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Sample records for sediment tephra record

  1. Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Schiff, C J; Kaufman, D S; Wallace, K L; Werner, A; Ku, T L; Brown, T A

    2007-02-25

    A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS {sup 14}C ages, along with the {sup 137}Cs and {sup 210}Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of sediment, and to determine the age of each tephra deposit. The age model is based on a cubic smooth spline function that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages {+-} 105 yr (1{sigma}). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7 per 500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of once every 130 yr.

  2. Geochemical fingerprints by activation analysis of tephra layers in Lake Van sediments, Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Landmann, Guenter [Technische Universitaet Darmstadt, Institut fuer Angewandte Geowissenschaften, Schnittspahnstr. 9, 64287 Darmstadt (Germany); Steinhauser, Georg; Sterba, Johannes H. [Vienna University of Technology, Atominstitut, Stadionallee 2, 1020 Vienna (Austria); Kempe, Stephan [Technische Universitaet Darmstadt, Institut fuer Angewandte Geowissenschaften, Schnittspahnstr. 9, 64287 Darmstadt (Germany); Bichler, Max, E-mail: bichler@ati.ac.a [Vienna University of Technology, Atominstitut, Stadionallee 2, 1020 Vienna (Austria)

    2011-07-15

    We discuss geochemical and sedimentological characteristics of 12 tephra layers, intercalated within the finely laminated sediments of Lake Van. Within the about 15 kyr long sediment record studied, volcanic activity concentrated in the periods 2.6-7.2 and 11.9-12.9 kyr B.P. Concentrations of 25 elements provide the geochemical fingerprint of each tephra layer and allow comparison to literature values of potential source volcanoes such as Mts. Nemrut and Suephan. The youngest two tephra layers (and probably also the other three ashes from the 2.6-7.2 kyr B.P. eruptions) originate from the Nemrut volcano. The source of the older tephra (11.9-12.9 kyr B.P.), however, remains unidentified.

  3. Automated statistical matching of multiple tephra records exemplified using five long maar sequences younger than 75 ka, Auckland, New Zealand

    Science.gov (United States)

    Green, Rebecca M.; Bebbington, Mark S.; Cronin, Shane J.; Jones, Geoff

    2014-09-01

    Detailed tephrochronologies are built to underpin probabilistic volcanic hazard forecasting, and to understand the dynamics and history of diverse geomorphic, climatic, soil-forming and environmental processes. Complicating factors include highly variable tephra distribution over time; difficulty in correlating tephras from site to site based on physical and chemical properties; and uncertain age determinations. Multiple sites permit construction of more accurate composite tephra records, but correctly merging individual site records by recognizing common events and site-specific gaps is complex. We present an automated procedure for matching tephra sequences between multiple deposition sites using stochastic local optimization techniques. If individual tephra age determinations are not significantly different between sites, they are matched and a more precise age is assigned. Known stratigraphy and mineralogical or geochemical compositions are used to constrain tephra matches. We apply this method to match tephra records from five long sediment cores (≤ 75 cal ka BP) in Auckland, New Zealand. Sediments at these sites preserve basaltic tephras from local eruptions of the Auckland Volcanic Field as well as distal rhyolitic and andesitic tephras from Okataina, Taupo, Egmont, Tongariro, and Tuhua (Mayor Island) volcanic centers. The new correlated record compiled is statistically more likely than previously published arrangements from this area.

  4. Late Miocene marine tephra beds : recorders of rhyolitic volcanism in North Island, New Zealand

    International Nuclear Information System (INIS)

    Shane, P.; Black, T.; Eggins, S.; Westgate, J.

    1998-01-01

    A deep-sea sequence of 72 rhyolitic tephra beds, now exposed at Mahia Peninsula in the Hawke's Bay region of the east coast, North Island, New Zealand, provides a record of Late Miocene volcanism of the Coromandel Volcanic Zone (CVZ): the precursor to large-scale explosive volcanism of the Quaternary Taupo Volcanic Zone (TVZ). The geochemical signature of the glasses in the Miocene tephra has been protected from hydrothermal alteration and prolonged subaerial exposure that have affected proximal CVZ deposits. The tephra beds are primarily eruption-driven sediment gravity flows that have been emplaced into a trench-slope basin, some 300 km from active volcanoes. Their occurrence is consistent with long-distance fluvial transport followed by a point-source discharge into the deep-sea environment, and has no implications for the paleogeographic location of the basins relative to the volcanic arc. The tephra beds are calc-alkaline rhyolites with SiO 2 contents in the range 72-78 wt% (recalculated on a volatile-free basis), and are broadly similar to glassy rocks of the CVZ. Their major oxide, trace element, and REE compositions are indistinguishable from glasses of TVZ rhyolites. The trace element and REE compositional variability in the Late Miocene tephra beds, which were erupted over an estimated duration of c. 0.5-2.4 m.y. is no greater than that of large silicic eruptives of the last 350 ka, and is suggestive of a long-lived source and/or similar magmatic processes. However, the individual tephra beds are products of discrete homogeneous magma batches. New fission track ages of the Miocene tephra beds suggest the main period of volcaniclastic deposition occurred in the interval c. 9-7 Ma. This corresponds well with the initiation of rhyolitic volcanism in the CVZ at c. 10 Ma, and a major period of caldera formation that took place to c. 7 Ma. The ages suggest a sediment accumulation rate of between 0.23 and 1.2 m/ka (av. 0.4 m/ka), and a frequency of eruption of

  5. Implications of S1 tephra findings in Dead Sea and Tayma palaeolake sediments for marine reservoir age estimation and palaeoclimate synchronisation

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    Neugebauer, Ina; Wulf, Sabine; Schwab, Markus J.; Serb, Johanna; Plessen, Birgit; Appelt, Oona; Brauer, Achim

    2017-08-01

    Here we report on the first findings of a cryptotephra in the Holocene lacustrine sediment records of the Dead Sea and Tayma palaeolake (NW Arabian Peninsula). The major element glass composition of this rhyolitic tephra is identical to the distal 'S1' tephra layer identified in the Yammoûneh palaeolake (Lebanon), in a marine sediment record from the SE Levantine basin and in the Sodmein Cave archaeological site in Egypt. The S1 tephra corresponds to the early Holocene 'Dikkartın' dome eruption of the Erciyes Dağ volcano in central Anatolia (Turkey) and has been dated in the marine record at 8830 ± 140 cal yr BP. We present new age estimates of the S1 tephra based on radiocarbon dating of terrestrial plant remains and pollen concentrates revealing ages of 8939 ± 83 cal yr BP in the Dead Sea sediments and 9041 ± 254 cal yr BP in Tayma. The precise date from the Dead Sea allows refining the early Holocene marine reservoir age in the SE Levantine Sea to ca. 320 ± 50 years. Synchronisation of marine and terrestrial palaeoclimate records in the eastern Mediterranean region using the S1 tephra further suggests a time-transgressive expansion of the early Holocene humid period.

  6. Correlation of Plio Pleistocene Tephra in Ethiopian and Kenyan rift basins: Temporal calibration of geological features and hominid fossil records

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    WoldeGabriel, Giday; Hart, William K.; Katoh, Shigehiro; Beyene, Yonas; Suwa, Gen

    2005-10-01

    The 200-m-thick fossiliferous Konso Formation and overlying terrace deposits, which crop out at the end of the southern sector of the Main Ethiopian Rift (MER), contain more than 30 distal tephra layers. Local and regional tephra correlations of more than 20 tephra units were established using major and trace element data of discrete and purified bulk glass samples within the Konso study area. Eleven correlative marker tuffs were recognized in stratigraphic sections of both the Konso Formation and the Omo-Turkana Basin sediments in southern Ethiopia and northern Kenya. The Turoha, Hope, Ivory, Bright White, and Boleshe Tuffs in the Konso Formation, and the Upper White Tuff in the overlying terrace deposits are securely correlated with the KBS, Akait, Lokapetamoi, Chari, Lower Nariokotome, and Silbo Tuffs of the Omo-Turkana Basin, using least mobile major elements (CaO, Fe 2O 3*, and TiO 2) and geochronology. Preliminary correlations are also suggested between the Konso Formation distal tephra and proximal units of the Quaternary caldera-forming silicic centers in the central sector of the MER. The strongly peralkaline tuffs of the Konso Formation are compositionally similar to proximal eruptions mostly located along the Quaternary axial rift zone of the southern, central, and northern sectors of the MER. The tephra correlation provides information about the temporal and spatial features of the volcanic and tectonic processes recorded in the evolving basins. Thickness and sedimentation rate were determined for both the Konso Formation and the Omo-Turkana Basin sections, measured between the Turoha (=KBS; 1.91 ± 0.03 Ma) and the Bright White (=Chari; 1.40 ± 0.02 Ma) Tuffs. Although the lithostratigraphic sequence at the Konso study area is younger, sedimentation rate within the Konso Formation was comparable to that of the Koobi Fora Formation, higher in the Nachukui Formation, and lower in the Shungura Formation. Local and regional differences in thickness and

  7. Spatial variation in pollen and charcoal records in relation to the 665 yr BP Kaharoa tephra at Harataonga Bay, Great Barrier Island, northern New Zealand : preliminary results

    International Nuclear Information System (INIS)

    Horrocks, M.; Nichol, S.L.; Jones, M.D.; Shane, P.A.; Sutton, D.G.

    2001-01-01

    We present preliminary results of a pollen study examining spatial variability using the 665 14 C yr BP Kaharoa tephra as the key stratigraphic marker. Our aim is to highlight potential differences in pollen and charcoal profiles from adjacent sites, and to point out the implications of these differences for the interpretation of pollen records. Three sediment cores were taken from swampy ground behind foredunes at Harataonga Bay, a small catchment on Great Barrier Island. Core 1 provides a c. 5000 14 C yr record of the swamp and is typical of northern New Zealand pollen profiles in that the deforestation signal appears immediately after Kaharoa tephra. Cores 2 and 3, however, show this signal at least 1 m below the tephra layer. Also, artefact pollen of gourd Lagenaria, an introduced Polynesian cultigen, was found 80 cm below the tephra layer in Core 2. This apparent difference in the timing of the human signal may be explained by the occurrence of small-scale, highly localised fires that are not recorded at adjacent sites. This has implications for inferring date of human presence in extensive areas, such as regions or large catchments, from a small number of pollen cores taken from within those areas. An alternative explanation is that sediments in cores 2 and 3 have been reworked to a much greater extent than those in Core 1. This has implications for the use of tephra as critical data for events, particularly when using recent tephra such as Kaharoa for dating human presence when the necessary resolution is to decades or centuries rather than millenia. (author). 18 refs., 6 figs., 2 tabs

  8. A volcanic event forecasting model for multiple tephra records, demonstrated on Mt. Taranaki, New Zealand

    Science.gov (United States)

    Damaschke, Magret; Cronin, Shane J.; Bebbington, Mark S.

    2018-01-01

    Robust time-varying volcanic hazard assessments are difficult to develop, because they depend upon having a complete and extensive eruptive activity record. Missing events in eruption records are endemic, due to poor preservation or erosion of tephra and other volcanic deposits. Even with many stratigraphic studies, underestimation or overestimation of eruption numbers is possible due to mis-matching tephras with similar chemical compositions or problematic age models. It is also common to have gaps in event coverage due to sedimentary records not being available in all directions from the volcano, especially downwind. Here, we examine the sensitivity of probabilistic hazard estimates using a suite of four new and two existing high-resolution tephra records located around Mt. Taranaki, New Zealand. Previous estimates were made using only single, or two correlated, tephra records. In this study, tephra data from six individual sites in lake and peat bogs covering an arc of 120° downwind of the volcano provided an excellent temporal high-resolution event record. The new data confirm a previously identified semi-regular pattern of variable eruption frequency at Mt. Taranaki. Eruption intervals exhibit a bimodal distribution, with eruptions being an average of 65 years apart, and in 2% of cases, centuries separate eruptions. The long intervals are less common than seen in earlier studies, but they have not disappeared with the inclusion of our comprehensive new dataset. Hence, the latest long interval of quiescence, since AD 1800, is unusual, but not out of character with the volcano. The new data also suggest that one of the tephra records (Lake Rotokare) used in earlier work had an old carbon effect on age determinations. This shifted ages of the affected tephras so that they were not correlated to other sites, leading to an artificially high eruption frequency in the previous combined record. New modelled time-varying frequency estimates suggest a 33

  9. Tephras in lacustrine sediments of the Sarliève marsh (French Massif Central): age and preservation

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    Fourmont, Agathe; Macaire, Jean-Jacques; Bréhéret, Jean-Gabriel; Argant, Jacqueline; Prat, Béatrice; Vernet, Gérard

    2006-12-01

    The Sarliève marsh sediments (Massif Central, France) contain two tephras. The first tephra [ 13.7±0.4ka(2δ), ca. 12 000 BP], regionally well known, enables to date the beginning of lacustrine infill to the Lateglacial. The second tephra, the 'tephra de Sarliève', the emitting volcano of which is unknown, would be dated to around the Early Subboreal from pollen data. This occurrence, after the discovery of the 'tephra de Beaunit', emphasizes that volcanic eruption(s) occurred in the 'Chaîne des Puys' or in the volcanic Cézallier more than 1000 years after the last known eruption (Pavin) in the 'Chaîne des Puys' at around 6.6/6.7 ka (5800/5900 BP). In the Sarliève piles, these tephras, well preserved in thick and more silicated deposits of deltas, were not observed in carbonated basin sediments where they were altered. The abundance of authigenic zeolites formed during the Lateglacial in restricted depocentre lacustrine waters allows us to detect initial CF1 tephra occurrence. To cite this article: A. Fourmont et al., C. R. Geoscience 338 (2006).

  10. Volcanic Cyclicities in the Pacific Northwest: Insights from the Marine Tephra Record from IODP Expedition 350, Izu Bonin Arc

    Science.gov (United States)

    Straub, S. M.; Schindlbeck, J. C.; Jegen, M. D.; Corry-Saavedra, K.; Murayama, M.; Woodhead, J. D.; Kutterolf, S.; Vautravers, M. J.; Wang, K. L.

    2016-12-01

    While the influences of orbital cycles on the ocean-atmosphere system are well documented, it remains largely unknown whether Earth's interior processes are similarly connected to orbital cycles. Recent studies of cyclic deposition in ash fallout from arc volcanism suggest that global climate changes in the form of variable glacial and water load are inversely related to magma production and/or volcanic eruption rate. However, a rigorous test of this hypotheses requires a temporally precise record of past volcanism which spans multiple glacial cycles at high resolution. The marine ash record of explosive volcanism provides such records readily. Here we undertake a detailed chemical study of discrete and disperse tephra deposits in cores from IODP Holes U1437B and U1436A drilled near the Izu Bonin arc in the northwestern Pacific. These locations combine a high background sedimentation rate (>10 m/Ma) of biogenic carbonate and Asian-derived dust with frequent emplacement of tephra fallout from the nearby Izu Bonin and Japan arcs. δ18O analyses record thirteen climatic cycles in the carbonate mud of the uppermost 120 m of Hole U1437B and eleven cycles in the uppermost 70 m of Hole U1436C. Strikingly, the distribution of 134 primary ash layers in Hole U1437B seems to be synchronous with glacial cycles, with a distinct increase in eruption occurrences at either the transitions of glacial/interglacial or at the early interglacials. This is confirmed by first results of a frequency analysis of the ash-time series that indicate a dominance of a 100 ka cycle. The question, which remains to be answered, is whether deglaciation drives volcanism or volcanism drives deglaciation? We also investigate the distribution of `dispersed ash' in this sequence, which is not visible to the naked eye but is volumetrically significant and thus also critical in testing time-cause relationships between arc volcanism and glacial cycles. Major questions we address are: 1) do we see the same

  11. Connecting the records: exploiting tephra deposits to help understand abrupt climate change

    Science.gov (United States)

    Davies, S. M.; Abbott, P. M.; Bourne, A. J.; Chapman, M.; Pearce, N. J. G.; Griggs, A. J.; Cook, E.

    2016-12-01

    The causal mechanism of abrupt climate change during the last glacial period remains a key challenge. Although these events are well-documented in a wide range of proxy records, the triggers and drivers remain poorly understood, largely due to the dating uncertainties that prevent the integration of different archives. Unravelling the lead/lag responses (hence cause and effect) between the Earth's climate components is limited by the challenges of synchronising palaeoclimate records on a common timescale. Here we present the potential and the challenges of optimising the use of cryptotephra deposits to precisely correlate the Greenland ice-cores with North Atlantic marine records. A series of new cryptotephra deposits have been identified in Greenland, increasing the scope of identifying coeval isochrons in the marine environment. This new framework, however, brings new challenges in the search for unique and robust geochemical fingerprints for unequivocal tephra correlations. As such, some tephra deposits are proposed to be more valuable than others and underpin key snapshots in time during the last glacial period. The North Atlantic Ash Zone II, for instance, represents the most widespread isochron and constrains the cooling of GI-15. Some tephra deposits in the ice-core record originate from ultra-distal sources beyond the North Atlantic region and we also explore the potential for establishing North Pacific linkages.

  12. Holocene vegetation, environment, and tephra recorded from Lake Pupuke, Auckland, New Zealand

    International Nuclear Information System (INIS)

    Horrocks, M.; Augustinus, P.; Deng, Y.; Shane, P.; Andersson, S.

    2005-01-01

    Lake Pupuke provides a near-complete, high-resolution environmental record of the Holocene from northern New Zealand. Tephra beds constrain the timing of a range of proxy indicators of environmental change, and demonstrate errors in a radiocarbon chronology. Agathis australis forest progressively increases from c. 7000 yr BP and, in conjunction with indicators of reduced biomass productivity, support a model of long-term climate change to drier conditions over the Holocene. However, except for Agathis, conifer-hardwood forest dominated mainly by Dacrydium cupressinum shows little change throughout the pre-human Holocene, suggesting environmental stability. Dramatic vegetation change occurred only within the last millennium as a result of large-scale Polynesian deforestation by fire. This happened a short time before the local eruption of c. 638 cal. yr BP Rangitoto Tephra. The identification of two eruptions of tephra from Rangitoto volcano has implications for future hazard planning in the Auckland region, because the volcanoes were previously considered single event centres. Changes in atmospheric circulation since the Late Glacial, possibly causing lower frequency of distal ashfall in Auckland during the Holocene, complicates the use of long-term records in hazard frequency assessment. (author). 39 refs., 7 figs., 2 tabs

  13. Exploring Links Between Global Climate and Explosive Arc Volcanism in Tephra-Rich Quaternary Sediments: A Pilot Study from IODP Expedition 350 Site 1437B, Izu Bonin Rear-Arc Region

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    Corry-Saavedra, K.; Straub, S. M.; Bolge, L.; Schindlbeck, J. C.; Kutterolf, S.; Woodhead, J. D.

    2015-12-01

    Fallout tephra in marine sediment provide an excellent archive of explosive arc volcanism that can be directly related to the other parameters of climate change, such as ice volume data, IRD (ice-rafted debris) input, etc. Current studies are based on 'discrete' tephra beds, which are produced by major eruptions and visible with the naked eye. Yet the more common, but less explosive arc eruptions that are more continuous through time produce 'disperse' tephra, which is concealed by the non-volcanic host sediment and invisible to the eye. The proportion of disperse tephra in marine sediments is known to be significant and may be critical in elucidating potential synchronicity between arc volcanism and glacial cycles. We conducted a pilot study in young sediments of IODP Hole 1437B drilled at 31°47.3911'N and 139°01.5788'E at the rear-arc of the Izu Bonin volcanic arc. By means of δ18O (Vautravers, in revision), eleven climatic cycles are recorded in uppermost 120 meter of carbonate mud that is interspersed by cm-thick tephra fallout layers. We selected six tephra layers, ranging from 0.2 to 1.16 million years in age, and sampled those vertically, starting from carbonate mud below the basal contact throughout the typical gradational top into the carbonate mud above. From each tephra bed, volcanic particles (>125 micrometer) were handpicked. All other samples were powdered and leached in buffered acetic acid and hydroxylamine hydrochloride to remove the carbonate and authigenous fraction, respectively. Major and trace element abundances (except for SiO2) from all samples were determined by ICP-MS and ICP-OES methods. Strong binary mixing trends are revealed between the pure tephra end member, and detrital sediment component. The tephra is derived from the Izu Bonin volcanic front and rear-arc, while the sediment component is presumably transported by ocean surface currents from the East China Sea. Our data show that mixing proportions change systematically with

  14. Diagenesis in tephra-rich sediments from the Lesser Antilles Volcanic Arc: Pore fluid constraints

    Science.gov (United States)

    Murray, Natalie A.; McManus, James; Palmer, Martin R.; Haley, Brian; Manners, Hayley

    2018-05-01

    expected given the high abundance of tephra in these sediments. Part of this carbonate buffering, at this site as well as throughout the region, derives from the fact that the Sr concentration in the non-carbonate fraction is generally low (<200 ppm), whereas the carbonate fraction has Sr concentrations approaching ∼1000 ppm.

  15. Multiple Magma Batches Recorded in Tephra Deposits from the Toba Complex, Sumatra.

    Science.gov (United States)

    Pearce, N. J. G.; Westgate, J.; Gatti, E.

    2015-12-01

    The Toba Caldera Complex is the largest Quaternary caldera on Earth, and has generated three voluminous and compositionally similar rhyolitic tuffs, viz. the Oldest (OTT, 800 ka), Middle (MTT, ~500 ka) and Youngest Toba Tuffs (YTT, 75 ka). These tephra deposits are widespread across Indonesia, Malaysia, South China Sea, Sea of Bengal, India and Indian Ocean and provide useful stratigraphic markers in oceanic, lacustrine and terrestrial environments. Single shard trace element analysis of these deposits reveals the changing availability of different batches of magma through time, with Sr, Ba and Y contents defining 5 discrete magma populations in YTT, 4 populations in MTT and only a single, low Ba population in OTT. Within an individual eruption these populations are clearly distinct, but between eruptions (e.g. MTT and YTT) some of these populations overlap while others do not, indicating both the longevity (and/or continuous supply of fresh material) and evolution of these magma batches in the Toba Complex. Major element compositions of the different groups show equilibration at different pressures (based on Q'-Ab'-Or'), with the equilibration of low Ba populations at ~160 MPa, increasing to depths of ~210 MPa for the highest Ba population. The proportions of different populations of glass in distal YTT shows that relatively little of the high Ba population makes it into the distal record across India, and that this population appears to be over-represented in the proximal free glass and pumice from the caldera walls. This data may shed light on magma availability and tephra dispersal during the YTT eruption. Similarly, the glass composition of individual pumices from proximal deposits record regional, compositional and temporal differences in the erupted products. These show, for example, the apparent mingling of some of the magma batches and also that the high Ba population appears early (i.e. stratigraphically lower) in the northern caldera wall.

  16. A new ELSA time series of tephra layers and paleobotanical evidence from laminated Eifel maar sediments covering the entire last 120,000 years

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    Sirocko, Frank; Knapp, Hannes; Klee, Marlies; Rothacker, Leo; Kromer, Bernd

    2014-05-01

    The ELSA Project has drilled a total of 50 sediment cores (2000 m of laminated lake sediment) from Eifel maar lakes and dry maar structures during the last 15 years. These records have been dated using 7 different methods, including 370 14C dates. Ten records reveal the established palynological succession of trees during the Holocene down to the Laacher See Tephra, which is used for synchronization with seven more recently drilled laminated sediment cores, which all are 14C-dated too and analyzed for tephra, pollen and paleobotanical macroremains. The seven newly established records reveal a continuous MIS2 section with mosses, ostracods and characea oogonia. They show that the 28.000 - 40.000 BP has witnessed an open landscape dominated by grass, but with rhythmic spread of conifer trees following the Greenland interstadial/succession. Seeds of Ranunculae provide excellent material for 14C dating. Even deciduous trees are present in small amounts until 28.000 BP. The time from 48.000 to 40.000 BP is characterized by a pronounced transition from the open landscape to an early MIS3 spruce (Picea) dominated forest during Greenland Interstadial GI17-14. Modern man apparently arrived at the end of this principal vegetation change near 40,000 BP. Volcanic activity in the Eifel had a stable and pronounced recurrence from 55,000 - 30,000 BP every 4000 years, but commenced with the beginning of MIS2. This landscape evolution with a forested early MIS3 is quite different to peat and sediment records from Netherlands/ Northern Germany/Scandinavia/ Poland, but is similar to conditions in parts of Switzerland. We address the early MIS3 forest to the nearby continuously moist soils and warm conditions in the nearby Mosel valley, i.e. on those stands where wine is growing today, and which most likely had served as a local refugia even for deciduous trees during MIS4 and MIS3. The MIS5 sections of the presented ELSA records reach down at least to the beginning of MIS5d near 118

  17. Acoustic and tephra records of explosive eruptions at West Mata submarine volcano, NE Lau Basin

    Science.gov (United States)

    Dziak, R. P.; Bohnenstiehl, D. R.; Baker, E. T.; Matsumoto, H.; Caplan-Auerbach, J.; Mack, C. J.; Embley, R. W.; Merle, S. G.; Walker, S. L.; Lau, T. A.

    2013-12-01

    West Mata is a 1200 m deep submarine volcano where explosive boninite eruptions were directly observed in May 2009. Here we present long-term acoustic and tephra records of West Mata explosion activity from three deployments of hydrophone and particle sensor moorings beginning on 8 January 2009. These records provide insights into the character of explosive magma degassing occurring at the volcano's summit vent until the decline and eventual cessation of the eruption during late 2010 and early 2011. The detailed acoustic records show three types of volcanic signals, 1) discrete explosions, 2) diffuse explosions, and 3) volcanic tremor. Discrete explosions are short duration, high amplitude broad-band signals caused by rapid gas bubble release. Diffuse signals are likely a result of 'trap-door' explosions where a quench cap of cooled lava forms over the magmatic vent but gas pressure builds underneath the cap. This pressure eventually causes the cap to breach and gas is explosively released until pressure reduces and the cap once again forms. Volcanic tremor is typified by narrow-band, long-duration signals with overtones, as well as narrow-band tones that vary frequency over time between 60-100 Hz. The harmonic tremor is thought to be caused by modulation of rapid, short duration gas explosion pulses and not a magma resonance phenomenon. The variable frequency tones may be caused by focused degassing or hydrothermal fluid flow from a narrow volcanic vent or conduit. High frequency (>30 Hz) tremor-like bands of energy are a result of interference caused by multipath wide-band signals, including sea-surface reflected acoustic phases, that arrive at the hydrophone with small time delays. Acoustic data suggest that eruption velocities for a single explosion range from 4-50 m s-1, although synchronous arrival of explosion signals has complicated our efforts to estimate long-term gas flux. Single explosions exhibit ~4-40 m3 s-1 of total volume flux (gas and rock) but

  18. A quantitative X-ray diffraction inventory of the tephra and volcanic glass inputs into the Holocene marine sediment archives off Iceland: A contribution to V.A.S.T.

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    Andrews, John T.; Kristjansdottir, Greta B.; Eberl, Dennis D.; Jennings, Anne E.

    2013-01-01

    This paper re-evaluates how well quantitative x-ray diffraction (qXRD) can be used as an exploratory method of the weight percentage (wt%) of volcaniclastic sediment, and to identify tephra events in marine cores. In the widely used RockJock v6 software programme, qXRD tephra and glass standards include the rhyodacite White River tephra (Alaska), a rhyolitic tephra (Hekla-4) and the basaltic Saksunarvatn tephra. Experiments of adding known wt% of tephra to felsic bedrock samples indicated that additions ≥10 wt% are accurately detected, but reliable estimates of lesser amounts are masked by amorphous material produced by milling. Volcaniclastic inputs range between 20 and 50 wt%. Primary tephra events are identified as peaks in residual qXRD glass wt% from fourth-order polynomial fits. In cores where tephras have been identified by shard counts in the > 150 µm fraction, there is a positive correlation (validation) with peaks in the wt% glass estimated by qXRD. Geochemistry of tephra shards confirms the presence of several Hekla-sourced tephras in cores B997-317PC1 and -319PC2 on the northern Iceland shelf. In core B997-338 (north-west Iceland), there are two rhyolitic tephras separated by ca. 100 cm with uncorrected radiocarbon dates on articulated shells of around 13 000 yr B.P. These tephras may be correlatives of the Borrobol and Penifiler tephras found in Scotland. The number of Holocene tephra events per 1000 yr was estimated from qXRD on 16 cores and showed a bimodal distribution with an increased number of events in both the late and early Holocene.

  19. Holocene eruption history in Iceland - Eruption frequency vs. Tephra layer frequency

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    Oladottir, B. A.; Larsen, G.

    2012-12-01

    Volcanic deposits of all kinds are used to reconstruct eruption history of volcanoes and volcanic zones. In Iceland tephra is the ideal volcanic deposit to study eruption history as two out of every three eruptions taking place there during the last 11 centuries have been explosive, leaving tephra as their only product. If eruptions producing both lava and tephra are included three out of every four eruptions have produced tephra. Tephra dispersal and deposition depends on factors such as eruption magnitude, eruption cloud height, duration of eruption and prevailing wind directions at the time of eruption. Several outcrops around a particular volcano must therefore be measured to obtain optimal information of its eruption history. Vegetation in the area of deposition is also of great importance for its preservation. Tephra deposited on un-vegetated land is rapidly eroded by wind and water, and deposits up to few tens of cm thickness may be lost from the record. Such tephra deposited on grassy or forested land is at least partly sheltered from the wind after deposition. Soon after tephra deposition (how soon depends on tephra thickness) the root system of the vegetation creates an even better shelter for the tephra and when this stage is reached the tephra is preserved in the soil for millennia, given that no soil erosion takes place. Vegetation is often boosted in the first years after tephra deposition which in turn helps tephra preservation. A setback of using soil sections for reconstructing Holocene eruption history is the lack of soil at the beginning of the era but for that time period tephra records in lake and marine sediments can be used. When tephra stratigraphy in soil sections is measured to study eruption history and eruption frequency of a volcano it must be kept in mind that what is seen is in fact the tephra layer frequency. One section only shows tephra layers deposited in that location and more importantly only the layers preserved there. The

  20. Stratigraphy, age and correlation of middle Pleistocene silicic tephras in the Auckland region, New Zealand : a prolific distal record of Taupo Volcanic Zone volcanism

    International Nuclear Information System (INIS)

    Alloway, B.V.; Westgate, J.; Pillans, B.; Pearce, N.; Newnham, R.; Byrami, M.; Aarburg, S.

    2004-01-01

    at Glenbrook Beach. The occurrence of Ongatiti Ignimbrite in Auckland significantly extends its northward distribution. Large numbers of post- and pre-Ongatiti rhyolitic tephra layers, ranging in age from c. 1.31 to 0.53 Ma, are also recognised in the region, with some up to 0.5 m in compacted fallout thickness. Although some tephras can be attributed to known TVZ eruptions (e.g., Ahuroa/Unit D), many have yet to be identified in proximal source areas and remain uncorrelated. However, some can be reliably correlated to tephra layers occurring in marine to nearshore sequences of Wanganui Basin and deep-sea cores retrieved east of North Island. The identification of previously unrecognised mid-Pleistocene TVZ-sourced tephra deposits in the Auckland region, and their correlation to the offshore marine record, represent an advance in the construction of a higher resolution history for the TVZ where, close to eruptive source, the record is fragmentary and obscured by deep burial, or erosion, or both. (author). 65 refs., 22 figs., 3 tabs

  1. Tephra Sedimentation from a Short-term Wind-affected Volcanic Plume of the 8 October 2016 Aso Nakadake Eruption, Japan

    Science.gov (United States)

    Tsuji, T.; Nishizaka, N.; Onishi, K.

    2017-12-01

    Sedimentation processes during explosive volcanic eruptions can be constrained based on detailed analysis of grain-size variation of tephra deposits. Especially, an accurate description of the amount of fine particles has also significant implications for the assessment of specific tephra hazards. Grain size studies for single short-term eruption has advantage to contribute understanding the sedimentation processes because it is simple compared to long-lasting eruption. The 2016 Aso Nakadake eruption, Japan represents an ideal for the study of short-term eruptions thanks to an accurate investigation. Then, we investigate the grain size variation with distance from the vent and sedimentological features of the deposit to discuss the sedimentation processes of the tephra fragments. The eruption provided pyroclastic flow deposit and fallout tephra which distributed NE to ENE direction from the vent. The deposits between 4 and 20 km from vent consist of fine-coated lapilli to coarse ash, ash pellet and mud droplet in ascending degree. The samples are lapilli-bearing within 20 km from vent and those outside of 20 km mainly consist of ash particles. Detailed analyses of individual samples highlight a rapid decay of maximum and mean grain size for the deposit from proximal to distal. The decay trend of maximum grain-size is approximated by three segments of exponential curves with two breaks-in-slope at 10 and 40 km from vent. Most of the sampled deposits are characterized by bimodal grain-size distributions, with the modes of the coarse subpopulation decreasing with distance from vent and those of the fine subpopulation being mostly stable. The fine subpopulation has been interpreted as being mostly associated with size-selective sedimentation processes (e.g., particle aggregation) confirmed by the existence of fine-coated particles, ash pellet and mud droplet. As the fine-coated particles generally have a higher terminal velocity than the individual constituent

  2. Eruptive and environmental processes recorded by diatoms in volcanically-dispersed lake sediments from the Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Harper, Margaret A.; Pledger, Shirley A.; Smith, Euan G. C.; Van Eaton, Alexa; Wilson, Colin J. N.

    2015-01-01

    Late Pleistocene diatomaceous sediment was widely dispersed along with volcanic ash (tephra) across and beyond New Zealand by the 25.4 ka Oruanui supereruption from Taupo volcano. We present a detailed analysis of the diatom populations in the Oruanui tephra and the newly discovered floras in two other eruptions from the same volcano: the 28.6 ka Okaia and 1.8 ka Taupo eruptions. For comparison, the diatoms were also examined in Late Pleistocene and Holocene lake sediments from the Taupo Volcanic Zone (TVZ). Our study demonstrates how these microfossils provide insights into the lake history of the TVZ since the Last Glacial Maximum. Morphometric analysis of Aulacoseira valve dimensions provides a useful quantitative tool to distinguish environmental and eruptive processes within and between individual tephras. The Oruanui and Okaia diatom species and valve dimensions are highly consistent with a shared volcanic source, paleolake and eruption style (involving large-scale magma-water interaction). They are distinct from lacustrine sediments sourced elsewhere in the TVZ. Correspondence analysis shows that small, intact samples of erupted lake sediment (i.e., lithic clasts in ignimbrite) contain heterogeneous diatom populations, reflecting local variability in species composition of the paleolake and its shallowly-buried sediments. Our analysis also shows a dramatic post-Oruanui supereruption decline in Cyclostephanos novaezelandiae, which likely reflects a combination of (1) reorganisation of the watershed in the aftermath of the eruption, and (2) overall climate warming following the Last Glacial Maximum. This decline is reflected in substantially lower proportions of C. novaezelandiae in the 1.8 ka Taupo eruption deposits, and even fewer in post-1.8 ka sediments from modern (Holocene) Lake Taupo. Our analysis highlights how the excellent preservation of siliceous microfossils in volcanic tephra may fingerprint the volcanic source region and retain a valuable record

  3. The eruption history of the quaternary Eifel volcanic fields: Implications from the ELSA - Tephra - Stack

    Science.gov (United States)

    Förster, Michael; Sirocko, Frank

    2015-04-01

    Numerous tephra layers occur in maar sediments in the quaternary Eifel volcanic fields. The sediments were systematically drilled and cored since 1998 by the Eifel Laminated Sediment Archive project (ELSA) (Sirocko et al. 2013). These maar sediments are laminated and the tephra is easily recognizeable by a coarser grain size. Additionaly, tephra layers appear dark grey to black in color. The ashes were sieved to a fraction of 250 - 100 µm and sorted into grains of: reddish and greyish sandstone, quartz, amphibole, pyroxene, scoria and pumice, sanidine, leucite and biotite. A minimum of 100 grains for each tephra layer were used for a sediment petrographic tephra characterisation (SPTC). The grain counts resemble the vol. -% of each grain species. Three types of tephra could be identified by their distinctive grain pattern: (1) phreatomagmatic tephra, rich in basement rocks like greyish/reddish sandstone and quartz. (2) Strombolian tephra, rich in scoria and mafic minerals like pyroxene. (3) evolved tephra, rich in sanidine and pumice. 16 drill-cores, covering the last 500 000 years have been examined. Younger cores were dated by 14C ages and older cores by optical stimulated luminescence. Independently from this datings, the drill-cores were cross-correlated by pollen and the occurences of specific marker-tephra layers, comprising characteristic grain-types. These marker-tephra layers are especially thick and of evolved composition with a significant abundance of sanidine and pumice. The most prominent tephra layers of this type are the Laacher See tephra, dated to 12 900 b2k by Zolitschka (1998), the 40Ar/39Ar dated tephra layers of Dümpelmaar, Glees and Hüttenberg, dated to 116 000 b2k, 151 000 b2k and 215 000 b2k by van den Bogaard & Schmincke (1990), van den Bogaard et al. (1989). These datings set the time-frame for the eruption-phases of the quaternary Eifel Volcanic Fields. Our study refines these findings and shows that phases of activity are very

  4. Quaternary magnetic excursions recorded in marine sediments.

    Science.gov (United States)

    Channell, J. E. T.

    2017-12-01

    This year is the golden (50th) anniversary of the first documentation of a magnetic excursion, the Laschamp excursion in volcanics from the Chaine des Puys (Bonhommet and Babkine, 1967). The first recording of an excursion in sediments was from the Blake Outer Ridge (Smith and Foster, 1969). Magnetic excursions are directional aberrations of the geomagnetic field apparently involving short-lived reversal of the main dipole field. They have durations of a few kyrs, and are therefore rarely recorded in sediments with mean sedimentation rates Palma), and 670 ka (Osaka Bay), implying at least 11 excursions in the Brunhes Chron. For the Matuyama Chron, excursions have been recorded in marine sediments at 868 ka (Kamikatsura?), 932 ka (Santa Rosa), 1051 ka (Intra-Jaramillo), 1115 ka (Punaruu), 1255 ka (Bjorn), 1476 ka (Gardar), 1580 ka (Gilsa), and 2737 ka (Porcupine). Excursions coincide with minima in relative paleointensity (RPI) records. Ages are from correlation of excursion records to oxygen isotope records in the same cores, and ice-volume calibration of the oxygen isotope template. The marine sediment record of excursions, combined with independent documentation of excursions in lavas with Ar/Ar age control, is progressively strengthening our knowledge of the excursion inventory in the Quaternary, and enhancing the importance of excursions and RPI in Quaternary stratigraphy.

  5. Lake sediment records of Quaternary climate change

    International Nuclear Information System (INIS)

    Moy, C.

    2012-01-01

    Lake sediment records provide an excellent means to reconstruct past climate and environmental change because they typically provide long, high-resolution and continuous archives of environmental change. Lake sediment records typically exhibit high sedimentation rates (centennial to millennial scale variability is common and annual resolution is possible in some sites), contain sedimentary components well-suited for a multi-proxy approach, multiple dating methods can be applied, tend to exhibit a broad geographic distribution, and are relatively accessible. Furthermore, a number of geochemical techniques can be applied to reconstruct components of the climate system based on the stable isotope geochemistry of carbonate or organic phases preserved and exposed in lacustrine sediment cores. Various stable isotope methods can be applied to lacustrine systems and these are a valuable tool that can be used to monitor physical processes (e.g. evaporation), vegetation dynamics within the watershed (C 3 vs C 4 plant distributions), biologic processes (aquatic productivity), all of which can be driven by a regional climate forcing. (author). 31 refs., 11 figs., 1 tab.

  6. Total grain-size distribution of four subplinian-Plinian tephras from Hekla volcano, Iceland: Implications for sedimentation dynamics and eruption source parameters

    Science.gov (United States)

    Janebo, Maria H.; Houghton, Bruce F.; Thordarson, Thorvaldur; Bonadonna, Costanza; Carey, Rebecca J.

    2018-05-01

    The size distribution of the population of particles injected into the atmosphere during a volcanic explosive eruption, i.e., the total grain-size distribution (TGSD), can provide important insights into fragmentation efficiency and is a fundamental source parameter for models of tephra dispersal and sedimentation. Recent volcanic crisis (e.g. Eyjafjallajökull 2010, Iceland and Córdon Caulle 2011, Chile) and the ensuing economic losses, highlighted the need for a better constraint of eruption source parameters to be used in real-time forecasting of ash dispersal (e.g., mass eruption rate, plume height, particle features), with a special focus on the scarcity of published TGSD in the scientific literature. Here we present TGSD data associated with Hekla volcano, which has been very active in the last few thousands of years and is located on critical aviation routes. In particular, we have reconstructed the TGSD of the initial subplinian-Plinian phases of four historical eruptions, covering a range of magma composition (andesite to rhyolite), eruption intensity (VEI 4 to 5), and erupted volume (0.2 to 1 km3). All four eruptions have bimodal TGSDs with mass fraction of fine ash (primary fragmentation. Due to differences in plume height, this contrast is not seen in samples from individual sites, especially in the near field, where lapilli have a wider spatial coverage in the Plinian deposits. The distribution of pyroclast sizes in Plinian versus subplinian falls reflects competing influences of more efficient fragmentation (e.g., producing larger amounts of fine ash) versus more efficient particle transport related to higher and more vigorous plumes, displacing relatively coarse lapilli farther down the dispersal axis.

  7. Occurrence of tephra/volcanic tuff in the tertiary sediments of Himachal Himalaya from Tileli area, Mandi district, H.P.: implication for stratigraphy and uranium mineralization

    International Nuclear Information System (INIS)

    Pandey, Pradeep; Chabbra, Jyotsana; Joshi, G.B.; Parihar, P.S.

    2014-01-01

    Presence of Early Tertiary pyroclastic material (tephra) has been documented petrographically, for the first time, in the Mandi-Bilaspur Sector from Tileli area, Dharamsala basin of Himachal Pradesh. The tephra is reported from the red shale, identified as tuffaceous siltstone belonging to lower Dharamsala Formation that lies above the uraniferous sandstone body and occurs as thin layers of over 300m along the strike, close to the contact of lower and upper Dharamsala formations. The tuffaceous material shows crude but preferred orientation of minerals like biotite, muscovite, chlorite, clay, hematite and specularite. Various features indicating presence of tephra are, glass shards altered to clay but retaining 'U' shaped outline, spindle-shaped hematite with preferred orientation, spherical to sub-spherical clay and altered Fe oxide rich balls, clay groundmass with flow pattern, flaky minerals in association with clast depicting asymmetrical ramp structure. A zone of approximately 300 m length containing tuffaceous material has been established at Tileli overlying the uraniferous sandstone body. Identification of tephra at Tileli has significant implications as it enabled in demarcating the boundary between the upper and lower Dharamsala formations in central part of the basin in Bilaspur-Mandi Sector of HP Himalaya and also in guiding the uranium exploration programme in the lower Dharamsala Formation. (author)

  8. Sedimentology, tephrostratigraphy, and chronology of the DEEP site sediment record, Lake Ohrid (Albania, FYROM)

    Science.gov (United States)

    Leicher, Niklas; Wagner, Bernd; Francke, Alexander; Just, Janna; Zanchetta, Giovanni; Sulpizio, Roberto; Giaccio, Biagio; Nomade, Sebastien

    2017-04-01

    Lake Ohrid, located on the Balkan Peninsula, is one of the very few lakes in the world that provides a continuous and high-resolution record of environmental change of >1.3 Ma. The sedimentary archive was drilled in spring 2013 within the scope of the International Continental Scientific Drilling Program (ICDP) and the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project in order to investigate local and regional geological and paleoclimatic processes, as well as triggers of evolutionary patterns and endemic biodiversity. The continuous composite profile (584 m) of the main drill site DEEP was logged (XRF, MSCL) and subsampled for biogeochemical (TIC, TOC, TN, TS) and sedimentological (grain size) analyses. The lithology of the DEEP site indicates that the history of Lake Ohrid can roughly be separated into two parts, with the older section between 584 and 450 m depth being characterised by a sedimentary facies indicating shallow water conditions, which is likely younger than ca. 1.9 Ma. In the lowermost few meters of the succession gravels and pebbles hampered a deeper drilling penetration and indicate that fluvial conditions existed during the onset of lake formation. Together with geotectonic, seismic, and biological information, the data imply that the Ohrid basin formed by transtension during the Miocene, opened during the Pliocene and Pleistocene, and that the lake established between 1.9 and 1.3 Ma ago. The sediments of the younger part (DEEP site sequence and are subject of ongoing investigations aimed at identifying their specific volcanic sources and equivalent known tephra by using geochemical fingerprinting of glass fragments. This was already successfully approved for tephra horizons in the upper 247.8 m of the sequence, obtaining important chronological information from 11 well dated tephra layers. These tephrochronological constraints were complemented by ages obtained from tuning the consistent pattern of the

  9. The ELSA tephra stack: Volcanic activity in the Eifel during the last 500,000 years

    Science.gov (United States)

    Förster, Michael W.; Sirocko, Frank

    2016-07-01

    Tephra layers of individual volcanic eruptions are traced in several cores from Eifel maar lakes, drilled between 1998 and 2014 by the Eifel Laminated Sediment Archive (ELSA). All sediment cores are dated by 14C and tuned to the Greenland interstadial succession. Tephra layers were characterized by the petrographic composition of basement rock fragments, glass shards and characteristic volcanic minerals. 10 marker tephra, including the well-established Laacher See Tephra and Dümpelmaar Tephra can be identified in the cores spanning the last glacial cycle. Older cores down to the beginning of the Elsterian, show numerous tephra sourced from Strombolian and phreatomagmatic eruptions, including the 40Ar/39Ar dated differentiated tephra from Glees and Hüttenberg. In total, at least 91 individual tephra can be identified since the onset of the Eifel volcanic activity at about 500,000 b2k, which marks the end of the ELSA tephra stack with 35 Strombolian, 48 phreatomagmatic and 8 tephra layers of evolved magma composition. Many eruptions cluster near timings of the global climate transitions at 140,000, 110,000 and 60,000 b2k. In total, the eruptions show a pattern, which resembles timing of phases of global sea level and continental ice sheet changes, indicating a relation between endogenic and exogenic processes.

  10. Tephra, tephrochronology and archaeology

    DEFF Research Database (Denmark)

    Riede, Felix; Thastrup, Mads

    2013-01-01

    increased areas, the overall potential of tephrochronology as a major dating tool for both palaeoenvironmental scientists and archaeologists is greatly expanded. The aim of this paper is not to be comprehensive, but to provide a brief and timely general review of tephra studies and their methodologies......Volcanic eruptions are often, although by no means always, associated with a profuse output of fine pyroclastic material, tephra. While residence time in the atmosphere of the very finest of these particles can be substantial, the deposition of the bulk of volcanic ejecta can be considered...... only act as a useful chronostratigraphic marker, but can also play a role in changing patterns of environmental and cultural change at the level of the site or the region. In order to move towards such integration, a series of methodological challenges have to be met. We outline some of these...

  11. A detailed paleomagnetic and rock-magnetic investigation of the Matuyama-Bruhnes geomagnetic reversal recorded in tephra-paleosol sequence of Tlaxcala(Central Mexico

    Directory of Open Access Journals (Sweden)

    Ana Maria Soler-Arechalde

    2015-04-01

    Full Text Available Geomagnetic reversals are global phenomena, for about 50 years the paleomagnetists attempted to acquire as many detailed records as possible using the magnetic memory of sediments and lava flows. Yet, transitional field behavior remains poorly characterized largely because of sporadic aspect of volcanic eruptions. In some specific cases, paleosols such as those developed from alluvial or aeolian sediments, may also record the variations of the Geomagnetic Field across the polarity changes. Here, we report a detailed paleomagnetic and rock-magnetic investigation on some radiometrically dated chromic luvisols located in Central Mexico carrying detrital or chemical remanent magnetization. The research was developed in order i to demonstrate the primary origin of the magnetic remanence and ii to show that paleosoils are good candidates to provide a high resolution record of the behavior of geomagnetic field during reversals. The lower part of the paleosoil sequence shows a clearly defined reverse polarity magnetization followed by geomagnetically unstable transitional field and ended by normal polarity remanence. Our AMS and rock magnetic data suggest that magnetization is acquired during the initial stage of soil formation in context of active volcanic activity since magnetic fabric is essentially sedimentary and reverse and normal polarity paleodirections are almost antipodal. Titanomagnetites are identified as main magnetic carriers of rock-magnetic measurements including thermomagnetics and hysteresis cycles. We propose that the transition recorded in this study correspond to the B-M boundary, considering the K-Ar datings available at the sequence bottom and that the chromic luvisols are potentially good recorders of the paleosecular variation. The identification of the B-M boundary within the studied sequence has fundamental significance for improving the chronological scale of Tlaxcala paleosol-sedimentary sequence and its correlation with the

  12. Lake sediment records of Quaternary climate change

    International Nuclear Information System (INIS)

    Moy, C.

    2013-01-01

    Lake sediments are excellent archives of climate and environmental change. Lakes typically exhibit high sedimentation rates, contain sedimentary components well-suited for a multi-proxy approach, multiple dating methods can be applied, exhibit a broad geographic distribution, and are relatively accessible for study. Furthermore, a number of geochemical techniques can be applied to recontsruct components of the climate system based on the stable isotope geochemistry of carbonate or organic phases preserved and exposed in lacustrine sedimentary cores. Various stable isotope methods can be applied to lacustrine systems and these are a valuable tool that can be used to monitor physical processes (e.g. evaporation), vegetation dynamics within the watershed (C 3 vs C 4 plant distributions), biologic processes (aquatic productivity), all of which can be driven by a regional climate forcing. (author). 31 refs., 11 figs.

  13. Lake sediment records of Quaternary climate change

    International Nuclear Information System (INIS)

    Moy, C.

    2016-01-01

    Lake sediments are excellent archives of climate and environmental change. Lakes typically exhibit high sedimentation rates, contain sedimentary components well-suited for a multi-proxy approach, multiple dating methods can be applied, exhibit a broad geographic distribution, and are relatively accessible for study. Furthermore, a number of geochemical techniques can be applied to recontsruct components of the climate system based on the stable isotope geochemistry of carbonate or organic phases preserved and exposed in lacustrine sedimentary cores. Various stable isotope methods can be applied to lacustrine systems and these are a valuable tool that can be used to monitor physical processes (e.g. evaporation), vegetation dynamics within the watershed (C 3 vs C 4 plant distributions), biologic processes (aquatic productivity), all of which can be driven by a regional climate forcing. (author).

  14. Lake sediment records of Quaternary climate change

    International Nuclear Information System (INIS)

    Moy, C.

    2014-01-01

    Lake sediments are excellent archives of climate and environmental change. Lakes typically exhibit high sedimentation rates, contain sedimentary components well-suited for a multi-proxy approach, multiple dating methods can be applied, exhibit a broad geographic distribution, and are relatively accessible for study. Furthermore, a number of geochemical techniques can be applied to recontsruct components of the climate system based on the stable isotope geochemistry of carbonate or organic phases preserved and exposed in lacustrine sedimentary cores. Various stable isotope methods can be applied to lacustrine systems and these are a valuable tool that can be used to monitor physical processes (e.g. evaporation), vegetation dynamics within the watershed (C 3 vs C 4 plant distributions), biologic processes (aquatic productivity), all of which can be driven by a regional climate forcing. (author)

  15. Lake sediment records of Quaternary climate change

    International Nuclear Information System (INIS)

    Moy, C.

    2015-01-01

    Lake sediments are excellent archives of climate and environmental change. Lakes typically exhibit high sedimentation rates, contain sedimentary components well-suited for a multi-proxy approach, multiple dating methods can be applied, exhibit a broad geographic distribution, and are relatively accessible for study. Furthermore, a number of geochemical techniques can be applied to recontsruct components of the climate system based on the stable isotope geochemistry of carbonate or organic phases preserved and exposed in lacustrine sedimentary cores. Various stable isotope methods can be applied to lacustrine systems and these are a valuable tool that can be used to monitor physical processes (e.g. evaporation), vegetation dynamics within the watershed (C 3 vs C 4 plant distributions), biologic processes (aquatic productivity), all of which can be driven by a regional climate forcing. (author)

  16. Ages of 24 widespread tephras erupted since 30,000 years ago in New Zealand, with re-evaluation of the timing and palaeoclimatic implications of the Lateglacial cool episode recorded at Kaipo bog

    Science.gov (United States)

    Lowe, David J.; Blaauw, Maarten; Hogg, Alan G.; Newnham, Rewi M.

    2013-08-01

    Tephras are important for the NZ-INTIMATE project because they link all three records comprising the composite inter-regional stratotype developed for the New Zealand climate event stratigraphy (NZ-CES). Here we firstly report new calendar ages for 24 widespread marker tephras erupted since 30,000 calendar (cal.) years ago in New Zealand to help facilitate their use as chronostratigraphic dating tools for the NZ-CES and for other palaeoenvironmental and geological applications. The selected tephras comprise 12 rhyolitic tephras from Taupo, nine rhyolitic tephras from Okataina, one peralkaline rhyolitic tephra from Tuhua, and one andesitic tephra each from Tongariro and Egmont/Taranaki volcanic centres. Age models for the tephras were obtained using three methods: (i) 14C-based wiggle-match dating of wood from trees killed by volcanic eruptions (these dates published previously); (ii) flexible depositional modelling of a high-resolution 14C-dated age-depth sequence at Kaipo bog using two Bayesian-based modelling programs, Bacon and OxCal's P_Sequence function, and the IntCal09 data set (with SH offset correction -44 ± 17 yr); and (iii) calibration of 14C ages using OxCal's Tau_Boundary function and the SHCal04 and IntCal09 data sets. Our preferred dates or calibrated ages for the 24 tephras are as follows (youngest to oldest, all mid-point or mean ages of 95% probability ranges): Kaharoa AD 1314 ± 12; Taupo (Unit Y) AD 232 ± 10; Mapara (Unit X) 2059 ± 118 cal. yr BP; Whakaipo (Unit V) 2800 ± 60 cal. yr BP; Waimihia (Unit S) 3401 ± 108 cal. yr BP; Stent (Unit Q) 4322 ± 112 cal. yr BP; Unit K 5111 ± 210 cal. yr BP; Whakatane 5526 ± 145 cal. yr BP; Tuhua 6577 ± 547 cal. yr BP; Mamaku 7940 ± 257 cal. yr BP; Rotoma 9423 ± 120 cal. yr BP; Opepe (Unit E) 9991 ± 160 cal. yr BP; Poronui (Unit C) 11,170 ± 115 cal. yr BP; Karapiti (Unit B) 11,460 ± 172 cal. yr BP; Okupata 11,767 ± 192 cal. yr BP; Konini (bed b) 11,880 ± 183 cal. yr BP; Waiohau 14,009 ± 155

  17. Microbially assisted recording of the Earth's magnetic field in sediment.

    Science.gov (United States)

    Zhao, Xiangyu; Egli, Ramon; Gilder, Stuart A; Müller, Sebastian

    2016-02-11

    Sediments continuously record variations of the Earth's magnetic field and thus provide an important archive for studying the geodynamo. The recording process occurs as magnetic grains partially align with the geomagnetic field during and after sediment deposition, generating a depositional remanent magnetization (DRM) or post-DRM (PDRM). (P)DRM acquisition mechanisms have been investigated for over 50 years, yet many aspects remain unclear. A key issue concerns the controversial role of bioturbation, that is, the mechanical disturbance of sediment by benthic organisms, during PDRM acquisition. A recent theory on bioturbation-driven PDRM appears to solve many inconsistencies between laboratory experiments and palaeomagnetic records, yet it lacks experimental proof. Here we fill this gap by documenting the important role of bioturbation-induced rotational diffusion for (P)DRM acquisition, including the control exerted on the recorded inclination and intensity, as determined by the equilibrium between aligning and perturbing torques acting on magnetic particles.

  18. Estuarine abandoned channel sedimentation rates record peak fluvial discharge magnitudes

    Science.gov (United States)

    Gray, A. B.; Pasternack, G. B.; Watson, E. B.

    2018-04-01

    Fluvial sediment deposits can provide useful records of integrated watershed expressions including flood event magnitudes. However, floodplain and estuarine sediment deposits evolve through the interaction of watershed/marine sediment supply and transport characteristics with the local depositional environment. Thus extraction of watershed scale signals depends upon accounting for local scale effects on sediment deposition rates and character. This study presents an examination of the balance of fluvial sediment dynamics and local scale hydro-geomorphic controls on alluviation of an abandoned channel in the Salinas River Lagoon, CA. A set of three sediment cores contained discrete flood deposits that corresponded to the largest flood events over the period of accretion from 1969 to 2007. Sedimentation rates scaled with peak flood discharge and event scale sediment flux, but were not influenced by longer scale hydro-meteorological activities such as annual precipitation and water yield. Furthermore, the particle size distributions of flood deposits showed no relationship to event magnitudes. Both the responsiveness of sedimentation and unresponsiveness of particle size distributions to hydro-sedimentological event magnitudes appear to be controlled by aspects of local geomorphology that influence the connectivity of the abandoned channel to the Salinas River mainstem. Well-developed upstream plug bar formation precluded the entrainment of coarser bedload into the abandoned channel, while Salinas River mouth conditions (open/closed) in conjunction with tidal and storm surge conditions may play a role in influencing the delivery of coarser suspended load fractions. Channel adjacent sediment deposition can be valuable records of hydro-meteorological and sedimentological regimes, but local depositional settings may dominate the character of short term (interdecadal) signatures.

  19. Tephrostratigraphy of the late Quaternary record from Lake Chalco, central México

    Science.gov (United States)

    Ortega-Guerrero, Beatriz; Caballero García, Lizeth; Linares-López, Carlos

    2018-01-01

    Lacustrine sequences in active volcanic settings preserve the record of fall-out products (tephras) from explosive volcanic activity from both proximal and distal sources. Sediments of Lake Chalco, located in the western part of the Trans Mexican Volcanic Belt, offer the opportunity to develop a detailed tephrostratigraphy of proximal and distal sources, and to provide stratigraphic marker horizons for the correlation of paleoclimate records. Here, we present major oxide glass and pumice data from 18 tephra layers interbedded in the lacustrine sediments of Chalco, from 11.5 to 31.3 cal ka BP. Tephra glass compositions range from basaltic trachyandesitic to rhyolitic. Two tephras were successfully correlated with the Tutti Frutti Plinian Eruption of Popocatépetl volcano; and two tephra layers from the Nevado de Toluca Plinian activity: the Upper Toluca Pumice and the Lower Toluca Pumice. Although the source of most of the tephras analyzed is unknown, their geochemical characterization, coupled with a robust chronology, contributes to establish a detailed tephrostratigraphy for the region. This tephra record also contributes to improving the estimated frequency of explosive volcanic activity for future hazards in the Basin of México and surrounding areas, where more than 29 million people live. Our findings estimate a recurrence interval of volcanic activity of ca. 1100 years in the interval between ca. 32 and 11.5 cal ka BP, shorter than previously estimated.

  20. Holocene tephra deposits in the northern Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The mineralogical and geochemical characteristics of sediments of Core CSH1, which was collected from the northern Okinawa Trough, indicate that large amounts of volcanic materials have deposited in the northern Okinawa Trough during the Holocene. On the basis of down-core variations in mineral and element contents of sediments, two layers in the uppermost section of Core CSH1 characterized by high quartz, Na2O, MnO, K2O, uranium contents and low contents of clay minerals, volatiles, Fe2O3, MgO, CaO and strontium, have been identified as the tephra deposits. Systematic grain-size measurements also suggest that sediments from the northern Okinawa Trough are made up of terrigenous materials and volcanic ashes with different proportion during the Holocene. The sediments of tephra layers in Core CSH1 show bi-modal patterns in grain-size distribution with modal grain-sizes of 74.3 and 7.81 μm,respectively. According to the radiocarbon dating on shells of zooplankton foraminifera, two tephra layers in Core CSH1, formed at 7 250 and 10 870 a BP (cal), approximately correspond to the K-Ah tephra [7 300 a BP (cal)] and the eruption of Kuju Volcano (12~10 ka BP), respectively.

  1. Rootless tephra stratigraphy and emplacement processes

    Science.gov (United States)

    Hamilton, Christopher W.; Fitch, Erin P.; Fagents, Sarah A.; Thordarson, Thorvaldur

    2017-01-01

    Volcanic rootless cones are the products of thermohydraulic explosions involving rapid heat transfer from active lava (fuel) to external sources of water (coolant). Rootless eruptions are attributed to molten fuel-coolant interactions (MFCIs), but previous studies have not performed systematic investigations of rootless tephrostratigraphy and grain-size distributions to establish a baseline for evaluating relationships between environmental factors, MFCI efficiency, fragmentation, and patterns of tephra dispersal. This study examines a 13.55-m-thick vertical section through an archetypal rootless tephra sequence, which includes a rhythmic succession of 28 bed pairs. Each bed pair is interpreted to be the result of a discrete explosion cycle, with fine-grained basal material emplaced dominantly as tephra fall during an energetic opening phase, followed by the deposition of coarser-grained material mainly as ballistic ejecta during a weaker coda phase. Nine additional layers are interleaved throughout the stratigraphy and are interpreted to be dilute pyroclastic density current (PDC) deposits. Overall, the stratigraphy divides into four units: unit 1 contains the largest number of sediment-rich PDC deposits, units 2 and 3 are dominated by a rhythmic succession of bed pairs, and unit 4 includes welded layers. This pattern is consistent with a general decrease in MFCI efficiency due to the depletion of locally available coolant (i.e., groundwater or wet sediments). Changing conduit/vent geometries, mixing conditions, coolant and melt temperatures, and/or coolant impurities may also have affected MFCI efficiency, but the rhythmic nature of the bed pairs implies a periodic explosion process, which can be explained by temporary increases in the water-to-lava mass ratio during cycles of groundwater recharge.

  2. Sedimentation rates and erosion changes recorded in recent sediments of Lake Piaseczno, south-eastern Poland

    Science.gov (United States)

    Tylmann, Wojciech; Turczyński, Marek; Kinder, Małgorzata

    2009-10-01

    This paper presents the dating results and basic analyses of recent sediments from Lake Piaseczno. The age of sediments was determined using the 210Pb method and constant flux: constant sedimentation (CF: CS) model. The estimated timescale was in agreement with the AMS14C date from the base of the core. The mean sediment accumulation rate during the last 100 years was calculated as 0.025 g cm-2 a-1. Based on the radiocarbon date, the rate of sediment accumulation below the 210Pb dating horizon was estimated as 0.066 g cm-2 a-1. The variability of main physical properties and sediment components along the core was analysed as well. The sediments were characterised by a very high water content (>80%). Carbonates were either not present or at a very low level (interesting record of increasing erosion intensity in the catchment area. Analysis of archival cartographic materials demonstrated that the most likely reason for the enhanced transport of minerogenic matter to the lake was deforestation caused by human activity in the beginning of the 20th century.

  3. Tools and techniques for developing tephra stratigraphies in lake cores: A case study from the basaltic Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Hopkins, Jenni L.; Millet, Marc-Alban; Timm, Christian; Wilson, Colin J. N.; Leonard, Graham S.; Palin, J. Michael; Neil, Helen

    2015-09-01

    Probabilistic hazard forecasting for a volcanic region relies on understanding and reconstructing the eruptive record (derived potentially from proximal as well as distal volcanoes). Tephrostratigraphy is commonly used as a reconstructive tool by cross-correlating tephra deposits to create a stratigraphic framework that can be used to assess magnitude-frequency relationships for eruptive histories. When applied to widespread rhyolitic deposits, tephra identifications and correlations have been successful; however, the identification and correlation of basaltic tephras are more problematic. Here, using tephras in drill cores from six maars in the Auckland Volcanic Field (AVF), New Zealand, we show how X-ray density scanning coupled with magnetic susceptibility analysis can be used to accurately and reliably identify basaltic glass shard-bearing horizons in lacustrine sediments and which, when combined with the major and trace element signatures of the tephras, can be used to distinguish primary from reworked layers. After reliably identifying primary vs. reworked basaltic horizons within the cores, we detail an improved method for cross-core correlation based on stratigraphy and geochemical fingerprinting. We present major and trace element data for individual glass shards from 57 separate basaltic horizons identified within the cores. Our results suggest that in cases where major element compositions (SiO2, CaO, Al2O3, FeO, MgO) do not provide unambiguous correlations, trace elements (e.g. La, Gd, Yb, Zr, Nb, Nd) and trace element ratios (e.g. [La/Yb]N, [Gd/Yb]N, [Zr/Yb]N) are successful in improving the compositional distinction between the AVF basaltic tephra horizons, thereby allowing an improved eruptive history of the AVF to be reconstructed.

  4. Geochemical Characterization of Late Pleistocene and Holocene Tephra Layers from the Basin of Mexico, Central Mexico

    Science.gov (United States)

    Ortega-Guerrero, Beatriz; Newton, Anthony J.

    1998-07-01

    In order to aid palaeoenvironmental research of Late Pleistocene and Holocene deposits of central Mexico, tephra layers collected from the sediments of the Texcoco and Chalco sub-basins, in the southern part of the Basin of Mexico, are geochemically characterized and used as stratigraphic markers. The tephra layers range in composition from basaltic andesites to rhyolites and are calc-alkaline. The tephras range in age from >34,000 to ca. 2600 14C yr B.P. New names are used informally to designate correlated tephras. The Tlahuac tephra is present in Chalco, at a depth of 18 m; in the southeastern part of Texcoco, at a depth of around 10 m; and at the Tlapacoya archaeological site, where it had been mistakenly described as basaltic. This basalt-andesite tephra is dated to at least 34,000 14C yr B.P. The Tlapacoya 1 tephra is dated to between 15,020 ± 450 and 14,430 ± 190 yr B.P. and is present in all Chalco sections. The Tlapacoya 2 tephra corresponds to the previously described "pomez gruesa con fragmentos de andesita" (ca. 14,400 yr B.P.) and is present in all Chalco and Texcoco sections. The likely source of these three tephras is the volcano Popocatepetl. Tephra II at Chalco dates to 12,520 ± 135 yr B.P. and correlates with the Upper Toluca Pumice from Nevado de Toluca volcano. These represent the first geochemical glass-shard analysis of tephras from the Basin of Mexico, and so further research is necessary before a reliable tephrochronology can be established.

  5. Geochemistry records from laminated sediments of Shira Lake (Russian Asia)

    Science.gov (United States)

    Phedorin, M.; Vologina, E.; Drebuschak, M.; Tolomeev, A.; Kirichenko, I.; Toyabin, A.

    2009-04-01

    We measured downcore elements distributions in five cores collected across the Shira Lake situated in Central part of Asia (E90o12', N54o30'). The lake is small (32km2), saline (ca.20g/l SO4-, Cl-, Na+, Mg+, K+), being filled with regional precipitation of about 300mm/year (mainly through one major tributary, river Son) and has no surface outflow. The aim of our study was to reconstruct history of changes in the regime of the lake that happened both before and during period of instrumental meteorological observations. In particular, we were interested in lake-level changes due to evaporation, water supply from surface and from underground sources, and in changes of bioproduction in the lake as well. To construct depth-age model for the cores, we measured Cs-137 and unsupported Pb-210 in top layers of the cores. The sedimentation rate thus identified varied in the range of 1-2 mm/year for different cores. We visually observed fine sedimentation ‘rhythms' having thickness of about 0.x-2.x mm: these layers may now be reliably identified as annual lamination. We also determined concentrations of elements in the sediments by recording x-ray fluorescence (XRF) spectra when continuously scanning the halves of the cores under sharp synchrotron radiation (SR) beam, using an instrument described in (Zolotarev et al., 2001). The resolution of the scanning was 0.1 mm. After processing of the measured XRF-SR data as in (Phedorin and Goldberg, 2005) we obtained downcore records of 20 elements. We correlated all five cores employing elements patterns. We qualitatively identified variations in surface-water supply treating markers of ‘clastic' material (Ti, Rb, Zr). We identified downcore variations in authgenic mineralization, which appeared to have different kinds: Ca-related, Sr-related, Ba-related, Fe-related. We tried to assess biogenic production changes from Br distribution, admitting analogy of Br in Shira sediments to Br in Lake Baikal sediments (Phedorin et al., 2000

  6. Holocene evolution of the River Nile drainage system as revealed from the Lake Dendi sediment record, central Ethiopian highlands

    Science.gov (United States)

    Wagner, B.; Viehberg, F. A.; Wennrich, V.; Junginger, A.; Kolvenbach, A.; Rethemeyer, J.; Schaebitz, F.; Schmiedl, G. H.

    2015-12-01

    A 12 m long sediment sequence from Dendi Crater lakes, located on the central Ethiopian Plateau, was analysed with sedimentological and geochemical methods to reconstruct the regional environmental history. Bulk organic carbon samples from 23 horizons throughout the sequence were used for AMS radiocarbon dating and indicate that the sediment sequence spans the last ca. 12 cal kyr BP. Microscope analyses and sedimentological data reveal three tephra layers, of which the most prominent layer with a thickness of ~2 m was deposited at 10.2 cal kyr BP and probably originates from an eruption of the Wenchi crater 12 km to the west of the Dendi lakes. Sedimentological data of the pelagic deposits indicate shifts in erosion and rainfall throughout the record. A decrease in Ca and Sr at 11.6 cal kyr BP is related to the shift of less humid condition during the Younger Dryas (YD) to the return to full humid conditions of the African Humid Period (AHP). Single thin horizons with high carbonate content or high Ti and K imply that short spells of dry conditions and significantly increased rainfall superimpose the generally more humid conditions during the AHP. The end of the AHP is gradual. Relatively stable and less humid conditions characterised the Dendi Crater lakes until around 3.9 cal kyr BP. A highly variable increase in clastic matter over the last 1500 years indicates higher erosion due to short-term variations in precipitation within the Dendi catchment. Overall, the sediment record suggests moderate change of precipitation during the Holocene, which is probably due to their exposed location in the Ethiopian highlands. The data from the Dendi Crater lakes show, in concert with other records from the Nile catchment and the Eastern Mediterranean Sea (EMS), that the Blue Nile provided the main freshwater source for maintaining EMS stratification and sapropel S1 formation between ca. 10.0 and 8.7 cal kyr BP. Subsequent aridification is recorded from equatorial East Africa

  7. Mono Lake sediments preserve a record of recent environmental change

    Science.gov (United States)

    Meixnerova, J.; Betts, M.; Westacott, S.; Ingalls, M.; Miller, L. G.; Sessions, A. L.; Trower, L.; Geobiology Course, A.

    2017-12-01

    Modern Mono Lake is a geochemically unique closed-basin, hypersaline soda lake. Since 1941, anthropogenic water diversions have decreased the lake's volume and water level, driving changes in water chemistry and ecology. Mono Lake sediments offer an opportunity to investigate the nature and extent of these changes. We analyzed a 70 cm sediment core from the center of Mono Lake recording the past 116 years of deposition. At the time of recovery, the entire core was dark green. 16S rRNA gene analysis indicated a sedimentary bacterial community dominated by Cyanobacteria. SEM imaging revealed abundant, well-preserved diatom frustules below 10 cm core depth, in contrast they are nearly absent above 10 cm depth. Fatty acid (FAME) biomarkers for diatoms and algal sterols were present throughout the core in varying concentrations. Phytol was exceptionally abundant in the core; ratios of phytol/C-18 FAME were commonly >200. The δ13Corg ranged between -17.5 and -20‰ in the lower 52 cm of the core while the upper part shows significant decrease of δ13Corg to -28‰. We interpret the shift in δ13Corg as an ecological transition from mainly diatoms in the lower core towards the green alga Picocystis, which is the main primary producer today and has a δ13Corg value of -32.5‰. The onset of this change dates back 23 years, which roughly coincides with the highest reported salinity, 88 g/L in 1995. We hypothesize that diatoms gradually became marginalized as a result of hypersaline conditions. We also observed a variety of trends that may be characterized as unique fingerprints of Mono Lake. The unusually high abundance of phytol was consistent with the core's pervasive green coloring and could potentially indicate a higher preservation potential of phytol under alkaline conditions. Throughout the core, δ15Norg fluctuated between +10 and +13‰. Such atypical enrichment in δ15Norg could be explained by NH4 dissociation and subsequent NH3 volatilization under high p

  8. Ferromagnetic response of a sediment record from Lake Soppensee

    Science.gov (United States)

    Kind, J.; García-Rubio, I.; Gehring, A. U.

    2012-12-01

    Environmental magnetism uses the spatial and temporal occurrence of magnetic carriers as diagnostic tools to detect environmental changes. Concentration, composition, grain size, and configuration of magnetite can be indicative of the origin of this magnetic carrier. In order to reconstruct the development of Lake Soppensee (Central Switzerland) since the late Pleistocene, a detailed ferromagnetic resonance (FMR) spectroscopy analysis was applied. FMR is a powerful tool to probe the magnetic properties of ferrimagnetic materials. Sediments from Lake Soppensee were analyzed in order to deduce different processes causing the formation of magnetite and its preservation. Based on the occurrence of magnetite, the sediment record can be subdivided into three stages. The first stage, attributed to the deglaciation contains superparamagnetic (SP) magnetite that is detected by the low-temperature FMR analysis. The simultaneous occurrence of SP magnetite in sediments with predominant hematite is interpreted as magnetite formation in reducing interstitial voids within a prevailing oxic environment. The second stage, assigned to the Bølling/Allerød - Younger Dryas period contains stable single domain (SSD) magnetite in varying concentrations. During the Bølling/Allerød denser vegetation cover led to an increase of organic matter in the depositional environment, which accelerated the microbial activity and the consumption of oxygen and the enhanced formation of SSD magnetite. An opposite trend is found for the cold Younger Dryas period. The third stage during the fairly stable Holocene exhibits the formation of SSD magnetite solely. Even though no drastic climatic changes are documented throughout the Holocene, the magnetite content varies considerably. In sediments with high magnetite content, dispersed magnetite particles and magnetite in chain-like configuration were detected by anisotropy traits inferred from the FMR spectra. This configuration provides clear evidence

  9. Lithostratigraphy and microfacies analyses of the Lateglacial and early Holocene sediment record from Lake Haemelsee (Germany)

    Science.gov (United States)

    Haliuc, Aritina; Brauer, Achim; Dulski, Peter; Engels, Stefan; Lane, Christine

    2015-04-01

    sedimentary conditions to climatic changes during Allerød and Allerød/Younger Dryas transition. An increased detrital sediment flux characterizes lithozone 6 and, most probably reflects the Younger Dryas cold interval. This interpretation is supported by the late Allerød Laacher See Tephra, an important chronostratigraphic marker horizon to link the floating 625 varve year chronology for the Allerød interstadial to an absolute time scale. Also, the preliminary pollen data provided the biostratigraphical information for establishing the lateglacial boundaries. Poorly preserved organic laminas are characteristic for lithozone 7 (1445-1474 cm). Our preliminary results demonstrate that the lake system responded sensitively to rapid and short-term climatic changes and these responses are well-expressed in sedimentological and geochemical variability.

  10. Comparison of estuarine sediment record with modelled rates of sediment supply from a western European catchment since 1500

    Science.gov (United States)

    Poirier, Clément; Poitevin, Cyril; Chaumillon, Éric

    2016-09-01

    Marine and estuarine sediment records reporting impacts of historical land use changes exist worldwide, but they are rarely supported by direct quantified evidence of changes in denudation rates on the related catchments. Here we implement a spatially-resolved RUSLE soil erosion model on the 10 000 km2 Charente catchment (France), supplied with realistic scenarios of land-cover and climate changes since 1500, and compare the results to a 14C-dated estuarine sediment record. Despite approximations, the model correctly predicts present-day Charente river sediment load. Back-cast modelling suggests that the Charente catchment is an interesting case where the sediment supply did not change despite increase in soil erosion resulting from 18th-century deforestation because it was mitigated by drier climate during the same period. Silt-sand alternations evidenced in the sediment record were correlated with sub-decadal rainfall variability.

  11. The role of tephra studies in African paleoanthropology as exemplified by the Sidi Hakoma Tuff

    Science.gov (United States)

    WoldeGabriel, Giday; Endale, Tamrat; White, Tim D.; Thouveny, Nicolas; Hart, William K.; Renne, Paul R.; Asfaw, Berhane

    2013-01-01

    Beginning in the 1960s, geological and paleoanthropological exploration of the Ethiopian rift system's basins have led to the discovery and assembly of the most comprehensive record of human biological and technological change during the last 6 million years. The hominid fossils, including partial skeletons, were primarily discovered in the Afar Rift, the Main Ethiopian Rift, and in the Omo Basin of the broadly rifted zone of SW Ethiopia. The paleoanthropological research areas within the SW Afar Rift that have yielded many diverse hominid species and the oldest stone tools are, from north to south, Woranso-Mille (aff. Ardipithecus and Au. afarensis), Hadar (Au. afarensis, Homo sp.), Dikika (Au. afarensis), Gona (Ar. kadabba, Ar. ramidus, H. erectus, and oldest stone tools), Middle Awash (Ar. kadabba, Ar. ramidus, Au. anamensis, Au. afarensis, Au. garhi, H. erectus, H. rhodesiensis, H. sapiens idaltu, and the oldest paleo-butchery locality), and Galili (Au. afarensis). Additional hominid remains were discovered at Melka Kunture on the banks of the Awash River near its source along the western margin of the central part of the Main Ethiopian Rift (H. erectus), at Konso (H. erectus and A. boisei), and at the southern end of the MER, and in the Omo Basin (Au. anamensis, Au. afarensis, Au. aethiopicus, Au. boisei, H. habilis, and H. erectus). Distal and sometimes proximal tephra units interbedded within fossilifeous sedimentary deposits have become key elements in this work by providing chronological and correlative control and depositional contexts. Several regional tephra markers have been identified within the northern half of the eastern African rift valley in Ethiopia and Kenya, and in marine sediments of the Gulf of Aden Rift and the NW Indian Ocean. Out of the many regional tephra stratigraphic markers that range in age from the early Pliocene (3.97 Ma) to the late Pleistocene (0.16 Ma), the Sidi Hakoma Tuff (SHT) has been more widely identified and thoroughly

  12. Promise and pitfalls for characterizing and correlating the zeolitically altered tephra of the Pleistocene Peninj Group, Tanzania

    Science.gov (United States)

    McHenry, Lindsay J.; Luque, Luis; Gómez, José Ángel; Diez-Martín, Fernando

    2011-05-01

    The Pleistocene Humbu and Moinik formations of the Peninj Group in northern Tanzania preserve an important archaeological and paleontological record, in addition to a record of local volcanism in the form of tephra and lavas. Samples of the major Humbu and Moinik formations' basaltic and trachytic tephra were collected and characterized using phenocryst composition and both primary and authigenic mineral assemblage, since the volcanic glass was completely altered to zeolite. Some tephra are distinguishable solely using phenocrysts, but some are too similar in mineral composition or too poor in phenocrysts to definitively "fingerprint" without glass. Titanomagnetite phenocrysts were mostly altered; characterization was thus limited to feldspar, augite, and hornblende compositions for most tephra. Phenocryst compositions were compared to Olduvai tephra compositions to see if any regional tephra could be identified that could help correlate the sites. Augite or hornblende composition rules out potential correlations of Olduvai Bed I Tuff IF and the Bed II Bird Print Tuff or Tuff IID to otherwise similar Peninj Group tephra. Despite their overlap in age and locations at less than ~ 80 km from the Ngorongoro Volcanic Highlands, Peninj and Olduvai have different tephra records, which limits the possibilities for establishing a regional tephrostratigraphic framework.

  13. Clastic sediment flux to tropical Andean lakes: records of glaciation and soil erosion

    Science.gov (United States)

    Rodbell, Donald T.; Seltzer, Geoffrey O.; Mark, Bryan G.; Smith, Jacqueline A.; Abbott, Mark B.

    2008-08-01

    We developed records of clastic sediment flux to 13 alpine lakes in Peru, Ecuador, and Bolivia, and compared these with independently dated records of regional glaciation. Our objectives are to determine whether a strong relationship exists between the extent of ice cover in the region and the rate of clastic sediment delivery to alpine lakes, and thus whether clastic sediment records serve as reliable proxies for glaciation during the late Pleistocene. We isolated the clastic component in lake sediment cores by removing the majority of the biogenic and authigenic components from the bulk sediment record, and we dated cores by a combination of radiocarbon and tephrochronology. In order to partially account for intra-basin differences in sediment focusing, bedrock erosivity, and sediment availability, we normalized each record to the weighted mean value of clastic sediment flux for each respective core. This enabled the stacking of all 13 lake records to produce a composite record that is generally representative of the tropical Andes. There is a striking similarity between the composite record of clastic sediment flux and the distribution of ˜100 cosmogenic radionuclide (CRN) exposure ages for erratics on moraine crests in the central Peruvian and northern Bolivian Andes. The extent of ice cover thus appears to be the primary variable controlling the delivery of clastic sediment to alpine lakes in the region, which bolsters the increasing use of clastic sediment flux as a proxy for the extent of ice cover in the region. The CRN moraine record and the stacked lake core composite record together indicate that the expansion of ice cover and concomitant increase in clastic sediment flux began at least 40 ka, and the local last glacial maximum (LLGM) culminated between 30 and 20 ka. A decline in clastic sediment flux that began ˜20 ka appears to mark the onset of deglaciation from the LLGM, at least one millennium prior to significant warming in high latitude regions

  14. Geochemical characterization of mid-distal Nisyros tephra on Datça peninsula (southwestern Anatolia)

    Science.gov (United States)

    Gençalioğlu-Kuşcu, Gonca; Uslular, Göksu

    2018-04-01

    We present new distal records of tephra deposits that overly the Kos ignimbrite in seven locations of Datça peninsula. Tephra in one of these locations were previously associated with Nisyros Kyra sub-unit based only on the field characteristics. We use different proxies such as field observations, petrography, mineral, glass, and whole-rock chemistry in order to characterize and correlate the previously and recently identified pumice fall deposits on Datça. The total thickness of the fall deposit reaches to 3.5 m. The size of the pumice clasts is generally within the range of lapilli, and they have vitrophyric texture consisting mainly of plagioclase (andesine to labradorite) with scarce clinopyroxene (diopside to augite), olivine (Fo48-50), amphibole (magnesio-hastingsite), and biotite crystals. Amphibole is a ubiquitous phenocryst in all Datça tephra units and used as a criterion for the correlation. Glass major element analyses by EMPA reveal two different groups with andesitic and dacitic compositions. Difference in silica content (up to ca. 4 wt%) detected in the same specimen also designates the heterogeneity in pumice glass. This heterogeneity in glass composition is also supported by the frequent occurrence of banded pumice clasts in Datça tephra. Whole-rock composition of the pumice is mainly andesitic with calc-alkaline affinity. Multi-element patterns on primitive-mantle normalized diagram display typical arc-magmatism signature (i.e. depletion in Nb, Ta, Ti, and P). In order to check and eliminate the potential alternatives, we compared the distal deposits on Datça not only with Kyra, but also with other Nisyros tephra units. Yet, Kyra is the only unit that has comparable depositional characteristics, calcic amphibole crystals, andesitic-dacitic glass and whole-rock chemistry, and distal tephra deposits on neighboring islands (Tilos and Chalki). Therefore, we associate Datça tephra deposits with some proximal Kyra subunits of intermediate

  15. The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea

    Science.gov (United States)

    Pearce, Christof; Varhelyi, Aron; Wastegård, Stefan; Muschitiello, Francesco; Barrientos, Natalia; O'Regan, Matt; Cronin, Thomas M.; Gemery, Laura; Semiletov, Igor; Backman, Jan; Jakobsson, Martin

    2017-04-01

    The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid-late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed across a more than 1.5 m long sediment sequence. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca. 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major influence of typically carbon-old Pacific waters, and it agrees well with recent estimates of ΔR along the northwest Alaskan coast, possibly

  16. Compositional Variations of Paleogene and Neogene Tephra From the Northern Izu-Bonin-Mariana Arc

    Science.gov (United States)

    Tepley, F. J., III; Barth, A. P.; Brandl, P. A.; Hickey-Vargas, R.; Jiang, F.; Kanayama, K.; Kusano, Y.; Li, H.; Marsaglia, K. M.; McCarthy, A.; Meffre, S.; Savov, I. P.; Yogodzinski, G. M.

    2014-12-01

    A primary objective of IODP Expedition 351 was to evaluate arc initiation processes of the Izu-Bonin-Mariana (IBM) volcanic arc and its compositional evolution through time. To this end, a single thick section of sediment overlying oceanic crust was cored in the Amami Sankaku Basin where a complete sediment record of arc inception and evolution is preserved. This sediment record includes ash and pyroclasts, deposited in fore-arc, arc, and back-arc settings, likely associated with both the ~49-25 Ma emergent IBM volcanic arc and the evolving Ryukyu-Kyushu volcanic arc. Our goal was to assess the major element evolution of the nascent and evolving IBM system using the temporally constrained record of the early and developing system. In all, more than 100 ash and tuff layers, and pyroclastic fragments were selected from temporally resolved portions of the core, and from representative fractions of the overall core ("core catcher"). The samples were prepared to determine major and minor element compositions via electron microprobe analyses. This ash and pyroclast record will allow us to 1) resolve the Paleogene evolutionary history of the northern IBM arc in greater detail; 2) determine compositional variations of this portion of the IBM arc through time; 3) compare the acquired data to an extensive whole rock and tephra dataset from other segments of the IBM arc; 4) test hypotheses of northern IBM arc evolution and the involvement of different source reservoirs; and 5) mark important stratigraphic markers associated with the Neogene volcanic history of the adjacent evolving Ryukyu-Kyushu arc.

  17. The influence of hydrology on lacustrine sediment contaminant records

    Science.gov (United States)

    Rosen, Michael R.

    2015-01-01

    The way water flows to a lake, through streams, as runoff, or as groundwater, can control the distribution and mass of sediment and contaminants deposited. Whether a lake is large or small, deep or shallow, open or closed, the movement of water to a lake and the circulation patterns of water within a lake control how and where sediment and contaminants are deposited. Particle-associated contaminants may stay close to the input source of contamination or be transported by currents to bathymetric lows. A complex morphology of the lake bottom or shoreline can also affect how contaminants will be distributed. Dissolved contaminants may be widely dispersed in smaller lakes, but may be diluted in large lakes away from the source. Although dissolved contaminants may not be deposited in lake sediments, the impact of dissolved contaminants (such as nitrogen) may be reflected by the ecosystem. For instance, increased phosphorus and nitrogen may increase organic content or algal biomass, and contribute to eutrophication of the lake over time. Changes in oxidation-reduction potential at the sediment-water interface may either release some contaminants to the water column or conversely deposit other contaminants to the sediment depending on the compound’s chemical characteristics. Changes in land use generally affect the hydrology of the watershed surrounding a lake, providing more runoff if soil binding vegetation is removed or if more impervious cover (roads and buildings) is increased. Groundwater inputs may change if pumping of the aquifer connected to the lake occurs. Even if groundwater is only a small portion of the volume of water entering a lake, if contaminant concentrations in the aquifer are high compared to surface water inputs, the mass of contaminants from groundwater may be as, or more, important than surface water contributions.

  18. The Mount Edgecumbe tephra deposits, a marker horizon in southeastern Alaska near the Pleistocene-Holocene boundary

    Science.gov (United States)

    Riehle, J.R.; Mann, D.H.; Peteet, D.M.; Engstrom, D.R.; Brew, D.A.; Meyer, C.E.

    1992-01-01

    Late Pleistocene tephra deposits found from Sitka to Juneau and Lituya Bay are assigned to a source at the Mount Edgecumbe volcanic field, based on similarity of glass compositions to nearvent deposits and on thinning away from Kruzof Island. The sequence of near-vent layers is basaltic andesite and andesite at the base, rhyolite, and mixed dacite and rhyolite on top. The only breaks in the tephra sequence are two 1-mm-thick silt partings in a lake-sediment core, indicating a depositional interval from basaltic andesite to dacite of no more than about a millennium. Tephra deposits at sites >30 km from the vent are solely dacite and rhyolite and are 10,600 to 11,400 14C yr old based on interpretation of 18 radiocarbon ages, including 5 by accelerator mass spectrometry (AMS). Basaltic andesite and andesite deposits nearer the vent are as much as 12,000 yr old. Discrepancy among radiocarbon ages of upland tephra deposits provisionally correlated as the same grainfall is resolvable within ??2 ?? of analytical uncertainty. Comparison of bulk and AMS ages in one sediment core indicates a systematic bias of +600 to +1100 yr for the bulk ages; correlation of tephra deposits among upland and lacustrine sites implies an additional discrepancy of 200-400 yr between upland (relatively too young) and lacustrine ages. In any case, the Mount Edgecumbe tephra deposits are a widespread, latest Pleistocene stratigraphic marker that serves to emphasize the uncertainty in dating biogenic material from southeastern Alaska. ?? 1992.

  19. Resolving the age of Wilson Creek Formation tephras and the Mono Lake excursion using high-resolution SIMS dating of allanite and zircon rims

    Science.gov (United States)

    Vazquez, J. A.; Lidzbarski, M. I.

    2012-12-01

    Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and interbedded rhyolitic tephras yield discordant 14C and 40Ar/39Ar results due to open-system effects, carbon reservoir uncertainties, as well as abundant xenocrysts entrained during eruption. Ion microprobe (SIMS) 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yields ages that effectively date eruption of key tephra beds and resolve age uncertainties about the Wilson Creek stratigraphy. To date the final several micrometers of crystal growth, individual allanite and zircon crystals were embedded in soft indium to allow sampling of unpolished rims. Isochron ages derived from rims on coexisting allanite and zircon (± glass) from hand-selected pumiceous pyroclasts delimit the timing of Wilson Creek sedimentation between Ashes 7 and 19 (numbering of Lajoie, 1968) to the interval between ca. 27 to ca. 62 ka. The interiors of individual allanite and zircon crystals sectioned in standard SIMS mounts yield model 238U-230Th ages that are mostly hydrologic responses in the Sierra Nevada and Mono Basin to climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation. Moreover, the results demonstrate that high-spatial resolution SIMS dating of accessory mineral rims is an alternative and promising approach for resolving the depositional ages of silicic tephras containing minerals that crystallized over protracted intervals or that are plagued by incorporation of xenocrysts

  20. Tephra Fallout Hazard Assessment for VEI5 Plinian Eruption at Kuju Volcano, Japan, Using TEPHRA2

    Science.gov (United States)

    Tsuji, Tomohiro; Ikeda, Michiharu; Kishimoto, Hiroshi; Fujita, Koji; Nishizaka, Naoki; Onishi, Kozo

    2017-06-01

    Tephra fallout has a potential impact on engineered structures and systems at nuclear power plants. We provide the first report estimating potential accumulations of tephra fallout as big as VEI5 eruption from Kuju Volcano and calculated hazard curves at the Ikata Power Plant, using the TEPHRA2 computer program. We reconstructed the eruptive parameters of Kj-P1 tephra fallout deposit based on geological survey and literature review. A series of parameter studies were carried out to determine the best values of empirical parameters, such as diffusion coefficient and the fall time threshold. Based on such a reconstruction, we represent probabilistic analyses which assess the variation in meteorological condition, using wind profiles extracted from a 22 year long wind dataset. The obtained hazard curves and probability maps of tephra fallout associated to a Plinian eruption were used to discuss the exceeding probability at the site and the implications of such a severe eruption scenario.

  1. Arctic deltaic lake sediments as recorders of fluvial organic matter deposition

    Directory of Open Access Journals (Sweden)

    Jorien E Vonk

    2016-08-01

    Full Text Available Arctic deltas are dynamic and vulnerable regions that play a key role in land-ocean interactions and the global carbon cycle. Delta lakes may provide valuable historical records of the quality and quantity of fluvial fluxes, parameters that are challenging to investigate in these remote regions. Here we study lakes from across the Mackenzie Delta, Arctic Canada, that receive fluvial sediments from the Mackenzie River when spring flood water levels rise above natural levees. We compare downcore lake sediments with suspended sediments collected during the spring flood, using bulk (% organic carbon, % total nitrogen, 13C, 14C and molecular organic geochemistry (lignin, leaf waxes. High-resolution age models (137Cs, 210Pb of downcore lake sediment records (n=11 along with lamina counting on high-resolution radiographs show sediment deposition frequencies ranging between annually to every 15 years. Down-core geochemical variability in a representative delta lake sediment core is consistent with historical variability in spring flood hydrology (variability in peak discharge, ice jamming, peak water levels. Comparison with earlier published Mackenzie River depth profiles shows that (i lake sediments reflect the riverine surface suspended load, and (ii hydrodynamic sorting patterns related to spring flood characteristics are reflected in the lake sediments. Bulk and molecular geochemistry of suspended particulate matter from the spring flood peak and lake sediments are relatively similar showing a mixture of modern higher-plant derived material, older terrestrial permafrost material, and old rock-derived material. This suggests that deltaic lake sedimentary records hold great promise as recorders of past (century-scale riverine fluxes and may prove instrumental in shedding light on past behaviour of arctic rivers, as well as how they respond to a changing climate.

  2. Grain size dependent magnetic discrimination of Iceland and South Greenland terrestrial sediments in the northern North Atlantic sediment record

    Science.gov (United States)

    Hatfield, Robert G.; Stoner, Joseph S.; Reilly, Brendan T.; Tepley, Frank J.; Wheeler, Benjamin H.; Housen, Bernard A.

    2017-09-01

    We use isothermal and temperature dependent in-field and magnetic remanence methods together with electron microscopy to characterize different sieved size fractions from terrestrial sediments collected in Iceland and southern Greenland. The magnetic fraction of Greenland silts (3-63 μm) and sands (>63 μm) is primarily composed of near-stoichiometric magnetite that may be oxidized in the finer clay (samples, in contrast to coarser PSD and multi-domain (MD) discrete magnetites from southern Greenland. We demonstrate the potential of using magnetic properties of the silt fraction for source unmixing by creating known endmember mixtures and by using naturally mixed marine sediments from the Eirik Ridge south of Greenland. We develop a novel approach to ferrimagnetic source unmixing by using low temperature magnetic susceptibility curves that are sensitive to the different crystallinity and cation substitution characteristics of the different source regions. Covariation of these properties with hysteresis parameters suggests sediment source changes have driven the magnetic mineral variations observed in Eirik Ridge sediments since the last glacial maximum. These observations assist the development of a routine method and interpretative framework to quantitatively determine provenance in a geologically realistic and meaningful way and assess how different processes combine to drive magnetic variation in the North Atlantic sediment record.

  3. The preglacial sediment record of Lake Ladoga, NW Russia - first results from a multi-proxy study on a 23 m sediment record

    Science.gov (United States)

    Gromig, R.; Melles, M.; Wagner, B.; Krastel, S.; Andreev, A.; Fedorov, G.; Just, J.; Wennrich, V.; Savelieva, L.; Subetto, D.; Shumilovskikh, L.

    2016-12-01

    The joint German-Russian project 'PLOT - Paleolimnological Transect' aims to recover lake sediment sequences along a more than 6000 km long longitudinal transect across the Eurasian Arctic in order to study the Late Quaternary climatic and environmental history. The eastern end of the PLOT transect is formed by the well-studied record from Lake El'gygytgyn (NE Siberia). Lake Ladoga (N 60°50' E 31°30') is Europe's largest lake, both by size and volume and forms the westernmost end of the transect. Whereas modern sedimentation as well as the Holocene and Late Glacial history of Lake Ladoga have intensely been studied, the preglacial history of the lake is poorly studied to date by sediment cores drilled in the 1930's. A seismic survey of Lake Ladoga in summer 2013 revealed unconformities in the western lake basin, which may separate preglacial sediments in isolated depressions from Late Glacial and Holocene sediment successions above. A 23 m long sediment core (Co1309) was retrieved from one of these depressions. Core Co1309 was investigated by XRF-scanning, magnetic susceptibility measurements, as well as pollen, grain-size, and bio-geochemical analyses. An age-depth model combining radiocarbon, OSL, and paleomagnetic dates is in progress. Both, the pollen results and the OSL ages from the base of the record indicate a deposition during MIS 5e (Eemian). The well sorted reddish sands from this interval contain dinoflagellates suggesting at least brackish conditions, likely due to the existence of a gateway connecting a precursor of the Baltic Sea with the White Sea via Lake Ladoga. The Late Glacial sequence consists of greyish varved clays of decreasing thickness upwards with sporadically intercalated sand layers. The Holocene sequence is composed of brownish diatomaceous silty clay with minor proportions of sand.

  4. Late Eocene impact events recorded in deep-sea sediments

    Science.gov (United States)

    Glass, B. P.

    1988-01-01

    Raup and Sepkoski proposed that mass extinctions have occurred every 26 Myr during the last 250 Myr. In order to explain this 26 Myr periodicity, it was proposed that the mass extinctions were caused by periodic increases in cometary impacts. One method to test this hypothesis is to determine if there were periodic increases in impact events (based on crater ages) that correlate with mass extinctions. A way to test the hypothesis that mass extinctions were caused by periodic increases in impact cratering is to look for evidence of impact events in deep-sea deposits. This method allows direct observation of the temporal relationship between impact events and extinctions as recorded in the sedimentary record. There is evidence in the deep-sea record for two (possibly three) impact events in the late Eocene. The younger event, represented by the North American microtektite layer, is not associated with an Ir anomaly. The older event, defined by the cpx spherule layer, is associated with an Ir anomaly. However, neither of the two impact events recorded in late Eocene deposits appears to be associated with an unusual number of extinctions. Thus there is little evidence in the deep-sea record for an impact-related mass extinction in the late Eocene.

  5. Hidden plastics of Lake Ontario, Canada and their potential preservation in the sediment record

    International Nuclear Information System (INIS)

    Corcoran, Patricia L.; Norris, Todd; Ceccanese, Trevor; Walzak, Mary Jane; Helm, Paul A.; Marvin, Chris H.

    2015-01-01

    Microplastics are a source of environmental pollution resulting from degradation of plastic products and spillage of resin pellets. We report the amounts of microplastics from various sites of Lake Ontario and evaluate their potential for preservation in the sediment record. A total of 4635 pellets were sampled from the Humber Bay shoreline on three sampling dates. Pellet colours were similar to those from the Humber River bank, suggesting that the river is a pathway for plastics transport into Lake Ontario. Once in the lake, high density microplastics, including mineral-polyethylene and mineral-polypropylene mixtures, sink to the bottom. The minerals may be fillers that were combined with plastics during production, or may have adsorbed to the surfaces of the polymers in the water column or on the lake bottom. Based on sediment depths and accumulation rates, microplastics have accumulated in the offshore region for less than 38 years. Their burial increases the chance of microplastics preservation. Shoreline pellets may not be preserved because they are mingled with organic debris that is reworked during storm events. - Highlights: • We determine the amount of microplastics in Lake Ontario shore and bottom sediments. • Pellet preservation in shoreline sediment is unlikely. • Microplastics have been accumulating in bottom sediments over <38 years. • Buried plastics in lake bottom sediment have a high potential for preservation. - Microplastics were identified in bottom sediments of Lake Ontario. Their burial could result in microplastics preservation in the future rock record

  6. Cumulative history recorded in the depth distribution of radiocesium in sediments deposited on a sandbar

    International Nuclear Information System (INIS)

    Tanaka, Kazuya; Kondo, Hiroaki; Sakaguchi, Aya; Takahashi, Yoshio

    2015-01-01

    We collected sediments deposited on a sandbar from the surface to 20 cm in depth in the Abukuma River to clarify the history of radiocesium derived from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. We analyzed the "1"3"7Cs concentration in the sediments from size-fractioned samples as well as bulk samples. The depth distribution of "1"3"7Cs showed the highest concentration in the deepest sediment layer (18–20 cm) studied, which indicates that sediments with a lower "1"3"7Cs concentration were transported and deposited on sediments having a higher "1"3"7Cs concentration. At the same time, the depth distribution suggests a decrease in radioactivity in provenance areas of the sediments. Analysis of the size-fractioned sediments indicated that the three sediment layers at 4–6 cm, 16–18 cm and 18–20 cm intervals had similar size distribution of "1"3"7Cs and grain size composition although the concentration levels of "1"3"7Cs were different according to their bulk concentrations. The size distribution of "1"3"7Cs also supported the possibility that the decrease in "1"3"7Cs concentration in bulk sediments above 18 cm is due to a decrease in the level of radioactivity in the catchment area. A comparison of the size distribution of "1"3"7Cs between the sediment layers above and below 18 cm suggested that the "1"3"7Cs concentration in the transported fine sediment particles decreased more with time than the "1"3"7Cs concentration in the coarse particles, reflecting the selective transport of the finer particles. The results of this study demonstrated that sediment layers deposited on a sandbar retained the cumulative history of the fluvial transport of radiocesium after the FDNPP accident. - Highlights: • We investigated the history of "1"3"7Cs recorded in sediments in the Abukuma River. • "1"3"7Cs concentration was the highest in the deepest sediment layer studied. • The depth distribution suggests a decrease in radioactivity in

  7. The preglacial sediment record of Lake Ladoga, Russia - first results from a seismic survey and sediment coring in 2013

    Science.gov (United States)

    Melles, Martin; Krastel, Sebastian; Fedorov, Grigory; Subetto, Dmitry A.; Savelieva, Larisa A.; Andreev, Andrej; Wagner, Bernd

    2014-05-01

    The new German-Russian project PLOT (Paleolimnological Transect) aims at investigating the Late Quaternary climatic and environmental history along a more than 6000 km long longitudinal transect crossing northern Eurasia. Special emphasis is put on the preglacial history. For this purpose shallow and deep seismic surveys shall be carried out on five lakes, which potentially host preglacial sediment records, followed by sediment coring based on the results of the seismic campaigns. The well-studied Lake El'gygytgyn represents the eastern-most location of the transect and acts as reference site. Within the scope of a pilot phase for the PLOT project, funded by the German Federal Ministry of Education and Research, we were able to investigate Lake Ladoga, which is located close to St. Petersburg at the western end of the transect. Lake Ladoga is the largest lake in Europe, covering an area of almost 18.000 km2. The modern sedimentation as well as the late glacial and Holocene history of the lake were already studied in detail over the past decades. The older, preglacial lake history, however, is only rudimentary known from a core transect drilled in the southern lake in the 1930th. The cores of up to about 60 m length were only briefly described and are not existing any more. The results from these cores, known from unpublished reports only, suggest the existence of marine sediments of presumably Eemian age, representing a time when Lake Lagoga was part of a precursor of the Baltic Sea, which had a connection via Ladoga and Onega Lakes to the White Sea and further to the Arctic Ocean. In late August/early September 2013 we carried out a seismic survey on Lake Ladoga using a Mini-GI-Gun and a 32-channel seismic streamer. In total, 1500 km of seismic profiles were measured, covering most parts of the lake. The seismic lines typically show acoustically well stratified Holocene muds overlaying rather transparent postglacial varves. These sediment successions can reach

  8. Holocene rainfall runoff in the central Ethiopian highlands and evolution of the River Nile drainage system as revealed from a sediment record from Lake Dendi

    Science.gov (United States)

    Wagner, Bernd; Wennrich, Volker; Viehberg, Finn; Junginger, Annett; Kolvenbach, Anne; Rethemeyer, Janet; Schaebitz, Frank; Schmiedl, Gerhard

    2018-04-01

    A 12 m long sediment sequence was recovered from the eastern Dendi Crater lake, located on the central Ethiopian Plateau and in the region of the Blue Nile headwaters. 24 AMS radiocarbon dates from bulk organic carbon samples indicate that the sediment sequence spans the last ca. 12 cal kyr BP. Sedimentological and geochemical data from the sediment sequence that were combined with initial diatom information show only moderate change in precipitation and catchment runoff during that period, probably due to the elevated location of the study region in the Ethiopian highlands. Less humid conditions prevailed during the Younger Dryas (YD). After the return to full humid conditions of the African Humid Period (AHP), a 2 m thick tephra layer, probably originating from an eruption of the Wenchi crater 12 km to the west of the lake, was deposited at 10.2 cal kyr BP. Subsequently, single thin horizons of high clastic matter imply that short spells of dry conditions and significantly increased rainfall, respectively, superimpose the generally humid conditions. The end of the AHP is rather gradual and precedes relatively stable and less humid conditions around 3.9 cal kyr BP. Subsequently, slightly increasing catchment runoff led to sediment redeposition, increasing nutrient supply, and highest trophic states in the lake until 1.5 cal kyr BP. A highly variable increase in clastic matter indicates fluctuating and increasing catchment runoff over the last 1500 years. The data from Lake Dendi show, in concert with other records from the Nile catchment and the Eastern Mediterranean Sea (EMS), that the Blue Nile discharge was relatively high between ca. 10.0 and 8.7 cal kyr BP. Subsequent aridification peaked with some regional differences between ca. 4.0 and 2.6 cal kyr BP. Higher discharge in the Blue Nile hydraulic regime after 2.6 cal kyr BP is probably triggered by more local increase in rainfall, which is tentatively caused by a change in the influence of the Indian Ocean

  9. Eruptive history and magmatic stability of Erebus volcano, Antarctica: Insights from englacial tephra

    Science.gov (United States)

    Iverson, N. A.; Kyle, P. R.; Dunbar, N. W.; Pearce, N. J.

    2012-12-01

    Erebus is the most active volcano in Antarctica and hosts a persistent convecting and degassing phonolite lava lake in its summit crater. Small Strombolian eruptions occasionally eject volcanic bombs onto the crater rim and floor. 40 years of observations, during the austral summer, show that ash eruptions are rare, but extensive records of small tephra (volcanic ash) layers are found embedded in ablating blue ice areas on the flanks of the volcano. Most tephra are deposited within 15km of the summit, although 3 Erebus phonolite tephra have been located over 200km away. The tephra provide a stratigraphic eruptive sequence of Erebus and gives insight into its explosive history. There is very little age control on the eruptions but based on their phonolitic composition they likely span the past 10-40ka. SEM images and Image Particle Analysis (IPA) of tephra were used to determine shard morphology and shape parameters, respectively. The tephra layers characterized by Pele's hair, glass spheres and budding ash are interpreted to be from Strombolian eruptions. In contrast, layers that are dominated by chemical pitting, quenched textures, mossy and adhering particles are mostly likely from phreatomagmatic eruptions. IPA parameters are characterized by rectangularity, compactness, elongation and circularity. Strombolian particles have larger elongation and circularity values exhibited by their stretched and irregular shape and lower rectangularity and compactness values. Phreatomagmatic tephra are more blocky and have higher rectangularity and compactness values and lower elongation and circularity values than Strombolian particles. Based on imagery, many Erebus tephra layers appear to contain a mixture of Strombolian and phreatomagmatic fragments. These mixed eruptions would likely start as phreatomagmatic and transition into magmatic Strombolian eruptions as the water source is exhausted. Major and trace element analyses of the glass shards were measured by electron

  10. An Overview of Sediment Organic Matter Records of Human Eutrophication in the Laurentian Great Lakes Region

    Energy Technology Data Exchange (ETDEWEB)

    Meyers, Philip A. [University of Michigan, Department of Geological Sciences (United States)], E-mail: pameyers@umich.ed

    2006-12-15

    The isotopic and molecular compositions of organic matter buried in lake sediments provide information that helps to reconstruct past environmental conditions and to assess impacts of humans on local ecosystems. This overview of sedimentary records from the North American Great Lakes region describes examples of applications of organic geochemistry to paleolimnological reconstructions. These lakes experienced a succession of human-induced environmental changes that started after completion of the Erie Canal in 1825. Agricultural deforestation in the mid-nineteenth century released soil nutrients that increased algal productivity and caused an associated increase in algal biomarkers in sediment records. Eutrophication that accompanied magnified delivery of municipal nutrients to the lakes in the 1960s and 1970s created excursions to less negative {delta}{sup 13}C values in sediment organic matter. Increased organic carbon mass accumulation rates mirror the isotopic evidence of eutrophication in the Great Lakes.

  11. Elemental signature of terrigenous sediment runoff as recorded in coastal salt ponds: US Virgin Islands

    International Nuclear Information System (INIS)

    Larson, Rebekka A.; Brooks, Gregg R.; Devine, Barry; Schwing, Patrick T.; Holmes, Charles W.; Jilbert, Tom; Reichart, Gert-Jan

    2015-01-01

    A high-resolution, multi-proxy approach is utilized on mm- to cm-scale laminated coastal salt pond sediments from St. John, U.S. Virgin Islands, to determine: (1) the sedimentological signature of depositional events/processes, (2) link this sedimentological signature with known depositional events/processes in the historical (past ∼100 years) record; and, (3) project back into the recent geologic past (past ∼1400 years) to investigate the natural variability of depositional events/processes. High-resolution, short-lived radioisotope geochronology ("2"1"0Pb, "1"3"7Cs, "7Be) combined with high-resolution elemental scanning techniques (scanning XRF and scanning LA-ICP-MS) allows for the direct comparison of well-preserved salt pond deposits to historical records of depositional events (e.g., runoff/rainfall, tropical cyclones, tsunamis) to identify the sedimentary signature of each type of event. There is a robust sedimentary record of terrigenous sediment runoff linked to the frequency of rainfall events that exceed a threshold of ∼12 mm/day (minimum to mobilize and transport sediment) for study sites. This is manifested in the sedimentary record as increases in terrigenous indicator elements (%Al, %Fe, %Ti, %Si), which agree well with rainfall records over the past ∼50 years. Variability in the sedimentary record over the past ∼100 years reflects decadal-scale fluctuations between periods of increased frequency of rainfall events, and decreased frequency of rainfall events. Dm-scale variability in terrigenous indicator elements over the past ∼1400 years represents the natural system variability on a decadal–centennial scale, and provides a high-resolution, long-term baseline of natural variability of rainfall/runoff events. A period of increased terrigenous sediment delivery during the 1700s and 1800s likely indicates increased erosion in response to anthropogenic activities associated with the island’s plantation era, and perhaps increased

  12. Nitrogen isotopes in bulk marine sediment: linking seafloor observations with subseafloor records

    Directory of Open Access Journals (Sweden)

    J.-E. Tesdal

    2013-01-01

    Full Text Available The stable isotopes of nitrogen offer a unique perspective on changes in the nitrogen cycle, past and present. However, the presence of multiple forms of nitrogen in marine sediments can complicate the interpretation of bulk nitrogen isotope measurements. Although the large-scale global patterns of seafloor δ15N have been shown to match process-based expectations, small-scale heterogeneity on the seafloor, or alterations of isotopic signals during translation into the subseafloor record, could obscure the primary signals. Here, a public database of nitrogen isotope measurements is described, including both seafloor and subseafloor sediment samples ranging in age from modern to the Pliocene, and used to assess these uncertainties. In general, good agreement is observed between neighbouring seafloor sites within a 100 km radius, with 85% showing differences of < 1‰. There is also a good correlation between the δ15N of the shallowest (< 5 ka subseafloor sediments and neighbouring seafloor sites within a 100 km radius (R2 = 0.83, which suggests a reliable translation of sediments into the buried sediment record. Meanwhile, gradual δ15N decreases over multiple glacial–interglacial cycles appear to reflect post-depositional alteration in records from the deep sea (below 2000 m. We suggest a simple conceptual model to explain these 100-kyr-timescale changes in well-oxygenated, slowly accumulating sediments, which calls on differential loss rates for pools of organic N with different δ15N. We conclude that bulk sedimentary nitrogen isotope records are reliable monitors of past changes in the marine nitrogen cycle at most locations, and could be further improved with a better understanding of systematic post-depositional alteration. Furthermore, geochemical or environmental criteria should be developed in order to effectively identify problematic locations and to account for

  13. Historical record of mercury contamination in sediments from the Babeni Reservoir in the Olt River, Romania.

    Science.gov (United States)

    Bravo, Andrea Garcia; Loizeau, Jean-Luc; Ancey, Lydie; Ungureanu, Viorel Gheorghe; Dominik, Janusz

    2009-08-01

    Mercury (Hg) is a ubiquitous and hazardous contaminant in the aquatic environment showing a strong biomagnification effect along the food chain. The most common transfer path of Hg to humans is contaminated fish consumption. In severely exposed humans, Hg poisoning may lead to damage in the central nervous system. Thus, it is important to examine current and past contamination levels of Hg in aquatic milieu. The Olt River is the largest Romanian tributary of the Danube River. The use of Hg as an electrode in a chlor-alkali plant contributed to the contamination of the aquatic environment in the Rm Valcea region. The purpose of this study was to compare the current state of Hg contamination with the past contamination using a historical record obtained from a dated sediment core from one of the Olt River reservoirs (Babeni) located downstream from the chlor-alkali plant. To our knowledge, no published data on Hg contamination in this region are available. The Babeni Reservoir was selected for this study because it is situated downstream from the chlor-alkali plant, whilst the other reservoirs only retain the pollutants coming from the upstream part of the watershed. Preliminary analyses (unpublished) showed high Hg concentrations in the surface sediment of the Babeni Reservoir. One core was taken in the upstream Valcea Reservoir to provide a local background level of Hg concentrations in sediments. Sediment texture was uniform in the cores from both reservoirs. Laminated sediment structure, without any obvious discontinuities, was observed. Hg concentrations in the sediment core from the Valcea Reservoir were low and constant (0.01-0.08 mg/kg). In Babeni Reservoir sediments, Hg concentrations were very high in the deeper core section (up to 45 mg/kg in the longest core) and decreased to lower concentrations toward the top of the cores (1.3-2.4 mg/kg). This decrease probably reflects technological progress in control of emissions from the Hg-cell-based chlor

  14. Marine sediments and Beryllium-10 record of the geomagnetic moment variations during the Brunhes period.

    Science.gov (United States)

    Ménabréaz, Lucie; Thouveny, Nicolas; Bourlès, Didier; Demory, François

    2010-05-01

    Over millennial time scales, the atmospheric production of the cosmonuclid 10Be (half-life 1.387 ± 0.012 Ma [Shmeleff et al., 2009; Korschinek et al., 2009]) is modulated by the geomagnetic field strength, following a negative power law (e.g. Lal, 1988; Masarik and Beer, 2009). With respect to paleomagnetic reconstructions, 10Be-derived paleointensity records can therefore constitute an alternative, global and independent reading of the dipole moment variations. During the last years, efforts have been made to extract a geomagnetic signal from single and stacked 10Be records in natural archives such as ice and marine sediments (e.g. Carcaillet et al., 2004; Christl et al., 2007; Muscheler et al., 2005). In marine sediments, the 10Be concentration results from complex interplay of several processes: cosmogenic production, adsorption on sediment particles, redistribution by fluviatile and oceanic transport, and deposition. Therefore, a correction procedure is required to consider both sediment redistribution and enhanced scavenging, which can alter the primary signatures. To reconstruct the succession of field intensity lows accompanying excursions during the Brunhes chron, we investigated authigenic 10Be/9Be record of marine sequences also studied for paleomagnetism and oxygen isotopes. Mid and low latitude sites were preferred in order to benefit from the most efficient modulation by the magnetospheric shielding. We present a high resolution authigenic 10Be/9Be record of the last 50 ka recovered from the Portuguese Margin, that deciphers the cosmonuclide 10Be overproduction created by the geomagnetic dipole low associated with the Laschamp excursion. This record is compared to other proxy records of the geomagnetic field variations for the same time interval: (1) the relative paleointensity (RPI) reconstructed from the same sediments and the GLOPIS-75 record (Laj et al., 2004), (2) the absolute VDM record based on absolute paleointensities measured on lava flows

  15. Anthropogenic effects on sediment quality offshore southwestern Taiwan: Assessing the sediment core geochemical record

    Digital Repository Service at National Institute of Oceanography (India)

    Selvaraj, K.; Parthiban, G.; Chen, C.T.A.; Lou, J.Y.

    -Fernández, A.C., Páez-Osuna, F., Urrutia-Fucugauchi, J., Preda, M., Rehault, I., 2004. Historical trace metal fluxes in the Mexico City Metropolitan Zone as evidenced by a sedimentary record from the Espejo de los Lirios lake. Journal of Environmental...

  16. Modulation of glacier ablation by tephra coverage from Eyjafjallajökull and Grímsvötn volcanoes, Iceland: an automated field experiment

    Science.gov (United States)

    Möller, Rebecca; Möller, Marco; Kukla, Peter A.; Schneider, Christoph

    2018-01-01

    We report results from a field experiment investigating the influence of volcanic tephra coverage on glacier ablation. These influences are known to be significantly different from those of moraine debris on glaciers due to the contrasting grain size distribution and thermal conductivity. Thus far, the influences of tephra deposits on glacier ablation have rarely been studied. For the experiment, artificial plots of two different tephra types from Eyjafjallajökull and Grímsvötn volcanoes were installed on a snow-covered glacier surface of Vatnajökull ice cap, Iceland. Snow-surface lowering and atmospheric conditions were monitored in summer 2015 and compared to a tephra-free reference site. For each of the two volcanic tephra types, three plots of variable thickness ( ˜ 1.5, ˜ 8.5 and ˜ 80 mm) were monitored. After limiting the records to a period of reliable measurements, a 50-day data set of hourly records was obtained, which can be downloaded from the Pangaea data repository (pangaea.de" target="_blank">https://www.pangaea.de; doi:10.1594/PANGAEA.876656). The experiment shows a substantial increase in snow-surface lowering rates under the ˜ 1.5 and ˜ 8.5 mm tephra plots when compared to uncovered conditions. Under the thick tephra cover some insulating effects could be observed. These results are in contrast to other studies which depicted insulating effects for much thinner tephra coverage on bare-ice glacier surfaces. Differences between the influences of the two different petrological types of tephra exist but are negligible compared to the effect of tephra coverage overall.

  17. Historical trends of organochlorine pesticides (OCPs) recorded in sediments across the Tibetan Plateau.

    Science.gov (United States)

    Yang, Ruiqiang; Xie, Ting; Yang, Handong; Turner, Simon; Wu, Guangjian

    2018-02-01

    Sediment cores from four lakes across the Tibetan Plateau were used as natural archives to study the time trends of organochlorine pesticides (OCPs). The total concentrations of dichlorodiphenyltrichloroethane (ΣDDT) and hexachlorocyclohexane isomers (ΣHCH) were in the range of 0.04-1.61 and 0.08-1.88 ng/g based on dry weight (dw), while the input fluxes were in the range of 0.3-236 and 0.7-295 pg/cm 2 /y in the core sediments, respectively. The input fluxes of ΣDDT and ΣHCH generally peaked in sediment layers corresponding to the 1970s-1990s and peaked in top sediment layers. The ratio of α/γ-HCH decreased in the top layer sediments, implying that the contribution of lindane (pure γ-HCH) has been increasing in recent years. In addition, the ratio of o,p'-DDT/p,p'-DDT increased significantly over the last 15-20 years, suggesting that dicofol (characterized by high ratio of o,p'-DDT/p,p'-DDT about 7.0) has recently become a relatively more important source of DDT compared to technical DDT itself. The time trends of OCPs recorded in lake sediments examined the impact on such remote alpine regions by human activities.

  18. Geochemical record of Holocene to Recent sedimentation on the Western Indus continental shelf, Arabian Sea

    Science.gov (United States)

    Limmer, David R.; BöNing, Philipp; Giosan, Liviu; Ponton, Camilo; KöHler, Cornelia M.; Cooper, Matthew J.; Tabrez, Ali R.; Clift, Peter D.

    2012-01-01

    We present a multiproxy geochemical analysis of two cores recovered from the Indus Shelf spanning the Early Holocene to Recent (<14 ka). Indus-23 is located close to the modern Indus River, while Indus-10 is positioned ˜100 km further west. The Holocene transgression at Indus-10 was over a surface that was strongly weathered during the last glacial sea level lowstand. Lower Holocene sediments at Indus-10 have higherɛNdvalues compared to those at the river mouth indicating some sediment supply from the Makran coast, either during the deposition or via reworking of older sediments outcropping on the shelf. Sediment transport from Makran occurred during transgressive intervals when sea level crossed the mid shelf. The sediment flux from non-Indus sources to Indus-10 peaked between 11 ka and 8 ka. A hiatus at Indus-23 from 8 ka until 1.3 ka indicates non-deposition or erosion of existing Indus Shelf sequences. HigherɛNdvalues seen on the shelf compared to the delta imply reworking of older delta sediments in building Holocene clinoforms. Chemical Index of Alteration (CIA), Mg/Al and Sr isotopes are all affected by erosion of detrital carbonate, which reduced through the Holocene. K/Al data suggest that silicate weathering peaked ca. 4-6 ka and was higher at Indus-10 compared to Indus-23. Fine-grained sediments that make up the shelf have geochemical signatures that are different from the coarser grained bulk sediments measured in the delta plain. The Indus Shelf data highlight the complexity of reconstructing records of continental erosion and provenance in marine settings.

  19. Diverse plant and animal genetic records from Holocene and Pleistocene sediments

    DEFF Research Database (Denmark)

    Willerslev, E.; Hansen, Anders J.; Binladen, J.

    2003-01-01

    Genetic analyses of permafrost and temperate sediments reveal that plant and animal DNA may be preserved for long periods, even in the absence of obvious macrofossils. In Siberia, five permafrost cores ranging from 400,000 to 10,000 years old contained at least 19 different plant taxa, including...... the oldest authenticated ancient DNA sequences known, and megafaunal sequences including mammoth, bison, and horse. The genetic data record a number of dramatic changes in the taxonomic diversity and composition of Beringian vegetation and fauna. Temperate cave sediments in New Zealand also yielded DNA...

  20. Sedimentation influx and volcanic interactions in the Fuji Five Lakes: implications for paleoseismological records

    Science.gov (United States)

    Lamair, Laura; Hubert-Ferrari, Aurélia; Yamamoto, Shinya; El Ouahabi, Meriam; Garrett, Ed; Shishikura, Masanobu; Schmidt, Sabine; Boes, Evelien; Obrochta, Stephen; Nakamura, Atsunori; Miyairi, Yosuke; Yokoyama, Yusuke; De Batist, Marc; Heyvaert, Vanessa M. A.

    2017-04-01

    The Fuji Fives Lakes are located at the foot of Mount Fuji volcano close to the triple junction, where the North American Plate, the Eurasian plate and the Philippine Sea Plate meet. These lakes are ideally situated to study Mount Fuji volcanism and the interaction between volcanism, changes in lake sedimentation rates and the ability of lakes to record paleoearthquakes. Here, we present newly acquired geological data of Lake Yamanaka and Lake Motosu, including seismic reflection profiles, gravity and piston cores. These two lakes and their respective watersheds were affected by several eruptions of Mount Fuji. Lake Yamanaka, a very shallow lake (max. depth 14 m), was heavily impacted by the scoria fall-out of the A.D. 1707 Hoei eruption of Mount Fuji. A detailed investigation of the effect of the Hoei eruption was conducted on short gravity cores, using high resolution XRD, C/N and 210Pb/137Cs analyses. The preliminary results suggest that the sedimentation rate of Lake Yamanaka drastically reduced after the Hoei eruption, followed by an increase until the present day. Similarly, lacustrine sedimentation in Lake Motosu (max. depth 122 m) was disturbed by Mount Fuji volcanism at a larger scale. The watershed of Lake Motosu was impacted by several lava flows and scoria cones. For example, the Omuro scoria cone reduced the catchment size of Lake Motosu and modified its physiography. The related scoria fall out covered an extensive part of the lake catchment and reduced terrigenous sedimentary influx to Lake Motosu. Within the deep basin of Lake Motosu, seismic reflection data shows two different periods that are distinguished by a major change in the dominant sedimentary processes. During the first period, sublacustrine landslides and turbidity currents were the dominant sedimentation processes. During the second one, the seismic stratigraphy evidences only deposition of numerous turbidites interrupting the hemipelagic sedimentation. Changes in sedimentary processes

  1. Best-practice checklists for tephra collection, analysis and reporting - a draft consensus from the Tephra 2014 workshop

    Science.gov (United States)

    Wallace, K.; Bursik, M. I.; Kuehn, S. C.

    2015-12-01

    The Tephra 2014 Workshop (3-7 August 2014) discussed major developments, best practices, future directions, and critical needs in tephra studies from both volcanological and tephrochronological perspectives. In a consensus-seeking session held at the end of the workshop, the international group of over 70 tephra scientists focused on two complementary themes: (A) the need for common best practices in tephra data collection and reporting among different scientific disciplines, and (B) the need to establish common, accessible mechanisms for tephra data archiving and retrieval. Tephra is the focus of a wide range of research in volcanology, petrology, tephrochronology and tephrostratigraphy (with applications in studies of environmental/climate change, surface processes, paleolimnology, etc.), ash dispersion and fallout modeling, and archaeology, paleoanthropology, and human origins. Researchers in each field have specific objectives that may or may not overlap. The focus on best practices is a first step towards standardized protocols for the collection, analysis and reporting of tephra data across and within disciplines. Such uniformity will facilitate the development and population of useful tephra databases. Current initiatives include the development of best practice checklists as a starting point for ensuring uniformity and completeness. The goals of the checklists are to: 1) ensure consistency among tephra scientists, regardless of research focus, 2) provide basic, comprehensible, metadata requirements, especially those who collect tephra as a peripheral part of their research, 3) help train students, and 4) help journal editors to know which essential metadata should be included in published works. Consistency in tephra sample collection, analysis, and reporting attained by use of these checklists should ultimately aid in improving correlation of tephras across geographically large areas, and facilitate collaborative tephra research. Current and future

  2. Deciphering long-term records of natural variability and human impact as recorded in lake sediments: a palaeolimnological puzzle

    DEFF Research Database (Denmark)

    Mills, Keely; Schillereff, Daniel; Saulnier-Talbot, Émilie

    2017-01-01

    that is particularly acute when considering management options for aquatic ecosystems. The duration and timing of human impacts on lake systems varies geographically, with some regions of the world (such as Africa and South America) having a longer legacy of human impact than others (e.g., New Zealand). A wide array...... of techniques (biological, chemical, physical and statistical) is available to palaeolimnologists to allow the deciphering of complex sedimentary records. Lake sediments are an important archive of how drivers have changed through time, and how these impacts manifest in lake systems. With a paucity of ‘real...

  3. Stratigraphic and compositional complexities of the late Quaternary Lethe tephra in South-central Alaska

    Science.gov (United States)

    Riehle, J.R.; Ager, T.A.; Reger, R.D.; Pinney, D.S.; Kaufman, D.S.

    2008-01-01

    Recently discovered Lethe tephra has been proposed as a latest Pleistocene marker bed in Bristol Bay lowland NE to the Cook Inlet region, Alaska, on the basis of correlations involving a single "Lethe average" glass composition. Type deposits in the Valley of Ten Thousand Smokes, however, are chemically heterogeneous-individual lapilli as well as aggregate ash deposits have glass compositions that range from the average mode to much higher SiO2 and K2O. Moreover, a lake-sediment core from the Cook Inlet region contains one ash deposit similar to "Lethe average" and other, closely underlying deposits that resemble a mixture of the average mode and high-Si high-K mode of proximal deposits. Synthesis of previously published radiocarbon ages indicates a major eruption mainly of "Lethe average" mode about 13,000 14C yr BP. As many as six deposits in the Cook Inlet region-five chiefly "Lethe average" mode-range from about 13,000 to 15-16,000 14C yr BP, and an early Holocene deposit in the Bristol Bay lowland extends the minimum age range of Lethe tephra throughout this region to 8000 14C yr BP. Because of the appearance of "Lethe average" composition in multiple deposits spanning thousands of years, we urge caution when using a Lethe-like composition as a basis for inferring a latest Pleistocene age of a tephra deposit in south-central Alaska. Linear variation plots suggest that magma mixing caused the Lethe heterogeneity; multiple magmas were involved as well in other large pyroclastic eruptions such as Katmai (Alaska) and Rotorua (New Zealand). Lethe is an example of a heterogeneous tephra that may be better compared with other tephras by use of plots of individual analytical points rather than by calculating similarity coefficients based on edited data. ?? 2006 Elsevier Ltd and INQUA.

  4. Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

    Directory of Open Access Journals (Sweden)

    N. Dijkstra

    2018-02-01

    Full Text Available Phosphorus (P concentrations in sediments are frequently used to reconstruct past environmental conditions in freshwater and marine systems, with high values thought to be indicative of a high biological productivity. Recent studies suggest that the post-depositional formation of vivianite, an iron(II-phosphate mineral, might significantly alter trends in P with sediment depth. To assess its importance, we investigate a sediment record from the Bornholm Basin that was retrieved during the Integrated Ocean Drilling Program (IODP Baltic Sea Paleoenvironment Expedition 347 in 2013, consisting of lake sediments overlain by brackish–marine deposits. Combining bulk sediment geochemistry with microanalysis using scanning electron microscope energy dispersive spectroscopy (SEM-EDS and synchrotron-based X-ray absorption spectroscopy (XAS, we demonstrate that vivianite-type minerals rich in manganese and magnesium are present in the lake deposits just below the transition to the brackish–marine sediments (at 11.5 to 12 m sediment depth. In this depth interval, phosphate that diffuses down from the organic-rich, brackish–marine sediments meets porewaters rich in dissolved iron in the lake sediments, resulting in the precipitation of iron(II phosphate. Results from a reactive transport model suggest that the peak in iron(II phosphate originally occurred at the lake–marine transition (9 to 10 m and moved downwards due to changes in the depth of a sulfidization front. However, its current position relative to the lake–marine transition is stable as the vivianite-type minerals and active sulfidization fronts have been spatially separated over time. Experiments in which vivianite was subjected to sulfidic conditions demonstrate that incorporation of manganese or magnesium in vivianite does not affect its susceptibility to sulfide-induced dissolution. Our work highlights that post-depositional formation of iron(II phosphates such as vivianite has

  5. Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

    Science.gov (United States)

    Dijkstra, Nikki; Hagens, Mathilde; Egger, Matthias; Slomp, Caroline P.

    2018-02-01

    Phosphorus (P) concentrations in sediments are frequently used to reconstruct past environmental conditions in freshwater and marine systems, with high values thought to be indicative of a high biological productivity. Recent studies suggest that the post-depositional formation of vivianite, an iron(II)-phosphate mineral, might significantly alter trends in P with sediment depth. To assess its importance, we investigate a sediment record from the Bornholm Basin that was retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013, consisting of lake sediments overlain by brackish-marine deposits. Combining bulk sediment geochemistry with microanalysis using scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and synchrotron-based X-ray absorption spectroscopy (XAS), we demonstrate that vivianite-type minerals rich in manganese and magnesium are present in the lake deposits just below the transition to the brackish-marine sediments (at 11.5 to 12 m sediment depth). In this depth interval, phosphate that diffuses down from the organic-rich, brackish-marine sediments meets porewaters rich in dissolved iron in the lake sediments, resulting in the precipitation of iron(II) phosphate. Results from a reactive transport model suggest that the peak in iron(II) phosphate originally occurred at the lake-marine transition (9 to 10 m) and moved downwards due to changes in the depth of a sulfidization front. However, its current position relative to the lake-marine transition is stable as the vivianite-type minerals and active sulfidization fronts have been spatially separated over time. Experiments in which vivianite was subjected to sulfidic conditions demonstrate that incorporation of manganese or magnesium in vivianite does not affect its susceptibility to sulfide-induced dissolution. Our work highlights that post-depositional formation of iron(II) phosphates such as vivianite has the potential to strongly

  6. Tephra-Producing Eruptions of Holocene Age at Akutan Volcano, Alaska; Frequency, Magnitude, and Hazards

    Science.gov (United States)

    Waythomas, C. F.; Wallace, K. L.; Schwaiger, H.

    2012-12-01

    Aleutian arc volcanoes. Tephra deposits from typical VEI 2 historical eruptions are not well preserved on the island so tephra-fall frequency estimated from stratigraphic studies is underestimated. Akutan Island is home to the largest seafood processing plant in North America and has a workforce of more than one thousand people. Other infrastructure consists of a recently constructed paved airfield on neighboring Akun Island (25 km east of the active vent) and a new boat harbor at the head of Akutan Harbor. Plans to develop greenhouses, tourism, and increased cold storage capacity on Akutan and Akun Islands also are evolving. To support the power demands of the development efforts, The City of Akutan is considering the utilization of geothermal resources on the island that are located in Hot Springs Bay valley northwest of the city. All of the existing and planned infrastructure, water supply, and residential areas are about 12 km downwind (east) of the volcano and are at risk from ash-producing eruptions. The historical eruptive history suggests that VEI 2 eruptions are plausible in the near future and the Holocene tephra-fall record indicates that large eruptions (VEI 4 or larger) occur about every few thousand years. Numerical modeling of tephra fallout based on the record of ash-producing eruptions will be used to improve tephra-fall hazard assessments for the area.

  7. Aeolian particle transport inferred using a ~150-year sediment record from Sayram Lake, arid northwest China

    Directory of Open Access Journals (Sweden)

    Long Ma

    2015-05-01

    Full Text Available We studied sediment cores from Sayram Lake in the Tianshan Mountains of northwest China to evaluate variations in aeolian transport processes over the past ~150 years. Using an end-member modeling algorithm of particle size data, we interpreted end members with a strong bimodal distribution as having been transported by aeolian processes, whereas other end members were interpreted to have been transported by fluvial processes. The aeolian fraction accounted for an average of 27% of the terrigenous components in the core. We used the ratio of aeolian to fluvial content in the Sayram Lake sediments as an index of past intensity of aeolian transport in the Tianshan Mountains. During the interval 1910-1930, the index was high, reflecting the fact that dry climate provided optimal conditions for aeolian dust transport. From 1930-1980, the intensity of aeolian transport was weak. From the 1980s to the 2000s, aeolian transport to Sayram Lake increased. Although climate in northwest China became more humid in the mid-1980s, human activity had by that time altered the impact of climate on the landscape, leading to enhanced surface erosion, which provided more transportable material for dust storms. Comparison of the Lake Sayram sediment record with sediment records from other lakes in the region indicates synchronous intervals of enhanced aeolian transport from 1910 to 1930 and 1980 to 2000.

  8. Tephra from the 1979 soufriere explosive eruption.

    Science.gov (United States)

    Sigurdsson, H

    1982-06-04

    The explosive phase of the 1979 Soufriere eruption produced 37.5 x 10(6) cubic meters (dense-rock equivalent) of tephra, consisting of about 40 percent juvenile basaltic andesite and 60 percent of a nonjuvenile component derived from the fragmentation of the 1971-1972 lava island during phreatomagmatic explosions. The unusually fine grain size, poor sorting, and bimodality of the land deposit are attributed to particle aggregation and the formation of accretionary lapilli in a wet eruption column.

  9. Improvements in the chronology, geochemistry and correlation techniques of tephra in Antarctic ice

    Science.gov (United States)

    Iverson, N. A.; Dunbar, N. W.; McIntosh, W. C.; Pearce, N. J.; Kyle, P. R.

    2013-12-01

    Visible and crypto tephra layers found in West Antarctic ice provide an excellent record of Antarctic volcanism over the past 100ka. Tephra layers are deposited almost instantaneously across wide areas creating horizons that, if found in several locations, provide 'pinning points' to adjust ice time scales that may otherwise be lacking detailed chronology. Individual tephra layers can have distinct chemical fingerprints allowing them to correlate over great distances. Advances in sample preparation, geochemical analyses (major and trace elements) of fine grained tephra and higher precision 40Ar/39Ar dating of young (typically too small to be directly dated by 40Ar/39Ar method, making it very important to geochemically correlate these layers to proximal deposits where more and larger feldspar can be sampled. The correlation of WDC06A-2767.117 to the coarse, proximal BIT-152 provides one such link. The New Mexico Geochronology Research Lab (NMGRL) has two new multi-collector ARGUS VI mass spectrometers that can provide single crystal laser fusion ages that are approximately an order of magnitude more precise than the previous determinations. With these advancements in analytical technology, we hope to improve precision on 'pinning points' in the deep ice cores where annual layer counting becomes less precise.

  10. The Disruption of Tephra Fall Deposits by Basaltic Lava Flows

    Science.gov (United States)

    Brown, R. J.; Thordarson, T.; Self, S.; Blake, S.

    2010-12-01

    Complex physical and stratigraphic relationships between lava and proximal tephra fall deposits around vents of the Roza Member in the Columbia River Basalt Province, (CRBP), USA, illustrate how basaltic lavas can disrupt, dissect (spatially and temporally) and alter tephra fall deposits. Thin pahoehoe lobes and sheet lobes occur intercalated with tephra deposits and provide evidence for synchronous effusive and explosive activity. Tephra that accumulated on the tops of inflating pahoehoe flows became disrupted by tumuli, which dissected the overlying sheet into a series of mounds. During inflation of subjacent tumuli tephra percolated down into the clefts and rubble at the top of the lava, and in some cases came into contact with lava hot enough to thermally alter it. Lava breakouts from the tumuli intruded up through the overlying tephra deposit and fed pahoehoe flows that spread across the surface of the aggrading tephra fall deposit. Non-welded scoria fall deposits were compacted and welded to a depth of ~50 cm underneath thick sheet lobes. These processes, deduced from the field relationships, have resulted in considerable stratigraphic complexity in proximal regions. We also demonstrate that, when the advance of lava and the fallout of tephra are synchronous, the contacts of some tephra sheets can be diachronous across their extent. The net effect is to reduce the usefulness of pyroclastic deposits in reconstructing eruption dynamics.

  11. Historical atmospheric pollution trends in Southeast Asia inferred from lake sediment records.

    Science.gov (United States)

    Engels, S; Fong, L S R Z; Chen, Q; Leng, M J; McGowan, S; Idris, M; Rose, N L; Ruslan, M S; Taylor, D; Yang, H

    2018-04-01

    Fossil fuel combustion leads to increased levels of air pollution, which negatively affects human health as well as the environment. Documented data for Southeast Asia (SEA) show a strong increase in fossil fuel consumption since 1980, but information on coal and oil combustion before 1980 is not widely available. Spheroidal carbonaceous particles (SCPs) and heavy metals, such as mercury (Hg), are emitted as by-products of fossil fuel combustion and may accumulate in sediments following atmospheric fallout. Here we use sediment SCP and Hg records from several freshwater lentic ecosystems in SEA (Malaysia, Philippines, Singapore) to reconstruct long-term, region-wide variations in levels of these two key atmospheric pollution indicators. The age-depth models of Philippine sediment cores do not reach back far enough to date first SCP presence, but single SCP occurrences are first observed between 1925 and 1950 for a Malaysian site. Increasing SCP flux is observed at our sites from 1960 onward, although individual sites show minor differences in trends. SCP fluxes show a general decline after 2000 at each of our study sites. While the records show broadly similar temporal trends across SEA, absolute SCP fluxes differ between sites, with a record from Malaysia showing SCP fluxes that are two orders of magnitude lower than records from the Philippines. Similar trends in records from China and Japan represent the emergence of atmospheric pollution as a broadly-based inter-region environmental problem during the 20th century. Hg fluxes were relatively stable from the second half of the 20th century onward. As catchment soils are also contaminated with atmospheric Hg, future soil erosion can be expected to lead to enhanced Hg flux into surface waters. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Correlation between historical cyclones and the sedimentary record obtained from gammaspectrometrically dated sediment cores from the shelf off Bangladesh

    International Nuclear Information System (INIS)

    Suckow, A.; Michels, K.; Kudrass, H.R.; Kottke, B.

    1999-01-01

    This paper presents results from a study related to storm history and sediment balance off Bangladesh. Sediment cores and high-resolution seismic and bathymetric records were obtained during two cruises of research vessel 'Sonne' in 1994 (So93) and 1997 (So126). Sediments were dated using the natural and fallout radionuclides 137 Cs, 210 Pb, 214 Pb, 214 Bi and 228 Ra, measured by gamma spectrometry on freeze-dried samples

  13. A 150 kyr-long hydroclimate record from Southern California using Searles Lake sediments: initial findings

    Science.gov (United States)

    Stroup, J. S.; Olson, K. J.; McGee, D.; Lowenstein, T. K.; Smoot, J. P.; Janick, J. J.; Lund, S.; Peaple, M.; Chen, C. Y.; Feakins, S. J.; Litwin, R.

    2017-12-01

    Over decadal to millennial scales, the southwestern U.S has experienced large shifts in hydroclimate ranging from pluvial conditions to extreme droughts. Direct observations, modeling and proxy data suggest precipitation amount and distribution are controlled by multiple factors including the position of the Hadley Cell, strength of the Aleutian Low and North Pacific High, ENSO and the path of winter storm tracks. Sediment records from closed basin lakes provide a means for assessing how hydrologic conditions have responded to past climate changes; however, long (>50 ka) paleoclimate records from lakes are rare and high-resolution age models are challenging to obtain. Searles Lake, in southeastern California, contains a sedimentary record that spans from the Holocene to the Pliocene at high resolution. Previous drill core studies from the basin used stratigraphy and sediment mineralogy to interpret paleoenvironmental changes and have demonstrated that the lake's sediments are able to be precisely dated. These results provide a strong foundation for new high-resolution investigations of the lake sediments. In January 2017, our group collected a new 80 m-long core with the aim of reconstructing hydrologic changes over the last 150 ka at millennial or better resolution. The core was split at the National Lacustrine Core Facility (LacCore) in June. The core contains alternating evaporite layers and finely laminated muds which likely indicate times of dryer and wetter conditions. Despite the challenge of alternating lithologies, core recovery and quality are extremely high. Here, we will present our initial chronological and stratigraphic findings. The core record will be dated using a combination of U/Th, 14C and magnetostratigraphy. We will compare our initial stratigraphic description to the existing Searles Lake literature as well as other records from the region, such as data from Devils Hole. These results provide the framework upon which we will develop detailed

  14. Radiocarbon dating of sediment cores from Hachinohe, the Kamikita Plain

    International Nuclear Information System (INIS)

    Hitoki, Eri; Nakamura, Toshio; Matsumoto, Yui; Tsuji, Sei-ichiro; Fujine, Hisashi

    2013-01-01

    We investigated stratigraphy and chronology by analyses of Holocene sediments and radiocarbon dating of sediment cores from the Kamikita Plain. On the Kamikita Plain, which faces the Pacific coast of Northeast Japan, marine and fluvial terraces covered with tephras derived from Towada and Hakkoda volcanoes are well developed. We clarified that Towada Chuseri tephra and fluvial deposits consisted of volcanic sediments influenced an alluvial depositional system in the Kamikita Plain after a maximum of the Jomon Transgression. (author)

  15. Detection of Lateglacial distal tephra layers in the Netherlands

    NARCIS (Netherlands)

    Davies, S.M.; Hoek, W.Z.; Bohncke, S.J.P.; Lowe, J.; Pyne O'Donnle, S.; Turney, C.S.M.

    2005-01-01

    Three distal tephra layers or cryptotephras have been detected within a sedimentary sequence from the Netherlands that spans the last glacial-interglacial transition. Geochemical analyses identify one as the Vedde Ash, which represents the southernmost discovery of this mid-Younger Dryas tephra so

  16. Ratio of basin lag times for runoff and sediment yield processes recorded in various environments

    Directory of Open Access Journals (Sweden)

    K. Banasik

    2015-03-01

    Full Text Available River basin lag time (LAG, defined as the elapsed time between the occurrence of the centroids of the effective rainfall intensity hyetograph and the storm runoff hydrograph, is an important factor in determining the time to peak and the peak value of the instantaneous unit hydrograph (IUH. In the procedure of predicting a sedimentgraph (suspended sediment load as a function of time, the equivalent parameter is the lag time for the sediment yield (LAGs, which is defined as the elapsed time between the occurrence of the centroids of sediment production during a storm event and the observed sedimentgraph at the gauging station. Data of over 150 events recorded in 11 small river catchments (located in Poland, Germany, UK and USA with a drainage area of 0.02 km2 to 82 km2 have been analysed to estimate the ratio of LAGs/LAG. The ratio, in majority of cases was smaller than 1, and decreased with increase of river basin slope. Special attention is given to the data collected in a small agricultural catchment and also during snowmelt periods, which is located in central Poland.

  17. Peruvian sediments as recorders of an evolving hiatus for the last 22 thousand years

    Science.gov (United States)

    Erdem, Zeynep; Schönfeld, Joachim; Glock, Nicolaas; Dengler, Marcus; Mosch, Thomas; Sommer, Stefan; Elger, Judith; Eisenhauer, Anton

    2016-04-01

    The Peruvian continental margin is characterized by the presence of one of the strongest and most distinct Oxygen Minimum Zones (OMZs) in today's oceans. Therefore, it has long been in the focus of oceanographic and geological investigations. Observations indicate that OMZs are expanding in relation with currently changing climate. To advance understanding of the temporal evolution of OMZs and climate change, complete paleoceanographic and palaeoclimatological reconstructions are needed. However, the development of paleoenvironmental scenarios for the period since the Last Glacial Maximum at this region was hampered by a ubiquitous hiatus and short-term interruptions of the stratigraphical record. In the present study, we combined the stratigraphical information from 31 sediment cores from the Peruvian margin located between 3 and 18°S and water depths of 90 to 1300 m within and below today's OMZ, in order to determine the extent of the hiatus and assess the responsible mechanisms. A widespread unconformity and related erosional features, omission surfaces and phosphorites, were observed in sediment cores from the area south of 7°S, depicting a prograding feature on the continental slope from south to north during the deglaciation. Combining recent oceanographic and sedimentological observations, it is inferred that, tide-topography interaction and resulting non-linear internal waves (NLIWs) shape the slope by erosion, carry sediments upslope or downslope and leave widespread phosphoritic lag sediments, while the Peru Chile Undercurrent (PCUC) transports the resuspended sediments southward causing non-deposition. This exceptional sedimentary regime makes the Peruvian margin a modern analogue for such environments. Overall, our compilation of downcore records showed that enhanced bottom currents due to tide-topography interaction were progressively evolving and affected a wider area with the onset of the last deglaciation. Elevated tidal amplitudes and variability

  18. Earth system feedback statistically extracted from the Indian Ocean deep-sea sediments recording Eocene hyperthermals.

    Science.gov (United States)

    Yasukawa, Kazutaka; Nakamura, Kentaro; Fujinaga, Koichiro; Ikehara, Minoru; Kato, Yasuhiro

    2017-09-12

    Multiple transient global warming events occurred during the early Palaeogene. Although these events, called hyperthermals, have been reported from around the globe, geologic records for the Indian Ocean are limited. In addition, the recovery processes from relatively modest hyperthermals are less constrained than those from the severest and well-studied hothouse called the Palaeocene-Eocene Thermal Maximum. In this study, we constructed a new and high-resolution geochemical dataset of deep-sea sediments clearly recording multiple Eocene hyperthermals in the Indian Ocean. We then statistically analysed the high-dimensional data matrix and extracted independent components corresponding to the biogeochemical responses to the hyperthermals. The productivity feedback commonly controls and efficiently sequesters the excess carbon in the recovery phases of the hyperthermals via an enhanced biological pump, regardless of the magnitude of the events. Meanwhile, this negative feedback is independent of nannoplankton assemblage changes generally recognised in relatively large environmental perturbations.

  19. Testing Proposed Correlations Between Olduvai Gorge and Laetoli, Tanzania Using Tephra Composition

    Science.gov (United States)

    McHenry, L. J.

    2006-12-01

    Olduvai Gorge and Laetoli are well-known Plio-Pleistocene archaeological sites located 30 km apart in Tanzania. Both received volcanic input from the nearby Ngorongoro Volcanic Highlands (NVH), and together provide a sedimentary and volcanic record from about 4.3 Ma to the Holocene. Previous researchers have proposed likely temporal correlations between the two sites, using both faunal and volcanic evidence. Direct tephra correlation between these sites could create a regional stratigraphic framework for their fossil and paleoecological records. Here, one of the proposed correlations is tested using geochemical fingerprinting. The fossiliferous Laetolil and Ndolanya beds of Laetoli predate the deposition of the Olduvai Beds, however recent 39Ar/40Ar SCLF age dating has shown potential temporal overlap between the Naibadad (2.23-1.93 +/- 0.02; Mangea, 1993) and Olpiro Beds (2.06-2.01 +/- 0.03; Manega 1993) at Laetoli with the Naabi Ignimbrite (2.029 +/- 0.005 Ma, Walter et al. 1992) and lower Bed I at Olduvai. Both the Naibadad bed and lower Bed I also contain fresh quartz-bearing tephra, which can be used for geochemical correlation. Three Naibadad tuffs and five lower Bed I tuffs (Naabi Ignimbrite, coarse feldspar crystal tuff (CFCT), Tuff IA, and two ignimbrites near Ngorongoro) were analyzed by electron microprobe for phenocryst and glass composition and compared to test for possible correlations. Certain mineralogical features made such a correlation unlikely. None of the lower Bed I tuffs analyzed contain significant plagioclase, which is present in all of the Naibadad tuffs analyzed. One Naibadad tuff has a bimodal glass composition indistinguishable from the CFCT, however the CFCT is rich in hornblende, while this Naibadad tuff contains none. This mineralogical difference highlights the need for mineralogical in addition to glass geochemical data for tephra correlation. Ngorongoro crater is the likely source for the Naibadad and lower Bed I tuffs because it

  20. The record of iceberg roll generated waves from sediments and seismics

    Science.gov (United States)

    Rosser, N. J.; Szczucinski, W.; Strzelecki, M.; Long, A. J.; Norman, E. C.; Dunning, S.; Drewniak, M.

    2013-12-01

    Iceberg-roll tsunamis in coastal settings have been observed to generate significant local waves, that hold potential to be recorded in coastal depositional records. Capturing the past magnitude and frequency of such events remains challenging, hindered by a lack of a good understanding of the nature, recurrence and scale of iceberg rolls, and more specifically those rolls that generate waves. Here we consider the sedimentary evidence for iceberg rolls in West Central Greenland, based upon survey of depositional environments in a range of open and confined coastal environments. We examine both an open 80 km fjord setting, and a series of confined ice-marginal beaches. We combine a detailed interpretation of sediment deposits from shore-normal transects with wider-scale high-resolution terrestrial laser scanning of sediments. Our sites - Vaigat, which separates Disko Island from the Nussuaq Peninsular, and the northern shore of Icefjord - both have a recent history of tsunamis, triggered variously by large rock avalanches, landslides and iceberg rolls. Icebergs in Vaigat and Icefjord are observed to undergo frequent failure and roll, generating - where circumstances permit - nearshore waves of meter-scale. To obtain a more detailed understanding of the likely recurrence of such iceberg roll waves and to consider their influence upon the preserved sedimentary record, we undertook an intensive 2-month monitoring campaign during sea-ice free conditions in summer 2013 to determine the patterns in the location, magnitude, frequency and timing of iceberg roll waves. Innovatively, using microseismic monitoring combined with time-lapse photography and weather monitoring, we derive a first-order model of the occurrence of iceberg roll waves. We then use this to inform our interpretation of deposits in these two environments, and consider the presence and absence of records of iceberg roll deposits in such settings. The study was funded by Polish National Science Centre grant

  1. A Holocene pollen and sediment record of Whangape Harbour, far northern New Zealand

    International Nuclear Information System (INIS)

    Horrocks, M.; Nichol, S.L.; Gregory, M.R.; Creese, R.; Augustinus, P.C.

    2001-01-01

    The sediment record of Whangape Harbour shows that there were significant fluctuations in depositional energy in the harbour during the period from c. >8000 cal. yr BP to some time within the last millenium, and that fluvial influences increased as the harbour infilled. The pollen record (highly discontinuous) from Whangape Harbour indicates that conifer-hardwood forest covered the hills surrounding the harbour during this period. The main canopy conifers were Dacrydium and Prumnopitys taxifolia, with some Libocedrus, Dacrycarpus, and Phyllocladus. Agathis was also present. Common canopy hardwoods were Metrosideros and, in the latter part of the period, Elaeocarpus. Ascarina and Cyathea were abundant in the sub-canopy. Leptospermum grew on disturbed areas fringing the estuary. Marsh or swamp environments probably never developed on a large scale in the harbour. Avicennia, extremely under-represented in the pollen flora, has been present on tidal flats in the harbour since at least c. 2500 cal. yr BP. Large-scale anthropogenic deforestation by burning commenced in the Whangape catchment some time during or since 700-430 cal. yr BP. The associated increase in erosion rates in the catchment resulted in a change towards a sandier sediment regime in the harbour which has continued to the present day. Weinmannia and Ackama, previously rare in the catchment, expanded in remaining forest. (author). 39 refs., 3 figs., 1 tab

  2. Validating the use of embryonic fish otoliths as recorders of sublethal exposure to copper in estuarine sediments

    International Nuclear Information System (INIS)

    Barbee, Nicole C.; Greig, Alan; Swearer, Stephen E.

    2013-01-01

    In this study we explore the use of fish otoliths (‘earbones’) as a tool for detecting exposure to heavy metals in sediments. Because otoliths are metabolically inert and incorporate chemical impurities during growth, they can potentially provide a more permanent record of pollutant exposure history in aquatic environments than soft tissues. To validate this technique we cultured embryos of a native Australian fish, the common Galaxias (Galaxias maculatus), in the laboratory on sediments spiked with copper in a concentration gradient. Our aims were to test whether exposure to copper contaminated sediments is recorded in the otoliths of embryos and determine over what range in concentrations we can detect differences in exposure. We found elevated copper levels in otoliths of embryos exposed to high copper concentrations in sediments, suggesting that otoliths can be used as a tool to track a history of exposure to elevated copper levels in the environment. -- Highlights: •Our aim was to determine if exposure to Cu is recorded in embryonic fish otoliths. •Fish eggs were cultured on Cu-spiked sediments in a gradient of concentrations. •Fish do uptake and incorporate Cu into their otoliths during development. •High sediment Cu concentrations resulted in high otolith Cu concentrations. •With further validation, otoliths could be used to track a history of Cu exposure. -- We use sediments spiked with Cu to examine the uptake of heavy metals into embryonic fish otoliths as a novel tool for tracking pollution exposure history

  3. The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea

    DEFF Research Database (Denmark)

    Pearce, C.; Varhelyi, A.; Wastegård, S.

    2016-01-01

    is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points...

  4. Does Thermal Granulation Drive Tephra Jets?

    Science.gov (United States)

    White, J. D.; Zimanowski, B.; Buettner, R.; Sonder, I.; Dellino, P.

    2011-12-01

    Surtseyan tephra jets, also called cypressoid or cock's tail plumes, comprise a characteristic mixture of ash with bombs travelling roughly ballistic paths that tip the individual fingers of the projecting jet. Jets of similar form but smaller scale are generated by littoral magma-water interactions, confirming the general inference that surtseyan tephra jets are a characteristic product of explosive magma-water interaction, and suggesting that magmatic volatiles play a subsidiary role, if any, in their formation. Surtseyan jets have been inferred to result from both intense fuel-coolant interactions, and from simple boiling of water entrained into rising magma, and little new information has become available to test these two positions since they were clearly developed in the 1980s. Recent experiments in which magma is poured into standing water have produced vigorous jetting of hot water as melt solidifies and undergoes extensive thermal granulation. We present high-resolution hi-speed video of these jets, which we see as having the following origin. As thermal granulation takes place, a fracture network advances into the melt/glass body, and water invading the cracks at the rate of propagation is heated nearly instantaneously. Vapor produced at the contact expands and drives outward through cooled cracks, condensing as it moves to the exterior of the magma body where it is emitted as a jet of hot water. In ocean ridge hydrothermal systems a diffuse crack network inducts cold water, which is heated and expelled in focused jets. Focusing of hot outflow in experiments is inferred to result, as suggested for ridge hydrothermal systems, from thermoelastic closure of cracks near the one(s) feeding the jet. From the cooled products of our experimental runs, we know that thermal contraction produces a network of curved cracks with modal spacing of 1-2 mm, which separate domains of unbroken glass. It is during growth of this crack network that cold water enters, is

  5. Analysis of volcanic tephra as a material of environment

    Science.gov (United States)

    Sitek, J.; Dekan, J.; Fang, X.; Xiaoli, P.; Chmielewská, E.

    2012-10-01

    Tephra is a fragmental material produced by volcanic eruption. Here, volcanic tephra deposit from the northeast of China was used for our study. Samples of unaltered tephra are usually composed of feldspar, glass, pyroxene, and olivine. Moreover, these volcanic alteration products also contain Fe oxides, phylosilicates, sulfates, and amorphous Al-Si-bearing material. Six different samples of tephra obtained were analyzed by Mössbauer spectroscopy. A typical Mössbauer spectrum of tephra consists of magnetic and non-magnetic components (magnetic component represents about 11% and non-magnetic component about 89% of spectral area). According to the structural composition, it may be supposed that the magnetic component can be assigned to titanomagnetite. Non-magnetic components contain two quadrupole doublets (Fe2+ species) and one doublet containing Fe3+. According to the measured values of Mössbauer spectra, the first two doublets are very similar with pyroxene, olivine and the third to phylosilicate, aluminosilicate or iron oxide of FeO type. Recently, volcanic tephra was applied as an ecological substance. Special solution was proposed for tephra utilization, especially for phosphate removal from contaminated water.

  6. Tephra compositions from Late Quaternary volcanoes around the Antarctic Peninsula

    Science.gov (United States)

    Kraus, S.

    2009-12-01

    /Hf ratios lower than N-MORB, all other volcanoes including the Larsen Rift centers display Zr/Hf higher than N-MORB. It is expected that the correlation of the new data with published data from tephra layers found in ice, lake and marine sediment cores will contribute to a better constrained timing of individual climatic events identified in the northern Antarctic Peninsula area. Late Quaternary volcanoes around the northern Antarctic Peninsula.

  7. Stratigraphy and tephra of the Kibish Formation, southwestern Ethiopia.

    Science.gov (United States)

    Brown, Francis H; Fuller, Chad R

    2008-09-01

    The Kibish Formation in southwestern Ethiopia, with an aggregate thickness of approximately 105 m, consists of lacustrine, marginal lacustrine, and deltaic deposits. It is divided into four members numbered I to IV on the basis of erosion surfaces (disconformities) between the strata of each member. It overlies the Mursi and Nkalabong formations, the latter of which is here shown to correlate with the Shungura Formation. Tephra layers in each member allow for secure correlation between geographically separated sections on the basis of the composition of their volcanic glass. Members I, III, and IV of the Kibish Formation appear to have been deposited at the same times as sapropels S7 (197 ka), S4 (104 ka), and S1 (8 ka) in the eastern Mediterranean Sea, respectively. We correlate the KHS Tuff of the Kibish Formation with a >154-kyr-old unnamed tuff in the Konso Formation. Tephra in Member IV may derive from Mount Wenchi, a volcano situated on the divide between the Omo and Blue Nile drainage basins. Thin-bedded sedimentary layers probably represent annual deposition reflecting rapid sedimentation (approximately 30 m/kyr) of parts of the formation. This conclusion is supported by variation in paleomagnetic inclination through a sequence of these layers at KHS. Two fossils of early Homo sapiens (Omo I and Omo II) derive from Member I. Their stratigraphic placement is confirmed by analysis of the KHS Tuff in the lower part of Member II at both fossil sites. The KHS Tuff lies above a disconformity, which itself lies above the fossils at both sites. (40)Ar/(39)Ar dates provide an estimated age of approximately 195 kyr for these fossils. Omo III, a third fossil H. sapiens, probably also derives from Member I of the Kibish Formation and is of similar age. Hominin fossils from AHS, a new site, also derive from Member I. Hominin fossils from CHS can only be placed between 104 ka and 10 ka, the H. sapiens specimen from JHS is most likely 9-13 kyr in age, and a partial

  8. Transition from Plinian to unstable eruption conditions recorded in fine-grained proximal ash layers of the Middle Laacher See Tephra (12,900 a BP), East Eifel Volcanic Field, Germany

    DEFF Research Database (Denmark)

    Zernack, Anke Verena

    The 12,900 a BP eruption of Laacher See Volcano is a classic example of a complex, multi-phase Plinian eruption and one of the largest known of the Northern Hemisphere during the Late Quaternary. The wide range of primary and reworked pyroclastic deposits produced record drastically changing...... internal and external conditions during the course of the eruption. Here we focus on the so-called “Hauptbritzbank” (HBB), which marks a significant change in the eruptive style of Laacher See Volcano following the initial Plinian phase. The interval is characterised by a series of thin ash beds...... to assess their eruptive mechanism, transport processes and depositional conditions. Correlation between the Eastern and Southern fan proved difficult with dispersal axes of deposits pointing to two different locations within the Laacher See basin and some not intersecting the basin at all. In addition...

  9. Sediment records of Yellow River channel migration and Holocene environmental evolution of the Hetao Plain, northern China

    Science.gov (United States)

    Wang, Jingzhong; Wu, Jinglu; Pan, Baotian; Jia, Hongjuan; Li, Xiao; Wei, Hao

    2018-05-01

    The origin and evolution of lakes in the Hetao Plain, northern China, were influenced by climate variation, channel migration, and human activity. We analyzed a suite of sediment cores from the region to investigate Yellow River channel migration and environmental change in this region over the Holocene. Short sediment cores show that environmental indicators changed markedly around CE 1850, a time that corresponds to flood events, when large amounts of river water accumulated in the western part of the Hetao Plain, giving rise to abundant small lakes. Multiple sediment variables (environmental proxies) from two long cores collected in the Tushenze Paleolake area show that sediments deposited between 12.0 and 9.0 cal ka BP were yellow clay, indicative of fluvial deposition and channel migration. From 9.0 to 7.5 cal ka BP, sand was deposited, reflecting a desert environment. From 7.5 to 2.2 cal ka BP, however, the sediments were blue-gray clay that represents lacustrine facies of Lake Tushenze, which owes its origin to an increase in strength of the East Asian monsoon. At about 2.2 cal ka BP, the north branch of the Yellow River was flooded, and the Tushenze Paleolake developed further. Around 2.0 cal ka BP, the paleolake shrank and eolian sedimentation was recorded. The analyzed sediment records are consistent with the written history from the region, which documents channel migration and environmental changes in the Hetao Plain over the Holocene.

  10. Sedimentation

    Science.gov (United States)

    Cliff R. Hupp; Michael R. Schening

    2000-01-01

    Sedimentation is arguably the most important water-quality concern in the United States. Sediment trapping is cited frequently as a major function of riverine-forested wetlands, yet little is known about sedimcntation rates at the landscape scale in relation to site parameters, including woody vegetation type, elevation, velocity, and hydraulic connection to the river...

  11. A millennium of metallurgy recorded by lake sediments from Morococha, Peruvian Andes.

    Science.gov (United States)

    Cooke, Colin A; Abbott, Mark B; Wolfe, Alexander P; Kittleson, John L

    2007-05-15

    To date, information concerning pre-Colonial metallurgy in South America has largely been limited to the archaeological record of artifacts. Here, we reconstruct a millennium of smelting activity in the Peruvian Andes using the lake-sediment stratigraphy of atmospherically derived metals (Pb, Zn, Cu, Ag, Sb, Bi, and Ti) and lead isotopic ratios (206Pb/ 207Pb) associated with smelting from the Morococha mining region in the central Peruvian Andes. The earliest evidence for metallurgy occurs ca. 1000 A.D., coinciding with the fall of the Wari Empire and decentralization of local populations. Smelting during this interval appears to have been aimed at copper and copper alloys, because of large increases in Zn and Cu relative to Pb. A subsequent switch to silver metallurgy under Inca control (ca. 1450 to conquest, 1533 A.D.) is indicated by increases in Pb, Sb, and Bi, a conclusion supported by further increases of these metals during Colonial mining, which targeted silver extraction. Rapid development of the central Andes during the 20th century raised metal burdens by an order of magnitude above previous levels. Our results represent the first evidence for pre-Colonial smelting in the central Peruvian Andes, and corroborate the sensitivity of lake sediments to pre-Colonial metallurgical activity suggested by earlier findings from Bolivia.

  12. Modern limnology, sediment accumulation and varve formation processes in Lake Żabińskie, northeastern Poland: comprehensive process studies as a key to understand the sediment record

    Directory of Open Access Journals (Sweden)

    Alicja Bonk

    2014-12-01

    Full Text Available Reconstructions of paleoclimatic and paleoenvironmental data from sediment records require a thorough knowledge of the physical, chemical and biological factors that influence sediment-formation processes and signal preservation in lake sediments. Lake Żabińskie, an eutrophic hardwater lake located in northeastern Poland (Masurian Lake District, provides an unique environment for the investigation of processes that lead to the varve formation. During a two-year long observation period we investigated limnological and hydrochemical conditions within the water column, recent sediment fluxes and laminations preserved in the sediments of this lake to understand the relationship between the lake water properties and the sediment formation processes. We demonstrate that different mixing patterns may occur in Lake Żabińskie, from dimictic to meromictic depending on the meteorological conditions. Regardless of the water mixing pattern, the lake was stratified during much of the year which led to significant differences between surface and near-bottom water environments. The hypolimnion was characterized by higher conductivity and anoxic conditions with only short periods of better oxygenation, which created conditions ideal for the formation and preservation of biogenic varves. The material collected from the sediment trap revealed notable changes in sediment fluxes with characteristic spring maxima and, optionally, a second late fall maxima. Considerable variability was also observed for the fluxes of total organic carbon, biogenic silica and calcite. Microscopic investigation of the topmost sediments revealed a complex structure of the varves showing a distinct spring calcite lamina followed by several fine calcite laminae interbedded with diatom-rich laminae and, finally, by an organic-rich lamina with minerogenic admixtures deposited during winter. This seasonal variability was also reflected in the chemical composition inferred from high

  13. Major hydrologic shifts in northwest Florida during the Holocene from a lacustrine sediment record

    Science.gov (United States)

    Rodysill, J. R.; Donnelly, J. P.

    2011-12-01

    Recent climate extremes have threatened water resource availability and destroyed homes and infrastructure along the heavily populated northern Gulf of Mexico coast. Water resources in Northwest Florida, in particular, suffer from declining aquifer levels and salt water intrusion despite the presence of extensive river and aquifer systems. Intensive water resource management has been necessary to meet water supply demands during recent droughts. Advanced preparedness for abrupt climate events requires the ability to anticipate when hydrologic extremes are likely to occur; however, the long-term history of hydrologic extremes is not well known, and the instrumental record is too short to resolve longer-term hydrologic variability. Reconstructing the pre-instrumental hydrologic history is essential to building our understanding of the timing of and the driving forces behind wet and dry extremes. Here we present a new record of paleohydrology in northwest Florida based upon variations in sediment lithology and geochemistry from Rattlesnake Lake. We see evidence for both brief and long-lived changes in the lake environment during the Holocene. We compare our record to published pollen-based reconstructions of paleohydrology to examine the spatial and temporal patterns of paleohydrologic extremes across the northern Gulf of Mexico region during the Holocene.

  14. The 1845 Hekla eruption: Grain-size characteristics of a tephra layer

    Science.gov (United States)

    Gudnason, Jonas; Thordarson, Thor; Houghton, Bruce F.; Larsen, Gudrun

    2018-01-01

    The 1845 eruption is commonly viewed as a typical Hekla eruption. It is a key event in the eruptive history of the volcano, as it is one of the best documented Hekla eruptions, in terms of contemporary accounts and observations. The eruption started on 2 September 1845 with an intense, hour long explosive Plinian phase that passed into effusive activity, ending on the 16 March 1846. The amount of tephra produced in the opening phase was 0.13 km3/7.5 × 1010 kg. The total grain-size distribution of the deposit is bimodal with a dominant coarse mode at - 2.5 φ (5.6 mm) and a broad finer mode at 3 to 4.5 φ (0.125 to 0.045 mm). At individual sites, the grain-size distribution of the tephra from the Plinian opening phase is also commonly (not always) bimodal. Deconvolved grain-size distributions exhibit distinctly different sedimentation patterns of the coarse and fine subpopulations. The lapilli-dominated subpopulation fines rapidly with transport, while the ash-dominated subpopulation shows less changes with distance, indicating premature sedimentation of fines by aggregation from the 1845 volcanic plume. Tephra deposition was to the ESE of the volcano from a 19 km (a.s.l.) high eruption plume. The plume front travelled at speeds of 16-19 m s- 1. Reports of ash deposition onto ships near the Faroe and Shetland Islands, 700 to 1100 km away from Hekla, demonstrate that even moderate-sized Hekla eruptions can affect very large parts of European air-space.

  15. A multiproxy fjord sediment record of Holocene climate change from the subantarctic Auckland Islands

    Science.gov (United States)

    Browne, I. M.; Moy, C. M.; Wilson, G. S.; Neil, H.; Riesselman, C. R.

    2014-12-01

    The Southern Hemisphere Westerly Winds (SHWW) and the associated oceanic fronts have a major influence on atmospheric and oceanic circulation in the Southern Hemisphere. Sediment cores recovered from fjords along the eastern margin of the sub-Antarctic Auckland Islands (51°S, 166°E) are ideally located to sensitively record changes in the strength and position of the SHWW throughout the Holocene. A 5.75m core from Hanfield Inlet preserves both marine and terrestrial environmental components, which we use to develop a multiproxy record of past climatic conditions. This core, composed entirely of brown marine mud and silt, was recovered from a depth of 44m. Based on the entrance sill depth of the fjord (10mbsl) and our knowledge of regional sea level rise, we infer that the base of the core will be early Holocene in age, which will be confirmed using radiocarbon age dating. Benthic foraminiferal assemblages (125-500μm fraction) in surface and downcore samples are dominated by three taxa, Nonionellina flemingi, Cassidulina carinata and Quinqueloculina seminula. These species are either shallow infaunal or infaunal. We will use stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope geochemistry of the benthic foraminifera Nonionellina flemingi, Bolivina cf. earlandi, Trifarina angulosa, Bulimina marginata f. marginata and Cibicides species (all identified from Rose Bengal stained box-core samples) to reconstruct water column fluctuations associated with frontal migration. These results will compliment bulk sediment C and N concentration and isotope reconstructions of terrestrial organic matter delivery to fjord sub-basins over the past 12,000 years.

  16. Lake sediment records on climate change and human activities in the Xingyun Lake catchment, SW China.

    Science.gov (United States)

    Zhang, Wenxiang; Ming, Qingzhong; Shi, Zhengtao; Chen, Guangjie; Niu, Jie; Lei, Guoliang; Chang, Fengqin; Zhang, Hucai

    2014-01-01

    Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS) and CaCO3 content), as well as accelerator mass spectrometry (AMS) 14C datings, four major climatic stages during the Holocene have been identified in Xingyun's catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60-1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP) were associated with the ancient Dian culture within Xingyun's catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years.

  17. Lake sediment records on climate change and human activities in the Xingyun Lake catchment, SW China.

    Directory of Open Access Journals (Sweden)

    Wenxiang Zhang

    Full Text Available Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC, total nitrogen (TN, δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS and CaCO3 content, as well as accelerator mass spectrometry (AMS 14C datings, four major climatic stages during the Holocene have been identified in Xingyun's catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60-1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP were associated with the ancient Dian culture within Xingyun's catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years.

  18. Is it possible to use 'twin cores' as a unique sedimentary record? An experimental design based on sediment color

    International Nuclear Information System (INIS)

    Veiga-Pires, C; Mestre, N C

    2009-01-01

    Sedimentary cores are widely used for studying Quaternary records. However, the amount of sediment that is available is proportional to the diameter of the core, which is rarely bigger than 15 cm. One way to obtain more sediment is to use two cores retrieved from almost the same location and use them as if they represent a unique sedimentary record. In the present work, an experimental design has been applied to verify if 'twin cores' from an estuary can be considered as representing the same sedimentary record with twice the amount of sediment to study. Because sediment can be characterized based on its color, the variables used as replicates in the experimental design are the three Lab CIE colors acquired with a X-Rite Colortron spectrophotometer. Sediment cores were retrieved from the upper saltmarsh of Gilao River's estuary, southern Portugal. Twin cores, with in between distances of 50 cm, 100 cm and 200 cm, from two different sites were analysed. Results from a nested ANOVA show that even for the closest twin cores (50 cm apart) there is at least one color variable that shows significant variations between the profiles of both cores. These results clearly show that 'twin cores' cannot be used as a unique sedimentary record without any previous testing, at least in such transitional regions.

  19. Millennial-scale record of overwash deposits preserved within lagoon sediments from the Arabian Peninsula

    Science.gov (United States)

    Griffis, A. M.; Jessica, P.; Reinhardt, E. G.; Kosciuch, T. J.; Kovacs, S. E.; Hoffmann, G.

    2017-12-01

    Coastlines along the Arabian Sea are susceptible to tsunami-related inundation due to their proximity to the Makran Subduction Zone (MSZ). This subduction zone has seen decades of low intensity events, but has historically produced large tsunamigenic-earthquakes that have impacted the 100 million people living along the Arabian Sea. One major problem in assessing the seismic risk of the MSZ is that the historical record of events are spatially and temporally limited and rely heavily on eye witness accounts. This hinders our ability to forecast the potential magnitude and recurrence intervals of earthquakes and tsunamis that can be expected in the future. Sediments deposited by paleotsunamis are useful as they expand the decadal record of events to include millennial timescales that more accurately capture the full range of magnitudes and recurrence intervals. On November 28, 1945 a 8.1 Mw earthquake originating from the MSZ generated a tsunami inundating coastlines along the Arabian Sea with wave heights up to 13m. At Sur, a small village on the northeastern coastline of Oman, the tsunami deposited a laterally continuous shell-rich layer within a 12 km2 lagoon. This layer contained distinctive taphonomic assemblages of foraminifera and bivalves. Below the 1945 shelly deposit at Sur Lagoon, seven anomalous sand layers were found preserved within fine-grained lagoonal sediment. These layers of medium-coarse sands range in thickness from 5 to 35 cm and are separated by sandy-mud sediment. Grain size analysis shows that these anomalously coarse layers are followed by an abrupt return to lagoonal mud. The sand layers have features consistent with the 1945 tsunami deposit such as fining upward trends, sharp basal contact, and marine foraminifera (e.g., Amphistegina sp., planktics). In contrast, the surrounding lagoon deposits are generally massive, finer in grain size, and contain foraminiferal species typically found in shallow quiescent coastal environments (e

  20. Geochemical signatures of tephras from Quaternary Antarctic Peninsula volcanoes

    OpenAIRE

    Kraus,Stefan; Kurbatov,Andrei; Yates,Martin

    2013-01-01

    In the northern Antarctic Peninsula area, at least 12 Late Plelstocene-Holocene volcanic centers could be potential sources of tephra layers in the region. We present unique geochemical fingerprints for ten of these volcanoes using major, trace, rare earth element, and isotope data from 95 samples of tephra and other eruption products. The volcanoes have predominantly basaltic and basaltic andesitic compositions. The Nb/Y ratio proves useful to distinguish between volcanic centers located on ...

  1. Lake Sediment Records as an Indicator of Holocene Fluctuations of Quelccaya Ice Cap, Peru and Regional Climate

    Science.gov (United States)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.; Baranes, H. E.

    2012-12-01

    The past fluctuations of Quelccaya Ice Cap, (QIC; 13°S, 70°W, 5200 m asl) located in the southeastern Peruvian Andes, provide a record of tropical climate since the last glacial-interglacial transition. A detailed surficial geomorphic record of past glacial extents developed over the last several decades (e.g. Mercer and Palacios 1977; Buffen et al. 2009; Kelly et al. 2012 accepted) demonstrates that QIC is a dynamic glacial system. These records show that the ice cap was larger than present and retreating by ~11,500 yr BP, and smaller than present between ~7,000 and ~4,600 yr BP. The most recent advance occurred during the late Holocene (Little Ice Age;LIA), dated with 10Be surface exposure ages (510±90 yrs (n = 8)) (Stroup et al. in prep.). This overrode earlier deposits obscuring a complete Holocene record; we aim to address the gaps in glacial chronology using the sedimentary record archived in lakes. We retrieved two sets cores (8 and 5 m-long) from Laguna Challpacocha (13.91°S, 70.86°W, 5040 m asl), a lake that currently receives meltwater from QIC. Four radiocarbon ages from the cores suggest a continuous record dating to at least ~10,500 cal. yr BP. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, grayscale and X-ray fluorescence chemistry indicate changes in the amount of clastic sediment deposition. We interpret clastic sediments to have been deposited from ice cap meltwater, thus indicating more extensive ice. Clastic sediments compose the top of the core from 4 to 30 cm depth, below there is a sharp transition to organic sediments radiocarbon dated to (500±30 and 550±20 cal. yr BP). The radiocarbon ages are similar to the 10Be dated (LIA) glacial position. At least three other clastic units exist in the core; dating to ~2600-4300, ~4800-7300 and older then ~10,500 cal. yr BP based on a linear age model with four radiocarbon dates. We obtained two, ~4 m long, cores from Laguna Yanacocha (13.95°S,70.87

  2. Revised tephra volumes for Cascade Range volcanoes

    Science.gov (United States)

    Nathenson, Manuel

    2017-01-01

    Isopach maps from tephra eruptions from Mount St. Helens were reported in Carey et al. (1995) and for tephra eruptions from Glacier Peak in Gardner et al. (1998). For exponential thinning, the isopach data only define a single slope on a log thickness versus square root of area plot. Carey et al. (1995) proposed a model that was used to estimate a second slope, and volumes were presented in both studies using this model. A study by Sulpizio (2005) for estimating the second slope and square root of area where the lines intersect involves a systematic analysis of many eruptions to provide correlation equations. The purpose of this paper is to recalculate the volumes of Cascades eruptions and compare results from the two methods. In order to gain some perspective on the methods for estimating the second slope, we use data for thickness versus distance beyond the last isopach that are available for some of the larger eruptions in the Cascades. The thickness versus square root of area method is extended to thickness versus distance by developing an approximate relation between the two assuming elliptical isopachs with the source at one of the foci. Based on the comparisons made between the Carey et al. (1995) and Sulpizio (2005) methods, it is felt that the later method provides a better estimate of the second slope. For Mount St. Helens, the estimates of total volume using the Sulpizio (2005) method are generally smaller than those using the Carey et al. (1995) method. For the volume estimates of Carey et al. (1995), the volume of the May 18, 1980, eruption of Mount St. Helens is smaller than six of the eight previous eruptions. With the new volumes using the Sulpizio (2005) method, the 1980 eruption is smaller in volume than the upper end of the range for only three of the layers (Wn, Ye, and Yn) and is the same size as layer We. Thus the 1980 eruption becomes representative of the mid-range of volumes rather than being in the lower range.

  3. The upwelling record in the sediments of the westen continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; PrakashBabu, C.; Rao, Ch.M.

    substanzers in marinen sedimentes unter oxygierenden and reduzierenden Bediggungen. Dissertation, University of Kiel, 175 pp. MOLLER G. and M. GASTNER (1971) The 'Karbonbate Bombe' a simple device for the determination of the carbonate content in sediments...

  4. Offshore sediments record the history of onshore iron ore mining in Goa State, India

    Digital Repository Service at National Institute of Oceanography (India)

    Sebastian, T.; Nath, B.N.; Naik, Sangeeta; Borole, D.V.; Pierre, S.; Yazing, A.K.

    Environmental magnetic and geochemical analyses combined with 210Pb dating were carried out on a sediment core off Goa from Arabian Sea to reconstruct the sedimentation history of last three and a half centuries and to investigate the impact...

  5. The Rhine-Meuse delta: a record of intra-Holocene variable sediment delivery

    NARCIS (Netherlands)

    Erkens, G.; Cohen, K.M.

    2013-01-01

    Human impact is shown to be of impressive scale and magnitude, and has to be regarded a forcing factor that acts drainage-basin wide already millennia ago. The quantified sedimentation rates and reconstructed sediment delivery highlight the importance of variation in received fluvial sediment

  6. Holocene record of glacier variability from lake sediments reveals tripartite climate history for Svalbard

    Science.gov (United States)

    van der Bilt, Willem; Bakke, Jostein; Vasskog, Kristian; D`Andrea, William; Bradley, Raymond; Olafsdottir, Sædis

    2016-04-01

    The Arctic is responding sensitively to ongoing global climate change, warming and moistening faster than any other region on the planet. Holocene proxy paleoclimate time series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. Glaciers rapidly respond to climate shifts as demonstrated by their current demise around the world. This response has a composite climate signature, marked by shifts in hydroclimate (winter precipitation) as well as (summer) temperature. Attendant changes in glacier size are recorded by variations in glacigenic rock flour that may be deposited in downstream lakes. Here, we present a Holocene reconstruction of glacier activity, based on sediments from Hajeren, a glacier-fed lake on northwest Spitsbergen in the High Arctic Svalbard archipelago. Owing to undisturbed sediments and robust age control, we could resolve variability on a sub-centennial scale. To ensure the accurate detection of glacier activity, we applied a toolbox of physical, magnetic and geochemical proxies in conjunction with multivariate statistics. Our findings indicate a three-stage Holocene climate history for Svalbard, driving by melt water pulses, episodic Atlantic cooling and a decline in orbitally driven summer insolation. Correspondence between inferred advances, including a Holocene glacier maximum around 9.5 ka BP, suggests forcing by the melting LIS during the Early Holocene. Following a late Holocene Thermal Maximum around 7.4 ka BP, glaciers disappeared from the catchment. Glaciers reformed around 4.2 ka BP during the regional onset of the Neoglacial, supporting previous findings. This transition did, however, not mark the onset of persistent glacier activity in the catchment, but a series of centennial-scale cycles of growth and decay, including events around 3.3 and 1.1 ka BP. As orbitally driven insolation declined towards the present, the glaciation threshold

  7. Effect of recent climate change on Arctic Pb pollution: A comparative study of historical records in lake and peat sediments

    International Nuclear Information System (INIS)

    Liu Xiaodong; Jiang Shan; Zhang Pengfei; Xu Liqiang

    2012-01-01

    Historical changes of anthropogenic Pb pollution were reconstructed based on Pb concentrations and isotope ratios in lake and peat sediment profiles from Ny-Ålesund of Arctic. The calculated excess Pb isotope ratios showed that Pb pollution largely came from west Europe and Russia. The peat profile clearly reflected the historical changes of atmospheric deposition of anthropogenic Pb into Ny-Ålesund, and the result showed that anthropogenic Pb peaked at 1960s–1970s, and thereafter a significant recovery was observed by a rapid increase of 206 Pb/ 207 Pb ratios and a remarkable decrease in anthropogenic Pb contents. In contrast to the peat record, the longer lake record showed relatively high anthropogenic Pb contents and a persistent decrease of 206 Pb/ 207 Pb ratios within the uppermost samples, suggesting that climate-sensitive processes such as catchment erosion and meltwater runoff might have influenced the recent change of Pb pollution record in the High Arctic lake sediments. - Highlights: ► Historical changes of anthropogenic Pb pollution in Ny-Ålesund were reconstructed. ► Anthropogenic Pb in Ny-Ålesund was largely originated from W. European and Russia. ► Anthropogenic Pb recorded in peat sediments peaked at 1960–1970s and then declined. ► High anthropogenic fluxes were found in recent change of Pb record from lake sediments. ► Climate-sensitive processes might have influenced recent Pb accumulation rate in lakes. - This manuscript reports the effects of climate-sensitive processes on historical records of Pb pollution in sediments of Arctic lakes.

  8. Multiproxy records of Holocene climate and glacier variability from sediment cores in the Cordillera Vilcabamba of southern Peru

    Science.gov (United States)

    Schweinsberg, A. D.; Licciardi, J. M.; Rodbell, D. T.; Stansell, N.; Tapia, P. M.

    2012-12-01

    Sediments contained in glacier-fed lakes and bogs provide continuous high-resolution records of glacial activity, and preserve multiproxy evidence of Holocene climate change. Tropical glacier fluctuations offer critical insight on regional paleoclimatic trends and controls, however, continuous sediment records of past tropical climates are limited. Recent cosmogenic 10Be surface exposure ages of moraine sequences in the Cordillera Vilcabamba of southern Peru (13°20'S latitude) reveal a glacial culmination during the early Holocene and a less extensive glaciation coincident with the Little Ice Age of the Northern Hemisphere. Here we supplement the existing 10Be moraine chronology with the first continuous records of multiproxy climate data in this mountain range from sediment cores recovered from bogs in direct stratigraphic contact with 10Be-dated moraines. Radiocarbon-dated sedimentological changes in a 2-meter long bog core reveal that the Holocene is characterized by alternating inorganic and organic-rich laminae, suggesting high-frequency climatic variability. Carbon measurements, bulk density, and bulk sedimentation rates are used to derive a record of clastic sediment flux that serves as a proxy indicator of former glacier activity. Preliminary analyses of the bog core reveal approximately 70 diatom taxa that indicate both rheophilic and lentic environments. Initial results show a general decrease in magnetic susceptibility and clastic flux throughout the early to mid-Holocene, which suggests an interval of deglaciation. An episode of high clastic flux from 3.8 to 2.0 ka may reflect a late Holocene glacial readvance. Volcanic glass fragments and an anomalous peak in magnetic susceptibility may correspond to the historical 1600 AD eruption of Huaynaputina. Ten new bog and lake sediment cores were collected during the 2012 field expedition and analytical measurements are underway. Ongoing efforts are focused on analyzing diatom assemblage data, developing

  9. Linking sediment-charcoal records and ecological modeling to understand causes of fire-regime change in boreal forests

    Science.gov (United States)

    Linda B. Brubaker; Philip E. Higuera; T. Scott Rupp; Mark A. Olson; Patricia M. Anderson; Feng Sheng. Hu

    2009-01-01

    Interactions between vegetation and fire have the potential to overshadow direct effects of climate change on fire regimes in boreal forests of North America. We develop methods to compare sediment-charcoal records with fire regimes simulated by an ecological model, ALFRESCO (Alaskan Frame-based Ecosystem Code) and apply these methods to evaluate potential causes of a...

  10. Erosion of the Alps: use of Rb-Sr isotopic data from molassic sediments to identify the ages of the metamorphism recorded by the eroded rocks

    International Nuclear Information System (INIS)

    Henry, P.; Deloule, E.

    1994-01-01

    Rb-Sr isotopic data from Oligocene and Miocene peri-alpine molassic sediments allow us to identify the different periods for which the eroded rocks have or have not recorded an alpine metamorphism. The Chattian and the Burdigalian sediments result from the erosion of rocks for which the latest metamorphic event was variscan, while the Stampian, Aquitanian and ''Helvetian'' sediments show evidence for the erosion of rocks which have recorded alpine metamorphic events. The application of this method to old detrital sediments could permit determination of the ages of the tectonic events which occurred in the sediment source regions. (authors). 18 refs., 6 figs

  11. ENSO-Type Signals Recorded in the Late Cretaceous Laminated Sediments of Songliao Basin, Northeast China

    Science.gov (United States)

    Yu, E.; Wang, C.; Hinnov, L. A.; Wu, H.

    2014-12-01

    The quasi-periodic, ca. 2-7 year El Niño Southern Oscillation (ENSO) phenomenon globally influences the inter-annual variability of temperature and precipitation. Global warming may increase the frequency of extreme ENSO events. Although the Cretaceous plate tectonic configuration was different from today, the sedimentary record suggests that ENSO-type oscillations had existed at the time of Cretaceous greenhouse conditions. Cored Cretaceous lacustrine sediments from the Songliao Basin in Northeast China (SK-1 cores from the International Continental Drilling Program) potentially offer a partially varved record of Cretaceous paleoclimate. Fourteen polished thin sections from the depth interval 1096.12-1096.53 m with an age of 84.4 Ma were analyzed by optical and scanning electron microscopy (SEM). ImageJ software was applied to extract gray scale curves from optical images at pixel resolution. We tracked minimum values of the gray scale curves to estimate the thickness of each lamina. Five sedimentary structures were recognized: flaser bedding, wavy bedding, lenticular bedding, horizontal bedding, and massive layers. The mean layer thicknesses with different sedimentary structures range from 116 to 162mm, very close to the mean sedimentation rate estimated for this sampled interval, 135mm/year, indicating that the layers bounded by pure clay lamina with the minimum gray values are varves. SEM images indicate that a varve is composed, in succession, of one lamina rich in coarse silt, one lamina rich in fine silt, one clay-rich lamina with some silt, and one clay-rich lamina. This suggests that a Cretaceous year featured four distinct depositional seasons, two of which were rainy and the others were lacking precipitation. Spectral analysis of extended intervals of the tuned gray scale curve indicates the presence of inter-annual periodicities of 2.2-2.7 yr, 3.5-6.1 year, and 10.1-14.5 year consistent with those of modern ENSO cycles and solar cycles, as well as

  12. The record of India-Asia collision preserved in Tethyan ocean basin sediments.

    Science.gov (United States)

    Najman, Yani; Jenks, Dan; Godin, Laurent; Boudagher-Fadel, Marcelle; Bown, Paul; Horstwood, Matt; Garzanti, Eduardo; Bracialli, Laura; Millar, Ian

    2015-04-01

    the time of collision. With the recent discovery that the Indus Group sediments in the suture zone cannot be used for this purpose as previously proposed (Henderson et al. 2011) we turn to the 54 Ma Kong and Chulung La Formation youngest Tethyan sediments on the Indian margin (Garzanti et al. 1987) to investigate whether we can identify such material, and whether it be Spong arc (Fuchs and Willems 1990), KLA or Trans-Himalayan derived, thus determining what collided with India and when. References Bouilhol P, Jagoutz O, Hanchar JM, Dudas FO. 2013. Dating the India-Eurasia collision through arc magmatic records. Earth and Planetary Science Letters 366, 163-175. Chatterjee S, Goswami A, Scotese CR. 2013. The longest voyage: Tectonic, magmatic, and paleoclimatic evolution of the Indian plate during its northward flight from Gondwana to Asia. Gondwana Research 23, 238-267. Clift P, Carter A, Krol M, Kirby E. 2002. Constraints on India-Eurasia collision in the Arabian sea region taken from the Indus Group, Ladakh Himalaya, India. The tectonic and climatic evolution of the Arabian Sea region Geological Society of London Special Publication 195, 97-116. de Sigoyer J, Chavagnac V, Blichert-Toft J, Villa IM, Luais B, Guillot S, Cosca M, Mascle G. 2000. Dating the Indian continental subduction and collisional thickening in the northwest Himalaya: Multichronology of the Tso Morari eclogites. Geology 28, 487-490. Fuchs G, Willems H. 1990. The final stages of sedimentation in the Tethyan zone of Zanskar and their geodynamic significance (Ladakh - Himalaya). Jahrbuche Geologische Bundenstalt 133: 259-273. Garzanti E, Baud A, Mascle G. 1987. Sedimentary Record of the Northward Flight of India and Its Collision with Eurasia (Ladakh Himalaya, India). Geodinamica Acta 1, 297-312. Green OR, Searle MP, Corfield RI, Corfield RM. 2008. Cretaceous-tertiary carbonate platform evolution and the age of the India-Asia collision along the Ladakh Himalaya (northwest India). J Geol 116: 331

  13. Synchronizing Greenland ice-core records and the Meerfelder maar sediment record via the global cosmogenic radionuclide signature and insights on climate around 11,230 years BP

    Science.gov (United States)

    Mekhaldi, F.; Czymzik, M.; Brauer, A.; Martin-Puertas, C.; Aldahan, A.; Possnert, G.; Muscheler, R.

    2017-12-01

    The causal investigation of multiple paleoclimate records relies on the accuracy of their respective chronostratigraphy. To achieve relative synchronization, cosmogenic radionuclides are an excellent tool because their common signature is global and can be retrieved and measured in different paleoclimate archives. For instance, 10Be can be measured in both ice cores and lake sediments (Berggren et al., 2013; Czymzik et al., 2016) which allows for both archives to be anchored onto radiocarbon timescales by synchronizing 10Be with 14C. We investigate the period 11,500-11,000 years BP when a short cold climate spell is known, from ice-core proxy records, to have occurred in Greenland shortly after the onset of the Holocene - the Preboreal Oscillation (PBO). This period also coincides with one of the largest and longest-lived increase in 14C production rate during the Holocene, which most likely corresponds to a grand solar minimum (around 11,230-11,000 years BP). In consequence, this period ideally illustrates the potential of using a known and clear signal in the production rate of cosmogenic radionuclides as a synchronizing tool, such as caused by large variations in solar activity. Here we measure 10Be in Meerfelder Maar (a well-dated and widely used sediment record from Germany) around 11,230 years BP which allows us to align the 10Be signal in both the Meerfelder Maar (MFM) sediment record and the GRIP ice core to IntCal13. Doing so, we report that i) the structure of the grand solar minimum is well-preserved in the 10Be signal of MFM sediments, ii) the PBO in Greenland occurs during high levels of solar activity and is not clearly observed in MFM, and iii) the PBO in Greenland ends precisely at the onset of the grand solar minimum at 11,230 years BP which also corresponds to a depositional change in MFM sediments (Martin-Puertas et al., 2017). These results thus suggest that changes in solar activity could have been a forcing at play eventually resulting in the

  14. Climate and lake-level history of the northern Altiplano, Bolivia, as recorded in Holocene sediments of the Rio Desaguadero

    Energy Technology Data Exchange (ETDEWEB)

    Baucom, P.C.; Rigsby, C.A. [East Carolina Univ., Greenville, NC (United States). Dept. of Geology

    1999-05-01

    Strata exposed in terraces and modern cutbanks along the Rio Desaguadero contain a variety of lithofacies that were deposited in four distinct facies associations. These facies associations document a history of aggradation and downcutting that is linked to Holocene climate change on the Altiplano. Braided-stream, meandering-stream, deltaic and shoreline, and lacustrine sediments preserved in multi-level terraces in the northern Rio Desaguadero valley record two high-water intervals: one between 4,500 and 3,900 yr BP and another between 2,000 and 2,200 yr BP. These wet periods were interrupted by three periods of fluvial downcutting, centered at approximately 4,000 yr BP, 3,600 yr BP, and after 2,000 yr BP. Braided-river sediments preserved in a single terrace level in the southern Rio Desaguadero valley record a history of nearly continuous fluvial sedimentation from at least 7,000 yr BP until approximately 3,200 yr BP that was followed by a single episode (post-3,210 yr BP) of down-cutting and lateral migration. The deposition and subsequent fluvial downcutting of the northern strata was controlled by changes in effective moisture that can be correlated to Holocene water-level fluctuations of Lake Titicaca. The deposition and dissection of braided-stream sediments to the south are more likely controlled by a combination of base-level change and sediment input from the Rio Mauri.

  15. Holocene pollen and sediment record from the tangle lakes area, central Alaska

    Science.gov (United States)

    Ager, Thomas A.; Sims, John D.

    1981-01-01

    Pollen and sediments have been analyzed from a 5.5 meter‐length core of lacustrine sediments from Tangle Lakes, in the Gulkana Upland south of the Alaska Range (63 ° 01 ‘ 46”; N. latitude, 146° 03 ‘ 48 “ W. longitude). Radiocarbon ages indicate that the core spans the last 4700 years. The core sediments are sandy silt and silty clay; the core shows distinct rhythmic laminations in the lower 398 cm. The laminae appear to be normally graded; peat fibers and macerated plant debris are more abundant near the tops of the laminae. Six volcanic‐ash layers are present in the upper 110 cm of the core.Present‐day vegetation of the Tangle Lakes area is mesic shrub tundra and open spruce woodland, with scattered patches of shrub willow (Salix), balsam poplar (P. balsamifera), spruce (Picea), paper birch (Betula papyrifera), and alder (Alnus). Pollen analysis of 27 core samples suggests that this vegetation type has persisted throughout the past 4700 years, except for an apparently substantial increase in Picea beginning about 3500 years B.P. Percentages of Picea pollen are very low (generally 1–3 percent) in the lower 2 meters of core (ca. 4700 to 3500 years B.P.), but rise to 13–18 percent in the upper 3.4 meters (ca. 3500 years B.P. to present). Previously reported data from this area indicate that Picea trees initially arrived in the Tangle Lakes area about 9100 years B.P., at least 2.5 to 3 thousand years after deglaciation of the region. The present investigation suggests that Picea trees became locally scarce or died out sometime after about 9000 years B.P. but before 4700 years B.P., then reinvaded the area about 3500 years B.P. If this extrapolated age for the Picea reinvasion is accurate it suggests that local expansion of the Picea population coincides with the onset of a Neoglacial interval of cooler, moister climate. This is an unexpected result, because intervals of cooler climate generally coincide with lowering of the altitudinal limit of

  16. Five thousand years of tropical lake sediment DNA records from Benin

    Science.gov (United States)

    Bremond, L.; Favier, C.; Ficetola, G. F.; Tossou, M. G.; Akouégninou, A.; Gielly, L.; Giguet-Covex, C.; Oslisly, R.; Salzmann, U.

    2017-08-01

    Until now, sedimentary DNA (sedDNA) studies have only focused on cold and temperate regions were DNA is relatively well preserved. Consequently, the tropics, where vegetation is hyperdiverse and natural archives are rare, have been neglected and deserve attention. In this study, we used next-generation sequencing to barcode sedDNA from Lake Sele, localized in the tropical lowlands of Benin (Africa), and compared the taxonomic diversity detected by DNA analyses with pollen assemblages. Plant sedDNA was successfully amplified from 33 of the 34 successfully extracted samples. In total, 43 taxa were identified along the 5000 years spanned by the sediment: 22 taxa were identified at the family level and 21 at the genus level. The plant diversity recovered through sedDNA from Lake Sele showed a specific local signal and limited overlapping with pollen. Introduced plants, grown and cultivated close to the water, such as sweet potato, were also well recorded by sedDNA. It appears, therefore, to be a promising approach to studying past diversity in tropical regions, and could help in tracking the introduction and history of agriculture. This is the first time this method has been used in the field of domestication and dissemination of several specific crops, and the results are very encouraging.

  17. Application of sediment core modelling to interpreting the glacial-interglacial record of Southern Ocean silica cycling

    Directory of Open Access Journals (Sweden)

    A. Ridgwell

    2007-07-01

    Full Text Available Sediments from the Southern Ocean reveal a meridional divide in biogeochemical cycling response to the glacial-interglacial cycles of the late Neogene. South of the present-day position of the Antarctic Polar Front in the Atlantic sector of the Southern Ocean, biogenic opal is generally much more abundant in sediments during interglacials compared to glacials. To the north, an anti-phased relationship is observed, with maximum opal abundance instead occurring during glacials. This antagonistic response of sedimentary properties provides an important model validation target for testing hypotheses of glacial-interglacial change against, particularly for understanding the causes of the concurrent variability in atmospheric CO2. Here, I illustrate a time-dependent modelling approach to helping understand climates of the past by means of the mechanistic simulation of marine sediment core records. I find that a close match between model-predicted and observed down-core changes in sedimentary opal content can be achieved when changes in seasonal sea-ice extent are imposed, whereas the predicted sedimentary response to iron fertilization on its own is not consistent with sedimentary observations. The results of this sediment record model-data comparison supports previous inferences that the changing cryosphere is the primary driver of the striking features exhibited by the paleoceanographic record of this region.

  18. A 500 year sediment lake record of anthropogenic and natural inputs to Windermere (English Lake District) using double-spike lead isotopes, radiochronology, and sediment microanalysis.

    Science.gov (United States)

    Miller, Helen; Croudace, Ian W; Bull, Jonathan M; Cotterill, Carol J; Dix, Justin K; Taylor, Rex N

    2014-07-01

    A high-resolution record of pollution is preserved in recent sediments from Windermere, the largest lake in the English Lake District. Data derived from X-ray core scanning (validated against wavelength dispersive X-ray fluorescence), radiochronological techniques ((210)Pb and (137)Cs) and ultrahigh precision, double-spike mass spectrometry for lead isotopes are combined to decipher the anthropogenic inputs to the lake. The sediment record suggests that while most element concentrations have been stable, there has been a significant increase in lead, zinc, and copper concentrations since the 1930s. Lead isotope down-core variations identify three major contributory sources of anthropogenic (industrial) lead, comprising gasoline lead, coal combustion lead (most likely source is coal-fired steam ships), and lead derived from Carboniferous Pb-Zn mineralization (mining activities). Periods of metal workings do not correlate with peaks in heavy metals due to the trapping efficiency of up-system lakes in the catchment. Heavy metal increases could be due to flood-induced metal inwash after the cessation of mining and the weathering of bedrock in the catchment. The combination of sediment analysis techniques used provides new insights into the pollutant depositional history of Windermere and could be similarly applied to other lake systems to determine the timing and scale of anthropogenic inputs.

  19. Toward a Last Interglacial Compilation Using a Tephra-based Chronology: a Future Reference For Model-data Comparison

    Science.gov (United States)

    Bazin, L.; Govin, A.; Capron, E.; Nomade, S.; Lemieux-Dudon, B.; Landais, A.

    2017-12-01

    The Last Interglacial (LIG, 129-116 ka) is a key period to decipher the interactions between the different components of the climate system under warmer-than-preindustrial conditions. Modelling the LIG climate is now part of the CMIP6/PMIP4 targeted simulations. As a result, recent efforts have been made to propose surface temperature compilations focusing on the spatio-temporal evolution of the LIG climate, and not only on its peak warmth as previously proposed. However, the major limitation of these compilations remains in the climatic alignment of records (e.g. temperature, foraminiferal δ18O) that is performed to define the sites' chronologies. Such methods prevent the proper discussion of phase relationship between the different sites. Thanks to recent developments of the Bayesian Datice dating tool, we are now able to build coherent multi-archive chronologies with a proper propagation of the associated uncertainties. We make the best use of common tephra layers identified in well-dated continental archives and marine sediment cores of the Mediterranean region to propose a coherent chronological framework for the LIG independent of any climatic assumption. We then extend this precise chronological context to the North Atlantic as a first step toward a global coherent compilation of surface temperature and stable isotope records. Based on this synthesis, we propose guidelines for the interpretation of different proxies measured from different archives that will be compared with climate model parameters. Finally, we present time-slices (e.g. 127 ka) of the preliminary regional synthesis of temperature reconstructions and stable isotopes to serve as reference for future model-data comparison of the up-coming CMIP6/PMIP4 LIG simulations.

  20. New marine geophysical and sediment record of the Northeast Greenland Ice Stream.

    Science.gov (United States)

    Callard, L.; Roberts, D. H.; O'Cofaigh, C.; Lloyd, J. M.; Smith, J. A.; Dorschel, B.

    2017-12-01

    The NE Greenland Ice Stream (NEGIS) drains 16% of the Greenland Ice Sheet (GrIS) and has a sea-level equivalent of 1.1-1.4 m. Stabilised by two floating ice shelves, 79N and Zachariae Isstrom, until recently it has shown little response to increased atmospheric and oceanic warming. However, since 2010 it has experienced an accelerated rate of grounding line retreat ( 4 km) and significant ice shelf loss that indicates that this sector of the GrIS is now responding to current oceanic and/or climatic change and has the potential to be a major contributor to future global sea-level rise. The project `NEGIS', a collaboration between Durham University and AWI, aims to reconstruct the history of the NE Greenland Ice Stream from the Last Glacial Maximum (LGM) to present using both onshore and offshore geological archives to better understand past ice stream response to a warming climate. This contribution presents results and interpretations from an offshore dataset collected on the RV Polarstern, cruises PS100 and PS109 in 2016 and 2017. Gravity and box cores, supplemented by swath bathymetric and sub-bottom profiler data, were acquired and initial core analysis including x-radiographs and MSCL data logging has been performed. Data collection focused principally in the Norske Trough and the area directly in front of the 79N ice shelf, a sub-ice shelf environment as recently as two years ago. On the outer shelf streamlined subglacial bedforms, grounding-zone wedges and moraines as well as overconsolidated subglacial tills, record an extensive ice sheet advance to the shelf edge. On the inner shelf and in front of the 79N ice shelf, deep, glacially-eroded bedrock basins are infilled with stratified sediment. The stratified muds represent deglacial and Holocene glacimarine sedimentation, and capture the recent transition from sub-ice shelf to shelf free conditions. Multiproxy palaeoenvironmental reconstructions, including foraminifera and diatom analysis, and radiocarbon

  1. A Model-Based Approach to Infer Shifts in Regional Fire Regimes Over Time Using Sediment Charcoal Records

    Science.gov (United States)

    Itter, M.; Finley, A. O.; Hooten, M.; Higuera, P. E.; Marlon, J. R.; McLachlan, J. S.; Kelly, R.

    2016-12-01

    Sediment charcoal records are used in paleoecological analyses to identify individual local fire events and to estimate fire frequency and regional biomass burned at centennial to millenial time scales. Methods to identify local fire events based on sediment charcoal records have been well developed over the past 30 years, however, an integrated statistical framework for fire identification is still lacking. We build upon existing paleoecological methods to develop a hierarchical Bayesian point process model for local fire identification and estimation of fire return intervals. The model is unique in that it combines sediment charcoal records from multiple lakes across a region in a spatially-explicit fashion leading to estimation of a joint, regional fire return interval in addition to lake-specific local fire frequencies. Further, the model estimates a joint regional charcoal deposition rate free from the effects of local fires that can be used as a measure of regional biomass burned over time. Finally, the hierarchical Bayesian approach allows for tractable error propagation such that estimates of fire return intervals reflect the full range of uncertainty in sediment charcoal records. Specific sources of uncertainty addressed include sediment age models, the separation of local versus regional charcoal sources, and generation of a composite charcoal record The model is applied to sediment charcoal records from a dense network of lakes in the Yukon Flats region of Alaska. The multivariate joint modeling approach results in improved estimates of regional charcoal deposition with reduced uncertainty in the identification of individual fire events and local fire return intervals compared to individual lake approaches. Modeled individual-lake fire return intervals range from 100 to 500 years with a regional interval of roughly 200 years. Regional charcoal deposition to the network of lakes is correlated up to 50 kilometers. Finally, the joint regional charcoal

  2. Connecting, synchronising, and dating with tephras : principles and applications of tephrochronology in Quaternary research

    International Nuclear Information System (INIS)

    Lowe, D.J.

    2016-01-01

    Tephrochronology is a unique method for linking and dating geological, palaeoecological, palaeoclimatic or archaeological sequences or events. The method relies firstly and fundamentally on stratigraphy and the law of superposition, which apply in any study that connects or correlates deposits from one place to another. Secondly, it relies on characterising and hence identifying or 'fingerprinting' tephra layers using either physical properties evident in the field or those obtained from laboratory analysis, including mineralogical examination by optical microscopy or geochemical analysis of glass shards or crystals (e.g. Fe-Ti oxides, ferromagnesian minerals) using the electron microprobe and other tools. Thirdly, the method is enhanced when a numerical age is obtained for a tephra layer by (1) radiometric methods such as radiocarbon, fission-track, U-series, or Ar/Ar dating, (2) incremental dating methods including dendrochronology or varved sediments or layering in ice cores, or (3) age-equivalent methods such as palaeomagnetism or correlation with marine oxygen isotope stages or palynostratigraphy. Once known, that age can be transferred from one site to the next using stratigraphic methods and by matching compositional characteristics, i.e. comparing 'fingerprints' from each layer. Used this way, tephrochronology is an age-equivalent dating method. (author).

  3. Connecting with tephras : principles, functioning, and applications of tephrochronology in Quaternary science

    International Nuclear Information System (INIS)

    Lowe, D.J.

    2013-01-01

    Tephrochronology is a unique method for linking and dating geological, palaeoecological, palaeoclimatic or archaeological sequences or events. The method relies firstly and fundamentally on stratigraphy and the law of superposition, which apply in any study that connects or correlates deposits from one place to another. Secondly, it relies on characterising and hence identifying or 'fingerprinting' tephra layers using either physical properties evident in the field or those obtained from laboratory analysis, including mineralogical examination by optical microscopy or geochemical analysis of glass shards or crystals (e.g. Fe-Ti oxides, ferromagnesian minerals) using the electron microprobe and other tools. Thirdly, the method is enhanced when a numerical age is obtained for a tephra layer by (1) radiometric methods such as radiocarbon, fission-track, U-series, or Ar/Ar dating, (2) incremental dating methods including dendrochronology or varved sediments or layering in ice cores, or (3) age-equivalent methods such as palaeomagnetism or correlation with marine oxygen isotope stages or palynostratigraphy. Once known, that age can be transferred from one site to the next using stratigraphic methods and by matching compositional characteristics, i.e. comparing 'fingerprints' from each layer. Used this way, tephrochronology is an age-equivalent dating method. (author). 150 refs., 13 figs., 5 tabs.

  4. Connecting with tephras: principles, functioning, and applications of tephrochronology in Quaternary science

    International Nuclear Information System (INIS)

    Lowe, D.J.

    2014-01-01

    Tephrochronology is a unique method for linking and dating geological, palaeoecological, palaeoclimatic or archaeological sequences or events. The method relies firstly and fundamentally on stratigraphy and the law of superposition, which apply in any study that connects or correlates deposits from one place to another. Secondly, it relies on characterising and hence identifying or 'fingerprinting' tephra layers using either physical properties evident in the field or those obtained from laboratory analysis, including mineralogical examination by optical microscopy or geochemical analysis of glass shards or crystals (e.g. Fe-Ti oxides, ferromagnesian minerals) using the electron microprobe and other tools. Thirdly, the method is enhanced when a numerical age is obtained for a tephra layer by (1) radiometric methods such as radiocarbon, fission-track, U-series, or Ar/Ar dating, (2) incremental dating methods including dendrochronology or varved sediments or layering in ice cores, or (3) age-equivalent methods such as palaeomagnetism or correlation with marine oxygen isotope stages or palynostratigraphy. Once known, that age can be transferred from one site to the next using stratigraphic methods and by matching compositional characteristics, i.e. comparing 'fingerprints' from each layer. Used this way, tephrochronology is an age-equivalent dating method. (author)

  5. Connecting, synchronising, and dating with tephras : principles and applications of tephrochronology in Quaternary research

    International Nuclear Information System (INIS)

    Lowe, D.J.

    2017-01-01

    Tephrochronology is a unique method for linking and dating geological, palaeoecological, palaeoclimatic or archaeological sequences or events. The method relies firstly and fundamentally on stratigraphy and the law of superposition, which apply in any study that connects or correlates deposits from one place to another. Secondly, it relies on characterising and hence identifying or 'fingerprinting' tephra layers using either physical properties evident in the field or those obtained from laboratory analysis, including mineralogical examination by optical microscopy or geochemical analysis of glass shards or crystals (e.g. Fe-Ti oxides, ferromagnesian minerals) using the electron microprobe and other tools. Thirdly, the method is enhanced when a numerical age is obtained for a tephra layer by (1) radiometric methods such as radiocarbon, fission-track, U-series, or Ar/Ar dating, (2) incremental dating methods including dendrochronology or varved sediments or layering in ice cores, or (3) age-equivalent methods such as palaeomagnetism or correlation with marine oxygen isotope stages or palynostratigraphy. Once known, that age can be transferred from one site to the next using stratigraphic methods and by matching compositional characteristics, i.e. comparing 'fingerprints' from each layer. Used this way, tephrochronology is an age-equivalent dating method. (author).

  6. Unravelling the magnetic record in marine and continental sediments : climatic versus geomagnetic signals

    NARCIS (Netherlands)

    Kruiver, Pauline Pascal

    2001-01-01

    Magnetic iron oxides and iron sulfides are present as trace constituents in sediments. These magnetic particles can carry a natural remanent magnetisation (NRM). When the sediment consolidates and lithifies after deposition, the direction of the then ambient field is preserved. The amount of

  7. Punctuated sediment record resulting from channel migration in a shallow sand-dominated micro-tidal lagoon, Northern Wadden Sea, Denmark

    DEFF Research Database (Denmark)

    Fruergaard, M.; Andersen, T.J.; Nielsen, L.H.

    2011-01-01

    depositional environment, but tidal channel sediments dominate in the five sediment cores, making up 56% of the 15 mof sediment core. Sedimentation in the lagoon alternated between slow vertical aggradation of sand flats (1.5–2 mm yr-1) and very fast lateral progradation of point bars in tidal channels, which...... caused the formation of a punctuated lagoonal fill. Frequent and comprehensive reworking of the sand flat sediments by tidal channel migration entails loss of sedimentary structures and bioturbation related to sand flat deposits, and old sand flat sediments are only very sparsely preserved. We further...... conclude that long-term (millennial timescale) sediment accumulation in the lagoon was controlled by rising sea-level, whereas short-term (centurial timescale) sediment accumulation was controlled by local erosion and depositional events caused by lateral migration of channels. Records of short-term sea...

  8. Seabed Motion During Sediment Density Flows as Recorded by Displaced Man-Made Motion-Recording Boulders and a Heavy Instrument Platform

    Science.gov (United States)

    Gwiazda, R.; Paull, C. K.; Kieft, B.; Bird, L.; Klimov, D.; Herlien, R.; Sherman, A.; McCann, M. P.; Sumner, E.; Talling, P.; Xu, J.; Parsons, D. R.; Maier, K. L.; Barry, J.

    2017-12-01

    Over a period of 18 months the Coordinated Canyon Experiment documented the passage of at least 15 sediment density flows in Monterey Canyon, offshore California, with an array of moorings and sensors placed from 200 m to 1,850 m water depths. Free-standing `smart' boulders (Benthic Event Detectors, BED) and a 1,000 Kg tripod with an Acoustic Monitoring Transponder (AMT) and a BED attached to it were deployed in the upper canyon to detect seabed motions during sediment density flows. BEDs consist of spheres made of a combination of metal, plastic and syntactic foam ballasted to 2.1 g/cm3 density, containing accelerometers along three orthogonal axes, a time recorder, and a pressure sensor inside a pressure case rated to 500 m water depth. Acceleration of ≥ 0.008 G triggers data collection at a recording rate of 50 Hz until motion stops. Built-in acoustic beacons and modems allow for BEDs to be relocated, and data to be downloaded, even when BEDs are buried in sediment to depths of >1 m. Over the course of the study, depth changes and velocities of 24 BED movements during 9 events were recorded. BEDs moved at the velocity of the propagation of the flows down canyon, as documented by the time of arrival of the flow at successive sensors, but sometimes travelled at lower speeds. Seven movements of the AMT tripod were also recorded. In the largest of these, the heavy AMT tripod was transported over a distance of 4.1 Km. For at least four of these seven motions the AMT temperature record indicates that the movements were initiated while the tripod was buried. In one particular event simultaneous movements of five BEDs over a 100 m depth range indicate that the entire seabed was in motion at the same time over a canyon distance of 3.5 Km. Reconstructions of instrument motions in this event from their internally recorded acceleration data show that the AMT displacement was at the front of the event and had no rotational component. In contrast, free standing BEDs at the

  9. Elemental geochemical records of seafloor hydrothermal activities in the sediments from the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    ZHAI Shikui; YU Zenghui; DU Tongjun

    2007-01-01

    The major and minor element contents in the sediment core H9 from the hydrothermal fields of the Okinawa Trough show a sharp change at the depth of 80 cm. The elements enriched in the upper 80 cm core are those enriched in the hydrothermal deposits and in the surface sediments recovered from the hydrothermal fields in the trough, which indicates the input of hydrothermal materials. Comparing with other hydrothermal sediments from Mid-ocean Ridges or the Lau Basin, the degree of the enrichment of elements iron, copper, cobalt, and nickel is relatively low. However, the enrichment of elements manganese, lead, arsenic, antimony and mercury is remarkable. The average contents of these elements in the upper 80 cm core sediments are three to six times those in the lower section, and 3 ~ 12 times those in the surface sediments which are not influenced by hydrothermal activities. Hydrothermal activities have contributed significant manganese, lead, arsenic, antimony and mercury to the sediments, and these elements are distinct indicators for the hydrothermal activity in the Okinawa Trough. The significant enrichment of these elements in Core H9 upward from the depth 80 cm indicates the start or the significant enhancing of the hydrothermal activity in this area at about 5 740 aB. P. The average accumulation rate of manganese during this period is about 40 461 μg/( cm2 · ka), which is similar to the hydrothermal sediments in the Lau Basin or the East Pacific Rise.

  10. Atmospheric lead fallout over the last century recorded in Gulf of Lions sediments (Mediterranean Sea)

    International Nuclear Information System (INIS)

    Miralles, J. . E-mail jmiralles@wanadoo.fr; Veron, A.J.; Radakovitch, O.; Deschamps, P.; Tremblay, T.; Hamelin, B.

    2006-01-01

    Six marine sediment cores from the Gulf of Lions continental slope (700-1700 m water depth) were analyzed for stable lead isotopes and 21 Pb geochronology in order to reconstruct lead atmospheric fallout pattern during the last century. The detrital lead contribution is 25 μg g -1 and the mean sediment anthropogenic inventory is 110 ± 7 μg cm -2 , a little bit higher than atmospheric deposition estimate. Anthropogenic lead accumulation in sediments peaked in early 1970s (1973 ± 2) in agreement with lead emissions features. For the period 1986-1997, the sediment signal also reflect the decrease of atmospheric lead described by independent atmospheric fallout investigations. The anthropogenic Pb deposition in the late 1990s was similar to the 1950s deposition, attesting thus of the output of European environmental policies

  11. High-resolution chronology of sediment below CCD based on Holocene paleomagnetic secular variations in the Tohoku-oki earthquake rupture zone

    Science.gov (United States)

    Kanamatsu, Toshiya; Usami, Kazuko; McHugh, Cecilia M. G.; Ikehara, Ken

    2017-08-01

    Using high-resolution paleomagnetic data, we examined the potential for obtaining precise ages from sediment core samples recovered from deep-sea basins close to rupture zones of the 2011 and earlier earthquakes off Tohoku, Japan. Obtaining detailed stratigraphic ages from deep-sea sediments below the calcium compensation depth (CCD) is difficult, but we found that the samples contain excellent paleomagnetic secular variation records to constrain age models. Variations in paleomagnetic directions obtained from the sediments reveal systematic changes in the cores. A stacked paleomagnetic profile closely matches the Lake Biwa data sets in southwest Japan for the past 7000 years, one can establish age models based on secular variations of the geomagnetic field on sediments recovered uniquely below the CCD. Comparison of paleomagnetic directions near a tephra and a paleomagnetic direction of contemporaneous pyroclastic flow deposits acquired by different magnetization processes shows precise depositional ages reflecting the magnetization delay of the marine sediment record.Plain Language SummaryGenerally obtaining detailed ages from deep-sea sediments is difficult, because available dating method is very limited. We found that the deep-see sediment off North Japan recorded past sequential geomagnetic directions. If those records correlate well with the reference record in past 7000 years, then we could estimate age of sediment by pattern matching. Additionally a volcanic ash emitted in 915 A.D., which was intercalated in our samples, indicates a time lag in our age model. This observation makes our age model more precise.

  12. physical volcanology of pyroclastic tephra deposit at batoke mt.

    African Journals Online (AJOL)

    Home

    2013-04-16

    Apr 16, 2013 ... In the deposit three facies types; which are the lava flow, the lapilli and ash ... flow flanked by the tephra pile, the lack of accidental clasts, and the ..... Origin of the Lethal gas ... eruption behaviour and petrochemistry of lava.

  13. Tephra stratification of volcanic ash soils in Nothern Ecuador

    NARCIS (Netherlands)

    Tonneijck, F.H.; Hageman, J.A.; Sevink, J.; Verstraten, J.M.

    2008-01-01

    We combined proxies traditionally used in stratigraphic research (mineral assemblages, grain size distribution, and element ratios) with soil organic carbon contents and radiocarbon dating both at a high vertical resolution, to unravel the tephra stratigraphy in volcanic ash soils. Our results show

  14. Geochemistry of buried river sediments from Ghaggar Plains, NW India: Multi-proxy records of variations in provenance, paleoclimate, and paleovegetation patterns in the Late Quaternary

    DEFF Research Database (Denmark)

    Singh, Ajit; Paul, Debajyoti; Sinha, Rajiv

    2016-01-01

    We report the first geochemical record in two drill-sediment cores from a buried channel in the Ghaggar Plains of NW India, which are used to infer variations in provenance, paleoclimate, and paleovegetation in the locality during the Late Quaternary. Aeolian sediments (~150 ka) in both the cores...... are overlain by fluvial sediments (~75 ka-recent). Major oxide compositions of the core sediments (n = 35) generally vary between that observed for the modern-day Ghaggar/Sutlej and Yamuna river sand. The isotopic composition (87Sr/86Sr: 0.7365 to 0.7783 and εNd: -14.6 to -19.0) of core sediments (n = 18......) suggest binary mixing of sediments from compositionally distinct Higher Himalaya (HH) and Lesser Himalaya (LH) endmembers in the catchment, and support involvement of a river system originating in the Himalayan hinterland. Distinctly higher 87Sr/86Sr and lower εNd in the core sediments during glacial...

  15. TRACEing Last Glacial Period (25-80 ka b2k) tephra horizons within North Atlantic marine cores and exploring links to the Greenland ice-cores

    Science.gov (United States)

    Abbott, P. M.; Davies, S. M.; Griggs, A. J.; Bourne, A. J.; Cook, E.; Pearce, N. J. G.; Austin, W. E. N.; Chapman, M.; Hall, I. R.; Purcell, C. S.; Scourse, J. D.; Rasmussen, T. L.

    2015-12-01

    Tephrochronology is a powerful technique for the correlation and synchronisation of disparate palaeoclimatic records from different depositional environments and has considerable potential for testing climatic phasing. For example, the relative timing of atmospheric and marine changes caused by the abrupt climatic events that punctuated the last glacial period within the North Atlantic region. Here we report on efforts to establish a framework of tephra horizons within North Atlantic marine sequences that can correlate these records and if traced in the Greenland ice-cores can act as isochronous tie-lines. Investigations have been conducted on a network of marine cores from a number of sites across the North Atlantic. Tephra horizons have been identified using cryptotephra extraction techniques more commonly applied to the study of terrestrial sequences. There are two main challenges with assessing cryptotephras in the glacial North Atlantic; i) determining the transportation processes and ii) assessing the influence of secondary reworking processes and the stratigraphic integrity of the isochrons. These processes and their influence are investigated for each cryptotephra using shard size variations, major element heterogeneity and co-variance of IRD input for some cores. Numerous Icelandic cryptophras have been successfully identified in the marine records and we will discuss the integration of a number of these with an isochronous nature into a marine tephra framework and how potential correlations to the Greenland ice-core tephra framework are determined. Spatial patterns in the nature of tephra records that are emerging from the core network will be highlighted to outline some of the key areas that could be explored in the future. In addition, the synchronisation of multiple North Atlantic records to the Greenland ice-cores using the North Atlantic Ash Zone II to test the synchroneity of an abrupt cooling in the North Atlantic will be discussed.

  16. Surface Ocean Radiocarbon Reservoir Ages From Land-Sea Tephra Correlation Constrains Deglacial Chronology and Ocean Circulation in the Southeast Bering Sea

    Science.gov (United States)

    Cook, M. S.; Miller, R.; White-Nockleby, C.; Chapman, A.; Mix, A. C.

    2017-12-01

    Radiocarbon estimates of the past ocean are valuable because unlike passive tracers, radiocarbon has the potential to trace both the distribution and rate of transport of water masses. Most studies using paired radiocarbon measurements on planktonic and benthic foraminifera assume that the surface reservoir age was constant at the preindustrial value, which if incorrect, can strongly bias radiocarbon reconstructions. The subarctic Pacific is ringed by volcanic arcs, and there is great potential to use tephrochronology as a stratigraphic tool in sediments from the last glacial and deglaciation, and assign calendar ages to the marine sediment without relying on calibrated planktonic radiocarbon ages. In this study, we use major and trace element analysis of volcanic glass to match tephras between radiocarbon-dated lake cores from Sanak Island in the eastern Aleutians to marine cores from Umnak Plateau in the southeast Bering Sea. There are numerous thin tephras preserved in laminated sediments from the Bolling-Allerod and early Holocene in marine cores from depths (1000-1500 m) within the modern oxygen minimum zone. We find that trace elements are crucial in distinguishing tephras from individual eruptions. Our preliminary radiocarbon measurements suggest that the benthic-atmosphere radiocarbon differences and marine surface reservoir ages in the Bolling-Allerod are similar to pre-industrial values, supporting previously published radiocarbon reconstructions from the region.

  17. A 1200-Year Record of Rapid Climate Changes Across the Tropical Americas Identified from Lake Sediments (Invited)

    Science.gov (United States)

    Abbott, M.; Rodbell, D. T.; Stansell, N.; Bird, B. W.; Vuille, M.

    2009-12-01

    Well-dated, highly resolved lake sediment stratigraphies from similar catchments across the tropical Americas provide a means to investigate the timing, rate and direction of climate variability as well as providing a way to evaluate whether rapid changes occur synchronously in both hemispheres. This presentation focuses on the last 1500 years from three new high-resolution stable isotope records including Yuraicocha (12°32'S, 75°29'W), Pumacocha (10°41'S, 76° 3'36W), and Gancho (8°27'N, 80°51'W). These lakes are all sensitive to changes in P/E and the sediment records respond at subdecadal timescales. Additionally, the results from these sites are compared with lake level records from Titicaca (16°14'S, 68°37'W) and Blanca (8°19'N, 71°46'W) as well as other lake core and speleothem records from the region. The results show that in general conditions are dry across South America from ~800 AD until ~1300 AD with wetter conditions in Central America and the Caribbean. This pattern of dry conditions in tropical South America and wet conditions in the north reverses after ~1300 when conditions become wetter in South America, and drier in Central America and the Carrabin.

  18. A quantitative x-ray diffraction inventory of volcaniclastic inputs into the marine sediment archives off Iceland: a contribution to the Volcanoes in the Arctic System programme

    Directory of Open Access Journals (Sweden)

    Dennis D. Eberl

    2013-02-01

    Full Text Available This paper re-evaluates how well quantitative x-ray diffraction (qXRD can be used as an exploratory method of the weight percentage (wt% of volcaniclastic sediment, and to identify tephra events in marine cores. In the widely used RockJock v6 software programme, qXRD tephra and glass standards include the rhyodacite White River tephra (Alaska, a rhyolitic tephra (Hekla-4 and the basaltic Saksunarvatn tephra. Experiments of adding known wt% of tephra to felsic bedrock samples indicated that additions ≥10 wt% are accurately detected, but reliable estimates of lesser amounts are masked by amorphous material produced by milling. Volcaniclastic inputs range between 20 and 50 wt%. Primary tephra events are identified as peaks in residual qXRD glass wt% from fourth-order polynomial fits. In cores where tephras have been identified by shard counts in the >150 µm fraction, there is a positive correlation (validation with peaks in the wt% glass estimated by qXRD. Geochemistry of tephra shards confirms the presence of several Hekla-sourced tephras in cores B997-317PC1 and -319PC2 on the northern Iceland shelf. In core B997-338 (north-west Iceland, there are two rhyolitic tephras separated by ca. 100 cm with uncorrected radiocarbon dates on articulated shells of around 13 000 yr B.P. These tephras may be correlatives of the Borrobol and Penifiler tephras found in Scotland. The number of Holocene tephra events per 1000 yr was estimated from qXRD on 16 cores and showed a bimodal distribution with an increased number of events in both the late and early Holocene.

  19. Pattern recognition on X-ray fluorescence records from Copenhagen lake sediments using principal component analysis

    DEFF Research Database (Denmark)

    Schreiber, Norman; Garcia, Emanuel; Kroon, Aart

    2014-01-01

    Principle Component Analysis (PCA) was performed on chemical data of two sediment cores from an urban fresh-water lake in Copenhagen, Denmark. X-ray fluorescence (XRF) core scanning provided the underlying datasets on 13 variables (Si, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Rb, Cd, Pb). Principle......, Fe, Rb) and characterized the content of minerogenic material in the sediment. In case of both cores, PC2 was a good descriptor emphasized as the contamination component. It showed strong linkages with heavy metals (Cu, Zn, Pb), disclosing changing heavy-metal contamination trends across different...

  20. Dust records in the Pleistocene sediments of Fraser Island: palaeoclimatic reconstruction of wind erosion over the last 600 ka

    International Nuclear Information System (INIS)

    Longmore, M.E.; McTainsh, G.H.

    1997-01-01

    Full text: Pleistocene lake sediments from a relic perched freshwater lake on Fraser Island have been found to date back to ca.600 ka using U/Th analysis of the organics. This sequence is one of the three longest terrestrial records of environmental change in Australia and the contained evidence of vegetation, fire and lake level changes (Longmore and Heijnis, 1996) and is an invaluable contribution to palaeoclimatic reconstruction. A younger sequence, dated by conventional radiocarbon analysis, has 6.5 m of continuous organic sedimentation from ca. 30 ka to the present. The last 8.5 ka has been analysed in detail, showing a mid-Holocene 'dry' period (Longmore, 1996). Continental aeolian dust from extreme wind erosional events has been measured in modern atmospheres (McTainsh, 1989; Knight et al., 1995) and deep sea cores (Hesse, 1994), but the terrestrial record of wind erosion during the Pleistocene is sparse. We will report on a pilot project to determine the presence of aeolian dust from extreme wind erosional events in the past in the sediments of Fraser Island lakes. Due to the highly weathered, well-sorted, siliceous nature of the dune sands forming the Island and the highly organic nature of the lake sediments (80-95% LOI), these are some of the few terrestrial sequences that permit separation of aeolian dust from local catchment materials. In the future, oxygen isotope and XRD analysis of the extracted dust will allow the most likely source of the entrained material to be determined and thus provide further evidence as to the wind regime during the last 600ka and 30ka respectively. The separation of dust from these terrestrial sequences is a major achievement and potentially may make a significant contribution to global palaeoclimatic models

  1. A multidisciplinary study of Holocene sediment records from Hjort Sø on Store Koldewey, Northeast Greenland

    NARCIS (Netherlands)

    Wagner, B.; Bennike, O.; Bos, J.A.A.; Cremer, H.; Lotter, A.F.; Melles, M.

    2008-01-01

    Two sediment cores of 70 and 252 cm length were recovered from Hjort Sø, a small lake on Store Koldewey, Northeast Greenland, and studied with a multidisciplinary approach in order to reconstruct the local environmental history and to test the relevance of proxies for paleoenvironmental information.

  2. Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

    NARCIS (Netherlands)

    DIjkstra, Nikki; Hagens, Mathilde; Egger, Matthias; Slomp, Caroline P.

    2018-01-01

    Phosphorus (P) concentrations in sediments are frequently used to reconstruct past environmental conditions in freshwater and marine systems, with high values thought to be indicative of a high biological productivity. Recent studies suggest that the post-depositional formation of vivianite, an

  3. Biochemical and stable carbon isotope records of mangrove derived organic matter in the sediment cores

    Digital Repository Service at National Institute of Oceanography (India)

    Manju, M.N.; Resmi, P.; RatheeshKumar, C.S.; Gireeshkumar, T.R.; Chandramohanakumar, N.; Joseph, M.M.

    in mangrove sediments. This also confirms the involvement of heterotrophic microorganisms in the organic carbon dynamics of the study area. The bulk elemental ratio (total organic carbon/total nitrogen) varied between 11.39 and 24.14 in the study region...

  4. Environmental record in detrital cave sediments in the Botovskaya and Dolganskaya Jama caves (Russian Federation)

    Czech Academy of Sciences Publication Activity Database

    Lisá, Lenka; Kadlec, Jaroslav; Chadima, Martin; Hercman, H.; Oberhansli, H.; Osincev, A.

    2006-01-01

    Roč. 8, - (2006), A10273-A10273 ISSN 1029-7006. [European Geosciences Union General Assembly. 02.04.2006-07.04.2006, Vienna] Institutional research plan: CEZ:AV0Z30130516 Keywords : cave * sediments * micromorphology * magnetic properties * provenance Subject RIV: DB - Geology ; Mineralogy http://www.cosis.net/abstracts/EGU06/10273/EGU06-J-10273-2.pdf

  5. Tephrostratigraphic studies on a sediment core from Lake Prespa in the Balkans

    Directory of Open Access Journals (Sweden)

    M. Damaschke

    2013-01-01

    Full Text Available A detailed tephrostratigraphic record, which dates back to Marine Isotope Stage (MIS 5b (ca. 91 kyr, has been established from a 17.76 m long core (Co1215 from Lake Prespa (Macedonia, Albania and Greece. A total of eleven tephra and cryptotephra layers (PT0915-1 to PT0915-11 were identified, using XRF scanning, magnetic susceptibility measurements, and macro- and microscopic inspection of the sediments. The major element composition of glass shards and/or micro-pumice fragments indicates that the tephras and cryptotephras originate from the explosive volcanism of Italy. Eight tephra and cryptotephra layers were correlated with specific volcanic eruptions: the AD 512 eruption of Somma-Vesuvius (1438 cal yr BP, the Mercato eruption of Somma-Vesuvius (8890 ± 90 cal yr BP, the Tufi Biancastri/LN1-LN2 eruption of the Campi Flegrei (14 749 ± 523 cal yr BP and 15 551 ± 621 cal yr BP, the SMP1-e/Y-3 eruption of the Campi Flegrei (30 000–31 000 cal yr BP, the Campanian Ignimbrite/Y-5 eruption of the Campi Flegrei (39 280 ± 110 cal yr BP, the SMP1-a event of Ischia Island (around 44 000 cal yr BP and the Green Tuff/Y-6 eruption of Pantelleria Island (around 45 000 cal yr BP. One tephra could be attributed to the volcanic activity of Mount Etna, but probably represents an unknown eruption at ca. 60 000 cal yr BP. Cryptotephras PT0915-6 and PT0915-10 remain unclassified so far, but according to the presented age-depth model these would have been deposited around 35 000 and 48 500 cal yr BP, respectively. Some of the tephras and cryptotephras are recognised for the first time in the Balkan region. The tephrostratigraphic work provides important information about ash dispersal and explosion patterns of source volcanoes and can be used to correlate and date geographically distant paleoenvironmental and archaeological archives in the central Mediterranean region. Moreover, the tephrostratigraphic work in combination with radiocarbon and electron spin

  6. Punctuated Sediment Input into Small Subpolar Ocean Basins During Heinrich Events and Preservation in the Stratigraphic Record

    Science.gov (United States)

    Hesse, R.

    2006-12-01

    generated from fresh-water discharges into the sea that can produce reversed buoyancy, as is well known from experiments. When the flows have traveled long enough, their tops will have lost enough sediment by settling such that their density decreases below that of the ambient seawater causing the current tops to lift up. The turbid fresh-water clouds buoyantly rise out of the turbidity current to a level of equal density, presumably the pycnocline, where they spread out laterally, even up-current, and generate interflows that deposit graded layers. The process is slow enough to allow incorporation into the graded layers of debris melting out of drifting icebergs. The observed lofted depositional facies is exclusively found in Heinrich layers. The most likely candidates for the parent currents from which lofting occurred were the sandy flows that formed the sand abyssal plain. Through this stratigraphic relationship the lofted facies ties the main pulses of Late Pleistocene sediment supply in the Labrador Basin to Heinrich events. Dating of pelagic interlayers during future ocean drilling may provide the proof that packages of sand turbidites underlying the abyssal plain are correlated to individual Heinrich events. The correlation may thus be documented in the stratigraphic record. Similar situations may exist in the Bering Sea or along the Maury Channel System in North Atlantic.

  7. Millennial-scale variations in dustiness recorded in Mid-Atlantic sediments from 0 to 70 ka

    Science.gov (United States)

    Middleton, Jennifer L.; Mukhopadhyay, Sujoy; Langmuir, Charles H.; McManus, Jerry F.; Huybers, Peter J.

    2018-01-01

    Sedimentary records of dust deposition in the subtropical Atlantic provide important constraints on millennial- and orbital-scale variability in atmospheric circulation and North African aridity. Constant flux proxies, such as extraterrestrial helium-3, yield dust flux records that are independent of the biases caused by lateral sediment transport and limited resolution that may be associated with age-model-derived mass accumulation rates. However, Atlantic dust records constrained using constant flux proxies are sparsely distributed and generally limited to the past 20 ka. Here we extend the Atlantic record of North African dust deposition to 70 ka using extraterrestrial helium-3 and measurements of titanium, thorium, and terrigenous helium-4 in two sediment cores collected at 26°N and 29°N on the Mid-Atlantic Ridge and compare results to model estimates for dust deposition in the subtropical North Atlantic. Dust proxy fluxes between 26°N and 29°N are well correlated, despite variability in lateral sediment transport, and underscore the utility of extraterrestrial helium-3 for constraining millennial-scale variability in dust deposition. Similarities between Mid-Atlantic dust flux trends and those observed along the Northwest African margin corroborate previous interpretations of dust flux variability over the past 20 ka and suggest that long distance transport and depositional processes do not overly obscure the signal of North African dust emissions. The 70 ka Mid-Atlantic record reveals a slight increase in North African dustiness from Marine Isotope Stage 4 through the Last Glacial Maximum and a dramatic decrease in dustiness associated with the African Humid Period. On the millennial-scale, the new records exhibit brief dust maxima coincident with North Atlantic cold periods such as the Younger Dryas, and multiple Heinrich Stadials. The correlation between Mid-Atlantic dust fluxes and previous constraints on North African aridity is high. However

  8. Effect of recent climate change on Arctic Pb pollution: a comparative study of historical records in lake and peat sediments.

    Science.gov (United States)

    Liu, Xiaodong; Jiang, Shan; Zhang, Pengfei; Xu, Liqiang

    2012-01-01

    Historical changes of anthropogenic Pb pollution were reconstructed based on Pb concentrations and isotope ratios in lake and peat sediment profiles from Ny-Ålesund of Arctic. The calculated excess Pb isotope ratios showed that Pb pollution largely came from west Europe and Russia. The peat profile clearly reflected the historical changes of atmospheric deposition of anthropogenic Pb into Ny-Ålesund, and the result showed that anthropogenic Pb peaked at 1960s-1970s, and thereafter a significant recovery was observed by a rapid increase of (206)Pb/(207)Pb ratios and a remarkable decrease in anthropogenic Pb contents. In contrast to the peat record, the longer lake record showed relatively high anthropogenic Pb contents and a persistent decrease of (206)Pb/(207)Pb ratios within the uppermost samples, suggesting that climate-sensitive processes such as catchment erosion and meltwater runoff might have influenced the recent change of Pb pollution record in the High Arctic lake sediments. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Century-scale high-resolution black carbon records in sediment cores from the South Yellow Sea, China

    Science.gov (United States)

    Xu, Xiaoming; Hong, Yuehui; Zhou, Qianzhi; Liu, Jinzhong; Yuan, Lirong; Wang, Jianghai

    2018-01-01

    Black carbon (BC) has received increasing attention in the last 20 years because it is not only an absorbent of toxic pollutants but also a greenhouse substance, preserving fire-history records, and more importantly, acting as an indicator of biogeochemical cycles and global changes. By adopting an improved chemothermal oxidation method (WXY), this study reconstructed the century-scale high-resolution records of BC deposition from two fine-grained sediment cores collected from the Yellow Sea Cold Water Mass in the South Yellow Sea. The BC records were divided into five stages, which exhibited specific sequences with three BC peaks at approximately 1891, 1921, and 2007 AD, representing times at which the first heavy storms appeared just after the termination of long-term droughts. The significant correlation between the times of the BC peaks in the cores and heavy storms in the area of the Huanghe (Yellow) River demonstrated that BC peaks could result from markedly strengthened sedimentation due to surface runoff, which augmented the atmospheric deposition. Stable carbon isotope analysis indicated that the evident increase in carbon isotope ratios of BC in Stage 5 might have resulted from the input of weathered rock-derived graphitic carbon cardinally induced by the annual anthropogenic modulation of water-borne sediment in the Huanghe River since 2005 AD. Numerical calculations demonstrated that the input fraction of graphitic carbon was 22.97% for Stage 5, whereas no graphitic carbon entered during Stages 1 and 3. The obtained data provide new and important understanding of the source-sink history of BC in the Yellow Sea.

  10. Distribution and mass of tephra-fall deposits from volcanic eruptions of Sakurajima Volcano based on posteruption surveys

    Science.gov (United States)

    Oishi, Masayuki; Nishiki, Kuniaki; Geshi, Nobuo; Furukawa, Ryuta; Ishizuka, Yoshihiro; Oikawa, Teruki; Yamamoto, Takahiro; Nanayama, Futoshi; Tanaka, Akiko; Hirota, Akinari; Miwa, Takahiro; Miyabuchi, Yasuo

    2018-04-01

    We estimate the total mass of ash fall deposits for individual eruptions of Sakurajima Volcano, southwest Japan based on distribution maps of the tephra fallout. Five ash-sampling campaigns were performed between 2011 and 2015, during which time Sakurajima continued to emit ash from frequent Vulcanian explosions. During each survey, between 29 and 53 ash samplers were installed in a zone 2.2-43 km downwind of the source crater. Total masses of erupted tephra were estimated using several empirical methods based on the relationship between the area surrounded by a given isopleth and the thickness of ash fall within each isopleth. We obtained 70-40,520 t (4.7 × 10-8-2.7 × 10-5-km3 DRE) as the minimum estimated mass of erupted materials for each eruption period. The minimum erupted mass of tephra produced during the recorded events was calculated as being 890-5140 t (5.9 × 10-7-3.6 × 10-6-km3 DRE). This calculation was based on the total mass of tephra collected during any one eruptive period and the number of eruptions during that period. These values may thus also include the contribution of continuous weak ash emissions before and after prominent eruptions. We analyzed the meteorological effects on ash fall distribution patterns and concluded that the width of distribution area of an ash fall is strongly controlled by the near-ground wind speed. The direction of the isopleth axis for larger masses is affected by the local wind direction at ground level. Furthermore, the wind direction influences the direction of the isopleth axes more at higher altitude. While a second maximum of ash fall can appear, the influence of rain might only affect the finer particles in distal areas.

  11. Spatiotemporal climatic, hydrological, and environmental variations based on records of annually laminated lake sediments from northern Poland

    Science.gov (United States)

    Tylmann, W.; Blanke, L.; Kinder, M.; Loewe, T.; Mayr, C.; Ohlendorf, C.; Zolitschka, B.

    2009-12-01

    In northern Poland there is the unique opportunity to compare varved lake sediment records with distinct climatic trends along a 700 km long W-E transect. Annually laminated Holocene sediment sequences from Lake Lubinskie, Lake Suminko, Lake Lazduny, and Lake Szurpily were cored for high-resolution multiproxy climate and environmental reconstruction in the framework of the Polish-German project “Northern Polish Lake Research” (NORPOLAR). First results from a 139 cm long gravity core of Lake Lazduny (53°51.4’N, 21°57.3’E) document deposition of an organic (mean organic matter: 13.9%; mean biogenic opal: 9.8%) and highly carbonaceous gyttja (mean calcite content: 61.6%). The finely laminated sediment consists of biochemical varves. Pale spring/summer layers composed of autochthonous carbonates alternate with dark fall/winter layers made of organic and minerogenic detritus. The established chronology for the last 1500 calendar-years is based on thin section analysis supported by independent radiometric dating (C-14, Pb-210). Sedimentological, geochemical and stable isotope analyses were carried out with a decadal temporal resolution. Additionally, non-destructive and high-resolution XRF scanning data reveal a rhythmic variation in the Ca content that reflects seasonal calcite deposition. Redox-sensitive elements like Fe, Mn and S are interpreted to be the response to mean winter temperatures: colder winter temperatures → extended lake ice cover → intensification of meromixis → increased Fe/Mn ratio. In turn, these parameters can be linked to NAO (North Atlantic Oscillation) variability, because a negative NAO is related to colder and drier conditions in northeastern Europe. Climate variability is also mirrored by the δ13C record of the endogenic calcite fraction. In mid-latitude lakes calcite precipitation is dominated by productivity-controlled consumption of the dissolved inorganic carbon (DIC) pool. Thus the δ13C record potentially provides a

  12. Paleoenvironmental record in Lake Baikal sediments: Environmental changes in the last 160 ky

    Czech Academy of Sciences Publication Activity Database

    Grygar, Tomáš; Kadlec, Jaroslav; Pruner, Petr; Swann, G.; Bezdička, Petr; Hradil, David; Lang, Kamil; Novotná, Kateřina; Oberhänsli, H.

    2006-01-01

    Roč. 237, 2-4 (2006), s. 240-254 ISSN 0031-0182 R&D Projects: GA MŠk(CZ) LN00A028; GA AV ČR IAA3032401 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z30130516 Keywords : lake sediments * climate change * spectroscopy Subject RIV: CA - Inorganic Chemistry Impact factor: 1.822, year: 2006

  13. Sensitivity of sediment magnetic records to climate change during Holocene for the northern South China Sea

    Science.gov (United States)

    Ouyang, Tingping; Li, Mingkun; Zhao, Xiang; Zhu, Zhaoyu; Tian, Chengjing; Qiu, Yan; Peng, Xuechao; Hu, Qiao

    2016-05-01

    Magnetic property has been proved to be a sensitive proxy to climate change for both terrestrial and marine sediments. Based on the schedule frame established by AMS 14C dating of foraminifera, detail magnetic analyses were performed for core PC24 sediments at sampling intervals of 2 cm to discuss magnetic sensitivity of marine sediment to climate during Holocene for the northern South China Sea. The results indicated that: 1) Concentration dependent magnetic parameters are positive corresponding to variation of temperature. The frequency dependent susceptibility coefficient basically reflected the variation in humidity; 2) XARM/SIRM was more sensitive to detrital magnetite particles and SIRM/X was more effective to biogenic magnetite particles. Variations of XARM/SIRM and SIRM/X are corresponding to precipitation and temperature, respectively; 3) the Holocene Megathermal in the study area was identified as 7.5-3.4 cal. ka BP. The warmest stage of Holocene for the study area should be during 6.1 to 3.9 cal. ka BP; 4) The 8 ka cold event was characterized as cold and dry during 8.55 to 8.25 cal. ka BP; 5) During early and middle Holocene, the climate combinations were warm dry and cold wet. It turned to warm and wet after 2.7 cal. ka BP.

  14. Sensitivity of sediment magnetic records to climate change during Holocene for the northern South China Sea

    Directory of Open Access Journals (Sweden)

    Tingping eOuyang

    2016-05-01

    Full Text Available Magnetic property has been proved to be a sensitive proxy to climate change for both terrestrial and marine sediments. Based on the schedule frame established by AMS 14C dating of foraminifera, detail magnetic analyses were performed for core PC24 sediments at sampling intervals of 2 cm to discuss magnetic sensitivity of marine sediment to climate during Holocene for the northern South China Sea. The results indicated that: 1 Concentration dependent magnetic parameters are positive corresponding to variation of temperature. The frequency dependent susceptibility coefficient basically reflected the variation in humidity; 2 XARM/SIRM was more sensitive to detrital magnetite particles and SIRM/X was more effective to biogenic magnetite particles. Variations of XARM/SIRM and SIRM/X are corresponding to precipitation and temperature, respectively; 3 the Holocene Megathermal in the study area was identified as 7.5-3.4 cal. ka BP. The warmest stage of Holocene for the study area should be during 6.1 to 3.9 cal. ka BP; 4 The 8 ka cold event was characterized as cold and dry during 8.55 to 8.25 cal. ka BP; 5 During early and middle Holocene, the climate combinations were warm dry and cold wet. It turned to warm and wet after 2.7 cal. ka BP.

  15. Environmental legacy of copper metallurgy and Mongol silver smelting recorded in Yunnan Lake sediments.

    Science.gov (United States)

    Hillman, Aubrey L; Abbott, Mark B; Yu, JunQing; Bain, Daniel J; Chiou-Peng, TzeHuey

    2015-03-17

    Geochemical measurements on well-dated sediment cores from Lake Er (Erhai) are used to determine the timing of changes in metal concentrations over 4500 years in Yunnan, a borderland region in southwestern China noted for rich mineral deposits but with inadequately documented metallurgical history. Our findings add new insight into the impacts and environmental legacy of human exploitation of metal resources in Yunnan history. We observe an increase in copper at 1500 BC resulting from atmospheric emissions associated with metallurgy. These data clarify the chronological issues related to links between the onset of Yunnan metallurgy and the advent of bronze technology in adjacent Southeast Asia, subjects that have been debated for nearly half a century. We also observe an increase from 1100 to 1300 AD in a number of heavy metals including lead, silver, zinc, and cadmium from atmospheric emissions associated with silver smelting. Culminating during the rule of the Mongols, known as the Yuan Dynasty (1271-1368 AD), these metal concentrations approach levels three to four times higher than those from industrialized mining activity occurring within the catchment today. Notably, the concentrations of lead approach levels at which harmful effects may be observed in aquatic organisms. The persistence of this lead pollution over time created an environmental legacy that likely contributes to known issues in modern day sediment quality. We demonstrate that historic metallurgical production in Yunnan can cause substantial impacts on the sediment quality of lake systems, similar to other paleolimnological findings around the globe.

  16. Isotopic chemical weathering behaviour of Pb derived from a high-Alpine Holocene lake-sediment record

    Science.gov (United States)

    Gutjahr, Marcus; Süfke, Finn; Gilli, Adrian; Anselmetti, Flavio; Glur, Lukas; Eisenhauer, Anton

    2017-04-01

    Several studies assessing the chemical weathering systematics of Pb isotopes provided evidence for the incongruent release of Pb from source rocks during early stages of chemical weathering, resulting in runoff compositions more radiogenic (higher) than the bulk source-rock composition [e.g. 1]. Deep NW Atlantic seawater Pb isotope records covering the last glacial-interglacial transition further support these findings. Clear excursions towards highly radiogenic Pb isotopic input in the deep NW Atlantic seen during the early Holocene, hence after the large-scale retreat of the Laurentide Ice Sheet in North America, are interpreted to be controlled by preferential release of radiogenic Pb from U- and Th-rich mineral phases during early stages of chemical weathering that are less resistant to chemical dissolution than other rock-forming mineral phases [2-4]. To date, however, no terrestrial Pb isotope record exists that could corroborate the evidence from deep marine sites for efficient late deglacial weathering and washout of radiogenic Pb. We present a high-resolution adsorbed Pb isotope record from a sediment core retrieved from Alpine Lake Grimsel (1908 m.a.s.l.) in Switzerland, consisting of 117 Pb compositions over the past 10 kyr. This high-Alpine study area is ideally located for incipient and prolonged chemical weathering studies. The method used to extract the adsorbed lake Pb isotope signal is identical to previous marine approaches targeting the authigenic Fe-Mn oxyhydroxides fraction within the lake sediments [5, 6]. The Pb isotope compositions are further accompanied by various elemental ratios derived from the same samples that equally trace climatic boundary conditions in the Grimsel Lake area. The Pb isotopic composition recorded in Lake Grimsel is remarkably constant throughout the majority of the Holocene until ˜2.5 ka BP, despite variable sediment composition and -age, and isotopically relatively close to the signature of the granitic source rock

  17. Multi-elemental contamination and historic record in sediments from the Santos-Cubatao Estuarine System, Brazil

    International Nuclear Information System (INIS)

    Luiz-Silva, Wanilson; Machado, Wilson; Matos, Rosa H.R.

    2008-01-01

    This paper records for the first time the contamination history and identifies the sources of 38 elements in sediments from the Santos-Cubatao Estuarine System (SE Brazil), at one of the most industrialized areas in Latin America. The compositions of samples from a 260 cm long sediment core collected in the Morrao River estuary were determined by ICP-MS. Enrichment factors, principal component analysis, correlation matrixes, and the characterization of geochemical signatures permitted a consistent data evaluation. Contaminant elements such as Cr, Mn, Ni, Zn, Ga, Ag, Cd, Sn, Sb, Pb, and Bi were associated with steel plant-derived Fe concentrations, while Be, Ca, Sc, Co, Cu, Sr, Y, Zr, Nb, Hf, Ta, Th, and U were associated with fertilizer industry-derived P concentrations. An overlap of sedimentary Fe distribution and local steel plant production indicated that Fe is a reliable marker of the contamination history, allowing the estimation of sedimentation rates over a period of 45 years of industrial activities. (author)

  18. Fallout isotope chronology of the near-surface sediment record of Lake Bolătău.

    Science.gov (United States)

    Bihari, Árpád; Karlik, Máté; Mîndrescu, Marcel; Szalai, Zoltán; Grădinaru, Ionela; Kern, Zoltán

    2018-01-01

    Fallout isotope ( 210 Pb ex, 137 Cs and 241 Am) based dating has been carried out on the near-surface sediment core collected from Lake Bolătău-Feredeu (Bukovina, Romania). The motivation was to improve the chronology of this recent section in connection with significant fluctuations observed in sediment accumulation rates, particle size distribution and primordial radioisotope (i.e. 40 K and 232 Th) composition. Previously only an extrapolation of a broad-range OxCal age-depth model, which was based on 8 AMS radiocarbon dates from the deeper part of a parallel sediment sequence and tentatively validated for the upper part using the double peaks of the 137 Cs activity concentration distribution, was available for the studied section (1-24 cm). Parallel to the previous 137 Cs measurement, 210 Pb and 226 Ra (for a more detailed, 210 Pb ex -based chronology), 241 Am (for an additional time-marker), as well as 40 K and 232 Th concentrations have also been determined by gamma-spectrometry. In case of the 210 Pb ex -based chronology, due to a large deviation from a pure exponential distribution, the Constant Flux (CF) model has been used for the calculation of sediment ages and accumulation rates. Although the broad-range OxCal and the CF model were broadly similar down to 22 cm, the 210 Pb ex -based ages are clearly superior in terms of uncertainty in the uppermost 12 cm, while the broad-range model has smaller uncertainty below 20 cm (>150 years). The CF model gave an average mass accumulation rate of (0.08 ± 0.03) g cm -2 yr -1 for sections 0-11 cm, and (0.03 ± 0.01) g cm -2 yr -1 for sections 12-22 cm, respectively. Significant changes have been observed in the depth distribution of both the particle size distribution and the elemental/isotopic composition of the sediment record, most likely related to the variation observable in the intensity and volume of precipitation in the catchment. The obtained high-resolution records of Lake Bolătău, including

  19. Lead isotope ratios in six lake sediment cores from Japan Archipelago: Historical record of trans-boundary pollution sources

    International Nuclear Information System (INIS)

    Hosono, Takahiro; Alvarez, Kelly; Kuwae, Michinobu

    2016-01-01

    Sediment cores from six lakes situated from north to south on the Japanese Archipelago were collected during 2009–2010 to investigate the hypothesis that deposition of lead (Pb) was coming from East Asia (including China, South Korea and eastern part of Russia). Accumulation rates and ages of the lake sediment were estimated by the "2"1"0Pb constant rate of supply model and "1"3"7Cs inputs to reconstruct the historical trends of Pb accumulation. Cores from four lakes located in the north and central Japan, showed clear evidence of Pb pollution with a change in the "2"0"6Pb/"2"0"7Pb and "2"0"8Pb/"2"0"7Pb ratios in the recent sediment as compared to the deeper sediment. Among the six studied lakes, significant inputs of anthropogenic lead emissions were observed at Lake Mikazuki (north Hokkaido in north Japan), Lake Chokai (north of Honshu), and Lake Mikuriga (central part of Honshu). Pb isotopic comparison of collected core sediment and previously reported data for wet precipitation and aerosols from different Asian regions indicate that, before 1900, Pb accumulated in these three lakes was not affected by trans-boundary sources. Lake Mikazuki started to receive Pb emissions from Russia in early 1900s, and during the last two decades, this lake has been affected by trans-boundary Pb pollution from northern China. Lake Chokai has received Pb pollutant from northern China since early 1900s until 2009, whereas for the Lake Mikuriga the major Pb contaminant was transported from southern China during the past 100 years. The results of our study demonstrate that Japan Archipelago has received trans-boundary Pb emissions from different parts of East Asian region depending on location, and the major source region has changed historically. - Highlights: • Historical trend of Pb pollution was recorded in six Japanese Lakes. • Pb concentration and Pb isotope ratios were determined for sediment cores. • High [Pb] and less radiogenic Pb isotope ratios were observed since

  20. Lead isotope ratios in six lake sediment cores from Japan Archipelago: Historical record of trans-boundary pollution sources

    Energy Technology Data Exchange (ETDEWEB)

    Hosono, Takahiro, E-mail: hosono@kumamoto-u.ac.jp [Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Alvarez, Kelly [Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Kuwae, Michinobu [Senior Research Fellow Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)

    2016-07-15

    Sediment cores from six lakes situated from north to south on the Japanese Archipelago were collected during 2009–2010 to investigate the hypothesis that deposition of lead (Pb) was coming from East Asia (including China, South Korea and eastern part of Russia). Accumulation rates and ages of the lake sediment were estimated by the {sup 210}Pb constant rate of supply model and {sup 137}Cs inputs to reconstruct the historical trends of Pb accumulation. Cores from four lakes located in the north and central Japan, showed clear evidence of Pb pollution with a change in the {sup 206}Pb/{sup 207}Pb and {sup 208}Pb/{sup 207}Pb ratios in the recent sediment as compared to the deeper sediment. Among the six studied lakes, significant inputs of anthropogenic lead emissions were observed at Lake Mikazuki (north Hokkaido in north Japan), Lake Chokai (north of Honshu), and Lake Mikuriga (central part of Honshu). Pb isotopic comparison of collected core sediment and previously reported data for wet precipitation and aerosols from different Asian regions indicate that, before 1900, Pb accumulated in these three lakes was not affected by trans-boundary sources. Lake Mikazuki started to receive Pb emissions from Russia in early 1900s, and during the last two decades, this lake has been affected by trans-boundary Pb pollution from northern China. Lake Chokai has received Pb pollutant from northern China since early 1900s until 2009, whereas for the Lake Mikuriga the major Pb contaminant was transported from southern China during the past 100 years. The results of our study demonstrate that Japan Archipelago has received trans-boundary Pb emissions from different parts of East Asian region depending on location, and the major source region has changed historically. - Highlights: • Historical trend of Pb pollution was recorded in six Japanese Lakes. • Pb concentration and Pb isotope ratios were determined for sediment cores. • High [Pb] and less radiogenic Pb isotope ratios

  1. Syndepositional tectonics recorded by soft-sediment deformation and liquefaction structures (continental Lower Permian sediments, Southern Alps, Northern Italy): Stratigraphic significance

    Science.gov (United States)

    Berra, F.; Felletti, F.

    2011-04-01

    The Lower Permian succession of the Central Southern Alps (Lombardy, Northern Italy) was deposited in fault-controlled continental basins, probably related to transtensional tectonics. We focussed our study on the stratigraphic record of the Lower Permian Orobic Basin, which consists of a 1000 m thick succession of prevailing continental clastics with intercalations of ignimbritic flows and tuffs (Pizzo del Diavolo Formation, PDV) resting on the underlying prevailing pyroclastic flows of the Cabianca Volcanite. The PDV consists of a lower part (composed of conglomerates passing laterally to sandstones and distally to silt and shales), a middle part (pelitic, with carbonates) and an upper part (alternating sandstone, silt and volcanic flows). Syndepositional tectonics during the deposition of the PDV is recorded by facies distribution, thickness changes and by the presence of deformation and liquefaction structures interpreted as seismites. Deformation is recorded by both ductile structures (ball-and-pillow, plastic intrusion, disturbed lamination, convolute stratification and slumps) and brittle structures (sand dykes and autoclastic breccias). Both the sedimentological features and the geodynamic setting of the depositional basin confidently support the interpretation of the described deformation features as related to seismic shocks. The most significant seismically-induced deformation is represented by a slumped horizon (about 4 m thick on average) which can be followed laterally for more than 5 km. The slumped bed consists of playa-lake deposits (alternating pelites and microbial carbonates, associated with mud cracks and vertebrate tracks). The lateral continuity and the evidence of deposition on a very low-angle surface along with the deformation/liquefaction of the sediments suggest that the slump was triggered by a high-magnitude earthquake. The stratigraphic distribution of the seismites allows us to identify time intervals of intense seismic activity

  2. Using lead isotopes and trace element records from two contrasting Lake Tanganyika sediment cores to assess watershed – Lake exchange

    Science.gov (United States)

    Odigie, Kingsley; Cohen, A.D.; Swarzenski, Peter W.; Flegal, R

    2014-01-01

    Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815–1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements – likely caused by changes in land use – over that period. For example, the flux of Pb increased by ∼300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r = 0.77–0.99, p factors (EF operations within the lake’s watershed over the past century. The data also indicate that the mid-lake site is a much more sensitive and useful recorder of environmental changes than the nearshore site. Furthermore, the lead isotopic compositions of sediment at the sites differed spatially, indicating that the Pb (and other trace elements by association) originated from different natural sources at the two locations.

  3. Biomarker and stable carbon isotopic signatures for 100–200 year sediment record in the Chaihe catchment in southwest China

    International Nuclear Information System (INIS)

    Wang, Yanhua; Yang, Hao; Zhang, Jixiang; Xu, Meina; Wu, Changbin

    2015-01-01

    Natural inputs and anthropogenic influences on lakes and their catchments are reflected in the sediment record. In the present study, the extractable organic compounds from sediments in the Chaihe catchment of the Dianchi watershed were analyzed to characterize source inputs. Results show that the sediments are dominated by odd numbered n-alkanes (n-C 16 –n-C 33 ), maximizing at n-C 17 , n-C 29 and n-C 31 . Aliphatic hydrocarbon may be composed of terrestrial plants and bacteria. The values of δ 13 C 27 , δ 13 C 29 and δ 13 C 31 of n-alkanes exhibit a range from − 33.27‰ to − 25.46‰, from − 35.76‰ to − 28.47‰ and from − 33.67‰ to − 27.42‰, respectively and three records strongly covary with depth, falling within the range of C 3 plants in the study area. An isotopic model revealed C 3 plant contribution to sedimentary organic matter (OM) ranging from 40.75% to 97.22%. The values of ACL 27–33 , CPI 27–33 , OEP, Paq, Pr/Ph, (C 27 + C 29 )/2C 31 , (C 21 + C 23 + C 25 )/3C 17 and nC 26 − /nC 27 + are consistent with the C 3 plant predominance. A constant CRS model gave the accumulation rates ranging from 2.69 to 8.46 mm a −1 spanning 1885–2010. It was concluded that OM transport in the Chaihe catchment was influenced strongly by human activities resulting in enhanced eutrophication. - Highlights: • Strong predominance of odd-numbered n-alkanes maximized at n-C 17 , n-C 29 and n-C 31 • Sedimentary OM in the Chaihe catchment was deduced mainly from C 3 plants. • Human activities enhanced OM transport, resulting in worse ecosystem

  4. Morava River flood plain sediments deposited during the last millennium: Climatic and anthropogenic record

    Czech Academy of Sciences Publication Activity Database

    Kadlec, Jaroslav; Grygar, Tomáš; Světlík, Ivo; Ettler, V.; Mihaljevič, M.; Diehl, J.; Beske-Diehl, S.

    2008-01-01

    Roč. 34, 4/6 (2008), s. 1338314-1338314 ISSN 0161-6951. [International Geological Congress /33./. 06.08.2008-14.08.2008, Oslo ] R&D Projects: GA AV ČR IAA300130505; GA AV ČR IAA3013201; GA AV ČR IAAX00130801 Institutional research plan: CEZ:AV0Z30130516; CEZ:AV0Z40320502; CEZ:AV0Z10480505 Keywords : Morava River * flood * plain sediments * magnetic minerals Subject RIV: DB - Geology ; Mineralogy

  5. A comparison of sedimentary DNA and pollen from lake sediments in recording vegetation composition at the Siberian treeline.

    Science.gov (United States)

    Niemeyer, Bastian; Epp, Laura S; Stoof-Leichsenring, Kathleen R; Pestryakova, Luidmila A; Herzschuh, Ulrike

    2017-11-01

    Reliable information on past and present vegetation is important to project future changes, especially for rapidly transitioning areas such as the boreal treeline. To study past vegetation, pollen analysis is common, while current vegetation is usually assessed by field surveys. Application of detailed sedimentary DNA (sedDNA) records has the potential to enhance our understanding of vegetation changes, but studies systematically investigating the power of this proxy are rare to date. This study compares sedDNA metabarcoding and pollen records from surface sediments of 31 lakes along a north-south gradient of increasing forest cover in northern Siberia (Taymyr peninsula) with data from field surveys in the surroundings of the lakes. sedDNA metabarcoding recorded 114 plant taxa, about half of them to species level, while pollen analyses identified 43 taxa, both exceeding the 31 taxa found by vegetation field surveys. Increasing Larix percentages from north to south were consistently recorded by all three methods and principal component analyses based on percentage data of vegetation surveys and DNA sequences separated tundra from forested sites. Comparisons of the ordinations using procrustes and protest analyses show a significant fit among all compared pairs of records. Despite similarities of sedDNA and pollen records, certain idiosyncrasies, such as high percentages of Alnus and Betula in all pollen and high percentages of Salix in all sedDNA spectra, are observable. Our results from the tundra to single-tree tundra transition zone show that sedDNA analyses perform better than pollen in recording site-specific richness (i.e., presence/absence of taxa in the vicinity of the lake) and perform as well as pollen in tracing vegetation composition. © 2017 John Wiley & Sons Ltd.

  6. Lake sediments record prehistoric lead pollution related to early copper production in North America.

    Science.gov (United States)

    Pompeani, David P; Abbott, Mark B; Steinman, Byron A; Bain, Daniel J

    2013-06-04

    The mining and use of copper by prehistoric people on Michigan's Keweenaw Peninsula is one of the oldest examples of metalworking. We analyzed the concentration of lead, titanium, magnesium, iron, and organic matter in sediment cores recovered from three lakes located near mine pits to investigate the timing, location, and magnitude of ancient copper mining pollution. Lead concentrations were normalized to lithogenic metals and organic matter to account for processes that can influence natural (or background) lead delivery. Nearly simultaneous lead enrichments occurred at Lake Manganese and Copper Falls Lake ∼8000 and 7000 years before present (yr BP), indicating that copper extraction occurred concurrently in at least two locations on the peninsula. The poor temporal coherence among the lead enrichments from ∼6300 to 5000 yr BP at each lake suggests that the focus of copper mining and annealing shifted through time. In sediment younger than ∼5000 yr BP, lead concentrations remain at background levels at all three lakes, excluding historic lead increases starting ∼150 yr BP. Our work demonstrates that lead emissions associated with both the historic and Old Copper Complex tradition are detectable and can be used to determine the temporal and geographic pattern of metal pollution.

  7. Anoxic sediments off Central Peru record interannual to multidecadal changes of climate and upwelling ecosystem during the last two centuries

    Science.gov (United States)

    Gutiérrez, D.; Sifeddine, A.; Reyss, J. L.; Vargas, G.; Velazco, F.; Salvatteci, R.; Ferreira, V.; Ortlieb, L.; Field, D.; Baumgartner, T.; Boussafir, M.; Boucher, H.; Valdés, J.; Marinovic, L.; Soler, P.; Tapia, P.

    2006-01-01

    High-resolution paleo-environmental and paleo-ecological archives in laminated sequences are present in selected areas from the upper continental Peruvian margin within the oxygen minimum zone. We present initial results of a multidisciplinary study (the PALEOPECES project) that aims to reconstruct environmental and ecosystem variability during the past 200 years from high-resolution records. We report chronology development, sediment structure, elemental, organic, and mineralogical compositions of a box core collected at 300 m depth off Pisco, central Peru. An average sedimentation rate of 2.2 mm y-1 was estimated from downcore excess 210Pb activities for the last 100-150 years. Extending this rate further downcore indicates that a slump located at 52 cm depth from the top of the core can be correlated with a large tsunami that struck the coast of central Peru in 1746. X-ray analyses reveal laminated structures composed of couplets of light and dark laminae. Observations under polarized microscope show that light laminae are dominated by more dense, detrital and terrigenous material, while dark laminae are less dense with greater concentrations of amorphous biogenic silica. Downcore variations in dry bulk density and X-ray radioscopy of gray level show similar patterns, including a major shift at 34 cm depth (ca. mid-nineteenth century). A finely laminated sequence, which may include annual varves, is present between 34 cm depth and the slump layer. Sediment characteristics of the sequence suggest increased seasonality of terrigenous versus biogenous sedimentation during the corresponding period. In addition to a mid-nineteenth century change and considerable multidecadal variability in TOC, there is a positive trend in the past 50 years. Mineralogical analyses from a Fourier Transformed Infrared Spectroscopy (FTIR) of the upper core covering the last 25 years, indicate higher concentrations of the mineral fraction (quartz, feldspar, kaolinite and illite) in

  8. Anoxic sediments off Central Peru record interannual to multidecadal changes of climate and upwelling ecosystem during the last two centuries

    Directory of Open Access Journals (Sweden)

    D. Gutiérrez

    2006-01-01

    Full Text Available High-resolution paleo-environmental and paleo-ecological archives in laminated sequences are present in selected areas from the upper continental Peruvian margin within the oxygen minimum zone. We present initial results of a multidisciplinary study (the PALEOPECES project that aims to reconstruct environmental and ecosystem variability during the past 200 years from high-resolution records. We report chronology development, sediment structure, elemental, organic, and mineralogical compositions of a box core collected at 300 m depth off Pisco, central Peru. An average sedimentation rate of 2.2 mm y-1 was estimated from downcore excess 210Pb activities for the last 100-150 years. Extending this rate further downcore indicates that a slump located at 52 cm depth from the top of the core can be correlated with a large tsunami that struck the coast of central Peru in 1746. X-ray analyses reveal laminated structures composed of couplets of light and dark laminae. Observations under polarized microscope show that light laminae are dominated by more dense, detrital and terrigenous material, while dark laminae are less dense with greater concentrations of amorphous biogenic silica. Downcore variations in dry bulk density and X-ray radioscopy of gray level show similar patterns, including a major shift at 34 cm depth (ca. mid-nineteenth century. A finely laminated sequence, which may include annual varves, is present between 34 cm depth and the slump layer. Sediment characteristics of the sequence suggest increased seasonality of terrigenous versus biogenous sedimentation during the corresponding period. In addition to a mid-nineteenth century change and considerable multidecadal variability in TOC, there is a positive trend in the past 50 years. Mineralogical analyses from a Fourier Transformed Infrared Spectroscopy (FTIR of the upper core covering the last 25 years, indicate higher concentrations of the mineral fraction (quartz, feldspar, kaolinite and

  9. Temporal record of Pu isotopes in inter-tidal sediments from the northeastern Irish Sea

    Energy Technology Data Exchange (ETDEWEB)

    Lindahl, Patric, E-mail: patriclindahl@yahoo.com [School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Worsfold, Paul; Keith-Roach, Miranda [School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Andersen, Morten B. [Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ (United Kingdom); Kershaw, Peter; Leonard, Kins [The Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Suffolk NR33 0HT (United Kingdom); Choi, Min-Seok [Division of Earth and Environmental Science, Korea Basic Science Institute, 113 Gwahangno, Yusung-gu, Daejon 305-333 (Korea, Republic of); Boust, Dominique [Laboratoire de Radioecologie, Institut de Radioprotection et de Surete Nucleaire, BP 10, 50130 Cherbourg-Octeville (France); Lesueur, Patrick [University of Caen Basse Normandie, M2C UMR CNRS 6143, 14000 Caen (France)

    2011-11-01

    A depth profile of {sup 239}Pu and {sup 240}Pu specific activities and isotope ratios was determined in an inter-tidal sediment core from the Esk Estuary in the northeastern Irish Sea. The study site has been impacted with plutonium through routine radionuclide discharges from the Sellafield nuclear reprocessing plant in Cumbria, NW England. A pronounced sub-surface maximum of {approx} 10 kBq kg{sup -1} was observed for {sup 239+240}Pu, corresponding to the peak in Pu discharge from Sellafield in 1973, with a decreasing trend with depth down to {approx} 0.04 kBq kg{sup -1} in the deeper layers. The depth profile of {sup 239+240}Pu specific activities together with results from gamma-ray spectrometry for {sup 137}Cs and {sup 241}Am was compared with reported releases from the Sellafield plant in order to estimate a reliable sediment chronology. The upper layers (1992 onwards) showed higher {sup 239+240}Pu specific activities than would be expected from the direct input of annual Sellafield discharges, indicating that the main input of Pu is from the time-integrated contaminated mud patch of the northeastern Irish Sea. The {sup 240}Pu/{sup 239}Pu atom ratios ranged from {approx} 0.03 in the deepest layers to > 0.20 in the sub-surface layers with an activity-weighted average of 0.181. The decreasing {sup 240}Pu/{sup 239}Pu atom ratio with depth reflects the changing nature of operations at the Sellafield plant from weapons-grade Pu production to reprocessing spent nuclear fuel with higher burn-up times in the late 1950s. In addition, recent annual {sup 240}Pu/{sup 239}Pu atom ratios in winkles collected during 2003-2008 from three stations along the Cumbrian coastline showed no significant spatial or temporal differences with an overall average of 0.204, which supports the hypothesis of diluted Pu input from the contaminated mud patch. - Highlights: {yields} Depth profiles of {sup 239}Pu and {sup 240}Pu determined in a northeastern Irish Sea sediment. {yields

  10. The history of metals pollution in Narragansett Bay as recorded by salt-marsh sediments

    International Nuclear Information System (INIS)

    Bricker, S.B.

    1990-01-01

    Sediment cores from 5 salt marshes from the head to the mouth of Narragansett Bay and an additional core from a lagoon on Block Island Sound were analyzed for 210 Pb and for Fe, Mn, Cu, Pb, Cr, Zn, Ag, and Ni in order to examine the long-term variation of metal inputs to Narragansett Bay. The 210 Pb results were used to determine accretion rates for each core. Distributions of Fe and Mn were used as indicators of chemical conditions of sediment cores and Cu, Pb, Cr, Zn, Ag, and Ni distributions with time were compared with known or estimated source inputs to examine the long-term variation of pollutant metal inputs to Narragansett Bay. At one location, duplicate cores were sampled to look at variability within a marsh. At another location, a high marsh, receiving predominantly atmospheric inputs and a low marsh, receiving waterborne and atmospheric inputs, were sampled so that atmospheric and tidal contributions could be determined. A comparison was made of the distributions of metals in bay cores and in the lagoon core. All the Rhode Island marshes accrete at rates equal to or greater than the local rise in sea level. Based on the 210 Pb chronologies, pollutant metals began to increase in the mid to late 1800s, corresponding to coal burning emissions to the atmosphere. Steeper increases in the 1900s reflect industrial and sewage discharges. Maximum concentrations were reached in the 1950s and have declined almost continuously since then. Observed reductions were attributable to implementation of and improvements to sewage treatment, and controls on atmospheric emissions

  11. A tephra lattice for Greenland and a reconstruction of volcanic events spanning 25-45 ka b2k

    Science.gov (United States)

    Bourne, A. J.; Cook, E.; Abbott, P. M.; Seierstad, I. K.; Steffensen, J. P.; Svensson, A.; Fischer, H.; Schüpbach, S.; Davies, S. M.

    2015-06-01

    Tephra layers preserved within the Greenland ice-cores are crucial for the independent synchronisation of these high-resolution records to other palaeoclimatic archives. Here we present a new and detailed tephrochronological framework for the time period 25,000-45,000 a b2k that brings together results from 4 deep Greenland ice-cores. In total, 99 tephra deposits, the majority of which are preserved as cryptotephra, are described from the NGRIP, NEEM, GRIP and DYE-3 records. The major element signatures of single glass shards within these deposits indicate that 93 are basaltic in composition all originating from Iceland. Specifically, 43 originate from Grimsvötn, 20 are thought to be sourced from the Katla volcanic system and 17 show affinity to the Kverkfjöll system. Robust geochemical characterisations, independent ages derived from the GICC05 ice-core chronology, and the stratigraphic positions of these deposits relative to the Dansgaard-Oeschger climate events represent a key framework that provides new information on the frequency and nature of volcanic events in the North Atlantic region between GS-3 and GI-12. Of particular importance are 19 tephra deposits that lie on the rapid climatic transitions that punctuate the last glacial period. This framework of well-constrained, time-synchronous tie-lines represents an important step towards the independent synchronisation of marine, terrestrial and ice-core records from the North Atlantic region, in order to assess the phasing of rapid climatic changes during the last glacial period.

  12. Bacteriohopanepolyols record stratification, nitrogen fixation and other biogeochemical perturbations in Holocene sediments of the central Baltic Sea

    Directory of Open Access Journals (Sweden)

    M. Blumenberg

    2013-04-01

    Full Text Available The Baltic Sea, one of the world's largest brackish-marine basins, established after deglaciation of Scandinavia about 17 000 to 15 000 yr ago. In the changeable history of the Baltic Sea, the initial freshwater system was connected to the North Sea about 8000 yr ago and the modern brackish-marine setting (Littorina Sea was established. Today, a relatively stable stratification has developed in the water column of the deep basins due to salinity differences. Stratification is only occasionally interrupted by mixing events, and it controls nutrient availability and growth of specifically adapted microorganisms and algae. We studied bacteriohopanepolyols (BHPs, lipids of specific bacterial groups, in a sediment core from the central Baltic Sea (Gotland Deep and found considerable differences between the distinct stages of the Baltic Sea's history. Some individual BHP structures indicate contributions from as yet unknown redoxcline-specific bacteria (bacteriohopanetetrol isomer, methanotrophic bacteria (35-aminobacteriohopanetetrol, cyanobacteria (bacteriohopanetetrol cyclitol ether isomer and from soil bacteria (adenosylhopane through allochthonous input after the Littorina transgression, whereas the origin of other BHPs in the core has still to be identified. Notably high BHP abundances were observed in the deposits of the brackish-marine Littorina phase, particularly in laminated sediment layers. Because these sediments record periods of stable water column stratification, bacteria specifically adapted to these conditions may account for the high portions of BHPs. An additional and/or accompanying source may be nitrogen-fixing (cyanobacteria, which is indicated by a positive correlation of BHP abundances with Corg and δ15N.

  13. Questa baseline and premining ground-water quality investigation. 8. Lake-sediment geochemical record from 1960 to 2002, Eagle Rock and Fawn Lakes, Taos County, New Mexico

    Science.gov (United States)

    Church, S.E.; Fey, D.L.; Marot, M.E.

    2005-01-01

    Geochemical studies of lake sediment from Eagle Rock Lake and upper Fawn Lake were conducted to evaluate the effect of mining at the Molycorp Questa porphyry molybdenum deposit located immediately north of the Red River. Two cores were taken, one from each lake near the outlet where the sediment was thinnest, and they were sampled at 1-cm intervals to provide geochemical data at less than 1-year resolution. Samples from the core intervals were digested and analyzed for 34 elements using ICP-AES (inductively coupled plasma-atomic emission spectrometry). The activity of 137Cs has been used to establish the beginning of sedimentation in the two lakes. Correlation of the geochemistry of heavy-mineral suites in the cores from both Fawn and Eagle Rock Lakes has been used to develop a sedimentation model to date the intervals sampled. The core from upper Fawn Lake, located upstream of the deposit, provided an annual sedimentary record of the geochemical baseline for material being transported in the Red River, whereas the core from Eagle Rock Lake, located downstream of the deposit, provided an annual record of the effect of mining at the Questa mine on the sediment in the Red River. Abrupt changes in the concentrations of many lithophile and deposit-related metals occur in the middle of the Eagle Rock Lake core, which we correlate with the major flood-of-record recorded at the Questa gage at Eagle Rock Lake in 1979. Sediment from the Red River collected at low flow in 2002 is a poor match for the geochemical data from the sediment core in Eagle Rock Lake. The change in sediment geochemistry in Eagle Rock Lake in the post-1979 interval is dramatic and requires that a new source of sediment be identified that has substantially different geochemistry from that in the pre-1979 core interval. Loss of mill tailings from pipeline breaks are most likely responsible for some of the spikes in trace-element concentrations in the Eagle Rock Lake core. Enrichment of Al2O3, Cu, and Zn

  14. Over 100 years of environmental change recorded by foraminifers and sediments in Mobile Bay, Alabama, Gulf of Mexico, USA

    Science.gov (United States)

    Osterman, Lisa E.; Smith, Christopher G.

    2012-12-01

    The marine microfauna of Mobile Bay has been profoundly influenced by the development and expansion of the primary shipping channel over the last ˜100 years. Foraminifers and sediments from seven box cores with excess lead-210 chronology document that channel dredging and spoil disposal have altered circulation, reduced estuarine mixing, changed sedimentation patterns, and caused a faunal turnover within the bay. Beginning in the late 1800s, changes in estuarine mixing allowed for greater low-pH freshwater influence in the bay, and ultimately began environmental changes that resulted in the loss of calcareous foraminifers. By the early 1900s, box cores throughout Mobile Bay record a ˜100-year trend of increasing calcareous test dissolution that continues to the present. Since the completion of the current shipping channel in the 1950s, restricted tidal flushing and increased terrestrial organic matter, documented by carbon-to-nitrogen ratios, stimulated an increase in agglutinated foraminiferal densities. However, in deeper areas of the bay, hypoxic water has negatively impacted the marine microfauna. Comparisons of the present-day foraminiferal assemblage with foraminifers collected in the early 1970s indicate that the continued biologic loss of calcareous foraminifers in the bay has allowed the introduction of a new agglutinated foraminiferal species into the bay.

  15. Carbonaceous particle record in lake sediments from the Arctic and other remote areas of the northern hemisphere

    International Nuclear Information System (INIS)

    Rose, N.L.

    1995-01-01

    Lake sediments, including spheroidal carbonaceous particles produced by high temperature combustion of fossil fuels, contain a record of lake, catchment and atmospheric deposition history. The spatial and temporal distributions of these particles can indicate the extent to which a single lake or a region has been contaminated by airborne pollutants (e.g. sulfur, polycyclic aromatic hydrocarbons (PAHs)) derived from fossil fuels. The carbonaceous particle records of two Arctic lakes, Shuonijavr and Stepanovichjarvi, close to local pollution sources on the Kola Peninsula, Russia, are compared with the record of a remote lake on Svalbard and with mid-latitude remote mountain lakes in Europe and Asia. Although, Shuonijavr and Stepanovichjarvi show relatively high levels of contamination, as expected, the presence of carbonaceous particles at all of the remote sites studied suggests there is a hemispherical background of these particles. Other less remote mountain lakes in Europe have been found to contain significant concentrations of particles and these may represent regional deposition patterns. Carbonaceous particle analysis may provide an effective assessment of whether a lake site is receiving local, regional or background levels of deposition

  16. Late Holocene monsoon climate as evidenced by proxy records from a lacustrine sediment sequence in western Guangdong, South China

    Science.gov (United States)

    Zhong, Wei; Cao, jiayuan; Xue, Jibin; Ouyang, Jun; Tang, Xiaohong; Yin, Huanling; Liao, Congyun; Long, Kun

    2014-02-01

    The study of a 300-cm-thick exposed lacustrine sediment section in the Hedong village in Zhaoqing area which is located in sub-tropical west Guangdong Province in South China, demonstrates that the lacustrine sedimentary sequence possibly contains evidence for exploring variation of Asian monsoon climate. Multi-proxy records, including the humification intensity, total organic carbon, and grain size fractions, reveal a general trend towards dry and cold conditions in the late Holocene that this is because of a decrease in solar insolation on an orbital scale. Three intensified Asian summer monsoon (ASM) intervals (˜3300-3000 cal yr BP, ˜2600-1600 cal yr BP, and ˜900-600 cal yr BP), and three weakened ASM intervals (˜4000-3300 cal yr BP, ˜3000-2600 cal yr BP, and ˜1600-900 cal yr BP) are identified. Our humification record (HDcal) shows a good correlation on multi-centennial scale with the tree ring Δ14C record, a proxy of solar activity. A spectral analysis of HDcal reveals four significant cycles, i.e., ˜1250 yr, 300 yr, 110 yr, and 70 yr, and most of these cycles are related to the solar activity. Our findings indicate that solar output and oceanic-atmospheric circulation probably have influenced the late Holocene climate variability in the study region.

  17. Integrative investigations on sediments in the Belauer See catchment (northern Germany)

    Science.gov (United States)

    Dreibrodt, Stefan

    2015-04-01

    The Holocene history of lake development, catchment vegetation, soil formation and human impact since the onset of the Neolithic period was reconstructed via the analysis of sediment sequences at Lake Belau (northern Germany). The chronology of the annually laminated lake sediment sequence was established via varve counts, radiocarbon dating and tephra analysis. Sequences of colluvial sediments and buried soils studied in 19 large exposures and supplementing auger cores within the lake catchment area were dated via radiocarbon dating and archaeological dating of embedded artifacts. The long term development of the lake status was found to be strongly influenced by local human activity. This is indicated by coincidence of phases of landscape openness deduced from pollen data with input of detritus and solutes into the lake. A comparison with palaeo-climate reconstructions reveals that calcite precipitation in the lake reflects climate variability at least to a certain degree. Calibrating the sediment record of the sub-recent lake sediments (micro-facies) on limnological and meteorological records discovered the influence of the NAO as well as solar activity on the limnological processes during the last century reflected by distinguished sedimentation patterns. A comparative study of additional laminated surface sediment sequences from northern Germany corroborates the results. A high resolution reconstruction of Neolithic weather conditions in northern Germany based on the varves of Lake Belau and Lake Poggensee was facilitated by the calibration. The quantitative records of sediments originating from soil erosion (colluvial sediments, allochthonous input into the lake) illustrate the dominance of short distance surface processes (slopes) acting in Holocene mid-latitude landscapes. Coincidence of gully incision in the lake catchment area and increased allochthonous input into the lake indicates the former occurrence of hydrological high energy runoff events (e. g

  18. Trace Element Geochemistry of Basaltic Tephra in Maar Cores; Implications for Centre Correlation, Field Evolution, and Mantle Source Characteristics of the Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Hopkins, J. L.; Leonard, G.; Timm, C.; Wilson, C. J. N.; Neil, H.; Millet, M. A.

    2014-12-01

    Establishing volcanic hazard and risk management strategies hinges on a detailed understanding of the type, timing and tephra dispersal of past eruptions. In order to unravel the pyroclastic eruption history of a volcanic field, genetic links between the deposits and eruption source centre need to be established. The Auckland Volcanic Field (AVF; New Zealand) has been active for ca. 200 kyr and comprises ca. 53 individual centres covering an area of ca. 360km2. These centres show a range of sizes and eruptive styles from maar craters and tuff rings, to scoria cones and lava flows consistent with both phreatomagmatic and magmatic eruptions. Superimposition of the metropolitan area of Auckland (ca. 1.4 million inhabitants) on the volcanic field makes it critically important to assess the characteristics of the volcanic activity, on which to base assessment and management of the consequent hazards. Here we present a geochemical approach for correlating tephra deposits to their source centres. To acquire the most complete stratigraphic record of pyroclastic events, maar crater cores from different locations, covering various depths and thus ages across the field were selected. Magnetic susceptibility and x-ray density scanning of the cores was used to identify the basaltic tephra horizons, which were sampled and in-situ analysis of individual shards undertaken for major and trace elements using EPMA and LA-ICP-MS techniques, respectively. Our results show that tephra shard trace element ratios are comparable and complementary to the AVF whole rock database. The use of specific trace element ratios (e.g. Gd/Yb vs. Zr/Yb) allows us to fingerprint and cross correlate tephra horizons between cores and, when coupled with newly acquired 40Ar-39Ar age dating and eruption size estimates, correlate horizons to their source centres. This integrated style of study can provide valuable information to help volcanic hazard management and forecasting, and mitigation of related risks.

  19. Millennial mercury records derived from ornithogenic sediment on Dongdao Island, South China Sea.

    Science.gov (United States)

    Yan, Hong; Wang, Yuhong; Cheng, Wenhan; Sun, Liguang

    2011-01-01

    Two ornithogenic sediment cores, which have a time span of 1000 years and are influenced by red-footed booby (Sula sula), were collected from Dongdao Islands, South China Sea. The determined mercury concentrations of the two cores show similar and substantial fluctuations during the past millennium, and the fluctuations are most likely caused by the changes in mercury level of the ocean environment and in anthropogenic Hg emission. For the past 500 years, the mercury concentration in the red-footed booby excrement has a striking association with global anthropogenic mercury emission. The mercury concentration increased rapidly after AD 1600 in corresponding to beginning of the unparalleled gold and silver mining in South Central America that left a large volume of anthropogenic mercury pollution. Since the Industrial Revolution, the mercury level has increased at a fast pace, very likely caused by modern coal combustion, chlor-alkali and oil refining industries. The comparison of mercury profiles from different places on earth suggested that anthropogenic mercury pollution after the Industrial Revolution is more severe in Northern Hemisphere than in Antarctica.

  20. Late Pleistocene to Holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments, southwestern Taiwan

    Science.gov (United States)

    Chen, Y.-G.; Liu, J.C.-L.; Shieh, Y.-N.; Liu, T.-K.

    2004-01-01

    A core, drilled at San-liao-wan in the southwestern coastal plain of Taiwan, has been analyzed for total sulfur contents, isotopic values, as well as ratios of pyritic sulfur to organic carbon. Our results demonstrate a close relationship between late Pleistocene sea-level change and the proxies generated in this study. The inorganic sulfur contents indicate that at our study site, the Holocene transgression started at ???11 ka and remained under seawater for thousands of years until the late Holocene, corresponding to a depth of 20 m in the study core. The uppermost 20 m of core shows relatively high total organic carbon (TOC) and ??34S of inorganic sulfur, suggesting a transitional environment such as muddy lagoon or marsh, before the site turned into a modern coastal plain. In the lower part of the core, at depths of 110-145 m (corresponding ages of ???12-30 ka), low sulfur contents are recorded, probably indicating fluvial sediments deposited during the oceanic isotope stage (OIS) 2, a sea-level lowstand. The lower part of the core, roughly within OIS 3, records at least two transgressions, although the transgressional signals may be somewhat obscured by subsequent weathering. The reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data; however, the marine organic source was periodically dominant. The modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments, probably indicating that the sulfate migrated into the site subsequent to early diagenesis. ?? 2003 Elsevier Ltd. All rights reserved.

  1. Sedimentary record of water column trophic conditions and sediment carbon fluxes in a tropical water reservoir (Valle de Bravo, Mexico).

    Science.gov (United States)

    Carnero-Bravo, Vladislav; Merino-Ibarra, Martín; Ruiz-Fernández, Ana Carolina; Sanchez-Cabeza, Joan Albert; Ghaleb, Bassam

    2015-03-01

    Valle de Bravo (VB) is the main water reservoir of the Cutzamala hydraulic system, which provides 40% of the drinking water consumed in the Mexico City Metropolitan Area and exhibits symptoms of eutrophication. Nutrient (C, N and P) concentrations were determined in two sediment cores to reconstruct the water column trophic evolution of the reservoir and C fluxes since its creation in 1947. Radiometric methods ((210)Pb and (137)Cs) were used to obtain sediment chronologies, using the presence of pre-reservoir soil layers in one of the cores as an independent chronological marker. Mass accumulation rates ranged from 0.12 to 0.56 g cm(-2) year(-1) and total organic carbon (TOC) fluxes from 122 to 380 g m(-2) year(-1). Total N ranged 4.9-48 g m(-2) year(-1), and total P 0.6-4.2 g m(-2) year(-1). The sedimentary record shows that all three (C, N and P) fluxes increased significantly after 1991, in good agreement with the assessed trophic evolution of VB and with historic and recent real-time measurements. In the recent years (1992-2006), the TOC flux to the bottom of VB (average 250 g m(-2) year(-1), peaks 323 g m(-2) year(-1)) is similar to that found in highly eutrophic reservoirs and impoundments. Over 1/3 of the total C burial since dam construction, circa 70,000 t, has occurred in this recent period. These results highlight the usefulness of the reconstruction of carbon and nutrient fluxes from the sedimentary record to assess carbon burial and its temporal evolution in freshwater ecosystems.

  2. Biomarker and stable carbon isotopic signatures for 100–200 year sediment record in the Chaihe catchment in southwest China

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yanhua, E-mail: wangyanhua@njnu.edu.cn [School of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Qixia, Nanjing 210023 (China); Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application (China); Yang, Hao [School of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Qixia, Nanjing 210023 (China); Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application (China); Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control (China); Zhang, Jixiang [College of Economics and Management, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Baixia, Nanjing 210016 (China); Xu, Meina; Wu, Changbin [School of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Qixia, Nanjing 210023 (China)

    2015-01-01

    Natural inputs and anthropogenic influences on lakes and their catchments are reflected in the sediment record. In the present study, the extractable organic compounds from sediments in the Chaihe catchment of the Dianchi watershed were analyzed to characterize source inputs. Results show that the sediments are dominated by odd numbered n-alkanes (n-C{sub 16}–n-C{sub 33}), maximizing at n-C{sub 17}, n-C{sub 29} and n-C{sub 31}. Aliphatic hydrocarbon may be composed of terrestrial plants and bacteria. The values of δ{sup 13}C{sub 27}, δ{sup 13}C{sub 29} and δ{sup 13}C{sub 31} of n-alkanes exhibit a range from − 33.27‰ to − 25.46‰, from − 35.76‰ to − 28.47‰ and from − 33.67‰ to − 27.42‰, respectively and three records strongly covary with depth, falling within the range of C{sub 3} plants in the study area. An isotopic model revealed C{sub 3} plant contribution to sedimentary organic matter (OM) ranging from 40.75% to 97.22%. The values of ACL{sub 27–33}, CPI{sub 27–33}, OEP, Paq, Pr/Ph, (C{sub 27} + C{sub 29})/2C{sub 31}, (C{sub 21} + C{sub 23} + C{sub 25})/3C{sub 17} and nC{sub 26}{sup −}/nC{sub 27}{sup +} are consistent with the C{sub 3} plant predominance. A constant CRS model gave the accumulation rates ranging from 2.69 to 8.46 mm a{sup −1} spanning 1885–2010. It was concluded that OM transport in the Chaihe catchment was influenced strongly by human activities resulting in enhanced eutrophication. - Highlights: • Strong predominance of odd-numbered n-alkanes maximized at n-C{sub 17}, n-C{sub 29} and n-C{sub 31} • Sedimentary OM in the Chaihe catchment was deduced mainly from C{sub 3} plants. • Human activities enhanced OM transport, resulting in worse ecosystem.

  3. Sub-ice-shelf sediments record history of twentieth-century retreat of Pine Island Glacier.

    Science.gov (United States)

    Smith, J A; Andersen, T J; Shortt, M; Gaffney, A M; Truffer, M; Stanton, T P; Bindschadler, R; Dutrieux, P; Jenkins, A; Hillenbrand, C-D; Ehrmann, W; Corr, H F J; Farley, N; Crowhurst, S; Vaughan, D G

    2017-01-05

    The West Antarctic Ice Sheet is one of the largest potential sources of rising sea levels. Over the past 40 years, glaciers flowing into the Amundsen Sea sector of the ice sheet have thinned at an accelerating rate, and several numerical models suggest that unstable and irreversible retreat of the grounding line-which marks the boundary between grounded ice and floating ice shelf-is underway. Understanding this recent retreat requires a detailed knowledge of grounding-line history, but the locations of the grounding line before the advent of satellite monitoring in the 1990s are poorly dated. In particular, a history of grounding-line retreat is required to understand the relative roles of contemporaneous ocean-forced change and of ongoing glacier response to an earlier perturbation in driving ice-sheet loss. Here we show that the present thinning and retreat of Pine Island Glacier in West Antarctica is part of a climatically forced trend that was triggered in the 1940s. Our conclusions arise from analysis of sediment cores recovered beneath the floating Pine Island Glacier ice shelf, and constrain the date at which the grounding line retreated from a prominent seafloor ridge. We find that incursion of marine water beyond the crest of this ridge, forming an ocean cavity beneath the ice shelf, occurred in 1945 (±12 years); final ungrounding of the ice shelf from the ridge occurred in 1970 (±4 years). The initial opening of this ocean cavity followed a period of strong warming of West Antarctica, associated with El Niño activity. Thus our results suggest that, even when climate forcing weakened, ice-sheet retreat continued.

  4. Collaborative Cyber-infrastructures for the Management of the UNESCO-IGCP Research Project "Forecast of tephra fallout"

    Science.gov (United States)

    Folch, A.; Costa, A.; Cordoba, G.

    2009-04-01

    Tephra fallout following explosive volcanic eruptions produces several hazardous effects on inhabitants, infrastructure, and property and represents a serious threat for communities located around active volcanoes. In order to mitigate the effects on the surrounding areas, scientists and civil decision-making authorities need reliable short-term forecasts during episodes of eruptive crisis and long-term probabilistic maps to plan territorial policies and land use. Modelling, together with field studies and volcano monitoring, constitutes an indispensable tool to achieve these objectives. The UNESCO-IGCP research project proposal "Forecast of tephra fallout" has the aim to produce a series of tools capable to elaborate both short-term forecasts and long-term hazard assessments using the cutting-edge models for tephra transport and sedimentation. A special project website will be designed to supply a set of models, procedures and expertise to several Latino-American Institutes based in countries seriously threatened by this geo-hazard (Argentina, Chile, Colombia, Ecuador, Mexico, and Nicaragua). This will proportionate to the final users a tool to elaborate short-term forecasts of tephra deposition on the ground, and determine airborne ash concentrations (a quantity of special relevance for aerial navigation safety) during eruptions and emergencies. The project web-site will have a public section and a password-protected area to exchange information and data among participants and, eventually, to allow remote execution of high-resolution mesoscale meteorological forecasts at the BSC facilities. The public website section will be updated periodically and will include sections describing the project objectives and achievements as well as the hazard maps for the investigated volcanoes, and will be linked to other relevant websites such as IAVCEI, IGCP, IUGS and UNESCO homepages. A part of the public section of the website will be devoted to disseminate achieved

  5. The nuclear bomb carbon curve recorded in tree-rings and lake sediments near Taal Volcano, Central Philippines

    Science.gov (United States)

    Liou, M. S.; Li, H. C.; Huang, S. K.; Guan, B. T.

    2017-12-01

    Dendrochronologies built from precisely dated annual rings have shown to record the regional bomb pulse and the C-14 concentration variations caused by local events. In this study, we collected teak trees Tectona grandis near the Lake Taal, Central Philippines in 2011 for dendrochronological analysis and radiocarbon dating. The tree-ring sample contains 90 rings dated from 1922 to 2011. Currently, 28 selected subsamples have been measured by AMS 14C on bulk carbon with a few samples on holocellulose. The 14C results of the samples indicate that: 1) the results of AMS 14C dating between holocellulose and whole wood from the same ring are similar, so we select whole wood for AMS 14C dating. 2) The nuclear bomb 14C pulse was clearly recorded in the Tectona grandis growth rings. The Δ14C values rose dramatically in 1960 and reached a maximum of 692‰ in 1966. The magnitude and the peak year of the bomb curve in the Tectona grandis tree-ring record are comparable to other published tree-ring records in the tropical regions. 3) The Δ14C values suddenly dropped in 1950, 1964 and 1968, probably affected by CO2 gas releasing due to the Taal volcanic activities. Further study on the tree-ring 14C dating will allow us to evaluate the bomb pulse trends more precisely, and the volcanic activities of Pinatubo and Taal Volcanoes. The tree-ring Δ14C record not only confirms existence of the bomb curve in Taal Lake area, but also allows us compare to the Δ14C record in the lake sediment for chronological construction. A 120-cm gravity core, TLS-2, collected from Lake Taal in 2008, shows the nuclear bomb carbon curve in the TOC of the core. However, the magnitude of the nuclear bomb 14C pulse in the TOC of TLS-2 is much lower than that in the tree-ring records, due to mixing effect of different organic carbon sources, smoothing effect of 14CO2 in multiple years plant growths, local old CO2 emission from volcanic activity, degassing from the lake bottom, and industrial and city

  6. Sub-ice-shelf sediments record history of twentieth-century retreat of Pine Island Glacier

    OpenAIRE

    Smith, J.A.; Andersen, T.J.; Shortt, M.; Gaffney, A.M.; Truffer, M.; Stanton, T.P.; Bindschadler, R.; Dutrieux, P.; Jenkins, A.; Hillenbrand, C.-D.; Ehrmann, W.; Corr, H.F.J.; Farley, N.; Crowhurst, S.; Vaughan, D.G.

    2016-01-01

    The article of record as published may be found at http://dx.doi.org/10.1038/nature20136 The West Antarctic Ice Sheet is one of the largest potential sources of rising sea levels. Over the past 40 years, glaciers flowing into the Amundsen Sea sector of the ice sheet have thinned at an accelerating rate, and several numerical models suggest that unstable and irreversible retreat of the grounding line—which marks the boundary between grounded ice and floating ice shelf—is underway. Under...

  7. Environmental evolution records reflected by radionuclides in the sediment of coastal wetlands: A case study in the Yellow River Estuary wetland.

    Science.gov (United States)

    Wang, Qidong; Song, Jinming; Li, Xuegang; Yuan, Huamao; Li, Ning; Cao, Lei

    2016-10-01

    Vertical profiles of environmental radionuclides ( 210 Pb, 137 Cs, 238 U, 232 Th, 226 Ra and 4 0 K) in a sediment core (Y1) of the Yellow River Estuary wetland were investigated to assess whether environmental evolutions in the coastal wetland could be recorded by the distributions of radionuclides. Based on 210 Pb and 137 Cs dating, the average sedimentation rate of core Y1 was estimated to be 1.0 cm y -1 . Vertical distributions of natural radionuclides ( 238 U, 232 Th, 226 Ra and 40 K) changed dramatically, reflecting great changes in sediment input. Concentrations of 238 U, 232 Th, 226 Ra and 40 K all had significant positive relationships with organic matter and clay content, but their distributions were determined by different factors. Factor analysis showed that 238 U was determined by the river sediment input while 226 Ra was mainly affected by the seawater erosion. Environmental changes such as river channel migrations and sediment discharge variations could always cause changes in the concentrations of radionuclides. High concentrations of 238 U and 226 Ra were consistent with high accretion rate. Frequent seawater intrusion decreased the concentration of 226 Ra significantly. The value of 238 U/ 226 Ra tended to be higher when the sedimentation rate was low and tide intrusion was frequent. In summary, environmental evolutions in the estuary coastal wetland could be recorded by the vertical profiles of natural radionuclides. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Holocene vegetation and climate change recorded in alpine bog sediments from the Borreguiles de la Virgen, Sierra Nevada, southern Spain

    Science.gov (United States)

    Jiménez-Moreno, Gonzalo; Anderson, R. Scott

    2012-01-01

    High-resolution pollen and magnetic susceptibility (MS) analyses have been carried out on a sediment core taken from a high-elevation alpine bog area located in Sierra Nevada, southern Spain. The earliest part of the record, from 8200 to about 7000 cal yr BP, is characterized by the highest abundance of arboreal pollen and Pediastrum, indicating the warmest and wettest conditions in the area at that time. The pollen record shows a progressive aridification since 7000 cal yr BP that occurred in two steps, first shown by a decrease in Pinus, replaced by Poaceae from 7000 to 4600 cal yr BP and then by Cyperaceae, Artemisia and Amaranthaceae from 4600 to 1200 cal yr BP. Pediastrum also decreased progressively and totally disappeared at ca. 3000 yr ago. The progressive aridification is punctuated by periodically enhanced drought at ca. 6500, 5200 and 4000 cal yr BP that coincide in timing and duration with well-known dry events in the Mediterranean and other areas. Since 1200 cal yr BP, several changes are observed in the vegetation that probably indicate the high-impact of humans in the Sierra Nevada, with pasturing leading to nutrient enrichment and eutrophication of the bog, Pinus reforestation and Olea cultivation at lower elevations.

  9. A ~20,000 year history of glacial variability in the tropical Andes recorded in lake sediments from the Cordillera Blanca, Peru

    Science.gov (United States)

    Stansell, N.; Rodbell, D. T.; Moy, C. M.

    2010-12-01

    Pro-glacial lake sediments from the Cordillera Blanca, Peru contain continuous records of climate variability spanning the Last Glacial Maximum to present day. Here we present results from two alpine lake basins in the Queshgue Valley (9.8°S, 77.3°W) that contain high-resolution records of clastic sediment deposition for the last ~20,000 years. Radiocarbon-dated sediment cores were scanned at 0.5 to 1.0 cm resolution using a profiling x-ray fluorescence scanner for major and minor element distributions. In addition, we measured down-core variations in magnetic susceptibility, organic carbon, biogenic silica and calcium carbonate. Samples of bedrock and sediments from glacial moraines in the Queshgue watershed were analyzed using an ICP-MS in order to fingerprint and trace the source of glacial sediments deposited in the lakes. The bedrock is dominated by a combination of granodiorite with high Sr concentrations and meta-sedimentary rocks with high Zr values. Because the glacial sediments proximal to the modern glacier terminus are composed mostly of the granodiorite end-member, we interpret changes in Sr and clastic sediment concentrations in the lake sediment profiles as proxies for past glacial variability. Preliminary results indicate that glaciers retreated soon after ~14,500 cal yr BP and remained less extensive during the remaining late Glacial Stage and early Holocene. Gradually increasing clastic sediments through the middle and late Holocene indicate that glaciers became progressively larger, or more erosive towards present day. However, this overall Holocene trend of increasing glacier extent was interrupted by multiple periods of centennial- to millennial-scale ice margin retreat. For example, relative peaks in clastic sediments occurred from ~14,500 to 6000, 5600 to 5000, 4600 to 4200, 3600 to 3200, 2800 to 2700, 2400 to 2200, 1750 to 1550, 1100 to 900 cal yr BP, and during the Little Ice Age (~700 to 50 cal yr BP), while periods of low clastic

  10. Record of late Pleistocene glaciation and deglaciation in the southern Cascade Range. I. Petrological evidence from lacustrine sediment in Upper Klamath Lake, southern Oregon

    Science.gov (United States)

    Reynolds, R.L.; Rosenbaum, J.G.; Rapp, J.; Kerwin, M.W.; Bradbury, J.P.; Colman, S.; Adam, D.

    2004-01-01

    Petrological and textural properties of lacustrine sediments from Upper Klamath Lake, Oregon, reflect changing input volumes of glacial flour and thus reveal a detailed glacial history for the southern Cascade Range between about 37 and 15 ka. Magnetic properties vary as a result of mixing different amounts of the highly magnetic, glacially generated detritus with less magnetic, more weathered detritus derived from unglaciated parts of the large catchment. Evidence that the magnetic properties record glacial flour input is based mainly on the strong correlation between bulk sediment particle size and parameters that measure the magnetite content and magnetic mineral freshness. High magnetization corresponds to relatively fine particle size and lower magnetization to coarser particle size. This relation is not found in the Buck Lake core in a nearby, unglaciated catchment. Angular silt-sized volcanic rock fragments containing unaltered magnetite dominate the magnetic fraction in the late Pleistocene sediments but are absent in younger, low magnetization sediments. The finer grained, highly magnetic sediments contain high proportions of planktic diatoms indicative of cold, oligotrophic limnic conditions. Sediment with lower magnetite content contains populations of diatoms indicative of warmer, eutrophic limnic conditions. During the latter part of oxygen isotope stage 3 (about 37-25 ka), the magnetic properties record millennial-scale variations in glacial-flour content. The input of glacial flour was uniformly high during the Last Glacial Maximum, between about 21 and 16 ka. At about 16 ka, magnetite input, both absolute and relative to hematite, decreased abruptly, reflecting a rapid decline in glacially derived detritus. The decrease in magnetite transport into the lake preceded declines in pollen from both grass and sagebrush. A more gradual decrease in heavy mineral content over this interval records sediment starvation with the growth of marshes at the margins

  11. Rapid sedimentation of iron oxyhydroxides in an active hydrothermal shallow semi-enclosed bay at Satsuma Iwo-Jima Island, Kagoshima, Japan

    Science.gov (United States)

    Kiyokawa, Shoichi; Ueshiba, Takuya

    2015-04-01

    Hydrothermal activity is common in the fishing port of Nagahama Bay, a small semi-enclosed bay located on the southwest coast of Satsuma Iwo-Jima Island (38 km south of Kyushu Island, Japan). The bay contains red-brown iron oxyhydroxides and thick deposits of sediment. In this work, the high concentration and sedimentation rates of oxyhydroxide in this bay were studied and the sedimentary history was reconstructed. Since dredging work in 1998, a thickness of 1.0-1.5 m of iron oxyhydroxide-rich sediments has accumulated on the floor of the bay. To estimate the volume of iron oxyhydroxide sediments and the amount discharged from hydrothermal vents, sediment traps were operated for several years and 13 sedimentary core samples were collected to reconstruct the 10-year sedimentary history of Nagahama Bay. To confirm the timing of sedimentary events, the core data were compared with meteorological records obtained on the island, and the ages of characteristic key beds were thus identified. The sedimentation rate of iron oxyhydroxide mud was calculated, after correcting for sediment input from other sources. The sediments in the 13 cores from Nagahama Bay consist mainly of iron oxyhydroxide mud, three thick tephra beds, and a topmost thick sandy mud bed. Heavy rainfall events in 2000, 2001, 2002, and 2004-2005 coincide with tephra beds, which were reworked from Iwo-Dake ash deposits to form tephra-rich sediment. Strong typhoon events with gigantic waves transported outer-ocean-floor sediments and supplied quartz, cristobalite, tridymite, and albite sands to Nagahama Bay. These materials were redeposited together with bay sediments as the sandy mud bed. Based on the results from the sediment traps and cores, it is estimated that the iron oxyhydroxide mud accumulated in the bay at the relatively rapid rate of 33.3 cm/year (from traps) and 2.8-4.9 cm/year (from cores). The pore water contents within the sediment trap and core sediments are 73%-82% and 47%-67%, respectively

  12. Streamflow record extension using power transformations and application to sediment transport

    Science.gov (United States)

    Moog, Douglas B.; Whiting, Peter J.; Thomas, Robert B.

    1999-01-01

    To obtain a representative set of flow rates for a stream, it is often desirable to fill in missing data or extend measurements to a longer time period by correlation to a nearby gage with a longer record. Linear least squares regression of the logarithms of the flows is a traditional and still common technique. However, its purpose is to generate optimal estimates of each day's discharge, rather than the population of discharges, for which it tends to underestimate variance. Maintenance-of-variance-extension (MOVE) equations [Hirsch, 1982] were developed to correct this bias. This study replaces the logarithmic transformation by the more general Box-Cox scaled power transformation, generating a more linear, constant-variance relationship for the MOVE extension. Combining the Box-Cox transformation with the MOVE extension is shown to improve accuracy in estimating order statistics of flow rate, particularly for the nonextreme discharges which generally govern cumulative transport over time. This advantage is illustrated by prediction of cumulative fractions of total bed load transport.

  13. Tephra and cryptotephra in a 60,000-year-old lacustrine sequence from the Fucino Basin: new insights into the major explosive events in Italy

    Science.gov (United States)

    Di Roberto, Alessio; Smedile, Alessandra; Del Carlo, Paola; De Martini, Paolo Marco; Iorio, Marina; Petrelli, Maurizio; Pantosti, Daniela; Pinzi, Stefania; Todrani, Alessandro

    2018-03-01

    Two cores were sampled in the Fucino Basin (central Apennines, Italy), which represents an extensional intramountain basin filled by Pliocene to Quaternary continental alluvial and lacustrine deposits. The cores were investigated for tephra content and five visible tephras with thickness ranging from 1 to 8 cm were identified. Six additional cryptotephra were identified during the inspection of significant peaks of the magnetic susceptibility curve. Texture and mineralogy of five tephra and six cryptotephra layers were analyzed by means of scanning electron microscope coupled with energy-dispersive X-ray spectrometry system (SEM-EDS) and geochemical measurements were performed by an electron microprobe (EPMA) equipped with five wavelength-dispersive spectrometers (WDS) and using a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) system on single glass shards. The results allowed us to assign tephra and cryptotephra to ten known volcanic eruptions that occurred over the last ca. 60 ka in the Campanian Province (Phlegrean Fields and Ischia Island), the Alban Hills volcanic complex, and Lipari island. In particular, we recognized the deposits of the Monte Epomeo Green Tuff and the Piroclastiti di Catavola eruptions of Ischia, the pre-Campanian Ignimbrite Tlc, the Campanian Ignimbrite and the Neapolitan Yellow Tuff eruptions of the Phlegrean Fields, the Gabellotto-Fiume Bianco eruption of Lipari, and all the four explosive events belonging to the last cycle of volcanic activity of Albano maar (Albano 4-7). Deposits from five of these identified events (i.e., Piroclastiti di Catavola, Gabellotto-Fiume Bianco, Albano 5 and 6 eruptions, and Campanian Ignimbrite) were previously un-reported in the Fucino basin. These findings add new tephra layers to the list of possible tephrochronologic markers in the region and highlight that a comprehensive tephra record may be constructed when the study of cryptotephra layers is included. Moreover, results

  14. Dramatic decreases in runoff and sediment load in the Huangfuchuan Basin of the Middle Yellow River, China: historical records and future projections

    Science.gov (United States)

    LI, E.; Li, D.; Wang, Y.; Fu, X.

    2017-12-01

    The Yellow River is well known for its high sediment load and serious water shortage. The long-term averaged sediment load is about 1.6´103 million tons per year, resulting in aggrading and perched lower reaches. In recent years, however, dramatic decreases in runoff and sediment load have been observed. The annual sediment load has been less than 150 million tons in the last ten years. Extrapolation of this trend into the future would motivate substantial change in the management strategies of the Lower Yellow River. To understand the possible trend and its coevolving drivers, we performed a case study of the Huangfuchuang River, which is a tributary to the Middle Yellow River, with a drainage area of 3246 km2 and an annual precipitation of 365 mm. Statistical analysis of historical data from 1960s to 2015 showed a significantly decreasing trend in runoff and sediment load since 1984. As potential drivers, the precipitation does not show an obvious change in annual amount, while the vegetation cover and the number of check dams have been increased gradually as a result of the national Grain for Green project. A simulation with the Soil and Water Assessment Tool (SWAT) reproduced the historical evolution processes, and showed that human activities dominated the reduction in runoff and sediment load, with a contribution of around 80%. We then projected the runoff and sediment load for the next 50 years (2016-2066), considering typical scenarios of climate change and accounting for vegetation cover development subject to climate conditions and storage capacity loss of check dams due to sediment deposition. The differences between the projected trend and the historical record were analyzed, so as to highlight the coevolving processes of climate, vegetation, and check dam retention on a time scale of decades. Keywords: Huangfuchuan River Basin, sediment load, vegetation cover, check dams, annual precipitation, SWAT.

  15. A palynological study of Polynesian and European effects on vegetation in Coromandel, New Zealand, showing the variability between four records from a single swamp

    International Nuclear Information System (INIS)

    Byrami, M.; Ogden, J.; Horrocks, M.; Deng, Y.; Shane, P.; Palmer, J.

    2002-01-01

    Seven cores were extracted from a river terrace swamp in the forested Kauaeranga valley, Coromandel Peninsula, New Zealand. High-resolution (c. 36-73 yr interval) pollen records were obtained from four of the cores and aged by radiocarbon dating and with stratigraphic reference to the 665 ± 15 14 C yr BP Kaharoa Tephra. The records span the last c. 1800 yr and show that the vegetation consisted of lowland podocarp-hardwood forest before deforestation by burning occurred. The pattern of deforestation at Kauaeranga, indicated by the abrupt dominance of Pteridium with concurrent increased charcoal, is typical of pollen records associated with early Polynesian settlement in New Zealand. Peaks of Pteridium and charcoal were also found in sediments deposited after European settlement. Different cores show marked palynological and stratigraphic differences relative to the Kaharoa Tephra, most importantly with regard to the timing of deforestation. Deforestation occurred close to the Kaharoa, at a calculated age of c. 750 BP in one core but well above the Kaharoa (c. 480 BP) in another. The stratigraphic unconformities between cores are attributed to variable fluvial processes causing an uneven deposition of sediments within the swamp. (author). 32 refs., 8 figs., 4 tabs

  16. A late Holocene metal record of Andean climate and anthropogenic activity in lake sediments near Quelccaya Ice Cap, Peru

    Science.gov (United States)

    Beal, S. A.; Kelly, M. A.; Jackson, B. P.; Stroup, J. S.; Osterberg, E. C.

    2011-12-01

    The tropical hypothesis maintains that major changes in global climate are motivated by phenomena based at tropical latitudes. Evidence for this hypothesis lies in: modern-day observations of El Niño Southern Oscillation (ENSO); East African lake sediment records of Intertropical Convergence Zone (ITCZ) position that precede high-latitude changes; and the potential for ITCZ shifts to cause major CO2 degassing from the Southern Ocean. In order to improve the understanding of these phenomena we present an ~1800 year record of atmospheric metal deposition in a lake sediment core near Quelccaya Ice Cap, Peru (13.9 °S). In June, 2010 we collected a 1.45 meter-long core from Yanacocha - a small, closed-basin tarn that has been isolated from glacial input since ~11,200 BP. The chronology for the core is based on 4 of 6 AMS 14C dates on aquatic macrofossils and one sharp Zr/Ti anomaly at 36 cm, likely derived from the 350 BP eruption of Huaynaputina. We completely digested organic-rich core samples at 1 cm resolution using HNO3, HCl, and HF in a closed-vessel microwave system, and then analyzed the digestates for 67 metals by inductively coupled plasma mass spectrometry. Here we show fluxes of lithogenic metals (Fe, Nb, Ti, and Zr) that reflect changes in wind strength and aridity, fluxes of lithogenic metal isotopes (REEs and Pb) that reflect wind direction, and enrichment factors (EFs) of metals (Ag, As, Cd, Cu, Hg, and Pb) that reflect anthropogenic activity. Five episodic peaks in lithogenic metal fluxes, centered around 1800, 1300, 900, 600, and 100 yrs BP, are thought to result from either drier or windier conditions, potentially caused by a northern ITCZ position or a more persistent El Niño state. The provenance of atmospheric deposition, evidenced by REE ratios (light REEs / heavy REEs), suggest that high lithogenic fluxes are associated with a change in wind direction, possibly caused by a change in the ENSO state, which will be explored with forthcoming Pb

  17. Comparison of infrared spectroscopy techniques: developing an efficient method for high resolution analysis of sediment properties from long records

    Science.gov (United States)

    Hahn, Annette; Rosén, Peter; Kliem, Pierre; Ohlendorf, Christian; Persson, Per; Zolitschka, Bernd; Pasado Science Team

    2010-05-01

    The analysis of sediment samples in visible to mid-infrared spectra is ideal for high-resolution records. It requires only small amounts (0.01-0.1g dry weight) of sample material and facilitates rapid and cost efficient analysis of a wide variety of biogeochemical properties on minerogenic and organic substances (Kellner et al. 1998). One of these techniques, the Diffuse Reflectance Fourier Transform Infrared Spectrometry (DRIFTS), has already been successfully applied to lake sediment from very different settings and has shown to be a promising technique for high resolution analyses of long sedimentary records on glacial-interglacial timescales (Rosén et al. 2009). However, the DRIFTS technique includes a time-consuming step where sediment samples are mixed with KBr. To assess if alternative and more rapid infrared (IR) techniques can be used, four different IR spectroscopy techniques are compared for core catcher sediment samples from Laguna Potrok Aike - an ICDP site located in southernmost South America. Partial least square (PLS) calibration models were developed using the DRIFTS technique. The correlation coefficients (R) for correlations between DRIFTS-inferred and conventionally measured biogeochemical properties show values of 0.80 for biogenic silica (BSi), 0.95 for total organic carbon (TOC), 0.91 for total nitrogen (TN), and 0.92 for total inorganic carbon (TIC). Good statistical performance was also obtained by using the Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy ATR-FTIRS technique which requires less sample preparation. Two devices were used, the full-sized Bruker Equinox 252 and the smaller and less expensive Bruker Alpha. R for ATR-FTIRS-inferred and conventionally measured biogeochemical properties were 0.87 (BSi), 0.93 (TOC), 0.90 (TN), and 0.91 (TIC) for the Alpha, and 0.78 (TOC), 0.85 (TN), 0.79 (TIC) for the Equinox 252 device. As the penetration depth of the IR beam is frequency dependent, a firm surface contact of

  18. Ecosystem responses during Late Glacial period recorded in the sediments of Lake Łukie (East Poland)

    Science.gov (United States)

    Zawiska, Izabela; Słowiński, Michał; Correa-Metrio, Alex; Obremska, Milena; Luoto, Tomi; Nevalainen, Liisa; Woszczyk, Michał; Milecka, Krystyna

    2014-05-01

    The main objectives of this study was to reconstruct climate impact on the functioning of Lake Łukie and its catchment (Łęczna Włodawa Lake District, East European Plain) during Late Glacial period. In order to reconstruct climatic fluctuations and corresponding ecosystem responses, we analysed lake sediments for pollen, subfossil Cladocera, plant macrofossils and chemical composition of the sediment. Of these, plant macrofossils and Cladocera were used to infer minimum and mean July temperatures and ordination analysis was used to examine biotic community shifts. Multiproxy analyses of late-glacial sediments of Lake Łukie clearly show that the main driver of aquatic and terrestrial ecosystems as well as geomorphological processes in the catchment was climate variation. The history of the lake initiated during the Older Dryas. In that period, Łęczna Włodawa Lake District was covered by open habitats dominated by grasses (Poaceae), humid sites were occupied by tundra plant communities with less clubmoss (Selaginella selaginoides), dry sites by dominated by steppe-like vegetation with light-demanding species such as Helianthemum, Artemisia, Chenopodiaceae, and juniper bushes (Juniperus). Cold climate limited the growth and development of organisms in the lake, Cladocera community species composition was poor, with only few species present there all the time. During this time period, permafrost was still present in the ground limiting infiltration of rainwater and causing high erosion in the catchment area. Surface runoff is confirmed by the presence of sclerotia of Cenococcum geophilum and high terrigenous silica content. The warming of the early Allerød caused a remarkable change in the natural environment of this area. This is in accordance with the temperature rise reconstructed with the use of plant macrofossils though the Cladocera reconstruction did not recorded the rise than. This temperature increase resulted in turnover of vegetation in the

  19. Grain size and shape analysis of the AD 1226 tephra layer, Reykjanes volcanic system

    Science.gov (United States)

    Ösp Magnúsdóttir, Agnes; Höskuldsson, Ármann; Larsen, Guðrún; Tumi Guðmunsson, Magnús; Sigurgeirsson, Magnús Á.

    2014-05-01

    Recent explosive eruptions in Iceland have drawn attention to long range tephra transport in the atmosphere. In Iceland tephra forming explosion eruptions are frequent, due to abundance of water. However, the volcanism on the island is principally basaltic. Volcanism along the Reykjanes Peninsula is divided into five distinct volcanic systems. Volcano-tectonic activity within these systems is periodic, with recurrence intervals in the range of 1 ka. Last volcano-tectonic sequence began around AD 940, shortly after settlement of Iceland, and lasted through AD 1340. During this period activity was characterized by basaltic fissure eruptions. Furthermore, this activity period on the Reykjanes peninsula began within the eastern most volcanic system and gradually moved towards the west across the peninsula. The 1226 eruption was a basaltic fissure eruption with in the Reykjanes volcanic system. The eruption began on land and gradually progressed towards the SW until the volcanic fissure extended into the sea. Water-magma interaction changed the eruption from effusive into explosive forming the largest tephra layer on the peninsula. Due to its close proximity to the Keflavik international airport and that of the capital of Iceland it is important to get an insight into, the characteristics, generation and distribution of such tephra deposits. In this eruption the tephra produced had an approximate volume of 0.1 km3 and covered an area of some 3500 km2 within the 0.5 cm isopach. Total grain size distribution of this tephra layer will be presented along with analysis of principal grain shapes of the finer portion of the tephra layer as a function of distance from the source. The tephra grain size is dominated by particles finer than 1 millimeter with an almost complete absence of large grains independent of distance from the source. Comprehensive understanding of the characteristics of tephra generated in this eruption can help us to understand hazards posed by future

  20. Detailed Jaramillo field reversals recorded in lake sediments from Armenia - Lower mantle influence on the magnetic field revisited

    Science.gov (United States)

    Kirscher, U.; Winklhofer, M.; Hackl, M.; Bachtadse, V.

    2018-02-01

    While it is well established that the Earth's magnetic field is generated by a self sustaining dynamo that reversed its polarity at irregular intervals in the geological past, the very mechanisms causing field reversals remain obscure. Paleomagnetic reconstructions of polarity transitions have been essential for physically constraining the underlying mechanisms in terms of time scale, but thus far remain ambiguous with regard to the transitional field geometry. Here we present new paleomagnetic records from a rapidly deposited lacustrine sediment sequence with extraordinarily stable paleomagnetic signals, which has captured in unprecedented detail the bottom (reverse to normal: R-N) and top (normal to reverse: N-R) transitions of the Jaramillo subchron (at 1.072 Ma and at 0.988 Ma). The obtained virtual geomagnetic pole (VGP) path indicates an oscillatory transitional field behavior with four abrupt transequatorial precursory jumps across the Pacific. The distribution of VGP positions indicates regions of preferred occurrence. Our results are in agreement with previously proposed bands of transitional VGP occurrence over the Americas and Australia/northwest Pacific. Additionally, our VGP positions seem to avoid large low shear velocity provinces (LLSVPs) above the core mantle boundary (CMB). Thus, our data supports the idea that the transitional field geometry is controlled by heat flux heterogeneities at the CMB linked to LLSVPs.

  1. Impact of earthquakes on agriculture during the Roman-Byzantine period from pollen records of the Dead Sea laminated sediment

    Science.gov (United States)

    Leroy, Suzanne A. G.; Marco, Shmuel; Bookman, Revital; Miller, Charlotte S.

    2010-03-01

    The Dead Sea region holds the archives of a complex relationship between an ever-changing nature and ancient civilisations. Regional pollen diagrams show a Roman-Byzantine period standing out in the recent millennia by its wetter climate that allowed intensive arboriculture. During that period, the Dead Sea formed laminites that display mostly a seasonal character. A multidisciplinary study focused on two earthquakes, 31 BC and AD 363, recorded as seismites in the Ze'elim gully A unit III which has been well dated by radiocarbon in a previous study. The sampling of the sediment was done at an annual resolution starting from a few years before and finishing a decade after each earthquake. A clear drop in agricultural indicators (especially Olea and cereals) is shown. These pollen indicators mostly reflect human activities in the Judean Hills and coastal oases. Agriculture was disturbed in large part of the rift valley where earthquake damage affected irrigation and access to the fields. It took 4 to 5 yr to resume agriculture to previous conditions. Earthquakes must be seen as contributors to factors damaging societies. If combined with other factors such as climatic aridification, disease epidemics and political upheaval, they may lead to civilisation collapse.

  2. Sedimentological, mineralogical, and geochemical results from surface sediments and the sediment record from Site 2 of the ICDP drilling project at Lake Towuti, Indonesia

    Science.gov (United States)

    Hasberg, A. K.; Melles, M.; Wennrich, V.; Vogel, H.; Just, J.; Russell, J. M.; Bijaksana, S.; Morlock, M.; Opitz, S.

    2017-12-01

    More than 1000 m of sediment core were recovered in spring 2015 from three different drill sites in tropical Lake Towuti (2.5°S, 121°E), Indonesia, during the Towuti Drilling Project (TDP) of the International Continental Scientific Drilling Program (ICDP). Furthermore, a set of 84 lake surface sediment samples, distributed over the entire lake, was collected in order to better understand modern sedimentary processes. The surface samples were investigated for physical, chemical, mineralogical, and biological properties at the University of Cologne (UoC), Germany. On the sediment cores macro- and microscopical lithological descriptions, line-scan imaging, logging of physical properties (MSCL), and subsampling was conducted at the National Lacustrine Core Facility of the University of Minnesota, USA, in November 2015 and January 2016. Afterwards, the archive core halves and 672 subsamples of TDP Site 2 were shipped to the UoC for X-Ray Fluorescence (XRF) scanning and sedimentological, geochemical, and mineralogical analyses, respectively, supplemented by visible to near-infrared spectroscopy (VNIR) at Brown University, USA. The data from the surface samples evidence that allochthonous sedimentation in Lake Towuti today is dominated by fluvial supply from five distinguishable source areas: (i) the Mahalona River to the north, which drains lakes Mahalona and Matano, (ii) inlets around the village of Timampu to the northwest, (iii) the Loeha River to the east, (iv) the Lengke River to the south, and (v) the Lemo-Lemo River to the northeast of Lake Towuti. Of these, source areas (ii) and (iii) as well as (iv) and (v) have similar geochemical compositions, respectively. In addition, the lake sedimentation is significantly influenced by gravitational sediment supply from steep slopes as well as lake-internal gravitational and density-driven processes. The uppermost 41 m of sediment core 2A consist of pelagic sediments (totaling 11 m) and event layers from mass movement

  3. Rock Magnetic Properties, Paleosecular Variation Record and Relative Paleointensity Stack between 11 and 21 14C kyr B.P. From Sediment Cores, Lake Moreno (Argentina)

    Science.gov (United States)

    Gogorza, C. S.; Irurzun, M. A.; Lirio, J. M.; Nunez, H.; Chaparro, M. A.; Sinito, A. M.

    2008-05-01

    We conducted a detailed study of natural remanence and rock magnetic properties on sediments cores from lake Moreno (South-Western Argentina). Based on these measurements, we constructed a paleosecular variation (PSV) record (Irurzun et al., 2008) and a relative paleointensity stack for the period 11-21 14C. The Declination and Inclination logs of the characteristic remanent magnetization for the cores as function of shortened depth are obtained. The data from all cores were combined to obtain a composite record using the Fisher method. Comparison between stacked inclination and declination records of lake Moreno and results obtained in previous works, lake Escondido (Gogorza et al., 1999; Gogorza et al., 2002) and lake El Trébol (Irurzun et al., 2008), shows good agreement. This agreement made possible to transform the stacked curves into time series that spans the interval 11 and 21 14C kyr B.P. Rock magnetic properties of the sediments cores showed uniform magnetic mineralogy and grain size, suggesting that they were suitable for relative paleointensity studies. The remanent magnetization at 20mT (NRM20mT) was normalized using the anhysteric remanent magnetization at 20mT (ARM20mT), the saturation of the isothermal remanent magnetization at 20mT (SIRM20mT) and the low field magnetic susceptibility {k}. Coherence analysis showed that the normalized records were not affected by local environmental conditions. The recorded pseudo-Thellier paleointensity was compared with records obtained from conventional normalizing methods. Comparing the paleointensity curves with others obtained previously in other lakes in the area has allowed us to reach reliable conclusions about centennial-scale features. References: Gogorza, C.S.G., Sinito, A.M., Di Tommaso, I., Vilas, J.F., Creer, K., Núnez, H. Holocene Geomagnetic Secular Variations Recorded by Sediments from Escondido lake (South Argentina). Earth, Planets and Space, V51(2), 93- 106. 1999. Gogorza, C.S.G., Sinito, A

  4. Erosion of the Alps: use of Rb-Sr isotopic data from molassic sediments to identify the ages of the metamorphism recorded by the eroded rocks; Erosion des Alpes: histoire metamorphique des roches erodees par l`analyse du couple Rb-Sr des sediments molassiques

    Energy Technology Data Exchange (ETDEWEB)

    Henry, P; Deloule, E [Centre National de la Recherche Scientifique (CNRS), 54 - Nancy (France). Centre de Recherches Petrographiques et Geochimiques; Michard, A [Aix-Marseille-3 Univ., 13 - Marseille (France)

    1994-06-01

    Rb-Sr isotopic data from Oligocene and Miocene peri-alpine molassic sediments allow us to identify the different periods for which the eroded rocks have or have not recorded an alpine metamorphism. The Chattian and the Burdigalian sediments result from the erosion of rocks for which the latest metamorphic event was variscan, while the Stampian, Aquitanian and ``Helvetian`` sediments show evidence for the erosion of rocks which have recorded alpine metamorphic events. The application of this method to old detrital sediments could permit determination of the ages of the tectonic events which occurred in the sediment source regions. (authors). 18 refs., 6 figs.

  5. Earthquake-induced soft-sediment deformations and seismically amplified erosion rates recorded in varved sediments of Köyceğiz Lake (SW Turkey)

    KAUST Repository

    Avsar, Ulas; Jonsson, Sigurjon; Avşar, Ö zgü r; Schmidt, Sabine

    2016-01-01

    sequence of Köyceğiz Lake (SW Turkey) that we compare with estimated peak ground acceleration (PGA) values of several nearby earthquakes. We find that earthquakes exceeding estimated PGA values of ca. 20 cm/s2 can induce soft-sediment deformations (SSD

  6. Recording of the Holocene sediment infilling in a confined tide-dominated estuary: the bay of Brest (Britanny, France)

    Science.gov (United States)

    Gregoire, Gwendoline; Le Roy, Pascal; Ehrhold, Axel; Jouet, Gwenael; Garlan, Thierry

    2016-04-01

    Modern estuaries constitute key areas for the preservation of sedimentary deposits related to the Holocene period. Several previous studies using stratigraphic reconstructions in such environments allowed to characterise the major parameters controlling the Holocene transgressive sequence and to decipher their respective role in the sedimentary infill: (1) the evolution of main hydrologic factors (wave or tide-dominated environment), (2) the sea level fluctuation and (3) the morphologies of the bedrock and the coastline. Nevertheless, the timing of the transgressive deposits and the detailed facies need to be precise in regard to the stratigraphic schemes. The Bay of Brest (Western Brittany, France) offers the opportunity to examine these points and to compare with previous studies. It constitutes an original tide-dominated estuary that communicates to the open sea (Iroise Sea) by a narrow strait. Two main rivers (Aulne and Elorn) are connected to a submerged paleovalleys network that was incised in the Paleozoic basement during lowstands and still preserved in the present morphology. It delineates the central basin surrounded by tidal flat located in sheltered area. The analysis of high and very-high resolution seismic lines recorded through the whole bay combined with sediment cores (up to 4.5 m long) and radiocarbon dating allow to precise the architecture and the timing of the thick Holocene coastal wedge. It is preserved from the valley network to the shore and presents a longitudinal variability (downstream-upstream evolution). The infill is divided into two successive stages (corresponding to the transgressive and highstand system tracts) which laterally evolve from the paleo-valley to the coast. Two units constitute the transgressive system tract. The oldest, dated from 8200 to 7000 cal B.P. is composed of fine-grained, organic-rich tidal flat deposits located in the sheltered area and organised in levees on the terrace bordering the paleo-valley. A tidal

  7. Coastal lagoon sediments as a recorder of Holocene landscape evolution and sea-level development: Samsø, southern Kattegat Sea, Denmark

    DEFF Research Database (Denmark)

    Sander, Lasse; Fruergaard, Mikkel; Johannessen, Peter N.

    on the fine-grained (lagoonal) sections of the cores. Age control was facilitated using radiocarbon and optically stimulated luminescence dating. Our data produced a surprisingly consistent pattern for the sedimentary successions found in the lagoons. The initial transgression can be identified along...... with the onset of deposition of fine-grained, organic-rich lagoonal sediments. The subsequent truncation and partial erosion of the lagoon sediments can be related to a decreasing sea-level. Based on these findings, we suggest a conceptual model that allows inferring age and elevation of transgressive...... and regressive stages from the lagoon sediments. Indication of geomorphological developments occurring in proximity to the lagoons (barrier formation, overwashing, dune formation) is further recorded in the deposits. These data can be used to support the proposed reconstruction of Samsø’s landscape evolution...

  8. Mercury levels in fish, invertebrates and sediment in a recently recorded polluted area (Nissum Broad, western Limfjord, Denmark)

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Møhlenberg, Flemming; Ulrik Riisgård, Hans

    1983-01-01

    High concentrations of mercury were measured in sediment and animals collected in the immediate vicinity of a closed-down chemical factory. Sediment contained up to 22 ppm (dry wt) of mercury, deposit-feeding bivalves between 1.4 and 4.4 ppm (wet wt), suspension-feeding bivalves between 0.9 and 1...

  9. Records of pan (floodplain wetland) sedimentation as an approach for post-hoc investigation of the hydrological impacts of dam impoundment: The Pongolo river, KwaZulu-Natal.

    Science.gov (United States)

    Heath, S K; Plater, A J

    2010-07-01

    River impoundment by dams has far-reaching consequences for downstream floodplains in terms of hydrology, water quality, geomorphology, ecology and ecosystem services. With the imperative of economic development, there is the danger that potential environmental impacts are not assessed adequately or monitored appropriately. Here, an investigation of sediment composition of two pans (floodplain wetlands) in the Pongolo River floodplain, KwaZulu-Natal, downstream of the Pongolapoort dam constructed in 1974, is considered as a method for post-hoc assessment of the impacts on river hydrology, sediment supply and water quality. Bumbe and Sokhunti pans have contrasting hydrological regimes in terms of their connection to the main Pongolo channel - Bumbe is a shallow ephemeral pan and Sokhunti is a deep, perennial water body. The results of X-ray fluorescence (XRF) geochemical analysis of their sediment records over a depth of >1 m show that whilst the two pans exhibit similar sediment composition and variability in their lower part, Bumbe pan exhibits a shift toward increased fine-grained mineral supply and associated nutrient influx at a depth of c. 45 cm whilst Sokhunti pan is characterised by increased biogenic productivity at a depth of c. 26 cm due to enhanced nutrient status. The underlying cause is interpreted as a shift in hydrology to a 'post-dam' flow regime of reduced flood frequencies with more regular baseline flows which reduce the average flow velocity. In addition, Sokhunti shows a greater sensitivity to soil influx during flood events due to the nature of its 'background' of autochthonous biogenic sedimentation. The timing of the overall shift in sediment composition and the dates of the mineral inwash events are not well defined, but the potential for these wetlands as sensitive recorders of dam-induced changes in floodplain hydrology, especially those with a similar setting to Sokhunti pan, is clearly demonstrated. Copyright 2010 Elsevier Ltd. All

  10. First High-Resolution Record of Late Quaternary Environmental Changes in the Amundsen Sea, West Antarctica, Revealed by Multi-proxy Analysis of Drift Sediments

    Science.gov (United States)

    Horrocks, J.; Ó Cofaigh, C.; Lloyd, J. M.; Hillenbrand, C. D.; Kuhn, G.; Smith, J.; Ehrmann, W. U.; Esper, O.

    2015-12-01

    The Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) is experiencing rapid mass loss and there is a pressing need to place the contemporary ice-sheet changes into a longer term context. The continental rise in this region is characterised by large sediment mounds that are shaped by westward flowing bottom currents and that resemble contouritic drifts existing offshore from the Antarctic Peninsula. Similar to the Antarctic Peninsula drifts, marine sediment cores from the poorly studied sediment mounds in the Amundsen Sea have the potential to provide reliable records of dynamical ice-sheet behaviour in West Antarctica and palaeoceanographic changes in the Southern Ocean during the Late Quaternary that can be reconstructed from their terrestrial, biogenic and authigenic components. Here we use multi-proxy data from three sediment cores recovered from two of the Amundsen Sea mounds to present the first high-resolution study of environmental changes on this part of the West Antarctic continental margin over the glacial-interglacial cycles of the Late Quaternary. Age constraints for the records are derived from biostratigraphy, AMS 14C dates and lithostratigraphy. We focus on the investigation of processes for drift formation, thereby using grain size and sortable silt data to reconstruct changes in bottom current speed and to identify episodes of current winnowing. Data on geochemical and mineralogical sediment composition and physical properties are used to infer both changes in terrigenous sediment supply in response to the advance and retreat of the WAIS across the Amundsen Sea shelf and changes in biological productivity that are mainly controlled by the duration of annual sea-ice coverage. We compare our data sets from the Amundsen Sea mounds to those from the well-studied Antarctic Peninsula drifts, thereby highlighting similarities and discrepancies in depositional processes and climatically-driven environmental changes.

  11. Optically stimulated luminescence dating as a tool for calculating sedimentation rates in Chinese loess: comparisons with grain-size records

    DEFF Research Database (Denmark)

    Stevens, Thomas; Lu, HY

    2009-01-01

    Understanding loess sedimentation rates is crucial for constraining past atmospheric dust dynamics, regional climatic change and local depositional environments. However, the derivation of loess sedimentation rates is complicated by the lack of available methods for independent calculation......) the influences on sediment grain-size and accumulation; and (ii) their relationship through time and across the depositional region. This uncertainty has led to the widespread use of assumptions concerning the relationship between sedimentation rate and grain-size in order to derive age models and climate...... reconstructions. To address this uncertainty, detailed independent age models, based on optically stimulated luminescence dating, undertaken at 10 to 40 cm intervals at five sections across the Loess Plateau in China, have been used to calculate sedimentation rates and make comparisons with grain-size changes...

  12. Evidence for Isostatic Emergence and Holocene Environmental Change Recorded in Chironomid Assemblages and Sediment Composition of Coastal Lake T1 in SW Greenland

    Science.gov (United States)

    Berman, K.; Axford, Y.; Lasher, G. E.

    2017-12-01

    Multi-proxy analysis of a coastal lake in southwest Greenland near Nuuk provides evidence for regional environmental changes, including the timing of isostatic rebound and the temperature history of the area. T1 (informal name) is a small lake 50 km south of Nuuk, at 17.5 m elevation and currently isolated from glacial meltwater drainage. The lake's sediment record begins approximately 9500 cal years BP, when the site was submerged beneath sea level due to glacial isostatic depression following the Last Glacial Maximum. The record captures the transition of the environment from a submerged, glacially-influenced marine site to a non-glacially fed (and initially meromictic) freshwater lake 8600 cal years BP. Magnetic susceptibility, a proxy for sediment minerogenic content, decreased rapidly from 9500 to 8600 years BP, before abruptly stabilizing and remaining relatively low and steady for the rest of the record. The transition to a lacustrine environment was characterized by a rapid and relatively simultaneous increase in primary productivity (inferred from biogenic silica concentrations) and shift towards terrestrial versus marine sources of organic matter (inferred from carbon:nitrogen ratios and nitrogen isotopes) between 8700 and 8400 years BP. Together, these proxies and the presence of marine shells below the transition provide robust evidence for the transition from a marine environment to a freshwater lake in response to regional postglacial isostatic rebound. Within the Holocene, measures of bulk sediment composition (e.g., biogenic silica, loss-on-ignition and magnetic susceptibility) are relatively stable. Chironomid (Insecta: Diptera: Chironomidae) assemblages, which in some environments are quantitative proxies for summer temperature changes, show species-level shifts within the Holocene that will be interpreted in this presentation alongside indicators of landscape change including carbon:nitrogen ratios, bulk sediment spectral reflectance and bulk

  13. Chronology of Late Saalian and Middle Weichselian episodes of ice-free lacustrine sedimentation recorded in the Arumetsa section, southwestern Estonia

    Directory of Open Access Journals (Sweden)

    Maris Rattas

    2010-06-01

    Full Text Available The information obtained from a 21 m thick open-pit section of silty-clayey sediments in the Arumetsa bedrock valley, southwestern Estonia, revealed that lacustrine to glaciolacustrine sedimentation at the site started prior to 151 ka ago and lasted to about the end of marine isotope stage 6 (MIS6 at 130 ka. Further down from the 151 ka age-level to the bottom of the buried valley there are ca 60 m of lacustrine fine-grained sediments, the age of which remains still unclear. The Late Saalian sediments at Arumetsa are discordantly overlain by Middle Weichselian clay, silt and sand, deposited between ca 44 and 37 ka ago. As testified by optically stimulated luminescence (OSL ages, and pollen and diatom record, the Middle Weichselian fine-grained sediments contain redeposited Holsteinian but no Eemian pollen, and have not been fully bleached during deposition. Chronological, microfossil and sedimentological data show two hiatuses in the Arumetsa section. The first hiatus has left no sedimentary evidence for the period between ca 130 ka and 44 ka ago (MIS5 to older half of MIS3. The younger hiatus from ca 37 to 22 ka occurs between the Middle Weichselian lacustrine silt and the Late Weichselian till layer on top of the section.

  14. ERUPTION TO DOSE: COUPLING A TEPHRA DISPERSAL MODEL WITHIN A PERFORMANCE ASSESSMENT FRAMEWORK

    International Nuclear Information System (INIS)

    G. N. Keating, J. Pelletier

    2005-01-01

    The tephra dispersal model used by the Yucca Mountain Project (YMP) to evaluate the potential consequences of a volcanic eruption through the waste repository must incorporate simplifications in order to function within a large Monte-Carlo style performance assessment framework. That is, the explicit physics of the conduit, vent, and eruption column processes are abstracted to a 2-D, steady-state advection-dispersion model (ASHPLUME) that can be run quickly over thousands of realizations of the overall system model. Given the continuous development of tephra dispersal modeling techniques in the last few years, we evaluated the adequacy of this simplified model for its intended purpose within the YMP total system performance assessment (TSPA) model. We evaluated uncertainties inherent in model simplifications including (1) instantaneous, steady-state vs. unsteady eruption, which affects column height, (2) constant wind conditions, and (3) power-law distribution of the tephra blanket; comparisons were made to other models and published ash distributions. Spatial statistics are useful for evaluating differences in these model output vs. results using more complex wind, column height, and tephra deposition patterns. However, in order to assess the adequacy of the model for its intended use in TSPA, we evaluated the propagation of these uncertainties through FAR, the YMP ash redistribution model, which utilizes ASHPLUME tephra deposition results to calculate the concentration of nuclear waste-contaminated tephra at a dose-receptor population as a result of sedimentary transport and mixing processes on the landscape. Questions we sought to answer include: (1) what conditions of unsteadiness, wind variability, or departure from simplified tephra distribution result in significant effects on waste concentration (related to dose calculated for the receptor population)? (2) What criteria can be established for the adequacy of a tephra dispersal model within the TSPA

  15. Earthquake-induced soft-sediment deformations and seismically amplified erosion rates recorded in varved sediments of Köyceğiz Lake (SW Turkey)

    KAUST Repository

    Avsar, Ulas

    2016-06-06

    Earthquake-triggered landslides amplify erosion rates in catchments, i.e. catchment response to seismic shocks (CR). In addition to historical eyewitness accounts of muddy rivers implying CRs after large earthquakes, several studies have quantitatively reported increased sediment concentrations in rivers after earthquakes. However, only a few paleolimnological studies could detect CRs within lacustrine sedimentary sequences as siliciclastic-enriched intercalations within background sedimentation. Since siliciclastic-enriched intercalations can easily be of non-seismic origin, their temporal correlation with nearby earthquakes is crucial to assign a seismic triggering mechanism. In most cases, either uncertainties in dating methods or the lack of recent seismic activity has prevented reliable temporal correlations, making the seismic origin of observed sedimentary events questionable. Here, we attempt to remove this question mark by presenting sedimentary traces of CRs in the 370-year-long varved sequence of Köyceğiz Lake (SW Turkey) that we compare with estimated peak ground acceleration (PGA) values of several nearby earthquakes. We find that earthquakes exceeding estimated PGA values of ca. 20 cm/s2 can induce soft-sediment deformations (SSD), while CRs seem only to be triggered by PGA levels higher than 70 cm/s2. In Köyceğiz Lake, CRs produce Cr- and Ni-enriched sedimentation due to the seismically mobilized soils derived from ultramafic rocks in the catchment. Given the varve chronology, the residence time of the seismically mobilized material in the catchment is determined to be 5 to 10 years.

  16. Environmental magnetic and petroleum hydrocarbons records in sediment cores from the north east coast of Tamilnadu, Bay of Bengal, India.

    Science.gov (United States)

    Venkatachalapathy, R; Veerasingam, S; Basavaiah, N; Ramkumar, T; Deenadayalan, K

    2011-04-01

    In this study, mineral magnetic properties and petroleum hydrocarbons were statistically analysed in four sediment cores (C1, A1, T1 and K1) from the north east coast of Tamilnadu, India to examine the feasibility of PHC concentrations assessment using magnetic susceptibility. The C1 and A1 cores reveal a clear horizon of increase in PHC above 35 and 50 cm respectively suggesting the excess anthropogenic loading occurred in the recent past. Magnetic properties which were enhanced in the upper part of the sediment cores were the result of ferrimagnetic minerals from anthropogenic sources. Factor analysis confirmed that the input of magnetic minerals and petroleum hydrocarbons in Chennai coastal sediments are derived from the same sources. The present study shows that instead of expensive and destructive PHC chemical methods, magnetic susceptibility is found to be a suitable, cheap and rapid method for detailed study of petroleum hydrocarbon contamination in marine sediments. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Variability in terrigenous sediment supply offshore of the Rio de la Plata (Uruguay) recording the continental climatic history over the past 1200 years

    Science.gov (United States)

    Perez, L.; García-Rodríguez, F.; Hanebuth, T. J. J.

    2015-04-01

    The continental shelf adjacent to the Río de la Plata (RdlP) exhibits extremely complex hydrographic and ecological characteristics which are of great socio-economic importance. Since the long-term environmental variations related to the atmospheric (wind fields), hydrologic (freshwater plume), and oceanographic (currents and fronts) regimes are little known, the aim of this study is to reconstruct the changes in the terrigenous input into the inner continental shelf during the Late Holocene period (associated with the RdlP sediment discharge) and to unravel the climatic forcing mechanisms behind them. To achieve this, we retrieved a 10 m long sediment core from the RdlP mud depocenter at a depth of 57 m (GeoB 13813-4). The radiocarbon age control indicated an extremely high sedimentation rate of 0.8 cm per year, encompassing the past 1200 years (750-2000 AD). We used element ratios (Ti / Ca, Fe / Ca, Ti / Al, Fe / K) as regional proxies for the fluvial input signal, and the variations in relative abundance of salinity-indicative diatom groups (freshwater vs. marine-brackish) to assess the variability in terrigenous water and sediment discharge. Ti / Ca, Fe / Ca, Ti / Al, Fe / K and the freshwater diatom group showed the lowest values between 850 and 1300 AD, while the highest values occurred between 1300 and 1850 AD. The variations in the sedimentary record can be attributed to such regional and global climatic episodes as the Medieval Climatic Anomaly (MCA) and the Little Ice Age (LIA), both of which had a significant impact on rainfall and wind patterns over the region. During the MCA, a northward migration of the Intertropical Confluence Zone (ITCZ) could explain the lowest element ratios (indicative of a lower terrigenous input) and a marine-dominated diatom record, both indicative of a reduced RdlP freshwater plume. In contrast during the LIA, the southward migration of the ITCZ accompanied by El Niño-like state conditions may have led to an expansion of

  18. Tephrostratigraphy and geochemical fingerprinting of the Mangaone Subgroup tephra beds, Okataina Volcanic Centre, New Zealand

    International Nuclear Information System (INIS)

    Smith, V.C.; Shane, P.; Smith, I.E.M.

    2002-01-01

    The Mangaone Subgroup is a sequence of 14 plinian tephra beds erupted from the Okataina Volcanic Centre in North Island, New Zealand, that are bracketed between the regional marker beds of Rotoehu Tephra (50-60 ka) and Oruanui Tephra (26 ka). The Mangaone Subgroup tephra beds are separated by thin paleosols in ascending stratigraphic order: unit A, unit B, unit C, Pupuwharau Tephra (new), Pongakawa Tephra (new), Maketu, Te Mahoe, Hauparu, unit G, unit H, Mangaone, Awakeri, Omataroa, and unit L. Geochemical fingerprinting of the glass and phenocryst phases allows clear subdivision of the Mangaone Subgroup into two stratigraphic intervals. Units A-G are rhyodacites and low-SiO 2 rhyolites (71-75.5 wt% SiO 2 glass; 68-71 wt% SiO 2 whole rock), clinopyroxene bearing, with calcic plagioclase (An 40-60 ) and magnesian orthopyroxene (En 60-70 ), and they display high eruption temperatures (870-940 degrees C) and oxygen fugacities (-log f O 2 11.66-10.40). Some of these units are compositionally heterogeneous in the glass phase (SiO 2 range up to 8 wt%), especially unit A, Ngamotu, Te Mahoe, and Hauparu tephra beds. Units A-G can easily be distinguished from other Taupo Volcanic Zone tephra erupted in the last c. 60 000 yr. Units H-L are high SiO 2 rhyolites (76-78 wt% SiO 2 glass; 71.5-75 wt% SiO 2 whole rock), which contain sodic plagioclase (An 30-40 ), low-Mg orthopyroxene (En 50-60 ), and display lower eruption temperatures (755-830 degrees C) and oxygen fugacities (-log f O 2 = 14.7-12.93). Compositional differences in titanomagnetite and ilmenite can also be used to distinguish them from older units. The two compositional groups also form distinct T-f O 2 trends. The shift in chemical affinity follows the large volume Hauparu eruption, and coincides with the likely geographic shift in vent location to the eastern margin of the caldera complex. Tephra beds that both predate and postdate the Mangaone Subgroup also reflect changes in magma type and vent location. The

  19. Beyond eruptive scenarios: assessing tephra fallout hazard from Neapolitan volcanoes.

    Science.gov (United States)

    Sandri, Laura; Costa, Antonio; Selva, Jacopo; Tonini, Roberto; Macedonio, Giovanni; Folch, Arnau; Sulpizio, Roberto

    2016-04-12

    Assessment of volcanic hazards is necessary for risk mitigation. Typically, hazard assessment is based on one or a few, subjectively chosen representative eruptive scenarios, which use a specific combination of eruptive sizes and intensities to represent a particular size class of eruption. While such eruptive scenarios use a range of representative members to capture a range of eruptive sizes and intensities in order to reflect a wider size class, a scenario approach neglects to account for the intrinsic variability of volcanic eruptions, and implicitly assumes that inter-class size variability (i.e. size difference between different eruptive size classes) dominates over intra-class size variability (i.e. size difference within an eruptive size class), the latter of which is treated as negligible. So far, no quantitative study has been undertaken to verify such an assumption. Here, we adopt a novel Probabilistic Volcanic Hazard Analysis (PVHA) strategy, which accounts for intrinsic eruptive variabilities, to quantify the tephra fallout hazard in the Campania area. We compare the results of the new probabilistic approach with the classical scenario approach. The results allow for determining whether a simplified scenario approach can be considered valid, and for quantifying the bias which arises when full variability is not accounted for.

  20. Contrasting Responses of the Humboldt Current Ecosystem between the Holocene and MIS5e Interglacials Revealed from Multiple Sediment Records

    Science.gov (United States)

    Salvatteci, R.; Schneider, R. R.; Blanz, T.; Martinez, P.; Crosta, X.

    2016-12-01

    The Humboldt Current Ecosystem (HCE) off Peru yields about 10% of the global fish catch, producing more fish per unit area than any other region in the world. The high productivity is maintained by the upwelling of cold, nutrient-rich water from the oxygen minimum zone (OMZ), driven by strong trade winds. However, the potential impacts of climate change on upwelling dynamics and oceanographic conditions in the near future are uncertain, threatening local and global economies. Here, we unravel the response of the HCE to contrasting climatic conditions during the last two interglacials (i.e. Holocene and MIS5e) providing an independent insight about the relation between climatic factors and upwelling and productivity dynamics. For this purpose, we used multiple cores to reconstruct past changes in OMZ and upwelling intensity, productivity and fish biomass variability. Chronologies for the Holocene were obtained by multiple 14C ages and laminae correlations among cores, while for the MIS5e they were mainly done by correlation of prominent features in several proxies with other published records. We used a multiproxy approach including alkenones to reconstruct sea surface temperatures, δ15N as a proxy for water column denitrification, redox sensitive metals as proxies for sediment redox conditions, and diatom and fish debris assemblages to reconstruct ecological changes. The results show a very different response of the HCE to climate conditions during the last 2 interglacials, likely driven by changes in Tropical Pacific dynamics. During the Holocene we find that 1) the Late Holocene exhibits higher multi-centennial scale variability compared to the Early Holocene, 2) increased upwelling and a weak OMZ during the mid-Holocene, and 3) long term increase in productivity (diatoms and fishes) from the Early to the Late Holocene. During the MIS5e we find an 1) intense OMZ, 2) strong water column stratification, 3) high siliceous biomass, and 4) low fish biomass compared

  1. Stable isotope record in annually laminated lake sediments from Lake Żabińskie (NE Poland) for the last millennium.

    Science.gov (United States)

    Gabryś, Alicja; Piotrowska, Natalia; Tylmann, Wojciech; Bonk, Alicja; Filipiak, Janusz; Wacnik, Agnieszka; Hernandez-Almeida, Ivan; Grosjean, Martin

    2015-04-01

    Stable isotope record of carbon (13C) and oxygen (18O) has been analysed from an annually laminated sediment from Lake Zabinskie (Mazurian Lakeland, NE Poland) with high resolution (1-3 yrs). The sediment layers which were formed in each year during the last millennium contain information about environmental changes in the past. The calcite layers are formed in lake sediment in warm months of the year, therefore the reconstruction of summer climate variables in the past is potentially possible. The investigation of correlation between isotope dataset and instrumental climate data for years 1897-2008 AD confirmed that theory. The record of temperature, precipitation and SPEI (Standardised Precipitation Evaporation Index) coefficient, which is a combination of both temperature and precipitation, was tested. The strongest linear correlations were found for most samples for June, July, August (JJA) months but in some cases the correlation coefficient was stronger when also May was taken into account. For the whole 120-yrs series the correlation between δ18O and average JJA temperature is 0.007, average JJA precipitation is 0.16 and average JJA SPEI is 0.20. Analyzing the results for 1897-2008 we can distinguish period 1960-2008 with relevantly stronger correlations: R(temperature) = 0.19, R(precipitation) = 0.20 and R(SPEI) = 0.45. This period is connected with cessation of human activity close to Lake Zabinskie. Reconstruction of climate variables for the last millennium was made using transfer function obtained for calibration period (1897-2008). Reconstructions showed that known climate extremes like Medieval Warm Period, Little Ice Age with Sporer (1420-1570), Maunder (1645-1715) and Dalton (1790-1820) Minimum was recorded in sediment from Lake Zabinskie. The presented study is a part of the project "Climate of northern Poland during the last 1000 years: Constraining the future with the past (CLIMPOL)", funded within Polish-Swiss Research Programme. http://www.climpol.ug.edu.pl

  2. n-Alkanes in sediments from the Yellow River Estuary, China: Occurrence, sources and historical sedimentary record.

    Science.gov (United States)

    Wang, Shanshan; Liu, Guijian; Yuan, Zijiao; Da, Chunnian

    2018-04-15

    A total of 21 surface sediments from the Yellow River Estuary (YRE) and a sediment core from the abandoned Old Yellow River Estuary (OYRE) were analyzed for n-alkanes using gas chromatography-mass spectrometry (GC-MS). n-Alkanes in the range C 12 -C 33 and C 13 -C 34 were identified in the surface sediments and the core, respectively. The homologous series were mainly bimodal distribution pattern without odd/even predominance in the YRE and OYRE. The total n-alkanes concentrations in the surface sediments ranged from 0.356 to 0.572mg/kg, with a mean of 0.434mg/kg on dry wt. Evaluation of n-alkanes proxies indicated that the aliphatic hydrocarbons in the surface sediments were derived mainly from a petrogenic source with a relatively low contribution of submerged/floating macrophytes, terrestrial and emergent plants. The dated core covered the time period 1925-2012 and the mean sedimentation rate was ca. 0.5cm/yr. The total n-alkanes concentrations in the core ranged from 0.0394 to 0.941mg/kg, with a mean of 0.180mg/kg. The temporal evolution of n-alkanes reflected the historical input of aliphatic hydrocarbons and was consistent with local and regional anthropogenic activity. In general, the investigation on the sediment core revealed a trend of regional environmental change and the role of anthropogenic activity in environmental change. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Greigite (Fe3S4) as an indicator of drought - The 1912-1994 sediment magnetic record from White Rock Lake, Dallas, Texas, USA

    Science.gov (United States)

    Reynolds, R.L.; Rosenbaum, J.G.; Van Metre, P.; Tuttle, M.; Callender, E.; Goldin, A.

    1999-01-01

    Combined magnetic and geochemical studies were conducted on sediments from White Rock Lake, a reservoir in suburban Dallas (USA), to investigate how land use has affected sediment and water quality since the reservoir was filled in 1912. The chronology of a 167-cm-long core is constrained by the recognition of the pre-reservoir surface and by 137Cs results. In the reservoir sediments, magnetic susceptibility (MS) and isothermal remanent magnetization (IRM) are largely carried by detrital titanomagnetite that originally formed in igneous rocks. Titanomagnetite and associated hematite are the dominant iron oxides in a sample from the surficial deposit in the watershed but are absent in the underlying Austin Chalk. Therefore, these minerals were transported by wind into the watershed. After about 1960, systematic decreases in Ti, Fe, and Al suggest diminished input of detrital Fe-Ti oxides from the surficial deposits. MS and IRM remain constant over this interval, however, implying compensation by an increase in strongly magnetic material derived from human activity. Anthropogenic magnetite in rust and ferrite spherules (from fly ash?) are more common in sediment deposited after about 1970 than before and may account for the constant magnetization despite the implied decrease in detrital Fe-Ti oxides. An unexpected finding is the presence of authigenic greigite (Fe3S4), the abundance of which is at least partly controlled by climate. Greigite is common in sediments that predate about 1975, with zones of concentration indicated by relatively high IRM/MS. High greigite contents in sediment deposited during the early to mid-1950s and during the mid-1930s correspond to several-year periods of below-average precipitation and drought from historical records. Relatively long water-residence times in the reservoir during these periods may have led to elevated levels of sulfate available for bacterial sulfate reduction. The sulfate was probably derived via the oxidation of

  4. The history of Cesium-137 liquid emissions by Mühleberg Nuclear Power Plant (Switzerland) is recorded in Lake Biel sediments

    Science.gov (United States)

    Girardclos, Stéphanie; Faessler, Jérôme; Loizeau, Jean-Luc; Zehringer, Markus

    2014-05-01

    Lake sediments record changes happening in their upstream river catchment and regional environment which includes traces of artificial radionuclides emissions deriving from human activities. 137Cs emissions started worldwide in the early 1950's and peaked in 1963-64 due to nuclear bomb tests in the high atmosphere. A second 137Cs activity peak, due to the 1986 Chernobyl catastrophe is recorded in sediment archives from central Europe. These two events (1963/64 and 1986) serve routinely as time markers for recent lake records. Nuclear Power Plants (NPPs) are often constructed along river course for cooling purposes. Since 1972, Mühleberg NPP (central Switzerland) lies 18 km upstream Lake Biel and releases radioactive liquid emissions into the Aare river which adds to the diffuse - above mentioned - radioactive pollution, as revealed by Albrecht et al. (1995; 1998) and recently confirmed by Thevenon et al. (2013) from Lake Biel sediments. The water of Lake Biel is used as drinking water for ca. 60'000 inhabitants and its outflowing water is further used by downstream cities lying on the Aare-Rhine course such as Basel (200'000 inhab.) In this study, the 137Cs activity curve of a 90-cm-long sediment core (BIE10-8), retrieved in April 2010 from the central Lake Biel basin at ca. 50 m depth, and measured by gamma ray spectrometry using high resolution germanium detectors, confirms previous work and reveals a new peak for the year 1998-2000, as observed by Thevenon et al. (2013). This peak is most certainly due to Mühleberg NPP as shown by the good correlation with declared 137Cs liquid emissions indicating a significant increase in 1998-99. Decay corrected activity data, converted into 137Cs fluxes, point to water pollution by Mühleberg NPP in 1975-1985 as being similar to those linked to the catastrophic events in 1963-64 and 1986 (about 75%). As former study showed that Lake Biel sediments scavenge only a portion of the total radionuclide in water, i.e. 30-55% for

  5. Sediment provenance in contractional orogens: The detrital zircon record from modern rivers in the Andean fold-thrust belt and foreland basin of western Argentina

    Science.gov (United States)

    Capaldi, Tomas N.; Horton, Brian K.; McKenzie, N. Ryan; Stockli, Daniel F.; Odlum, Margaret L.

    2017-12-01

    This study analyzes detrital zircon U-Pb age populations from Andean rivers to assess whether active synorogenic sedimentation accurately records proportional contributions from varied bedrock source units across different drainage areas. Samples of modern river sand were collected from west-central Argentina (28-33°S), where the Andes are characterized by active uplift and deposition in diverse contractional provinces, including (1) hinterland, (2) wedge-top, (3) proximal foreland, and (4) distal broken foreland basin settings. Potential controls on sediment provenance were evaluated by comparing river U-Pb age distributions with predicted age spectra generated by a sediment mixing model weighted by relative catchment exposure (outcrop) areas for different source units. Several statistical measures (similarity, likeness, and cross-correlation) are employed to compare how well the area-weighted model predicts modern river age populations. (1) Hinterland basin provenance is influenced by local relief generated along thrust-bounded ranges and high zircon fertility of exposed crystalline basement. (2) Wedge-top (piggyback) basin provenance is controlled by variable lithologic durability among thrust-belt bedrock sources and recycled basin sediments. (3) Proximal foreland (foredeep) basin provenance of rivers and fluvial megafans accurately reflect regional bedrock distributions, with limited effects of zircon fertility and lithologic durability in large (>20,000 km2) second-order drainage systems. (4) In distal broken segments of the foreland basin, regional provenance signatures from thrust-belt and hinterland areas are diluted by local contributions from foreland basement-cored uplifts.

  6. A 20-15 ka high-resolution paleomagnetic secular variation record from Black Sea sediments - no evidence for the 'Hilina Pali excursion'?

    Science.gov (United States)

    Liu, Jiabo; Nowaczyk, Norbert R.; Frank, Ute; Arz, Helge W.

    2018-06-01

    A comprehensive magnetostratigraphic investigation on sixteen sediment cores from the southeastern Black Sea yielded a very detailed high-quality paleosecular variation (PSV) record spanning from 20 to 15 ka. The age models are based on radiocarbon dating, stratigraphic correlation, and tephrochronology. Further age constraints were obtained by correlating four meltwater events, described from the western Black Sea, ranging in age from about 17 to 15 ka, with maxima in K/Ti ratios, obtained from X-ray fluorescence (XRF) scanning, and minima in S-ratios, reflecting increased hematite content, in the studied cores. Since the sedimentation rates in the investigated time window are up to 50 cm ka-1, the obtained PSVs records enabled a stacking using 50-yr bins. A directional anomaly at 18.5 ka, associated with pronounced swings in inclination and declination, as well as a low in relative paleointensity (rPI), is probably contemporaneous with the Hilina Pali excursion, originally reported from Hawaiian lava flows. However, virtual geomagnetic poles (VGPs) calculated from Black Sea sediments are not located at latitudes lower than 60°N, which denotes normal, though pronounced secular variations. During the postulated Hilina Pali excursion, the VGPs calculated from Black Sea data migrated clockwise only along the coasts of the Arctic Ocean from NE Canada (20.0 ka), via Alaska (18.6 ka) and NE Siberia (18.0 ka) to Svalbard (17.0 ka), then looping clockwise through the Eastern Arctic Ocean.

  7. Expanded spatial extent of the Medieval Climate Anomaly revealed in lake-sediment records across the boreal region in northwest Ontario.

    Science.gov (United States)

    Laird, Kathleen R; Haig, Heather A; Ma, Susan; Kingsbury, Melanie V; Brown, Thomas A; Lewis, C F Michael; Oglesby, Robert J; Cumming, Brian F

    2012-09-01

    Multi-decadal to centennial-scale shifts in effective moisture over the past two millennia are inferred from sedimentary records from six lakes spanning a ~250 km region in northwest Ontario. This is the first regional application of a technique developed to reconstruct drought from drainage lakes (open lakes with surface outlets). This regional network of proxy drought records is based on individual within-lake calibration models developed using diatom assemblages collected from surface sediments across a water-depth gradient. Analysis of diatom assemblages from sediment cores collected close to the near-shore ecological boundary between benthic and planktonic diatom taxa indicated this boundary shifted over time in all lakes. These shifts are largely dependent on climate-driven influences, and can provide a sensitive record of past drought. Our lake-sediment records indicate two periods of synchronous signals, suggesting a common large-scale climate forcing. The first is a period of prolonged aridity during the Medieval Climate Anomaly (MCA, c. 900-1400 CE). Documentation of aridity across this region expands the known spatial extent of the MCA megadrought into a region that historically has not experienced extreme droughts such as those in central and western north America. The second synchronous period is the recent signal of the past ~100 years, which indicates a change to higher effective moisture that may be related to anthropogenic forcing on climate. This approach has the potential to fill regional gaps, where many previous paleo-lake depth methods (based on deeper centrally located cores) were relatively insensitive. By filling regional gaps, a better understanding of past spatial patterns in drought can be used to assess the sensitivity and realism of climate model projections of future climate change. This type of data is especially important for validating high spatial resolution, regional climate models. © 2012 Blackwell Publishing Ltd.

  8. Lake-sediment record of PAH, mercury, and fly-ash particle deposition near coal-fired power plants in Central Alberta, Canada.

    Science.gov (United States)

    Barst, Benjamin D; Ahad, Jason M E; Rose, Neil L; Jautzy, Josué J; Drevnick, Paul E; Gammon, Paul R; Sanei, Hamed; Savard, Martine M

    2017-12-01

    We report a historical record of atmospheric deposition in dated sediment cores from Hasse Lake, ideally located near both currently and previously operational coal-fired power plants in Central Alberta, Canada. Accumulation rates of spheroidal carbonaceous particles (SCPs), an unambiguous marker of high-temperature fossil-fuel combustion, in the early part of the sediment record (pre-1955) compared well with historical emissions from one of North America's earliest coal-fired power plants (Rossdale) located ∼43 km to the east in the city of Edmonton. Accumulation rates in the latter part of the record (post-1955) suggested inputs from the Wabamun region's plants situated ∼17-25 km to the west. Increasing accumulation rates of SCPs, polycyclic aromatic hydrocarbons (PAHs) and Hg coincided with the previously documented period of peak pollution in the Wabamun region during the late 1960s to early 1970s, although Hg deposition trends were also similar to those found in western North American lakes not directly affected by point sources. A noticeable reduction in contaminant inputs during the 1970s is attributed in part to technological improvements and stricter emission controls. The over one hundred-year historical record of coal-fired power plant emissions documented in Hasse Lake sediments has provided insight into the impact that both environmental regulations and changes in electricity output have had over time. This information is crucial to assessing the current and future role of coal in the world's energy supply. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

  9. The marine isotope stage 1-5 cryptotephra record of Tenaghi Philippon, Greece: Towards a detailed tephrostratigraphic framework for the Eastern Mediterranean region

    Science.gov (United States)

    Wulf, Sabine; Hardiman, Mark J.; Staff, Richard A.; Koutsodendris, Andreas; Appelt, Oona; Blockley, Simon P. E.; Lowe, J. John; Manning, Christina J.; Ottolini, Luisa; Schmitt, Axel K.; Smith, Victoria C.; Tomlinson, Emma L.; Vakhrameeva, Polina; Knipping, Maria; Kotthoff, Ulrich; Milner, Alice M.; Müller, Ulrich C.; Christanis, Kimon; Kalaitzidis, Stavros; Tzedakis, Polychronis C.; Schmiedl, Gerhard; Pross, Jörg

    2018-04-01

    The iconic climate archive of Tenaghi Philippon (TP), NE Greece, allows the study of short-term palaeoclimatic and environmental change throughout the past 1.3 Ma. To provide high-quality age control for detailed palaeoclimate reconstructions based on the TP archive, (crypto)tephra studies of a peat core 'TP-2005' have been carried out for the 0-130 ka interval. The results show that the TP basin is ideally positioned to receive tephra fall from both the Italian and Aegean Arc volcanic provinces. Two visible tephra layers, the Santorini Cape Riva/Y-2 (c. 22 ka) and the Campanian Ignimbrite (CI)/Y-5 (c. 39.8 ka) tephras, and six primary cryptotephra layers, namely the early Holocene E1 tephra from the Aeolian Islands (c. 8.3 ka), the Campanian Y-3 (c. 29 ka) and X-6 tephras (c. 109.5 ka), as well as counterpart tephras TM-18-1d (c. 40.4 ka), TM-23-11 (c. 92.4 ka) and TM-33-1a (c. 116.7 ka) from the Lago Grande di Monticchio sequence (southern Italy), were identified along with repeatedly redeposited Y-2 and CI tephra material. Bayesian modelling of the ages of seven of the primary tephra layers, 60 radiocarbon measurements and 20 palynological control points have been applied to markedly improve the chronology of the TP archive. This revised chronology constrains the age of tephra TM-18-1d to 40.90-41.66 cal ka BP (95.4% range). Several tephra layers identified in the TP record form important isochrons for correlating this archive with other terrestrial (e.g., Lago Grande di Monticchio, Sulmona Basin and Lake Ohrid) and marine (e.g., Adriatic Sea core PRAD 1-2 and Aegean Sea core LC21) palaeoclimate records in the Mediterranean region.

  10. Lake sediment multi-taxon DNA from North Greenland records early post-glacial appearance of vascular plants and accurately tracks environmental changes

    DEFF Research Database (Denmark)

    Epp, L. S.; Gussarova, C.; Boessenkool, S.

    2015-01-01

    temperatures. Lake sediments contain DNA paleorecords of the surrounding ecosystems and can be used to retrieve a variety of organismal groups from a single sample. In this study, we analyzed vascular plant, bryophyte, algal (in particular diatom) and copepod DNA retrieved from a sediment core spanning...... phases, and distinct temporal changes in plant presence were recovered. The plant DNA was mostly in agreement with expected vegetation history, but very early occurrences of vascular plants, including the woody Empetrum nigrum, document terrestrial vegetation very shortly after glacial retreat. Our study...... core. Our DNA record was stratigraphically coherent, with no indication of leaching between layers, and our cross-taxon comparisons were in accordance with previously inferred local ecosystem changes. Authentic ancient plant DNA was retrieved from nearly all layers, both from the marine and the limnic...

  11. Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries.

    Science.gov (United States)

    Thevenon, Florian; Graham, Neil D; Chiaradia, Massimo; Arpagaus, Philippe; Wildi, Walter; Poté, John

    2011-12-15

    This research first focuses on the spatial and temporal patterns of heavy metals from contrasting environments (highly polluted to deepwater sites) of Lake Geneva. The mercury (Hg) and lead (Pb) records from two deepwater sites show that the heavy metal variations before the industrial period are primarily linked to natural weathering input of trace elements. By opposition, the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century, involved the sedimentation of highly metal-contaminated sediments in the area surrounding the WWTP outlet pipe discharge. Eventually, a new Pb isotope record of sediments from Lake Lucerne identifies the long-term increasing anthropogenic lead pollution after ca. 1500, probably due to the development of metallurgical activities during the High Middle Ages. These data furthermore allows to compare the recent anthropogenic sources of water pollution from three of the largest freshwater lakes of Western Europe (lakes Geneva, Lucerne, and Constance). High increases in Pb and Hg highlight the regional impact of industrial pollution after ca. 1750-1850, and the decrease of metal pollution in the 1980s due to the effects of remediation strategies such as the implementation of wastewater treatment plants (WWTPs). However, at all the studied sites, the recent metal concentrations remain higher than pre-industrial levels. Moreover, the local scale pollution data reveal two highly contaminated sites (>100 μg Pb/g dry weight sediment) by industrial activities, during the late-19th and early-20th centuries (Lake Lucerne) and during the second part of the 20th century (Vidy Bay of Lake Geneva). Overall, the regional scale pollution history inferred from the three large and deep perialpine lakes points out at the pollution of water systems by heavy metals during the last two centuries due to the discharge of industrial effluents. Copyright © 2011 Elsevier B.V. All rights reserved.

  12. Post-Wisconsinan Chemical Weathering Rates and Trajectories From a 13,400-Year Sediment Core Record of Lead Isotopic Ratios in Maine

    Science.gov (United States)

    Perry, R. H.; Norton, S. A.; Koons, P. O.; Handley, M.

    2008-12-01

    Lead isotopic ratios recorded in a 5.3-m 13.4-ka 14C-dated lake sediment core from Sargent Mountain Pond, Maine (USA) are interpreted as an archive of post-glacial chemical weathering. Early weathering yielded highly radiogenic sediment from the preferential release of U and Th decay products (206Pb, 207Pb, and 208Pb) from accessory mineral phases in the catchment's predominantly-granitic till and bedrock relative to non-radiogenic 204Pb from the more abundant primary minerals. Values for 207Pb/206Pb in the sediment increased rapidly from 0.799 to 0.814 in the catchment's first 4,000 years of post-Wisconsinan weathering, and thereafter increased only slightly to just prior to the 19th century. Values for 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb decline over the same time-scale, as a result of decreasing radiogenic Pb being released from catchment weathering. Our results are consistent with: (1) the published interpretation of Pb isotopic variation in ferromanganese ocean crusts as a reflection of continental-scale glacial-interglacial chemical weathering cycles, (2) bench-scale whole-rock weathering experiments, and (3) soil chronosequence Pb isotope dissolution experiments and bridge the gap between short-term, mineral-scale experiments and long-term, ocean sediment records. We establish a time-scale for depletion of accessory minerals, and loss of their Pb isotopic signature at one catchment, and document the concurrent shift to slower primary mineral-controlled chemical weathering after deglaciation.

  13. Disruption of tephra fall deposits caused by lava flows during basaltic eruptions

    Science.gov (United States)

    Brown, R. J.; Thordarson, T.; Self, S.; Blake, S.

    2015-10-01

    Observations in the USA, Iceland and Tenerife, Canary Islands reveal how processes occurring during basaltic eruptions can result in complex physical and stratigraphic relationships between lava and proximal tephra fall deposits around vents. Observations illustrate how basaltic lavas can disrupt, dissect (spatially and temporally) and alter sheet-form fall deposits. Complexity arises through synchronous and alternating effusive and explosive activity that results in intercalated lavas and tephra deposits. Tephra deposits can become disrupted into mounds and ridges by lateral and vertical displacement caused by movement (including inflation) of underlying pāhoehoe lavas and clastogenic lavas. Mounds of tephra can be rafted away over distances of 100 s to 1,000 s m from proximal pyroclastic constructs on top of lava flows. Draping of irregular topography by fall deposits and subsequent partial burial of topographic depressions by later lavas can result in apparent complexity of tephra layers. These processes, deduced from field relationships, have resulted in considerable stratigraphic complexity in the studied proximal regions where fallout was synchronous or alternated with inflation of subjacent lava sheets. These mechanisms may lead to diachronous contact relationships between fall deposits and lava flows. Such complexities may remain cryptic due to textural and geochemical quasi-homogeneity within sequences of interbedded basaltic fall deposits and lavas. The net effect of these processes may be to reduce the usefulness of data collected from proximal fall deposits for reconstructing basaltic eruption dynamics.

  14. A high-resolution record of Holocene millennial-scale oscillations of surface water, foraminiferal paleoecology and sediment redox chemistry in the SE Brazilian margin

    Science.gov (United States)

    Dias, B. B.; Barbosa, C. F.; Albuquerque, A. L.; Piotrowski, A. M.

    2014-12-01

    Holocene millennial-scale oscillations and Bond Events (Bond et al. 1997) are well reported in the North Atlantic as consequence of fresh water input and weaking of the Atlantic Meridional Overturning Circulation (AMOC). It has been hypothesized that the effect of weaking of AMOC would lead to warming in the South Atlantic due to "heat piracy", causing surface waters to warm and a reorganization of surface circulation. There are few reconstructions of AMOC strength in the South Atlantic, and none with a high resolution Holocene record of changes of productivity and the biological pump. We reconstruct past changes in the surface water mass hydrography, productivity, and sediment redox changes in high-resolution in the core KCF10-01B, located 128 mbsl water depth off Cabo Frio, Brazil, a location where upwelling is strongly linked to surface ocean hydrography. We use Benthic Foraminiferal Accumulation Rate (BFAR) to reconstruct productivity, which reveals a 1.3kyr cyclicity during the mid- and late-Holocene. The geochemistry of trace and rare earth elements on foraminiferal Fe-Mn oxide coatings show changes in redox-sensitive elements indicating that during periods of high productivity there were more reducing conditions in sediment porewaters, producing a Ce anomaly and reduction and re-precipitation of Mn oxides. Bond events 1-7 were identified by a productivity increase along with reducing sediment conditions which was likely caused by Brazil Current displacement offshore allowing upwelling of the nutritive bottom water South Atlantic Central Waters (SACW) to the euphotic zone and a stronger local biological pump. In a global context, correlation with other records show that this occurred during weakened AMOC and southward displacement of the ITCZ. We conclude that Bond climatic events and millennial-scale variability of AMOC caused sea surface hydrographic changes off the Brazilian Margin leading to biological and geochemical changes recorded in coastal records

  15. Caesium and Plutonium Isotopes as Tracers of Various Events in Sediment Records in the Bay of Toulon (Northwestern Mediterranean Sea)

    Energy Technology Data Exchange (ETDEWEB)

    Duffa, C.; Arnaud, M.; Charmasson, S.; Thebault, H. [Institut de Radioprotection et de Surete Nucleaire, DEI/SESURE/LERCM, La Seyne sur Mer (France)

    2013-07-15

    Located along the French Mediterranean coast, the Toulon bay has a specific configuration with two basins. The shallow one is a semi-enclosed basin (Petite Rade) with complex hydrodynamic conditions that contribute to fine sedimentation. The open sea basin, separated from the first one by a long sea wall, receives different anthropogenic inputs. Surface and core sediment sampling cruises took place in 2001 and 2008, in order to study radionuclide spatial dispersion and sediment accumulation. {sup 137}Cs values are statistically higher in the 'Petite Rade' than in the open basin. {sup 239+240}Pu levels range from 0.7 to 2.6 Bq/kg dry weight in surface sediments, up to 6 times higher than elsewhere in Mediterranean coastal areas not influenced by riverine inputs. Plutonium activity ratios ({sup 238}Pu/{sup 239+240}Pu and {sup 239}Pu/{sup 240}Pu) labelled atmospheric nuclear weapon testing. Regarding the long cores, the highest plutonium activities, measured by alpha counting and ICP-MS, concern the first ten centimetres with a maximum value of 3.5 Bq/kg dry weight in {sup 239+240}Pu. (author)

  16. Rock magnetic records of the sediments of the eastern Arabian Sea: Evidence for the late Quaternary climatic change

    Digital Repository Service at National Institute of Oceanography (India)

    AnilKumar, K.; Rao, V.P; Patil, S.K.; Kessarkar, P; Thamban, M.

    water core off Kochi further suggests that the intense SW monsoon conditions prevailed until about 5 ka. The late Holocene organic-rich sediments of the SW margin of India were, however, subjected to early diagenesis at different intervals in the cores...

  17. Records of Lead and Other Heavy Metal Inputs to Sediments of the Ala Wai Canal, Oahu, HI

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Four cores are given: G8, G8B, M21, and M3. For each core, a printable table file (.PRN) and a spreadsheet (.WK3) are provided. The file names reflect the sediment...

  18. Discontinuous Late Pleistocene-Holocene pollen records from Auckland Domain, northern New Zealand

    International Nuclear Information System (INIS)

    Horrocks, M.; O'Loan, A.; Wallace, R.

    2009-01-01

    Two sediment sequences from Pukekawa crater, Auckland Domain, contain silty clay underlain by fibrous peat. The peat contains a pollen flora and wood indicating the presence of a warm-temperate, conifer-hardwood forest with Metrosideros, Agathis, Prumnopitystaxifolia, P. ferruginea, and especially Dacrydium. Radiocarbon dates indicate that the peat was deposited before the Last Glacial Maximum (LGM). Absence of tephras and small amounts of Fuscospora pollen indicate probable non-preservation of the LGM. The pollen flora of most of the clay contains Metrosideros, Ascarina, and ferns, indicating post-LGM warmer, wetter conditions. The two uppermost samples contain exotic pollen, indicating that they are post-European in origin. Excavation and levelling to form sports fields and parkland appears to have curtailed and mixed the Holocene record. (author). 24 refs., 4 figs., 1 tab.

  19. Lead isotope ratios in six lake sediment cores from Japan Archipelago: Historical record of trans-boundary pollution sources.

    Science.gov (United States)

    Hosono, Takahiro; Alvarez, Kelly; Kuwae, Michinobu

    2016-07-15

    Sediment cores from six lakes situated from north to south on the Japanese Archipelago were collected during 2009-2010 to investigate the hypothesis that deposition of lead (Pb) was coming from East Asia (including China, South Korea and eastern part of Russia). Accumulation rates and ages of the lake sediment were estimated by the (210)Pb constant rate of supply model and (137)Cs inputs to reconstruct the historical trends of Pb accumulation. Cores from four lakes located in the north and central Japan, showed clear evidence of Pb pollution with a change in the (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios in the recent sediment as compared to the deeper sediment. Among the six studied lakes, significant inputs of anthropogenic lead emissions were observed at Lake Mikazuki (north Hokkaido in north Japan), Lake Chokai (north of Honshu), and Lake Mikuriga (central part of Honshu). Pb isotopic comparison of collected core sediment and previously reported data for wet precipitation and aerosols from different Asian regions indicate that, before 1900, Pb accumulated in these three lakes was not affected by trans-boundary sources. Lake Mikazuki started to receive Pb emissions from Russia in early 1900s, and during the last two decades, this lake has been affected by trans-boundary Pb pollution from northern China. Lake Chokai has received Pb pollutant from northern China since early 1900s until 2009, whereas for the Lake Mikuriga the major Pb contaminant was transported from southern China during the past 100years. The results of our study demonstrate that Japan Archipelago has received trans-boundary Pb emissions from different parts of East Asian region depending on location, and the major source region has changed historically. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Temporal limits to the archaeological record in arid western NSW, Australia : lessons from OSL and radiocarbon dating of hearths and sediments

    International Nuclear Information System (INIS)

    Fanning, P.; Holdaway, S.

    2001-01-01

    The Western NSW Archaeology Program (WNSWAP) has been investigating surface scatters of Aboriginal stone artefacts and associated heat-retainer hearths in arid northwestern NSW, Australia, since 1995. The research combines new methods for documenting and analysing stone artefact scatters with an understanding of geomorphic landscape dynamics to seek insights into spatial and temporal patterns of Aboriginal occupation of the arid margin of Australia during the Late Holocene. The temporal dimension is dealt with in two ways: by radiocarbon determinations on charcoal from the remains of heat-retainer hearths associated with the artefact scatters, and by using optically simulated luminescence (OSL) and radiocarbon determinations from valley fill sediments to develop a chronology of landscape evolution of the valleys in which the artefacts and hearths are found. The heat-retainer hearths produced a record of just less than 2000 years of activity within the valley of Stud Creek, a 30 square km catchment in Sturt National Park. However, the record is discontinuous, with a gap in heat-retainer hearth construction of 200-400 years occurring between about 800 and 1100 y BP. Examination of patterns of erosion and deposition at the places where the hearths were found, and Bayesian statistical analysis of the radiocarbon determinations, demonstrates that this gap is real and not an artefact of the survey protocol. A discontinuous record is also evident when the sediments that comprise the valley fill upon which the hearths and stone artefact scatters are currently lying are examined. Five major sedimentary units can be identified, providing a record of depositional episodes ranging from modern or post-European back to the Late Pleistocene (about 70,000 years). But, in contrast to the record from the remains of the heat-retainer hearths, erosion is the major determinant of the temporal pattern of landscape change that can be reconstructed from this record. Gaps of up to 10

  1. Storm-related sedimentation influenced by coastal configuration in the stratigraphic record of a tectonically active shelf (Upper Pleistocene Le Castella terrace, Italy)

    Science.gov (United States)

    Nalin, Ronald; Massari, Francesco

    2018-03-01

    Analysis of patterns of coastal circulation and sediment dispersal is an essential step for the study of controlling factors influencing the long-term dynamics of coastal systems. Modern settings offer the possibility to monitor relevant parameters over relatively short time spans. However, geological examples complement this perspective by providing a time-averaged record where longer trends and stratigraphically significant processes can be evaluated. This study investigates the shallow marine deposits of Le Castella terrace (Upper Pleistocene, southern Italy) to document how patterns of circulation influenced by coastline configuration can affect the preserved millennial-scale depositional record of a progradational shoreline system. The regressive portion of the Le Castella terrace deposits, developed during a relative sea-level highstand and falling stage, consists of a progradational wedge mainly composed of redistributed skeletal particles of a coeval shallow water carbonate factory. Preservation of the morphology of the paleocoastline and abundant current-related sedimentary structures allow reconstruction of the predominant sediment dispersal dynamics responsible for the formation of this sedimentary wedge. Facies and paleocurrent analysis indicate offshore and alongshore sediment transport modes, consistent with coastal circulation driven by storms normally incident to the shoreline and a sharp change in coastline orientation. This coastal inflection influenced circulation patterns causing flow separation and eddy formation in the lee of the curved coastline. Syndepositional tectonic deformation also affected the architecture of the preserved deposits, controlling the nucleation and development of a clinostratified body and determining localized lateral stratigraphic variability. This study illustrates how transient but recurrent circulation patterns associated with changes in coastal orientation and related to high-energy storm events can leave a

  2. Astronomical calibration of the first Toba super-eruption from deep-sea sediments

    Science.gov (United States)

    Lee, M.; Chen, C.; Wei, K.; Iizuka, Y.

    2003-04-01

    Correlations between tephra layers interbedded within deep-sea cores and radiometrically dated volcanic eruptions provide an independent means of verifying dating techniques developed for sediment cores. Alternatively, the chronostratigraphic framework developed from marine sediments can be used to calibrate ages of land-base eruptions, if geochemical correlations can be established. In this study, we examined three deep-sea cores along an east-west transection across the South China Sea, with a distance of ~1800 to 2500 km away from the Toba caldera. The occurrence of the Oldest Toba Tuff was recognized on the basis of its geochemical characteristics, such as a high-silicate, high-potassium content and a distinct strontium isotope composition. The correlative tephra layer occurs slightly above the Australasian microtektite layer and below the Brunhes/Matuyama boundary, which in constitute three time-parallel markers for correlation and dating of Quaternary stratigraphic records. Against the astronomically tuned oxygen isotope chronostratigraphy, the rhyolitic ignimbrite erupted during the transition from marine isotope stage 20 (glacial) to stage 19 (interglacial) with an estimated age of 788 ka. The refined age is in good agreement with the radiometric age of 800+20 ka for Layer D of ODP Site 758 (Hall and Farrell, 1995), but significantly younger than the commonly referred age of 840+30 ka (Diehl et al., 1987). The mid-Pleistocene eruption expelled at least 800-1000 km3 dense-rock-equivalent of rhyolitic magma taking into account the widespread ashfall deposits in the Indian Ocean and the South China Sea basins. In spite of its exceptional magnitude, the timing of the first Toba super-eruption disputes a possible causal linkage between a major volcanic eruption and a long-term global climatic deterioration.

  3. Electron microprobe analyses of glasses from Kīlauea tephra units, Kīlauea Volcano, Hawaii

    Science.gov (United States)

    Helz, Rosalind L.; Clague, David A.; Mastin, Larry G.; Rose, Timothy R.

    2014-01-01

    This report presents approximately 2,100 glass analyses from three tephra units of Kīlauea Volcano: the Keanakākoʻi Tephra, the Kulanaokuaiki Tephra, and the Pāhala Ash. It also includes some new analyses obtained as part of a re-evaluation of the MgO contents of glasses in two of the three original datasets; this re-evaluation was conducted to improve the consistency of glass MgO contents among the three datasets. The glass data are a principal focus of Helz and others (in press), which will appear in the AGU Monograph Hawaiian Volcanoes—From Source to Surface. The report is intended to support this publication, in addition to making the data available to the scientific community.

  4. Buckets of ash track tephra flux from Halema'uma'u Crater, Hawai'i

    Science.gov (United States)

    Swanson, Don; Wooten, Kelly M.; Orr, Tim R.

    2009-01-01

    The 2008–2009 eruption at Kīlauea Volcano's summit made news because of its eight small discrete explosive eruptions and noxious volcanic smog (vog) created from outgassing sulfur dioxide. Less appreciated is the ongoing, weak, but continuous output of tephra, primarily ash, from the new open vent in Halema'uma'u Crater. This tephra holds clues to processes causing the eruption and forming the new crater-in-a-crater, and its flux is important to hazard evaluations.The setting of the vent–easily accessible from the Hawaiian Volcano Observatory (HVO)—is unusually favorable for neardaily tracking of tephra mass flux during this small prolonged basaltic eruption. Recognizing this, scientists from HVO are collecting ash and documenting how ejection masses, components, and chemical compositions vary through time.

  5. Information from uranium and thorium isotopes recorded in lake bottom sediment - Lake Kawaguchi. Attempt to evaluate environmental changes

    International Nuclear Information System (INIS)

    Sakaguchi, A.; Yamamoto, M.; Shimizu, T.; Sasaki, K.; Koshimizu, S.

    2003-01-01

    Lake sediments, as well as ice cores and marine sediments, have been used to reveal past environmental changes caused by both natural and artificial events with local and global scales. Particles in the lake originate from soil and other suspended matter which are carried in from the inflowing water or from direct discharge (lithogenous particles), and they are also formed in the lake as a result of the growth, metabolism and death of plants and animals (autogenous particles). The settling particles contain U and Th isotopes due to lithogenous particles (soil), and adsorbed U to the particles. Thorium has an exceedingly low solubility in water and is very strongly adsorbed onto particles. If we can distinguish these two different components in the mixture of U due to lithogenous particles themselves and adsorption fractions, the former might provide useful information on past environmental changes by natural events, while the latter information on past environmental changes by artificial events. In this paper, we aimed to test the above hypothesis using data on U and Th isotopes of sediment cores (0- ca. 40 cm depth, covering periods of past several hundred years) from 3 points in Lake Kawaguchi of Fuji-Goko in Japan. By using model equation and results obtained from analysis, we distinguished U due to lithogenous and autogenous particles. And these depth profiles were compared with changes in the rainfall during the period of 1933 - 2001. Although the changes in the 238 U/ 232 Th ratios with depth for lithogenous particles and rainfall do not fluctuate synchronously, some parts of depth coincided with each other. The results suggest strongly that variation in the U and Th isotopic ratios separated by model might be helpful in tracing the past environmental changes in regional scale. To check the usefulness of this method, physical and chemical data such as grain size, grain density, water content and biogenic SiO 2 in the sediment will be further compared with the

  6. Continuous Lake-Sediment Records of Glaciation in the Sierra Nevada between 52,600 and 12,500 14C yr B.P

    Science.gov (United States)

    Benson, Larry V.; May, Howard M.; Antweiler, Ronald C.; Brinton, Terry I.; Kashgarian, Michaele; Smoot, Joseph P.; Lund, Steve P.

    1998-09-01

    The chemistry of the carbonate-free clay-size fraction of Owens Lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial-interstadial oscillations. Owens Lake records of total organic carbon, magnetic susceptibility, and chemical composition of the carbonate-free, clay-size fraction indicate that Tioga glaciation began ˜24,500 and ended by ˜13,600 14C yr B.P. Many of the components of glacial rock flour (e.g., TiO 2, MnO, BaO) found in Owens Lake sediments achieved maximum values during the Tioga glaciation when valley glaciers reached their greatest extent. Total organic carbon and SiO 2(amorphous) concentrations reached minimum values during Tioga glaciation, resulting from decreases in productivity that accompanied the introduction of rock flour into the surface waters of Owens Lake. At least 20 stadial-interstadial oscillations occurred in the Sierra Nevada between 52,600 and 14,000 14C yr B.P. Total organic carbon data from a Pyramid Lake sediment core also indicate oscillations in glacier activity between >39,500 and ˜13,600 14C yr B.P. Alpine glacier oscillations occurred on a frequency of ≤1900 yr in both basins, suggesting that millennial-scale oscillations occurred in California and Nevada during most of the past 52,600 yr.

  7. Long-term Records of Trace Metal Elements in Core Sediments: Anthropogenic Impacts in The Eure River Watershed

    Science.gov (United States)

    Gardes, T.; Debret, M.; Copard, Y.; Patault, E.; Deloffre, J.; Marcotte, S.; Develle, A. L.; Sabatier, P.; Chaumillon, E.; Coulombier, T.; Revillon, S.; Nizou, J.; Laberdesque, Y.; Koltalo, F.

    2017-12-01

    The Martot Dam is located in the Eure River Watershed (Normandy, France), few hundred meters upstream the Eure-Seine Rivers confluence. In the context of the European Water Framework Directive (2000/60/EC), the French Authorities planned to remove this dam in 2017. Nevertheless, impacts of the removal remain poorly studied. Classically, dam blocked sedimentary transfers downstream, but here, sediments are not blocked behind the dam but stored three hundred meters upstream in a hydraulic annex, called the Martot Pond. Furthermore, this pond is submitted to the tidal flow from the Seine Estuary despite the Martot Dam. The aim of the study is to evaluate the dam removal impacts on sedimentary transfers and re-suspension of contaminated sediments stored in the Martot Pond and the Eure River's channel. Concerning past transfers and sediments accumulation in the Eure River Watershed, sedimentary archives have been cored, before dam removal, at the Martot Pond and the Les Damps Pond (located 10km upstream the latter). Dating of sedimentary cores for both ponds indicates a sedimentation rate around 1 cm y-1. Trace metal elements quantification showed a wide metallic contamination with highest concentrations evidenced during the 1950-1960's (As: 13-22 mg kg-1; Cd: 40-55 mg kg-1; Cr: 170-210 mg kg-1; Cu: 400-490 mg kg-1; Hg: 2.3 mg kg-1; Mn: 1,280-2,200 mg kg-1; Ni: 64-75 mg kg-1; Zn: 905-990 mg kg-1) and the 1990-2000's (Cr: 95-215 mg kg-1; Ni: 100 mg kg-1; Pb: 670-855 mg kg-1). These variations of concentrations along cores can be associated with industrial past of the Eure River Watershed and sources of contamination can be identified. Thereby, Zn, Ni or Hg contamination could be associated with wastes of battery factory released in the Eure River during the economic recovery, while Pb contamination is linked to the activities of a cathode-ray tubes factory. Metals quantification in core materials highlighted anthropogenic impacts in the Eure River Watershed. These

  8. First identification and characterization of Borrobol-type tephra in the Greenland ice cores

    DEFF Research Database (Denmark)

    Cook, Eliza; Davies, Siwan M.; Guðmundsdóttir, Esther R.

    2018-01-01

    in the ice-cores or that it relates to just one of the ice-core events. A firm correlation cannot be established at present due to their strong geochemical similarities. The older tephra horizon, found within all three ice-cores and dated to 17326 ± 319 a b2k, can be correlated to a known layer within marine....... The older deposit is consistent with BT age estimates derived from Scottish sites, while the younger deposit overlaps with both BT and PT age estimates. We suggest that either the BT in Northern European terrestrial sequences represents an amalgamation of tephra from both of the GI-1e events identified...

  9. Sediment record of polycyclic aromatic hydrocarbons in the Liaohe River Delta wetland, Northeast China: Implications for regional population migration and economic development.

    Science.gov (United States)

    Ma, Chuanliang; Lin, Tian; Ye, Siyuan; Ding, Xigui; Li, Yuanyuan; Guo, Zhigang

    2017-03-01

    The polycyclic aromatic hydrocarbons (PAHs) of a 210 Pb-dated sediment core extracted from the Liaohe River Delta wetland were measured to reconstruct the sediment record of PAHs and its response to human activity for the past 300 years in Northeast China. The concentrations of the 16 U.S. Environmental Protection Agency priority PAHs (∑16PAHs) ranged from 46 to 1167 ng g -1 in this sediment core. The concentrations of the 16 PAHs (especially 4- and 5+6-ring PAHs) after the 1980s (surface sediments 0-6 cm) were one or two orders of magnitudes higher than those of the down-core samples. The exponential growth of 4-ring and 5+6-ring PAH concentrations after the 1980s responded well to the increased energy consumption and number of civil vehicles resulting from the rapid economic development in China. Prior to 1950, relatively low levels of the 16 PAHs and a high proportion of 2+3-ring PAHs was indicative of biomass burning as the main source of the PAHs. A significant increase in the 2 + 3 ring PAH concentration from the 1860s-1920s was observed and could be attributed to a constant influx of population migration into Northeast China. It was suggested that the link between historical trend of PAHs and population or energy use involves two different economic stages. Typically, in an agricultural economy, the greater the population size, the greater the emission of PAHs from biomass burning, while in an industrial economy, the increase in sedimentary PAH concentrations is closely related to increasing energy consumption of fossil fuels. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Holocene Record of Major and Trace Components in the Sediments of an Urban Impoundment on the Mississippi River: Lake Pepin, Minnesota and Wisconsin

    Science.gov (United States)

    Dean, Walter E.

    2009-01-01

    Lake Pepin is a natural impoundment formed by damming of the Mississippi River about 9,180 radiocarbon years ago (19,600 calendar years) by an alluvial fan deposited by the Chippewa River, a tributary of the Mississippi in Wisconsin. Unique among 26 Mississippi River impoundments, Lake Pepin has stratigraphically preserved Holocene materials, including pollutants, that have been transported down the Mississippi. This natural Holocene record can then be compared to changes that have occurred since European settlement (ca. AD 1830), and since enactment of clean air and water legislation. The most immediate response to settlement in the sediments of Lake Pepin was an increase in bulk-sediment accumulation rate. This was accompanied by gradual increases in concentrations of phosphorus (P), and organic carbon (OC), followed by dramatic increases in these elements beginning about 1940. The increase in P was far greater than any of the minor fluctuations in P that occurred throughout the Holocene, but the increase in OC was comparable to an increase in OC that occurred in the mid-Holocene. The concentrations of several metals (for example, cadmium [Cd], and lead [Pb]) also are elevated in recent sediments. Increased Cd concentrations lasted only about two decades during the industrial era between World War II and the enactment of clean water standards in the 1970s. Increased Pb emissions, on the other hand, occurred over more than 100 years, first from burning of coal and smelting of lead ores, and then, beginning in the 1930s, burning of leaded gasoline. Concentrations of Pb in the sediments of Lake Pepin decreased to about two times preindustrial levels within a decade of enactment of unleaded gasoline restrictions.

  11. High resolution analysis of northern Patagonia lake sediments

    Science.gov (United States)

    Jarvis, S. W.; Croudace, I. W.; Langdon, P. G.; Rindby, A.

    2009-04-01

    activity in the catchment. Variation of elemental composition of these ‘glacial' layers is also clear from the Itrax data. It therefore appears that there have been significant reglaciation events in the catchment since the last glacial maximum. Many cores contain tephra layers, identified both visually and from the Itrax scans. Some of these have been confirmed as volcanic ash from the 1991 eruption of Mt Hudson, which at 45°54'S, 72°58'W is the southern-most volcano in the Chilean Andes and only 140km from the study area. Further work is underway to confirm and identify the source and age of other suspected tephra layers. Sediment accumulation rates in the upper parts of the cores are of the order of 1mm/yr (as determined by lead-210, caesium-137 dating and the 1991 Hudson tephra). Given XRF scan resolutions of up to 200μm there is thus the potential for investigation of sub-annual variability. Funding has been obtained to determine carbon-14 dates for the lower parts of the longer cores. The reproducibility and accuracy of the Itrax data has been validated using conventional WD-XRF spectrometry and the work presented will also include geochemical interpretation of the XRF data and comparison with recorded and proxy-inferred climate data for the region.

  12. Seasonality of the late Pleistocene Dawson tephra and exceptional preservation of a buried riparian surface in central Yukon Territory, Canada

    Science.gov (United States)

    Froese, Duane G.; Zazula, Grant D.; Reyes, Alberto V.

    2006-07-01

    The late Pleistocene Dawson tephra was deposited by one of the largest Quaternary eruptions in northwestern North America. Its distribution is known sparsely from sites near the source area in southwestern Alaska and central Yukon Territory, where more than 20 occurrences are documented in the Klondike region. Dawson tephra erupted about 25,300C yr BP, near the onset of the last glaciation, and provides a stratigraphic marker across Eastern Beringia. We report radiocarbon ages, paleobotanical data, and cryostratigraphic observations from a new Dawson tephra locale at Goldbottom Creek, in the Klondike region of Yukon Territory, which collectively indicate that the eruption occurred in the late winter or early spring. Multiple, fining-upward tephra-rich ice beds are interpreted as remnants of surface icings, which presently are common in the region during spring. A buried in situ riparian meadow, preserved below the icing and tephra, consists of abundant tufted hair grass ( Deschampsia caespitosa), with interspersed horsetails ( Equisetum cf. palustre) and mosses. Detrital plant remains and preserved in situ grass inflorescences entombed in the icing had expelled their fruits, consistent with a late season surface when the icing was active. The extraordinary thickness of Dawson tephra in central Yukon likely reflects reworking of a winter-deposited tephra by snow melt in the spring following the eruption, indicating that the primary thickness may be overestimated at valley-bottom sites. Winter deposition of the tephra may have, in part, minimized the terrestrial ecological impacts of the eruption on zonal "steppe-tundra" vegetation through the retransportation of tephra from hillslopes to the riparian areas, where the tephra became incorporated into local fluvial systems.

  13. Mass Flux of Tephra Sampled Frequently During the Ongoing Halema`uma`u Eruption (Invited)

    Science.gov (United States)

    Swanson, D.; Wooten, K.; Orr, T. R.

    2009-12-01

    The ongoing summit eruption of Kilauea provides an unparalleled opportunity to track, almost daily, the production of tephra. The eruption began on 19 March 2008, and tephra has been erupted every day since then to the end of August 2009. Most of the time, tephra is ejected quasi-continuously from the vent accompanied by a light gray to white gas plume, occasionally broken by a more vigorous pulse (“brown plume”) richer in ejecta. In early April 2008, an array of 10 plastic buckets was placed within 400 m of the new vent in Halema`uma`u down the prevailing NE wind direction. The configuration of the array, spanning an area of about 73,000 m2, has not changed since then. Buckets are emptied frequently, initially every day and, since summer 2008, on all weekdays. The contents are dried and weighed, and an “average network accumulation rate” is calculated in g/m2/hour. In addition, componentry analyses are made of the >0.5-mm size fraction from a bucket near the vent, in order to categorize the tephra into juvenile and lithic fractions. To estimate the total mass of tephra ejected from the vent for a given collection, we first drew isomass contours for several daily collections and plotted isomass versus square root of area to obtain the total mass of the deposit. From this, we developed an empirical multiplication factor that allows us to estimate, within ~25 percent, the total ejected mass per day in kilograms from the total collected mass in grams. The tephra is a mix of vitric and lithic pyroclasts, mostly ash in size. The vitric clasts, interpreted as juvenile, include Pele’s hair and tears, hollow spherules, dumbbells, pumice, and bits of coarsely vesicular glass. All these clasts were probably produced by weak spattering at the top of the lava column, which has rarely been seen. Especially since fall 2008, some vitric clasts are partly coated with secondary minerals or rock dust. We interpret such clasts as recycled, first erupted during spattering

  14. Alterations in the organic carbon pool recorded in sediments of Guanabara Bay, Brazil, a fertilized tropical estuary

    International Nuclear Information System (INIS)

    Carreira, R.S.; Kalas, F.A.; Santos, E.S.; Lima, A.L.; Godoy, J.M.; Wagener, A.L.R.

    1999-01-01

    We designed a core project in Guanabara Bay aimed at studying the possible anthropogenic impact on early diagenesis of sedimentary organic matter deposited in this system over the last century. The basic approach has been to look for the molecular, elemental (C, N and P) and isotopic compositions of organic matter in order to obtain the necessary information. The present work presents data on C, P and isotopic composition of organic matter, as well as the results of polyaromatic hydrocarbons, sedimentation rates and humic acids so far obtained for cores collected at several stations in the bay

  15. Centennial-scale records of total organic carbon in sediment cores from the South Yellow Sea, China

    Science.gov (United States)

    Zhu, Qing; Lin, Jia; Hong, Yuehui; Yuan, Lirong; Liu, Jinzhong; Xu, Xiaoming; Wang, Jianghai

    2018-01-01

    Global carbon cycling is a significant factor that controls climate change. The centennial-scale variations in total organic carbon (TOC) contents and its sources in marginal sea sediments may reflect the influence of human activities on global climate change. In this study, two fine-grained sediment cores from the Yellow Sea Cold Water Mass of the South Yellow Sea were used to systematically determine TOC contents and stable carbon isotope ratios. These results were combined with previous data of black carbon and 210Pb dating from which we reconstructed the centennial-scale initial sequences of TOC, terrigenous TOC (TOCter) and marine autogenous TOC (TOCmar) after selecting suitable models to correct the measured TOC (TOCcor). These sequences showed that the TOCter decreased with time in the both cores while the TOCmar increased, particularly the rapid growth in core H43 since the late 1960s. According to the correlation between the Huanghe (Yellow) River discharge and the TOCcor, TOCter, or TOCmar, we found that the TOCter in the two cores mainly derived from the Huanghe River and was transported by it, and that higher Huanghe River discharge could strengthen the decomposition of TOCmar. The newly obtained initial TOC sequences provide important insights into the interaction between human activities and natural processes.

  16. Inputting history of heavy metals into the inland lake recorded in sediment profiles: Poyang Lake in China

    International Nuclear Information System (INIS)

    Yuan Guoli; Liu Chen; Chen Long; Yang Zhongfang

    2011-01-01

    The temporal and spatial distribution of heavy metals (Cd, Hg, Pb, As and Cr) in Poyang Lake, the largest freshwater lake (3050 km 2 ) in China, were studied based on the sedimentary profiles. For this purpose, eight sedimentary cores were selected which located at lake area, outfall of lake and the main branch rivers, respectively. High-resolution profiles with interval 2 cm were used for analyzing the concentration of metals, and the ages of them were determined by 210 Pb and 137 Cs isotopic dating. While studying the change of metals concentration with the age in profile, it is found that the concentration of them in sediments was influenced not only by the sources in history but also by the sediment types. Based on this detailed work, the inventory and burden of heavy metals per decade were estimated in lake area during the past 50 years. Significantly, rivers-contribution ratio per decade was estimated to distinguish each river's contribution of heavy metals into lake while river-flux in history and metals concentration in profiles were considered as calculating factors. So, our research provides a proof to well understand the sedimentary history and the inputting history of heavy metals from main rivers into an inland lake.

  17. A 60,000-year record of hydrologic variability in the Central Andes from the hydrogen isotopic composition of leaf waxes in Lake Titicaca sediments

    Science.gov (United States)

    Fornace, Kyrstin L.; Hughen, Konrad A.; Shanahan, Timothy M.; Fritz, Sherilyn C.; Baker, Paul A.; Sylva, Sean P.

    2014-12-01

    A record of the hydrogen isotopic composition of terrestrial leaf waxes (δDwax) in sediment cores from Lake Titicaca provides new insight into the precipitation history of the Central Andes and controls of South American Summer Monsoon (SASM) variability since the last glacial period. Comparison of the δDwax record with a 19-kyr δD record from the nearby Illimani ice core supports the interpretation that precipitation δD is the primary control on δDwax with a lesser but significant role for local evapotranspiration and other secondary influences on δDwax. The Titicaca δDwax record confirms overall wetter conditions in the Central Andes during the last glacial period relative to a drier Holocene. During the last deglaciation, abrupt δDwax shifts correspond to millennial-scale events observed in the high-latitude North Atlantic, with dry conditions corresponding to the Bølling-Allerød and early Holocene periods and wetter conditions during late glacial and Younger Dryas intervals. We observe a trend of increasing monsoonal precipitation from the early to the late Holocene, consistent with summer insolation forcing of the SASM, but similar hydrologic variability on precessional timescales is not apparent during the last glacial period. Overall, this study demonstrates the relative importance of high-latitude versus tropical forcing as a dominant control on glacial SASM precipitation variability.

  18. A geochemical record of the link between chemical weathering and the East Asian summer monsoon during the late Holocene preserved in lacustrine sediments from Poyang Lake, central China

    Science.gov (United States)

    Huang, Chao; Wei, Gangjian; Li, Wuxian; Liu, Ying

    2018-04-01

    This paper presents relatively high-resolution geochemical records spanning the past 4000 cal yr BP obtained from the lacustrine sediments of Poyang Lake in central China. The variations in the intensity of the East Asian summer monsoon (EASM) are traced using the K/Na, Ti/Na, Al/K, kaolinite/illite and clay/feldspar ratios, together with the chemical index of alteration (CIA), as indicators of chemical weathering. During the last 4000 years, the proxy records of chemical weathering from Poyang Lake exhibit an overall enhanced trend, consistent with regional hydrological changes in previous independent records. Further comparisons and analyses demonstrate that regional moisture variations in central China is inversely correlated with the EASM intensity, with weak EASM generating high precipitation in central China. Our data reveal three intervals of dramatically dry climatic conditions (i.e., ca. 4000-3200 cal yr BP, ca. 2800-2400 cal yr BP, and ca. 500-200 cal yr BP). A period of weak chemical weathering, related to cold and dry climatic conditions, occurred during the Little Ice Age (LIA), whereas more intense chemical weathering, reflecting warm and humid climatic conditions, was recorded during the Medieval Warm Period (MWP). Besides, an intensification of chemical weathering in Poyang Lake during the late Holocene agrees well with strong ENSO activity, suggesting that moisture variations in central China may be predominantly driven by ENSO variability.

  19. Obtaining isochrones from pollution signals in a fluvial sediment record: A case study in a uranium-polluted floodplain of the Ploučnice River, Czech Republic

    International Nuclear Information System (INIS)

    Matys Grygar, T.; Elznicová, J.; Bábek, O.; Hošek, M.; Engel, Z.; Kiss, T.

    2014-01-01

    Highlights: • Integrated approach to assess pollutant distribution in floodplain. • Natural background concentration is a function and not a value. • Concept of local enrichment factors based on local background functions. • Secondary pollution from transient fluvial deposits. - Abstract: Uranium mining and processing in the watershed of the Ploučnice River in the Czech Republic during a well-defined time interval (1969–1989) allowed for a study of pollutant fates in sediments of a meandering river that is otherwise in a nearly natural state. A considerable part of the primary pollution is present in hotspots in the floodplain 10–15 km downstream from the mining district. One of the hotspots was characterised using geoinformatic, geophysical and geochemical means. The floodplain geomorphology and architecture and river channel dynamics were studied to develop an understanding of the formation of the hotspot and evaluate further movement of pollutants in the river system. Local background functions (with Rb or Ti as a predictor) and local enrichment factors (LEFs) were obtained for Ba, Ni, Pb, U and Zn concentrations in unpolluted sediments from the deeper strata of the active floodplain, an abandoned floodplain and an ancient terrace. The most recent (2013) overbank fines in the study area are still considerably enriched in Ni, U and Zn (LEF 3, 6 and 8, respectively), and thus pollution by heavy metals several km downstream of the hotspots continuously increases even though the primary source of pollution was terminated more than 20 years ago. The onset of the primary pollution (the base of the polluted strata) is hence clearly identified in the distal floodplain sediments as persistent and a potentially isochronous pollution signal in the fluvial record, whereas a secondary pollution signal overwrites the expected “primary pollution climax” and “pollution improvement” signals. That inertia of the fluvial system can also be expected in other

  20. A palaeoenvironmental record of natural and human change from the Auckland Isthmus, New Zealand, during the Late Holocene

    International Nuclear Information System (INIS)

    Horrocks, M.; Deng, Y.; Nichol, S.L.; Shane, P.A.; Ogden, J.

    2002-01-01

    A multi-proxy analysis of a sediment core from Waiatarua, Auckland Isthmus, adds to an environmental history from the local wetland spanning the Late Glacial to modern times. Several distal tephra were recorded in the core: 8.5 ka Rotoma (reworked), 6.1 ka Tuhua (primary and reworked), most likely the 1.8 ka Taupo (the latter is previously unreported for the Auckland Isthmus), and one unidentified, possibly 665 yr BP Kaharoa. Pollen and diatom analyses of the core show that during the period c. 6000-c. 4800 yr BP, the site was a lake fringed with Cyperaceae/Leptospermum swamp. The lake became progressively shallower after c. 4800 yr BP, probably due to hydroseral infilling. Surrounding the lake was forest dominated by Dacrydium, Prumnopitys, Metrosideros, and Nestegis. Transition to the Polynesian era appears unclear because the site probably endured a hiatus due to destruction of peat by burning in European times. (author). 39 refs., 4 figs., 2 tabs

  1. Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries

    Energy Technology Data Exchange (ETDEWEB)

    Thevenon, Florian, E-mail: Florian.Thevenon@yahoo.fr [Institute F.-A. Forel, University of Geneva, Versoix (Switzerland); Graham, Neil D. [Institute F.-A. Forel, University of Geneva, Versoix (Switzerland); Chiaradia, Massimo [Department of Mineralogy, University of Geneva, Geneva (Switzerland); Arpagaus, Philippe; Wildi, Walter; Pote, John [Institute F.-A. Forel, University of Geneva, Versoix (Switzerland)

    2011-12-15

    This research first focuses on the spatial and temporal patterns of heavy metals from contrasting environments (highly polluted to deepwater sites) of Lake Geneva. The mercury (Hg) and lead (Pb) records from two deepwater sites show that the heavy metal variations before the industrial period are primarily linked to natural weathering input of trace elements. By opposition, the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century, involved the sedimentation of highly metal-contaminated sediments in the area surrounding the WWTP outlet pipe discharge. Eventually, a new Pb isotope record of sediments from Lake Lucerne identifies the long-term increasing anthropogenic lead pollution after ca. 1500, probably due to the development of metallurgical activities during the High Middle Ages. These data furthermore allows to compare the recent anthropogenic sources of water pollution from three of the largest freshwater lakes of Western Europe (lakes Geneva, Lucerne, and Constance). High increases in Pb and Hg highlight the regional impact of industrial pollution after ca. 1750-1850, and the decrease of metal pollution in the 1980s due to the effects of remediation strategies such as the implementation of wastewater treatment plants (WWTPs). However, at all the studied sites, the recent metal concentrations remain higher than pre-industrial levels. Moreover, the local scale pollution data reveal two highly contaminated sites (> 100 {mu}g Pb/g dry weight sediment) by industrial activities, during the late-19th and early-20th centuries (Lake Lucerne) and during the second part of the 20th century (Vidy Bay of Lake Geneva). Overall, the regional scale pollution history inferred from the three large and deep perialpine lakes points out at the pollution of water systems by heavy metals during the last two centuries due to the discharge of industrial effluents. Highlights: Black-Right-Pointing-Pointer Natural sources

  2. Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries

    International Nuclear Information System (INIS)

    Thevenon, Florian; Graham, Neil D.; Chiaradia, Massimo; Arpagaus, Philippe; Wildi, Walter; Poté, John

    2011-01-01

    This research first focuses on the spatial and temporal patterns of heavy metals from contrasting environments (highly polluted to deepwater sites) of Lake Geneva. The mercury (Hg) and lead (Pb) records from two deepwater sites show that the heavy metal variations before the industrial period are primarily linked to natural weathering input of trace elements. By opposition, the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century, involved the sedimentation of highly metal-contaminated sediments in the area surrounding the WWTP outlet pipe discharge. Eventually, a new Pb isotope record of sediments from Lake Lucerne identifies the long-term increasing anthropogenic lead pollution after ca. 1500, probably due to the development of metallurgical activities during the High Middle Ages. These data furthermore allows to compare the recent anthropogenic sources of water pollution from three of the largest freshwater lakes of Western Europe (lakes Geneva, Lucerne, and Constance). High increases in Pb and Hg highlight the regional impact of industrial pollution after ca. 1750–1850, and the decrease of metal pollution in the 1980s due to the effects of remediation strategies such as the implementation of wastewater treatment plants (WWTPs). However, at all the studied sites, the recent metal concentrations remain higher than pre-industrial levels. Moreover, the local scale pollution data reveal two highly contaminated sites (> 100 μg Pb/g dry weight sediment) by industrial activities, during the late-19th and early-20th centuries (Lake Lucerne) and during the second part of the 20th century (Vidy Bay of Lake Geneva). Overall, the regional scale pollution history inferred from the three large and deep perialpine lakes points out at the pollution of water systems by heavy metals during the last two centuries due to the discharge of industrial effluents. Highlights: ► Natural sources dominated trace element

  3. Historical shifts in oxygenation regime as recorded in the laminated sediments of lake Montcortès (Central Pyrenees) support hypoxia as a continental-scale phenomenon.

    Science.gov (United States)

    Vegas-Vilarrúbia, Teresa; Corella, Juan Pablo; Pérez-Zanón, Núria; Buchaca, Teresa; Trapote, M Carmen; López, Pilar; Sigró, Javier; Rull, Valentí

    2018-01-15

    Recent expansion of anoxia has become a global issue and there is potential for worsening under global warming. At the same time, obtaining proper long-term instrumental oxygen records is difficult, thus reducing the possibility of recording long-term changes in oxygen shifts that can be related with climate or human influence. Varved lake sediments provide the better time frame to study this phenomenon at high resolution. We tracked the oxic/anoxic shifts of the varved Lake Montcortès since 1500CE, and tried to recognise anthropogenic and climatic influences combining biological and geochemical proxies. Four main scenarios emerged: 1) years with abrupt sediment inputs (A); 2) years with outstanding mixing and oxygenation of the water column (B); 3) years with strong stratification, anoxia, intense sulfur bacterial activity and increased biomass production (C); 4) years with stratification and anoxia, but relatively less biomass production (D). In line with current limnologic trends, high supra-annual variability in the occurrence of oxygenation events was observed. Interestingly, at least 45.3% of the years were mixing years and, like the meromictic ones, were mostly clustered into groups of consecutive years, thus alternating years of monomixis with years of meromixis. Most years of D belong to the period 1500-1820CE, when human activities were the most intense. Most years of A belonged to the climatic unstable period of 1850-1899CE. Years of B were irregularly distributed but were best represented in the period 1820-1849CE. Most years of C belonged to the 20th century. More than 90% of the years with climatic instrumental records belonged to B and C. Current climate warming seems to be taking control over the oxygenation capacity of the lake, especially since the second half of the 20th century. Our results support recent findings related to hypoxia spreading at the global scale. Copyright © 2017. Published by Elsevier B.V.

  4. Thermoluminescence dating of a tephra deposit of the ''Toya'' volcano (Hokkaido, Japan)

    International Nuclear Information System (INIS)

    Sanzelle, S.; Pilleyre, Th.; Miallier, D.; Fain, J.; Ganzawa, Y.

    2000-01-01

    Toya caldera which has a diameter of about 10 km and a hexagonal form is situated in the southern part of Hokkaido, northern Japan. The water level of the caldera lake is 84 m and the highest altitude of the central dome in the lake, Nakajima is 454 m. The volcanic activity is divided into 4 stages of the Toya Pyroclastic Flow Deposits 1 to 4. This tephra is composed of rhyolitic ash which is rich in glass and associated with hornblende, pyroxene and quartz. In a previous work, the age of eruption was estimated by utilising several dating methods and the stratigraphical correlation with other tephra. The ages which resulted from FT (Fission Tracks) dating and TL (Thermoluminescence) dating indicated 130±30 ka and 103-134 ka, respectively. The overall estimated age, received from other information such as the environmental change of mineral marine deposits, has been accepted as 100-120 ka by Quaternary Researchers. Because this tephra can be found widely in the Quaternary field, many researchers can use it as an appropriate age indicator of the 5c or 5d Isotope Stage, the middle age of the Last Internal Glacial Age. A new dating program was initiated, using the red TL of quartz grains extracted from the tephra. The samples studied in the present work came from the southern part of the deposits, around 15 km away from the centre of the caldera. The TL measurements, using the red signal of xenolithic quartz grains from the tephra, were made at Aubiere. Three distinct sets of samples were measured. The first two differ from each other by grain size, 250-350 μm (TOYA2, Aset2) and 150-250 μm (TOYA1,Bset3), and were irradiated in Japan and the third one, 250-350 μm (TOYA2, Cset2) was irradiated at Aubiere. The annual dose rate experienced by the samples during burial was estimated from a compilation of radionuclide contents evaluated in Japan using NAA and in France, using low level gamma spectroscopy (Aubiere) and ICPMS (CRPG, Nancy). In situ water content (as dug

  5. Classifying the Sizes of Explosive Eruptions using Tephra Deposits: The Advantages of a Numerical Inversion Approach

    Science.gov (United States)

    Connor, C.; Connor, L.; White, J.

    2015-12-01

    Explosive volcanic eruptions are often classified by deposit mass and eruption column height. How well are these eruption parameters determined in older deposits, and how well can we reduce uncertainty using robust numerical and statistical methods? We describe an efficient and effective inversion and uncertainty quantification approach for estimating eruption parameters given a dataset of tephra deposit thickness and granulometry. The inversion and uncertainty quantification is implemented using the open-source PEST++ code. Inversion with PEST++ can be used with a variety of forward models and here is applied using Tephra2, a code that simulates advective and dispersive tephra transport and deposition. The Levenburg-Marquardt algorithm is combined with formal Tikhonov and subspace regularization to invert eruption parameters; a linear equation for conditional uncertainty propagation is used to estimate posterior parameter uncertainty. Both the inversion and uncertainty analysis support simultaneous analysis of the full eruption and wind-field parameterization. The combined inversion/uncertainty-quantification approach is applied to the 1992 eruption of Cerro Negro (Nicaragua), the 2011 Kirishima-Shinmoedake (Japan), and the 1913 Colima (Mexico) eruptions. These examples show that although eruption mass uncertainty is reduced by inversion against tephra isomass data, considerable uncertainty remains for many eruption and wind-field parameters, such as eruption column height. Supplementing the inversion dataset with tephra granulometry data is shown to further reduce the uncertainty of most eruption and wind-field parameters. We think the use of such robust models provides a better understanding of uncertainty in eruption parameters, and hence eruption classification, than is possible with more qualitative methods that are widely used.

  6. Probabilistic tephra hazard maps for the Neapolitan area: Quantitative volcanological study of Campi Flegrei eruptions

    Science.gov (United States)

    Mastrolorenzo, G.; Pappalardo, L.; Troise, C.; Panizza, A.; de Natale, G.

    2008-07-01

    Tephra fall is a relevant hazard of Campi Flegrei caldera (Southern Italy), due to the high vulnerability of Naples metropolitan area to such an event. Here, tephra derive from magmatic as well as phreatomagmatic activity. On the basis of both new and literature data on known, past eruptions (Volcanic Explosivity Index (VEI), grain size parameters, velocity at the vent, column heights and erupted mass), and factors controlling tephra dispersion (wind velocity and direction), 2D numerical simulations of fallout dispersion and deposition have been performed for a large number of case events. A bayesian inversion has been applied to retrieve the best values of critical parameters (e.g., vertical mass distribution, diffusion coefficients, velocity at the vent), not directly inferable by volcanological study. Simulations are run in parallel on multiple processors to allow a fully probabilistic analysis, on a very large catalogue preserving the statistical proprieties of past eruptive history. Using simulation results, hazard maps have been computed for different scenarios: upper limit scenario (worst-expected scenario), eruption-range scenario, and whole-eruption scenario. Results indicate that although high hazard characterizes the Campi Flegrei caldera, the territory to the east of the caldera center, including the whole district of Naples, is exposed to high hazard values due to the dominant westerly winds. Consistently with the stratigraphic evidence of nature of past eruptions, our numerical simulations reveal that even in the case of a subplinian eruption (VEI = 3), Naples is exposed to tephra fall thicknesses of some decimeters, thereby exceeding the critical limit for roof collapse. Because of the total number of people living in Campi Flegrei and the city of Naples (ca. two million of inhabitants), the tephra fallout risk related to a plinian eruption of Campi Flegrei largely matches or exceeds the risk related to a similar eruption at Vesuvius.

  7. Using Spectroscopy to Infer the Eruption Style and Volatile History of Volcanic Tephras

    Science.gov (United States)

    McBride, M. J.; Horgan, B. H. N.; Rowe, M. C.; Wall, K. T.; Oxley, B. M.

    2017-12-01

    The interaction between volatiles and magma strongly influences volcanic eruption styles, and results in an increase in the glass component of volcanic tephra. On Earth, both phreatomagmatic and magmatic explosive eruptions create glassy tephras. Phreatomagmatic eruptions form abundant glass by quickly quenching lava through interaction with meteoric water while magmatic eruptions create less glass through slower cooling within larger pyroclasts or eruption columns. Wall et al. (2014) used X-ray diffraction (XRD) of diverse tephra samples to show that glass content correlates with eruption style, as magmatic samples contain less glass than phreatomagmatic samples. While use of XRD is limited to Earth and the Curiosity rover on Mars, orbital spectroscopy is much a more common technique in the exploration of terrestrial bodies. In this study, we evaluate whether or not spectroscopy can be used to infer eruption style and thus volatile history. Visible/near-infrared (VNIR) and thermal-infrared (TIR) spectra were collected of the Wall et al. (2014) tephra samples, and were analyzed for trends related to glass content and thus eruption style. VNIR spectra can detect glass at high abundances as well as hydrothermal alteration minerals produced during interactions with meteoric water. Using TIR, glass abundances can be derived by deconvolving the spectra with a standard spectral library; however, due to the non-unique spectral shape of glass, intermediate to high glass abundances in tephras are difficult to differentiate using TIR alone. Synthetic mixtures of glass and crystalline minerals verify these results. Therefore, the most effective method for determining glass abundance and thus eruption style from volcanic deposits is a combination of VNIR and TIR spectral analysis. Using standard planetary remote sensing instrumentation to infer eruption styles will provide a new window into the volcanic and volatile histories of terrestrial bodies.

  8. A late glacial record of ice-sheet dynamics and melt supply recovered in the sediments of IODP Expedition 347 in the Baltic Sea

    Science.gov (United States)

    Passchier, Sandra; Jensen, Jørn Bo; Kenzler, Michael; Johnson, Sean; Andrén, Thomas; Barker Jørgensen, Bo

    2015-04-01

    Modern observations of increased surface ablation, meltwater routing to the bed, and increases in glacial speeds point to feedbacks between ice-sheet dynamics, melt supply, and subglacial discharge. Paleorecords have the potential to explore the decadal to centennial variability of these systems, but until recently such records were short and discontinuous in ice-proximal settings and underutilized for this specific purpose. The Integrated Ocean Drilling Program Expedition 347 in the Baltic Sea recovered annually laminated sediments that document the dynamics of the Scandinavian Ice Sheet. Hydraulic piston cores recovered from Sites M0060, M0063, M0064, and M0065 allow us to reconstruct a nearly complete record of ca. 6000 years in ice retreat history at annual to decadal resolution between ca. 17 and 11ka. The late glacial successions of these four IODP drillsites comprise of a till or proglacial fluvioglacial sediment overlain by variable thicknesses of well-laminated deglacial successions within several high-recovery holes. As the Scandinavian Ice Sheet retreated from the western Baltic Sea, and to the North, the ice-sheet's grounding line migrated across the four sites and deposited overlapping sections of high-resolution ice-proximal to ice-distal successions. Laser particle size results from Sites M0060 and M0063, and inspection of line-scan images, show shifts in sedimentary facies and lithologies that were not recognized during initial visual core description. For example, at Site M0060 in the Kattegat, ice-rafting fluxes in silty clays decrease upward and are negligible in the overlying varved succession. These characteristics are interpreted as ice retreat within a calving bay environment from ca. 17ka onward, followed by distal glacial marine deposition from sediment plumes governed by meltwater discharge. Moreover, at Site M0063 in the Baltic Sea, laser particle size distributions record an abrupt shift from interlaminated clayey silt to laminated clay

  9. Hydrothermal sediments as a potential record of seawater Nd isotope compositions: The Rainbow vent site (36°14'N, Mid-Atlantic Ridge)

    Science.gov (United States)

    Chavagnac, ValéRie; Palmer, Martin R.; Milton, J. Andrew; Green, Darryl R. H.; German, Christopher R.

    2006-09-01

    Geochemical compositions and Sr and Nd isotopes were measured in two cores collected ˜2 and 5 km from the Rainbow hydrothermal vent site on the Mid-Atlantic Ridge. Overall, the cores record enrichments in Fe and other metals from hydrothermal fallout, but sequential dissolution of the sediments allows discrimination between a leach phase (easily leachable) and a residue phase (refractory). The oxy-anion and transition metal distribution combined with rare earth element (REE) patterns suggest that (1) the leach fraction is a mixture of biogenic carbonate and hydrothermal Fe-Mn oxy-hydroxide with no significant contribution from detrital material and (2) >99.5% of the REE content of the leach fraction is of seawater origin. In addition, the leach fraction has an average 87Sr/86Sr ratio indistinguishable from modern seawater at 0.70916. Although we lack the ɛNd value of present-day deep water at the Rainbow vent site, we believe that the REE budget of the leach fraction is predominantly of seawater origin. We suggest therefore that the leach fraction provides a record of local seawater ɛNd values. Nd isotope data from these cores span the period of 4-14 ka (14C ages) and yield ɛNd values for North East Atlantic Deep Water (NEADW) that are higher (-9.3 to -11.1) than those observed in the nearby Madeira Abyssal Plain from the same depth (-12.4 ± 0.9). This observation suggests that either the Iceland-Scotland Overflow Water (ISOW) and Lower Deep Water contributions to the formation of NEADW are higher along the Mid-Atlantic Ridge than in the surrounding basins or that the relative proportion of ISOW was higher during this period than is observed today. This study indicates that hydrothermal sediments have the potential to provide a higher-resolution record of deep water ɛNd values, and hence deepwater circulation patterns in the oceans, than is possible from other types of sediments.

  10. Changes in the Indian summer monsoon intensity in Sri Lanka during the last 30 ky - A multiproxy record from a marine sediment core.

    Science.gov (United States)

    Ranasinghage, P. N.; Nanayakkara, N. U.; Kodithuwakku, S.; Siriwardana, S.; Luo, C.; Fenghua, Z.

    2016-12-01

    Indian monsoon plays a vital role in determining climate events happening in the Asian region. There is no sufficient work in Sri Lanka to fully understand how the summer monsoonal variability affected Sri Lanka during the quaternary. Sri Lanka is situated at an ideal location with a unique geography to isolate Indian summer monsoon record from iris counterpart, Indian winter monsoon. Therefore, this study was carried out to investigate its variability and understand the forcing factors. For this purpose a 1.82 m long gravity core, extracted from western continental shelf off Colombo, Sri Lanka by Shiyan 1 research vessel, was used. Particle size, chemical composition and colour reflectance were measured using laser particle size analyzer at 2 cm resolution, X-Ray Fluorescence spectrometer (XRF) at 2 cm resolution, and color spectrophotometer at 1 cm resolution respectively. Radio carbon dating of foraminifera tests by gas bench technique yielded the sediment age. Finally, principal component analysis (PCA) of XRF and color reflectance (DSR) data was performed to identify groups of correlating elements and mineralogical composition of sediments. Particle size results indicate that Increasing temperature and strengthening monsoonal rainfall after around 18000 yrs BP, at the end of last glacial period, enhanced chemical weathering over physical weathering. Proxies for terrestrial influx (XRF PC1, DSR PC1) and upwelling and nutrient supply driven marine productivity (XRF PC3 and DSR PC2) indicate that strengthening of summer monsoon started around 15000 yrs BP and maximized around 8000-10000 yrs BP after a short period of weakening during Younger Dryas (around 11000 yrs BP). The 8.2 cold event was recorded as a period of low terrestrial influx indicating weakening of rainfall. After that terrestrial input was low till around 2000 yrs BP indicating decrease in rainfall. However, marine productivity remained increasing throughout the Holocene indicating an increase in

  11. Decline of the Macquarie Marshes ecosystem, Australia, since European arrival recorded by organic geochemical proxies in sediments

    Science.gov (United States)

    Yu, L.; Chivas, A. R.; Garcia, A.; Hu, J.

    2011-12-01

    The Macquarie Marshes are floodplain wetlands in semi-arid NSW, Australia, and a Ramsar site experiencing accelerated deterioration in the last 50 years due to anthropogenic activities. We investigated environmental changes occurring in the northern and southern marshes using organic geochemical proxies from short cores and surface samples as modern analogues. Some proxies of modern plants (ferns, charophyte, reeds, Eucalyptus) and biota (black swan guano) samples, which are abundant in the Macquarie Marshes, were also analysed for comparison. The proxies analysed include bulk organic carbon and nitrogen (TOC, TN, C/N ratio), carbon and nitrogen isotopes (δ13C, δ15N) and some organic biomarkers (focusing on n-alkanes, sterols and polycylic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs)). TOC values in surface samples range between 2 to 5% depending on the organic input. The TOC and TN curves exhibit similar trends along time, decreasing to only one tenth at the depth of 70 cm (~ 565-752 years old) than those at the surface. The bulk δ13C values of modern samples (less than 50 years old) vary from -23% to -26%, falling within the range of values found in black swan guano(-21.6%) and plants (-27.0 to -31.5%). The calculated C/N ratios range from 10 to 25, and together with δ13C values suggest that the organic matter is mainly derived from terrestrial C3 plants. The contribution of aquatic plants is shown by shifts to higher δ13C values and lower C/N values in the core sections below the 40 cm depth (older than 130 years). Changes in vegetation type are also reflected by n-alkane and sterol biomarkers. In one core from the northern marshes, the temporal variation of (n-C27+C29)/n-C31 ratio indicates that the dominance of grasses has gradually been replaced by higher plants about 130 years ago. Sediments from the floodplain and dry lagoons show a dominant peak in long-chain n-alkanes with strong odd-to-even preference, contributed by emergent

  12. A 200 year sedimentary record of progressive eutrophication in lake Greifen (Switzerland): Implications for the origin of organic-carbon-rich sediments

    Science.gov (United States)

    Hollander, David J.; McKenzie, Judith A.; Lo Ten Haven, H.

    1992-09-01

    Over the past 200 years Lake Greifen, a small lake in northeastern Switzerland, has undergone dramatic changes in primary productivity and eutrophication due to increased nutrient supply from agricultural activity and industrialization. A 40 year historical record of the water-column chemistry indicates that productivity and eutrophication reached a maximum in 1974, after which stricter regulations on the input of nutrients resulted in a progressive decrease. Collected cores show the sedimentary expression of this anthropogenically induced eutrophication by a well-developed annual sedimentation and by enhanced values of total organic carbon, organic-carbon accumulation rates, and hydrogen indices (HI) of the kerogens. Analyses of the carbon isotopic composition of sedimentary carbonates and organic matter reveal that the fractionation between these two phases varies with the HI of kerogens. This observation is explicable in terms of changing productivity and preservation of the organic matter, and the CO2(aq) budget of the water body. We propose that if high primary productivity were primarily responsible for the preservation and accumulation of organic matter, then a negative correlation will occur between Δδ13Ccalcite-organic matter (Δδ13Ccal-om) and HI values. In an environment with relatively low to moderate productivity but with bottom-water anoxia, a positive correlation will exist between Δδ13Ccal-om and HI values. This study of Lake Greifen has implications for understanding paleoenvironmental controls on ancient organic-carbon-rich sediments.

  13. Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core.

    Science.gov (United States)

    Sculley, John B; Lowe, Rex L; Nittrouer, Charles A; Drexler, Tina M; Power, Mary E

    2017-09-19

    Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass of Cladophora surveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by "top-down" (consumer release) rather than "bottom-up" (growth promoting) controls.

  14. Over 100 years of environmental change recorded by foraminifers and sediments in a large Gulf of Mexico estuary, Mobile Bay, AL, USA

    Science.gov (United States)

    Osterman, Lisa E.; Smith, Christopher G.

    2012-01-01

    The marine microfauna of Mobile Bay has been profoundly influenced by the development and expansion of the primary shipping channel over the last ˜100 years. Foraminifers and sediments from seven box cores with excess lead-210 chronology document that channel dredging and spoil disposal have altered circulation, reduced estuarine mixing, changed sedimentation patterns, and caused a faunal turnover within the bay. Beginning in the late 1800s, changes in estuarine mixing allowed for greater low-pH freshwater influence in the bay, and ultimately began environmental changes that resulted in the loss of calcareous foraminifers. By the early 1900s, box cores throughout Mobile Bay record a ˜ 100-year trend of increasing calcareous test dissolution that continues to the present. Since the completion of the current shipping channel in the 1950s, restricted tidal flushing and increased terrestrial organic matter, documented by carbon-to-nitrogen ratios, stimulated an increase in agglutinated foraminiferal densities. However, in deeper areas of the bay, hypoxic water has negatively impacted the marine microfauna. Comparisons of the present-day foraminiferal assemblage with foraminifers collected in the early 1970s indicate that the continued biologic loss of calcareous foraminifers in the bay has allowed the introduction of a new agglutinated foraminiferal species into the bay.

  15. Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core

    Science.gov (United States)

    Sculley, John B.; Lowe, Rex L.; Nittrouer, Charles A.; Drexler, Tina M.; Power, Mary E.

    2017-01-01

    Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass of Cladophora surveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by “top-down” (consumer release) rather than “bottom-up” (growth promoting) controls. PMID:28874576

  16. High-resolution sub-bottom seismic and sediment core records from the Chukchi Abyssal Plain reveal Quaternary glaciation impacts on the western Arctic Ocean

    Science.gov (United States)

    Joe, Y. J.; Seokhoon, Y.; Nam, S. I.; Polyak, L.; Niessen, F.

    2017-12-01

    For regional context of the Quaternary history of Arctic marine glaciations, such as glacial events in northern North America and on the Siberian and Chukchi margins, we used CHIRP sub-bottom profiles (SBP) along with sediment cores, including a 14-m long piston core ARA06-04JPC taken from the Chukchi abyssal plain during the RV Araon expedition in 2015. Based on core correlation with earlier developed Arctic Ocean stratigraphies using distribution of various sedimentary proxies, core 04JPC is estimated to extend to at least Marine Isotope Stage 13 (>0.5 Ma). The stratigraphy developed for SBP lines from the Chukchi abyssal plain to surrounding slopes can be divided into four major seismostratigraphic units (SSU 1-4). SBP records from the abyssal plain show well preserved stratification, whereas on the surrounding slopes this pattern is disrupted by lens-shaped, acoustically transparent sedimentary bodies interpreted as glaciogenic debris flow deposits. Based on the integration of sediment physical property and SBP data, we conclude that these debris flows were generated during several ice-sheet grounding events on the Chukchi and East Siberian margins, including adjacent ridges and plateaus, during the middle to late Quaternary.

  17. Decade-centenary resolution records of climate changes in East Siberia from elements in the bottom sediments of lake Baikal for the last 150 kyr

    International Nuclear Information System (INIS)

    Goldberg, E.L.; Phedorin, M.A.; Chebykin, E.P.; Zolotarev, K.B; Zhuchenko, N.A.

    2007-01-01

    High-resolution scanning Synchrotron Radiation X-ray Fluorescence Analysis (SRXFA) was applied to investigate the downcore distribution of elements in the sediments from Lake Baikal (East Siberia). The obtained multi-element time series reveal the presence of abrupt climate shifts in East Siberia which were synchronous with the abrupt warming events in the North Atlantic and Greenland (Dansgaard-Oeschges events (D/O) during the last ice age 24-75 kyr BP. We show here the set of climatic indicators reveals all globally known climate changes from dry and cool or glacial climates to humid and warm ones, which were recorded in Northern Atlantic and East Siberia both on the orbital and millennial time scales during the last 150 kyr

  18. Glacial flour in lacustrine sediments: Records of alpine glaciation in the western U.S.A. during the last glacial interval

    Science.gov (United States)

    Rosenbaum, J. G.; Reynolds, R. L.

    2010-12-01

    Sediments in Bear Lake (UT/ID) and Upper Klamath Lake (OR) contain glacial flour derived during the last glacial interval from the Uinta Mountains and the southern Cascade Range, respectively. Magnetic properties provide measures of glacial-flour content and, in concert with elemental and grain-size analyses, yield high-resolution records of glacial growth and decay. Creation and preservation of such records requires that (1) properties of glacial flour contrast with those of other sedimentary components and (2) magnetic minerals are neither formed nor destroyed after deposition. In the Bear Lake watershed, glaciers were confined to a small headwater area of the Bear River underlain by hematite-rich rocks of the Uinta Mountain Group (UMG), which are not exposed elsewhere in the catchment. Because UMG detritus is abundant only in Bear Lake sediments of glacial age, hard isothermal remanent magnetization (a measure of hematite content) provides a proxy for glacial flour. In contrast, the entire Upper Klamath Lake catchment, which lies to the east of the Cascade Range in southern Oregon, is underlain largely by basalt and basaltic andesite. Magnetic properties of fresh titanomagnetite-rich rock flour from glaciers on a composite volcano contrast sharply with those of detritus from unglaciated areas in which weathering destroyed some of the titanomagnetite. Ideally, well-dated records of the flux of glacial flour can be compared to ages of glacial features (e.g., moraines). For Upper Klamath Lake, quantitative measures of rock-flour content (from magnetic properties) and excellent chronology allow accurate calculation of flux. However, ages of glacial features are lacking and mafic volcanic rocks, which weather rapidly in this environment, are not well suited for cosmogenic exposure dating. At Bear Lake, estimates of glacial-flour content are less quantitative and chronology within the glacial interval must be interpolated from radiocarbon ages above and below the

  19. Decade-centenary resolution records of climate changes in East Siberia from elements in the bottom sediments of lake Baikal for the last 150 kyr

    Energy Technology Data Exchange (ETDEWEB)

    Goldberg, E.L. [Limnological Institute of the SB RAS, 664033 Irkutsk (Russian Federation)]. E-mail: gold@econova.nsk.su; Phedorin, M.A. [Limnological Institute of the SB RAS, 664033 Irkutsk (Russian Federation); Chebykin, E.P. [Limnological Institute of the SB RAS, 664033 Irkutsk (Russian Federation); Zolotarev, K.B [Budker Institute of Nuclear Physics of SB RAS, Lavrentyev prospect -11, 630090 Novosibirsk (Russian Federation); Zhuchenko, N.A. [Limnological Institute of the SB RAS, 664033 Irkutsk (Russian Federation)

    2007-05-21

    High-resolution scanning Synchrotron Radiation X-ray Fluorescence Analysis (SRXFA) was applied to investigate the downcore distribution of elements in the sediments from Lake Baikal (East Siberia). The obtained multi-element time series reveal the presence of abrupt climate shifts in East Siberia which were synchronous with the abrupt warming events in the North Atlantic and Greenland (Dansgaard-Oeschges events (D/O) during the last ice age 24-75 kyr BP. We show here the set of climatic indicators reveals all globally known climate changes from dry and cool or glacial climates to humid and warm ones, which were recorded in Northern Atlantic and East Siberia both on the orbital and millennial time scales during the last 150 kyr.

  20. Seasonal variability in the surface sediments of Mobile Bay, Alabama, recorded by geochemistry and foraminifera, 2009–2010

    Science.gov (United States)

    Umberger, D.K.; Osterman, L.E.; Smith, C.G.; Frazier, J.; Richwine, K.A.

    2012-01-01

    A study was undertaken in order to document and quantify recent environmental change in Mobile Bay, Alabama. The study was part of the Northern Gulf of Mexico (NGOM) Ecosystem Change and Hazard Susceptibility project, a regional project funded by the Coastal and Marine Geology Program to understand how natural forcings and anthropogenic modifications influence coastal ecosystems and their susceptibility to coastal hazards. Mobile Bay is a large drowned-river estuary that has been modified significantly by humans to accommodate the Port of Mobile. Examples include repeated dredging of a large shipping channel down the central axis of the bay and construction of a causeway across the head of the bay and at the foot of the bayhead delta. In addition to modifications, the bay is also known to have episodic periods of low oxygen (hypoxia) that result in significant mortality to fish and benthic organisms (May, 1973). For this study a series of surface sediment samples were collected. Surface benthic foraminiferal and bulk geochemical data provide the modern baseline conditions of the bay and can be used as a reference to changing environmental parameters in the past (Osterman and Smith, in press) and into the future. This report archives data collected as part of the Mobile Bay Study that may be used in future environmental change studies.

  1. Sedimentary Records of Hyperpycnal Flows and the Influence of River Damming on Sediment Dynamics of Estuaries: Examples from the Nelson, Churchill, Moisie and Sainte-Marguerite Rivers (Canada)

    Science.gov (United States)

    St-Onge, G.; Duboc, Q.; Boyer-Villemaire, U.; Lajeunesse, P.; Bernatchez, P.

    2015-12-01

    Sediment cores were sampled in the estuary of the Nelson and Churchill Rivers in western Hudson Bay, as well as in the estuary of the Moisie and Sainte-Marguerite Rivers in Gulf of St. Lawrence in order to evaluate the impact of hydroelectric dams on the sedimentary regime of these estuaries. The gravity cores at the mouth of the Nelson River recorded several cm-thick rapidly deposited layers with a reverse to normal grading sequence, indicating the occurrence of hyperpycnal flows generated by major floods during the last few centuries. These hyperpycnal flows were probably caused by ice-jam formation, which can increase both the flow and the sediment concentration following the breaching of such natural dams. Following the construction of hydroelectric dams since the 1960s, the regulation of river discharge prevented the formation of hyperpycnal flows, and hence the deposition of hyperpycnites in the upper part of the cores. In the core sampled in the estuary of the Churchill River, only one hyperpycnite was recorded. This lower frequency may be due to the enclosed estuary of the Churchill River, its weaker discharge and the more distal location of the coring site.In the Gulf of St. Lawrence, grain size measurements allowed the identification of a major flood around AD 1844±4 years in box cores from both the Sainte-Marguerite and Moisie Rivers, whereas a drastic decrease in variations in the median grain size occurred around AD ~1900 in the estuary of the Sainte-Marguerite River, highlighting the offshore impact of the SM1 dam construction in the early 1900s. Furthermore, sedimentological variations in the box cores from both estuaries have been investigated by wavelet analysis and the sharp disappearance of high frequencies around AD 1900 in the estuary of the dammed river (Sainte-Marguerite River), but not in the estuary of the natural river (Moisie River), also provides evidence of the influence of dams on the sedimentary regime of estuaries.

  2. Evaluation of sediment trace metal records as paleoproductivity and paleoxygenation proxies in the upwelling center off Concepción, Chile (36°S)

    Science.gov (United States)

    Muñoz, Praxedes; Dezileau, Laurent; Lange, Carina; Cardenas, Lissette; Sellanes, Javier; Salamanca, Marco A.; Maldonado, Antonio

    2012-01-01

    This study analyzes the records of several trace metals sensitive to redox conditions in continental shelf sediments off Concepción, Chile (36°S). The continental margin off Concepción (36°S; 73°W) lies beneath an important upwelling center characterized by high primary production rates and, consequently, high fluxes of organic matter. In spring and summer, this material settles to the seafloor where it decays, producing periods of very low oxygen content in bottom waters (oxygen minimum zone develops at ∼100-400 m water depth, where dissolved oxygen levels are oxygen at the bottom increases drastically (>1 mL L -1). The goals of this study were to determine the input of trace metals to the sediment and to decipher how this information can be used to reveal variations in primary productivity or bottom oxygenation. Gravity cores collected at two stations - VG06-2 over the mid-shelf station (88 m water depth, upper boundary of the oxygen minimum zone) and VG06-3 over the outer shelf (120 m water depth, within the oxygen minimum zone) - were sampled for high resolution profiles (1 cm) of trace metals, biogenic opal, stable isotopes, and total organic carbon. The results suggest that the variability in the trace metal distribution on the continental shelf off Concepción is determined by redox conditions and the organic carbon flux to the bottom. Some sections of the sediment cores from the outer shelf showed appreciable authigenic enrichment of U, Cd, and Mo (EF: 5-10, 2-5, and 10-16 respectively) along with heavier values of δ 15N, suggesting periods of suboxic conditions. During these periods, fluxes of organic material to the bottom were higher, as indicated by elevated TOC and opal contents. Alternating periods of higher and lower trace metal contents were not observed mid-shelf as they were on the outer shelf. Rather, the mid-shelf samples showed authigenic enrichment of U, Cd, and Mo (EF: 1-6, 4-5, and 10-20, respectively) throughout the core except in a

  3. Marine sediment cores database for the Mediterranean Basin: a tool for past climatic and environmental studies

    Science.gov (United States)

    Alberico, I.; Giliberti, I.; Insinga, D. D.; Petrosino, P.; Vallefuoco, M.; Lirer, F.; Bonomo, S.; Cascella, A.; Anzalone, E.; Barra, R.; Marsella, E.; Ferraro, L.

    2017-06-01

    Paleoclimatic data are essential for fingerprinting the climate of the earth before the advent of modern recording instruments. They enable us to recognize past climatic events and predict future trends. Within this framework, a conceptual and logical model was drawn to physically implement a paleoclimatic database named WDB-Paleo that includes the paleoclimatic proxies data of marine sediment cores of the Mediterranean Basin. Twenty entities were defined to record four main categories of data: a) the features of oceanographic cruises and cores (metadata); b) the presence/absence of paleoclimatic proxies pulled from about 200 scientific papers; c) the quantitative analysis of planktonic and benthonic foraminifera, pollen, calcareous nannoplankton, magnetic susceptibility, stable isotopes, radionuclides values of about 14 cores recovered by Institute for Coastal Marine Environment (IAMC) of Italian National Research Council (CNR) in the framework of several past research projects; d) specific entities recording quantitative data on δ18O, AMS 14C (Accelerator Mass Spectrometry) and tephra layers available in scientific papers. Published data concerning paleoclimatic proxies in the Mediterranean Basin are recorded only for 400 out of 6000 cores retrieved in the area and they show a very irregular geographical distribution. Moreover, the data availability decreases when a constrained time interval is investigated or more than one proxy is required. We present three applications of WDB-Paleo for the Younger Dryas (YD) paleoclimatic event at Mediterranean scale and point out the potentiality of this tool for integrated stratigraphy studies.

  4. Tephrostratigraphy the DEEP site record, Lake Ohrid

    Science.gov (United States)

    Leicher, N.; Zanchetta, G.; Sulpizio, R.; Giaccio, B.; Wagner, B.; Francke, A.

    2016-12-01

    In the central Mediterranean region, tephrostratigraphy has been proofed to be a suitable and powerful tool for dating and correlating marine and terrestrial records. However, for the period older 200 ka, tephrostratigraphy is incomplete and restricted to some Italian continental basins (e.g. Sulmona, Acerno, Mercure), and continuous records downwind of the Italian volcanoes are rare. Lake Ohrid (Macedonia/Albania) in the eastern Mediterranean region fits this requisite and is assumed to be the oldest continuously existing lake of Europe. A continous record (DEEP) was recovered within the scope of the ICDP deep-drilling campaign SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid). In the uppermost 450 meters of the record, covering more than 1.2 Myrs of Italian volcanism, 54 tephra layers were identified during core-opening and description. A first tephrostratigraphic record was established for the uppermost 248 m ( 637 ka). Major element analyses (EDS/WDS) were carried out on juvenile glass fragments and 15 out of 35 tephra layers have been identified and correlated with known and dated eruptions of Italian volcanoes. Existing 40Ar/39Ar ages were re-calculated by using the same flux standard and used as first order tie points to develop a robust chronology for the DEEP site succession. Between 248 and 450 m of the DEEP site record, another 19 tephra horizons were identified and are subject of ongoing work. These deposits, once correlated with known and dated tephra, will hopefully enable dating this part of the succession, likely supported by major paleomagnetic events, such as the Brunhes-Matuyama boundary, or the Cobb-Mountain or the Jaramillo excursions. This makes the Lake Ohrid record a unique continuous, distal record of Italian volcanic activity, which is candidate to become the template for the central Mediterranean tephrostratigraphy, especially for the hitherto poorly known and explored lower Middle Pleistocene period.

  5. δD values of hydrated volcanic glass : a potential record of ancient meteoric water and climate in New Zealand

    International Nuclear Information System (INIS)

    Shane, P.; Ingraham, N.

    2002-01-01

    Tephra beds that are well drained and have been buried by thin paleosols become hydrated within 2-3000 yr on reaction with meteoric waters. Hence, the absorbed water within silicic volcanic glass shards provides a potential record of δD values of ancient meteoric water. Such isotopic records have previously received little investigation. We demonstrate that 1.5-2 m thick tephra beds in central North Island, New Zealand, display uniform δD values vertically through their profiles and laterally up to 250 m in outcrop. Reproducibility is not influenced by grain size or age of the tephra. We obtained an average δD value of -48 ± 3 permille for water within the 1.8 ka Taupo Tephra. This is similar to the composition of present-day surface waters. δD values of -73 ± 2 and -60 ± 2 permille for the 25 ka Kawakawa and 30 ka Mangaone Tephra beds are significantly lower than present waters, indicating that they have been hydrated under different surficial conditions. This is consistent with other proxy paleoclimatic indicators that suggest a cooler, drier, and windier climate at the time of their eruption. Tephra beds are a potential source of paleoclimatic data in terrestrial environments that otherwise may lack proxy records. (author). 17 refs., 5 figs., 3 tabs

  6. Quantitative summer temperature reconstruction derived from a combined biogenic Si and chironomid record from varved sediments of Lake Silvaplana (south-eastern Swiss Alps) back to AD 1177

    Science.gov (United States)

    Trachsel, M.; Grosjean, M.; Larocque-Tobler, I.; Schwikowski, M.; Blass, A.; Sturm, M.

    2010-09-01

    High-resolution quantitative temperature records are needed for placing the recent warming into the context of long-term natural climate variability. In this study we present a quantitative high-resolution (9-year) summer (June-August) temperature reconstruction back to AD 1177 for the south-eastern Swiss Alps. This region is a good predictor for summer temperatures in large parts of western and central Europe. Our reconstruction is based on a combination of the high-frequency component of annually resolved biogenic silica (bSi flux) data and the low-frequency component of decadal chironomid-inferred temperatures from annually laminated well dated sediments (varves) from proglacial Lake Silvaplana, eastern Swiss Alps. For the calibration (period AD 1760-1949) we assess systematically the effects of six different regression methods (Type I regressions: Inverse Regression IR, Inverse Prediction IP, Generalised Least Squares GLS; Type II regressions: Major Axis MA, Ranged Major Axis RMA and Standard Major Axis SMA) with regard to the predicted amplitude and the calibration statistics such as root-mean-square error of prediction (RMSEP), reduction of error (RE) and coefficient of efficiency (CE). We found a trade-off in the regression model choice between a good representation of the amplitude and good calibration statistics. The band-pass filtered bSi flux record is in close agreement both in the structure and the amplitude with two fully independent reconstructions spanning back to AD 1500 and AD 1177, respectively. All known pulses of negative volcanic forcing are represented as cold anomalies in the bSi flux record. Volcanic pulses combined with low solar activity (Spörer and Maunder Minimum) are seen as particularly cold episodes around AD 1460 and AD 1690. The combined chironomid and bSi flux temperature record (RMSEP = 0.57 °C) is in good agreement with the glacier history of the Alps. The warmest (AD 1190) and coldest decades (17th century; 1680-1700) of our

  7. Thermoluminescence dating of a tephra level from Baume Moula-Guercy (Soyons, Ardeche, France)

    International Nuclear Information System (INIS)

    Sanzelle, S.; Montret, M.; Pilleyre, T.; Miallier, D.; Fain, J.

    1998-01-01

    The Baume Moula-Guercy site (Ardeche, France) is a cave that overhangs the Rhone river valley at a hundred meters height. Since its discovery, it has been assimilated as a shelter with an upper part opened towards the sky. It contains an upper Pleistocene sequence inside which a 2-3 cm localized volcanic layer has been identified. This layer is attributed to an important phreato-magmatic emission from the Vivarais region located at about 50 km SW of the site. The filling of this cave contains neanderthalian remains in a lower level and middle Paleolithic lithic industries in a upper level. Thus, the dating of the tephra level would be of great archaeological importance as it could be used as a chronostratigraphic reference. An estimation of the age obtained by thermoluminescence dating has been requested. This report presents the dating procedure performed on quartz samples extracted from the tephra level and the estimation of the site dosimetry. (J.S.)

  8. Depositional record of trace metals and degree of contamination in core sediments from the Mandovi estuarine mangrove ecosystem, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Veerasingam, S.; Vethamony, P.; ManiMurali, R.; Fernandes, B.

    of sources. Enrichment of metals in bottom sediments represents a critical measure of health for any mangrove ecosystem (Janaki-Raman et al., 2007). Trace metals in coastal and estuarine sediments are incorporated into the aquatic food webs through primary... of susceptibility of the particles to the processes of physical and chemical weathering. The different morphological forms of iron oxides are well correlated with the sediment horizons. Spherical iron oxides predominate in the upper layers of sediment profiles...

  9. Long-term Records of Pacific Salmon Abundance From Sediment Core Analysis: Relationships to Past Climatic Change, and Implications for the Future

    Science.gov (United States)

    Finney, B.

    2002-12-01

    The response of Pacific salmon to future climatic change is uncertain, but will have large impacts on the economy, culture and ecology of the North Pacific Rim. Relationships between sockeye salmon populations and climatic change can be determined by analyzing sediment cores from lakes where sockeye return to spawn. Sockeye salmon return to their natal lake system to spawn and subsequently die following 2 - 3 years of feeding in the North Pacific Ocean. Sockeye salmon abundance can be reconstructed from stable nitrogen isotope analysis of lake sediment cores as returning sockeye transport significant quantities of N, relatively enriched in N-15, from the ocean to freshwater systems. Temporal changes in the input of salmon-derived N, and hence salmon abundance, can be quantified through downcore analysis of N isotopes. Reconstructions of sockeye salmon abundance from lakes in several regions of Alaska show similar temporal patterns, with variability occurring on decadal to millennial timescales. Over the past 2000 years, shifts in sockeye salmon abundance far exceed the historical decadal-scale variability. A decline occurred from about 100 BC - 800 AD, but salmon were consistently more abundant 1200 - 1900 AD. Declines since 1900 AD coincide with the period of extensive commercial fishing. Correspondence between these records and paleoclimatic data suggest that changes in salmon abundance are related to large scale climatic changes over the North Pacific. For example, the increase in salmon abundance c.a. 1200 AD corresponds to a period of glacial advance in southern Alaska, and a shift to drier conditions in western North America. Although the regionally coherent patterns in reconstructed salmon abundance are consistent with the hypothesis that climate is an important driver, the relationships do not always follow patterns observed in the 20th century. A main feature of recorded climate variability in this region is the alternation between multi-decade periods of

  10. Correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods: Review and evaluation

    Science.gov (United States)

    Lowe, David J.; Pearce, Nicholas J. G.; Jorgensen, Murray A.; Kuehn, Stephen C.; Tryon, Christian A.; Hayward, Chris L.

    2017-11-01

    We define tephras and cryptotephras and their components (mainly ash-sized particles of glass ± crystals in distal deposits) and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental, geological, and archaeological research. We then document and appraise recent advances in analytical methods used to determine the major, minor, and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application. Protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures. A narrow electron beam (diameter ∼3-5 μm) can now be used to analyze smaller glass shards than previously attainable. Reliable analyses of 'microshards' (defined here as glass shards T2 test). Randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful. Compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices, hierarchical cluster analysis, and PCA. Such transformations may make the assumption of multivariate normality more appropriate. A sequential procedure using Mahalanobis distance and the Hotelling two-sample T2 test is illustrated using glass major element data from trachytic to phonolitic Kenyan tephras. All these methods require a broad range of high-quality compositional data which can be used to compare 'unknowns' with reference (training) sets that are sufficiently complete to account for all possible correlatives, including tephras with heterogeneous glasses that contain multiple compositional groups. Currently, incomplete databases are tending to limit correlation efficacy. The development of an open, online global database to facilitate progress towards integrated, high

  11. A 700 year sediment record of black carbon and polycyclic aromatic hydrocarbons near the EMEP air monitoring station in Aspvreten, Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Marie Elmquist; Zdenek Zencak; Oerjan Gustafsson [Stockholm University, Stockholm (Sweden). Department of Applied Environmental Science

    2007-10-15

    In view of poor constraints on historical combustion emissions, past environmental loadings of black carbon (BC) and polycyclic aromatic hydrocarbon (PAH) were reconstructed from dated lake sediment cores collected 70 km south of Stockholm, Sweden. Compared to several dramatic variations over the recent 150 years, the preindustrial loadings were steady within {+-}50% through the entire medieval with BC fluxes of 0.071 g m{sup -2} yr{sup -1} and PAH fluxes of 6 g m{sup -2} yr{sup -1}. In the wood-burning dominated century leading up to the industrial revolution around 1850, increasing BC fluxes were leading PAH fluxes. BC fluxes reached their millennial-scale maximum around 1920, whereas PAH fluxes increased exponentially to its record maximum around 1960, 50-fold above preindustrial values. For 1920-1950, BC fluxes consistently decreased as PAH fluxes kept increasing. Coal and coke represented >50% of the Swedish energy market in the 1930s. Combined with sharply decreasing (1,7-)/(1,7{+-}2,6-dimethylphenanthrene), indicative of diminishing wood combustion, and decreasing methylphenanthrenes/phenanthrene, indicative of higher-temperature combustion (coal instead of wood), the sediment archive suggests that the relative BC/PAH emission factors thus are lower for coal than for wood combustion. For the first time, both BC and PAH fluxes decreased after 1960. This trend break is a testament to the positive effects of decreasing reliance on petroleum fuels and a number of legislative actions aimed at curbing emissions and by 1990, the loading of BC was back at preindustrial levels, whereas that of PAH were the lowest since the 1910s. However, for the most recent period (1990-2004) the BC and PAH fluxes are no longer decreasing. 55 refs., 3 figs.

  12. Laminated sediments from the central Peruvian continental slope: A 500 year record of upwelling system productivity, terrestrial runoff and redox conditions

    Science.gov (United States)

    Sifeddine, A.; Gutiérrez, D.; Ortlieb, L.; Boucher, H.; Velazco, F.; Field, D.; Vargas, G.; Boussafir, M.; Salvatteci, R.; Ferreira, V.; García, M.; Valdés, J.; Caquineau, S.; Mandeng Yogo, M.; Cetin, F.; Solis, J.; Soler, P.; Baumgartner, T.

    2008-10-01

    Sedimentological studies including X-ray digital analyses, mineralogy, inorganic contents, and organic geochemistry on cores of laminated sediments accumulated in the oxygen minimum zone of the central Peruvian margin reveal variable oceanographic and climate conditions during the last 500 yr. Coherent upcore variations in sedimentological and geochemical markers in box cores taken off Pisco (B0405-6) and Callao (B0405-13) indicate that variability in the climate proxies examined has regional significance. Most noteworthy is a large shift in proxies at ˜1820 AD, as determined by 210Pb and 14C radiometric dating. This shift is characterized by an increase in total organic carbon (TOC) in parallel with an abrupt increase in the enrichment factor for molybdenum Mo indicating a regional intensification of redox conditions, at least at the sediment water interface. In addition there was lower terrestrial input of quartz, feldspar and clays to the margin. Based on these results, we interpret that during several centuries prior to 1820, which corresponds to the little ice age (LIA), the northern Humboldt current region was less productive and experienced higher terrestrial input related to more humid conditions on the continent. These conditions were probably caused by a southward displacement of the inter-tropical convergence zone and the subtropical high pressure cell during the LIA. Since 1870, increases in TOC and terrigenous mineral fluxes suggest an increase of wind-driven upwelling and higher productivity. These conditions continued to intensify during the late 20th century, as shown by instrumental records of wind forcing.

  13. Long-term records of cadmium and silver contamination in sediments and oysters from the Gironde fluvial-estuarine continuum - evidence of changing silver sources.

    Science.gov (United States)

    Lanceleur, Laurent; Schäfer, Jörg; Chiffoleau, Jean-François; Blanc, Gérard; Auger, Dominique; Renault, Sophie; Baudrimont, Magalie; Audry, Stéphane

    2011-11-01

    The Gironde fluvial estuarine system is impacted by historic metal pollution (e.g. Cd, Zn, Hg) and oysters (Crassostrea gigas) from the estuary mouth have shown extremely high Cd concentrations for decades. Based on recent work (Chiffoleau et al., 2005) revealing anomalously high Ag concentrations (up to 65 mg kg(-1); dry weight) in Gironde oysters, we compared long-term (~1955-2001) records of Ag and Cd concentrations in reservoir sediment with the respective concentrations in oysters collected between 1979 and 2010 to identify the origin and historical trend of the recently discovered Ag anomaly. Sediment cores from two reservoirs upstream and downstream from the main metal pollution source provided information on (i) geochemical background (upstream; Ag: ~0.3 mg kg(-1); Cd: ~0.8 mg kg(-1)) and (ii) historical trends in Ag and Cd pollution. The results showed parallel concentration-depth profiles of Ag and Cd supporting a common source and transport. Decreasing concentrations since 1986 (Cd: from 300 to 11 mg kg(-1); Ag: from 6.7 to 0.43 mg kg(-1)) reflected the termination of Zn ore treatment in the Decazeville basin followed by remediation actions. Accordingly, Cd concentrations in oysters decreased after 1988 (from 109 to 26 mg kg(-1), dry weight (dw)), while Ag bioaccumulation increased from 38 up to 116 mg kg(-1), dw after 1993. Based on the Cd/Ag ratio (Cd/Ag~2) in oysters sampled before the termination of zinc ore treatment (1981-1985) and assuming that nearly all Cd in oysters originated from the metal point source, we estimated the respective contribution of Ag from this source to Ag concentrations in oysters. The evolution over the past 30 years clearly suggested that the recent, unexplained Ag concentrations in oysters are due to increasing contributions (>70% after 1999) by other sources, such as photography, electronics and emerging Ag applications/materials. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Diatom Surface Sediment Assemblages from the Bering Sea Shelf: a Tossed Salad or Faithful Recorder of 50 Years of Environmental Change?

    Science.gov (United States)

    Caissie, B.; Brigham-Grette, J.; Kanamaru-Shinn, K.

    2010-12-01

    Recent environmental change in the Bering Sea includes a shift from the negative to positive phase of the Pacific Decadal Oscillation in 1976/77, a secondary shift in sea level pressure and sea surface temperatures in 1998, increasing sea surface temperatures, an earlier spring, an increase in the number of days that sea ice is present along the shelf-slope break, and a decrease in the number of days that sea ice is present in the Chukchi Sea and Arctic Ocean. These physical changes have manifest biological changes such as a northward migration of invertebrates and fish from the southern Bering Sea and shifts in the timing and duration of sea-ice related primary productivity and the spring bloom. We aim to see if diatom sediment assemblages are faithful recorders of these ecological changes in the Bering Sea or if bioturbation has essentially mixed today’s rapid change down core such that the signal is either muted or no longer apparent. Six continental shelf areas were examined in the Bering Sea ranging from northeast of St. Lawrence Island to the shelf-slope break in the south-central Bering Sea. Diatom assemblages from core tops collected as part of the PROBES program in the 1960s were compared to core tops taken nearby (7 m) multi-year ice so their decline may be related to the decrease in multi-year ice over the past 30 years. Additionally, in most cases, species diversity has declined over the past 50 years with Fragilariopsis oceanica and Fragilariopsis cylindrus accounting for a greater percentage of the sediment assemblages today. These two species are collectively considered indicators of seasonal sea ice; their relative abundance peaks when ice is present for 5 months per year. Ongoing down core analyses in these six areas will further reveal the nature of these assemblage changes.

  15. Late Glacial and Early Holocene Climatic Changes Based on a Multiproxy Lacustrine Sediment Record from Northeast Siberia

    Energy Technology Data Exchange (ETDEWEB)

    Kokorowski, H D; Anderson, P M; Sletten, R S; Lozhkin, A V; Brown, T A

    2008-05-20

    Palynological (species assemblage, pollen accumulation rate), geochemical (carbon to nitrogen ratios, organic carbon and biogenic silica content), and sedimentological (particle size, magnetic susceptibility) data combined with improved chronology and greater sampling resolution from a new core from Elikchan 4 Lake provide a stronger basis for defining paleoenvironmental changes than was previously possible. Persistence of herb-dominated tundra, slow expansion of Betula and Alnus shrubs, and low percentages of organic carbon and biogenic silica suggest that the Late-Glacial transition (ca. 16,000-11,000 cal. yr BP) was a period of gradual rather than abrupt vegetation and climatic change. Consistency of all Late-Glacial data indicates no Younger Dryas climatic oscillation. A dramatic peak in pollen accumulation rates (ca. 11,000-9800 cal. yr BP) suggests a possible summer temperature optimum, but finer grain-sizes, low magnetic susceptibility, and greater organic carbon and biogenic silica, while showing significant warming at ca. 11,000 cal. yr BP, offer no evidence of a Holocene thermal maximum. When compared to trends in other paleo-records, the new Elikchan data underscore the apparent spatial complexity of climatic responses in Northeast Siberia to global forcings between ca. 16,000-9000 cal. yr BP.

  16. Atmospheric Despersal and Disposition of Tephra From a Potential Volcanic Eruption at Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    G. Keating; W.Statham

    2004-01-01

    The purpose of this model report is to provide documentation of the conceptual and mathematical model (ASHPLUME) for atmospheric dispersal and subsequent deposition of ash on the land surface from a potential volcanic eruption at Yucca Mountain, Nevada. This report also documents the ash (tephra) redistribution conceptual model. The ASHPLUME conceptual model accounts for incorporation and entrainment of waste fuel particles associated with a hypothetical volcanic eruption through the Yucca Mountain repository and downwind transport of contaminated tephra. The ASHPLUME mathematical model describes the conceptual model in mathematical terms to allow for prediction of radioactive waste/ash deposition on the ground surface given that the hypothetical eruptive event occurs. This model report also describes the conceptual model for tephra redistribution from a basaltic cinder cone. Sensitivity analyses and model validation activities for the ash dispersal and redistribution models are also presented. Analyses documented in this model report will improve and clarify the previous documentation of the ASHPLUME mathematical model and its application to the Total System Performance Assessment (TSPA) for the License Application (TSPA-LA) igneous scenarios. This model report also documents the redistribution model product outputs based on analyses to support the conceptual model

  17. Atmospheric Dispersal and Dispostion of Tephra From a Potential Volcanic Eruption at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    G. Keating; W.Statham

    2004-02-12

    The purpose of this model report is to provide documentation of the conceptual and mathematical model (ASHPLUME) for atmospheric dispersal and subsequent deposition of ash on the land surface from a potential volcanic eruption at Yucca Mountain, Nevada. This report also documents the ash (tephra) redistribution conceptual model. The ASHPLUME conceptual model accounts for incorporation and entrainment of waste fuel particles associated with a hypothetical volcanic eruption through the Yucca Mountain repository and downwind transport of contaminated tephra. The ASHPLUME mathematical model describes the conceptual model in mathematical terms to allow for prediction of radioactive waste/ash deposition on the ground surface given that the hypothetical eruptive event occurs. This model report also describes the conceptual model for tephra redistribution from a basaltic cinder cone. Sensitivity analyses and model validation activities for the ash dispersal and redistribution models are also presented. Analyses documented in this model report will improve and clarify the previous documentation of the ASHPLUME mathematical model and its application to the Total System Performance Assessment (TSPA) for the License Application (TSPA-LA) igneous scenarios. This model report also documents the redistribution model product outputs based on analyses to support the conceptual model.

  18. A 27 ka paleoenvironmental lake sediment record from Taro Co, central Tibetan Plateau: implications for the interplay between monsoon and the Westerlies

    Science.gov (United States)

    Wang, J.; Ma, Q.; Huang, L.; Ju, J.; Guo, Y.; Lin, X.; Li, Y.; Zhu, L.

    2017-12-01

    The climate of Tibetan Plateau (TP) is mainly influenced by the Indian Ocean Summer Monsoon (IOSM) and the Westerlies. The interaction of these two air masses is therefore a crucial scientific issue to understand how they impact the climate in this area, especially in the geological times. However, constrained by the available archives, researches on this topic are still very few in the hinterland of the TP, especially covering the Last Glacial Maximum (LGM) period. Here we present a new lake sediment record retrieved from Taro Co covering the last 27 ka to elucidate how the IOSM and the Westerlies interact and the possible mechanisms. Taro Co (486 km2, Dmax: 132m, 4565 m a.s.l., currently closed), located on the central TP, is a fresh lake with the major supply from glaciers. Two parallel piston cores as well as several gravity cores were retrieved from the deepest parts. These cores were correlated based on high resolution XRF scanning and a continuous 1069 cm-long core was finally integrated. Chronology was determined by 210Pb, 137Cs and AMS 14C measurements. Multidiscipline analyses including grain size, total organic carbon (TOC), total nitrogen, diatom, ostracod, pollen and n-alkanes were accomplished to reconstruct paleoenvironmental changes. The lake level of Taro Co was low since 27 cal ka BP indicated by very coarse materials and diatom assemblages with gradually increased temperature and salinity (TOC and carbonate getting higher). The terrestrial water input decreased continuously reflected by such elements as Si, Ti, Fe, K. It is likely that there was a sedimentation gap between 961-954cm, corresponding to 23.4 to 18.6 cal ka BP probably demonstrated Taro Co was very shallow at that period. The first prominent abrupt change of most proxies was observed at 14.7 cal ka BP showing a great lake deepening which likely indicated an enhancement of IOSM. There were several spells with abrupt changes of cold/warm stages before the Holocene and the Younger Dryas

  19. Geochemistry of tephra from Bed I, Olduvai Gorge, Tanzania: Stratigraphic correlations and implications for magmatic evolution

    Science.gov (United States)

    McHenry, L.

    2003-04-01

    At least 10 predominantly trachytic and rhyolitic tuffs are preserved interbedded in volcaniclastic sediments of Plio-Pleistocene Bed I, Olduvai Gorge, Tanzania. Physical correlation of the tuffs is complicated by faulting and variation in preservation and lithofacies. Differences in the degree and type of tephra alteration (clay, zeolitic, none) and preservation of glass shards within the various depositional environments (saline-alkaline lake, lake margin, wetlands, alluvial fan) make correlation by conventional glass chemistry methods impossible. However, variations in overall mineralogy and chemical compositions of co-magmatic phenocrysts (feldspar, augite, titanomagnetite, amphibole) have proven useful to uniquely characterize the tuffs for correlation purposes. Samples of 10 major tuffs in the Olduvai Bed I sequence were collected from various depostional and preservational environments situated up to 15 km apart. Thin sections and mineral separates (10-60 grains of each type of phenocryst/ sample, 2-3 samples/ tuff) were analyzed by electron microprobe for major and minor elements. The lower Bed I tuffs are rhyolitic and easily distinguished from the upper tuffs by the presence of quartz and high-Fe augite. Feldspar composition has been previously found to separate all of the upper tuffs (1B-1F) except the two trachyandesitic tuffs (1D and the "unnamed" tuff between 1E and 1F). Mn and Ti concentrations in the titanomagnetites separate the upper tuffs (MnO%: 1B=1.5-2, 1C=1.3-1.6, 1D=1.1-1.4, 1E=1.5-1.7, unnamed= 0.9-1.2, 1F=1.6-2; TiO2%: 1B, 1E=23-26, 1C=18-22, 1D=25-27, unnamed=20-21, 1F= 12-20). Tuffs 1B, unnamed, and 1F contain abundant amphibole, 1D contains none. Mn and Fe concentrations in the augites also separate the tuffs (MnO%: 1B=1.2-1.5, 1C=0.9-1.2, 1D=0.6-0.9, 1E=0.9-1.1, unnamed=0.5-0.7, 1F=variable; FeO%: 1B=19-21, 1C=15-19, 1D=12-16, 1E=13-16, unnamed=11-14, 1F=variable). Results of these findings provide new widespread markers in the Olduvai

  20. Revised Late Oligocene to Early Miocene magnetic stratigraphy recorded by drift sediments at Sites U1405 and U1406, IODP Expedition 342 (Newfoundland, NW Atlantic)

    Science.gov (United States)

    van Peer, Tim; Xuan, Chuang; Wilson, Paul; Liebrand, Diederik; Lippert, Peter

    2015-04-01

    to impact the completeness of the spliced magnetostratigraphic record. Rock and mineral magnetic studies of selected samples are currently ongoing to characterise the magnetic mineralogy of the sediments and how it changes across the stratigraphic gaps and intervals with contrasting lithological and/or palaeomagnetic properties. These data will help us understand the origin of the palaeomagnetic signal and test its reliability, while providing insights on the nature of the observed stratigraphic gaps and how they relate to global climate dynamics of the OMT and the Deep Western Boundary Current.

  1. Geological Development of the Izu-Bonin Forearc Since the Eocene Based on Biostratigraphic, Rock Magnetic, and Sediment Provenance Observations from IODP Expedition 352 Drill Cores

    Science.gov (United States)

    Petronotis, K. E.; Robertson, A.; Kutterolf, S.; Avery, A.; Baxter, A.; Schindlbeck, J. C.; Wang, K. L.; Acton, G.

    2016-12-01

    International Ocean Discovery Program (IODP) Expedition 352 recovered early Oligocene to recent sediments above Eocene igneous basement at 4 sites in the Izu-Bonin Forearc. The sites were selected to investigate the forearc region since subduction initiation in the Eocene, with Sites U1439 and U1442 being cored into the upper trench slope and Sites U1440 and U1441 into the lower trench slope. Postcruise studies of biostratigraphy, sediment chemistry, tephra composition and chronology and magnetic properties, along with observations from prior coring help constrain the regional geological development. Volcanic activity in the area, as inferred from its influence on sediment composition, has varied between long periods of activity and quiescence. Combined whole-rock sediment chemistry and tephra compositions suggest that during the Oligocene to earliest Miocene ( 30-22 Ma) tuffaceous input of predominantly dacitic composition was mainly derived from the intra-oceanic Izu-Bonin Arc. The early Miocene interval ( 22-15 Ma) lacks tuffaceous input, as supported by rock magnetic data. During this period, the forearc subsided beneath the carbonate compensation depth (CCD), as evidenced by radiolarian-bearing mud and metal-rich silty clay. This was followed by input of tephra with bimodal felsic and mafic compositions from the Izu-Bonin Arc from 15 to 5 Ma. Middle Miocene to Quaternary time was characterized by increased carbonate preservation, coupled with abundant, predominantly felsic tephra input, which is chemically indicative of a Japan continental arc source (Honshu), with additional chemically distinctive input from the Izu-Bonin Arc. Extending back to 32 Ma, tephra layers can be correlated between the upper-slope sites, extrapolated to the less well-dated lower-slope sites, and further correlated with onland Japanese tephra (Kutterolf et al., 2016; Goldschmidt Conference). Overall, the new results provide an improved understanding of the regional tectonic evolution.

  2. Wisconsin Glaciation of the Sierra Nevada (79,000-15,000 yr B.P.) as Recorded by Rock Flour in Sediments of Owens Lake, California

    Science.gov (United States)

    Bischoff, James L.; Cummins, Kathleen

    2001-01-01

    Chemical analyses of the clay-sized fractions of 564 continuous sediment samples (200-yr resolution) from composite core OL90/92 allow quantification of an abundance of glacial rock flour. Rock flour produced during glacier advances is represented by clay-sized plagioclase, K-feldspar, and biotite in homogeneous internal composition. The abundance of rock flour is deemed proportional to the intensity of glacies advances. Age control for the composite section is provided by combining previously published radiocarbon dates on organics, U/Th dates on ostracode shells, and U/Th dates on saline minerals from nearby Searles Lake correlated to OL92 by pollen. The rock flour record displays three levels of variability: (1) a dominant one of about 20,000 yr related to summer insolation and precipitation; (2) an intermediate one of 3000-5000 yr, perhaps related to North Atlantic Heinrich events; and (3) a minor one of 1000-2000 yr, perhaps related to North Atlantic thermohaline-driven air-temperature variation.

  3. First fossil record of Alphonsea Hk. f. & T. (Annonaceae from the Late Oligocene sediments of Assam, India and comments on its phytogeography.

    Directory of Open Access Journals (Sweden)

    Gaurav Srivastava

    Full Text Available A new fossil leaf impression of Alphonsea Hk. f. & T. of the family Annonaceae is described from the Late Oligocene sediments of Makum Coalfield, Assam, India. This is the first authentic record of the fossil of Alphonsea from the Tertiary rocks of South Asia. The Late Oligocene was the time of the last significant globally warm climate and the fossil locality was at 10°-15°N palaeolatitude. The known palaeoflora and sedimentological studies indicate a fluvio-marine deltaic environment with a mosaic of mangrove, fluvial, mire and lacustrine depositional environments. During the depositional period the suturing between the Indian and Eurasian plates was not complete to facilitate the plant migration. The suturing was over by the end of the Late Oligocene/beginning of Early Miocene resulting in the migration of the genus to Southeast Asia where it is growing profusely at present. The present study is in congruence with the earlier published palaeofloral and molecular phylogenetic data. The study also suggests that the Indian plate was not only a biotic ferry during its northward voyage from Gondwana to Asia but also a place for the origin of several plant taxa.

  4. Acoustic and Shear-Wave Velocities in Hydrate-Bearing Sediments Offshore Southwestern Taiwan: Tomography, Converted Waves Analysis and Reverse-Time Migration of OBS Records

    Directory of Open Access Journals (Sweden)

    Philippe Schnurle

    2006-01-01

    Full Text Available A 2.5-D combined seismic reflection and refraction survey has been conducted in the accretionary complex offshore of southwestern Taiwan where BSRs (Bottom Simulating Reflectors are highly concentrated and geochemical signals for the presence of gas hydrate are strong. In this study, we perform velocity analysis of the 6 4-component OBS (Ocean-Bottom Seismometer records along the southernmost transect of this seismic experiment. We utilize 3 independent methods in order to accurately determine the acoustic and shear-wave velocities of the sediments: 1-D Root Mean Square (RMS analysis of the P-P and P-S reflected events on individual datumed components, 2-D inversion of the P-P and P-S reflected and refracted events along the in-line transect, and 3-D acoustic inversion of the first arrivals. The principal sources of bias in the determination of the velocities are the 3-dimentional nature of the topography and the complexity of the underlying structures. The three methods result in consistent velocity profiles. Rapid lateral and vertical variations of the velocities are observed. We then investigate the large scale gas hydrate content through rock physic modeling: at the vertical of each OBS, shear-waves velocities are utilized to estimate the water-filled porosities, and the acoustic velocities predicted for a set of gas hydrate, quartz and clay contents are compared to the observed profiles.

  5. Spatial and Temporal Variability of Dust Deposition in the San Juan Mountains, CO: A Network of Late Holocene Lake Sediment Records

    Science.gov (United States)

    Arcusa, S.; Routson, C.; McKay, N.

    2017-12-01

    Millions of stakeholders living in the arid southwestern US rely on snowmelt from the San Juan Mountains of Colorado. However, dust deposition on snow accelerates snowmelt, challenging water management. Dustiness in the southwestern US is primarily mediated by drought, which is projected to increase in frequency and severity. Over the past several millennia, multidecadal-length megadroughts are hypothesized to have enhanced regional dustiness. These past megadroughts were more frequent during the Roman (ca. 1-400 CE) and Medieval (ca. 800-1300 CE) time periods and were similar in duration and severity to those projected for the future. Developing an understanding of the temporal and spatial patterns of past dust deposition in the San Juan Mountains will help inform adaptation strategies for future droughts. A network of short sediment cores from six alpine lakes in the San Juan Mountains were collected in 2016 and 2017 to investigate the spatial patterns of dust deposition. The range in lake basin characteristics in the network, such as catchment size, helps to constrain the influence of secondary dust deposition. Grain size analysis and X-ray Fluorescence were combined with radiocarbon dating to trace the temporal patterns in dust flux over the Late Holocene (the last 2000 years). The End-member Modelling Algorithm (EMMA) was used to estimate the dust proportion in the lake sediment, distinguishing from locally derived catchment material. Comparisons to modern dust-on-snow samples were made to identify the dust size distribution. The results show that deposition trends were not uniform between the south-eastern and north-western San Juans, with increasing trends towards the present in the former, possibly reflecting a shift in dust sources associated with changes in wind speed and direction. Dust levels greater than long term averages were recorded during the Medieval and Roman periods. The network also showed the influence of lake basin parameters, such as the

  6. Paleovegetation changes recorded by n-alkyl lipids bound in macromolecules of plant fossils and kerogens from the Cretaceous sediments in Japan

    Science.gov (United States)

    Miyata, Y.; Sawada, K.; Nakamura, H.; Takashima, R.; Takahashi, M.

    2014-12-01

    Resistant macromolecules composing living plant tissues tend to be preserved through degradation and diagenesis, hence constituate major parts of sedimentary plant-derived organic matter (kerogen), and their monomer compositions vary widely among different plant taxa, organs and growth stages. Thus, analysis of such macromolecule may serve as new technique for paleobotanical evaluation distinctive from classical paleobotnical studies depends on morphological preservation of fossils. In the present study, we analyzed plant fossils and kerogens in sediments from the Cretaceous strata in Japan to examine chemotaxonomic characteristics of fossil macromolecules and to reconstruct paleovegetation change by kerogen analysis. The kerogens were separated from the powdered sediments of Cretaceous Yezo Group, Hokkaido, Japan. All kerogens have been confirmed to be mostly originated from land plant tissues by microscopic observation. Mummified angiosperm and gymnosperm fossil leaves were separated from carbonaceous sandstone of the Cretaceous Ashizawa Formation, Futaba Group. The kerogens and plant fossils were extracted with methanol and dichloromethane, and were subsequently refluxed under 110°C to remove free compounds completely. The residues are hydrolyzed by KOH/methanol under 110°C. These released compounds are analyzed by GC-MS. As main hydrolyzed products (ester-bound molecular units) from all kerogens, C10-C28 n-alkanoic acids and C10-C30 n-alkanols were detected. Recent studies on the hydrolysis products of plant tissues suggested the long chain (>C20) n-alkanols were predominantly abundant in deciduous broadleaved angiosperms. Correspondingly, the stratigraphic variation of the ratios of long chain (>C20) n-alkanols to fatty acids was concordant with the variation of angiosperm/gymnosperm ratios recorded by land plant-derived terpenoid biomarkers. In addition, we found that the long chain n-alkanols/fatty acids ratio in the angiosperm fossil leaf was

  7. Dating young tephras - a distal solution to proximal controversy

    Science.gov (United States)

    Chen, Xuanyu; Blockley, Simon; Xu, Yigang; Menzies, Martin

    2017-04-01

    In-situ dating of young volcanic rocks (environmental data. Assessment of the temporal and spatial variations of such climatic events will help us better understand the dynamics of these rapid and short-lived climatic episodes. References: Broecker, W.S., 2001. Was the Medieval Warm Period Global? Science, 291(5508): 1497-1499. Chen, X.-Y., Blockley, S.P.E., Tarasov, P.E., Xu, Y.-G., McLean, D., Tomlinson, E.L., Albert, P.G., Liu, J.-Q., Müller, S., Wagner, M. and Menzies, M.A., 2016. Clarifying the distal to proximal tephrochronology of the Millennium (B-Tm) eruption, Changbaishan Volcano, northeast China. Quat. Geochronol., 33: 61-75. Ge, Q. and Wu, W., 2011. Climate during the Medieval Climate Anomaly in China. PAGES news, 19: 24-26. Sun, C., Plunkett, G., Liu, J., Zhao, H., Sigl, M., McConnell, J.R., Pilcher, J.R., Vinther, B., Steffensen, J.P. and Hall, V., 2014. Ash from Changbaishan Millennium eruption recorded in Greenland ice: Implications for determining the eruption's timing and impact. Geophys. Res. Lett., 2013GL058642.

  8. Reply to the comment on "Geochemistry of buried river sediments from Ghaggar Plains, NW India: Multi-proxy records of variations in provenance, paleoclimate, and paleovegetation patterns in the Late Quaternary" by Singh et al. (2016), Palaeogeography, Palaeoclimatology, Palaeoecology 449 (2016) 85-100

    DEFF Research Database (Denmark)

    Singh, Ajit; Paul, Debajyoti; Sinha, Rajiv

    2016-01-01

    In the comment on our paper (this issue), Clift et al. (2016) compared our recently reported radiogenic Nd-isotopic record in two drill cores (Singh et al., 2016) with those from the Hakra floodplain sediments and Indus Delta sediments. While they agree with the concept of erosion patterns...... of these sediments. Moreover, we note that whereas our paper considers a similar to 75 ka fluvial depositional record, their comment is only based on the post-Last Glacial Maximum (LGM) record. When considering the longer record, their arguments do not negate the main conclusions of our original paper. (c) 2016...

  9. Extending the turbidity record: making additional use of continuous data from turbidity, acoustic-Doppler, and laser diffraction instruments and suspended-sediment samples in the Colorado River in Grand Canyon

    Science.gov (United States)

    Voichick, Nicholas; Topping, David J.

    2014-01-01

    Turbidity is a measure of the scattering and absorption of light in water, which in rivers is primarily caused by particles, usually sediment, suspended in the water. Turbidity varies significantly with differences in the design of the instrument measuring turbidity, a point that is illustrated in this study by side-by-side comparisons of two different models of instruments. Turbidity also varies with changes in the physical parameters of the particles in the water, such as concentration, grain size, grain shape, and color. A turbidity instrument that is commonly used for continuous monitoring of rivers has a light source in the near-infrared range (860±30 nanometers) and a detector oriented 90 degrees from the incident light path. This type of optical turbidity instrument has a limited measurement range (depending on pathlength) that is unable to capture the high turbidity levels of rivers that carry high suspended-sediment loads. The Colorado River in Grand Canyon is one such river, in which approximately 60 percent of the range in suspended-sediment concentration during the study period had unmeasurable turbidity using this type of optical instrument. Although some optical turbidimeters using backscatter or other techniques can measure higher concentrations of suspended sediment than the models used in this study, the maximum turbidity measurable using these other turbidimeters may still be exceeded in conditions of especially high concentrations of suspended silt and clay. In Grand Canyon, the existing optical turbidity instruments remain in use in part to provide consistency over time as new techniques are investigated. As a result, during these periods of high suspended-sediment concentration, turbidity values that could not be measured with the optical turbidity instruments were instead estimated from concurrent acoustic attenuation data collected using side-looking acoustic-Doppler profiler (ADP) instruments. Extending the turbidity record to the full

  10. Detrital zircon provenance from three turbidite depocenters of the Middle-Upper Triassic Songpan-Ganzi complex, central China: Record of collisional tectonics, erosional exhumation, and sediment production

    Science.gov (United States)

    Weislogel, A.L.; Graham, S.A.; Chang, E.Z.; Wooden, J.L.; Gehrels, G.E.

    2010-01-01

    To test the idea that the voluminous upper Middle to Upper Triassic turbidite strata in the Songpan-Ganzi complex of central China archive a detrital record of Dabie ultrahigh-pressure (UHP) terrane unroofing, we report 2080 single detrital U-Pb zircon ages by sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis from 29 eastern Songpan-Ganzi complex sandstone samples. Low (Th/U zircons, consistent with crystallization under UHP conditions, are rare in eastern Songpan-Ganzi complex zircon, and U-Pb ages of low Th/U zircons are incompatible with a Dabie terrane source. An unweighted pair group method with arithmetic mean nearest-neighbor analysis of Kolmogorov-Smirnov two-sample test results reveals that the eastern Songpan-Ganzi complex is not a single contiguous turbidite system but is instead composed of three subsidiary depocenters, each associated with distinct sediment sources. The northeastern depocenter contains zircon ages characterized by Paleozoic and bimodally distributed Precambrian zircon populations, which, together with south-to southeast-directed paleocurrent data, indicate derivation from the retro-side of the Qinling-Dabie (Q-D) collisional orogen wedge. In the central depocenter, the dominantly Paleozoic detrital zircon signature and south-to southwest-oriented paleocurrent indicators reflect a profusion of Paleozoic zircon grains. These data are interpreted to reflect an influx of material derived from erosion of Paleozoic supra-UHP rocks of the Dabie terrane in the eastern Qinling-Dabie orogen, which we speculate may have been enhanced by development of a monsoonal climate. This suggests that erosional unroofing played a significant role in the initial phase of UHP exhumation and likely influenced the petrotectonic and structural evolution of the Qinling-Dabie orogen, as evidenced by compressed Triassic isotherms/grads reported in the Huwan

  11. Record of environmental and climatic changes in middle Pleistocene sediments from Łuków (eastern Poland on the basis of plant macroremains analysis

    Directory of Open Access Journals (Sweden)

    Stachowicz-Rybka Renata

    2015-06-01

    Full Text Available Lacustrine sediments at the Łuków site bear a record of the Ferdynandovian interglacial, correlated with Marine Isotope Stage (MIS 13-15, including two warm periods of interglacial rank (climatostratigraphic units Ferdynandovian 1 and 2 separated by cooling/glaciation (Ferdynandovian 1/2. On the basis of plant macroremains analysis, the type of local vegetation in the lake and its surroundings as well as changes in climate, trophic conditions and water level were reconstructed in detail. Ferdynandovian 1 was a time of development of tall sedge swamps. The presence of Najas marina and N. minor also suggests high levels of eutrophication, particularly in the younger part of the climatic optimum. The occurrence of Zannichellia palustris indicates habitats of variable water level and high salt content. In the terminocratic phase of Ferdynandovian 1, the communities showed the reoccurrence of Betula nana, B. humilis and Larix sp., the disappearance of thermophilous trees, and the intensification of succession processes linked to climate cooling. In the cool Ferdynandovian 1/2, Betula nana and Cenococcum geophilum increased their frequencies, most likely due to enhanced supply of mineral matter to the basin. During Ferdynandovian 2, the next climate warming of interglacial rank, communities of aquatic vegetation with the highest share of thermophilous taxa included the extinct Aldrowanda borysthenica, Brasenia borysthenica, and Scirpus atroviroides, as well as Cyperus glomeratus, a species not presently found in the flora of Poland. Another cooling in the Sanian 2 (Elsterian 2 glaciation is indicated by the development of peat communities, with numerous Carex sp., Menyanthes trifoliata, Eriophorum vaginatum, and Andromeda polifolia, accompanied by the extinct Carex paucifloroides, Caulinia macrosperma, and Potamogeton praemaackianus.

  12. The RESET project: constructing a European tephra lattice for refined synchronisation of environmental and archaeological events during the last c. 100 ka

    Czech Academy of Sciences Publication Activity Database

    Lowe, J. J.; Ramsey, C. B.; Housley, R. A.; Lane, C. S.; Tomlinson, E. L.; Stringer, C.; Davies, W.; Barton, N.; Pollard, M.; Gamble, C.; Menzies, M.; Rohling, E.; Roberts, A.; Blockley, S.; Cullen, V.; Grant, K.; Lewis, M.; MacLeod, A.; White, D.; Albert, P.; Hardiman, M.; Lee, S.; Oh, A.; Satow, C.; Cross, J. K.; Bramham Law, C.; Todman, A.; Bourne, A.; Matthews, I.; Müller, W.; Smith, V.; Wulf, S.; Anghelinu, M.; Antl-Weiser, W.; Bar-Yosef, O.; Borić, D.; Boscato, P.; Ronchitelli, A.; Chabai, V.; Veselsky, A.; Uthmeier, T.; Farrand, W.; Gjipali, I.; Ruka, R.; Güleç, E.; Karavanić, I.; Karkanas, P.; King, T.; Komšo, D.; Koumouzelis, M.; Kyparissi, N.; Lengyel, G.; Mester, Z.; Neruda, P.; Nigst, P.; Haesaerts, P.; Panagopoulou, E.; Shalamanov-Korobar, L.; Tolevski, I.; Sinitsyn, A.; Sirakov, N.; Guadelli, A.; Guadelli, J.-L.; Ferrier, C.; Škrdla, Petr; Slimak, L.; Soler, N.; Soller, J.; Soressi, M.; Tushabramishvilii, N.; Zilhão, J.; Angelucci, D.; Cullen, V. L.; Lincoln, P.; Staff, R.; Flower, K.; Aouadi-Abdeljaouad, N.; Belhouchet, L.; Barker, G.; Bouzouggar, A.; Van Peer, P.; Kindermann, K.; Gerken, K.; Niemann, H.; Tipping, R.; Saville, A.; Ward, T.; Clausen, I.; Weber, M.-J.; Kaiser, K.; Torksdorf, J. F.; Turner, F.; Veil, S.; Nygaard, N.; Pyne-O'Donnel, S. D. F.; Masojć, M.; Nalepka, D.; Jurochnik, A.; Kabaciński, J.; Antoine, P.; Olive, M.; Christensen, M.; Bodu, P.; Debout, G.; Orliac, M.; De Bie, M.; Van Gils, M.; Paulissen, E.; Brou, L.; Leesch, D.; Hadorn, P.; Thew, N.; Riede, F.; Heinen, M.; Joris, O.; Richter, J.; Knipping, M.; Stika, H.-P.; Friedrich, M.; Conard, N. J.; Malina, M.; Kind, C.-J.; Beutelspacher, T.; Mortensen, M. F.; Burdukiewicz, J. M.; Szynkiewicz, A.; Połtowicz-Bobak, M.; Bobak, D.; Wiśniewski, A.; Przeździecki, M.; Valde-Nowak, P.; Muzyczuk, A.; Davies, L.; Morgan, P.; Aydar, E.; Çubukçu, E.; Brown, R.; Coltelli, M.; Lo Castro, D.; Cioni, R.; DeRosa, R.; Donato, P.; Di Roberto, A.; Gertisser, R.; Giordano, G.; Branney, M.; Jordan, N.; Keller, J.; Kinvig, H.; Gottsman, J.; Blundy, J.; Marani, M.; Orsi, G.; Civetta, L.; Arienzo, I.; Carandente, A.; Rosi, M.; Zanchetta, G.; Seghedi, I.; Szakacs, A.; Sulpizio, R.; Thordarson, T.; Trincardi, F.; Vigliotti, L.; Asioli, A.; Piva, A.; Andrič, M.; Brauer, A.; de Klerk, P.; Filippi, M.-L.; Finsinger, W.; Galović, L.; Jones, T.; Lotter, A.; Müller, U.; Pross, J.; Mangerud, J.; Lohne, Ø.; Pyne-O'Donnell, S.; Markovic, S.; Pini, R.; Ravazzi, C.; Theuerkauf, M.; Tzedakis, C.; Margari, V.; Veres, D.; Wastegård, S.; Ortiz, J. E.; Torres, T.; Díaz-Bautista, A.; Moreno, A.; Valero-Garcés, B.; Lowick, S.; Ottolini, L.

    2015-01-01

    Roč. 118, 15 June 2015 (2015), s. 1-17 ISSN 0277-3791 Institutional support: RVO:68081758 Keywords : Last Glacial stage * Dansgaard-Oeschger and Heinrich events * Abrupt environmental transitions (AETs) * Middle to Upper Palaeolithic * Volcanic ash isochrons * Tephra geochemistry * Tephra database Subject RIV: AC - Archeology, Anthropology, Ethnology Impact factor: 4.521, year: 2015

  13. New zircon (U-Th)/He and U/Pb eruption age for the Rockland tephra, western USA

    Science.gov (United States)

    Coble, Matthew A.; Burgess, Seth D.; Klemetti, Erik W.

    2017-09-01

    Eruption ages of a number of prominent Quaternary volcanic deposits remain inaccurately and/or imprecisely constrained, despite their importance as regional stratigraphic markers in paleo-environment reconstruction and as evidence of climate-altering eruptions. Accurately dating volcanic deposits presents challenging analytical considerations, including poor radiogenic yield, scarcity of datable minerals, and contamination of crystal populations by magma, eruption, and transport processes. One prominent example is the Rockland tephra, which erupted from the Lassen Volcanic Center in the southern Cascade arc. Despite a range in published eruption ages from 0.40 to 0.63 Ma, the Rockland tephra is extensively used as a marker bed across the western United States. To more accurately and precisely constrain the age of the Rockland tephra-producing eruption, we report U/Pb crystallization dates from the outermost ∼2 μm of zircon crystal faces (surfaces) using secondary ion mass spectrometry (SIMS). Our new weighted mean 238U/206Pb age for Rockland tephra zircon surfaces is 0.598 ± 0.013 Ma (2σ) and MSWD = 1.11 (mean square weighted deviation). As an independent test of the accuracy of this age, we obtained new (U-Th)/He dates from individual zircon grains from the Rockland tephra, which yielded a weighted mean age of 0.599 ± 0.012 Ma (2σ, MSWD = 5.13). We also obtained a (U-Th)/He age of 0.628 ± 0.014 Ma (MSWD = 1.19) for the Lava Creek Tuff member B, which was analyzed as a secondary standard to test the accuracy of the (U-Th)/He technique for Quaternary tephras, and to evaluate assumptions made in the model-age calculation. Concordance of new U/Pb and (U-Th)/He zircon ages reinforces the accuracy of our preferred Rockland tephra eruption age, and confirms that zircon surface dates sample zircon growth up to the time of eruption. We demonstrate the broad applicability of coupled U/Pb zircon-surface and single-grain zircon (U-Th)/He geochronology to accurate

  14. Multi-criteria correlation of tephra deposits to source centres applied in the Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Hopkins, Jenni L.; Wilson, Colin J. N.; Millet, Marc-Alban; Leonard, Graham S.; Timm, Christian; McGee, Lucy E.; Smith, Ian E. M.; Smith, Euan G. C.

    2017-07-01

    Linking tephras back to their source centre(s) in volcanic fields is crucial not only to reconstruct the eruptive history of the volcanic field but also to understand tephra dispersal patterns and thus the potential hazards posed by a future eruption. Here we present a multi-disciplinary approach to correlate distal basaltic tephra deposits from the Auckland Volcanic Field (AVF) to their source centres using proximal whole-rock geochemical signatures. In order to achieve these correlations, major and trace element tephra-derived glass compositions are compared with published and newly obtained whole-rock geochemical data for the entire field. The results show that incompatible trace element ratios (e.g. (Gd/Yb)N, (La/Yb)N, (Zr/Yb)N) vary widely across the AVF (e.g. (La/Yb)N = 5 to 40) but show a more restricted range within samples from a single volcanic centre (e.g. (La/Yb)N = 5 to 10). These ratios are also the least affected by fractional crystallisation and are therefore the most appropriate geochemical tools for correlation between tephra and whole-rock samples. However, findings for the AVF suggest that each volcanic centre does not have a unique geochemical signature in the field as a whole, thus preventing unambiguous correlation of tephras to source centre using geochemistry alone. A number of additional criteria are therefore combined to further constrain the source centres of the distal tephras including age, eruption scale, and location (of centres, and sites where tephra were sampled). The combination of tephrostratigraphy, 40Ar/39Ar dating and morphostratigraphic constraints allow, for the first time, the relative and absolute ordering of 48 of 53 volcanic centres of the Auckland Volcanic Field to be resolved. Eruption frequencies are shown to vary between 0.13 and 1.5 eruptions/kyr and repose periods between individual eruptions vary from <0.1 to 13 kyr, with 23 of the 48 centres shown to have pre-eruptive repose periods of <1000 years. No spatial

  15. Character, mass, distribution, and origin of tephra-fall deposits of the 1989-1990 eruption of redoubt volcano, south-central Alaska

    Science.gov (United States)

    Scott, W.E.; McGimsey, R.G.

    1994-01-01

    The 1989-1990 eruption of Redoubt Volcano spawned about 20 areally significant tephra-fall deposits between December 14, 1989 and April 26, 1990. Tephra plumes rose to altitudes of 7 to more than 10 km and were carried mainly northward and eastward by prevailing winds, where they substantially impacted air travel, commerce, and other activities. In comparison to notable eruptions of the recent past, the Redoubt events produced a modest amount of tephra-fall deposits - 6 ?? 107 to 5 ?? 1010 kg for individual events and a total volume (dense-rock equivalent) of about 3-5 ?? 107 m3 of andesite and dacite. Two contrasting tephra types were generated by these events. Pumiceous tephra-fall deposits of December 14 and 15 were followed on December 16 and all later events by fine-grained lithic-crystal tephra deposits, much of which fell as particle aggregates. The change in the character of the tephra-fall deposits reflects their fundamentally different modes of origin. The pumiceous deposits were produced by magmatically driven explosions. The finegrained lithic-crystal deposits were generated by two processes. Hydrovolcanic vent explosions generated tephrafall deposits of December 16 and 19. Such explosions continued as a tephra source, but apparently with diminishing importance, during events of January and February. Ash clouds of lithic pyroclastic flows generated by collapse of actively growing lava domes probably contributed to tephra-fall deposits of all events from January 2 to April 26, and were the sole source of tephra fall for at least the last 4 deposits. ?? 1994.

  16. End-Pleistocene to Holocene paleoenvironmental record from piston corer samples and the challenge of stratigraphic correlation of playa sediment data with a connected alluvial apron from Damghan Basin, Iran

    Science.gov (United States)

    Büdel, Christian; Hoelzmann, Philipp; Wennrich, Volker; Majid Padashi, Sajed; Baumhauer, Roland

    2015-04-01

    The study yields a first characterization and correlation of the end-Pleistocene to Holocene sediment archive of playa and playa lake deposits in the Damghan Basin, northern Iran. The Basin sediments are deposited since Mio- and Pliocene, which is valid for the connected alluvial fans, too. These are covering the area between the playa and mountains and while prograding from the mountain ranges they deliver gravels and fine-sediments to the basins sink. The processes on the studied alluvial apron are described and dated already and can be explained in seven morphodynamic phases, which are linked to a general lake level high-stand in north-east Iran at about 8000-9000 years ago. If and how these phases are passed on from the alluvial record down to the playa sediment record is aim of this study. Today the salt pans margins are highly affected by salt tectonic drifting and access was suboptimal. Only here drilling could be performed through about 280 centimeters of salt-crust unfrequently intercalated with loamy layers. For yielding undisturbed playa sediment records sampling was performed with inliner-tubes deployed in a piston corer (Kullenberg type). Thus at two different drilling sites in summation seven cores could be taken, down to a maximum depth of 129 cm and 1000 cm. Back in Germany the cores had been opened and initially described, photographed and optically scanned with a core logger. Regarding future studies, the aim was a best possible comprehensive documentation of the cores. Therefore basically grainsize measurements (laser diffraction), multi element analyses (XRF, ICP-OES, titrimetry) and mineralogical measurements (XRD) had been deployed on samples taken from every single previously identified layer. Continuous elemental data was secured by use of a XRF-scanning core logger. The sedimentological description together with laboratory element analyses shows saline conditions in the first three meters coincide with general coarser grain sizes. The next

  17. Post depositional memory record of mercury in sediment near effluent disposal site of a chlor-alkali plant in Thane Creek-Mumbai Harbour, India

    Digital Repository Service at National Institute of Oceanography (India)

    Ram, A.; Rokade, M.A.; Zingde, M.D.; Borole, D.V.

    in landfills, mine tailings, contaminated industrial sites, soils and sediments. Estuaries and coastal marine regions form an essential link in the global biogeochemical cycling of Hg between the terrestrial environment - the major repository for atmospheric... by close relationship with organic matter, and Fe and Al oxides or sorbed onto the mineral particles [8]. Hence, sediments adjacent to the outfalls of chlor-alkali plants frequently contain high levels of Hg [7,10-15]. Some natural processes (water, soil...

  18. Paleosecular Type Curves for South America Based on Holocene-Pleistocene Lake Sediments Studies

    Science.gov (United States)

    Gogorza, C. S.

    2007-05-01

    Most of the high-resolution paleomagnetic secular variation (PSV) results were obtained from records on sediments from the Northern Hemisphere. Experimental results from South America are scarce. The first results were obtained by Creer et al. (1983) and have been continued since few years ago by the author and collaborators. This review deals with studies of PSV records from bottom sediments from three lakes: Escondido, Moreno and El Trébol (south-western Argentina, 41° S, 71° 30'W). Measurements of directions (declination D and inclination I) and intensity of natural remanent magnetization (NRM), magnetic susceptibility at low and high frequency (specific, X and volumetric, k), isothermal remanent magnetization (IRM), saturation isothermal remanent magnetization (SIRM), and back field were carried out. Stability of the NRM was investigated by alternating-field demagnetization. Rock magnetic studies suggest that the main carriers of magnetization are ferrimagnetic minerals, predominantly pseudo single domain magnetite. The correlation between cores was based on magnetic parameters as X and NRM. The tephra layers were identified from the lithologic profiles and also from the magnetic susceptibility logs. Due to their different chronological meaning and their rather bad behavior as magnetic recorder, these layers were removed from the sequence and the gaps that were produced along the profiles by the removal were closed, obtaining a "shortened depth". Radiocarbon age estimates from these cores and from earlier studies allow us to construct paleosecular variation records for the past 22,000 years. Inclination and declination curves (Gogorza et al., 2000a; Gogorza et al., 2002; Irurzun et al., 2006) show trends that are similar to a paleomagnetic secular variation curve for SW of Argentina (Gogorza et al., 2000b). References Creer, K.M., Tucholka, P. and Barton, C.E. 1983. Paleomagnetism of lake sediments, in Geomagnetism of Baked Clays and Recent Sediments, edited

  19. Studies of environmental radioactivity in Cumbria. Part 6. The chronology of discharges of caesium-137, plutonium and americium-241 from BNFL Sellafield, as recorded in lake sediments

    Energy Technology Data Exchange (ETDEWEB)

    Eakins, J D; Cambray, R S

    1985-04-01

    A study has been made of the radionuclide content of lake sediments from Cumbria in order to determine the history of discharges of /sup 137/Cs and actinides from the Sellafield works of British Nuclear Fuels plc (BNFL). Sediment cores have been taken from Ullswater and Grasmere, which are remote from Sellafield, in order to establish the behaviour of nuclear weapon fallout nuclides. Cores have also been taken from Barfield Tarn, which is 19 km SE of Sellafield but close to the sea, and from Ponsonby and Harnsey Moss Tarns, close to Sellafield. All sediments were analysed for /sup 137/Cs and sup(239+240)Pu. Additional measurements of /sup 238/Pu and /sup 241/Am were made on samples from the closer tarns. The sediment cores were dated by the /sup 210/Pb method and, where appropriate, by the /sup 137/Cs technique also. The amounts of /sup 137/Cs and sup(239+240)Pu in sediments from Barfield Tarn could be accounted for by fallout from nuclear weapons, although the levels of /sup 241/Am were marginally greater. However in Harnsey Moss Tarn the levels of actinides indicated that they were derived mainly from material originally discharged to sea from Sellafield. Sediment from Ponsonby Tarn contained material derived mainly from discharges to atmosphere.

  20. Sedimentation rates of lake Haruna in the past 200 years as revealed by tephrochronology, 210Pb and 137Cs methods

    International Nuclear Information System (INIS)

    Ishiwatari, Ryoshi; Uchida, Kuniko; Nagasaka, Hiromitsu; Tsukamoto, Sumiko

    2010-01-01

    A 90 cm sediment core (HAR 99A) from Lake Haruna, Gumma Prefecture, Japan was dated by tephrochronology, lead-210 and cesium-137 methods and was compared stratigraphically with the cores obtained in 1966 (HAR 96B) and 1971 (HAR 71). For the HAR 99A core, the 24-26 cm depth layer was estimated to be AD 1963 by 137 Cs. The tephra layer in 62-66 cm depth was identified to be volcanic ashes from Asama volcano eruption (Asama-A tephra: As-A) in AD 1783. Average mass sedimentation rate (AMSR) for 1963 to 1999 (0-26 cm depth) is 0.050 g cm -2 yr -1 and that for 1783 to 1963 (25-62 cm depth) is 0.033 g cm -2 yr -1 . AMSR for the 0-62 cm depth obtained by 210 Pb ranges between 0.052 and 0.058 g cm -2 yr -1 . In addition, it is proposed that the previous assignment of As-B (AD 1108) for a tephra layer at 40-50 cm depth of the HAR 71 core should be changed to As-A tephra (AD 1783). (author)

  1. Late Pleistocene and Holocene paleoclimate and alpine glacier fluctuations recorded by high-resolution grain-size data from an alpine lake sediment core, Wind River Range, Wyoming, USA

    Science.gov (United States)

    Thompson Davis, P.; Machalett, Björn; Gosse, John

    2013-04-01

    Varved lake sediments, which provide ideal high-resolution climate proxies, are not commonly available in many geographic areas over long time scales. This paper utilizes high-resolution grain-size analyses (n = 1040) from a 520-cm long sediment core from Lower Titcomb Lake (LTL), which lies just outside the type Titcomb Basin (TTB) moraines in the Wind River Range, Wyoming. The TTB moraines lie between Lower Titcomb Lake and Upper Titcomb Lake (UTL), about 3 km beyond, and 200 m lower than the modern glacier margin and Gannett Peak (Little Ice Age) moraines in the basin. Based on cosmogenic exposure dating, the TTB moraines are believed to be Younger Dryas (YD) age (Gosse et al., 1995) and lie in a geomorphic position similar to several other outer cirque moraines throughout the western American Cordillera. Until recently, many of these outer cirque moraines were believed to be Neoglacial age. The sediment core discussed here is one of five obtained from the two Titcomb Lakes, but is by the far the longest with the oldest sediment depositional record. Two AMS radiocarbon ages from the 445- and 455-cm core depths (about 2% loss on ignition, LOI) suggest that the lake basin may have been ice-free as early as 16.1 or even 16.8 cal 14C kyr, consistent with 10Be and 26Al exposure ages from boulders and bedrock surfaces outside the TTB moraines. The 257-cm depth in the core marks an abrupt transition from inorganic, sticky gray silt below (rock flour production between the 257 and 466 cm core depths appear to be roughly correlative with the YD-Alleröd-Bölling-Meiendorf-Heinrich 1 climate events recognized in other terrestrial records and Northern Atlantic Ocean marine cores, but provide much higher resolution than most of those records from a climate-sensitive alpine region in North America.

  2. Fate and agricultural consequences of leachable elements added to the environment from the 2011 Cordón Caulle tephra fall

    Science.gov (United States)

    Stewart, Carol; Craig, Heather M.; Gaw, Sally; Wilson, Thomas; Villarosa, Gustavo; Outes, Valeria; Cronin, Shane; Oze, Christopher

    2016-11-01

    The June 2011 eruption of Cordón Caulle volcano, Chile, dispersed tephra over 350,000 km2, including productive agricultural land. This resulted in the death of nearly one million livestock. Two distinct environments were affected: a proximal temperate Andean setting, and the semi-arid Argentine steppe farther from the volcano. The purpose of this study was to better understand the fate and agricultural consequences of leachable elements added to the environment by this large silicic tephra fall. Tephra, soil and surface water samples across the depositional area were collected both immediately after the eruption (tephra and water) and nine months afterwards (tephra, soil and water). Tephra samples were analysed following a new hazard assessment protocol developed by the International Volcanic Health Hazard Network (IVHHN). Water-extractable element concentrations in freshly-collected tephra were very low to low compared to other eruptions, and showed no trends with distance from the volcano. Surface water analyses suggested short-term changes to water composition due to the release of elements from tephra. No effect on the fertility of soils underlying tephra was apparent after nine months. Water-extractable fluorine (F) in freshly-collected tephra ranged from 12 to 167 mg/kg, with a median value of 67 mg/kg. Based on parallels with the 11-12 October 1995 eruption of Ruapehu volcano, New Zealand, we conclude that F toxicity was a possible contributing factor to the large-scale livestock deaths as well as to chronic fluorosis widely reported in wild deer populations across the Cordón Caulle tephra depositional area. Finally, we recommend that effective response to widespread tephra fall over agricultural areas should include: (1) rapid, statistically representative field sampling of tephra, soils, surface water supplies and forage crops; (2) analysis using appropriate and reliable laboratory methods; (3) modelling both short and long-term impacts on the ecosystem

  3. Introducing Geoscience Students to Numerical Modeling of Volcanic Hazards: The example of Tephra2 on VHub.org

    Directory of Open Access Journals (Sweden)

    Leah M. Courtland

    2012-07-01

    Full Text Available The Tephra2 numerical model for tephra fallout from explosive volcanic eruptions is specifically designed to enable students to probe ideas in model literacy, including code validation and verification, the role of simplifying assumptions, and the concepts of uncertainty and forecasting. This numerical model is implemented on the VHub.org website, a venture in cyberinfrastructure that brings together volcanological models and educational materials. The VHub.org resource provides students with the ability to explore and execute sophisticated numerical models like Tephra2. We present a strategy for using this model to introduce university students to key concepts in the use and evaluation of Tephra2 for probabilistic forecasting of volcanic hazards. Through this critical examination students are encouraged to develop a deeper understanding of the applicability and limitations of hazard models. Although the model and applications are intended for use in both introductory and advanced geoscience courses, they could easily be adapted to work in other disciplines, such as astronomy, physics, computational methods, data analysis, or computer science.

  4. ATMOSPHERIC DISPERSAL AND DEPOSITION OF TEPHRA FROM A POTENTIAL VOLCANIC ERUPTION AT YUCCA MOUNTAIN, NEVADA

    International Nuclear Information System (INIS)

    C. Harrington

    2004-01-01

    The purpose of this model report is to provide documentation of the conceptual and mathematical model (Ashplume) for atmospheric dispersal and subsequent deposition of ash on the land surface from a potential volcanic eruption at Yucca Mountain, Nevada. This report also documents the ash (tephra) redistribution conceptual model. These aspects of volcanism-related dose calculation are described in the context of the entire igneous disruptive events conceptual model in ''Characterize Framework for Igneous Activity'' (BSC 2004 [DIRS 169989], Section 6.1.1). The Ashplume conceptual model accounts for incorporation and entrainment of waste fuel particles associated with a hypothetical volcanic eruption through the Yucca Mountain repository and downwind transport of contaminated tephra. The Ashplume mathematical model describes the conceptual model in mathematical terms to allow for prediction of radioactive waste/ash deposition on the ground surface given that the hypothetical eruptive event occurs. This model report also describes the conceptual model for tephra redistribution from a basaltic cinder cone. Sensitivity analyses and model validation activities for the ash dispersal and redistribution models are also presented. Analyses documented in this model report update the previous documentation of the Ashplume mathematical model and its application to the Total System Performance Assessment (TSPA) for the License Application (TSPA-LA) igneous scenarios. This model report also documents the redistribution model product outputs based on analyses to support the conceptual model. In this report, ''Ashplume'' is used when referring to the atmospheric dispersal model and ''ASHPLUME'' is used when referencing the code of that model. Two analysis and model reports provide direct inputs to this model report, namely ''Characterize Eruptive Processes at Yucca Mountain, Nevada and Number of Waste Packages Hit by Igneous Intrusion''. This model report provides direct inputs to

  5. ATMOSPHERIC DISPERSAL AND DEPOSITION OF TEPHRA FROM A POTENTIAL VOLCANIC ERUPTION AT YUCCA MOUNTAIN, NEVADA

    Energy Technology Data Exchange (ETDEWEB)

    C. Harrington

    2004-10-25

    The purpose of this model report is to provide documentation of the conceptual and mathematical model (Ashplume) for atmospheric dispersal and subsequent deposition of ash on the land surface from a potential volcanic eruption at Yucca Mountain, Nevada. This report also documents the ash (tephra) redistribution conceptual model. These aspects of volcanism-related dose calculation are described in the context of the entire igneous disruptive events conceptual model in ''Characterize Framework for Igneous Activity'' (BSC 2004 [DIRS 169989], Section 6.1.1). The Ashplume conceptual model accounts for incorporation and entrainment of waste fuel particles associated with a hypothetical volcanic eruption through the Yucca Mountain repository and downwind transport of contaminated tephra. The Ashplume mathematical model describes the conceptual model in mathematical terms to allow for prediction of radioactive waste/ash deposition on the ground surface given that the hypothetical eruptive event occurs. This model report also describes the conceptual model for tephra redistribution from a basaltic cinder cone. Sensitivity analyses and model validation activities for the ash dispersal and redistribution models are also presented. Analyses documented in this model report update the previous documentation of the Ashplume mathematical model and its application to the Total System Performance Assessment (TSPA) for the License Application (TSPA-LA) igneous scenarios. This model report also documents the redistribution model product outputs based on analyses to support the conceptual model. In this report, ''Ashplume'' is used when referring to the atmospheric dispersal model and ''ASHPLUME'' is used when referencing the code of that model. Two analysis and model reports provide direct inputs to this model report, namely ''Characterize Eruptive Processes at Yucca Mountain, Nevada and Number of Waste Packages Hit

  6. Assessing the long-term probabilistic volcanic hazard for tephra fallout in Reykjavik, Iceland: a preliminary multi-source analysis

    Science.gov (United States)

    Tonini, Roberto; Barsotti, Sara; Sandri, Laura; Tumi Guðmundsson, Magnús

    2015-04-01

    Icelandic volcanism is largely dominated by basaltic magma. Nevertheless the presence of glaciers over many Icelandic volcanic systems results in frequent phreatomagmatic eruptions and associated tephra production, making explosive eruptions the most common type of volcanic activity. Jökulhlaups are commonly considered as major volcanic hazard in Iceland for their high frequency and potentially very devastating local impact. Tephra fallout is also frequent and can impact larger areas. It is driven by the wind direction that can change with both altitude and season, making impossible to predict a priori where the tephra will be deposited during the next eruptions. Most of the volcanic activity in Iceland occurs in the central eastern part, over 100 km to the east of the main population centre around the capital Reykjavík. Therefore, the hazard from tephra fallout in Reykjavík is expected to be smaller than for communities settled near the main volcanic systems. However, within the framework of quantitative hazard and risk analyses, less frequent and/or less intense phenomena should not be neglected, since their risk evaluation depends on the effects suffered by the selected target. This is particularly true if the target is highly vulnerable, as large urban areas or important infrastructures. In this work we present the preliminary analysis aiming to perform a Probabilistic Volcanic Hazard Assessment (PVHA) for tephra fallout focused on the target area which includes the municipality of Reykjavík and the Keflavík international airport. This approach reverts the more common perspective where the hazard analysis is focused on the source (the volcanic system) and it follows a multi-source approach: indeed, the idea is to quantify, homogeneously, the hazard due to the main hazardous volcanoes that could pose a tephra fallout threat for the municipality of Reykjavík and the Keflavík airport. PVHA for each volcanic system is calculated independently and the results

  7. Tephrochronology of the Brooks River Archaeological District, Katmai National Park and Preserve, Alaska: What can and cannot be done with tephra deposits

    Science.gov (United States)

    Riehle, J.R.; Dumond, D.E.; Meyer, C.E.; Schaaf, J.M.

    2000-01-01

    The Brooks River Archaeological District (BRAD) in Katmai National Park and Preserve is a classical site for the study of early humans in Alaska. Because of proximity to the active Aleutian volcanic arc, there are numerous tephra deposits in the BRAD, which are potentially useful for correlating among sites of archaeological investigations. Microprobe analyses of glass separates show, however, that most of these tephra deposits are heterogeneous mixtures of multiple glass populations. Some glasses are highly similar to pyroclasts of Aniakchak Crater (160 km to the south), others are similar to pyroclasts in the nearby Valley of Ten Thousand Smokes, and some are similar to no other tephra samples from the Alaska Peninsula. Moreover, tephra deposits in any one archaeological study site are not always similar to those from nearby sites, indicating inconsistent preservation of these mainly thin, fine-grained deposits. At least 15, late Holocene tephra deposits are inferred at the BRAD. Their heterogeneity is the result of either eruptions of mixed or heterogeneous magmas, like the 1912 Katmai eruption, or secondary mixing of closely succeeding tephra deposits. Because most cannot be reliably distinguished from one another on the basis of megascopic properties, their utility for correlations is limited. At least one deposit can be reliably identified because of its thickness (10 cm) and colour stratification. Early humans seem not to have been significantly affected by these tephra falls, which is not surprising in view of the resilience exhibited by both plants and animals following the 1912 Katmai eruption.

  8. Reply to the comment on "Geochemistry of buried river sediments from Ghaggar Plains, NW India: Multi-proxy records of variations in provenance, paleoclimate, and paleovegetation patterns in the Late Quaternary" by Singh et al. (2016), Palaeogeography, Palaeoclimatology, Palaeoecology 449 (2016) 85-100

    DEFF Research Database (Denmark)

    Singh, Ajit; Paul, Debajyoti; Sinha, Rajiv

    2016-01-01

    of these sediments. Moreover, we note that whereas our paper considers a similar to 75 ka fluvial depositional record, their comment is only based on the post-Last Glacial Maximum (LGM) record. When considering the longer record, their arguments do not negate the main conclusions of our original paper. (c) 2016...

  9. A 60-year record of 129I in Taal Lake sediments (Philippines): Influence of human nuclear activities at low latitude region

    DEFF Research Database (Denmark)

    Zhang, Luyuan; Hou, Xiaolin; Li, Hong-chun

    2017-01-01

    in the Taal Lake core appears to be the signal of the Chernobyl accident in 1986. In addition, volcanic activities are reflected in the iodine isotope profiles in the sediment core, suggesting the potential of using iodine isotopes as an indicator of volcanic eruptions.......The influence of human nuclear activities on environmental radioactivity is not well known at low latitude region that are distant from nuclear tests sites and nuclear facilities. A sediment core collected from Taal Lake in the central Philippines was analyzed for 129I and 127I to investigate...

  10. Luminescence property of volcanic quartz and the use of red isothermal TL for dating tephras

    International Nuclear Information System (INIS)

    Tsukamoto, S.; Murray, A.S.; Huot, S.; Watanuki, T.; Denby, P.M.; Botter-Jensen, L.

    2007-01-01

    An optically stimulated luminescence (OSL) age obtained from a Japanese tephra using quartz phenocrysts severely underestimated the known age. The characteristics of the OSL signals were investigated in order to understand the cause of the underestimation; the main OSL component of volcanic quartz has a thermodynamic lifetime of about 1700 years at room temperature, and it also seems to fade anomalously (i.e. athermally). Measurement of conventional red thermoluminescence (RTL) using a Ga-As photomultiplier tube was difficult due to the presence of a strong thermal background, although RTL gave an age consistent with the independent age. Furthermore, red isothermal TL (RITL) at 380 deg. C allowed the RTL signal to be separated from to the thermal background, and RITL ages of three volcanic quartz samples show good agreement with independent ages

  11. A 300 kyr record of aridity and wind strength in southwestern Africa: evidence from grain-size distributions of sediments on Walvis Ridge, SE Atlantic.

    NARCIS (Netherlands)

    Stuut, J.-B. W.; Prins, M.A.; Schneider, R.S.; Weltje, G.J.; Jansen, J.H.F.; Postma, G.

    2002-01-01

    The terrigenous fraction of sediments recovered from Walvis Ridge, SE Atlantic Ocean, reveals a history of southwestern African climate of the last 300 kyr. End-member modelling of a data set of grain-size distributions (n = 428) results in three end members. The two coarsest end members are

  12. Holocene history of the Baltic Sea as a background for assessing records of human impact in the sediments of the Gotland Basin

    DEFF Research Database (Denmark)

    Andrén, E.; Andrén, T.; Kunzendorf, Helmar

    2000-01-01

    Sediment cores from the Gotland Basin were studied for their siliceous microfossil assemblages and organic carbon content to compare recent environmental changes in the Baltic Sea with its natural long-term history. Age models were constructed using Pb-210, Cs-137 and corrected and calibrated C-14...

  13. A geochemical record of environmental changes in sediments from Sishili Bay, northern Yellow Sea, China: Anthropogenic influence on organic matter sources and composition over the last 100 years

    International Nuclear Information System (INIS)

    Wang, Yujue; Liu, Dongyan; Richard, Pierre; Li, Xin

    2013-01-01

    Highlights: • Increased TOC and TN in the sediment cores indicated a eutrophic trend since 1975. • Marine organic matter sources dominated in Sishili Bay. • Scallop culture displayed mitigation on eutrophication pressures in Sishili Bay. • Increased fertilizer use well matched eutrophic process in Sishili Bay in 1975. -- Abstract: Total organic carbon (TOC), total nitrogen (TN), δ 13 C and δ 15 N were measured in sediment cores at three sites in Sishili Bay, China, to track the impacts of anthropogenic activities on the coastal environment over the last 100 years. The increased TOC and TN in the upper section of sediment cores indicated a eutrophic process since 1975. In comparison, the TOC and TN in the sediment core near to a scallop aquaculture area displayed a much slower increase, indicating the contribution of scallop aquaculture in mitigating eutrophication. Combined information from δ 13 C, δ 15 N and TOC:TN indicated an increased terrestrial signal, although organic matter sources in Sishili Bay featured a mixture of terrestrial and marine sources, with phytoplankton being dominant. Increased fertilizer use since 1970s contributed to the eutrophic process in Sishili Bay since 1975, and increased sewage discharge from 1990s has added to this process

  14. Rock magnetic and geochemical record in a sediment core from the eastern Arabian Sea: Diagenetic and environmental implications during the late quaternary

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P; Kessarkar, P; Patil, S.K.; Ahmad, S.M.

    . The sediments are dominated by fine-grained magnetite, but intervals of 1.2-3.8 kaBP and 10-13.5 kaBP were subjected to diagenetic changes, resulting in the dissolution of fine-grained magnetites and enrichment of redox-sensitive trace elements (Cu, Ni, Zn, V...

  15. Lake ecosystem response to rapid lateglacial climate changes in lake sediments from northern Poland

    Science.gov (United States)

    Słowiński, Michał; Zawiska, Izabela; Ott, Florian; Noryśkiewicz, Agnieszka M.; Apolinarska, Karina; Lutyńska, Monika; Michczyńska, Danuta J.; Brauer, Achim; Wulf, Sabine; Skubała, Piotr; Błaszkiewicz, Mirosław

    2013-04-01

    During the Late Glacial Period environment changes were triggered by climatic oscillations which in turn controlled processes like, for example, permafrost thawing, vegetation development and ground water circulation. These environmental changes are ideally recorded in lake sediments and thus can be reconstructed applying a multi-poxy approach. Here, we present the results from the Trzechowskie paleolake, located in the northern Polish lowlands (eastern part of the Pomeranian Lakeland). The site is situated on the outwash plain of the Wda River, which was formed during the Pomeranian phase of the Vistulian glaciation ca 16,000 14C yrs BP. The depression of the Trzechowskie lake basin formed after melting of a buried ice block during the Allerød (13903±170 cal yrs BP). We reconstructed environmental changes in the Trzechowskie paleolake and its catchment using biotic proxies (macrofossils, pollen, cladocera, diatoms, oribatidae mite) and geochemical proxies (δ18O, δ13C, loss-on-ignition (LOI), CaCO3 content). In addition, we carried out µ-XRF element core scanning. The chronology has been established by means of biostratigraphyAMS14C dating on plant macro remains, varve counting in laminated intervals and the late Allerød Laacher See Tephra isochrone. Our results showed that biogenic accumulation in the lake started during the Bølling. Development of coniferous forest during the Allerød with dominance of Pinus sylvestris lead to leaching of carbonates in the catchment due to low pH increasing the flux of Ca ions into the lake. In consequence calcite precipitating in the lake increased as evidences by increasing CaCO3 contents. Both biotic and physical proxies clearly reflect the rapid decrease in productivity at the onset of the Younger Dryas. We compare the data from the Trzechowskie paleolake with the Meerfelder Maar and Rehwiese lake records based on tephrochronological synchronization using the Laacher See Tephra. This study is a contribution to the

  16. Adjusting particle-size distributions to account for aggregation in tephra-deposit model forecasts

    Science.gov (United States)

    Mastin, Larry G.; Van Eaton, Alexa; Durant, A.J.

    2016-01-01

    Volcanic ash transport and dispersion (VATD) models are used to forecast tephra deposition during volcanic eruptions. Model accuracy is limited by the fact that fine-ash aggregates (clumps into clusters), thus altering patterns of deposition. In most models this is accounted for by ad hoc changes to model input, representing fine ash as aggregates with density ρagg, and a log-normal size distribution with median μagg and standard deviation σagg. Optimal values may vary between eruptions. To test the variance, we used the Ash3d tephra model to simulate four deposits: 18 May 1980 Mount St. Helens; 16–17 September 1992 Crater Peak (Mount Spurr); 17 June 1996 Ruapehu; and 23 March 2009 Mount Redoubt. In 192 simulations, we systematically varied μagg and σagg, holding ρagg constant at 600 kg m−3. We evaluated the fit using three indices that compare modeled versus measured (1) mass load at sample locations; (2) mass load versus distance along the dispersal axis; and (3) isomass area. For all deposits, under these inputs, the best-fit value of μagg ranged narrowly between  ∼  2.3 and 2.7φ (0.20–0.15 mm), despite large variations in erupted mass (0.25–50 Tg), plume height (8.5–25 km), mass fraction of fine ( discrete process that is insensitive to eruptive style or magnitude. This result offers the potential for a simple, computationally efficient parameterization scheme for use in operational model forecasts. Further research may indicate whether this narrow range also reflects physical constraints on processes in the evolving cloud.

  17. Sediment delivery and lake dynamics in a Mediterranean mountain watershed: Human-climate interactions during the last millennium (El Tobar Lake record, Iberian Range, Spain).

    Science.gov (United States)

    Barreiro-Lostres, Fernando; Brown, Erik; Moreno, Ana; Morellón, Mario; Abbott, Mark; Hillman, Aubrey; Giralt, Santiago; Valero-Garcés, Blas

    2015-11-15

    Land degradation and soil erosion are key environmental problems in Mediterranean mountains characterized by a long history of human occupation and a strong variability of hydrological regimes. To assess recent trends and evaluate climatic and anthropogenic impacts in these highly human modified watersheds we apply an historical approach combining lake sediment core multi-proxy analyses and reconstructions of past land uses to El Tobar Lake watershed, located in the Iberian Range (Central Spain). Four main periods of increased sediment delivery have been identified in the 8m long sediment sequence by their depositional and geochemical signatures. They took place around 16th, late 18th, mid 19th and early 20th centuries as a result of large land uses changes such as forest clearing, farming and grazing during periods of increasing population. In this highly human-modified watershed, positive synergies between human impact and humid periods led to increased sediment delivery periods. During the last millennium, the lake depositional and geochemical cycles recovered quickly after each sediment delivery event, showing strong resilience of the lacustrine system to watershed disturbance. Recent changes are characterized by large hydrological affections since 1967 with the construction of a canal from a nearby reservoir and a decreased in anthropic pressure in the watershed as rural areas were abandoned. The increased fresh water influx to the lake has caused large biological changes, leading to stronger meromictic conditions and higher organic matter accumulation while terrigenous inputs have decreased. Degradation processes in Iberian Range watersheds are strongly controlled by anthropic activities (land use changes, soil erosion) but modulated by climate-related hydrological changes (water availability, flood and runoff frequency). Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Sedimentary record of polycyclic aromatic hydrocarbons in a sediment core from a maar lake, Northeast China: evidence in historical atmospheric deposition.

    Science.gov (United States)

    Guan, Yu-Feng; Sun, Jian-Lin; Ni, Hong-Gang; Guo, Jian-Yang

    2012-09-01

    A maar lake is an excellent ecosystem to study the atmospheric deposition of pollutants, as its contaminants are primarily by atmospheric deposition. In this study, a sediment core from Sihailongwan Maar Lake, Northeast China, was collected and the historical atmospherically deposited polycyclic aromatic hydrocarbons (PAHs) were analyzed. The concentrations of TPAHs (the sum of the US EPA proposed 16 priority PAHs, excluding naphthalene and pyrene) ranged from 473.9 to 2289 ng g(-1) with a slow increasing stage in the deeper sediments and a sharp increasing stage in the upper sediments. The input rate of TPAHs, especially that of PAH(9) (the sum of fluoranthene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, dibenzo(ah)anthrathene, and benzo(ghi)perylene), correlated well to the Chinese historical socioeconomic data. This indicates that sediment PAHs were mainly derived from human activities and PAH(9) can be regarded as a better indicator of the local socioeconomic development. Source identification suggested that PAHs were originated primarily from mixed sources (e.g., coal and biomass burning and petroleum combustion), except for perylene which was mostly of diagenetic origin. In addition, the down-core PAHs profile clearly illustrated that PAHs sources in Northeast China experienced a transformation from low- and moderate temperature to high-temperature combustion processes, especially after the late 1980s. Additionally, an ecological risk assessment using two redefined biological thresholds (TEQ(ERL) and TEQ(ERM)) indicated that most of the PAHs measured in the present sediment core would not cause an immediate toxic effect; only FLU and PHEN are a potential source of concern for biological impairment.

  19. The organic carbon isotope of lacustrine sediments of the Upper Shahejie formation in Huanghua Depression: a record of sedimentary environment and productivity of an ancient lake

    International Nuclear Information System (INIS)

    Fei, Weiwei; Huang, Xiaoyan; Dai, Na; Zhong, Ningning

    2013-01-01

    -rich lamellae is the result of algae blooming and deposition in ancient lakes, as carbonate lamellae is the result of CaCO_3 saturation precipitation with CO_2 decreasing in surface water due to the algal blooming. Lamellar deposition pattern of the mudstone recorded the geological process of algae’s blooming, death and burial. (2) The carbon isotopic composition of organic matter can be a sensitive indicator of the relative significance of bioproductivity and redox conditions as the main factor controlling the formation of organic-rich sediments. δ"1"3C_o_r_g shows a positive correlation with TOC when bioproductivity dominated, however, a negative correlation when redox conditions dominated (Harris et al., 2004). The study on biomarker shows pristane/phytane ratios nearly constant throughout the interval, suggesting the redox environments remained stable. The negative correlation between pristane/phytane ratios and TOC is not obvious, whereas δ"1"3C_o_r_g shows a good positive correlation to TOC%, adjusted R is 0.89. Thus it can be seen that bioproductivity exerted a significant control on organic carbon accumulation in the upper of Shahejie Formation.

  20. 21,000 years of Ethiopian African monsoon variability recorded in sediments of the western Nile deep-sea fan: impact of the Nile freshwater inflow for the Mediterranean thermo-haline circulation

    Science.gov (United States)

    Revel, Marie; Colin, Christophe; Bernasconi, Stephano; Combourieu-Nebout, Nathalie; Ducassou, Emmanuelle; Rolland, Yann; Bosch, Delphine

    2014-05-01

    The Nile delta sedimentation constitutes a continuous high resolution (1.6 mm/year) record of Ethiopian African monsoon regime intensity. Multiproxy analyses performed on core MS27PT recovered in hemipelagic Nile sediment margin (Blue/White Nile River suspended matter frequency fluctuations during the last 21 cal. ka BP. The radiogenic Sr and Nd isotopes, clay mineralogy, bulk elemental composition and palynological analyses reveal large changes in source components, oscillating between a dominant aeolian Saharan contribution during the LGM and the Late Holocene (~4 to 2 cal. ka BP), a dominant Blue/Atbara Nile River contribution during the early Holocene (15 to 8.4 cal. ka BP) and a probable White Nile River contribution during the Middle Holocene (8.4 to 4 cal. ka BP). The following main features are highlighted: 1. The rapid shift from the LGM arid conditions to the African Humid Period (AHP) started at about 15 cal. ka BP. AHP extends until 8.4 cal. ka BP, and we suggest that the Ethiopian African Monsoon maximum between 12 and 8 cal. ka BP is responsible for a larger Blue/Atbara Nile sediment load and freshwater input into the Eastern Mediterranean Sea. 2. The transition between the AHP and the arid Late Holocene is gradual and occurs in two main phases between 8.4 and 6.5 cal. ka BP and 6.5 to 3.2 cal. ka BP. We suggest that the main rain belt shifted southward from 8.4 to ~4 cal. ka BP and was responsible for progressively reduced sediment load and freshwater input into the eastern Mediterranean Sea. 3. The aridification along the Nile catchments occurred from ~4 to 2 cal. ka BP. A dry period, which culminates at 3.2 cal. ka BP, and seems to coincide with a re-establishment of increased oceanic primary productivity in the western Mediterranean Sea. We postulate that the decrease in thermo-haline water Mediterranean circulation could be part of a response to huge volumes of fresh-water delivered principally by the Nile River from 12 to 8.4 cal. ka BP in the

  1. Comparing records with related chronologies

    Science.gov (United States)

    Bronk Ramsey, Christopher; Albert, Paul; Kearney, Rebecca; Staff, Richard A.

    2016-04-01

    In order to integrate ice, terrestrial and marine records, it is necessary to deal with records on different timescales. These timescales can be grouped into those that use a common fundamental chronometer (such as Uranium-Thorium dating or Radiocarbon) and can also be related to one another where we have chronological tie points such as tephra horizons. More generally we can, through a number of different methodologies, derive relationships between different timescales. A good example of this is the use of cosmogenic isotope production, specifically 10Be and 14C to relate the calibrated radiocarbon timescale to that of the Greenland ice cores. The relationships between different timescales can be mathematically expressed in terms of time-transfer functions. This formalism allows any related record to be considered against any linked timescale with an appropriate associated uncertainty. The prototype INTIMATE chronological database allows records to be viewed and compared in this way and this is now being further developed, both to include a wider range of records and also to provide better connectivity to other databases and chronological tools. These developments will also include new ways to use tephra tie-points to constrain the relationship between timescales directly, without needing to remodel each associated timescale. The database as it stands allows data for particular timeframes to be recalled and plotted against any timescale, or exported in spreadsheet format. New functionality will be added to allow users to work with their own data in a private space and then to publish it when it has been through the peer-review publication process. In order to make the data easier to use for other further analysis and plotting, and with data from other sources, the database will also act as a server to deliver data in a JSON format. The aim of this work is to make the comparison of integrated data much easier for researchers and to ensure that good practice in

  2. The Chew Bahir Drilling Project (HSPDP). Deciphering climate information from the Chew Bahir sediment cores: Towards a continuous half-million year climate record near the Omo - Turkana key palaeonanthropological Site

    Science.gov (United States)

    Foerster, Verena E.; Asrat, Asfawossen; Chapot, Melissa S.; Cohen, Andrew S.; Dean, Jonathan R.; Deino, Alan; Günter, Christina; Junginger, Annett; Lamb, Henry F.; Leng, Melanie J.; Roberts, Helen M.; Schaebitz, Frank; Trauth, Martin H.

    2017-04-01

    As a contribution towards an enhanced understanding of human-climate interactions, the Hominin Sites and Paleolakes Drilling Project (HSPDP) has successfully completed coring five dominantly lacustrine archives of climate change during the last 3.5 Ma in East Africa. All five sites in Ethiopia and Kenya are adjacent to key paleoanthropological research areas encompassing diverse milestones in human evolution, dispersal episodes, and technological innovation. The 280 m-long Chew Bahir sediment records, recovered from a tectonically-bound basin in the southern Ethiopian rift in late 2014, cover the past 550 ka of environmental history, a time period that includes the transition to the Middle Stone Age, and the origin and dispersal of modern Homo sapiens. Deciphering climate information from lake sediments is challenging, due to the complex relationship between climate parameters and sediment composition. We will present the first results in our efforts to develop a reliable climate-proxy tool box for Chew Bahir by deconvolving the relationship between sedimentological and geochemical sediment composition and strongly climate-controlled processes in the basin, such as incongruent weathering, transportation and authigenic mineral alteration. Combining our first results from the long cores with those from a pilot study of short cores taken in 2009/10 along a NW-SE transect of the basin, we have developed a hypothesis linking climate forcing and paleoenvironmental signal-formation processes in the basin. X-ray diffraction analysis of the first sample sets from the long Chew Bahir record reveals similar processes that have been recognized for the uppermost 20 m during the pilot-study of the project: the diagenetic illitization of smectites during episodes of higher alkalinity and salinity in the closed-basin lake induced by a drier climate. The precise time resolution, largely continuous record and (eventually) a detailed understanding of site specific proxy formation

  3. Holocene environmental change along the southern Cape coast of South Africa - Insights from the Eilandvlei sediment record spanning the last 8.9 kyr

    Science.gov (United States)

    Wündsch, Michael; Haberzettl, Torsten; Cawthra, Hayley C.; Kirsten, Kelly L.; Quick, Lynne J.; Zabel, Matthias; Frenzel, Peter; Hahn, Annette; Baade, Jussi; Daut, Gerhard; Kasper, Thomas; Meadows, Michael E.; Mäusbacher, Roland

    2018-04-01

    This study investigates Holocene sediments from Eilandvlei, a coastal lake located within the Wilderness embayment at the southern Cape coast of South Africa. The evolution of the present estuarine/coastal lake system is reconstructed based on seismic data as well as a multi-proxy approach on a 30.5 m sediment core spanning the last 8.9 kyr. Geochemical (Ca, TOC/S, Br/TOC) and micropalaeontological data (diatoms, foraminifera) reflect changes in the degree of marine influence at the core site. The embayment likely developed via distinct phases of connectivity to the Indian Ocean caused by sea level changes and dune progradation. Marine conditions prevailed at the core site from 8900 to 4700 cal BP. The rapid sea level rise during the early Holocene caused the inundation of a palaeovalley that most likely had formed at lower sea levels during the Pleistocene. Towards the mid-Holocene the sea level exceeded its present height around 7500 cal BP creating a marine embayment. At 4700 cal BP, the embayment became distinctly more disconnected from the ocean turning into a lagoon system that persisted until 1200 cal BP. Subsequently, the marine influence further decreased and the present estuarine/coastal lake system was established. Grain size and geochemical data (Fe, Si/Al, chemical index of alteration (CIA)) further reflect changes in the deposition of terrigenous sediments at the core site. While the sedimentation of fine-grained (climatic conditions than today from 8900 to 7900 cal BP and 6400 to 3000 cal BP. In contrast, the periods between 7900-6400 cal BP and 3000 cal BP-present were likely characterized by high river discharge and thus, generally more rainfall. The reconstructed palaeoclimatic variations are discussed within the context of e.g., shifts in the position of the Antarctic sea ice extent and the mid-latitude westerly wind belt as well as changes in the El Niño-Southern Oscillation (ENSO).

  4. Tephrostratigraphy and Provenance From IODP Expedition 352, Izu-Bonin Arc: Tracing Tephra Sources and Volumes From the Oligocene to Recent

    Science.gov (United States)

    Kutterolf, S.; Schindlbeck, J. C.; Robertson, A. H. F.; Avery, A.; Baxter, A. T.; Petronotis, K.; Wang, K.-L.

    2018-01-01

    Provenance studies of widely distributed tephras, integrated within a well-defined temporal framework, are important to deduce systematic changes in the source, scale, distribution, and changes in regional explosive volcanism. Here, we establish a robust tephrochronostratigraphy for a total of 157 marine tephra layers collected during IODP Expedition 352. We infer at least three major phases of highly explosive volcanism during Oligocene to Pleistocene time. Provenance analysis based on glass composition assigns 56 of the tephras to a Japan source, including correlations with 12 major and widespread tephra layers resulting from individual eruptions in Kyushu, Central Japan, and North Japan between 115 ka and 3.5 Ma. The remaining 101 tephras are assigned to four source regions along the Izu-Bonin arc. One, exclusively assigned to the Oligocene age, is proximal to the Bonin Ridge islands; two reflect eruptions within the volcanic front and back-arc of the central Izu-Bonin arc, and a fourth region corresponds to the Northern Izu-Bonin arc source. First-order volume estimates imply eruptive magnitudes ranging from 6.3 to 7.6 for Japan-related eruptions and between 5.5 and 6.5 for IBM eruptions. Our results suggest tephras between 30 and 22 Ma reflect a subtly different Izu-Bonin chemical signature compared to the recent arc. After a ˜9 Ma gap in eruption, tephra supply from the Izu-Bonin arc predominated from 15 to 5 Ma, and finally a subequal mixture of tephra sources from the (palaeo)Honshu and Izu-Bonin arcs occured within the last ˜5 Ma.

  5. The lacustrine sediment record of Oberwinkler Maar (Eifel, Germany): Chironomid and macro-remain-based inferences of environmental changes during Oxygen Isotope Stage 3

    NARCIS (Netherlands)

    Engels, S.; Bohncke, S.J.P.; Heiri, O.; Schaber, K.; Sirocko, F.

    2008-01-01

    The lacustrine record of Oberwinkler Maar (Eifel, Germany) is the northernmost continuous record documenting the Weichselian Pleniglacial in central Europe - a period characterized by multiple abrupt climate oscillations known as the Dansgaard/Oeschger cycles. Here, the results of a high-resolution

  6. Palynological record of tropical rain forest vegetation and sea level fluctuations since 140 ka from sediment core, south-eastern Arabian sea.

    Digital Repository Service at National Institute of Oceanography (India)

    Farooqui, A.; Pattan, J.N.; Parthiban, G.; Srivastava, J.; Ranjana

    of rain forest “plant refugia” on land. Neogene rain forest flora recorded earlier from the Varkala Formation and the present record of its existence since MIS-6 in the region provide an understanding that the monsoon circulation over southern India...

  7. Geothermal flux through palagonitized tephra, Surtsey, Iceland - The Surtsey temperature-data-relay experiment via Landsat-1

    Science.gov (United States)

    Friedman, J. D.; Preble, D. M.; Jakobsson, S.

    1976-01-01

    The net geothermal flux through palagonitized basaltic tephra rims of the Surtur I and Surtur II craters at Surtsey, Iceland, in 1972, is estimated at 780 plus or minus 325 microcal/sq cm/s, indicating a decline since 1969 when a flux of 1500 microcal/sq cm/s was estimated. Heat flux in this range characterizes the postvolcanic environment on Surtsey in which the subaerial polagonitization of basaltic tephra is associated with mass transfer of hydrothermal vapor, either of meteoric or sea-water origin, only a few years after cessation of eruptive activity. The flux estimation is the result of the Surtsey data-relay experiment via Landsat-1 which was carried out in several phases. Temperature data were transmitted for a 38-day period in November and December 1972. A near-surface vertical gradient of 69.4 C/m was obtained, suggesting a mixed mechanism of heat transfer, partitioned between conduction and convection.

  8. A 100-year record of climate change and human activities inferred from the geochemical composition of sediments in Chaiwopu Lake, arid northwest China

    Directory of Open Access Journals (Sweden)

    Wen Liu

    2016-01-01

    Full Text Available An 81-cm sediment core from Chaiwopu Lake in arid northwest China was analyzed for 137Cs activity and concentrations of major and trace elements. We used these data to discriminate between the influence of climate change and human activities on the geochemical change of the lake sediments over the past century. Elements Al, K, Ba, Ti, V, Fe, Ni, Mn, Li, and Be were mainly from detrital. Ca, Sr, and Mg concentrations were controlled by chemical weathering processes. Na came mainly from salt precipitation caused by a decline in water level. Enrichment factors for Pb and P in recent deposits are large, indicating they were influenced by human activies. Geochemical conditions during the past century can be divided into three stages: i From ca. 1900 to the1950s element concentrations varied widely and frequently. In general, concentrations of typical mobile elements Ca, Sr, and Mg stay relatively high whereas values for other elements remained relatively low. This was interpreted to reflect variable climate under conditions of weak surface erosion intensity. ii From the 1950s to the early 2000s, element concentrations display less variability. The Al, K, Ba, Ti, P, Cr, V, Fe, Ni, Mn, Co, Cu, Li, Zn, Be, Pb, and Na contents were generally higher, whereas contents of Ca, Sr, and Mg were on average lower. This indicates that the regional environment was conducive to surface erosion. Enrichment of trace metals and major elements in the sediment reflects enhanced human activities. iii In the last decade, Pb and P exhibited a great increase, possibly associated with the input from fossil fuel combustion, sewage discharge and non-point-source pollution in the watershed. The lake volume decreased substantially because of groundwater extraction for municipal water, which resulted in a marked increase in salinity and enhanced Na precipitation.

  9. A 60-year record of 129I in Taal Lake sediments (Philippines): Influence of human nuclear activities at low latitude regions.

    Science.gov (United States)

    Zhang, Luyuan; Hou, Xiaolin; Li, Hong-Chun; Xu, Xiaomei

    2018-02-01

    The influence of human nuclear activities on environmental radioactivity is not well known at low latitude regions that are distant from nuclear test sites and nuclear facilities. A sediment core collected from Taal Lake in the central Philippines was analyzed for 129 I and 127 I to investigate this influence in a low-latitude terrestrial system. A baseline of 129 I/ 127 I atomic ratios was established at (2.04-5.14) × 10 -12 in the pre-nuclear era in this region. Controlled by the northeasterly equatorial trade winds, increased 129 I/ 127 I ratios of (20.1-69.3) × 10 -12 suggest that atmospheric nuclear weapons tests at the Pacific Proving Grounds in the central Pacific Ocean was the major source of 129 I in the sediment during 1956-1962. The 129 I/ 127 I ratios, up to 157.5 × 10 -12 after 1964, indicate a strong influence by European nuclear fuel reprocessing plants. The East Asian Winter Monsoon is found to be the dominant driving force in the atmospheric dispersion of radioactive iodine ( 129 I) from the European nuclear fuel reprocessing plants to Southeast Asia, which is also important for dispersion of other airborne pollutants from the middle-high to low latitude regions. A significant 129 I/ 127 I peak at 42.8 cm in the Taal Lake core appears to be the signal of the Chernobyl accident in 1986. In addition, volcanic activities are reflected in the iodine isotope profiles in the sediment core, suggesting the potential of using iodine isotopes as an indicator of volcanic eruptions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Spores of coprophilous fungi from under the Dawson tephra (25,300 14C years BP), Yukon Territory, northwestern Canada

    NARCIS (Netherlands)

    van Geel, B.; Zazula, G.D.; Schweger, C.E.

    2007-01-01

    Based on the analysis of pollen and macrofossils Zazula et al. [Zazula, G.D., Froesne, D.G., Elias, S.A., Kuzmina, S., la Farge, C., Reyes, A.V., Sanborn, P.T., Schweger, C.E., Smith, C.A.S., Mathewes, R.W., 2006. Vegetation buried under Dawson tephra (25,300 14C yr BP) and locally diverse late

  11. New accelerator mass spectrometry radiocarbon ages for the Mazama tephra layer from Kootenay National Park, British Columbia, Canada

    International Nuclear Information System (INIS)

    Hallett, D.J.; Hills, L.V.; Clague, J.J.

    1997-01-01

    Charcoal fragments recovered from the Mazama air-fall tephra layer in cores from Dog and Cobb lakes, Kootenay National Park, British Columbia, yielded accelerator mass spectrometry ages of 6720 ± 70 and 6760 ± 70 14 C years BP, respectively. These two new ages, together with other previously published radiocarbon ages on charcoal and twig fragments from Mazama air-fall deposits, indicate that the climatic eruption of Mount Mazama occurred 6730 ± 40 14 C years BP. (author)

  12. Holocene tephra-fall deposits of southern and austral Andes volcanic zones (33-54oS): eruption recurrence

    International Nuclear Information System (INIS)

    Naranjo, J.A.; Polanco, E.; Lara, L; Moreno, H; Stern, C.R

    2001-01-01

    Radiometric 14 C dating is a very useful tool to study the chronostratigraphy of pyroclastic deposits. In addition, 14 C ages are essential parameters for the estimation of the recurrence time of the explosive volcanic activity. The origin, distribution and relative age of mappable Holocene tephra-fall deposits of the Southern Andes Volcanic Zone (SVZ) and Austral Andes Volcanic Zone (AVZ) from 33 o S-54 o S, were studied and their recurrence period is analysed (au)

  13. The Geomagnetic Field Recorded in Sediments of the Tuzla Section (the Krasnodar Territory, Russia) over the Time Interval 120-70 ka

    DEFF Research Database (Denmark)

    Pilipenko, Olga; Abrahamsen, N.; Trubikhin, V. M.

    2007-01-01

    Petro- and paleomagnetic methods are applied to the study of the lower part of the Early Pleistocene Tuzla section on the Black Sea coast of the Taman Peninsula. This part of the section is composed of marine and lagoonal sediments deposited over the time interval 120-70 ka. The measured curves...... of the variation in the geomagnetic field inclination reveal an anomalous direction dated at ~110 ka which coincides with a similar anomalous direction in the Eltigen section (Ukraine) correlating with the Blake paleomagnetic event. The significant correlation between the time series NRM0.015/SIRM0.015 (Tuzla...

  14. Sphaerodoropsis kitazatoi, a new species and the first record of Sphaerodoridae (Annelida: Phyllodocida) in SW Atlantic abyssal sediments around a whale carcass

    Science.gov (United States)

    Shimabukuro, Maurício; Rizzo, Alexandra E.; Alfaro-Lucas, Joan M.; Fujiwara, Yoshihiro; Sumida, Paulo Y. G.

    2017-12-01

    A new polychaete species, Sphaerodoropsis kitazatoi (Annelida: Phyllodocida: Sphaerodoridae), is described from the abyssal Southwest Atlantic Ocean at the base of São Paulo Ridge (4204 m depth). This species was found in sediments impacted by a whale carcass. The new species has four longitudinal rows of macrotubercles and one transversal row per chaetiger and shares several characters with S. anae Aguado and Rouse, 2006 that is also associated with chemosynthetic environments. They can be clearly distinguished from S. anae and other Sphaerodoropsis species by the arrangement and the number of prostomial, body and parapodial papillae.

  15. A high-resolution paleosecular variation record from Black Sea sediments indicating fast directional changes associated with low field intensities during marine isotope stage (MIS) 4

    Science.gov (United States)

    Nowaczyk, Norbert R.; Jiabo, Liu; Frank, Ute; Arz, Helge W.

    2018-02-01

    A total of nine sediment cores recovered from the Archangelsky Ridge in the SE Black Sea were systematically subjected to intense paleo- and mineral magnetic analyses. Besides 16 accelerator mass spectrometry (AMS) 14C ages available for another core from this area, dating was accomplished by correlation of short-term warming events during the last glacial monitored by high-resolution X-ray fluorescence (XRF) scanning as maxima in both Ca/Ti and K/Ti ratios in Black Sea sediments to the so-called 'Dansgaard-Oeschger events' recognized from Greenland ice cores. Thus, several hiatuses could be identified in the various cores during the last glacial/interglacial cycle. Finally, core sections documenting marine isotope stage (MIS) 4 at high resolution back to 69 ka were selected for detailed analyses. At 64.5 ka, according to obtained results from Black Sea sediments, the second deepest minimum in relative paleointensity during the past 69 ka occurred, with the Laschamp geomagnetic excursion at 41 ka being associated with the lowest field intensities. The field minimum during MIS 4 is associated with large declination swings beginning about 3 ka before the minimum. While a swing to 50°E is associated with steep inclinations (50-60°) according to the coring site at 42°N, the subsequent declination swing to 30°W is associated with shallow inclinations of down to 40°. Nevertheless, these large deviations from the direction of a geocentric axial dipole field (I = 61 °, D = 0 °) still can not yet be termed as 'excursional', since latitudes of corresponding virtual geomagnetic poles (VGP) only reach down to 51.5°N (120°E) and 61.5°N (75°W), respectively. However, these VGP positions at opposite sides of the globe are linked with VGP drift rates of up to 0.2° per year in between. These extreme secular variations might be the mid-latitude expression of a geomagnetic excursion with partly reversed inclinations found at several sites much further North in Arctic

  16. A Tephra Database With an Intelligent Correlation System, Mono-Inyo Volcanic Chain, CA

    Science.gov (United States)

    Bursik, M.; Rogova, G.

    2004-12-01

    We are assembling a web-accessible, relational database of information on past eruptions of the Mono-Inyo volcanic chain, eastern California. The PostgreSQL database structure follows the North American Data Model and CordLink. The database allows us to extract the features diagnostic of particular pyroclastic layers, as well as lava domes and flows. The features include depth in the section, layer thickness and internal stratigraphy, mineral assemblage, major and trace element composition, tephra componentry and granulometry, and radiocarbon age. Our working hypotheses are that 1) the database will prove useful for unraveling the complex recent volcanic history of the Mono-Inyo chain 2) aided by the use of an intelligent correlation system integrated into the database system. The Mono-Inyo chain consists of domes, craters and flows that stretch for 50 km north-south, subparallel to the Sierran range front fault system. Almost all eruptions within the chain probably occurred less than 50,000 years ago. Because of the variety of magma and eruption types, and the migration of source regions in time and space, it is nontrivial to discern patterns of behaviour. We have explored the use of multiple artificial neural networks combined within the framework of the Dempster-Shafer theory of evidence to construct a hybrid information processing system as an aid in the correlation of Mono-Inyo pyroclastic layers. It is hoped that such a system could provide information useful to discerning eruptive patterns that would otherwise be difficult to sort and categorize. In a test case on tephra layers at known sites, the intelligent correlation system was able to categorize observations correctly 96% of the time. In a test case with layers at one unknown site, and using a pairwise comparison of the unknown site with the known sites, a one-to-one correlation between the unknown site and the known sites was found to sometimes be poor. Such a result could be used to aid a

  17. Probabilistic short-term volcanic hazard in phases of unrest: A case study for tephra fallout

    Science.gov (United States)

    Selva, Jacopo; Costa, Antonio; Sandri, Laura; Macedonio, Giovanni; Marzocchi, Warner

    2014-12-01

    During volcanic crises, volcanologists estimate the impact of possible imminent eruptions usually through deterministic modeling of the effects of one or a few preestablished scenarios. Despite such an approach may bring an important information to the decision makers, the sole use of deterministic scenarios does not allow scientists to properly take into consideration all uncertainties, and it cannot be used to assess quantitatively the risk because the latter unavoidably requires a probabilistic approach. We present a model based on the concept of Bayesian event tree (hereinafter named BET_VH_ST, standing for Bayesian event tree for short-term volcanic hazard), for short-term near-real-time probabilistic volcanic hazard analysis formulated for any potential hazardous phenomenon accompanying an eruption. The specific goal of BET_VH_ST is to produce a quantitative assessment of the probability of exceedance of any potential level of intensity for a given volcanic hazard due to eruptions within restricted time windows (hours to days) in any area surrounding the volcano, accounting for all natural and epistemic uncertainties. BET_VH_ST properly assesses the conditional probability at each level of the event tree accounting for any relevant information derived from the monitoring system, theoretical models, and the past history of the volcano, propagating any relevant epistemic uncertainty underlying these assessments. As an application example of the model, we apply BET_VH_ST to assess short-term volcanic hazard related to tephra loading during Major Emergency Simulation Exercise, a major exercise at Mount Vesuvius that took place from 19 to 23 October 2006, consisting in a blind simulation of Vesuvius reactivation, from the early warning phase up to the final eruption, including the evacuation of a sample of about 2000 people from the area at risk. The results show that BET_VH_ST is able to produce short-term forecasts of the impact of tephra fall during a rapidly

  18. The effect of wind and eruption source parameter variations on tephra fallout hazard assessment: an example from Vesuvio (Italy)

    Science.gov (United States)

    Macedonio, Giovanni; Costa, Antonio; Scollo, Simona; Neri, Augusto

    2015-04-01

    Uncertainty in the tephra fallout hazard assessment may depend on different meteorological datasets and eruptive source parameters used in the modelling. We present a statistical study to analyze this uncertainty in the case of a sub-Plinian eruption of Vesuvius of VEI = 4, column height of 18 km and total erupted mass of 5 × 1011 kg. The hazard assessment for tephra fallout is performed using the advection-diffusion model Hazmap. Firstly, we analyze statistically different meteorological datasets: i) from the daily atmospheric soundings of the stations located in Brindisi (Italy) between 1962 and 1976 and between 1996 and 2012, and in Pratica di Mare (Rome, Italy) between 1996 and 2012; ii) from numerical weather prediction models of the National Oceanic and Atmospheric Administration and of the European Centre for Medium-Range Weather Forecasts. Furthermore, we modify the total mass, the total grain-size distribution, the eruption column height, and the diffusion coefficient. Then, we quantify the impact that different datasets and model input parameters have on the probability maps. Results shows that the parameter that mostly affects the tephra fallout probability maps, keeping constant the total mass, is the particle terminal settling velocity, which is a function of the total grain-size distribution, particle density and shape. Differently, the evaluation of the hazard assessment weakly depends on the use of different meteorological datasets, column height and diffusion coefficient.

  19. A 15,400-year record of environmental magnetic variations in sub-alpine lake sediments from the western Nanling Mountains in South China: Implications for palaeoenvironmental changes

    Science.gov (United States)

    Zhong, Wei; Wei, Zhiqiang; Shang, Shentan; Ye, Susu; Tang, Xiaowen; Zhu, Chan; Xue, Jibin; Ouyang, Jun; Smol, John P.

    2018-04-01

    A detailed environmental magnetic investigation has been performed on a sub-alpine sedimentary succession deposited over the past 15,400 years in Daping Swamp in the western Nanling Mountains of South China. Magnetic parameters reveal that fine grains of pseudo-single domain (PSD) magnetite or titanomagnetite are the dominant magnetic minerals in the lake sediments and surface soils collected from the catchment, which suggests that magnetic minerals in lake sediments mainly originated from surface soil erosion of the catchment. Variation of surface runoff caused by rainfall is interpreted as the main process for transportation of weathered soils into the lake. In the Last Deglacial period (LGP, 15,400-11,500 cal a BP), the influx of magnetic minerals of detrital material may have been significantly affected by the severe dry and cold conditions of the Last Glacial Maximum. Stabilised conditions of the catchment associated with increased vegetation coverage (e.g., 8000-4500 and 2500-1000 cal a BP) limited the input of magnetic minerals. Intensive soil erosion caused by increased human activity may have given rise to abnormal increases in multiple magnetic parameters after 1000 cal a BP. Because changes in runoff and vegetation coverage are closely related to Asian summer monsoon (ASM) intensity, the sedimentary magnetism of Daping Swamp provides another source of information to investigate the evolution of the ASM.

  20. Records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated AUV and ROV data, offshore Palos Verdes, southern California Borderland

    Science.gov (United States)

    Maier, Katherine L.; Brothers, Daniel; Paull, Charles K.; McGann, Mary; Caress, David W.; Conrad, James E.

    2016-01-01

    Variations in seabed gradient are widely acknowledged to influence deep-water deposition, but are often difficult to measure in sufficient detail from both modern and ancient examples. On the continental slope offshore Los Angeles, California, autonomous underwater vehicle, remotely operated vehicle, and shipboard methods were used to collect a dense grid of high-resolution multibeam bathymetry, chirp sub-bottom profiles, and targeted sediment core samples that demonstrate the influence of seafloor gradient on sediment accumulation, depositional environment, grain size of deposits, and seafloor morphology. In this setting, restraining and releasing bends along the active right-lateral Palos Verdes Fault create and maintain variations in seafloor gradient. Holocene down-slope flows appear to have been generated by slope failure, primarily on the uppermost slope (~ 100–200 m water depth). Turbidity currents created a low relief (water depositional systems. These results help to bridge gaps in scale between existing deep-sea and experimental datasets and may provide constraints for future numerical modeling studies.

  1. Stable lead isotopic characterisation of the historical record of environmental lead contamination in dated freshwater lake sediment cores from northern and central Scotland

    Energy Technology Data Exchange (ETDEWEB)

    Eades, L.J.; Farmer, J.G. [Environmental Chemistry Unit, Department of Chemistry, University of Edinburgh, West Mains Road, EH9 3JJ, Scotland Edinburgh (United Kingdom); MacKenzie, A.B. [Scottish Universities Research and Reactor Centre, East Kilbride, G75 0QF, Scotland Glasgow (United Kingdom); Kirika, A.; Bailey-Watts, A.E. [NERC Centre for Ecology and Hydrology, EH26 0QB, Scotland Penicuik (United Kingdom)

    2002-06-20

    Sediment cores from three Scottish freshwater lakes, Loch Ness in the remote north and Loch Lomond and the Lake of Menteith, much closer to the heavily populated and industrialised central belt, were analysed for 210Pb, 137Cs, Pb and stable Pb isotopic composition (206Pb/207Pb). The radionuclide data were used to establish chronologies for the Loch Ness and Loch Lomond cores, but a chronology could not be developed for the Lake of Menteith core, in which the surface sediment had been subject to intense mixing. Although Pb concentrations generally started increasing during the mid-17th Century, a small peak occurred for Loch Ness in the early 16th Century, perhaps attributable to the influence of medieval mining and smelting in mainland Europe. Temporal trends in the pattern of Pb accumulation were similar for Loch Ness and both sites in Loch Lomond, with 40-50% of the anthropogenic Pb deposited prior to the 20th Century. Fluxes of anthropogenic Pb to the lake sediments peaked during the 1950s at all locations where chronologies could be established. The 5-fold increase in anthropogenic Pb inventory for the southern basin of Loch Lomond relative to Loch Ness reflected geographical proximity to the main polluting sources. The 206Pb/207Pb data for anthropogenic Pb in the sediments from Loch Ness and Loch Lomond exhibited largely similar trends related to five different time periods. Pre-1820, the 206Pb/207Pb ratio was close to that for coal (1.181). From 1820 to 1900, a fairly constant 206Pb/207Pb ratio of 1.17 probably resulted from a combination of emissions from the smelting of indigenous Pb ore (1.170) and coal burning (1.181) in Scotland, and industrial activity to the south in England, where Australian Pb of characteristically low 206Pb/207Pb ratio (1.04) was already in use. From 1901 to 1930, the 206Pb/207Pb ratio declined by <0.01, due to the increasing influence of Australian Pb. From 1931 to 1975/1985, the 206Pb/207Pb ratio of anthropogenic Pb declined by a

  2. Stable lead isotopic characterisation of the historical record of environmental lead contamination in dated freshwater lake sediment cores from northern and central Scotland.

    Science.gov (United States)

    Eades, L J; Farmer, J G; MacKenzie, A B; Kirika, A; Bailey-Watts, A E

    2002-06-20

    Sediment cores from three Scottish freshwater lakes, Loch Ness in the remote north and Loch Lomond and the Lake of Menteith, much closer to the heavily populated and industrialised central belt were analysed for 210Pb, 137Cs, Pb and stable Pb isotopic composition (206Pb/207Pb). The radionuclide data were used to establish chronologies for the Loch Ness and Loch Lomond cores, but a chronology could not be developed for the Lake of Menteith core, in which the surface sediment had been subject to intense mixing. Although Pb concentrations generally started increasing during the mid-17th Century, a small peak occurred for Loch Ness in the early 16th Century, perhaps attributable to the influence of medieval mining and smelting in mainland Europe. Temporal trends in the pattern of Pb accumulation were similar for Loch Ness and both sites in Loch Lomond, with 40-50% of the anthropogenic Pb deposited prior to the 20th Century. Fluxes of anthropogenic Pb to the lake sediments peaked during the 1950s at all locations where chronologies could be established. The 5-fold increase in anthropogenic Pb inventory for the southern basin of Loch Lomond relative to Loch Ness reflected geographical proximity to the main polluting sources. The 206Pb/207Pb data for anthropogenic Pb in the sediments from Loch Ness and Loch Lomond exhibited largely similar trends related to five different time periods. Pre-1820, the 206Pb/207Pb ratio was close to that for coal (1.181). From 1820 to 1900, a fairly constant 206Pb/207Pb ratio of approximately 1.17 probably resulted from a combination of emissions from the smelting of indigenous Pb ore (1.170) and coal burning (1.181) in Scotland, and industrial activity to the south in England, where Australian Pb of characteristically low 206Pb/207Pb ratio (1.04) was already in use. From 1901 to 1930, the 206Pb/207Pb ratio declined by <0.01, due to the increasing influence of Australian Pb. From 1931 to 1975/1985, the 206Pb/207Pb ratio of anthropogenic Pb

  3. Inferring the effects of compositional boundary layers on crystal nucleation, growth textures, and mineral chemistry in natural volcanic tephras through submicron-resolution imaging

    Directory of Open Access Journals (Sweden)

    Georg F. Zellmer

    2016-09-01

    Full Text Available Crystal nucleation and growth are first order processes captured in volcanic rocks and record important information about the rates of magmatic processes and chemical evolution of magmas during their ascent and eruption. We have studied glass-rich andesitic tephras from the Central Plateau of the Southern Taupo Volcanic Zone by electron- and ion-microbeam imaging techniques to investigate down to sub-micrometre scale the potential effects of compositional boundary layers (CBLs of melt around crystals on the nucleation and growth of mineral phases and the chemistry of crystal growth zones. We find that CBLs may influence the types of mineral phases nucleating and growing, and growth textures such as the development of swallowtails. The chemistry of the CBLs also has the capacity to trigger intermittent overgrowths of nanometre-scale bands of different phases in rapidly growing crystals, resulting in what we refer to as cryptic phase zoning. The existence of cryptic phase zoning has implications for the interpretation of microprobe compositional data, and the resulting inferences made on the conditions of magmatic evolution. Identification of cryptic phase zoning may in future lead to more accurate thermobarometric estimates and thus geospeedometric constraints. In future, a more quantitative characterization of CBL formation and its effects on crystal nucleation and growth may contribute to a better understanding of melt rheology and magma ascent processes at the onset of explosive volcanic eruptions, and will likely be of benefit to hazard mitigation efforts.

  4. Changes in Mass Flux of Tephra from the Lava Lake in Overlook Crater, Kīlauea Volcano, Hawai`i

    Science.gov (United States)

    Swanson, D. A.; Orr, T. R.; Patrick, M. R.

    2016-12-01

    The mass flux of tephra (mostly Pele's hair and tears, hollow spherules, and lithic clasts) from the lava lake in Overlook crater varies on short (seconds-minutes), intermediate (hours-days), and long (months) time scales. The tephra is collected almost daily from a network of 10 buckets within 400 m of, and 100-150 m above, the lava lake; bucket locations have not changed during the eruption. A mass accumulation rate (AR) is calculated for the network; since April 2008, the AR averages 0.17 g/m2/h ( 5×10-8 kg/m2/s). The tephra forms during almost constant spattering at the SE sink (the main downwelling site) and ephemeral sites along the crater wall, as well as from sporadic, rockfall-induced violent outgassing that can eject decimeter-size spatter clots onto the crater rim; the average AR excludes these violent events. The rockfalls, and nearly constant raveling from the crater wall, introduce lithic clasts into the tephra. The lithic content of the tephra has decreased with time, reflecting both greater wall stability and higher lake level, and was usually 7 m/s). At intermediate and long time scales, juvenile AR shows no correlation with measured SO2 output and only weak or no correlation with wind speed, but it often tracks the elevation of the lake surface—higher when lava is nearer the buckets. For example, both lava level and juvenile AR were unusually high in January-July 2016. Before 2016, however, 7-9 periods of heightened juvenile production (see figure below), each lasting several months, show no correlation with other monitored parameters—lake level, SO2, wind speed and direction, or downwelling location. Often AR gradually increased to a peak before falling off, sometimes to nearly zero. We speculate that such long-term variations result from changes in magma supply rate, gas concentration, or rise frequency of decoupled gas slugs. These changes may be too small or slow to detect by current geodetic and gas monitoring. They suggest a slowly

  5. Remarkably preserved tephra from the 3430 Ma Strelley Pool Formation, Western Australia: Implications for the interpretation of Precambrian microfossils

    Science.gov (United States)

    Wacey, David; Saunders, Martin; Kong, Charlie

    2018-04-01

    The ∼3430 Ma Strelley Pool Formation (SPF), Pilbara, Western Australia contains some of the most diverse microfossil evidence for early life on Earth. Here we report an assemblage of tephra (scoria, tubular pumice, plus vesicular and non-vesicular volcanic glass shards) from two stratigraphic levels in the SPF, including morphotypes that closely resemble previously described microfossils from this unit and elsewhere. Clasts of scoria are characterised by numerous spheroidal vesicles, with subordinate eye- and lens-shaped morphotypes, commonly lined with anatase (TiO2) and small amounts of organic material. Their diameters range from 5-180 μm with 80% in the 10-50 μm range. Fragments of tubular pumice are also lined with anatase + / - carbon and have tube diameters of 5-15 μm. Other volcanic ejecta particles include a multitude of sub-angular shard particles with or without vesicles, plus more rounded vase-shaped, eye-shaped, and hair-like morphologies; once again, most of these are coated by anatase + / - carbon and are several tens of micrometres in size. Many of the tephra fragments are now entirely silicified with no compositional difference between the former volcanic glass, the vesicle infill and the clast matrix. However, some examples retain a partial aluminosilicate composition, either as a vesicle infilling phase or as isolated lath-like grains within the formerly glassy groundmass. Isolated occurrences of some of these tephra morphotypes strongly resemble simple microbial morphologies including pairs and clusters of cells (cf. scoria), filamentous microbes (cf. tubular pumice) and larger sheaths/cysts (cf. sub-rounded glass shards). Furthermore, some tephra-containing clasts occur in a SPF sandstone unit that hosts previously described microfossils, while others are interbedded with chert layers from which microfossils have also been described. In light of our new volcanogenic data, we evaluate the robustness of previous microfossil evidence from the

  6. A 1000-year record of dry conditions in the eastern Canadian prairies reconstructed from oxygen and carbon isotope measurements on Lake Winnipeg sediment organics

    Science.gov (United States)

    Buhay, W.M.; Simpson, S.; Thorleifson, H.; Lewis, M.; King, J.; Telka, A.; Wilkinson, Philip M.; Babb, J.; Timsic, S.; Bailey, D.

    2009-01-01

    A short sediment core (162 cm), covering the period AD 920-1999, was sampled from the south basin of Lake Winnipeg for a suite of multi-proxy analyses leading towards a detailed characterisation of the recent millennial lake environment and hydroclimate of southern Manitoba, Canada. Information on the frequency and duration of major dry periods in southern Manitoba, in light of the changes that are likely to occur as a result of an increasingly warming atmosphere, is of specific interest in this study. Intervals of relatively enriched lake sediment cellulose oxygen isotope values (??18Ocellulose) were found to occur from AD 1180 to 1230 (error range: AD 1104-1231 to 1160-1280), 1610-1640 (error range: AD 1571-1634 to 1603-1662), 1670-1720 (error range: AD 1643-1697 to 1692-1738) and 1750-1780 (error range: AD 1724-1766 to 1756-1794). Regional water balance, inferred from calculated Lake Winnipeg water oxygen isotope values (??18Oinf-lw), suggest that the ratio of lake evaporation to catchment input may have been 25-40% higher during these isotopically distinct periods. Associated with the enriched d??18Ocellulose intervals are some depleted carbon isotope values associated with more abundantly preserved sediment organic matter (d??13COM). These suggest reduced microbial oxidation of terrestrially derived organic matter and/or subdued lake productivity during periods of minimised input of nutrients from the catchment area. With reference to other corroborating evidence, it is suggested that the AD 1180-1230, 1610-1640, 1670-1720 and 1750-1780 intervals represent four distinctly drier periods (droughts) in southern Manitoba, Canada. Additionally, lower-magnitude and duration dry periods may have also occurred from 1320 to 1340 (error range: AD 1257-1363), 1530-1540 (error range: AD 1490-1565 to 1498-1572) and 1570-1580 (error range: AD 1531-1599 to 1539-1606). ?? 2009 John Wiley & Sons, Ltd.

  7. Terrestrial environmental changes around the Gulf of Aden over the last 210 kyr deduced from the sediment n-alkane record: Implications for the dispersal of Homo sapiens

    Science.gov (United States)

    Isaji, Yuta; Kawahata, Hodaka; Ohkouchi, Naohiko; Murayama, Masafumi; Tamaki, Kensaku

    2015-03-01

    We analyzed long-chain (C25-C36) n-alkanes and pollen grains in sediments from the Gulf of Aden covering the last 212 kyr to reconstruct the surrounding terrestrial environment, a critical region for the dispersal of Homo sapiens. Substantial increases in the flux of n-alkanes during 200-185, 120-95, and 70-50 ka were interpreted to indicate enhanced vegetation biomass in the Arabian Peninsula and the northern part of the Horn of Africa or increase in lithogenic material inputs. Periods of enhanced n-alkane flux occurred during or immediately after pluvial episodes, indicating that the increased precipitation may have induced substantially enhanced vegetation biomass, creating favorable conditions for Homo sapiens. Additionally, vegetation may have increased due to moderate precipitation unrecorded by speleothems or in accordance with the lowering of sea level, indicating that the dispersal might have been possible even after the shift to an arid environment indicated by the speleothems.

  8. A 50-years record of dichloro-diphenyl-trichloroethanes and hexachlorocyclohexanes in lake sediments and penguin droppings on King George Island, Maritime Antarctic.

    Science.gov (United States)

    Sun, Li-guang; Yin, Xue-bin; Pan, Can-ping; Wang, Yu-hong

    2005-01-01

    Since the ban on the use of organochlorine pesticides (OCPs) such as dichloro-diphenyl-trichloroethane (DDT) and hexachlorocyclohexane(HCH) in agriculture, their levels have generally dropped. In a number of cases, however, the levels of these OCPs were found to be unchanging or even increasing after the ban. With the aim to unveil the possible causes of these exceptions, we collected two lake cores from King George Island, West Antarctica, and determined their accumulation flux profiles and temporal trends of these OCPs. In the lake core sediments with glacier meltwater input, the accumulation flux of DDT shows an abnormal peak around 1980s in addition to the expected one in 1960s. In the lake core sediments without glacier meltwater input, the accumulation flux of DDT shows a gradual decline trend after the peak in 1960s. This striking difference in the DDT flux profiles between the two lake cores is most likely caused by the regional climate warming and the resulted discharge of the DDT stored in the Antarctic ice cap into the lakes in the Antarctic glacier frontier. Furthermore, to investigate the change of OCPs loadings in the Antarctic coastal ecosystem, we reconstructed the HCH and DDT concentration profiles in penguin droppings and observed a gradual increase for the former and a continuous decrease for the latter during the past 50 years. The increase of HCH seems to be due to the regional warming from the early 1970s and the resulted HCH discharge to the coastal ecosystem by glaciers' meltwater and the illegal use of HCH in the Southern Hemisphere in the recent decade. Thedifferent temporal trends of HCH and DDT accumulation rate in the lake core with glacier meltwater input and the aged penguin droppings can be explained by their different water-soluble property.

  9. Potential and limits of OSL, TT-OSL, IRSL and pIRIR290 dating methods applied on a Middle Pleistocene sediment record of Lake El'gygytgyn, Russia

    Directory of Open Access Journals (Sweden)

    A. Zander

    2013-03-01

    Full Text Available This study tests the paleomagnetic and proxy-data based Mid- to Upper Pleistocene sediment deposition history of Lake El'gygytgyn by applying different approaches of luminescence dating techniques on sediment cores taken from the centre of the 175 m deep lake. For dating polymineral and quartz fine grains (4–11 μm grain size range were extracted from nine different levels from the upper 28 m of sediment cores 5011-1A and 5011-1B. According to the independent age model, the lowest sample from 27.8–27.9 m below lake bottom level correlates to the Brunhes-Matuyama (B/M reversal. Polymineral sub-samples were analysed by infra-red stimulated luminescence (IRSL and post-IR IRSL measured at 290 °C (pIRIR290 using single aliquot regenerative dose (SAR sequences. SAR protocols were further applied to measure the blue light optically stimulated luminescence (OSL and thermally-transferred OSL (TT-OSL of fine-grained quartz supplemented by a multiple aliquot approach. Neither low temperature IRSL measurements at 50 °C nor any OSL dating approach on quartz yielded reliable results. Deconvolution of their dose response curves revealed a pseudo-increase of the dose response curves and explains the observed underestimation. The pIRIR protocol applied to polymineral fine grains was the only luminescence technique able to provide dating results of acceptable accuracy up to ca. 700 ka when correlated to the existing proxy-data and paleomagnetic based age record. We present the potential and limits of the different dating techniques and a correlation of pIRIR290 results with the proxy-data based age model.

  10. Interactions between climate and vegetation during the Lateglacial period as recorded by lake and mire sediment archives in Northern Italy and Southern Switzerland

    NARCIS (Netherlands)

    Vescovi, E.; Ravazzi, C.; Arpenti, E.; Finsinger, W.; Pini, R.; Valsecchi, V.; Wick, L.; Ammann, B.; Tinner, W.

    2007-01-01

    We reconstruct the vegetational history of the southern side of the Alps at 18,000–10,000 cal yr BP using previous and new AMS-dated stratigraphic records of pollen, stomata, and macrofossils. To address potential effects of climatic change on vegetation, we compare our results with independent

  11. The 129iodine bomb pulse recorded in Mississippi River Delta sediments: results from isotopes of I, Pu, Cs, Pb, and C

    Science.gov (United States)

    Oktay, S. D.; Santschi, P. H.; Moran, J. E.; Sharma, P.

    2000-03-01

    129I ( t1/2 = 1.56 × 10 7 yr) has both natural as well as anthropogenic sources. Anthropogenic sources from nuclear reprocessing discharges and bomb test fallout have completely overwhelmed the natural signal on the surface of the earth in the last 50 years. However, the transfer functions in and out of environmental compartments are not well known due to temporal variations in the sources of 129I and to a lack of knowledge regarding the forms of iodine. From a vertical profile of 129I/ 127I ratios in sediments located in the Mississippi Delta region in approximately 60 meters water depth, the 129I input function to this region was reconstructed. Dates in the core were assigned based on the plutonium peak at 20 cm depth (assumed to have been deposited in 1963) and the excess 210Pb profile in the same depth interval, and below that, based on the steadily decreasing 240Pu/ 239Pu ratios from a ratio of 0.18 at 22 cm to 0.05 at 57 cm depth, the 1953 horizon. These low 240Pu/ 239Pu values are attributed to low yield, close-in, tropospherically transported bomb fallout produced from the Nevada test site in the early 1950s, which had a value of about 0.035, and strongly suggest a terrestrial source for Pu isotopes. 129I/ 127I ratios increased from 2 × 10 -10 at 3 cm to 4 × 10 -10 at 20 cm, and from there decreased monotonously to pre-anthropogenic values at 53 cm and below. 129I concentrations ranged from 8-13 × 10 6 atoms/g in the top 20 cm, and decreased to values of less than 1 × 10 6 atoms/g below 50 cm. Atom ratios of 129I/ 137Cs, decay corrected to 1962, the year of maximum radionuclide production, are about 0.3, very close to the production ratios of about 0.2 during atomic bomb tests. This evidence, combined with other observations, strongly suggests that 129I in Mississippi River Delta sediments originates from atomic bomb fallout eroded from soils of the Mississippi River drainage basin, with little alteration of the isotopic ratios during transport from

  12. Aligning and synchronization of MIS5 proxy records from Lake Ohrid (FYROM) with independently dated Mediterranean archives: implications for DEEP core chronology

    Science.gov (United States)

    Zanchetta, Giovanni; Regattieri, Eleonora; Giaccio, Biagio; Wagner, Bernd; Sulpizio, Roberto; Francke, Alex; Vogel, Hendrik; Sadori, Laura; Masi, Alessia; Sinopoli, Gaia; Lacey, Jack H.; Leng, Melanie J.; Leicher, Niklas

    2016-05-01

    The DEEP site sediment sequence obtained during the ICDP SCOPSCO project at Lake Ohrid was dated using tephrostratigraphic information, cyclostratigraphy, and orbital tuning through the marine isotope stages (MIS) 15-1. Although this approach is suitable for the generation of a general chronological framework of the long succession, it is insufficient to resolve more detailed palaeoclimatological questions, such as leads and lags of climate events between marine and terrestrial records or between different regions. Here, we demonstrate how the use of different tie points can affect cyclostratigraphy and orbital tuning for the period between ca. 140 and 70 ka and how the results can be correlated with directly/indirectly radiometrically dated Mediterranean marine and continental proxy records. The alternative age model presented here shows consistent differences with that initially proposed by Francke et al. (2015) for the same interval, in particular at the level of the MIS6-5e transition. According to this new age model, different proxies from the DEEP site sediment record support an increase of temperatures between glacial to interglacial conditions, which is almost synchronous with a rapid increase in sea surface temperature observed in the western Mediterranean. The results show how a detailed study of independent chronological tie points is important to align different records and to highlight asynchronisms of climate events. Moreover, Francke et al. (2016) have incorporated the new chronology proposed for tephra OH-DP-0499 in the final DEEP age model. This has reduced substantially the chronological discrepancies between the DEEP site age model and the model proposed here for the last glacial-interglacial transition.

  13. Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries

    OpenAIRE

    Thevenon F; Graham ND; Chiaradia M; Arpagaus P; Wildi W; Pote J

    2011-01-01

    This research first focuses on the spatial and temporal patterns of heavy metals from contrasting environments (highly polluted to deepwater sites) of Lake Geneva. The mercury (Hg) and lead (Pb) records from two deepwater sites show that the heavy metal variations before the industrial period are primarily linked to natural weathering input of trace elements. By opposition the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century i...

  14. Stratigraphy and chronology of a 15 ka sequence of multi-sourced silicic tephras in a montane peat bog, eastern North Island, New Zealand

    International Nuclear Information System (INIS)

    Lowe, D.J.; Newnham, R.M.; Ward, C.M.

    1999-01-01

    We document the stratigraphy, composition, and chronology of a succession of 16 distal, silicic tephra layers interbedded with lateglacial and Holocene peats and muds up to c. 15 000 radiocarbon years (c. 18 000 calendar years) old at a montane site (Kaipo Bog) in eastern North Island, New Zealand. Aged from 665 + or - 15 to 14 700 + or - 95 14 C yr BP, the tephras are derived from six volcanic centres in North Island, three of which are rhyolitic (Okataina, Taupo, Maroa), one peralkaline (Tuhua), and two andesitic (Tongariro, Egmont). Correlations are based on multiple criteria: field properties and stratigraphic interrelationships, ferromagnesian silicate mineral assemblages, glass-shard major element composition (from electron microprobe analysis), and radiocarbon dating. We extend the known distribution of tephras in eastern North Island and provide compositional data that add to their potential usefulness as isochronous markers. The chronostratigraphic framework established for the Kaipo sequence, based on both site-specific and independently derived tephra-based radiocarbon ages, provides the basis for fine-resolution paleoenvironmental studies at a climatically sensitive terrestrial site from the mid latitudes of the Southern Hemisphere. Tephras identified as especially useful paleoenvironmental markers include Rerewhakaaitu and Waiohau (lateglacial), Konini (late-glacial-early Holocene), Tuhua (middle Holocene), and Taupo and Kaharoa (late Holocene). (author). 102 refs., 3 tabs., 3 figs

  15. Radiocarbon Ages and Environments of Deposition of the Wono and Trego Hot Springs Tephra Layers in the Pyramid Lake Subbasin, Nevada

    Science.gov (United States)

    Benson, L.V.; Smoot, J.P.; Kashgarian, Michaele; Sarna-Wojcicki, A.; Burdett, J.W.

    1997-01-01

    Uncalibrated radiocarbon data from core PLC92B taken from Wizards Cove in the Pyramid Lake subbasin indicate that the Trego Hot Springs and Wono tephra layers were deposited 23,200 ?? 300 and 27,300 ??300 14C yr B.P. (uncorrected for reservoir effect). Sedimentological data from sites in the Pyramid Lake and Smoke Creek-Black Rock Desert subbasins indicate that the Trego Hot Springs tephra layer was deposited during a relatively dry period when Pyramid Lake was at or below its spill point (1177 m) to the Winnemucca Lake subbasin. The Wono tephra layer was deposited when lake depth was controlled by spill across Emerson Pass sill (1207 m) to the Smoke Creek-Black Rock Desert subbasin. 18O data from core PLC92B also support the concept that the Trego Hot Springs tephra fell into a relatively shallow Pyramid Lake and that the Wono tephra fell into a deeper spilling lake. ?? 1997 University of Washington.

  16. High-MgO Vitric Ash in Upper Kulanaokuaiki Tephra, Kilauea Volcano, Hawai`i: A Preliminary Description

    Science.gov (United States)

    Rose, T. R.; Fiske, R. S.; Swanson, D.

    2011-12-01

    Small, well-formed Pele's tears containing anomalously high values of MgO were recently discovered in outcrops of the upper Kulanaokuaiki Tephra at and near the base of Uwekahuna Bluff, the western wall of Kilauea Caldera. Electron microprobe analyses of more than 60 high-MgO tears, which are 1-3 mm in diameter, show that most contain 11 to 12 wt. % MgO with a few approaching 13 % MgO. Separate microprobe analyses for sulfur and chlorine of 20 grains revealed no appreciable amounts of either, indicating the magma was largely degassed. Polished-section studies employing an analytical scanning electron microscope show most tears are composed of pure microvesicular glass with scattered skeletal olivine crystals and rare chromite. The abundance of skeletal olivine appears to increase with decreasing MgO content of the glass. These tears contain among the highest known MgO values of any material erupted subaerially from Kilauea. The high-MgO tears occur in a 1-6 cm thick layer of medium-coarse lithic-crystal-vitric ash. The top of this layer consists of 2-3 mm of very fine lithic-crystal ash. The lithics and many of the olivine crystals in this layer are highly oxidized. This deposit is at the top of a sequence of several lithic beds that are interspersed with thinner vitric units totaling about 75 cm in thickness. It is overlain by 9-13 cm of medium pumice lapilli and coarse vitric ash at the top of the "Bluff base" and "mid-Bluff" tephra sections described by Fiske et al. (2009). This high-MgO glass layer has been found thus far in only one other locality, a 2 m-deep soils study pit within Kipuka Puaulu, 3.5 km northwest of the caldera. Based upon stratigraphic relationships and preliminary microprobe data, a few other likely exposures of the high-MgO deposit have been identified north and west of the caldera. The high-MgO vitric ash in the upper Kulanaokuaiki Tephra has a primitive composition that suggests little if any shallow level storage of magma. Instead, the

  17. Proterozoic events recorded in quartzite cobbles at Jack Hills, Western Australia: New constraints on sedimentation and source of > 4 Ga zircons

    Science.gov (United States)

    Grange, Marion L.; Wilde, Simon A.; Nemchin, Alexander A.; Pidgeon, Robert T.

    2010-03-01

    Rare heavy mineral bands within quartzite cobbles were identified in two conglomerate units within the Jack Hills belt, Western Australia. Seven zircon-bearing cobbles were analysed from one location (site 152) and three from another (site 154), both approximately 1 km west of the site where zircons in excess of 4 Ga are abundant (W74 'discovery' site). Individual pebbles from the 152 site reveal three distinctive features, containing either zircons > 3.0 Ga in age, 4 Ga was discovered from the entire suite of pebbles, in contrast to the well-studied W74 site. A single detrital zircon with an age of 1220 ± 42 Ma from location 152 is the youngest grain so far reported from sedimentary rocks at Jack Hills. It shows magmatic oscillatory zoning and thus implies at least two sedimentary cycles within the Proterozoic; requiring erosion of an igneous precursor, incorporation into a clastic sediment, induration and subsequent erosion and transport to be hosted in the conglomerate. The nearest source for rocks of this age is the Bangemall Supergroup in the Collier Basin, ˜ 100 km northeast in the Capricorn Orogen. This would imply tectonic interleaving of originally more extensive Bangemall rocks, possibly related to activity along the Cargarah Shear Zone that traverses the Jack Hills belt. The lack of > 4.1 Ga zircons in the pebbles is highly significant, suggesting the immediate source of ancient zircons was no longer present at the Earth's surface. This equates with a general lack of ancient crystals noted in rocks that contain Proterozoic zircons from previous studies and implies that such grains diminish in number as earlier sedimentary rocks were successively recycled.

  18. Historical volcanic eruptions in the Canary Islands, tephra composition, and insights into the crystal cargo of basaltic magmas

    Science.gov (United States)

    Longpre, M. A.; Muller, J.; Beaudry, P.; Andronikides, A.; Felpeto, A.

    2017-12-01

    Since the 16th century, at least 13 volcanic eruptions have occurred in the Canary Islands that formed monogenetic cinder cones and lava flow fields: 2 on Lanzarote, 4 on Tenerife, 6 on La Palma, and 1 on the submarine flank of El Hierro. Here we present a comprehensive new dataset of tephra composition for all 13 eruptions, comprising major and trace element data for bulk rocks and matrix glasses, as well as vesicularity and crystallinity measurements. In addition, we compile available volcanological and petrological information for specific eruptions, including estimates of lava flow area and volume. All lapilli samples show a vesicularity of 40-50 vol% and a vesicle-free crystallinity (crystals ≥ 250 µm) of 5-15 vol%. Modal mineralogy varies significantly between samples, typically consisting of olivine ± clinopyroxene ± Fe-Ti oxide ± plagioclase ± amphibole in different proportions. All but 2 tephras have basanite-tephrite bulk rock compositions. Lapilli from vents of the AD 1730-1736 Timanfaya eruption, Lanzarote, largely are basaltic, whereas the AD 1798 Chahorra eruption, Tenerife, produced phonotephrite tephra. These results are in agreement with published bulk lava flow data. Unsurprisingly, glass compositions are more evolved than bulk rocks and MgOglass is weakly positively correlated to MgObulk (MgOglass = 0.30*MgObulk + 2.11, R2 = 0.54). Both bulk rocks and glasses show strikingly similar multi-element diagram patterns, with strong enrichment relative to the bulk-silicate Earth and marked positive Nb and Ta and negative Pb anomalies — typical for ocean island basalts. Glass/bulk rock elemental ratios reveal systematic differences between samples that relate to their mineralogy; for example, Lanzarote tephras that lack significant clinopyroxene and Fe-Ti oxide crystals have higher Scglass/Scbulk and Vglass/Vbulk than Tenerife, La Palma and El Hierro samples that typically contain these minerals. Among all elements, K and P display the greatest

  19. Kulanaokuaiki Tephra (ca, A.D. 400-1000): Newly recognized evidence for highly explosive eruptions at Kilauea Volcano, Hawai'i

    Science.gov (United States)

    Fiske, R.S.; Rose, T.R.; Swanson, D.A.; Champion, D.E.; McGeehin, J.P.

    2009-01-01

    K??lauea may be one of the world's most intensively monitored volcanoes, but its eruptive history over the past several thousand years remains rather poorly known. Our study has revealed the vestiges of thin basaltic tephra deposits, overlooked by previous workers, that originally blanketed wide, near-summit areas and extended more than 17 km to the south coast of Hawai'i. These deposits, correlative with parts of tephra units at the summit and at sites farther north and northwest, show that K??lauea, commonly regarded as a gentle volcano, was the site of energetic pyroclastic eruptions and indicate the volcano is significantly more hazardous than previously realized. Seventeen new calibrated accelerator mass spectrometry (AMS) radiocarbon ages suggest these deposits, here named the Kulanaokuaiki Tephra, were emplaced ca. A.D. 400-1000, a time of no previously known pyroclastic activity at the volcano. Tephra correlations are based chiefly on a marker unit that contains unusually high values of TiO2 and K2O and on paleomagnetic signatures of associated lava flows, which show that the Kulanaokuaiki deposits are the time-stratigraphic equivalent of the upper part of a newly exhumed section of the Uw??kahuna Ash in the volcano's northwest caldera wall. This section, thought to have been permanently buried by rockfalls in 1983, is thicker and more complete than the previously accepted type Uw??kahuna at the base of the caldera wall. Collectively, these findings justify the elevation of the Uw??kahuna Ash to formation status; the newly recognized Kulanaokuaiki Tephra to the south, the chief focus of this study, is defined as a member of the Uw??kahuna Ash. The Kulanaokuaiki Tephra is the product of energetic pyroclastic falls; no surge- or pyroclastic-flow deposits were identified with certainty, despite recent interpretations that Uw??kahuna surges extended 10-20 km from K??lauea's summit. ?? 2009 Geological Society of America.

  20. Sediment Transport

    DEFF Research Database (Denmark)

    Liu, Zhou

    Flow and sediment transport are important in relation to several engineering topics, e.g. erosion around structures, backfilling of dredged channels and nearshore morphological change. The purpose of the present book is to describe both the basic hydrodynamics and the basic sediment transport...... mechanics. Chapter 1 deals with fundamentals in fluid mechanics with emphasis on bed shear stress by currents, while chapter 3 discusses wave boundary layer theory. They are both written with a view to sediment transport. Sediment transport in rivers, cross-shore and longshore are dealt with in chapters 2......, 4 and 5, respectively. It is not the intention of the book to give a broad review of the literature on this very wide topic. The book tries to pick up information which is of engineering importance. An obstacle to the study of sedimentation is the scale effect in model tests. Whenever small...

  1. Character, mass, distribution, and origin of tephra-fall deposits from the 2009 eruption of Redoubt Volcano, Alaska: highlighting the significance of particle aggregation

    Science.gov (United States)

    Wallace, Kristi; Coombs, Michelle L; Schaefer, Janet R.

    2013-01-01

    The 2009 eruption of Redoubt Volcano included 20 tephra-producing explosions between March 15, 2009 and April 4, 2009 (UTC). Next-Generation radar (NEXRAD) data show that plumes reached heights between 4.6 km and 19 km asl and were distributed downwind along nearly all azimuths of the volcano. Explosions lasted between 0.8 mm thick), including communities along the Kenai Peninsula (80–100 km) and the city of Anchorage (170 km). Trace ash (mass of tephra-fall deposits at 54.6 × 109 kg with a total DRE volume of 20.6 × 106 m3.

  2. Estimating sediment discharge: Appendix D

    Science.gov (United States)

    Gray, John R.; Simões, Francisco J. M.

    2008-01-01

    Sediment-discharge measurements usually are available on a discrete or periodic basis. However, estimates of sediment transport often are needed for unmeasured periods, such as when daily or annual sediment-discharge values are sought, or when estimates of transport rates for unmeasured or hypothetical flows are required. Selected methods for estimating suspended-sediment, bed-load, bed- material-load, and total-load discharges have been presented in some detail elsewhere in this volume. The purposes of this contribution are to present some limitations and potential pitfalls associated with obtaining and using the requisite data and equations to estimate sediment discharges and to provide guidance for selecting appropriate estimating equations. Records of sediment discharge are derived from data collected with sufficient frequency to obtain reliable estimates for the computational interval and period. Most sediment- discharge records are computed at daily or annual intervals based on periodically collected data, although some partial records represent discrete or seasonal intervals such as those for flood periods. The method used to calculate sediment- discharge records is dependent on the types and frequency of available data. Records for suspended-sediment discharge computed by methods described by Porterfield (1972) are most prevalent, in part because measurement protocols and computational techniques are well established and because suspended sediment composes the bulk of sediment dis- charges for many rivers. Discharge records for bed load, total load, or in some cases bed-material load plus wash load are less common. Reliable estimation of sediment discharges presupposes that the data on which the estimates are based are comparable and reliable. Unfortunately, data describing a selected characteristic of sediment were not necessarily derived—collected, processed, analyzed, or interpreted—in a consistent manner. For example, bed-load data collected with

  3. Heterogeneous distribution of pelagic sediments incoming the Japan Trench possibly controlling slip propagation on shallow plate boundary fault

    Science.gov (United States)

    Yamaguchi, A.; Nakamura, Y.; Fukuchi, R.; Kurano, H.; Ikehara, K.; Kanamatsu, T.; Arai, K.; Usami, K.; Ashi, J.

    2017-12-01

    Catastrophic tsunami of the 2011 Tohoku Earthquake was triggered by large coseismic slip reached to the Japan Trench axis (e.g. Fujiwara et al., 2011, Science; Kodaira et al., 2012, Nature Geoscience). Results of the IODP Expedition 343 (JFAST) suggest that small friction of smectite-rich pelagic clay caused slip propagation on shallow plate boundary fault (Ujiie et al., 2013, Science; Kameda et al., 2015, Geology; Moore et al., 2015, Geosphere). On the other hand, JAMSTEC high-resolution seismic profiles show that incoming sediments have large heterogeneities in thicknesses, and two areas of extremely thin sediments on the Pacific Plate (thickness less than 100 m) were found at around 39°N (Nakamura et al., AGU 2017, this session). To reconcile whether the smectite-rich pelagic clay even exists in these areas, we sampled surface sediments during the R/V Shinsei Maru KS-15-3 cruise. Seven piston cores were retrieved from seaward trench slope, horst, graben, and graben edge. Core lithologies are mainly diatomaceous ooze/clay including tephra layers, not resemble to pelagic clays discovered in JFAST. Ages of tephra layers were estimated by correlating mineral assemblages and refractive indices of volcanic glasses to Japanese widespread tephras. Averaged sedimentation rates of seaward trench slope, horst, graben, and graben edge are estimated to be 25-30, 6.5-20, 45, 0.9 cm/kyr, respectively. These sedimentation rates imply that sediments on seaward trench slope and horst have been deposited in the last 160-500 kyr, suggesting that entire pelagic sediments, including smectite-rich pelagic clay, have been removed by some reasons in the last 0.5 million years. Possible reason for such modification of sediment is near-trench igneous activity known as petit-spot volcanism (Hirano et al., 2006, Science). The lack of smectite-rich pelagic clay near 39°N of the Japan Trench is consistent with results of tsunami inversions proposing shallow large coseismic slip propagated

  4. A micromorphological study of pedogenic processes in an evolutionary soil sequence formed in late quaternary rhyolitic tephra deposits, North Island, New Zealand.

    NARCIS (Netherlands)

    Bakker, L.; Lowe, D.J.; Jongmans, A.G.

    1996-01-01

    The influence of time as a soil forming factor was studied on an evolutionary sequence of five soils (1850 radiocarbo years BP-ca. 120,000 BP) developed in rhyolitic tephra deposits in New Zealand. New micromorphological observations were combined with existing macromorphological, chemical,

  5. Automatized near-real-time short-term Probabilistic Volcanic Hazard Assessment of tephra dispersion before eruptions: BET_VHst for Vesuvius and Campi Flegrei during recent exercises

    Science.gov (United States)

    Selva, Jacopo; Costa, Antonio; Sandri, Laura; Rouwet, Dmtri; Tonini, Roberto; Macedonio, Giovanni; Marzocchi, Warner

    2015-04-01

    Probabilistic Volcanic Hazard Assessment (PVHA) represents the most complete scientific contribution for planning rational strategies aimed at mitigating the risk posed by volcanic activity at different time scales. The definition of the space-time window for PVHA is related to the kind of risk mitigation actions that are under consideration. Short temporal intervals (days to weeks) are important for short-term risk mitigation actions like the evacuation of a volcanic area. During volcanic unrest episodes or eruptions, it is of primary importance to produce short-term tephra fallout forecast, and frequently update it to account for the rapidly evolving situation. This information is obviously crucial for crisis management, since tephra may heavily affect building stability, public health, transportations and evacuation routes (airports, trains, road traffic) and lifelines (electric power supply). In this study, we propose a methodology named BET_VHst (Selva et al. 2014) for short-term PVHA of volcanic tephra dispersal based on automatic interpretation of measures from the monitoring system and physical models of tephra dispersal from all possible vent positions and eruptive sizes based on frequently updated meteorological forecasts. The large uncertainty at all the steps required for the analysis, both aleatory and epistemic, is treated by means of Bayesian inference and statistical mixing of long- and short-term analyses. The BET_VHst model is here presented through its implementation during two exercises organized for volcanoes in the Neapolitan area: MESIMEX for Mt. Vesuvius, and VUELCO for Campi Flegrei. References Selva J., Costa A., Sandri L., Macedonio G., Marzocchi W. (2014) Probabilistic short-term volcanic hazard in phases of unrest: a case study for tephra fallout, J. Geophys. Res., 119, doi: 10.1002/2014JB011252

  6. American West Tephras – Geomagnetic polarity events redefined through calibration of radio-isotopic and astronomical time

    DEFF Research Database (Denmark)

    Rivera, Tiffany; Storey, Michael

    calibration. Although this geomagnetic event is not part of the most recent geologic timescale, refined ages on short-lived excursions could hold importance to understanding time scales for the wavering nature of Earth’s magnetic field. We propose a new 40Ar/39Ar age for the Quaternary mineral dating standard......The foundation of the EARTHTIME/GTSnext initiative seeks to construct an internally consistent geologic timescale based on astronomical and radio-isotopic geochronology. American west tephras offer a prime opportunity to integrate these two independent timescales with the geomagnetic timescale....... Using an astronomically calibrated age for the monitor mineral Fish Canyon sanidine (FCs;28.201 ± 0.046 Ma, Kuiper, et al., 2008), ages of Pleistocene geomagnetic polarity events are reexamined. Of particular interest, the Quaternary mineral dating standard Alder Creek sandine (ACs) is the type locality...

  7. Timescales of mixing and storage for Keanakāko`i Tephra magmas (1500-1820 C.E.), Kīlauea Volcano, Hawai`i

    Science.gov (United States)

    Lynn, Kendra J.; Garcia, Michael O.; Shea, Thomas; Costa, Fidel; Swanson, Donald A.

    2017-09-01

    The last 2500 years of activity at Kīlauea Volcano (Hawai`i) have been characterized by centuries-long periods dominated by either effusive or explosive eruptions. The most recent period of explosive activity produced the Keanakāko`i Tephra (KT; ca. 1500-1820 C.E.) and occurred after the collapse of the summit caldera (1470-1510 C.E.). Previous studies suggest that KT magmas may have ascended rapidly to the surface, bypassing storage in crustal reservoirs. The storage conditions and rapid ascent hypothesis are tested here using chemical zoning in olivine crystals and thermodynamic modeling. Forsterite contents (Fo; [Mg/(Mg + Fe) × 100]) of olivine core and rim populations are used to identify melt components in Kīlauea's prehistoric (i.e., pre-1823) plumbing system. Primitive (≥Fo88) cores occur throughout the 300+ years of the KT period; they originated from mantle-derived magmas that were first mixed and stored in a deep crustal reservoir. Bimodal olivine populations (≥Fo88 and Fo83-84) record repeated mixing of primitive magmas and more differentiated reservoir components shallower in the system, producing a hybrid composition (Fo85-87). Phase equilibria modeling using MELTS shows that liquidus olivine is not stable at depths >17 km. Thus, calculated timescales likely record mixing and storage within the crust. Modeling of Fe-Mg and Ni zoning patterns (normal, reverse, complex) reveal that KT magmas were mixed and stored for a few weeks to several years before eruption, illustrating a more complex storage history than direct and rapid ascent from the mantle as previously inferred for KT magmas. Complexly zoned crystals also have smoothed compositional reversals in the outer 5-20 µm rims that are out of Fe-Mg equilibrium with surrounding glasses. Diffusion models suggest that these rims formed within a few hours to a few days, indicating that at least one additional, late-stage mixing event may have occurred shortly prior to eruption. Our study

  8. Fluvial sediment transport: Analytical techniques for measuring sediment load

    International Nuclear Information System (INIS)

    2005-07-01

    Sediment transport data are often used for the evaluation of land surface erosion, reservoir sedimentation, ecological habitat quality and coastal sediment budgets. Sediment transport by rivers is usually considered to occur in two major ways: (1) in the flow as a suspended load and (2) along the bed as a bed load. This publication provides guidance on selected techniques for the measurement of particles moving in both modes in the fluvial environment. The relative importance of the transport mode is variable and depends on the hydraulic and sedimentary conditions. The potential user is directed in the selection of an appropriate technique through the presentation of operating principles, application guidelines and estimated costs. Techniques which require laboratory analysis are grab sample, pump sample, depth sample, point integrated and radioactive tracers. Techniques which will continuously record data are optical backscattering, nuclear transmission, single frequency acoustic and laser diffraction

  9. Glacial magnetite dissolution in abyssal NW Pacific sediments - evidence for carbon trapping?

    Science.gov (United States)

    Korff, Lucia; von Dobeneck, Tilo; Frederichs, Thomas; Kasten, Sabine; Kuhn, Gerhard; Gersonde, Rainer; Diekmann, Bernhard

    2016-04-01

    followed by subsequent interglacial carbon burn-down and CO2 release. Abyssal Northwest Pacific sediments may have served as glacial carbon reservoir in particular since the onset of systematic 100 kyr ice age cycles at the end of the Mid-Pleistocene transition (MPT). Stagnant glacial Antarctic Bottom Water, which expanded primarily into abyssal South Atlantic basins during the MPT interim phase, thereafter seemed to flow preferentially into the deeper and larger abyssal Indo-Pacific basins, where it may have enabled more efficient carbon-trapping. More intensive scavenging of the Northwest Pacific surface ocean by enhanced glacial Asian dust flux is suggested by parallel TOC and quartz contents, enhancing glacial carbon accumulation despite potentially lower export production. The magnetic records also identify numerous partly consistent tephra layers, which can be matched between most records of the core transect.

  10. Characterization of diagenetic siderites formed in recent and ancient ferruginous sediments of Lake Towuti, Indonesia.

    Science.gov (United States)

    Vuillemin, Aurele; Kallmeyer, Jens; Wagner, Dirk; Kemnitz, Helga; Wirth, Richard; Luecke, Andreas; Mayr, Christoph

    2016-04-01

    Authigenic minerals in lacustrine settings can be formed in the water column and within the sediment, abiotically and/or triggered by biological activity. Such minerals have been used as paleosalinity and paleoproductivity proxies, reflecting trophic state, and/or early diagenetic conditions. They have also been considered as potential biosignatures of past and present microbial activity. Here we present a study from Lake Towuti, a deep tectonic basin in Sulawesi, Indonesia. Its geographic position makes it a prime location to record paleoclimatic changes in the tropical Western Pacific warm pool in its sedimentary sequence. The ultramafic rocks and surrounding lateritic soils in the catchment area supply considerable amounts of iron and other metals to the lake. These elements further restrain primary productivity along with the development of specific microbial metabolic pathways involved in early diagenesis. Lake Towuti is stratified with anoxic conditions below 130 m, allowing metal reduction processes to take place in the hypolimnion. The extreme scarcity of sulphate and nitrate/nitrite make Lake Towuti's bottom waters a modern analogue for the Archaean Ocean. It was therefore chosen as a drilling target by the International Continental Drilling Program (ICDP). In May to July 2015, the Towuti Drilling Project recovered a total >1000 m of sediment core from three drilling sites, including a 114 m long core drilled with a contamination tracer dedicated to geomicrobiological studies. Heavy mineral fractions were extracted from core catcher samples and siderite crystals (FeCO3) were selected from different depths. Characterization of their habitus was achieved via SEM and TEM imaging. Preliminary results show that siderites grow from amorphous into nanocrystalline phases and form twinned aggregates developing into mosaic monocrystals with depth. Gradual filling of vugs and microporosity were observed along with inclusions of magnetite nanocrystals. Work in

  11. Centennial-scale vegetation dynamics and climate variability in SE Europe during Marine Isotope Stage 11 based on a pollen record from Lake Ohrid

    Science.gov (United States)

    Kousis, Ilias; Koutsodendris, Andreas; Peyron, Odile; Leicher, Niklas; Francke, Alexander; Wagner, Bernd; Giaccio, Biagio; Knipping, Maria; Pross, Jörg

    2018-06-01

    To better understand climate variability during Marine Isotope Stage (MIS) 11, we here present a new, centennial-scale-resolution pollen record from Lake Ohrid (Balkan Peninsula) derived from sediment cores retrieved during an International Continental Scientific Drilling Program (ICDP) campaign. Our palynological data, augmented by quantitative pollen-based climate reconstructions, provide insight into the vegetation dynamics and thus also climate variability in SE Europe during one of the best orbital analogues for the Holocene. Comparison of our palynological results with other proxy data from Lake Ohrid as well as with regional and global climate records shows that the vegetation in SE Europe responded sensitively both to long- and short-term climate change during MIS 11. The chronology of our palynological record is based on orbital tuning, and is further supported by the detection of a new tephra from the Vico volcano, central Italy, dated to 410 ± 2 ka. Our study indicates that MIS 11c (∼424-398 ka) was the warmest interval of MIS 11. The younger part of the interglacial (i.e., MIS 11b-11a; ∼398-367 ka) exhibits a gradual cooling trend passing over into MIS 10. It is characterized by considerable millennial-scale variability as inferred by six abrupt forest-contraction events. Interestingly, the first forest contraction occurred during full interglacial conditions of MIS 11c; this event lasted for ∼1.7 kyrs (406.2-404.5 ka) and was characterized by substantial reductions in winter temperature and annual precipitation. Most notably, it occurred ∼7 ka before the end of MIS 11c and ∼15 ka before the first strong ice-rafted debris event in the North Atlantic. Our findings suggest that millennial-scale climate variability during MIS 11 was established in Southern Europe already during MIS 11c, which is earlier than in the North Atlantic where it is registered only from MIS 11b onwards.

  12. A high-resolution record of the Matuyama-Brunhes transition from the Mediterranean region: The Valle di Manche section (Calabria, Southern Italy)

    Science.gov (United States)

    Macrì, Patrizia; Capraro, Luca; Ferretti, Patrizia; Scarponi, Daniele

    2018-05-01

    High-resolution palaeomagnetic and rock magnetic investigations on the Valle di Manche section (Crotone Basin, Calabria, Southern Italy) provide a detailed record of the Matuyama-Brunhes (M-B) reversal that, to our best knowledge, is the only available record of the last geomagnetic reversal for the Mediterranean on-land marine stratigraphy. The M-B transition can be pinpointed precisely, as it develops within a 3-cm-thick interval located just above a prominent tephra layer (the "Pitagora ash") where the sedimentation rates are about 27 cm/kyr. Demagnetization analyses indicate a stable palaeomagnetic behaviour throughout the section for both normal and reversed polarity directions, with demagnetization vectors aligned toward the origin of Zijderveld diagrams after the removal of a small viscous low-coercivity remanence component. In the lower part of the studied interval, some samples acquired a spurious gyromagnetic remanent magnetization (GRM) during AF demagnetization in high fields. Rock magnetic analyses confirm that magnetite is the main magnetic carrier for all measured specimens, which also have an abundant paramagnetic fraction. Only the lower part of the record, well below the M-B boundary, is characterized by a downward-increasing presence of iron sulphides (greigite). According to our chronology, which is based on a robust, cross-validated age model, the final reverse-to-normal directional change of the M-B transition occurred at ca. 786.9 ± 5 ka (error includes uncertainty in orbital tuning) and was very rapid, of the order of 100 years or less.

  13. Hazard assessment of long-range tephra dispersal for a Plinian eruptive scenario at Popocatépetl volcano (Mexico). Inplications on civil aviation

    Science.gov (United States)

    Bonasia, R.; Scaini, C.; Capra, L.; Nathenson, M.; Siebe, C.; Arana-Salinas, L.; Folch, A.

    2013-12-01

    Popocatépetl is one of the most active volcanoes in Mexico threatening a densely populated area that includes Mexico City with more than 20 million inhabitants. The destructive potential of this volcano is demonstrated by its Late Pleistocene-Holocene eruptive activity, which has been characterized by recurrent Plinian eruptions of large magnitude. The current volcanic hazards map, reconstructed after the crisis occurred in 1994, considers the potential occurrence of different volcanic phenomena, including pyroclastic density currents and lahars. However, no quantitative assessment of the tephra dispersal hazard, especially related to atmospheric dispersal, has been performed. Given the high number of important airports in the surroundings of Popocatépetl volcano and considering the potential threat posed to civil aviation in Mexico and adjacent regions in case of a Plinian eruption, a hazard assessment for tephra dispersal is strongly required. In this work we present the first probabilistic tephra dispersal hazard assessment for Popocatépetl volcano. We compute probabilistic hazard maps for critical thresholds of airborne ash concentrations at different flight levels. Tephra dispersal modelling is performed using the FALL3D numerical model. Probabilistic hazard maps are built for a Plinian eruptive scenario defined on the basis of geological field data for the 'Ochre Pumice' Plinian eruption (4965 14C yrBP). FALL3D model input eruptive parameters are constrained through an inversion method carried out with the semi-analytical HAZMAP model and are varied sampling them on the base of a Probability Density Function. We analyze the influence of seasonal variations on ash dispersal and estimate the average persistence of critical ash concentrations at relevant locations and airports. This study assesses the impact that a Plinian eruption similar to the Ochre Pumice eruption would have on the main airports of Mexico and adjacent areas. The hazard maps presented here

  14. A suspended sediment yield predictive equation for river basins in ...

    African Journals Online (AJOL)

    The fit was found to be better than those relating mean annual specific suspended sediment yield to basin area or runoff only. Since many stream gauging stations in the country have no records on fluvial sediment, the empirical equation can be used to obtain preliminary estimates of expected sediment load of streams for ...

  15. Tectonic/climatic control on sediment provenance in the Cape Roberts Project core record (southern Victoria Land, Antarctica): A pulsing late Oligocene/early Miocene signal from south revealed by detrital thermochronology

    Science.gov (United States)

    Olivetti, V.; Balestrieri, M. L.; Rossetti, F.; Talarico, F. M.

    2012-04-01

    , three peaks are detected reflecting different bedrock provenance areas. Two peaks older than 40 Ma (P2 and P3) are compatible with thermochronological data from TAM bedrock that underwent a stepwise denudation in Cretaceous times. A Peak younger than 40 Ma (P1) has been detected occasionally, recording the signal of a source area exhumed during late Oligocene /early Miocene with a constant denudation rate of 0.4 mm/yr (constant lag-time up-section), but absent in the onshore portion of the proximal TAM. Indeed, when compared with AFT data from ANDRILL cores, the relatively young P1 ages, suggest that part of sediments in the Cape Robert Rift basin have a provenance from source regions probably located far away in the south (i.e. Skelton-Byrd glaciers region) where bedrock experienced compatible thermal histories. This provenance would imply glacial systems with main flow patterns from south to the north, therefore orthogonal to the orientation of present-day drainage. We thus infer that the post-Eocene glacial and erosional history of the TAM front was significantly controlled by the N-S-trending transtensional regime that affected the western Ross Sea margin during transition from orthogonal to oblique rifting in the region. The appearance and disappearance of P1 along the drill-cored stratigraphic succession seems to be linked to the oscillation in the extent of the ice sheet.

  16. Keanakākoʻi Tephra produced by 300 years of explosive eruptions following collapse of Kīlauea's caldera in about 1500 CE

    Science.gov (United States)

    Swanson, Donald A.; Rose, Timothy R.; Fiske, Richard S.; McGeehin, John P.

    2012-01-01

    The Keanakākoʻi Tephra at Kīlauea Volcano has previously been interpreted by some as the product of a caldera-forming eruption in 1790 CE. Our study, however, finds stratigraphic and 14C evidence that the tephra instead results from numerous eruptions throughout a 300-year period between about 1500 and 1800. The stratigraphic evidence includes: (1) as many as six pure lithic ash beds interleaved in sand dunes made of earlier Keanakākoʻi vitric ash, (2) three lava flows from Kīlauea and Mauna Loa interbedded with the tephra, (3) buried syneruptive cultural structures, (4) numerous intraformational water-cut gullies, and (5) abundant organic layers rich in charcoal within the tephra section. Interpretation of 97 new accelerator mass spectrometry (AMS) 14C ages and 4 previous conventional ages suggests that explosive eruptions began in 1470–1510 CE, and that explosive activity continued episodically until the early 1800s, probably with two periods of quiescence lasting several decades. Kīlauea's caldera, rather than forming in 1790, predates the first eruption of the Keanakākoʻi and collapsed in 1470–1510, immediately following, and perhaps causing, the end of the 60-year-long, 4–6 km3 ʻAilāʻau eruption from the east side of Kīlauea's summit area. The caldera was several hundred meters deep when the Keanakākoʻi began erupting, consistent with oral tradition, and probably had a volume of 4–6 km3. The caldera formed by collapse, but no eruption of lava coincided with its formation. A large volume of magma may have quickly drained from the summit reservoir and intruded into the east rift zone, perhaps in response to a major south-flank slip event, leading to summit collapse. Alternatively, magma may have slowly drained from the reservoir during the prolonged ʻAilāʻau eruption, causing episodic collapses before the final, largest downdrop took place. Two prolonged periods of episodic explosive eruptions are known at Kīlauea, the Keanak

  17. Keanakākoʻi Tephra produced by 300 years of explosive eruptions following collapse of Kīlauea's caldera in about 1500 CE

    Science.gov (United States)

    Swanson, Donald A.; Rose, Timothy R.; Fiske, Richard S.; McGeehin, John P.

    2012-01-01

    The Keanakākoʻi Tephra at Kīlauea Volcano has previously been interpreted by some as the product of a caldera-forming eruption in 1790 CE. Our study, however, finds stratigraphic and 14C evidence that the tephra instead results from numerous eruptions throughout a 300-year period between about 1500 and 1800. The stratigraphic evidence includes: (1) as many as six pure lithic ash beds interleaved in sand dunes made of earlier Keanakākoʻi vitric ash, (2) three lava flows from Kīlauea and Mauna Loa interbedded with the tephra, (3) buried syneruptive cultural structures, (4) numerous intraformational water-cut gullies, and (5) abundant organic layers rich in charcoal within the tephra section. Interpretation of 97 new accelerator mass spectrometry (AMS) 14C ages and 4 previous conventional ages suggests that explosive eruptions began in 1470–1510 CE, and that explosive activity continued episodically until the early 1800s, probably with two periods of quiescence lasting several decades. Kīlauea's caldera, rather than forming in 1790, predates the first eruption of the Keanakākoʻi and collapsed in 1470–1510, immediately following, and perhaps causing, the end of the 60-year-long, 4–6 km3 ʻAilāʻau eruption from the east side of Kīlauea's summit area. The caldera was several hundred meters deep when the Keanakākoʻi began erupting, consistent with oral tradition, and probably had a volume of 4–6 km3. The caldera formed by collapse, but no eruption of lava coincided with its formation. A large volume of magma may have quickly drained from the summit reservoir and intruded into the east rift zone, perhaps in response to a major south-flank slip event, leading to summit collapse. Alternatively, magma may have slowly drained from the reservoir during the prolonged ʻAilāʻau eruption, causing episodic collapses before the final, largest downdrop took place. Two prolonged periods of episodic explosive eruptions are known at Kīlauea, the Keanak

  18. Leaching of lava and tephra from the Oldoinyo Lengai volcano (Tanzania): Remobilization of fluorine and other potentially toxic elements into surface waters of the Gregory Rift

    Science.gov (United States)

    Bosshard-Stadlin, Sonja A.; Mattsson, Hannes B.; Stewart, Carol; Reusser, Eric

    2017-02-01

    Volcanic ash leachate studies have been conducted on various volcanoes on Earth, but few have been done on African volcanoes until now. Tephra emissions may affect the environment and the health of people living in this area, and therefore we conducted a first tephra (ash and lapilli sized) leachate study on the Oldoinyo Lengai volcano, situated in northern Tanzania. The recent explosive eruption in 2007-2008 provided us with fresh samples from the first three weeks of the eruption which were used for this study. In addition, we also used a natrocarbonatitic sample from the activity prior to the explosive eruption, as the major activity at Oldoinyo Lengai is natrocarbonatitic. To compare the leaching process affecting the natrocarbonatitic lavas and the tephras from Oldoinyo Lengai, the 2006 natrocarbonatitic lava flow was resampled 5 years after the emplacement and compared to the initial, unaltered composition. Special interest was given to the element fluorine (F), since it is potentially toxic to both humans and animals. A daily intake of fluoride (F-) in drinking water of > 1.5 mg/l can lead to dental fluorosis, and higher concentrations lead to skeletal fluorosis. For this reason, a guideline value for fluoride in drinking water was set by the WHO (2011) to 1.5 mg/l. However, surface waters and groundwaters in the Gregory Rift have elevated fluoride levels of up to 9.12 mg/l, and as a consequence, an interim guideline value for Tanzania has been set at 8 mg/l. The total concentration of fluorine in the samples from the natrocarbonatitic lava flow is high (3.2 wt%), whereas we observed a significant decrease of the fluorine concentration (between 1.7 and 0.5 wt%) in the samples collected three days and three weeks after the onset of the explosive 2007-08 eruption. However, the total amount of water-extractable fluoride is lower in the natrocarbonatitic lavas (319 mg/l) than in the nephelinitic tephra (573-895 mg/l). This is due to the solubility of the

  19. Chemistry of marine sediments

    International Nuclear Information System (INIS)

    Yen, T.F.

    1977-01-01

    Some topics considered are as follows: characterization of sediments in the vicinity of offshore petroleum production; thermal alteration experiments on organic matter in recent marine sediments as a model for petroleum genesis; composition of polluted bottom sediments in Great Lakes harbors; distribution of heavy metals in sediment fractions; recent deposition of lead off the coast of southern California; release of trace constituents from sediments resuspended during dredging operations; and migration of chemical constituents in sediment-seawater interfaces

  20. Extensive lake sediment coring survey on Sub-Antarctic Indian Ocean Kerguelen Archipelago (French Austral and Antarctic Lands)

    Science.gov (United States)

    Arnaud, Fabien; Fanget, Bernard; Malet, Emmanuel; Poulenard, Jérôme; Støren, Eivind; Leloup, Anouk; Bakke, Jostein; Sabatier, Pierre

    2016-04-01

    sequence from the newly-named Lake Tiercelin (2m-long) was recovered using UWITEC gravity coring equipment operated from a portable rubber boat by 54m water-depth. Those three sequences cover the whole Holocene periods. The 3m-long sequence taken in Lake Guynemer, Loranchet peninsula, was taken using a homemade small platform and a Nesje piston corer by 50m water-depth and covers the last 5 ka cal. BP. Two additional lakes were cored in the vicinity of Lake Armor: Fougères and Poule from which short sequences were taken in order to study environmental changes since the arrival of humans in the 18th century and the subsequent introduction of exogenous plant and animal species. We present here preliminary results including the dating of all sediment sequences as well as their chemical logging and sedimentological description. This already revealed the recurrence of Holocene volcanic eruptions as well as erosion patterns that are comparable among different records. The recognition of tephra layers will further allow the synchronization of terrestrial records together and with marine records around Kerguelen Archipelago. Paleoclimate interpretations of acquired data as well as further measurements are still ongoing processes. However, one may already argue that we collected rare geological sequences of prime importance in the quest of understanding climate patterns affecting the southern high latitudes all along the Holocene. 1. Lamy. et al. 2015. in Integr. Anal. of Intergl. Clim. Dyn. Schulz & Paul eds., 75-81 (Springer) 2. Rebolledo et al. 2015. Quat. Res. 84, 21-36 3. Agosta et al. 2015. Clim. Res. 62, 219-240 4. Van der Putten et al 2015. Quat. Sci. Rev. 122, 142-157

  1. History through sediments: environmental, land use and technological change in the record of a temperate wetland (Las Tablas de Daimiel, central Spain); La historia a traves de los sedimentos: cambios climaticos y de uso del suelo en el registro reciente de un humedal mediterraneo (Las Tablas de Daimiel, Ciudad Real)

    Energy Technology Data Exchange (ETDEWEB)

    Santisteban, J. I.; Mediavilla, R.; Gil Garcia, M. J.; Dominguez Castro, F.; Ruiz Zapata, M. B.

    2009-07-01

    The analysis of the sediments of a temperate wetland in central Spain (Las Tablas de Daimiel National Park) and their correlation to historical and documental data allows to interpret the environmental changes recorded in such sediments as due to the variable intensity human action in addition to the natural variability. Recorded events are related to land use changes that are caused by the socio economical circumstances of the surrounding human communities. Relative intensity and length of such impacts permits to estimate the duration of the anthropic events and the recovery ability of the natural system, evidencing that the intensity degree is determined by the technological capability to sustain a prolonged soil use. As a result, the Tablas de Daimiel National Park record has been divided in three periods: a natural period, when the impact of events is short and the environment is able to recover quickly, a pre industrial period, when changes are gradual but sustained, and an industrial period, when the sustained activity is so intense that the natural system is unable to recover. (Author) 34 refs.

  2. Distribution of butyltins in the waters and sediments along the coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Garg, A.; Meena, R; Jadhav, S.; Bhosle, N.B.

    for sediments it varied between below detection limit to 14861 ng Sn g sup(-1) dry weight of sediment. On an average Chennai port recorded the highest level of butyltins in the sediments while Paradip recorded the highest level of butylins in the waters. A...

  3. Petrography and geochemistry of achnelithic tephra from Las Herrerías Volcano (Calatrava volcanic field, Spain): Formation of nephelinitic achneliths and post-depositional glass alteration

    Science.gov (United States)

    Carracedo-Sánchez, M.; Sarrionandia, F.; Arostegui, J.; Errandonea-Martin, J.; Gil-Ibarguchi, J. I.

    2016-11-01

    We present the results of a petrographic and geochemical study carried out on a layer of achnelithic tephra outcropping at the base of the volcanic cone of Las Herrerías (Miocene-Quaternary volcanic region of Campo de Calatrava, Spain). The tephra, with a composition of nephelinite and ash (Pele's tears), achnelith fragments and rare welded achneliths. The achneliths at Las Herrerías were generated in a gas-rich fire fountain that fragmented the magma into micro- to nanometre particles. The low viscosity of the nephelinitic blebs (< 1235 Pa.s) inside the hottest (ca. 900 °C), inner zone of the fountain allowed the development of the characteristic fluidal shapes of these pyroclasts and their welding above the glass transition temperature (533-669 °C). The sideromelane glass of the achneliths, also nephelinitic in composition, is variably altered to palagonite. The palagonitization was isovolumetric and took place in a near closed system at the achnelith scale. Palagonitization involved depletion in the concentration (g/cm3) of all major elements and notable increase in H2O content. The elements liberated by this process formed smectite with an average structural formula comprised between those of beidellite and nontronite end terms: (Na0.01K0.03Ca0.18) (Mg0.22Fe0.16)2 + (Fe0.