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Sample records for cambrian metaclastic sediments

  1. Provenance of the late Proterozoic to early Cambrian metaclastic sediments of the Sierra de San Luis (Eastern Sierras Pampeanas) and Cordillera Oriental, Argentina

    Science.gov (United States)

    Drobe, Malte; López de Luchi, Mónica G.; Steenken, André; Frei, Robert; Naumann, Rudolf; Siegesmund, Siegfried; Wemmer, Klaus

    2009-10-01

    show one peak of detrital zircons around 550 Ma, and only a few grains are older than 700 Ma. The detrital zircon ages for the San Luis Formation show age ranges between 590 and 550 Ma. A common basin can be assumed for the Conlara Metamorphic Complex and the Puncoviscana Formation, but the available data support different sources for the rest of the Complexes of the Sierra de San Luis. These share the diminished importance or the lack of the Grenvillian detrital peak, a common feature for the late Cambrian-early Ordovician basins of the Eastern Sierras Pampeanas, in contrast to the Sierras de Córdoba, the PVF and the Conlara Metamorphic Complex.

  2. Provencance of the late Proterozoic to early Cambrian metaclastic sediments ot the Sierra de San Luis (Eastern Sierras Pampeanas) and Cordillera Oriental, Argentina

    DEFF Research Database (Denmark)

    Drobe, M.; López de Luchi, M.; Steenken, A.

    2009-01-01

    /204Pb values. Possible source rocks for the different domains could be the Quebrada Choja in the Central Arequipa-Antofalla domain, the Southern domain of the Arequipa-Antofalla basement, the Brazilian shield or southern Africa. Zircon SHRIMP data point to a connection between the Puncoviscana...

  3. Geochemistry of highly aluminiferous Vendian-Cambrian sediments of the Tunka Bald Mountains, East Sayan

    Science.gov (United States)

    Shkol'Nik, S. I.; Barash, I. G.; Belichenko, V. G.; Letnikova, E. F.

    2011-01-01

    This paper presents comprehensive geochemical characteristics of highly aluminiferous schists discovered in the Tunka Bald Mountains and associated with the Vendian-Cambrian cover of the Tuva-Mongolian Microcontinent. The Al2O3 content varies within a wide range, the maximum being up to 36.11 wt. %. A specific feature of the geochemical composition of these rocks is the simultaneously high contents of Cr (up to 1400 ppm), V (up to 2700 ppm), and Zr (up to 800 ppm). The origin has been interpreted, and the conditions in which the highly aluminiferous rocks formed have been considered. Based on geochemical data, it is assumed that the main origin could be weathering crusts formed after ultramafic and mafic rocks, with a felsic source playing a secondary role.

  4. The zircon evidence of temporally changing sediment transport—the NW Gondwana margin during Cambrian to Devonian time (Aoucert and Smara areas, Moroccan Sahara)

    Science.gov (United States)

    Gärtner, Andreas; Youbi, Nasrrddine; Villeneuve, Michel; Sagawe, Anja; Hofmann, Mandy; Mahmoudi, Abdelkader; Boumehdi, Moulay Ahmed; Linnemann, Ulf

    2017-03-01

    Detrital zircon provenance studies are an established tool to develop palaeogeographic models, mostly based on zircon of siliciclastic rocks and isotope data. But zircon is more than just istopes and features well definable morphological characteristics. The latter may indicate single grain transport histories independent of the individual grade of concordance. This additional tool for palaeogeoraphic reconstructions was tested on zircon from siliciclastic and carbonate sedimentary rocks of Palaeozoic age from the Aoucert and Smara areas of the Souttoufides, while findings of zircon in limestone generally open new archives for sedimentary provenance analysis. The morphologies—length, width, roundness, grain surfaces—of 834 detrital zircons from sediments of allochthonous Cambrian, and (par-)autochthonous Ordovician, and Devonian units were studied, while 772 of them were analysed for their U-Th-Pb isotopes by LA-ICP-MS. Mesoproterozoic zircon contents of more than 10% in the Cambrian sediments exclude the West African Craton (WAC) as exclusive source area. Thus, at least one additional external source is suggested. This is likely the western Adrar Souttouf Massif with its significant Mesoproterozoic zircon inheritance, or comparable, yet unknown sources. Decreasing Mesoproterozoic zircon age populations in Ordovician sediments are thought to be linked to the rifting of the terranes in the course of the Rheic Ocean opening and a predominant supply of WAC detritus. The Devonian sediments likely contain reworked material from the Cambrian siliciclastics, which is shown by the zircon age distribution pattern and the zircon morphologies. Therefore, multiple shifts in the direction of sedimentary transport are indicated.

  5. Provenance, tectonic setting and source-area weathering of the lower Cambrian sediments of the Parahio valley in the Spiti basin, India

    Science.gov (United States)

    Pandey, Shivani; Parcha, Suraj K.

    2017-03-01

    The geochemical study of siliciclastic rocks from the Lower Cambrian of Parahio Valley has been studied to describe the provenance, chemical weathering and tectonic setting. The K2O/Al2O3 ratio and positive correlation of Co ( r=0.85), Ni ( r=0.86), Zn ( r=0.82), Rb ( r=0.98) with K2O reflects that the presence of clay minerals control the abundances of these elements and suggests a warm and humid climate for this region. The chondrite normalized REE pattern of the samples is equivalent to upper continental crust, which reflects enriched LREE and flat HREE with negative Eu anomaly. The tectonic setting discriminant diagram log[K2O/Na2O] vs. SiO2; [SiO2/Al2O3] vs. log[K2O/Na2O]; [SiO2/20] - [K2O+Na2O] - [TiO2+Fe2O3+MgO] indicates transitional tectonic setting from an active continental margin to a passive margin. The discriminant function plot indicates quartzose sedimentary provenance, and to some extent, the felsic igneous provenance, derived from weathered granite, gneissic terrain and/or from pre-existing sedimentary terrain. The CIA value indicates low to moderate degree of chemical weathering and the average ICV values suggests immature sediments deposited in tectonically active settings. The A-CN-K diagram indicates that these sediments were generated from source rocks of the upper continental crust.

  6. Provenance, tectonic setting and source-area weathering of the lower Cambrian sediments of the Parahio valley in the Spiti basin, India

    Indian Academy of Sciences (India)

    Shivani Pandey; Suraj K Parcha

    2017-03-01

    The geochemical study of siliciclastic rocks from the Lower Cambrian of Parahio Valley has been studied to describe the provenance, chemical weathering and tectonic setting. The K ₂O/Al ₂O₃ ratio and positivecorrelation of Co (r = 0.85), Ni (r = 0.86), Zn (r = 0.82), Rb (r = 0.98) with K₂O reflects that the presence of clay minerals control the abundances of these elements and suggests a warm and humid climate for this region. The chondrite normalized REE pattern of the samples is equivalent to uppercontinental crust, which reflects enriched LREE and flat HREE with negative Eu anomaly. The tectonic setting discriminant diagram log[K ₂O/Na ₂O] vs. SiO ₂; [SiO ₂ /Al ₂O ₃] vs. log[K ₂O/Na ₂O]; [SiO ₂/20] – [K ₂O+Na ₂O] – [TiO ₂+Fe ₂O ₃+MgO] indicates transitional tectonic setting from an active continental margin to a passive margin. The discriminant function plot indicates quartzose sedimentary provenance, and to some extent, the felsic igneous provenance, derived from weathered granite, gneissic terrain and/orfrom pre-existing sedimentary terrain. The CIA value indicates low to moderate degree of chemical weathering and the average ICV values suggests immature sediments deposited in tectonically active settings. The A–CN–K diagram indicates that these sediments were generated from source rocks of theupper continental crust.

  7. Reconstruction of early Cambrian ocean chemistry from Mo isotopes

    Science.gov (United States)

    Wen, Hanjie; Fan, Haifeng; Zhang, Yuxu; Cloquet, Christophe; Carignan, Jean

    2015-09-01

    The Neoproterozoic-Cambrian transition was a key time interval in the history of the Earth, especially for variations in oceanic and atmospheric chemical composition. However, two conflicting views exist concerning the nature of ocean chemistry across the Precambrian-Cambrian boundary. Abundant geochemical evidence suggests that oceanic basins were fully oxygenated by the late Ediacaran, while other studies provide seemingly conflicting evidence for anoxic deep waters, with ferruginous conditions [Fe(II)-enriched] persisting into the Cambrian. Here, two early Cambrian sedimentary platform and shelf-slope sections in South China were investigated to trace early Cambrian ocean chemistry from Mo isotopes. The results reveal that early Cambrian sediments deposited under oxic to anoxic/euxinic conditions have δ98/95Mo values ranging from -0.28‰ to 2.29‰, which suggests that early Cambrian seawater may have had δ98/95Mo values of at least 2.29‰, similar to modern oceans. The heaviest and relatively homogeneous δ98/95Mo values were recorded in siltstone samples formed under completely oxic conditions, which is considered that Mn oxide-free shuttling was responsible for such heavy δ98/95Mo value. Further, combined with Fe species data and the accumulation extent of Mo and U, the variation of δ98/95Mo values in the two studied sections demonstrate a redox-stratified ocean with completely oxic shallow water and predominantly anoxic (even euxinic) deeper water having developed early on, which eventually became completely oxygenated. This suggests that oceanic circulation at the time became reorganized, and such changes in oceanic chemistry may have been responsible for triggering the "Cambrian Explosion" of biological diversity.

  8. High continental weathering rate during Early Cambrian: Evidence from Os isotopic composition of Early Cambrian Ocean

    Science.gov (United States)

    Jiang, S.-Y.; Yang, J.-H.; Ling, H.-F.; Feng, H.-Z.; Chen, Y.-Q.; Chen, J.-H.

    2003-04-01

    The paleo-ocean environmental change during the Precambrian-Cambrian transition is a key issue related to the causes for an explosive radiation of different metazoan phyla during Early Cambrian. The chemical and isotopic compositions of marine sediments and chemical precipitates such as carbonates, phosphorites, siliceous rocks, and black shales record the changing composition and physical conditions of the seawater in which these rocks accumulated. Organic carbon-rich black shales from marine environments are commonly enriched in a number of trace elements such as Ni, Mo, V, Co, Cr, Au, U, As, Pb, Zn, Cu, Re, and platinum-group-elements (PGE). Recent researches have demonstrated that Re-Os isotopes and PGE contents in black shales are useful proxies for seawater chemistry. It is believed that Re and Os in orgainc-carbon rich black shales are mostly hydrogeneous in origin which were largely sequestered from seawater at the time of deposition. In South China, the Lower Cambrian black shale sequence of the Niutitang Formation (and lateral equivalents) exists broadly several thousands kilometers. The lowermost sequence of this formation contain a thin sulfide ore horizon with an apparently unique and extreme case of metal enrichments such as Mo, Ni, Se, Re, Os, As, Hg, Sb, Ag, Au, Pt, and Pd. In this study, we conducted a preliminary investigation of Re-Os isotopes and Plantium Group Element (PGE) distribution patterns of the balck shales and intercalated Ni-Mo polymetallic sulfide bed from Guizhou and Hunan Provinces. The high rOs(t) values of the black shales indicate that the Early Cambrian ocean in Yangtze Platform had a highly radiogenic Os, possibly as a result of high continental weathering rate at that time. The Ni-Mo polymetallic sulfide ores within the black shales have lower rOs(t) values than the black shales, and they show similar REE and PGE patterns as the hydrothermal siliceous rocks within the Lower Cambrian strata, which suggest that the Ni

  9. Umbrella structure and channel-wall stoping in the Cambrian St. Roch Formation, Quebec Appalachians: significance for particle support mechanisms and turbulence development in hyper-concentrated sediment gravity flows

    Science.gov (United States)

    Hesse, Reinhard; Fong, Christopher

    2014-03-01

    Umbrella structure is a newly recognized sedimentary structure associated with large platy clasts in resedimented boulder-bearing pebble conglomerate with a sandy matrix. It consists of a sand rim that lacks pebbles on parts or the entire underside of platy boulders, whereas on the upper side, pebbles are in direct contact with the boulders. The depositing processes were high- to hyper-concentrated sediment gravity flows in a submarine channel or canyon on the Cambrian continental slope of North America bordering the Iapetus Ocean. The structure occurs predominantly where clasts dip moderately in the down-current direction. Based on the association of the structure with slightly forward dipping slabs, it is proposed that these down-current dipping slabs may have been in the process of counter-clockwise rotation that was aborted and may have generated a pressure shadow on the underside enabling the inrush of fluid and the infiltration of sand into the anomalous low-pressure zone. The structure has implications for particle support mechanisms in high- to hyper-concentrated sedimentary gravity flows, in that it redirects attention to the much debated mechanism of dispersive pressure and alternatives. It provides an observable sediment structure that supports dispersive pressure which so far depended on experimental evidence and theoretical arguments alone. Vrolijk and Southard's (1997) concept of a `laminar sheared layer' is here for the first time interpreted as having an upward-moving `free-surface' layer effect during deposition from hyper-concentrated flows. Channel-wall stoping involves unlithified turbiditic spillover sand in the levee sediment of the canyon wall that was washed out by the upper diluted parts of the high-concentration flows coming down the channel and leaving a niche in the wall that was filled with coarser channel-axis facies by the same flow (or later flows) when its aggradation reached the level of the niche. The contact between turbidite and

  10. The Cambrian impact hypothesis

    CERN Document Server

    Zhang, Weijia

    2008-01-01

    After a thorough research on the circumstantial changes and the great evolution of life in the Cambrian period, the author propounds such a hypothesis: During the Late Precambrian, about 500-600Ma, a celestial body impacted the Earth. The high temperature ended the great glaciation, facilitated the communication of biological information. The rapid change of Earth environment enkindled the genesis-control system, and released the HSP-90 variations. After the impact, benefited from the protection of the new ozone layer and the energy supplement of the aerobic respiration, those survived underground life exploded. They generated carapaces and complex metabolism to adjust to the new circumstance of high temperature and high pressure. This article uses a large amount of analyses and calculations, and illustrates that this hypothesis fits well with most of the important incidences in astronomic and geologic discoveries.

  11. Sponge fossil assemblage from the Early Cambrian Hetang Formation in southern Anhui

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhe; HU Jie; ZHOU Chuanming; XIAO Shuhai; YUAN Xunlai

    2004-01-01

    Abundant well-preserved large articulated sponge fossils and isolated spicules have been reported from the Early Cambrian Hetang Formation, southern Anhui Province. This unique epifaunal fossil assemblage dominated by articulated sponge fossils is called the Xidi Sponge Fauna.The sponge fauna lived in a quiet oxygenic environment below the storm wave base. Bloom of phytoplankton and rapid sedimentation rate resulted in the deposition of the black shales. Sufficient food supply, lack of other competitors,abundant ecological niches, and demand for oxygen during early Cambrian were in favor of the diversification and evolution of large sponges in the Early Cambrian.

  12. Towering sponges in an Early Cambrian Lagerstätte: Disparity between nonbilaterian and bilaterian epifaunal tierers at the Neoproterozoic-Cambrian transition

    Science.gov (United States)

    Yuan, Xunlai; Xiao, Shuhai; Parsley, Ronald L.; Zhou, Chuanming; Chen, Zhe; Hu, Jie

    2002-04-01

    Epifaunal, suspension-feeding bilaterian animals in the Cambrian lived close to the sediment-water interface, and hence their ecological tiering levels were low (Burgess Shale, and Sinsk biotas. These data are consistent with medium- to high-tiering levels in Neoproterozoic-Cambrian epifaunal communities, but suggest that nonbilaterians achieved such tiering levels long before bilaterian suspension feeders did so in the Early Ordovician. The disparity between bilaterian and nonbilaterian tierers during the Neoproterozoic-Cambrian transition and the delayed appearance of high-tiering bilaterians demand phylogenetic and ecological explanations. The Cambrian substrate revolution may have triggered a cascade of ecological evolution, including the rise of bilaterian animals in high-tiering levels during the Ordovician radiation of the Paleozoic fauna.

  13. Provenance shift in Cambrian mid-Baltica: detrital zircon chronology of Ediacaran–Cambrian sandstones in Estonia

    Directory of Open Access Journals (Sweden)

    Yukio Isozaki

    2014-12-01

    Full Text Available In order to clarify the tectono-sedimentary history of Paleozoic Baltica, age spectra of detrital zircon grains from the Ediacaran (Kotlin Regional Stage and Lower Cambrian sandstones (lowermost Lontova and Lükati formations in western Estonia in central Baltica were analyzed by LA-ICPMS. The abundant occurrence of Archean to Mesoproterozoic (2800–1000 Ma zircon grains was confirmed in all samples. The new data provided the following information on the provenance of siliciclastic material as well as a major change in the sedimentary regime of the Paleo-Baltic basin during the Early Cambrian: (1 the Ediacaran–Lower Cambrian Paleo-Baltic basin received abundant terrigenous clastics from the core of Baltica underlain by the Archean–Mesoproterozoic crystalline crust, (2 the exposed surface area of the 1600 Ma Rapakivi granites apparently was more extensive during the Ediacaran–Early Cambrian than at present, (3 a major re-organization of the basin geometry occurred in the middle Early Cambrian (ca 530–515 Ma in central Baltica, inducing a change in the sediment supply system, (4 in contrast to the total absence of Neoproterozoic detrital zircon grains before the middle Early Cambrian, their sudden appearance at this time, together with consistent occurrence at least until the mid-Devonian, suggests a significant uplift event located in southeast Baltica and/or in a more easterly land domain (e.g., in Sarmatia, (5 possible sources for the Neoproterozoic zircon grains include the peripheral mobile belts with pan-African signatures around Baltica, e.g., the so-called Gondwanan fragments along the Tornquist margin to the southwest and the Timanian belt along the northeastern margin.

  14. Oxygen, ecology, and the Cambrian radiation of animals

    Science.gov (United States)

    Sperling, Erik A.; Frieder, Christina A.; Raman, Akkur V.; Girguis, Peter R.; Levin, Lisa A.; Knoll, Andrew H.

    2013-08-01

    The Proterozoic-Cambrian transition records the appearance of essentially all animal body plans (phyla), yet to date no single hypothesis adequately explains both the timing of the event and the evident increase in diversity and disparity. Ecological triggers focused on escalatory predator-prey "arms races" can explain the evolutionary pattern but not its timing, whereas environmental triggers, particularly ocean/atmosphere oxygenation, do the reverse. Using modern oxygen minimum zones as an analog for Proterozoic oceans, we explore the effect of low oxygen levels on the feeding ecology of polychaetes, the dominant macrofaunal animals in deep-sea sediments. Here we show that low oxygen is clearly linked to low proportions of carnivores in a community and low diversity of carnivorous taxa, whereas higher oxygen levels support more complex food webs. The recognition of a physiological control on carnivory therefore links environmental triggers and ecological drivers, providing an integrated explanation for both the pattern and timing of Cambrian animal radiation.

  15. An early Cambrian agglutinated tubular lophophorate with brachiopod characters

    Science.gov (United States)

    Zhang, Z.-F.; Li, G.-X.; Holmer, L. E.; Brock, G. A.; Balthasar, U.; Skovsted, C. B.; Fu, D.-J.; Zhang, X.-L.; Wang, H.-Z.; Butler, A.; Zhang, Z.-L.; Cao, C.-Q.; Han, J.; Liu, J.-N.; Shu, D.-G.

    2014-05-01

    The morphological disparity of lophotrochozoan phyla makes it difficult to predict the morphology of the last common ancestor. Only fossils of stem groups can help discover the morphological transitions that occurred along the roots of these phyla. Here, we describe a tubular fossil Yuganotheca elegans gen. et sp. nov. from the Cambrian (Stage 3) Chengjiang Lagerstätte (Yunnan, China) that exhibits an unusual combination of phoronid, brachiopod and tommotiid (Cambrian problematica) characters, notably a pair of agglutinated valves, enclosing a horseshoe-shaped lophophore, supported by a lower bipartite tubular attachment structure with a long pedicle with coelomic space. The terminal bulb of the pedicle provided anchorage in soft sediment. The discovery has important implications for the early evolution of lophotrochozoans, suggesting rooting of brachiopods into the sessile lophotrochozoans and the origination of their bivalved bauplan preceding the biomineralization of shell valves in crown brachiopods.

  16. A review of the Late Cambrian (Furongian) palaeogeography in the western Mediterranean region, NW Gondwana

    Science.gov (United States)

    Álvaro, J. Javier; Ferretti, Annalisa; González-Gómez, Cristina; Serpagli, Enrico; Tortello, M. Franco; Vecoli, Marco; Vizcaïno, Daniel

    2007-11-01

    The Cambrian-Ordovician transition of the western Mediterranean region (NW Gondwana) is characterized by the record of major erosive unconformities with gaps that range from a chronostratigraphic stage to a series. The hiatii are diachronous and involved progressively younger strata along the Gondwanan margin, from SW (Morocco) to NE (Montagne Noire). They can be related to development of a multi-stage rifting (further North), currently connected to the opening of the Rheic Ocean, and concomitant erosion on southern rift shoulders. The platforms of this margin of Gondwana occupied temperate-water, mid latitudes and were dominated by siliciclastic sedimentation, while carbonate factories were only episodically active in the Montagne-Noire platform. The Upper Cambrian is devoid of significant gaps in the southern Montagne Noire and the Iberian Chains. There, the sedimentation took place in a transgressive-dominated depositional system, with common offshore deposits and clayey substrates, and was bracketed by two major regressive trends. The Late Cambrian is also associated with the record of volcanic activity ( e.g., in the Cantabrian and Ossa-Morena zones, and the northern Montagne Noire), and widespread development of a tectonic instability that led to the episodic establishment of palaeotopographies and record of slope-related facies associations. Several immigration events are recognized throughout the latest Middle Cambrian, Late Cambrian and Tremadocian. The trilobites show a stepwise replacement of Acado-Baltic-type families ( e.g., the conocoryphid-paradoxidid-solenopleurid assemblage) characterized by: (i) a late Languedocian (latest Middle Cambrian) co-occurrence of Middle Cambrian trilobite families with the first anomocarid, dorypygid and proasaphiscid invaders; (ii) a Late Cambrian immigration replacing previous faunas, composed of trilobites (aphelaspidids, catillicephalids, ceratopygids, damesellids, eulomids, idahoiids, linchakephalids, lisariids

  17. Disparity, decimation and the Cambrian "explosion": comparison of early Cambrian and present faunal communities with emphasis on velvet worms (Onychophora).

    Science.gov (United States)

    Monge-Nájera, J; Hou, X

    2000-01-01

    structure was generalized during the Cambrian, and even biodiversity and equitability indices were surprisingly close to modern values; (2) the morphological diversity and geographic distribution of onychophorans indicate a significant pre-Cambrian evolutionary history which does not support the "explosion" hypothesis; (3) disparity among phyla was not as important as the explosion-decimation model predicts, but in the case of onychophorans, disparity within the phylum was greater than it is today and its reduction may have been associated with migration into the sediment when large predators evolved.

  18. The abnormal distribution of the molecular fossils in the pre-Cambrian and Cambrian: its biological significance

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes and C28 steranes for diatom. Therefore, the highest concentrations of these compounds are typically found in strata deposited since the beginning of the Mesozoic. However these compounds appeared widely and abundantly in extracts from organic-rich sediments in the Sinian and Cambrian of the Tarim Basin. This suggests that some of the planktonic algae such as dinoflagellates and diatoms have an earlier origin than the Mesozoic. Some of the remarkable algal fossils observed in the Cambrian, in both well He 4 and the outcrop section of Xiao-Er-Bulak, Tarim Basin, provide possible biological evidence for this kind of inference.

  19. Biogeochemical cycling through the Neoproterozoic-Cambrian transition in China: an integrated study of redox-sensitive elements

    OpenAIRE

    Och, L. M.

    2011-01-01

    I investigated changes in biogeochemical cycling during the Precambrian-Cambrian transition on the Yangtze Platform in South China by analyzing about 350 predominantly black shale samples from several sedimentary successions deposited during the interval from the Late Cryogenian to the Lower Cambrian. I focused on redox-sensitive trace-metal concentrations in these sediments, whereby special attention is paid to molybdenum, vanadium and uranium to try to pinpoint the onset of increasing atmos...

  20. Ichnofossil from the Cambrian succession of Parahio Valley, Spiti Basin, India: Their stratigraphic and paleoenvironmental significance

    Science.gov (United States)

    Pandey, Shivani; Parcha, Suraj Kumar

    2013-04-01

    The Spiti Basin exposes an excellent section of Neoproterozoic- Cretaceous rocks in the Tethyan Himalaya of Himachal Pradesh. The diverse assemblage of ichnofossils is present in the Cambrian succession of Parahio Valley in the Spiti Basin. In the present study nineteen ichnofossils are reported from the Cambrian succession of Parahio Valley. The ichnofossils includes Bergaueria, Chondrites, Cruziana, Didymaulichnus, Dimorphichnus, Diplichnites, Helminthorhaphe, Merostomichnites, ?Monocraterion, Monomorphichnus, Nereites, Palaeopascichnus, Palaeophycus, Phycodes, Planolites, Rusophycus, Skolithos, Scolicia, Treptichnus etc. along with annelid worm, burrow and scratch marks. The described ichnofossil assemblage indicates that the ichnocenosis is dominated by a high behavioral diversity ranging from suspension to deposit feeders. It seems that the ichnofauna present in the Cambrian succession of this section were mostly produced by trilobite and arthropods, whereas some of them were produced by crustacean, priapulid worm, polychaetes and polyphyletic vermiforms. The distribution pattern of ichnofossils shows increase in taxonomic and morphological diversity up in the section. It further indicates that the availability of nutrients significantly increased their abundance as well as spatial distribution during Cambrian. The presence of Chondrites, Treptichnus, and Phycodes at the basal part of the Cambrian indicates shallow to deep environment with anaerobic condition. Whereas, the complex forms like Rusophycus, Cruziana, Monomorphichnus and Nereites represent shelf to slope environment. The appearance of Skolithos in the upper part reflects well oxygenated high energy condition. The environmental changes in the Parahio Valley during Cambrian period was distinctly marked by an anaerobic to aerobic condition and by a faunal change from endobenthic, soft - bodied, deposit feeders to epibenthic grazers. The present ichnofossils indicates that these sediments were

  1. Nonbiomineralized carapaces in Cambrian seafloor landscapes (Sirius Passet, Greenland)

    DEFF Research Database (Denmark)

    Mangano, M. Gabriela; Bromley, Richard Granville; Harper, David A.T.

    2012-01-01

    -caliber structures with dendritic terminations, and annulated burrows are abundant in the Early Cambrian Sirius Basset Lagerstatte (Greenland). Taphonomic controls were partially responsible for the pronounced association of these structures and carapaces, but ecologic conditions are envisioned as playing...... of nonbiomineralized organisms may have acted as attractors, supporting a community of small invertebrates. Carapaces created a sharp boundary, further decreasing oxygen diffusion into the sediment. This steep oxygen gradient at the organic surface of the carapace promoted the growth of sulfur bacteria that could have...

  2. The Ecology of the Cambrian Radiation

    Science.gov (United States)

    Briggs, Derek E. G.

    The Cambrian radiation is one of the most exciting and controversial events in the fossil record. It was marked by a sudden abundance of shells, the first steep rise in plots of diversity through time, and the appearance of the fabulous soft-bodied fossils of the Burgess Shale in British Columbia and elsewhere in the world. The Cambrian radiation was also the subject of Steve Gould's Wonderful Life and Simon Conway Morris's Crucible of Creation.. The Ecology of the Cambrian Radiation is a long-awaited compilation that tackles one of the more impenetrable parts of the story. Interpretations of ecology are, after all, characteristically equivocal in rocks of this age.

  3. Stratigraphical and biological significance of negative carbon isotopic anomalies in the basal Cambrian series of Guizhou Province

    Institute of Scientific and Technical Information of China (English)

    YANG Ruidong; WANG Shijie; OUYANG Ziyuan; ZHU Lijun; JIANG Lijun; ZHANG Weihua; GAO Hui

    2005-01-01

    The early Early Cambrian strata within the bounds of Guizhou Province are almost predominated by black shale deposition. Recently, however, the authors have found a section consisting of a set of mudstones interbedded with limestones at the basement of the Cambrian at Yingping, Fuquan County, Guizhou Province, which provides favorable conditions for the study of marine geochemical characteristics of the early Early Cambrian. The characteristics of intense negative carbon isotopic anomalies near the Precambrian/Cambrian boundary at Yingping, Fuquan County, Guizhou Province, can be correlated with those of global carbon isotopic anomalies at the same time on a global scale, corresponding to the intense negative carbon isotopic anomalies near the Neoproterozoic/Cambrian boundaries at the bottom of the Xiaowaitoushan Member, Huize, Yunnan Province, at the top of the Tsagaan Oloom Formation of Mongolia and at the top of the Salarmy Gol Formation of Siberia, as well as those observed in southwestern United States, Iran, Amman, Poland, Newfoundland, the Great Britain, Canada, etc. Negative carbon isotopic anomalies can be used as the important basis for the division of the Precambrian/Cambrian boundaries. There have been found 8 m-thick black shales and cherts below the intense negative carbon isotopic anomalies in this profile. In the black shales there have been found large amounts of fossils such as Bradorida, gernus Archotuba, indicating that during the period of sedimentation of black shales under anaerobic conditions there would be large quantities of organic species living in the sea. But in the section of grayish-green mudstones interbedded with limestones with intense negative carbon isotopic anomalies almost no organic fossil has been found. This may imply that the anaerobic event seems to have little bearing on the mass extinction near the Precambrian/Cambrian boundary, whereas the intense negative carbon isotopic anomaly event appears to be more closely

  4. The Stratigraphy of the Cambrian Lancara Formation between the Luna River and the Esla River in the Cantabrian Mountains, Spain

    NARCIS (Netherlands)

    Meer Mohr, van der C.G.

    1969-01-01

    The Lancara Formation is a unit of carbonate sediments of Lower to Middle Cambrian age in the Cantabrian Mountains of northern Spain. The formation is divisible into a Dolomite Member, a Limestone Member and a Griotte Member. The Dolomite Member and the Limestone Member consist mainly of very shallo

  5. Succession of Cambrian conodonts from South China

    Institute of Scientific and Technical Information of China (English)

    董熙平

    2000-01-01

    More than 4 200 kg, the total weight, of 980 productive conodont samples mainly from four key sections in western Hunan and northwestern Hunan, South China have been processed. It is found that the paraconodonts occurring below Fengshanian (upper Upper Cambrian) may be used for stratigraphic subdivision and correlation. Accordingly, eight conodont zones ranging from upper Middle Cambrian to upper Upper Cambrian in South China are erected for the first time. The correlation between these zones and those of North China, North America and Iran is discussed. These eight zones are in ascending order as follows:Gapparodus bisulcatus-Westergaardodina brevidens zone, Shandongodus priscus-Hunano-gnathus tricuspidatus zone, Westergaardodina quadrata zone, Westergaardodina matsushitai-W. grandidens zone, Westergaardodina proligula zone, Westergaardodina cf. behrae-Prooneotodus rotundatus zone, Proconodontus zone, Cordylodus proavus zone.

  6. Succession of Cambrian conodonts from South China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    More than 4200 kg, the total weight, of 980 productive conodont samples mainly from four key sections in western Hunan and northwestern Hunan, South China have been processed. It is found that the paraconodonts occurring below Fengshanian (upper Upper Cambrian) may be used for stratigraphic subdivision and correlation. Accordingly, eight conodont zones ranging from upper Middle Cambrian to upper Upper Cambrian in South China are erected for the first time. The correlation between these zones and those of North China, North America and Iran is discussed. These eight zones are in ascending order as follows:Gapparodus bisulcatus-Westergaardodina brevidens zone, Shandongodus priscus-Hunano- gnathus tricuspidatus zone, Westergaardodina quadrata zone, Westergaardodina matsushitai-W. grandidens zone, Westergaardodina proligula zone, Westergaardodina cf. behrae-Prooneotodus rotundatus zone, Proconodontus zone, Cordylodus proavus zone.

  7. Possible impact event in the Late Cambrian

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The repeated investigation of the Batyrbay section has been done by the authors. Today we see increasing of interest to revising of volumes and boundaries of Stages and Series in the Cambrian and Ordovician,as well as to the events of this time. In this work the description of iron spherules and particles, found in the deep-water limestone layer of the conodont Cordylodus primitivus Zone in the middle Upper Cambrian of the Batyrbay section, Malyi Karatau of South Kazakhstan, and formed during the time of global sea-level changes known as a world-wide Lange Ranch Eustatic event, have been done. From our point of view, finds of iron spherules and particles may evidence about new unknown yet Event of cosmic origin, i.e. falling of a meteorite on Earth in the middle Late Cambrian.

  8. Gut contents as direct indicators for trophic relationships in the Cambrian marine ecosystem.

    Science.gov (United States)

    Vannier, Jean

    2012-01-01

    Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut contents of Ottoia prolifica, an abundant priapulid worm from the middle Cambrian (Stage 5) Burgess Shale biota. I identify the undigested exoskeletal remains of a wide range of small invertebrates that lived at or near the water sediment interface such as hyolithids, brachiopods, different types of arthropods, polychaetes and wiwaxiids. This set of direct fossil evidence allows the first detailed reconstruction of the diet of a 505-million-year-old animal. Ottoia was a dietary generalist and had no strict feeding regime. It fed on both living individuals and decaying organic matter present in its habitat. The feeding behavior of Ottoia was remarkably simple, reduced to the transit of food through an eversible pharynx and a tubular gut with limited physical breakdown and no storage. The recognition of generalist feeding strategies, exemplified by Ottoia, reveals key-aspects of modern-style trophic complexity in the immediate aftermath of the Cambrian explosion. It also shows that the middle Cambrian ecosystem was already too complex to be understood in terms of simple linear dynamics and unique pathways.

  9. Gut contents as direct indicators for trophic relationships in the Cambrian marine ecosystem.

    Directory of Open Access Journals (Sweden)

    Jean Vannier

    Full Text Available Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut contents of Ottoia prolifica, an abundant priapulid worm from the middle Cambrian (Stage 5 Burgess Shale biota. I identify the undigested exoskeletal remains of a wide range of small invertebrates that lived at or near the water sediment interface such as hyolithids, brachiopods, different types of arthropods, polychaetes and wiwaxiids. This set of direct fossil evidence allows the first detailed reconstruction of the diet of a 505-million-year-old animal. Ottoia was a dietary generalist and had no strict feeding regime. It fed on both living individuals and decaying organic matter present in its habitat. The feeding behavior of Ottoia was remarkably simple, reduced to the transit of food through an eversible pharynx and a tubular gut with limited physical breakdown and no storage. The recognition of generalist feeding strategies, exemplified by Ottoia, reveals key-aspects of modern-style trophic complexity in the immediate aftermath of the Cambrian explosion. It also shows that the middle Cambrian ecosystem was already too complex to be understood in terms of simple linear dynamics and unique pathways.

  10. The significance of 24-norcholestanes, triaromatic steroids and dinosteroids in oils and Cambrian-Ordovician source rocks from the cratonic region of the Tarim Basin, NW China

    Science.gov (United States)

    Li, Meijun; Wang, T.-G.; Lillis, Paul G.; Wang, Chunjiang; Shi, Shengbao

    2012-01-01

    Two oil families in Ordovician reservoirs from the cratonic region of the Tarim Basin are distinguished by the distribution of regular steranes, triaromatic steroids, norcholestanes and dinosteroids. Oils with relatively lower contents of C28 regular steranes, C26 20S, C26 20R + C27 20S and C27 20R regular triaromatic steroids, dinosteranes, 24-norcholestanes and triaromatic dinosteroids originated from Middle–Upper Ordovician source rocks. In contrast, oils with abnormally high abundances of the above compounds are derived from Cambrian and Lower Ordovician source rocks. Only a few oils have previously been reported to be of Cambrian and Lower Ordovician origin, especially in the east region of the Tarim Basin. This study further reports the discovery of oil accumulations of Cambrian and Lower Ordovician origin in the Tabei and Tazhong Uplifts, which indicates a potential for further discoveries involving Cambrian and Lower Ordovician sourced oils in the Tarim Basin. Dinosteroids in petroleum and ancient sediments are generally thought to be biomarkers for dinoflagellates and 24-norcholestanes for dinoflagellates and diatoms. Therefore, the abnormally high abundance of these compounds in extracts from the organic-rich sediments in the Cambrian and Lower Ordovician and related oils in the cratonic region of the Tarim Basin suggests that phytoplankton algae related to dinoflagellates have appeared and might have flourished in the Tarim Basin during the Cambrian Period. Steroids with less common structural configurations are underutilized and can expand understanding of the early development history of organisms, as well as define petroleum systems.

  11. Cambrian Research in the New Century—the Fourth International Symposium on the Cambrian System

    Institute of Scientific and Technical Information of China (English)

    Peng Shanchi; Zhu Maoyan; L.E.Babcock

    2006-01-01

    @@ The International Subcomission on Cambrian Stratigraphy (ISCS) of the International Commission on Stratigraphy (ICS)held its Fourth International Symposium on the Cambrian System in Nanjing, the capital city of Jiangsu Province, China, on 18-24August, 2005. The Symposium was held in conjunction with the Tenth Field Conference of the Cambrian Stage Subdivision Working Group of the ISCS. Technical sessions were held in the conference center of Southeast University, and hosted by the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, the Geological Institute, Chinese Academy of Geological Sciences, and Guizhou University. Associated with the meeting were five field excursions to classical Cambrian localities in North China and South China.

  12. Upper Cambrian (Furongian) biostratigraphy in Scandinavia revisited

    DEFF Research Database (Denmark)

    Nielsen, Arne Thorshøj; Weidner, Thomas; Terfelt, Fredrik;

    2014-01-01

    The traditional Furongian trilobite biozones of Scandinavia, recently proposed abandoned due to inconsistent boundary definitions [Terfelt, F., Eriksson, M.E., Ahlberg, P. & Babcock, L.E., 2008: Furongian Series (Cambrian) biostratigraphy of Scandinavia – a revision. Norwegian Journal of Geology8...

  13. Exceptional fossil preservation and the cambrian explosion.

    Science.gov (United States)

    Butterfield, Nicholas J

    2003-02-01

    Exceptionally preserved, non-biomineralizing fossils contribute importantly to resolving details of the Cambrian explosion, but little to its overall patterns. Six distinct "types" of exceptional preservation are identified for the terminal Proterozoic-Cambrian interval, each of which is dependent on particular taphonomic circumstances, typically restricted both in space and time. Taphonomic pathways yielding exceptional preservation were particularly variable through the Proterozoic-Cambrian transition, at least in part a consequence of contemporaneous evolutionary innovations. Combined with the reasonably continuous record of "Doushantuo-type preservation," and the fundamentally more robust records of shelly fossils, phytoplankton cysts and trace fossils, these taphonomic perturbations contribute to the documentation of major evolutionary and biogeochemical shifts through the terminal Proterozoic and early Cambrian.Appreciation of the relationship between taphonomic pathway and fossil expression serves as a useful tool for interpreting exceptionally preserved, often problematic, early Cambrian fossils. In shale facies, for example, flattened non-biomineralizing structures typically represent the remains of degradation-resistant acellular and extracellular "tissues" such as chaetae and cuticles, whereas three-dimensional preservation represents labile cellular tissues with a propensity for attracting and precipitating early diagenetic minerals. Such distinction helps to identify the acuticular integument of hyolithids, the chaetae-like nature of Wiwaxia sclerites, the chaetognath-like integument of Amiskwia, the midgut glands of various Burgess Shale arthropods, and the misidentification of deposit-feeding arthropods in the Chengjiang biota. By the same reasoning, putative lobopods in the Sirius Passet biota and putative deuterostomes in the Chengiang biota are better interpreted as arthropods.

  14. Plankton from Early Cambrian black shale series on the Yangtze Platform, and its influences on lithologies

    Institute of Scientific and Technical Information of China (English)

    Andreas BRAUN; CHEN Junyuan

    2003-01-01

    Black shales, cherts, and associated lithologies in the Early Cambrian of the Yangtze Platform yielded abundant phytoplankton, the earliest well preserved skeletons of zooplankton (radiolarians) and abundant phosphatic ovoid bodies, probably representing fecal pellets, produced by Mesozooplankton grazing on phytoplankton. The oceanic food chain in surface waters is therefore considered to be more complete than known up to now with respect to primary and secondary consumers in the Early Cambrian plankton ecosystem. On the basis of primary sedimentary compositions preserved in phosphorite concretions and chert layers it is shown that biosiliceous sedimentation mixed with organic substance played a significant role within the black shale sequence of the Hetang and Niutitang formations. The resulting lithology corresponds closely in character to the bituminous Alum-shale and Lydite-sequences of Lower Silurian (Llandoverian) age along northern Gondwana (e.g. Thuringia, Bohemia).

  15. Early Cambrian sipunculan worms from southwest China.

    Science.gov (United States)

    Huang, Di-Ying; Chen, Jun-Yuan; Vannier, Jean; Saiz Salinas, J I

    2004-08-22

    We report the discovery of sipunculan worms from the Lower Cambrian Maotianshan Shale, near Kunming (southwest China). Their sipunculan identity is evidenced by the general morphology of the animals (sausage-shaped body with a slender retractable introvert and a wider trunk) and by other features, both external (e.g. perioral crown of tentacles, and hooks, papillae and wrinkle rings on the body surface) and internal (U-shaped gut, and the anus opening near the introvert-trunk junction). The three fossil forms (Archaeogolfingia caudata gen. et sp. nov., Cambrosipunculus tentaculatus gen. et sp. nov. and Cambrosipunculus sp.) have striking similarities to modern sipunculans, especially the Golfingiidae to which their evolutionary relationships are discussed. This study suggests that most typical features of extant sipunculans have undergone only limited changes since the Early Cambrian, thus indicating a possible evolutionary stasis over the past 520 Myr.

  16. Burgess shale faunas and the cambrian explosion.

    Science.gov (United States)

    Morris, S C

    1989-10-20

    Soft-bodied marine faunas from the Lower and Middle Cambrian, exemplified by the Burgess Shale of British Columbia, are a key component in understanding the major adaptive radiations at the beginning of the Phanerozoic ("Cambrian explosion"). These faunas have a widespread distribution, and many taxa have pronounced longevity. Among the components appear to be survivors of the preceding Ediacaran assemblages and a suite of bizarre forms that give unexpected insights into morphological diversification. Microevolutionary processes, however, seem adequate to account for this radiation, and the macroevolutionary patterns that set the seal on Phanerozoic life are contingent on random extinctions. They weeded out the morphological spectrum and permitted rediversification among surviving clades. Although the predictability of which clades will play in successive acts of the Phanerozoic theater is low, at least the outlines of the underlying ecological plot are already clear from the opening of the drama.

  17. Developmental sequence of Cambrian embryo Markuelia

    Institute of Scientific and Technical Information of China (English)

    DONG XiPing

    2007-01-01

    Based on more exquisitely preserved specimens of Markuelia hunanensis recently recovered from Middle and Upper Cambrian in western Hunan and in the light of Synchrotron radiation X-ray tomographic microscopy, the developmental sequence from cleavage through organogenesis to the pre-hatching of Cambrian embryo Markuelia, especially the developmental sequence during the pre-hatching stage, i.e. from the earliest period when the scalids and tail spines only took shape to the latest period (just about hatching), is established. This developmental sequence provides a pattern of embryonic development during the pre-hatching stage, which has not been established in the living scalidophorans (priapulids, Ioriciferans and kinorhynchs). Thus, it not only enriches our knowledge on the embryonic development of the extant descendants of Markuelia, but also opens a new window to the evolution and development of the animal.

  18. Cambrian problematica and the diversification of deuterostomes

    Directory of Open Access Journals (Sweden)

    Smith Andrew B

    2012-10-01

    Full Text Available Abstract Vetulicolians are an enigmatic group of Cambrian organisms that have been affiliated at various times with arthropods, lobopodians, kinorhynchs and deuterostomes. New evidence on the structure of the lateral pores of vetulicolians published in BMC Biology strengthens the view that they may be total group deuterostomes, but unfortunately sheds no new light on early deuterostome evolution. See research article http://www.biomedcentral.com/1741-7007/10/81

  19. Tubicolous enteropneusts from the Cambrian period.

    Science.gov (United States)

    Caron, Jean-Bernard; Morris, Simon Conway; Cameron, Christopher B

    2013-03-28

    Hemichordates are a marine group that, apart from one monospecific pelagic larval form, are represented by the vermiform enteropneusts and minute colonial tube-dwelling pterobranchs. Together with echinoderms, they comprise the clade Ambulacraria. Despite their restricted diversity, hemichordates provide important insights into early deuterostome evolution, notably because of their pharyngeal gill slits. Hemichordate phylogeny has long remained problematic, not least because the nature of any transitional form that might serve to link the anatomically disparate enteropneusts and pterobranchs is conjectural. Hence, inter-relationships have also remained controversial. For example, pterobranchs have sometimes been compared to ancestral echinoderms. Molecular data identify enteropneusts as paraphyletic, and harrimaniids as the sister group of pterobranchs. Recent molecular phylogenies suggest that enteropneusts are probably basal within hemichordates, contrary to previous views, but otherwise provide little guidance as to the nature of the primitive hemichordate. In addition, the hemichordate fossil record is almost entirely restricted to peridermal skeletons of pterobranchs, notably graptolites. Owing to their low preservational potentials, fossil enteropneusts are exceedingly rare, and throw no light on either hemichordate phylogeny or the proposed harrimaniid-pterobranch transition. Here we describe an enteropneust, Spartobranchus tenuis (Walcott, 1911), from the Middle Cambrian-period (Series 3, Stage 5) Burgess Shale. It is remarkably similar to the extant harrimaniids, but differs from all known enteropneusts in that it is associated with a fibrous tube that is sometimes branched. We suggest that this is the precursor of the pterobranch periderm, and supports the hypothesis that pterobranchs are miniaturized and derived from an enteropneust-like worm. It also shows that the periderm was acquired before size reduction and acquisition of feeding tentacles, and

  20. Did gamma ray burst induce Cambrian explosion?

    Science.gov (United States)

    Chen, Pisin; Ruffini, R.

    2015-06-01

    One longstanding mystery in bio-evolution since Darwin's time is the origin of the Cambrian explosion that happened around 540 million years ago (Mya), where an extremely rapid increase of species occurred. Here we suggest that a nearby GRB event 500 parsecs away, which should occur about once per 5 Gy, might have triggered the Cambrian explosion. Due to a relatively lower cross section and the conservation of photon number in Compton scattering, a substantial fraction of the GRB photons can reach the sea level and would induce DNA mutations in organisms protected by a shallow layer of water or soil, thus expediting the bio-diversification. This possibility of inducing genetic mutations is unique among all candidate sources for major incidents in the history of bio-evolution. A possible evidence would be the anomalous abundance of certain nuclear isotopes with long half-lives transmuted by the GRB photons in geological records from the Cambrian period. Our notion also imposes constraints on the evolution of exoplanet organisms and the migration of panspermia.

  1. Did Gamma Ray Burst Induce Cambrian Explosion?

    CERN Document Server

    Chen, Pisin

    2014-01-01

    One longstanding mystery in bio-evolution since Darwin's time is the origin of the Cambrian explosion that happened around 540 million years ago (Mya), where an extremely rapid increase of species occurred. Here we suggest that a nearby GRB event ~500 parsecs away, which should occur about once per 5 Gy, might have triggered the Cambrian explosion. Due to a relatively lower cross section and the conservation of photon number in Compton scattering, a substantial fraction of the GRB photons can reach the sea level and would induce DNA mutations in organisms protected by a shallow layer of water or soil, thus expediting the bio-diversification. This possibility of inducing genetic mutations is unique among all candidate sources for major incidents in the history of bio-evolution. A possible evidence would be the anomalous abundance of certain nuclear isotopes with long half-lives transmuted by the GRB photons in geological records from the Cambrian period. Our notion also imposes constraints on the evolution of ...

  2. Oxygen Requirements for the Cambrian Explosion

    Institute of Scientific and Technical Information of China (English)

    Xingliang Zhang; Linhao Cui

    2016-01-01

    Hypoxic tolerance experiments may be helpful to constrain the oxygen requirement for animal evolution. Based on literature review, available data demonstrate that fishes are more sensitive to hypoxia than crustaceans and echinoderms, which in turn are more sensitive than annelids, whilst mollusks are the least sensitive. Mortalities occur where O2 concentrations are below 2.0 mg/L, equivalent to saturation with oxygen content about 25% PAL (present atmospheric level). Therefore, the minimal oxygen requirement for maintaining animal diversity since Cambrian is determined as 25% PAL. The traditional view is that a rise in atmospheric oxygen concentrations led to the oxygenation of the ocean, thus triggering the evolution of animals. Geological and geochemical studies suggest a constant increase of the oxygen level and a contraction of anoxic oceans during Ediacaran–Cambrian transition when the world oceans experienced a rapid diversification of metazoan lineages. However, fossil first appearances of animal phyla are obviously asynchronous and episodic, showing a sequence as:basal metazoans>lophotrochozoans>ecdysozoans and deuterostomes. According to hitherto known data of fossil record and hypoxic sensitivity of animals, the appearance sequence of different animals is broadly consistent with their hypoxic sensitivity:animals like molluscs and annelids that are less sensitive to hypoxia appeared earlier, while animals like echinoderms and fishes that are more sensitive to hypoxia came later. Therefore, it is very likely that the appearance order of animals is corresponding to the increasing oxygen level and/or the contraction of anoxic oceans during Ediacaran–Cambrian transition.

  3. Cambrian bivalved arthropod reveals origin of arthrodization.

    Science.gov (United States)

    Legg, David A; Sutton, Mark D; Edgecombe, Gregory D; Caron, Jean-Bernard

    2012-12-07

    Extant arthropods are diverse and ubiquitous, forming a major constituent of most modern ecosystems. Evidence from early Palaeozoic Konservat Lagerstätten indicates that this has been the case since the Cambrian. Despite this, the details of arthropod origins remain obscure, although most hypotheses regard the first arthropods as benthic predators or scavengers such as the fuxianhuiids or megacheirans ('great-appendage' arthropods). Here, we describe a new arthropod from the Tulip Beds locality of the Burgess Shale Formation (Cambrian, series 3, stage 5) that possesses a weakly sclerotized thorax with filamentous appendages, encased in a bivalved carapace, and a strongly sclerotized, elongate abdomen and telson. A cladistic analysis resolved this taxon as the basal-most member of a paraphyletic grade of nekto-benthic forms with bivalved carapaces. This grade occurs at the base of Arthropoda (panarthropods with arthropodized trunk limbs) and suggests that arthrodization (sclerotization and jointing of the exoskeleton) evolved to facilitate swimming. Predatory and fully benthic habits evolved later in the euarthropod stem-lineage and are plesiomorphically retained in pycnogonids (sea spiders) and euchelicerates (horseshoe crabs and arachnids).

  4. Diachronism in the late Neoproterozoic-Cambrian arc-rift transition of North Gondwana: A comparison of Morocco and the Iberian Ossa-Morena Zone

    Science.gov (United States)

    Álvaro, J. Javier; Bellido, Félix; Gasquet, Dominique; Pereira, M. Francisco; Quesada, Cecilio; Sánchez-García, Teresa

    2014-10-01

    In the northwestern border of the West African craton (North Gondwana), a transition from late Neoproterozoic subduction/collision to Cambrian rift processes was recorded in the Anti-Atlas (Morocco) and in the Ossa-Morena Zone (Iberia). Cambrian rifting affected both Pan-African and Cadomian basements in a stepwise and diachronous way. Subsequently, both areas evolved into a syn-rift margin episodically punctuated by uplift and tilting that precluded Furongian sedimentation. A comparison of sedimentary, volcanic and geodynamic evolution is made in the late Neoproterozoic (Pan-African and Cadomian) belts and Cambrian rifts trying to solve the apparent diachronous (SW-NE-trending) propagation of an early Palaeozoic rifting regime that finally led to the opening of the Rheic Ocean.

  5. Cambrian to Lower Ordovician complexes of the Kokchetav Massif and its fringing (Northern Kazakhstan): Structure, age, and tectonic settings

    Science.gov (United States)

    Degtyarev, K. E.; Tolmacheva, T. Yu.; Tretyakov, A. A.; Kotov, A. B.; Shatagin, K. N.

    2016-01-01

    A comprehensive study of the Lower Palaeozoic complexes of the Kokchetav Massif and its fringing has been carried out. It has allowed for the first time to discover and investigate in detail the stratified and intrusive complexes of the Cambrian-Early Ordovician. Fossil findings and isotope geochronology permitted the determination of their ages. The tectonic position and internal structures of those complexes have also been defined and their chemical features have been analyzed as well. The obtained data allowed us to put forward a model of the geodynamic evolution of Northern Kazakhstan in the Late Ediacaran-Earliest Ordovician. The accumulation of the oldest Ediacaran to Earliest Cambrian siliciclastics and carbonates confined to the Kokchetav Massif and its fringing occurred in a shallow shelf environment prior to its collision with the Neoproterozoic Daut island arc: complexes of the latter have been found in the northeast of the studied area. The Early Cambrian subduction of the Kokchetav Massif under the Daut island arc, their following collision and exhumation of HP complexes led to the formation of rugged ground topography, promoting deposition of siliceous-clastic and coarse clastic units during the Middle to early Late Cambrian. Those sediments were mainly sourced from eroded metamorphic complexes of the Kokchetav Massif basement. At the end of the Late Cambrian to the Early Ordovician within the boundaries of the massif with the Precambrian crust, volcanogenic and volcano-sedimentary units along with gabbros and granites with intraplate affinities were formed. Simultaneously in the surrounding zones, which represent relics of basins with oceanic crust, N-MORB- and E-MORB-type ophiolites were developed. These complexes originated under extensional settings occurred in the majority of the Caledonides of Kazakhstan and Northern Tian Shan. In the Early Floian Stage (Early Ordovician) older heterogeneous complexes were overlain by relatively monotonous

  6. The late Neoproterozoic to early Cambrian sulphur cycle: an isotopic investigation of sedimentary rocks from the Yangtze platform

    Science.gov (United States)

    Goldberg, T.; Strauss, H.

    2003-04-01

    The sulphur cycle responds to changes in seawater chemistry, biological evolution and tectonic activity. We follow an isotopic approach in order to constrain the state of the ocean/atmosphere system during the late Neoproterozoic and early Cambrian. For this purpose, sedimentary successions from the Yangtze platform, South China, were analysed for their sulphur isotopic composition in different S-bearing phases. The general stratigraphy comprises in ascending order the Doushantuo, Dengying and Niutitang formations. Main lithologies include carbonates, phosphorites, black shales and cherts. The sulphur isotopic composition of the late Neoproterozoic to early Cambrian seawater sulphate ranges from +30 to +35 ‰ as evident from calcium sulphates and trace sulphate in unaltered carbonates and phosphorites (Shields et al., 1999). Sulphur isotopes in chromium reducible and organically bound sulphur are displaced by about +40 ‰ from the seawater sulphate signal, indicating bacterial sulphate reduction. Isotope values range between -16 and +25 ‰ reflecting different environmental conditions, varying from open to closed/limiting conditions in respect to sulphate availability. Pyrite morphology is studied in order to characterize the diagenetic environment. Consistent with a biological origin for the sedimentary pyrite in the Neoproterozoic as well as in the Cambrian (Strauss, 2002) is the positive correlation between sulphide sulphur and organic carbon abundances. The availability of reactive iron is evaluated by means of the degree of pyritization (Raiswell et al., 1988). Raiswell, R. Buckley, F., Berner, R. &Anderson, T. (1988) Degree of pyritization of iron as a paleoenvironmental indicator of bottom-water oxygenation. Journal of Sedimentary Petrology, 58, No.5, 812-819 Shields, G., Strauss, H., Howe, S. &Siegmund, H. (1999) Sulphur isotope composition of sedimentary phosphorites from the basal Cambrian of China: implications for Neoproterozoic-Cambrian biochemical

  7. Cambrian-lower Middle Ordovician passive carbonate margin, southern Appalachians: Chapter 14

    Science.gov (United States)

    Read, J. Fred; Repetski, John E.

    2012-01-01

    The southern Appalachian part of the Cambrian–Ordovician passive margin succession of the great American carbonate bank extends from the Lower Cambrian to the lower Middle Ordovician, is as much as 3.5 km (2.2 mi) thick, and has long-term subsidence rates exceeding 5 cm (2 in.)/k.y. Subsiding depocenters separated by arches controlled sediment thickness. The succession consists of five supersequences, each of which contains several third-order sequences, and numerous meter-scale parasequences. Siliciclastic-prone supersequence 1 (Lower Cambrian Chilhowee Group fluvial rift clastics grading up into shelf siliciclastics) underlies the passive margin carbonates. Supersequence 2 consists of the Lower Cambrian Shady Dolomite–Rome-Waynesboro Formations. This is a shallowing-upward ramp succession of thinly bedded to nodular lime mudstones up into carbonate mud-mound facies, overlain by lowstand quartzose carbonates, and then a rimmed shelf succession capped by highly cyclic regressive carbonates and red beds (Rome-Waynesboro Formations). Foreslope facies include megabreccias, grainstone, and thin-bedded carbonate turbidites and deep-water rhythmites. Supersequence 3 rests on a major unconformity and consists of a Middle Cambrian differentiated rimmed shelf carbonate with highly cyclic facies (Elbrook Formation) extending in from the rim and passing via an oolitic ramp into a large structurally controlled intrashelf basin (Conasauga Shale). Filling of the intrashelf basin caused widespread deposition of thin quartz sandstones at the base of supersequence 4, overlain by widespread cyclic carbonates (Upper Cambrian lower Knox Group Copper Ridge Dolomite in the south; Conococheague Formation in the north). Supersequence 5 (Lower Ordovician upper Knox in the south; Lower to Middle Ordovician Beekmantown Group in the north) has a basal quartz sandstone-prone unit, overlain by cyclic ramp carbonates, that grade downdip into thrombolite grainstone and then storm

  8. Early Cambrian wave-formed shoreline deposits: the Hardeberga Formation, Bornholm, Denmark

    Science.gov (United States)

    Clemmensen, Lars B.; Glad, Aslaug C.; Pedersen, Gunver K.

    2016-09-01

    During the early Cambrian, the Danish island Bornholm was situated on the northern edge of the continent Baltica with palaeolatitudes of about 35°S. An early Cambrian (Terreneuvian) transgression inundated large areas of Baltica including Bornholm creating shallow marine and coastline environments. During this period, wave-formed shoreline sediments (the Vik Member, Hardeberga Formation) were deposited on Bornholm and are presently exposed at Strøby quarry. The sediments consist of fine- and medium-grained quartz-cemented arenites in association with a few silt-rich mudstones. The presence of well-preserved subaqueous dunes and wave ripples indicates deposition in a wave-dominated upper shoreface (littoral zone) environment, and the presence of interference ripples indicates that the littoral zone environment experienced water level fluctuations due to tides and/or changing meteorological conditions. Discoidal structures (medusoids) are present in the quarry, but due to the relative poor preservation of their fine-scale structures it is difficult to determine if the discoids represent true medusae imprints or inorganic structures. The preservation of the shallow-water bedforms as well as the possible medusae imprints is related to either the formation of thin mud layers, formed during a period of calm water when winds blew offshore for a longer period, or to the growth of bacterial mats. The orientation of the wave-formed bedforms indicates a local palaeoshoreline trending NE-SW and facing a large ocean to the north.

  9. Diagenetic and Catagenetic Transference of Noble Metal Elements in Lower Cambrian Black Rock Series, Southwest China

    Institute of Scientific and Technical Information of China (English)

    Li Shengrong; Gao Zhenmin; Shen Junfeng

    2004-01-01

    Some extraditional types-black rock series types of platinum group element (PGE), gold and silver mineralization occurrences were found in the Lower Cambrian in Guizhou and Hunan provinces of southwest China where PGE concentration reaches more than 800×10-6. Sea floor hydrothermal fluid eruption was suggested to have been the main origin of the ore-forming materials. The whole process from the sedimentation to the redistribution of the ore-forming elements occurred on the conditions of intermediate to weak alkaline, weak reduction to weak oxidation. The temperature for the sedimentation and redistribution of the ore-forming elements was lower than 210 ℃. At such a low temperature, inert elements such as PGE, Au and Ag could quite easily be remobilized.

  10. Geochemical evidence for widespread euxinia in the Later Cambrian ocean

    OpenAIRE

    2011-01-01

    Widespread anoxia in the ocean is frequently invoked as a primary driver of mass extinction as well as a long-term inhibitor of evolutionary radiation on early Earth. In recent biogeochemical studies it has been hypothesized that oxygen deficiency was widespread in subsurface water masses of later Cambrian oceans1, 2, possibly influencing evolutionary events during this time1, 2, 3. Physical evidence of widespread anoxia in Cambrian oceans has remained elusive and thus its potential relations...

  11. Global standard names for the Lowermost Cambrian Series and Stage

    Institute of Scientific and Technical Information of China (English)

    Ed Landing; Shanchi Peng; Loren E.Babcock; Gerd Geyer; Malgorzata Moczydlowska-Vidal

    2007-01-01

    @@ The GSSP marking the base of the Cambrian System was ratified by the IUGS in 1992.Ratification of the GSSP point at the base of the Trichophycus pedum Ichnozone in the Fortune Head section,eastern Newfoundland,Canada,automatically defined the conterminant base of the lowermost series and stage of the Cambrian although names for those subdivisions were not proposed at the time of the decision.

  12. Primitive soft-bodied cephalopods from the Cambrian.

    Science.gov (United States)

    Smith, Martin R; Caron, Jean-Bernard

    2010-05-27

    The exquisite preservation of soft-bodied animals in Burgess Shale-type deposits provides important clues into the early evolution of body plans that emerged during the Cambrian explosion. Until now, such deposits have remained silent regarding the early evolution of extant molluscan lineages-in particular the cephalopods. Nautiloids, traditionally considered basal within the cephalopods, are generally depicted as evolving from a creeping Cambrian ancestor whose dorsal shell afforded protection and buoyancy. Although nautiloid-like shells occur from the Late Cambrian onwards, the fossil record provides little constraint on this model, or indeed on the early evolution of cephalopods. Here, we reinterpret the problematic Middle Cambrian animal Nectocaris pteryx as a primitive (that is, stem-group), non-mineralized cephalopod, based on new material from the Burgess Shale. Together with Nectocaris, the problematic Lower Cambrian taxa Petalilium and (probably) Vetustovermis form a distinctive clade, Nectocarididae, characterized by an open axial cavity with paired gills, wide lateral fins, a single pair of long, prehensile tentacles, a pair of non-faceted eyes on short stalks, and a large, flexible anterior funnel. This clade extends the cephalopods' fossil record by over 30 million years, and indicates that primitive cephalopods lacked a mineralized shell, were hyperbenthic, and were presumably carnivorous. The presence of a funnel suggests that jet propulsion evolved in cephalopods before the acquisition of a shell. The explosive diversification of mineralized cephalopods in the Ordovician may have an understated Cambrian 'fuse'.

  13. Evidence for microbial dissolution of pyrite from the Lower Cambrian oolitic limestone, South China

    Directory of Open Access Journals (Sweden)

    W. Liu

    2011-03-01

    Full Text Available The oxidative dissolution of the sulphide mineral pyrite (FeS2 has been of significant interest since it affects global geochemical cycles, generates acid mine drainage, and is used in industrial metal extraction. Several different groups of prokaryotes are known to catalyze the dissolution of pyrite and use the free energy generated from the oxidation, which may result in the dissolution of the mineral and the precipitation of the secondary ferric iron minerals either on the cell surface or is separated from the cells. However, straightforward evidence for such metabolic process in the ancient sediments is rare. Here we report pyrite crystals from the Lower Cambrian oolitic limestones that show indications of microbial erosion in various degrees. Erosion pits and tubular micro-tunnels with characteristic shapes and sizes in our samples are generally similar to those obtained from the laboratory studies on the oxidative dissolution of pyrite by iron-oxidizing bacteria. Diagenetic examination demonstrates that the bioerosion predates the consolidation of the limestone. In addition, bacillus-sized and -shaped microfossils encrusted with iron oxides are present in our samples, which are very likely to be fossilized sheaths produced by iron-oxidizing bacteria. Our findings indicate that the microbial oxidative dissolution of pyrite existed in the Cambrian shallow marine carbonate sediments. Furthermore, we suggest that characteristic pitting patterns on the pyrite crystals from ancient sediments are an important clue to trace the evolution of life, in particular, the evolution of metabolism like microbial iron oxidation in the remote past on our planet, independent of biomarkers, isotopic signals and body fossils as well.

  14. Carbonaceous preservation of Cambrian hexactinellid sponge spicules.

    Science.gov (United States)

    Harvey, Thomas H P

    2010-12-23

    Early fossil sponges offer a direct window onto the evolutionary emergence of animals, but insights are limited by the paucity of characters preserved in the conventional fossil record. Here, a new preservational mode for sponge spicules is reported from the lower Cambrian Forteau Formation (Newfoundland, Canada), prompting a re-examination of proposed homologies and sponge inter-relationships. The spicules occur as wholly carbonaceous films, and are interpreted as the remains of robust organic spicule sheaths. Comparable sheaths are restricted among living taxa to calcarean sponges, although the symmetries of the fossil spicules are characteristic of hexactinellid sponges. A similar extinct character combination has been documented in the Burgess Shale fossil Eiffelia. Interpreting the shared characters as homologous implies complex patterns of spicule evolution, but an alternative interpretation as convergent autapomorphies is more parsimonious. In light of the mutually exclusive distributions of these same characters among the crown groups, this result suggests that sponges exhibited an early episode of disparity expansion followed by comparatively constrained evolution, a pattern shared with many other metazoans but obscured by the conventional fossil record of sponges.

  15. Sm-Nd isotopic compositions of Cambrian-Ordovician strata at the Jinggangshan area in Jiangxi Province:Tectonic implications

    Institute of Scientific and Technical Information of China (English)

    SHEN WeiZhou; LING HongFei; SHU LiangShu; ZHANG FangRong; XIANG Lei

    2009-01-01

    Whole-rock Sm-Nd Isotopes were investigated for Cambrian-Ordovician strata from the Jinggangshan area beTween the Yangtze Block and Cathysla Block in South China. These strata were deposited as a greatly thick unit of muddy-sandy laminas with intercalated carbonate and organic carbon-bearing layers. They have low ε(t) values of -13.9 to -7.9 and old Nd model ages of 1842 to 2375 Ma. In t-tdiagram, they are far away from the concordant line but fall within the evolution zone of the Proterozoic crust of South China. This indicates that the Cambrian-Ordovician strata are mainly composed of mat-ters eroded from ancient Paleoproterozoic crust that may mainly consist of continental-derived detrital sediments with high maturity in the Cathyaia Block. However, the Ordovician Jueshangou Formation and Dui'erehi Formation have ε(t) values of -10.5 and -7.9 at the higher end of the above range and Nd model ages of 1842 to 2059 Ma at the lower end of the above range. This suggests involvement of more detritus that were eroded from the relatively juvenile crust from Late Paleoproterozoic to the Early Neoproterozoic. All the Nd model ages for the Cambrian-Ordovlcian sedimentary rocks in the Cathysia Block and the southeastern margin of the Yangtze Block are older than 1800 Ma, suggesting that no material from the Early Paleozoic depleted mantle-derived magmas was involved in these regions.

  16. Darwin's dilemma: the realities of the Cambrian 'explosion'.

    Science.gov (United States)

    Conway Morris, Simon

    2006-06-29

    The Cambrian 'explosion' is widely regarded as one of the fulcrum points in the history of life, yet its origins and causes remain deeply controversial. New data from the fossil record, especially of Burgess Shale-type Lagerstätten, indicate, however, that the assembly of bodyplans is not only largely a Cambrian phenomenon, but can already be documented in fair detail. This speaks against a much more ancient origin of the metazoans, and current work is doing much to reconcile the apparent discrepancies between the fossil record, including the Ediacaran assemblages of latest Neoproterozoic age and molecular 'clocks'. Hypotheses to explain the Cambrian 'explosion' continue to be generated, but the recurrent confusion of cause and effect suggests that the wrong sort of question is being asked. Here I propose that despite its step-like function this evolutionary event is the inevitable consequence of Earth and biospheric change.

  17. Dinomischus from the Middle Cambrian Kaili Biota, Guizhou, China

    Institute of Scientific and Technical Information of China (English)

    PENG Jin; ZHAO Yuanlong; LIN Jih-Pai

    2006-01-01

    Dinomischus is a rare solitary epifaunal suspension feeder. The over-all morphology of Dinomischus consists of a conical calyx surrounded with elongate bracts and an elongate stem. Visceral mass and stomach sac are evident in the body cavity. Dinomischus is interpreted as a primative ancestor of living entoprocts based on similarities in morphology and mode of life. Previously,Dinomischus is only known in two localities: the mid-Middle Cambrian Burgess Shale Biota and the Early Cambrian Chengjiang Biota. A single specimen of Dinomischus cf. D. isolatus Cowry Morris,1977 from the Kaili Biota, Guizhou, China is reported here. The discovery of Dinomischus in the Kaili Biota extends its geographical range and indicated that the rare Dinomischus could tolerate deeper water settings during the Middle Cambrian.

  18. Cambrian stalked echinoderms show unexpected plasticity of arm construction.

    Science.gov (United States)

    Zamora, S; Smith, A B

    2012-01-22

    Feeding arms carrying coelomic extensions of the theca are thought to be unique to crinoids among stemmed echinoderms. However, a new two-armed echinoderm from the earliest Middle Cambrian of Spain displays a highly unexpected morphology. X-ray microtomographic analysis of its arms shows they are polyplated in their proximal part with a dorsal series of uniserial elements enclosing a large coelomic lumen. Distally, the arm transforms into the more standard biserial structure of a blastozoan brachiole. Phylogenetic analysis demonstrates that this taxon lies basal to rhombiferans as sister-group to pleurocystitid and glyptocystitid blastozoans, drawing those clades deep into the Cambrian. We demonstrate that Cambrian echinoderms show surprising variability in the way their appendages are constructed, and that the appendages of at least some blastozoans arose as direct outgrowths of the body in much the same way as the arms of crinoids.

  19. Ediacarian sponge spicule clusters from southwestern Mongolia and the origins of the Cambrian fauna

    Science.gov (United States)

    Brasier, Martin; Green, Owen; Shields, Graham

    1997-04-01

    Carbon and strontium isotopic data are used to show that the earliest sponge spicule clusters and associated phosphatic sediments (with Anabarites) from southwestern Mongolia are of Ediacarian age. Spicule morphologies include bundles of oxeas arranged in three-dimensional quadrules, linked together at junctions by tetracts, pentacts, hexacts, or polyactines. All are referred to the Phylum Porifera, Class Hexactinellida. These sponge spicules provide the oldest remains that can be assigned without question to an extant phylum, and also the first firm evidence for filter feeding and metazoan silica biomineralization in the fossil record. It is suggested that siliceous and phosphatic members of the “Cambrian fauna” may have had their origins in eutrophic and outer shelf facies of the Late Proterozoic.

  20. Contribution of Oxygenic Photosynthesis to Palaeo-Oceanic Organic Carbon Sink Fluxes in Early Cambrian Upper Yangtze Shallow Sea:Evidence from Black Shale Record

    Institute of Scientific and Technical Information of China (English)

    Kunyu Wu; Tingshan Zhang; Yang Yang; Yuchuan Sun; Daoxian Yuan

    2016-01-01

    ABSTRACT:The extensive transgression that occurred on the Yangtze Plate in Early Cambrian led to a massive organic carbon pool in the Niutitang Formation. A black shale core section from 3 251.08 to 3 436.08 m beneath the Earth’s surface was studied to estimate the contribution of oxygenic photosyn-thesis to organic carbon sink fluxes in Early Cambrian Upper Yangtze shallow sea. Results indicate that the oxygenic photosynthesis played the most important role in carbon fixation in Early Cambrian. Or-ganic carbon sink was mainly contributed by photosynthetic microorganisms, e.g., cyanobacteria, algae and archaea. The Niutitang Formation was formed in a deep anoxic marine shelf sedimentary envi-ronment at a sedimentation rate of ~0.09±0.03 mm/yr. The initial TOC abundance in Niutitang shale ranged from 0.18%to 7.09%, with an average of 2.15%. In accordance with the sedimentation rate and initial TOC abundance, organic carbon sink fluxes were calculated and found to range from 0.21 to 8.10×103 kg/km2·yr-1, especially the organic carbon sink fluxes in depth between 3 385 and 3 470 m range from 3.80 to 8.10×103 kg/km2·yr-1, with an average of~6.03×103 kg/km2·yr-1, which is much high-er than that of contemporary marine sediments. The organic carbon sink fluxes of Niutitang shale are equal to 0.56 to 21.61×103 kg/km2·yr-1 net oxygen emitted into the Early Cambrian ocean and atmos-phere, this emitted oxygen may have significantly promoted the oxygen level of the Earth’s surface and diversification of metazoans.

  1. A New Landmark for Exploration of the Cambrian Explosion

    Institute of Scientific and Technical Information of China (English)

    Zhao Baohua; Song Jianlan; Guo Haiyan

    2002-01-01

    @@ New studies suggest that the Kaili Biota in southwestern China's Guizhou Province could be the third revealing evidence for the spectacular Cambrian Explosion of life about 530 million years ago, next to the Burgess Shale Biota of Canada, found in 1909,and the Chengjiang Biota, brought to light in Yunnan Province, China,in 1984.

  2. New Evidence for Pre-Cambrian Development of Complex Animals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Much mystery surrounds the sudden and mushrooming appearance of animals in the fossil record about 540 million years ago. Known as the "Cambrian explosion," the change took place from zero evidence to all the basic types of creatures in today's world within a few million years.

  3. Compilation and network analyses of cambrian food webs.

    Directory of Open Access Journals (Sweden)

    Jennifer A Dunne

    2008-04-01

    Full Text Available A rich body of empirically grounded theory has developed about food webs--the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments appear insurmountable for most fossil assemblages; however, a few assemblages with excellent soft-body preservation across trophic levels are candidates for food-web data compilation and topological analysis. Here we present plausible, detailed food webs for the Chengjiang and Burgess Shale assemblages from the Cambrian Period. Analyses of degree distributions and other structural network properties, including sensitivity analyses of the effects of uncertainty associated with Cambrian diet designations, suggest that these early Paleozoic communities share remarkably similar topology with modern food webs. Observed regularities reflect a systematic dependence of structure on the numbers of taxa and links in a web. Most aspects of Cambrian food-web structure are well-characterized by a simple "niche model," which was developed for modern food webs and takes into account this scale dependence. However, a few aspects of topology differ between the ancient and recent webs: longer path lengths between species and more species in feeding loops in the earlier Chengjiang web, and higher variability in the number of links per species for both Cambrian webs. Our results are relatively insensitive to the exclusion of low-certainty or random links. The many similarities between Cambrian and recent food webs point toward surprisingly strong and enduring constraints on the organization of complex feeding interactions among metazoan species. The few differences could reflect a transition to more strongly integrated and constrained trophic organization within ecosystems following the rapid

  4. Compilation and network analyses of cambrian food webs.

    Science.gov (United States)

    Dunne, Jennifer A; Williams, Richard J; Martinez, Neo D; Wood, Rachel A; Erwin, Douglas H

    2008-04-29

    A rich body of empirically grounded theory has developed about food webs--the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments appear insurmountable for most fossil assemblages; however, a few assemblages with excellent soft-body preservation across trophic levels are candidates for food-web data compilation and topological analysis. Here we present plausible, detailed food webs for the Chengjiang and Burgess Shale assemblages from the Cambrian Period. Analyses of degree distributions and other structural network properties, including sensitivity analyses of the effects of uncertainty associated with Cambrian diet designations, suggest that these early Paleozoic communities share remarkably similar topology with modern food webs. Observed regularities reflect a systematic dependence of structure on the numbers of taxa and links in a web. Most aspects of Cambrian food-web structure are well-characterized by a simple "niche model," which was developed for modern food webs and takes into account this scale dependence. However, a few aspects of topology differ between the ancient and recent webs: longer path lengths between species and more species in feeding loops in the earlier Chengjiang web, and higher variability in the number of links per species for both Cambrian webs. Our results are relatively insensitive to the exclusion of low-certainty or random links. The many similarities between Cambrian and recent food webs point toward surprisingly strong and enduring constraints on the organization of complex feeding interactions among metazoan species. The few differences could reflect a transition to more strongly integrated and constrained trophic organization within ecosystems following the rapid diversification of species, body

  5. Tropical shoreline ice in the late Cambrian: Implications for earth's climate between the Cambrian Explosion and the Great Ordovician Biodiversification Event

    Science.gov (United States)

    Runkel, Anthony C.; MacKey, T.J.; Cowan, Clinton A.; Fox, David L.

    2010-01-01

    Middle to late Cambrian time (ca. 513 to 488 Ma) is characterized by an unstable plateau in biodiversity, when depauperate shelf faunas suffered repeated extinctions. This poorly understood interval separates the Cambrian Explosion from the Great Ordovician Biodiversification Event and is generally regarded as a time of sustained greenhouse conditions. We present evidence that suggests a drastically different climate during this enigmatic interval: Features indicative of meteoric ice are well preserved in late Cambrian equatorial beach deposits that correspond to one of the shelf extinction events. Thus, the middle to late Cambrian Earth was at least episodically cold and might best be considered a muted analogue to the environmental extremes that characterized the Proterozoic, even though cooling in the two periods may have occurred in response to different triggers. Such later Cambrian conditions may have significantly impacted evolution preceding the Ordovician radiation.

  6. New Vetulicoliids from the Lower Cambrian Guanshan Fauna,Kunming

    Institute of Scientific and Technical Information of China (English)

    LUO Huilin; FU Xiaoping; HU Shixue; LI Yong; CHEN Liangzhong; YOU Ting; LIU Qi

    2005-01-01

    The Guanshan Fauna, a soft-bodied fauna intermediate between the Chengjiang Fauna and the Kaili Fauna and also the Burgess Shale Fauna stratigraphically, consists of trilobites, trilobitoides, Tuzoia, Vetulicola, Paleoscolex, brachiopods and sponges. The discovery and research of this fauna is of great significance in understading the "Cambrian Explosion" and the evolution of early life. The occurrence of vetulicoliids from the Guanshan Fauna not only adds new members to the taxonomic list, but also provides new information to the evolution of this animal group. This paper describe Vetulicola gantoucunensis Luo, Fu et Hu sp. nov. from the Lower Cambrian Wulongqing Formation in the Kunming area. Also presented are the amended description of Vetulicola and the comparisons with related genera within Vetulicoliids. The affinity, distribution, as well as evolution of vetulicoliids are discussed.

  7. New burgess shale fossil sites reveal middle cambrian faunal complex.

    Science.gov (United States)

    Collins, D; Briggs, D; Morris, S C

    1983-10-14

    Soft-bodied and lightly sclerotized Burgess shale fossils have been found at more than a dozen new localities in an area extending for 20 kilometers along the front of the Cathedral Escarpment in the Middle Cambrian Stephen Formation of the Canadian Rockies. Five different fossil assemblages from four stratigraphic levels have been recognized. These assemblages represent distinct penecontemporaneous marine communities that together make up a normal fore-reef faunal complex.

  8. A primitive fish from the Cambrian of North America.

    Science.gov (United States)

    Morris, Simon Conway; Caron, Jean-Bernard

    2014-08-28

    Knowledge of the early evolution of fish largely depends on soft-bodied material from the Lower (Series 2) Cambrian period of South China. Owing to the rarity of some of these forms and a general lack of comparative material from other deposits, interpretations of various features remain controversial, as do their wider relationships amongst post-Cambrian early un-skeletonized jawless vertebrates. Here we redescribe Metaspriggina on the basis of new material from the Burgess Shale and exceptionally preserved material collected near Marble Canyon, British Columbia, and three other Cambrian Burgess Shale-type deposits from Laurentia. This primitive fish displays unambiguous vertebrate features: a notochord, a pair of prominent camera-type eyes, paired nasal sacs, possible cranium and arcualia, W-shaped myomeres, and a post-anal tail. A striking feature is the branchial area with an array of bipartite bars. Apart from the anterior-most bar, which appears to be slightly thicker, each is associated with externally located gills, possibly housed in pouches. Phylogenetic analysis places Metaspriggina as a basal vertebrate, apparently close to the Chengjiang taxa Haikouichthys and Myllokunmingia, demonstrating also that this primitive group of fish was cosmopolitan during Lower-Middle Cambrian times (Series 2-3). However, the arrangement of the branchial region in Metaspriggina has wider implications for reconstructing the morphology of the primitive vertebrate. Each bipartite bar is identified as being respectively equivalent to an epibranchial and ceratobranchial. This configuration suggests that a bipartite arrangement is primitive and reinforces the view that the branchial basket of lampreys is probably derived. Other features of Metaspriggina, including the external position of the gills and possible absence of a gill opposite the more robust anterior-most bar, are characteristic of gnathostomes and so may be primitive within vertebrates.

  9. Upper Cambrian chitons (Mollusca, polyplacophora) from Missouri, USA

    Science.gov (United States)

    Pojeta, J.; Vendrasco, M.J.; Darrough, G.

    2010-01-01

    Numerous new specimens reveal a greater presence of chitons in Upper Cambrian rocks than previously suspected. Evidence is presented showing that the chiton esthete sensory system is present in all chiton species in this study at the very beginning of the known polyplacophoran fossil record. The stratigraphic occurrences and paleobiogeography of Late Cambrian chitons are documented. The 14 previously-named families of Cambrian and Ordovician chitons are reviewed and analyzed. Aulochitonidae n. fam. is defined, based on Aulochiton n. gen.; A. sannerae n. sp. is also defined. The long misunderstood family Preacanthochitonidae and its type genus Preacanthochiton Bergenhayn, 1960, are placed in synonymy with Mattheviidae and Chelodes Davidson & King, 1874, respectively; Eochelodes Marek, 1962, also is placed in synonymy with Chelodes, and Elongata Stinchcomb & Darrough, 1995, is placed in synonymy with Hemithecella Ulrich & Bridge, 1941. At the species level, H. elongata Stinchcomb & Darrough, 1995, and Elongata perplexa Stinchcomb & Darrough, 1995, are placed in synonymy with H. eminensis Stinchcomb & Darrough, 1995. The Ordovician species H. abrupta Stinchcomb & Darrough, 1995, is transferred to the genus Chelodes as C. abrupta (Stinchcomb & Darrough, 1995). The Ordovician species Preacanthochiton baueri Hoare & Pojeta, 2006, is transferred to the genus Helminthochiton as H. ? baueri (Hoare & Pojeta, 2006). The Ordovician species H. marginatus Hoare & Pojeta, 2006, is transferred to the genus Litochiton as L. marginatus (Hoare & Pojeta, 2006). Matthevia walcotti Runnegar, Pojeta, Taylor, & Collins, 1979, is treated as a synonym of Hemithecella expansa Ulrich & Bridge, 1941. In addition, other multivalved Cambrian mollusks are discussed; within this group, Dycheiidae n. fam. is defined, as well as Paradycheia dorisae n. gen. and n. sp. Cladistic analysis indicates a close relationship among the genera here assigned to the Mattheviidae, and between Echinochiton Pojeta

  10. Early Cambrian pentamerous cubozoan embryos from South China.

    Directory of Open Access Journals (Sweden)

    Jian Han

    Full Text Available BACKGROUND: Extant cubozoans are voracious predators characterized by their square shape, four evenly spaced outstretched tentacles and well-developed eyes. A few cubozoan fossils are known from the Middle Cambrian Marjum Formation of Utah and the well-known Carboniferous Mazon Creek Formation of Illinois. Undisputed cubozoan fossils were previously unknown from the early Cambrian; by that time probably all representatives of the living marine phyla, especially those of basal animals, should have evolved. METHODS: Microscopic fossils were recovered from a phosphatic limestone in the Lower Cambrian Kuanchuanpu Formation of South China using traditional acetic-acid maceration. Seven of the pre-hatched pentamerous cubozoan embryos, each of which bears five pairs of subumbrellar tentacle buds, were analyzed in detail through computed microtomography (Micro-CT and scanning electron microscopy (SEM without coating. RESULTS: The figured microscopic fossils are unequivocal pre-hatching embryos based on their spherical fertilization envelope and the enclosed soft-tissue that has preserved key anatomical features arranged in perfect pentaradial symmetry, allowing detailed comparison with modern cnidarians, especially medusozoans. A combination of features, such as the claustrum, gonad-lamella, suspensorium and velarium suspended by the frenula, occur exclusively in the gastrovascular system of extant cubozoans, indicating a cubozoan affinity for these fossils. Additionally, the interior anatomy of these embryonic cubozoan fossils unprecedentedly exhibits the development of many new septum-derived lamellae and well-partitioned gastric pockets unknown in living cubozoans, implying that ancestral cubozoans had already evolved highly specialized structures displaying unexpected complexity at the dawn of the Cambrian. The well-developed endodermic lamellae and gastric pockets developed in the late embryonic stages of these cubozoan fossils are comparable with

  11. Oxygen, Ecology, and the Cambrian Radiation of Animals

    OpenAIRE

    2013-01-01

    The Proterozoic-Cambrian transition records the appearance of essentially all animal body plans (phyla), yet to date no single hypothesis adequately explains both the timing of the event and the evident increase in diversity and disparity. Ecological triggers focused on escalatory predator–prey “arms races” can explain the evolutionary pattern but not its timing, whereas environmental triggers, particularly ocean/atmosphere oxygenation, do the reverse. Using modern oxygen minimum zones as an ...

  12. Armored kinorhynch-like scalidophoran animals from the early Cambrian.

    Science.gov (United States)

    Zhang, Huaqiao; Xiao, Shuhai; Liu, Yunhuan; Yuan, Xunlai; Wan, Bin; Muscente, A D; Shao, Tiequan; Gong, Hao; Cao, Guohua

    2015-11-26

    Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated cuticular plates, longitudinal muscles, dorsoventral muscles, and ganglia. Molecular clock estimates suggest that kinorhynchs may have diverged in the Ediacaran Period. Remarkably, no kinorhynch fossils have been discovered, in sharp contrast to priapulids and loriciferans that are represented by numerous Cambrian fossils. Here we describe several early Cambrian (~535 million years old) kinorhynch-like fossils, including the new species Eokinorhynchus rarus and two unnamed but related forms. E. rarus has characteristic scalidophoran features, including an introvert with pentaradially arranged hollow scalids. Its trunk bears at least 20 annuli each consisting of numerous small rectangular plates, and is armored with five pairs of large and bilaterally placed sclerites. Its trunk annuli are reminiscent of the epidermis segments of kinorhynchs. A phylogenetic analysis resolves E. rarus as a stem-group kinorhynch. Thus, the fossil record confirms that all three scalidophoran phyla diverged no later than the Cambrian Period.

  13. At the origin of animals: the revolutionary cambrian fossil record.

    Science.gov (United States)

    Budd, Graham E

    2013-09-01

    The certain fossil record of animals begins around 540 million years ago, close to the base of the Cambrian Period. A series of extraordinary discoveries starting over 100 years ago with Walcott's discovery of the Burgess Shale has accelerated in the last thirty years or so with the description of exceptionally-preserved Cambrian fossils from around the world. Such deposits of "Burgess Shale Type" have been recently complemented by other types of exceptional preservation. Together with a remarkable growth in knowledge about the environments that these early animals lived in, these discoveries have long exerted a fascination and strong influence on views on the origins of animals, and indeed, the nature of evolution itself. Attention is now shifting to the period of time just before animals become common, at the base of the Cambrian and in the preceding Ediacaran Period. Remarkable though the Burgess Shale deposits have been, a substantial gap still exists in our knowledge of the earliest animals. Nevertheless, the fossils from this most remarkable period of evolutionary history continue to exert a strong influence on many aspects of animal evolution, not least recent theories about developmental evolution.

  14. Minerals in the gut: scoping a Cambrian digestive system

    Science.gov (United States)

    Strang, K. M.; Armstrong, H. A.; Harper, D. A. T.

    2016-11-01

    The Sirius Passet Lagerstätte of North Greenland contains the first exceptionally preserved mat-ground community of the Cambrian, dominated, in terms of abundance, by trilobites but particularly characterized by iconic arthropods and lobopods, some also occurring in the Burgess shale. High-resolution photography, scanning electron imaging and elemental mapping have been carried out on a variety of specimens of the non-mineralized arthropod Campanamuta mantonae (Budd 2011 J. Syst. Palaeontol. 9, 217-260 (doi:10.1080/14772019.2010.492644)) which has three-dimensional gut and muscle preservation. Results show that the guts contain a high concentration of calcium phosphate (approximating to the mineral francolite), whereas the adjacent muscles are silicified. This indicates a unique, tissue-specific taphonomy for this Cambrian taxon. We hypothesize that the precipitation of calcium phosphate in the guts occurs rapidly after death by `crystal seed' processes in suboxic, slightly acidic conditions; critically, the gut wall remained intact during precipitation. We postulate that the calcium phosphate was derived from ingested cellular material. Silicification of the muscles followed as the localized water chemistry became saturated in silica, high in Fe2+, and low in oxygen and sulfate. We document here the unique occurrence of two distinct but mechanistically similar taphonomic pathways within a diverse suite of possibilities in an Early Cambrian Lagerstätte.

  15. Antarctica, supercontinents and the palaeogeography of the Cambrian 'explosion'

    Science.gov (United States)

    Dalziel, Ian

    2014-05-01

    Laurentia is bordered by latest Precambrian-Cambrian rifted margins and must therefore have been located within a Precambrian supercontinent. Geochronologic and geochemical evidence indicates that it was attached to parts of the East Antarctic craton within the Rodinian supercontinent in the late Mesoproterozoic. The Mawson craton of Antarctica rifted from the proto-Pacific margin of Laurentia during the Neooproterozoic, colliding with the present 'southern cone' of Laurentia at ~600 Ma along the Shackleton Range suture zone as Gondwana and Laurentia amalgamated to form the ephemeral Pannotia supercontinental assembly at the end of the Precambrian. The abrupt appearance of almost all animal phyla in the fossil record is often colloquially referred to as the Cambrian 'explosion' of life on Earth. It is also named 'Darwin's dilemma,' as he appreciated that this seemingly mysterious event posed a major problem for his theory of evolution by natural selection. It coincided with a time of major marine transgression over all the continents. Although the metazoan 'explosion' is now seen as more protracted than formerly recognized, it is still regarded one of the most critical events in the history of the biosphere. One of the most striking aspects of the earliest Cambrian fossils is geographic differentiation. In particular, the first benthic trilobite faunas on Laurentia, ancestral North America, and the newly amalgamated southern supercontinent of Gondwana are distinctly different. This has led to the suggestion of an unknown vicariant event intervening between an ancestral trilobite clade and higher members that are represented in the fossil record, possibly one related to the breakup of a supercontinent. Igneous rocks along the Panthalassic margin of Gondwana, including South America, southernmost Africa and the Ellsworth-Whitmore crustal block of Antarctica, and along the proto-Appalachian margin of Laurentia indicate that final separation of Laurentia from

  16. Isotopic evolution of the terminal Neoproterozoic and early Cambrian carbon cycle on the northern Yangtze Platform, South China

    Institute of Scientific and Technical Information of China (English)

    GUO Qingjun; LIU Congqiang; Harald STRAUSS; Tatiana GOLDBERG

    2003-01-01

    Profound geotectonic, climatic and biological changes occur during the terminal Neoproterozoic and its transition into the early Cambrian. These are reflected in temporal variations of the chemical and isotopic composition of seawater. We are studying a sequence of sedimentary rocks at the Shatan section, northern Yangtze Platform, Sichuan Province of China. This succession comprises, in ascending stratigraphic order, predominantly calcareous sediments of the Sinian upper Dengying Formation and black shales of the lower Cambrian Guojiaba Formation (time equivalent of Niutitang Fm.). Paleoenvironmental setting represents shallow-water shelf deposits. The objective of our study is to provide temporal records for the isotopic compositions of organic and carbonate carbon throughout this time interval. Organic carbon isotope values display a range between -35.8‰ and -30.1‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between -3.5‰ and +0.5‰. These secular variations are interpreted to reflect perturbations of the global carbon cycle, specifically changes in the fractional burial of organic carbon. However, local conditions have further affected the isotopic signals.

  17. Silicalites of Hydrothermal Origin in the Lower Cambrian Black Rock Series of South China

    Institute of Scientific and Technical Information of China (English)

    李胜荣; 高振敏

    1996-01-01

    A silicalite bed was found in the hanging wall and foot wall of the sulfide-rich bed of the Lower Cambrian black rock series in South China.Its origin was not described before,On the oxide(SiO2-Al2O3,SiO2-MgO,SiO2-k2o+Na2O)diagrams for discriminating silicalites of chemical,biological and volcanic origins(Liu Xiufeng,1991),most of the data points of silicalites fall within the areas representing silicalites of chemical and volcanic origins.On the Al-Fe-Mn diagram for discriminating silicalites of hydrothermal and biological origins(Yamamoto,1987),the data points fall within the areas representing silicalites of hydrotermal and hydrothermal-biological origins.On the SiO2-Al2O3 diagram for discriminating silicalites of hydrothermal and hydrogenous origins(Bonatti,1975),the data points mostly fall within the hydrothermal area.The ratios of SiO2/Al2O3,SiO2/(K2O+Na2O),SiO2/MgO,and K2O/Na2O in the silicalites stand between those of volcanic sediments and of seafloor hydrothermal sediments.The total amount of rare-earth elements in the silicalites is low;the North american Shale-normalized REE patterns decline leftward with obvious negative Ce anomaly.The trace elements Mo,Zn,As,Sb,Se,U,and Ba are higher than those in non-hydrothermal sediments and U/Th≥1.The present authors think that the silicalites are derived from seafloor hot brines which had attracted elements from igneous rocks.

  18. Beyond the Burgess Shale: Cambrian microfossils track the rise and fall of hallucigeniid lobopodians.

    Science.gov (United States)

    Caron, Jean-Bernard; Smith, Martin R; Harvey, Thomas H P

    2013-09-22

    Burgess Shale-type deposits are renowned for their exquisite preservation of soft-bodied organisms, representing a range of animal body plans that evolved during the Cambrian 'explosion'. However, the rarity of these fossil deposits makes it difficult to reconstruct the broader-scale distributions of their constituent organisms. By contrast, microscopic skeletal elements represent an extensive chronicle of early animal evolution--but are difficult to interpret in the absence of corresponding whole-body fossils. Here, we provide new observations on the dorsal spines of the Cambrian lobopodian (panarthropod) worm Hallucigenia sparsa from the Burgess Shale (Cambrian Series 3, Stage 5). These exhibit a distinctive scaly microstructure and layered (cone-in-cone) construction that together identify a hitherto enigmatic suite of carbonaceous and phosphatic Cambrian microfossils--including material attributed to Mongolitubulus, Rushtonites and Rhombocorniculum--as spines of Hallucigenia-type lobopodians. Hallucigeniids are thus revealed as an important and widespread component of disparate Cambrian communities from late in the Terreneuvian (Cambrian Stage 2) through the 'middle' Cambrian (Series 3); their apparent decline in the latest Cambrian may be partly taphonomic. The cone-in-cone construction of hallucigeniid sclerites is shared with the sclerotized cuticular structures (jaws and claws) in modern onychophorans. More generally, our results emphasize the reciprocal importance and complementary roles of Burgess Shale-type fossils and isolated microfossils in documenting early animal evolution.

  19. Community structure and composition of the Cambrian Chengjiang biota

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on previously published species data(228 species in over 18 phyla) and field sampling(114 species and 18406 individuals) in the Chengjiang-Haikou-Anning area,we analyzed quantitatively the paleocommunity composition and structure of the Cambrian Chengjiang biota(Cambrian Series 2,eastern Yunnan,China).Arthropods dominate the community both in species diversity(species:37%) and in abundance(individuals:51.8%).Priapulids(individuals:22.6%) and brachiopods(individuals:16.3%) follow in abundance rank.The arthropod Kunmingella douvillei(26.2%),the priapulid Cricocosmia jinning-ensis(15.4%),and the brachiopod Diandongia pista(11%) are the three most abundant species.Ecological analyses show that the community was dominated by epifaunal organisms(species:63%,individuals:68.4%) followed by infaunal organisms(species:11.9%,individuals:25.9%),nektobenthic organisms(species:11.5%,individuals:2.6%),and pelagic organisms(species:5.3%,individuals:3.1%).The diverse feeding strategies,dominated by suspension feeders(species:35.6%,individuals:26.1%) and hunter/scavengers(species:31.1%,individuals:40.4%),indicate the former existence of a complex food chain and intense competition.Epifaunal vagrant omnivores(28.2%),infaunal vagrant hunter/scavengers(19.8%),epifaunal sessile suspension feeders(17.7%),and epifaunal vagrant hunter/scavengers(15.3%) were the most abundant ecological groups,represented primarily by arthropods,poriferans,priapulids,and brachiopods.Ecological group analyses reveal that the early Cambrian Chengjiang biota is similar in community patterns and functional relations to modern biotas in shallow marine settings.

  20. Source tracing of noble metal elements in Lower Cambrian black rock series of Guizhou-Hunan Provinces, China

    Institute of Scientific and Technical Information of China (English)

    李胜荣; 高振敏

    2000-01-01

    The Lower Cambrian black rock series of South China is abnormally rich in noble metal elements. According to the concentrations, the ratios, the relations, the distribution and partition patterns of noble metal elements, the authors think that the noble metals and other elements are neither directly from extraterrestrial materials, nor from the products of normal marine sedimentation. The abnormal enrichment of noble metal elements is closely related with hydrothermal fluid that flew out on the sea floor through deep cycling and reaction with Proterozoic ultramafic-mafic igneous rocks forming noble metal rich fluid. It is possible to form industrial multiple-element-ore-deposits, especially hydrothermal type platinum-group-element-ore-deposits in the region with strong hydrothermal action.

  1. Source tracing of noble metal elements in Lower Cambrian black rock series of Guizhou-Hunan Provinces, China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Lower Cambrian black rock series of South China is abnormally rich in noble metal elements. According to the concentrations, the ratios, the relations, the distribution and partition patterns of noble metal elements, the authors think that the noble metals and other elements are neither directly from extraterrestrial materials, nor from the products of normal marine sedimentation. The abnormal enrichment of noble metal elements is closely related with hydrothermal fluid that flew out on the sea floor through deep cycling and reaction with Proterozoic ultramafic-mafic igneous rocks forming noble metal rich fluid. It is possible to form industrial multiple-element- ore-deposits, especially hydrothermal type platinum-group-element-ore-deposits in the region with strong hydrothermal action.

  2. A New Ichnogenus Kailidiscus Produced by Attachment from the Middle Cambrian Kaili Formation in Taijiang, Guizhou Province, China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Over 190 specimens of an attachment ichnofossil Kailidiscus (n. ichnogen.) have been found in the Kaili Bitoa, a Burgess Shale-type biota, from the middle Kaili Formation (early Middle Cambrian) in Taijiang County, Guizhou Province, southern China. Kailidiscus is an epichnia with a circular to oval attachment platform, on which there is a carbonaceous film probably formed by the body of the living organism. Structures such as a marginal furrow, an inner and outer marginal ride, many convex fold-ridges, and a large caved peripheral furrow on the attachment platform may be the result of basal tissues of a sessile organism that wrinkled to increase the attachment's surface area. The Kailidiscus organism may have been a sessile cnidarian attached to the muddy seafloor. Kailidiscus organisms lived in relatively quiet water,and were buried by a sudden influx of sediment.

  3. The Cambrian explosion triggered by critical turning point in genome size evolution.

    Science.gov (United States)

    Li, Dirson Jian; Zhang, Shengli

    2010-02-05

    The Cambrian explosion is a grand challenge to science today and involves multidisciplinary study. This event is generally believed as a result of genetic innovations, environmental factors and ecological interactions, even though there are many conflicts on nature and timing of metazoan origins. The crux of the matter is that an entire roadmap of the evolution is missing to discern the biological complexity transition and to evaluate the critical role of the Cambrian explosion in the overall evolutionary context. Here, we calculate the time of the Cambrian explosion by a "C-value clock"; our result quite fits the fossil records. We clarify that the intrinsic reason of genome evolution determined the Cambrian explosion. A general formula for evaluating genome size of different species has been found, by which the genome size evolution can be illustrated. The Cambrian explosion, as a major transition of biological complexity, essentially corresponds to a critical turning point in genome size evolution.

  4. Morphology and ultrastructure of epilithic versus cryptic, microbial growth in lower Cambrian phosphorites from the Montagne Noire, France.

    Science.gov (United States)

    Alvaro, J J; Clausen, S

    2010-03-01

    The lower Cambrian grainy phosphorites of the northern Montagne Noire occur interbedded with grey to black, laminated to massive shales and limestones deposited along the edge of a continental shelf, associated with slope-related facies and unstable substrates. The concentration of phosphate took place by repeated alternations of low sedimentation rates and condensation (hardgrounds), in situ early-diagenetic precipitation of fluorapatite, winnowing and polyphase reworking of previously phosphatized skeletons and hardground-derived clasts. The succession of repeated cycles of sedimentation, phosphate concentration, and reworking led to multi-event phosphate deposits rich in allochthonous particles. Phosphogenesis was primarily mediated by microbial activity, which is evidenced by the abundance of phosphatized putative microbial remains. These occur as smooth and segmented filaments, sheaths, and ovoid-shaped coccoids. These simple morphologies commonly form composite frameworks as a result of their aggregation and entanglement, leading to the record of biofilms, microbial mats, and complex networks. These infested the calcitic skeletonized microfossils that littered the substrate. Microbial activity evidences epilithic (anisotropic coatings on skeletons), euendolithic (perforating skeletal walls), and cryptoendolithic (lining inter- and intraparticulate pores) strategies, the latter dominated by bundles of filaments and globular clusters that grew along the cavities of helcionellids and hyoliths. According to their epilithic versus cryptic strategies, microbial populations that penetrated and dwelled inside hard skeletal substrates show different network and colonial morphologies. These early Cambrian shell concentrations were the loci of a stepwise colonization made by saprophytic to mutualistic, cyanobacterial-fungal consortia. Their euendolithic and cryptoendolithic ecological niches provided microbial refugia to manage the grazing impact mainly led by metazoans.

  5. Element—Assemblage Zoning Features of Gold Deposis in the Cambrian Silicalite Formation,Western Qinling

    Institute of Scientific and Technical Information of China (English)

    刘家军; 郑明华; 等

    1997-01-01

    The gold deposits,occurring in the south subzone of western Qinling,are the only typical and important strata-bound gold deposits,which are associated with submarine exhalative sedimentation.The gold deposits include the La'erma ore deposit,the Qiongmo ore deposit and the Yaxiang ore occurrence.They are hosted i the Cambrian silicalite formation composed of black chert and slate.The presence of typical chert offers important evidence to evaluate the possible submarine exhalative system and its role in the formation of the gold deposits,which are closely associated with peroclation and diffusion in the horizontal,vertical and axial directions,Element-assemblage zonation is clearly seen due to differences in element concentrations in different directions,Such a zonation makes gold.selenium,uranium,copper,stibium,molybdenum,mercury,etc,precipitate in the form of simple or composite orebodies.The establishent of the element-assemblage zonation is highly helpful for evaluating directly the metallogenesis of gold deposits.

  6. Mo Isotopes Record Destabilization of a Stratified Ocean at the Precambrian-Cambrian Boundary

    Science.gov (United States)

    Wille, M.; Nägler, T. F.; Schröder, S.; Lehmann, B.; Kramers, J. D.

    2007-12-01

    Here we present Mo isotope signatures in black shales from two sample sets (Ara group, Oman and Yangtze Platform, China) which were deposited at and shortly after the Precambrian-Cambrian boundary (PC-C). At the first view, the overall Mo isotopic signatures (delta98/95Mo) of the Early Cambrian black shales is 1.2 permil below recent ocean water, similar to the signature found in Mesoproterozoic shales (Arnold et al. 2004), indicating a larger proportion of Mo sedimentation under strongly euxinic conditions compared to recent oceans. A chemically stratified ocean with sulfidic deep waters and modestly oxygenated surface waters as proposed by Canfield (1998) for the Paleoproterozoic and Mesoproterozoic ocean, and Jiang et al. (2007) reported Carbon isotope data from the Ediacaran Yangtze platform (635-542 Ma) to be consistent with long-term deep ocean anoxia/euxinia. A stratified ocean therefore provides a plausible scenario to explain our new PC-C Mo isotope data. On closer inspection, a transient Mo isotopic signal following immediately after the PC-C boundary in both sample sets indicates a short but intense global non-steady state situation. In particular, a short term, drastic decrease of the Mo ocean inventory to almost zero is required to reconcile the observed Mo isotope data. Combined with the extreme Mo enrichment, found in the Chinese sulfide marker bed at the PC-C boundary, this signal has to be explained with a non-uniformitarian Mo scavenging mechanism. We put forward the hypothesis of mixing of oxidized, i.e. Mo rich surface waters with upwelling euxinic bottom water masses of the stratified ocean, as H2S is the most efficient Mo scavenging reagent. This scenario not only explains the transient isotopic signal, it can also be responsible for the sudden extinction of the Ediacaran fauna by H2S poisoning. In contrast, mass extinction scenarios like bolide impact, flood basalt eruptions or methane release, do not provide a direct explanation for the

  7. He-Ar Isotopic Systematics of Fluid Inclusions in Pyrites from PGE-polymetallic Deposits in Lower Cambrian Black Rock Series, South China

    Institute of Scientific and Technical Information of China (English)

    SUN Xiaoming; WANG Min; XUE Ting; MA Mingyang; LI Yinhe

    2004-01-01

    He-Ar isotopic compositions of fluid inclusions trapped in pyrites from some representative PGEpolymetallic deposits in Lower Cambrian black rock series in South China were analyzed by using an inert gas isotopic mass spectrometer. The results show that the ore-forming fluids possess a low 3He/4He ratio, varying from 0.43x10-8 to 26.39×10-8, with corresponding R/Ra value of 0.003-0.189. The 40Ar/36Ar ratios are 258-287, close to those of airsaturated water (ASW). He-Ar isotopic indicator studies show that the ore-forming fluids were mainly derived from the formation water or basinal hot brine and sea water, while the content of mantle-derived fluid or deep-derived magmatic water might be negligible. The PGE-polymetallic mineralization might be related to the evolution of the Caledonian miogeosynclines distributed along the southern margin of the Yangtze Craton. During the Early Cambrian, the formation water or basinal hot brine trapped in Caledonian basins which accumulated giant thick sediments was expelled and migrated laterally along strata because of the pressure generated by overlying sediments. The basinal hot brine ascended along faults, mixed with sea water and finally deposited ore minerals.

  8. Occurrence of Highly Mature Organic Matter in Marine Black Shale Petroleum Source Rocks of Basal Cambrian from Northern Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    YU Bingsong (于炳松); Hailiang DONG; CHEN Jianqiang (陈建强); CHEN Xiaolin (陈晓林); LIANG Shiyou (梁世友)

    2004-01-01

    More and more evidence indicates that organic matter (OM) in immature organic-rich sediments and sedimentary rocks is chemically adsorbed onto the outer surfaces of minerals and into interlayer (inner) surfaces of smectitic clay minerals in the form of amorphous molecular-scale carbon. But there have been few reports about the occurrence of highly mature OM in marine black shales (petroleum source rocks). The occurrence of highly mature OM in the black shales of basal Cambrian from northern Tarim Basin is studied in this paper. Based on the comprehensive analyses of total organic carbon contents (TOC), maximum thermolysis temperatures (T max ) of OM, mineral surface areas (MSA), and scanning electronic microscopic (SEM) and transmission electronic microscopic (TEM) observations of the black shales, it is concluded that the highly mature OM in the marine black shales of the basal Cambrian from northern Tarim Basin occurs in particulates ranging in size from 1 to 5 μm in diameter. Through the contrast of the occurrence of the highly mature OM in the black shales with that of the immature ones in modern marine continental margin sediments, some scientific problems are proposed, which are worth to study further in detail.

  9. Discussion on the systematic position of the Early Cambrian priapulomorph worms

    Institute of Scientific and Technical Information of China (English)

    HUANG Diying; CHEN Junyuan; J. VANNIER

    2006-01-01

    @@ Priapulid worms form a small marine phylum in present-day environments with only 18 described species, but they were the most abundant animals in the endobenthic communities of the Cambrian. They are particularly well represented in the Lower Cambrian Maotianshan Shale of China [1-3] and the Middle Cambrian Burgess Shale of Canada [4]. The priapulid worms from the 530 Ma old Maotianshan Shale 5 be placed within 6 basic groups: selkirkiid, corynetid, anningid, palaeoscolecidan, tylotitid and priapuliid [5]. In addition, another important endobenthic worm phylum, the Sipuncula has been also reported from the Maotianshan Shale [6].

  10. Fossil Association from the Lower Cambrian Yanjiahe Formation in the Yangtze Gorges Area, Hubei, South China

    Institute of Scientific and Technical Information of China (English)

    GUO Junfeng; Tsuyoshi KOMIYA; LI Yong; HAN Jian; ZHANG Xingliang; ZHANG Zhifei; OU Qiang; LIU Jianni; SHU Degan; Shigenori MARUYAMA

    2008-01-01

    Apart from previously reported Small Shelly Fossils (SSFs), a macroscopic fossil assemblage, comprising abundant algae, cone-shaped tubular fossil forms, and probable impressions of a megascopic metazoan, comes from the Lower Cambrian Yanjiahe Formation in the Yangtze Gorges area of western Hubei Province, south China. The visible fossils are preserved in thin-laminated siltstone or muddy siltstone intercalated between 8-15 mm-thick carbonate deposits, probably representing sedimentary settings of a constrained local depression in the shallow water carbonate platform during the Early Cambrian Meishucunian Stage. The macroscopic fossil association provides significant fossil evidence about the evolution of life from the late Precambrian to the 'Cambrian explosion' interval.

  11. Plated Cambrian bilaterians reveal the earliest stages of echinoderm evolution.

    Directory of Open Access Journals (Sweden)

    Samuel Zamora

    Full Text Available Echinoderms are unique in being pentaradiate, having diverged from the ancestral bilaterian body plan more radically than any other animal phylum. This transformation arises during ontogeny, as echinoderm larvae are initially bilateral, then pass through an asymmetric phase, before giving rise to the pentaradiate adult. Many fossil echinoderms are radial and a few are asymmetric, but until now none have been described that show the original bilaterian stage in echinoderm evolution. Here we report new fossils from the early middle Cambrian of southern Europe that are the first echinoderms with a fully bilaterian body plan as adults. Morphologically they are intermediate between two of the most basal classes, the Ctenocystoidea and Cincta. This provides a root for all echinoderms and confirms that the earliest members were deposit feeders not suspension feeders.

  12. Diagenesis of Cambrian and lower Carboniferous sandstones, southwest Sinai, Egypt

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Wahab, A.A.; Salem, A.M.K. [Tanta Univ., Kafr El-Sheikh (Egypt); McBride, E.F. [Univ. of Texas, Austin, TX (United States)

    1996-12-31

    Quartzose and feldspathic Cambrian and Lower Carboniferous sandstones (fluvial > marine > eolian) deposited on the Arabian shield in southwestern Sinai were not buried more than 1 to 1.5 km until Late Cretaceous and younger time, when the deepest rocks reached 2.5 km. Porosity was reduced by compaction to about 26%. Grain rearrangement was the main mechanism of compaction; intergranular pressure solution and ductile grain deformation are insignificant. Cementation by iron oxide (5%), quartz (3%), calcite (2%), kaolinite (2%) and K-feldspar (< 1%) reduced porosity to 12-15% except in silcretes and some ferricretes, where porosity was reduced to non-reservoir quality. Cements have no selectivity for certain textures or stratigraphic positions.

  13. Diagenesis of Cambrian and lower Carboniferous sandstones, southwest Sinai, Egypt

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Wahab, A.A.; Salem, A.M.K. (Tanta Univ., Kafr El-Sheikh (Egypt)); McBride, E.F. (Univ. of Texas, Austin, TX (United States))

    1996-01-01

    Quartzose and feldspathic Cambrian and Lower Carboniferous sandstones (fluvial > marine > eolian) deposited on the Arabian shield in southwestern Sinai were not buried more than 1 to 1.5 km until Late Cretaceous and younger time, when the deepest rocks reached 2.5 km. Porosity was reduced by compaction to about 26%. Grain rearrangement was the main mechanism of compaction; intergranular pressure solution and ductile grain deformation are insignificant. Cementation by iron oxide (5%), quartz (3%), calcite (2%), kaolinite (2%) and K-feldspar (< 1%) reduced porosity to 12-15% except in silcretes and some ferricretes, where porosity was reduced to non-reservoir quality. Cements have no selectivity for certain textures or stratigraphic positions.

  14. Primitive deuterostomes from the Chengjiang Lagerstätte (Lower Cambrian, China).

    Science.gov (United States)

    Shu, D G; Morris, S C; Han, J; Chen, L; Zhang, X L; Zhang, Z F; Liu, H Q; Li, Y; Liu, J N

    2001-11-22

    Cambrian fossil-Lagerstätten (sites of exceptional fossil preservation), such as those from Chengjiang (Lower Cambrian) and the Burgess Shale (Middle Cambrian), provide our best window into the Cambrian 'explosion'. Such faunas are known from about 40 localities, and have yielded a widely disparate series of taxa ranging from ctenophores to agnathan fish. Recent excavations of the Chengjiang fossil-Lagerstätte, known from a series of sites near Kunming in Yunnan, south China, have resulted in the discovery of several new forms. In conjunction with material described earlier, these provide evidence for a new group of metazoans, the vetulicolians. Several features, notably a series of gill slits, suggest that this group can throw light on an early stage of deuterostome diversification.

  15. Rare earth element geochemistry of Cambrian phosphorites from the Yangtze Region

    Institute of Scientific and Technical Information of China (English)

    CHEN Jiyan; YANG Ruidong; WEI Huairui; GAO Junbo

    2013-01-01

    Analysis on P2O5 and REE (rare earth elements) in basal Cambrian phosphorites from the Yangtze Region,showed that the phosphofites from Bailongtan in Yunnan Province,Zhijin,Jinsha,Xishui,Zunyi,Tianzhu and Tongren in Guizhou Province,Shangrao in Jiangxi Province,Jiangshan in Zhejiang Province and Nanjing in Jiangsu Province contained high REE contents in phosphorites,especially those from Tianzhu and Tongren in Guizhou Province,Shangrao in Jiangxi Province,Jiangshan in Zhejiang Province and Nanjing in Jiangsu Province.Among them,the highest REE contents reached up to 1361.59× 10-6 and P2O5 contents up to 29.45%.In contrast,phosphofites from Kaiyang,Qingzhen and Zhenyuan in Guizhou Province had relatively low total REE contents and low P2O5 contents,with the lowest total REE content of 53.19× 10-6,and the lowest P2O5 content of 0.07%.REE contents exhibited a positive correlation with phosphorous contents,indicating a close genetic relationship between REE and phosphorous element.The main reason was the difference of the sedimentary environments and the contents of phosphorous and REE in deep water mass formed in upwelling currents,at an upper slope facies (Slu) in reducing condition due to relatively closed sedimentary environment.It was very difficult for the upswelling phosphorous and REE to deposit,massive phosphorous deposits were hard to be formed.At a deep water ramp facies (DRa) in the ascending process of currents,phosphorus and REE underwent differentiation rather than sedimentation.Consequently,the contents of P2O5 sediments and REE were low.At a shallow water ramp facies (including shoals and tidal fiats) (SRa),with active seawater circulation and phosphatic supplement,sunny weather,high nutrition and rapid growth of algae,were benefitial for the physical enrichment of carbonate sediments.Therefore,massive phosphorite deposits were easy to be formed with abundant REE minerals,and finally turned into high REE beating phosphorous deposits.

  16. Moulting in the lobopodian Onychodictyon from the lower Cambrian of Greenland

    DEFF Research Database (Denmark)

    Topper, Timothy P.; Skovsted, Christian B.; Peel, John S.;

    2013-01-01

    . We document here an assemblage of well-preserved isolated plates of Onychodictyon sp. from the Lower Cambrian (Cambrian Series 2, Stage 4) of North Greenland. Two specimens exhibit perfectly conjoined plates from successive moults. Details of ornamentation and the outline and profile of the fixed...... plates are identical, but width and length of the underlying plate are 24% larger. These specimens boost the body of evidence that lobopodians moulted but also show that plate outline and ornamentation did not vary during ontogeny....

  17. Hydrogen sulphide release to surface waters at the Precambrian/Cambrian boundary.

    Science.gov (United States)

    Wille, Martin; Nägler, Thomas F; Lehmann, Bernd; Schröder, Stefan; Kramers, Jan D

    2008-06-01

    Animal-like multicellular fossils appeared towards the end of the Precambrian, followed by a rapid increase in the abundance and diversity of fossils during the Early Cambrian period, an event also known as the 'Cambrian explosion'. Changes in the environmental conditions at the Precambrian/Cambrian transition (about 542 Myr ago) have been suggested as a possible explanation for this event, but are still a matter of debate. Here we report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 Myr. We find a transient molybdenum isotope signal immediately after the Precambrian/Cambrian transition. Using a box model of the oceanic molybdenum cycle, we find that intense upwelling of hydrogen sulphide-rich deep ocean water best explains the observed Early Cambrian molybdenum isotope signal. Our findings suggest that the Early Cambrian animal radiation may have been triggered by a major change in ocean circulation, terminating a long period during which the Proterozoic ocean was stratified, with sulphidic deep water.

  18. A Carboniferous non-onychophoran lobopodian reveals long-term survival of a Cambrian morphotype.

    Science.gov (United States)

    Haug, Joachim T; Mayer, Georg; Haug, Carolin; Briggs, Derek E G

    2012-09-25

    Lobopodians, a nonmonophyletic assemblage of worm-shaped soft-bodied animals most closely related to arthropods, show two major morphotypes: long-legged and short-legged forms. The morphotype with stubby, conical legs has a long evolutionary history, from the early Cambrian through the Carboniferous, including the living onychophorans and tardigrades. Species with tubular lobopods exceeding the body diameter have been reported exclusively from the Cambrian; the three-dimensionally preserved Orstenotubulus evamuellerae from the uppermost middle Cambrian "Orsten" (Sweden) is the youngest long-legged lobopodian reported thus far. Here we describe a new long-legged lobopodian, Carbotubulus waloszeki gen. et sp. nov., from Mazon Creek, Illinois, USA (∼296 million years ago). This first post-Cambrian long-legged lobopodian extends the range of this morphotype by about 200 million years. The three-dimensionally preserved specimen differs significantly from the associated short-legged form Ilyodes inopinata, of which we also present new head details. The discovery of a Carboniferous long-legged lobopodian provides a more striking example of the long-term survival of Cambrian morphotypes than, for example, the occurrence of a Burgess Shale-type biota in the Ordovician of Morocco and dampens the effect of any major extinction of taxa at the end of the middle Cambrian.

  19. The Cambrian Evolutionary Explosion: Novel Evidence from Fossils Studied by X-ray Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jun-Yuan [Nanjing University, China

    2011-06-01

    The Cambrian explosion (from 542 million years to 488 million years ago) is one of the greatest mysteries in evolutionary biology. It wasn't until this period that complex organisms became common and diverse. the magnitude of the event can be understood based on the contrast between the biota and the degree of diversity of the fossils from both sides. great advances have been made in Cambrian palaeontology over the past century, especially the discovery of the well-preserved soft-bodied fauna from the Middle Cambrian Burgess Shale and the Lower Cambrian Maotianshan Shale deposits. The Cambrian side of the "Cambrian explosion" is richly illustrated and contrasts greatly with the Precambrian side. The study of these extraordinarily preserved fossil biota is extremely difficult. A major challenge is 3-D reconstruction and determining the patter of the cell organization in Weng'an embryos and their buried structures in Maotianshan Shale fossils. This talk will show that two recent technological approaches, propagation phase contrast synchrotron x-ray microtomography and microtomography, provide unique analytical tools that permit the nondestructive computational examination and visualization of the internal and buried characters in virtual sections in any plane, and virtual 3-D depictions of internal structures.

  20. Paleomagnetic studies on the late Ediacaran - Early Cambrian Puncoviscana and the late Cambrian Campanario formations, NW Argentina: New paleogeographic constraints for the Pampia terrane

    Science.gov (United States)

    Franceschinis, Pablo R.; Rapalini, Augusto E.; Escayola, Monica P.; Luppo, Tomás

    2016-10-01

    A magnetofabric and paleomagnetic study was carried out in the Late Ediacaran - Early Cambrian Puncoviscana and the early Late Cambrian Campanario formations, exposed in Santa Victoria Oeste, in northwestern Argentina. Ten sites (93 samples) were located in tuffs and volcanic sills interbedded in the Puncoviscana Formation, one of which had been dated at 537 ± 0.9 Ma. On the other hand, 42 samples were collected at three sites from red to purple sandstones of the Campanario Formation. The analysis of anisotropy of magnetic susceptibility (AMS) allowed to recognize a pre-Andean fabric in both formations indicating that it is previous to the Andean cycle. In the paleomagnetic study reliable magnetic components were isolated in only two sites of the Puncoviscana formation whose virtual geomagnetic poles (VGPs) are close to but do not coincide with the apparent polar wander path of Río de la Plata craton - Gondwana for the late Neoproterozoic - Cambrian. A new paleomagnetic pole (18.2°S, 358.8°W, K: 27.9; A95: 3.9) was computed for the Campanario formation which is close to but does not coincide with those obtained in other locations for this unit and were considered anomalous respect to the expected position in the Gondwana path. The pole presented here is closer to the apparent polar wander path of Gondwana for the Late Cambrian-Early Ordovician suggesting two possible interpretations; the presence of different amounts of Andean tectonic rotations between different sampling locations of the Campanario Formation or the recording of a rapid Pampia dextral displacement along the Rio de la Plata craton margin in Cambrian times.

  1. Three-step modernization of the ocean:Modeling of carbon cycles and the revolution of ecological systems in the Ediacaran/Cambrian periods

    Institute of Scientific and Technical Information of China (English)

    Miyuki Tahata; Yusuke Sawaki; Yuichiro Ueno; Manabu Nishizawa; Naohiro Yoshida; Toshikazu Ebisuzaki; Tsuyoshi Komiya; ,Shigenori Maruyama

    2015-01-01

    Important ecological changes of the Earth (oxidization of the atmosphere and the ocean) increase in nutrient supply due to the break-up of the super continent (Rodinia) and the appearance of multi-cellular organisms (macroscopic algae and metazoan) took place in the Ediacaran period, priming the Cambrian explosion. The strong perturbations in carbon cycles in the ocean are recorded as excursions in carbonate and organic carbon isotope ratio (d13Ccarb and d13Corg) from the Ediacaran through early Cambrian periods. The Ediacaraneearly Cambrian sediment records of d13Ccarb and d13Corg, obtained from the drill-core samples in Three Gorges in South China, are compared with the results of numerical simulation of a sim-ple one-zone model of the carbon cycle of the ocean, which has two reservoirs (i.e., dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The fluxes from the reservoirs are assumed to be proportional to the mass of the carbon reservoirs. We constructed a model, referred to here as the Best Fit Model (BFM), which reproduce d13Ccarb and d13Corg records in the Ediacaraneearly Cambrian period noted above. BFM reveals that the Shuram excursion is related to three major changes in the carbon cycle or the global ecological system of the Earth:(1) an increase in the coefficient of remineralization by a factor of ca. 100, possibly corresponding to a change in the dominant metabolism from anaerobic respiration to aerobic respiration, (2) an increase of carbon fractionation index from 25&to 33&, possibly corresponding to the change in the primary producer from rock-living cyanobacteria to free-living macro algae, and (3) an in-crease in the coefficient of the organic carbon burial by a factor of ca. 100, possibly corresponding to the onset of a biological pump driven by the flourishing metazoan and zooplankton. The former two changes took place at the start of the Shuram excursion, while the third occurred at the end of the Shuram excursion. The other

  2. Genesis of early Cambrian phosphorite of Krol Belt, Lesser Himalaya

    Digital Repository Service at National Institute of Oceanography (India)

    Mazumdar, A.; Banerjee, D.M.

    models, we envisage a repeated influx of P and 12C rich water on to the shallow platform. Amorphous calcium phosphate (ACP) precipitated from the shallow water column overlying the sediment water interface and subsequently modified...

  3. Geochemical characteristics of organic matter-rich strata of lower Cambrian in Tarim Basin and its origin

    Institute of Scientific and Technical Information of China (English)

    CHEN; Jianfa; SUN; Shengli; LIU; Wenhui; ZHENG; Jianjing

    2004-01-01

    The organic matter-rich strata of the Yurtusi Formation of Lower Cambrian are wildly spread and steady in the Tarim Basin, in which cherts are developed, companied with phosphorite. Al/(Al+Fe+Mn) ratio and Si/(Si+Al+Fe) ratio of cherts range from 0.0023 to 0.0046 and 0.965 to 0.98, respectively, suggesting that cherts are formed in submarine hydrothermal activity and far away from terrestrial. Trace elements, such as As, Hg, Pb, Zn, Cu, Co, P, V, Ba, etc., are markedly rich in organic matter-rich sedimentary rocks of which Ba/Sr ratios are between 21.2 and 158.1. Compared with modern hydrothermal sediments, their Ba/Sr ratios are similar, it indicates that the organic matter-rich strata have the geochemical feature of submarine hydrothermal sediments. The total content of rare earth elements (ЕREE) in cherts is from 8.81 to 56.682 μg/g, on average 31.41 μg/g and the ΕREE of cherts is between continental margin chert's and abyssal chert's. The LREE/HREE ratio of cherts varies from 1.01 to 3.56, which reveals the characteristics of hydrothermal sediments. There is positive correlation between the total organic content (TOC) and Ba/Sr ratio which is geochemical index of submarine hydrothermal activity, which indicates that the submarine hydrothermal activity obviously influences the richness of organic matter in the Yurtusi Formation.

  4. A Cambrian Arc Built on the Neoproterozoic Rifted Margin of Gondwana

    Science.gov (United States)

    Musgrave, R. J.

    2009-12-01

    Cambrian convergence along the northeastern side of the Curnamona Craton, the Gondwana margin in southeastern Australia, resulted in the development of the Delamerian Orogen. A Neoproterozoic rifted margin, marked by the alkalic Mount Arrowsmith Volcanics, forms the substrate on which is built a NE-facing Cambrian arc, complete with a clearly delineated inner imbricate accretionary prism (the Wonnaminta Zone) and outer thin-skinned wedge (the Kayrunnera Zone). Arc volcanism, represented by the calc-alkaline Mount Wright Volcanics, exhibits mixed arc-rift geochemistry. Interpretation and modelling of magnetic data reveals a chain of volcanic edifices of the Mount Wright Arc, now below 3 to 7 km of Devonian sandstones in the Bancannia Trough. Remarkably, a simple rotation around an Euler pole reconstructs the Wonnaminta Zone against the craton, and aligns structural elements on the two sides of the trough. Arc volcanism evidently occupied a rift in marginal continental crust, and the geometry, geochemistry and geophysical properties of the Mount Wright Arc are closely analogous to the Taupo Zone of New Zealand. Rifting of the arc divided Delamerian structures, indicating that at least part of the Delamerian deformation developed in a subduction accretion setting, rather than in some terminal collision. Below the Wonnaminta Zone a 3 to 5 km thick body can be traced as a large magnetic source along the length of the zone. Overridden by the thrust stack of the accretionary prism, this body is mostly planar and dips towards the east, although it is deformed into a broad antiform in the central part of the zone. Physical properties suggest that this body may be a thick rift-volcanic pile equivalent to the Mount Arrowsmith Volcanics. In the southern part of the belt a re-entrant in the Wonnaminta Zone faces a large magnetic anomaly sourced in the basement of the Kayrunnera Zone. The geometry of the re-entrant, and the development of Silurian and Devonian basins over the

  5. Research on Diageneses of Cambrian Shoal Facies Carbonate Rocks in the Xiadong Area, Hubei Province

    Institute of Scientific and Technical Information of China (English)

    张秀莲; 蒋凌志

    2001-01-01

    With continuous outcrops, developed shoal facies rocks, complete types of diagenesis and changeable diagenetic environments, Cambrian strata are well developed in the Xiadong area, Yichang, Hubei Province. Under the combined influence of numerous diageneses, secondary pores can be formed, which result in better reservoir properties of the rock strata. The Cambrian rocks in this area consist of mainly carbonate rocks and secondarily detrital rocks. The carbonate rocks are dominated by grainstones including wormkalk, calcirudite-calcarenite, oolitic limestone and oncolitic limestone. Graded bedding and cross bedding are well developed in the strata, which indicates that the formation environment is of a high-energy shoal facies. In this area, there has developed a sequence of stable Cambrian platform carbonate deposition. The evolution trend is as follows: open sea shelf facies? intertidal low-energy restricted sea facies? intertidal high-energy shoal facies? coastal shoal facies? evaporite tidal-flat facies. The diageneses that the strata have experienced mainly include dolomitization, dedolomitization and dissolution, which are constructive diageneses for the formation of secondary pores, such as intercrystal pores, intercrystal solution pores, gypsum mold pores and caverns of dolomite. The diagenetic facies intervals can be divided into the unitary and the compound ones, totalling 22 in the area. In the early atmospheric fresh-water diagenetic environment and the late epidiagenetic environment, Cambrian rocks, especially dolomite of the Middle and Upper Cambrian, experienced extensive and profound fresh water corrosion, forming pore intervals with a porosity ranging from 5% to 15%.

  6. Composition and origin of Early Cambrian Tiantaishan phosphorite-Mn carbonate ores, Shaanxi Province, China

    Science.gov (United States)

    Hein, J.R.; Fan, D.; Ye, J.; Liu, T.; Yeh, H.-W.

    1999-01-01

    The Tiantaishan phosphorite-Mn carbonate ores occur in the Early Cambrian Tananpo Formation in complexly folded and faulted rocks located in southern Shaanxi Province. About 65 x 106 tonnes of 17% P2O5 ore reserves exist and Mn-ore reserves are about 8.3 x 106 tonnes of +18% Mn. The stratigraphic sequence in ascending order consists of black phyllite, black to gray phosphorite ore, black phyllite, rhodochrostone ore, Mn mixed-carbonates, and dolostone. Data are presented from microprobe mineral chemistry, whole-rock chemistry, stable isotopes of carbonates, X-ray mineralogy, petrographic and SEM observations, and statistical analysis of chemical data. The dominant ore-forming minerals are hydroxy- and carbonate fluorapatite and Ca rhodochrosite, with Mg kutnahorite and dolomite comprising the Mn mixed-carbonate section. Pyrite occurs in all rock types and alabandite (MnS) occurs throughout the rhodochrostone section. The mean P2O5 content of phosphorite is 31% and argillaceous phosphorite is 16%, while the mean MnO content of rhodochrostone ore is 37%. Phosphorite ores are massive, spheroidal, laminated, and banded, while rhodochrostone ores have oolitic, spheroidal, and granular fabrics. The most distinguishing characteristics of the ores are high total organic carbon (TOC) contents (mean 8.4%) in the phosphorite and high P2O5 contents (mean 2.7%) in the rhodochrostone ore. The atypically high TOC contents in the Tiantaishan phosphorite probably result from very strong productivity leading to high sedimentation rates accompanied by weak reworking of sediments; poor utilization of the organic matter by bacteria; and/or partial replacement of bacterial or algal mats by the apatite. The depositional setting of the ores was the margin of an epicontinental seaway created as a direct consequence of global processes that included break-up of a supercontinent, formation of narrow seaways, creation of extensive continental shelves, overturn of stagnant, metal-rich deep

  7. Articulated Wiwaxia from the Cambrian Stage 3 Xiaoshiba Lagerstätte

    Science.gov (United States)

    Yang, Jie; Smith, Martin R.; Lan, Tian; Hou, Jin-Bo; Zhang, Xi-Guang

    2014-04-01

    Wiwaxia is a bizarre metazoan that has been interpreted as a primitive mollusc and as a polychaete annelid worm. Extensive material from the Burgess Shale provides a detailed picture of its morphology and ontogeny, but the fossil record outside this lagerstätte is scarce, and complete wiwaxiids are particularly rare. Here we report small articulated specimens of Wiwaxia foliosa sp. nov. from the Xiaoshiba fauna (Cambrian Stage 3, Hongjingshao Formation, Kunming, south China). Although spines are absent, the fossils' sclerites - like those of W. corrugata - are symmetrically arranged in five distinct zones. They form rows across the body, and were individually added and shed throughout growth to retain an approximately symmetrical body shape. Their development pattern suggests a molluscan affinity. The basic body plan of wiwaxiids is fundamentally conserved across two continents through Cambrian Stages 3-5 - revealing morphological stasis in the wake of the Cambrian explosion.

  8. Sponge spicules in phosphorites of the Early Cambrian Gezhongwu Formation, Zhijin, Guizhou

    Institute of Scientific and Technical Information of China (English)

    YANG Ruidong; QIAN Yi; ZHANG Jie; ZHANG Weihua; JIANG Lijun; GAO Hui

    2004-01-01

    Phosphorites occurring at the bottom of the Cambrian system contain abundant small shelly fossils, which are the product of the first episode of life explosion in the Cambrian. It was previously reported that the small shelly fossils are dominated by hyolithids, olivooids, zhijinitids, conodontomorphs, yubelichitids, camenitids and algae, with minor amounts of sponge fossils. Large amounts of sponge spicules, diverse in form, have been found for the first time in the Gezhongwu Formation phosphorites at Shixing, Zhijin County, Guizhou Province, of which such spicules as diaxon-triactins, diaxon-tetractins, pentaxon-pentactins and hexon-hexactins account for 30%. These spicules constitute the sponge clastic phosphorites made up of sponge clastics. Meanwhile, it is also expected that the radiation and diversity of sponge animals started as early as in the earliest Early Cambrian. Habit and burying environment of sponge animal are discussed in the paper.

  9. Geological-lithological criteria for predicting oil content of the Cambrian in the Baltic Sea

    Energy Technology Data Exchange (ETDEWEB)

    Chepikov, K.R.; Nikishin

    1981-01-01

    An examination is made of the features of spread of sandy collectors of oil of different types in the middle Cambrain in the water area of the Baltic syneclise because of the modern and paleo-depth of their occurrence. A conclusion is drawn regarding the dependence of the postsedimentation quartz formation of Cambrian sandstones on the duration of their stay at considerable depths. A high evaluation is made of the possible oil content of the Liyepay-More elevation located in the zone of development of good pore collectors. It is suggested that the data of marine geophysics be used to pinpoint the concepts regarding the paleotectonics of productive deposits of the Cambrian and dispersal of different types of collectors on the Baltic water area, as well as rhythm-facial analysis for predicting oil traps of the nonanticlinal types in the Cambrian.

  10. Discovery of Corallina fossil from the Middle Cambrian of Taijiang County,Guizhou Province,China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Abundant and well-preserved macroalgae fossils have been discovered in silty mudstones and shales from the Middle Cambrian of Taijiang County,Guizhou Province,China.Corallina Paraamphiroa siniansis gen.et sp.nov.in the Kaili Fm.,is the earliest Corallina fossil,which usually coexists with other carbonaceous macroalgae fossils on the bedding planes of mudstone and shale and is different from the calcareous and phosphatized Precambrian-Cambrian thallus discovered in the Lower Cambrian of Siberia and the Doushantou phosphate rocks of Weng'an County,Guizhou Province,China.The discovery of calcified thallus in the Kaili Fm.bears great importance on the study of phylogeny and evolution of early calcareous macroalgae.

  11. Biodiversity and taphonomy of the Early Cambrian Guanshan biota,eastern Yunnan

    Institute of Scientific and Technical Information of China (English)

    Michael; STEINER

    2010-01-01

    The Guanshan biota from eastern Yunnan(Cambrian Series 2,early Stage 4) is a Burgess Shale-type fossil biota with abundant exceptionally preserved soft-bodied fossils after the discovery of the well-known Cambrian Chengjiang fauna and Kaili biota in South China.The geological settings,sedimentology,taphonomy,and the fossil assemblage of the Guanshan biota are briefly summarized here.The Guanshan biota consists of about 60 taxa belonging to more than 10 metazoan groups and algae,among which the lobopods,eldonids,hyolithids with helens,and green algae are reported for the first time.The common occurrence of soft-bodied preservation in many groups,notably the trilobites and brachiopods,makes the Guanshan biota a significant fossil lagersttte for understanding the metazoan evolution during Cambrian explosion and taphonomy of the Burgess Shale-type fossils.

  12. Cambrian Sequence Stratigraphy and Sea Level Cycles of North China Platform

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The Cambrian of the North China platform consists chiefly of shallow water deposits and shows the sedimentary characters of an epicontinental sea basin. Controlled mainly by global sea level changes and sedimentary influx, the depositional sequences all exhibit as composite sequences. From bottom upward, 14 sequences (3rd order) are recognized, which may be grouped into 5 sequence sets and further into 2 mesosequences (2nd order). It is suggested herein that the Cambrian/Ordovician boundary may better be set at the MFS (maximum flooding surface) of the sequence OSq1, above which the conodont Cordylodus lindstroemi occurs. This position is about 40 m above the traditional Cambrian/Ordovician boundary and is within the Yeli Formation.

  13. Ichnology of the Early Cambrian Tal Group, Mussoorie Syncline, Lesser Himalaya, India

    Indian Academy of Sciences (India)

    Meera Tiwari; S K Parcha; Rajita Shukla; Harshita Joshi

    2013-12-01

    The Lesser Himalayan sequence is considered as one of the best developed sections of Cambrian successions, exposed in five different synclines. Mussoorie Syncline, being one of the five synclines, exposes the Cambrian Tal Group. This paper describes nine ichnotaxa, viz., Dimorphichnus isp., ?Diplichnites isp., Monomorphichnus isp., Nereites isp., Palaeopasichnus isp., Palaeophycus isp., Planolites montanus, Planolites isp., Skolithos isp., Treptichnus isp. from the Dhaulagiri Formation of the Tal Group. A detailed analysis of the ichnofossils indicates that the entire succession of Tal Group reflects shallow marine conditions in general and Mussoorie Syncline in particular. The above ichnofossil assemblage along with earlier ichnofossils and other faunal occurrences substantiates the assignment of Early Cambrian age to the Dhaulagiri Formation.

  14. An epipodite-bearing crown-group crustacean from the Lower Cambrian.

    Science.gov (United States)

    Zhang, Xi-guang; Siveter, David J; Waloszek, Dieter; Maas, Andreas

    2007-10-04

    Crown-group crustaceans (Eucrustacea) are common in the fossil record of the past 500 million years back to the early Ordovician period, and very rare representatives are also known from the late Middle and Late Cambrian periods. Finds in Lower Cambrian rocks of the Phosphatocopina, the fossil sister group to eucrustaceans, imply that members of the eucrustacean stem lineage co-occurred, but it remained unclear whether crown-group members were also present at that time. 'Orsten'-type fossils are typically tiny embryos and cuticle-bearing animals, of which the cuticle is phosphatized and the material is three-dimensional and complete with soft parts. Such fossils are found predominantly in the Cambrian and Ordovician and provide detailed morphological and phylogenetic information on the early evolution of metazoans. Here we report an Orsten-type Konservat-Lagerstätte from the Lower Cambrian of China that contains at least three new arthropod species, of which we describe the most abundant form on the basis of exceptionally well preserved material of several growth stages. The limb morphology and other details of this new species are markedly similar to those of living cephalocarids, branchiopods and copepods and it is assigned to the Eucrustacea, thus representing the first undoubted crown-group crustacean from the early Cambrian. Its stratigraphical position provides substantial support to the proposition that the main cladogenic event that gave rise to the Arthropoda was before the Cambrian. Small leaf-shaped structures on the outer limb base of the new species provide evidence on the long-debated issue of the origin of epipodites: they occur in a set of three, derive from setae and are a ground-pattern feature of Eucrustacea.

  15. The onset of the 'Ordovician Plankton Revolution' in the late Cambrian

    DEFF Research Database (Denmark)

    Servais, Thomas; Perrier, Vincent; Danelian, Taniel

    2016-01-01

    The 'Great Ordovician Biodiversification Event' comprises the rapid diversification of marine organisms during the Ordovician Period. It is now clear that this adaptive radiation started for some organisms already in the Cambrian and continued for others beyond the end of the Ordovician, making...... during the late Cambrian and Early Ordovician, in particular in relation to the SPICE event. Our analyses include the changing diversities of the phytoplankton (acritarchs), diverse groups of zooplankton (e.g., radiolarians, graptolites, chitinozoans) and the switch to a planktonic mode of life of fossil...

  16. A New Platy-armored Worm from the Early Cambrian Chengjiang Lagerstatte, South China

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The Lower Cambrian Chengjiang Lagerstatte provides a good window to explore the origin and radiation of early bilaterians. Here we describe a netted sclerite-bearing worm Tabelliscolex hexagonus gen. et sp. nov., and tentatively assign it to palaeoscolecidans of priapulids. The cuticle of the animal is covered with two kinds of platy sclerites which are constructed by hexagonally arranged tubercles. Similar structures of the sclerites can be seen on some Cambrian palaeoscolecidans and lobopods, so, this new species is critical for understanding the relationships between lobopods and palaeoscolecidans.

  17. The first study of the micro-fauna of middle Cambrian olistoliths in the Argentine Precordillera

    OpenAIRE

    Fahlgren, Elise; Tranvik, Maria

    2015-01-01

    This study implies a survey of a somewhat unexplored Cambrian carbonate formation in the Argentine Precordillera (AP) located in western Argentina, close to the city of San José de Jáchal. The carbonate platform of the AP is a unique piece of the South American geology and is in this study partly surveyed and compared with the Stephen Formation of northern Canada, a middle Cambrian unit renowned for its contents of exceptionally well preserved soft bodied fossils named the Burgess Shale biota...

  18. Biological and Molecular Geochemical Evidence for Dinoflagellate Ancestors in the Upper Sinian-Cambrian

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Dinoflagellates are single celled organisms that reflect the ecological conditions in modem oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic (c.240 Ma ago). However, the presence of molecular biomarkers (dinosterane, 4α-methyl-24-ethylcholestane and triaromatic dinosteroids) in rock extracts and coccoid dinoflagellate fossils from the upper Sinian to Cambrian of the Tarim basin confirms the hypothesis that dinoflagellates have an ancient origin, and predate the oldest undisputed dinoflagellate fossils at least by 300 Ma, as early as the late Sinian-Cambrian.

  19. Affinities and functional morphology of the Middle Cambrian ornamented tubules from West Hunan, China

    Institute of Scientific and Technical Information of China (English)

    ZHU Caifa; DONG Xiping

    2004-01-01

    Problematic phosphatic tubular microfossils with ornamented sculptures are documented to exist in limestones of the upper Middle Cambrian Huaqiao Formation at the Paibi section and the Wangcun section in West Hunan, China. Two morphological patterns, including Ornamented Tube Form I and Ornamented Tube Form II are described. Based on the analysis of the preservation, wall structure and composition of the fossils, it is deduced that these ornamented tubes may represent carapace spines of some Cambrian arthropods with phosphatic carapaces, such as bradoriid crustaceans. Analysis of functional morphology indicates that the sclerites may rather be considered of a defensive than grasping function on the original organism body.

  20. Discovery of sponge body fossils from the late Meishucunian (Cambrian) at Jinsha, Guizhou, south China

    Institute of Scientific and Technical Information of China (English)

    YANG Xinglian; ZHAO Yuanlong; WANG Yue; WANG Pingli

    2005-01-01

    Here we report discovery of a sponge body fossil Triticispongia sp. from the base of lower Cambrian Niutitang Formation at Jinsha, Guizhou. Stratigraphically, the fossil horizon is located below Ni-Mo ore layer with the Niutitang Biota above, and is equivalent to the late Meishucunian. The species is global in shape with skeletons composed of stauractins and monaxons. Triticispongia sp. reported here may be the earliest sponge body fossils of Cambrian, which provides new informationfor understanding early evolution and radiation of sponge animals.

  1. Telling time in shallow water carbonates - from the Cambrian of Morocco to the Holocene of the Bahamas

    Science.gov (United States)

    Maloof, A. C.; Bowring, S. A.; Fike, D. A.; Grotzinger, J. P.

    2008-12-01

    Virtually all pre-Mesozoic records of changing ocean-atmosphere chemistry and temperature are derived from chemical sediments deposited on continental shelves. Paired isotope studies of these carbonate rocks have placed the evolution of life in the context of a variable and, at times, non-uniformitarian carbon-sulfur cycle. Furthermore, paired δ13C and 87Sr/86Sr have allowed for global correlation of these stratigraphic successions and have built a framework for studying the history of global change. However, in the absence of quantitative constraints on the rate and duration of geochemical variability, paired stable isotope data tell us little about the processes most important to the variable carbon-sulfur cycle and the co-evolution of life and the surface environment. We discuss two methods of telling time in shelfal carbonate successions. First, we illustrate the use of interbedded volcanic ashes in determining the rate of isotopic change during the Cambrian radiation of animals in Morocco. Next, we present a study of Holocene stratigraphy in the Bahamas that sheds light on the characteristic timescales for the dominant processes controlling carbonate production on continental shelves, and discuss the promise and risk of determining an absolute timescale in the absence of geochronology.

  2. Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) ‘The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia’

    Science.gov (United States)

    Briggs, Derek E. G.

    2015-01-01

    Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a ‘weird wonder’ (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750235

  3. Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) 'The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia'.

    Science.gov (United States)

    Briggs, Derek E G

    2015-04-19

    Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a 'weird wonder' (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

  4. Sedimentary facies of the upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: new insight on the old stormy debate

    Science.gov (United States)

    Eoff, Jennifer D.

    2014-01-01

    New data from detailed measured sections permit a comprehensive revision of the sedimentary facies of the Furongian (upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. Heterogeneous sandstones, comprising seven lithofacies along a depositional transect from shoreface to transitional-offshore environments, record sedimentation in a storm-dominated, shallow-marine epicontinental sea. The origin of glauconite in the Birkmose Member and Reno Member of the Lone Rock Formation was unclear, but its formation and preserved distribution are linked to inferred depositional energy rather than just net sedimentation rate. Flat-pebble conglomerate, abundant in lower Paleozoic strata, was associated with the formation of a condensed section during cratonic flooding. Hummocky cross-stratification was a valuable tool used to infer depositional settings and relative paleobathymetry, and the model describing formation of this bedform is expanded to address flow types dominant during its genesis, in particular the importance of an early unidirectional component of combined flow. The depositional model developed here for the Lone Rock Formation and Mazomanie Formation is broadly applicable to other strata common to the early Paleozoic that document sedimentation along flooded cratonic interiors or shallow shelves.

  5. Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils

    DEFF Research Database (Denmark)

    Agic, Heda; Moczydlowska, Malgorzata; Canfield, Donald Eugene

    2016-01-01

    Unicellular organic-walled microfossils from the Cambrian-Ordovician transition in Estonia (ca. 490-480million years ago) exhibit rare characters reflecting their function as reproductive algal cysts. The studied assemblages record the evolutionary history of phytoplankton in the early Palaeozoic...

  6. Ferroan dolomite cement in Cambrian sandstones: burial history and hydrocarbon generation of the Baltic sedimentary basin

    DEFF Research Database (Denmark)

    Sliaupa, S.; Cyziene, J.; Molenaar, Nicolaas

    2008-01-01

    The conditions and timing of carbonate cementation in Cambrian sandstones of the Baltic sedimentary basin were determined by oxygen and carbon stable isotope and chemical data in combination with optical and cathodoluminescence petrographic studies. Studied samples represent a range in present...

  7. Ultra-high geomagnetic field reversal frequency around the Precambrian-Cambrian transition ?

    Science.gov (United States)

    Pavlov, V.; Gallet, Y.; Shatsillo, A.; Kouznetsov, N.

    2014-12-01

    Magnetostratigraphic investigations carried out in Siberia have shown that the middle Cambrian was marked by an extremely high geomagnetic field reversal frequency of about 7 to 10 rev./Myr. The results available for the Lower Cambrian are more uncertain but they may indicate an even higher reversal frequency, which could thus reveal a very unstable nature of the geomagnetic field at this time. Recent magnetostratigraphic results also suggest that the geomagnetic reversal frequency has been extraordinarily high at the end of the Precambrian, thus in agreement with the Lower Cambrian data. We will present a review of these data, and will further describe new results we have obtained from Late Ediacaran-Nemakit-Daldynian sections of the south-western Siberian platform (Enisey range, Teya and Chapa rivers valleys). All these data provide consistent evidences for an ultra-high geomagnetic field reversal frequency, and thus for the exceptional nature of the geomagnetic field, around the Precambrian-Cambrian transition. We will also discuss a number of hypotheses which could explain a temporary destabilization of the geomagnetic field.

  8. Geochemistry of the Cambrian Sirius Passet Lagerstätte, Northern Greenland

    DEFF Research Database (Denmark)

    Le Boudec, Ange; Ineson, Jon; Rosing, Minik Thorleif;

    2014-01-01

    The lower Cambrian Sirius Passet Lagerstätte (∼518 Ma) consists of mudstones about 8 m thick located in the Franklinian Basin of North Greenland. We analyzed major and trace elements plus the S, C, Cu, Fe, Zn, and Mo isotope compositions. Factor analysis allowed the lithology of the mudstone...

  9. Kaili Biota: A Taphonomic Window on Diversification of Metazoans from the Basal Middle Cambrian: Guizhou, China

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yuanlong; ZHU Maoyan; Loren E. BABCOCK; YUAN Jinliang; Ronald L. PARSLEY; PENG Jin; YANG Xinglian; WANG Yue

    2005-01-01

    A Burgess Shale-type biota is, in part, characterized by a wide diversity of taxa and soft-part preservation.Each provides unique historical insights into early metazoan evolution. Among the more than 40 globally distributed biotas, the early Cambrian Chengjiang and Middle Cambrian Burgess-type biotas are the largest. The Kaili Biota, from the earliest Middle Cambrian of Guizhou, China, contains representatives of 110 metazoan genera belonging to 10 phyla. It contains many well-persevered soft-bodied specimens. This Chinese biota has become the third most taxonomically diverse Burgess Shale-type fauna. Because the Kaili Biota formed in an outer-shelf environment, its main faunal character is large numbers of eocrinoids and planktoic trilobites. The Kaili is younger than the Chengjiang Biota but older than the Canadian Burgess Shale Biota; it shares 30 genera with the Chengjiang and 38 genera with the Burgess Biota. The Kaili Biota displays a tapbonomic window to the diversification and evolution of marine offshore organisms covering 5.13million years between the Early and Middle Cambrian.

  10. Progress and significance in research on the early Middle Cambrian Kaili Biota, Guizhou Province,China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Important progress in research on the Kaili Biota has been made recently. Many interesting components from Chengjiang Biota and Burgess Shale Biota have been discovered, e.g. Microdictyon of lobopodia; Ottoia, Palaeoscolex of worms; Naraoia, Marrella of Trilobitioidea, Mollisonia, anamalocarids and other non-trilobite arthropods; and new sorts of echinoder-mas, macroalage fossils and so on. Recent work on the Kaili Biota has resulted in the following developments: (i) an increase in the number of animal genera, up to more than 100 genera in total, so that the Kaili Biota has become the third most diverse of the Burgess Shale-type Biota after the Burgess Shale and Chengjiang Biotas; and (ii) the most noteworthy fossils in the Kaili Biota are echinoderms, non-trilobite arthropods and soft-bodied medusiform fossils, especially the most diverse echinoderms. The progress provides envidence for the biodiversity of marine organisms presented after the "Cambrian Explosion" and serves as a link between the earlist Cambrian Chengjiang Biota and late early Middle Cambrian Burgess Shale Biota. It is of great significance in the reconstruction of the Cambrian palaeoplate, palaeongeography and in research on taphonomy.

  11. On the evolution and histology of some Cambrian protoconodonts, paraconodonts and primitive euconodonts

    Institute of Scientific and Technical Information of China (English)

    DONG Xiping

    2004-01-01

    Previous reports on the morphological evolution of protoconodonts and paraconodonts are reviewed. The evolutionary trends exhibited by species of the protoconodont genus Gapparodus and the paraconodont genus Westergaadodina are discussed. Based on the present study on histology, genus Paibiconus is protoconodont, while genus Yongshunella is paraconodont (fig. 1 (a)). However, the nature of Huayuanodontus has not been fully understood so far.Recently, the transitional form New Gen. Sensu Miller, 1980 of late Late Cambrian has been found in Hunan Province, South China. It is considered as the Sister-Group of Proconodontus.Moreover, another kind of transitional form of middle Late Cambrian and late Late Cambrian between Prooneotodus rotundatus and Proconodontus, which looks like Prooneotodus rotundatus in gross morphology, but has anterior and posterior costae, has also been found in Hunan,South China. This kind of transitional form is believed to be probably the real intermediate link between Prooneotodus rotundatus and Proconodontus, and Prooneotodus rotundatus is most probably the ancestor of Proconodontus. The two transitional forms noted above are all euconodonts by the study of their histology. Unlike the euconodonts of Post-Cambrian, the evolutionary relationships among the species of protoconodonts, paraconodonts and the primitive euconodonts could not be made clear without the histological study on them.

  12. Petrographic and geochemical composition of kerogen in the Furongian (U. Cambrian) Alum Shale, central Sweden

    DEFF Research Database (Denmark)

    Sanei, H.; Petersen, H. I.; Schovsbo, N. H.;

    2014-01-01

    This paper presents an integrated geochemical and petrological study of the Hällekis-1 core from the Furongian (upper Cambrian) Alum shales in central Sweden to characterise organic matter composition, depositional environment, and potential hydrocarbon generation capability. The results show tha...

  13. The distribution of the oil derived from Cambrian source rocks in Lunnan area, the Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    There are great differences in biomarks between Cambrian oil and Middle-Upper Ordoviclan oil. In this stuty, the authors analyzed 40 oils found in Lunnan area by GC-MS and calculated the content of Cambrian oil in the 40 oils according to the steroid indexes of typical oil mixture and match experiment. The results show that it is a general phenomenon in Ordovician reservoir that the oil derived from Cambrian source rock mixed with the oil derived from Middle-Upper Ordovician source rock in Lunnan area, the mixture degree of the two oils is lower in Carboniferous reservoir than in Ordovician reservoir, and the oils kept in Triassic reservoir have single source, Middle-Upper Ordovician source rock. The mixture oils mainly composed of Cambrian oil (>50%) distributed in Sangtamu fault zone, and the oils found in Lunnan fault zone are Middle-Upper Ordovician oil. This distribution of oils in Lunnan area is owing to that Lunnan fault zone is located in anticline axis part, Lunnan fault zone underwent serious erosion, and the oils from Cambrian source rock accumulated in Lunnan fault zone were degraded completely during Caledonian-Hercynian movement. But the Cambrian oil accumulated in Sangtamu fault zone was not degraded completely and some of them were left for the location of Sangtamu fault zone is lower than Lunnan fault zone. Later, the oil derived from Middle-Upper Ordovician source rock mixed with the remained Cambrian oil, and the mixture oil formed in Sangtamu fault zone.

  14. Marine Mo biogeochemistry in the context of dynamically euxinic mid-depth waters: A case study of the lower Cambrian Niutitang shales, South China

    Science.gov (United States)

    Cheng, Meng; Li, Chao; Zhou, Lian; Algeo, Thomas J.; Zhang, Feifei; Romaniello, Stephen; Jin, Cheng-Sheng; Lei, Li-Dan; Feng, Lian-Jun; Jiang, Shao-Yong

    2016-06-01

    Molybdenum (Mo) concentrations and Mo isotopes have been widely used as proxies for local and global redox conditions in early oceans (>520 Ma) that were stratified and characterized by dynamically euxinic mid-depth waters. However, the nature of the Mo cycle and accompanying isotopic fractionations in such oceans remain poorly known. To fill this gap, we conducted an integrated study of Mo isotopes and redox-sensitive trace element (RSTE) abundances in the Lower Cambrian Niutitang Formation at Yangjiaping, South China. This section accumulated on the northern shelf margin of the Nanhua Basin, a failed intracontinental rift basin with a good connection to the open ocean during the early Cambrian. The Niutitang Formation contains a ∼18-m-thick lower black shale member, and a ∼56-m-thick upper gray silty shale member. The lower member (LM) is moderately to strongly enriched in Mo, U and V, and heterogeneous in Mo isotopic composition (δ98Mo = -0.65‰ to +2.14‰), indicative of dominantly euxinic depositional conditions punctuated by ferruginous episodes (as shown by previously reported Fe speciation data). The upper member (UM) shows lesser enrichment of Mo, U and V, higher Mo/U ratios, and intermediate and more uniform Mo-isotopic compositions (δ98Mo = +1.16‰ to +1.71‰), indicative of weakly oxic to anoxic-euxinic depositional conditions. Geochemical profiles suggest that the LM-to-UM transition reflects a shift of the O2/H2S chemocline from the water column to the sediment. Large δ98Mo fluctuations in the LM may record variations of H2S concentrations in the mid-depth euxinic waters. The intermediate and relatively uniform δ98Mo values of the UM are attributed to the effects of a local Fe-Mn particulate shuttle. In light of the observations at Yangjiaping and other contemporaneous sections in the Nanhua Basin, we propose a new marine Mo biogeochemical model for the early Cambrian ocean. In this model, an Fe-Mn reduction zone may have developed above

  15. The Cambrian-Ordovician rocks of Sonora, Mexico, and southern Arizona, southwestern margin of North America (Laurentia): chapter 35

    Science.gov (United States)

    Page, William R.; Harris, Alta C.; Repetski, John E.; Derby, James R.; Fritz, R.D.; Longacre, S.A.; Morgan, W.A.; Sternbach, C.A.

    2013-01-01

    Cambrian and Ordovician shelf, platform, and basin rocks are present in Sonora, Mexico, and southern Arizona and were deposited on the southwestern continental margin of North America (Laurentia). Cambrian and Ordovician rocks in Sonora, Mexico, are mostly exposed in scattered outcrops in the northern half of the state. Their discontinuous nature results from extensive Quaternary and Tertiary surficial cover, from Tertiary and Mesozoic granitic batholiths in western Sonora, and from widespread Tertiary volcanic deposits in the Sierra Madre Occidental in eastern Sonora. Cambrian and Ordovician shelf rocks were deposited as part of the the southern miogeocline on the southwestern continental margin of North America.

  16. Silicified egg clusters from a Middle Cambrian Burgess Shale type deposit, Guizhou, south China

    Science.gov (United States)

    Lin, Jih-Pai; Scott, Andrew C.; Li, Chia-Wei; Wu, Hung-Jen; Ausich, William I.; Zhao, Yuan-Long; Hwu, Yeu-Kuang

    2006-12-01

    Although knowledge of Cambrian fossil eggs and/or embryos has increased dramatically, embryos were previously unknown in siliciclastic settings of coeval strata. Here we report for the first time egg clusters in a fine-grained siliciclastic matrix from the Middle Cambrian Kaili Formation lagerstätte (513 501 Ma), south China. Some were imaged under synchrotron radiation. These spheroids are preferentially preserved as microcrystalline quartz and interpreted as marine invertebrate fossil eggs based on patterns of spheroid arrangement, shape, and analogues of fossil and modern invertebrate eggs. Embryos with cleavage cells are evident in at least one cluster. Detailed element analyses show that eggs are primarily preserved as solid silica replacement, and there is a calcite layer covering the eggs replacing the original organic layer. Silicification of intact invertebrate egg clusters is reported here as a new mode of preservation associated with a Burgess Shale type deposit.

  17. Lower Cambrian yolk-pyramid embryos from Southern Shaanxi,China

    Institute of Scientific and Technical Information of China (English)

    CHEN Junyuan; Andreas BRAUN; Dieter WALOSZEK; PENG Qingqing; Andreas MAAS

    2004-01-01

    Phosphatized globules with radially arranged pillars were recently recorded from the Lower Cambrian phosphate deposit, Ningqiang, Shaanxi by Yue and Bengtson. These authors interpreted the globules as blastula stage of embryos and the pillars as blastomeres. On the basis of new additional material, we reinterpret these structures as yolk-pyramid stages of possible arthropod eggs. The 20 embryos under present study range from 380 μm to 600 μm in diameter and contain about 120 pyramids. Some embryos having a higher number of pyramids are tentatively interpreted as slightly later developmental stages of the same animal. These 543-million-year-old embryos may push back the evolutionary history of the arthropods to a deeper time and also suggest that one important pattern of arthropod development was already present at the beginning of the Cambrian.

  18. Experimental mineralization of crustacean eggs: new implications for the fossilization of Precambrian-Cambrian embryos

    Science.gov (United States)

    Hippler, D.; Hu, N.; Steiner, M.; Scholtz, G.; Franz, G.

    2012-05-01

    Phosphatized globular microfossils from the Ediacaran and lower Cambrian of South China represent an impressive record of early animal evolution and development. However, their phylogenetic affinity is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are crucial for a reliable interpretation of their phylogenetic position. We conducted phosphatization experiments on eggs of the marbled crayfish Procambarus that indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope. Our experiments replicated the different preservational stages of degradation observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4 · 2H2O) and calcite. The mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment were likely similar during fossilization of Cambrian embryos.

  19. A chancelloriid-like metazoan from the early Cambrian Chengjiang Lagerstätte, China

    Science.gov (United States)

    Hou, Xianguang; Williams, Mark; Siveter, David J.; Siveter, Derek J.; Gabbott, Sarah; Holwell, David; Harvey, Thomas H. P.

    2014-12-01

    Nidelric pugio gen. et sp. nov. from the Cambrian Series 2 Heilinpu Formation, Chengjiang Lagerstätte, Yunnan Province, China, is an ovoid, sac-like metazoan that bears single-element spines on its surface. N. pugio shows no trace of a gut, coelom, anterior differentiation, appendages, or internal organs that would suggest a bilateral body plan. Instead, the sac-like morphology invites comparison with the radially symmetrical chancelloriids. However, the single-element spines of N. pugio are atypical of the complex multi-element spine rosettes borne by most chancelloriids and N. pugio may signal the ancestral chancelloriid state, in which the spines had not yet fused. Alternatively, N. pugio may represent a group of radial metazoans that are discrete from chancelloriids. Whatever its precise phylogenetic position, N. pugio expands the known disparity of Cambrian scleritome-bearing animals, and provides a new model for reconstructing scleritomes from isolated microfossils.

  20. Cambrian spiral-plated echinoderms from Gondwana reveal the earliest pentaradial body plan.

    Science.gov (United States)

    Smith, Andrew B; Zamora, Samuel

    2013-08-22

    Echinoderms are unique among animal phyla in having a pentaradial body plan, and their fossil record provides critical data on how this novel organization came about by revealing intermediate stages. Here, we report a spiral-plated animal from the early Cambrian of Morocco that is the most primitive pentaradial echinoderm yet discovered. It is intermediate between helicoplacoids (a bizarre group of spiral-bodied echinoderms) and crown-group pentaradiate echinoderms. By filling an important gap, this fossil reveals the common pattern that underpins the body plans of the two major echinoderm clades (pelmatozoans and eleutherozoans), showing that differential growth played an important role in their divergence. It also adds to the striking disparity of novel body plans appearing in the Cambrian explosion.

  1. Eocrinoid echinoderms from the Lower Cambrian Guanshan Fauna in Wuding, Yunnan, China

    Institute of Scientific and Technical Information of China (English)

    HU ShiXue; LUO HuiLin; HOU ShuGuang; Bernd-Dietrich ERDTMANN

    2007-01-01

    This is a brief report of a new occurrence of eocrinoids from the Early Cambrian Wulongqing Formation in Yunnan, China. The eocrinoids from the Guanshan fauna are among the earliest known eocrinoids. Different from many other Early and Middle Cambrian eocrinoids, the Guanshan eocrinoids are characterized by the absence of sutural pores and epispires, the long and spiral brachioles, the extremely long stalk, and the ratio of the length of the stalk versus that of the calyx. The discovery of the eocrinoids from the Guanshan fauna not only provides new information to the investigation of the early evolution of this animal group, but also shed new light on the occurrence and migration of early eocrinoids.

  2. Stratigraphic implications of Sinian-Early Cambrian volcanic ash beds on the Yangtze Platform

    Institute of Scientific and Technical Information of China (English)

    ZHANG Junming; ZHU Maoyan; YANG Aihua; LI Guoxiang; YANG Jinghong; Christoph HEUBECK

    2004-01-01

    Volcanic ash beds from shallow- to deep-water facies strata of the Sinian-Early Cambrian (Meishucunian) on the Yangtze Platform consist of bentonites and tuffites which are readily recognized in the field by their physical features and confirmed by geochemical analyses.Geochemistry suggests that the volcanic ash beds in Meishucunian time are rhyolite and rhyodacite while those in the Qiongzhusian and Sinian are andesite and trachyandesite.The ash beds in the time-equivalent strata, even in different areas display rather similar geochemical features, whereas the ash beds in different strata even in the same areas show large chemical difference.The results suggest that these ash beds can be used for intra- and extra-basinal correlations of the Sinian-Early Cambrian interval on the Yangtze Platform.Additionally, these ash beds suggest high potentials for further U-Pb dating strategies.

  3. Response to "Discussion on the systematic position of the Early Cambrian priapulomorph worms"

    Institute of Scientific and Technical Information of China (English)

    HAN Jian; HU Shixue

    2006-01-01

    @@ Due to the combination of complex states of preservation and taphonomies in Chengjiang fossils, Huang et al.[1] expressed different opinions to those of Han et al.[2] on the morphology and systematic position of the fossil priapulomorph worms (Priapulomorpha) based on their additional materials. These diverse opinions are critical in any investigation of the diversity of the Introverta in the Cambrian explosion. However, some of their ideas need to be discussed in further detail.

  4. Acute vision in the giant Cambrian predator Anomalocaris and the origin of compound eyes.

    Science.gov (United States)

    Paterson, John R; García-Bellido, Diego C; Lee, Michael S Y; Brock, Glenn A; Jago, James B; Edgecombe, Gregory D

    2011-12-07

    Until recently, intricate details of the optical design of non-biomineralized arthropod eyes remained elusive in Cambrian Burgess-Shale-type deposits, despite exceptional preservation of soft-part anatomy in such Konservat-Lagerstätten. The structure and development of ommatidia in arthropod compound eyes support a single origin some time before the latest common ancestor of crown-group arthropods, but the appearance of compound eyes in the arthropod stem group has been poorly constrained in the absence of adequate fossils. Here we report 2-3-cm paired eyes from the early Cambrian (approximately 515 million years old) Emu Bay Shale of South Australia, assigned to the Cambrian apex predator Anomalocaris. Their preserved visual surfaces are composed of at least 16,000 hexagonally packed ommatidial lenses (in a single eye), rivalling the most acute compound eyes in modern arthropods. The specimens show two distinct taphonomic modes, preserved as iron oxide (after pyrite) and calcium phosphate, demonstrating that disparate styles of early diagenetic mineralization can replicate the same type of extracellular tissue (that is, cuticle) within a single Burgess-Shale-type deposit. These fossils also provide compelling evidence for the arthropod affinities of anomalocaridids, push the origin of compound eyes deeper down the arthropod stem lineage, and indicate that the compound eye evolved before such features as a hardened exoskeleton. The inferred acuity of the anomalocaridid eye is consistent with other evidence that these animals were highly mobile visual predators in the water column. The existence of large, macrophagous nektonic predators possessing sharp vision--such as Anomalocaris--within the early Cambrian ecosystem probably helped to accelerate the escalatory 'arms race' that began over half a billion years ago.

  5. A New Leanchoiliid Megacheiran Arthropod from the Lower Cambrian Emu Bay Shale, South Australia

    OpenAIRE

    Edgecombe, Gregory D; Diego C. García-Bellido; Paterson, John R

    2011-01-01

    The Leanchoiliidae is well-known from abundant material of Leanchoilia, from the Burgess Shale and Chengjiang Konservat-Lagerstätten. The first Australian member of the group is Oestokerkus megacholix gen. et sp. nov., described from the Emu Bay Shale (Cambrian Series 2, Stage 4), at Buck Quarry, Kangaroo Island, South Australia, and is intermediate in age between the well known leanchoiliid species from the Burgess Shale and Chengjiang. Phylogenetic analysis of “short great appendage” arthro...

  6. In situ benthos and paleo-oxygenation in the Middle Cambrian Burgess Shale, British Columbia, Canada

    Science.gov (United States)

    Allison, Peter A.; Brett, Carlton E.

    1995-12-01

    The Middle Cambrian Burgess Shale was deposited under variable levels of oxygenation. During periods of oxygenation, low-diversity shell beds were formed and the muds were colonized by infauna. Under these circumstances pyrite was restricted to anoxic microenvironments and formed small (1 mm) discrete aggregated masses. Soft-bodied organisms were preserved under low-oxygen conditions typified by evenly dispersed pyrite, and an absence of trace fossils and shell beds.

  7. Beyond the Burgess Shale: Cambrian microfossils track the rise and fall of hallucigeniid lobopodians

    OpenAIRE

    Caron, Jean-Bernard; Smith, Martin R.; Harvey, Thomas H. P.

    2013-01-01

    Burgess Shale-type deposits are renowned for their exquisite preservation of soft-bodied organisms, representing a range of animal body plans that evolved during the Cambrian ‘explosion’. However, the rarity of these fossil deposits makes it difficult to reconstruct the broader-scale distributions of their constituent organisms. By contrast, microscopic skeletal elements represent an extensive chronicle of early animal evolution—but are difficult to interpret in the absence of corresponding w...

  8. Demecology in the Cambrian: synchronized molting in arthropods from the Burgess Shale

    OpenAIRE

    Haug, Joachim T; Caron, Jean-Bernard; Haug, Carolin

    2013-01-01

    Background The Burgess Shale is well known for its preservation of a diverse soft-bodied biota dating from the Cambrian period (Series 3, Stage 5). While previous paleoecological studies have focused on particular species (autecology) or entire paleocommunities (synecology), studies on the ecology of populations (demecology) of Burgess Shale organisms have remained mainly anecdotal. Results Here, we present evidence for mass molting events in two unrelated arthropods from the Burgess Shale Wa...

  9. Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia

    Science.gov (United States)

    Lee, Michael S. Y.; Jago, James B.; García-Bellido, Diego C.; Edgecombe, Gregory D.; Gehling, James G.; Paterson, John R.

    2011-06-01

    Despite the status of the eye as an ``organ of extreme perfection'', theory suggests that complex eyes can evolve very rapidly. The fossil record has, until now, been inadequate in providing insight into the early evolution of eyes during the initial radiation of many animal groups known as the Cambrian explosion. This is surprising because Cambrian Burgess-Shale-type deposits are replete with exquisitely preserved animals, especially arthropods, that possess eyes. However, with the exception of biomineralized trilobite eyes, virtually nothing is known about the details of their optical design. Here we report exceptionally preserved fossil eyes from the Early Cambrian (~515 million years ago) Emu Bay Shale of South Australia, revealing that some of the earliest arthropods possessed highly advanced compound eyes, each with over 3,000 large ommatidial lenses and a specialized `bright zone'. These are the oldest non-biomineralized eyes known in such detail, with preservation quality exceeding that found in the Burgess Shale and Chengjiang deposits. Non-biomineralized eyes of similar complexity are otherwise unknown until about 85 million years later. The arrangement and size of the lenses indicate that these eyes belonged to an active predator that was capable of seeing in low light. The eyes are more complex than those known from contemporaneous trilobites and are as advanced as those of many living forms. They provide further evidence that the Cambrian explosion involved rapid innovation in fine-scale anatomy as well as gross morphology, and are consistent with the concept that the development of advanced vision helped to drive this great evolutionary event.

  10. Oldest glosselline linguliform brachiopod with soft parts from the Lower Cambrian of Yunnan, Southern China

    OpenAIRE

    Wang, Haizhou; Zhang, Zhifei; Holmer, Lars Erik

    2014-01-01

    Lingulella chengjiangensis Jin, Huo & Wang, 1993 is one of the most abundant brachiopods from the celebrated Lower Cambrian Chengjiang Lagerstätte. A detailed study of abundant new well-preserved specimens clearly shows that their morphology and preserved soft anatomy differ widely from that of the linguliforms of the subfamily Obolinae, including Lingulella. L. chengjiangensis is herein re-described as the probable earliest member of the subfamily Glossellinae, which was previously known...

  11. Genesis mechanism of the Sinian-Cambrian reservoirs in the Anyue Gas Field, Sichuan Basin

    OpenAIRE

    Zhou Jingao; Yao Genshun; Yang Guang; Zhang Jianyong; Hao Yi; Wang Fang; Gu Mingfeng; Li Wenzheng

    2015-01-01

    The Lower Cambrian Longwangmiao Fm, the 4th and 2nd members of the Sinian Dengying Fm are the three major gas layers in the Anyue Gas Field of the Sichuan Basin. Their main characteristics and genesis mechanism were investigated, and the following three findings were obtained. First, according to sedimentary microfacies, lithology and porosity, the Longwangmiao Fm is identified as fractured-vuggy dolomite reservoir of grain shoal facies, the 4th member of the Dengying Fm as fractured-vuggy (c...

  12. Biogeochemical significance of the Precambrian-Cambrian boundary carbon isotope anomaly; constraints from Oman

    OpenAIRE

    Amthor, J. E.; Grotzinger, J. P.; S. Schröder; S. A. Bowring; Matter, A

    2001-01-01

    Globally significant events of faunal turnover, tectonic reorganization, and biogeochemical change are now widely regarded to have closely coincided with the Precambrian. Cambrian boundary. Over the past decade, numerous studies have provided constraints on the age and duration of these events, the possible phylogenetic relationships between faunal assemblages, and the magnitude and significance of· contemporaneous shifts in the trace element composition and isotopic comp...

  13. Cambrian Series 3 carbonate platform of Korea dominated by microbial-sponge reefs

    Science.gov (United States)

    Hong, Jongsun; Lee, Jeong-Hyun; Choh, Suk-Joo; Lee, Dong-Jin

    2016-07-01

    Metazoans have been considered as negligible components of Cambrian Series 3 and Furongian microbial-dominated reefs, in contrast to their presence in earlier Terreneuvian-Cambrian Series 2 microbial-archaeocyath reefs. However, recent discoveries of sponges in Cambrian Series 3-Furongian reefs of Australia, China, Iran, USA, and Korea have raised question regarding their contribution in terms of carbonate platform development, which have never been assessed. This study examines Cambrian Series 3 deposits of the Daegi Formation, Korea to elucidate this question. The 100-m-thick middle part of the Daegi Formation is dominated by boundstone facies, which occupies 45% of the study interval, as well as bioclastic wackestone to packstone, bioclastic grainstone, and ooid packstone to grainstone facies. The Daegi reefs are primarily thrombolitic in composition, with 90% (n = 26/29) of the reefs containing an average of 9% sponges in aerial percentage calculated from thin sections. Lithistid sponges composed of peloidal fabrics, some desma spicules, and spicule networks commonly occupy the interstitial space in microbial clusters, are encrusted by mesoclots and Epiphyton, and are surrounded by micrite. Subordinate non-lithistid demosponges occur within clusters of microbial elements. The middle Daegi Formation can be largely subdivided into shoal environment dominated by grainstone to packstone facies and shallow subtidal platform interior environment located behind shoal with wackestone to packstone facies. The microbial-sponge reefs mainly developed around platform interior as patch reefs. The current study indicates that metazoans in the form of lithistid and non-lithistid demosponges are nearly ubiquitously incorporated in Daegi reefs and contributed greatly to the formation of microbial-sponge reefs as well as carbonate platform during the time. Study of these microbial-sponge reefs and their distribution within the carbonate platform may help us to understand how

  14. Cambrian suspension-feeding lobopodians and the early radiation of panarthropods

    OpenAIRE

    Caron, Jean-Bernard; Aria, Cédric

    2017-01-01

    Background Arthropoda, Tardigrada and Onychophora evolved from lobopodians, a paraphyletic group of disparate Palaeozoic vermiform animals with soft legs. Although the morphological diversity that this group encompasses likely illustrates the importance of niche diversification in the early radiation of panarthropods, the ecology of lobopodians remains poorly characterized. Results Here we describe a new luolishaniid taxon from the middle Cambrian Burgess Shale (Walcott Quarry) in British Col...

  15. Ecological innovations in the Cambrian and the origins of the crown group phyla

    OpenAIRE

    2016-01-01

    Simulation studies of the early origins of the modern phyla in the fossil record, and the rapid diversification that led to them, show that these are inevitable outcomes of rapid and long-lasting radiations. Recent advances in Cambrian stratigraphy have revealed a more precise picture of the early bilaterian radiation taking place during the earliest Terreneuvian Series, although several ambiguities remain. The early period is dominated by various tubes and a moderately diverse trace fossil r...

  16. The influence of diagenesis on the reservoir quality of Cambrian and Carboniferous sandstones, southwest Sinai, Egypt

    Science.gov (United States)

    McBride, Earle F.; Abdel-Wahab, Antar; Salem, Alaa M. K.

    1996-04-01

    The diagenetic influence on hydrocarbon reservoir quality was investigated for the Cambrian and Lower Carboniferous sandstones of southwestern Sinai. These quartzose and feldspathic Palaeozoic sandstones were not buried more than 1 to 1.5 km until Late Cretaceous and more recent times, when the most deeply buried rocks may have reached 25 km. Porosity was reduced by compaction from an assumed original 45% to about 26%. In general, both Cambrian and Carboniferous sandstones lost more porosity by compaction (average of 19% for each) than by cementation (average of 17% and 13%, respectively). There is no significant difference in the degree of compaction shown by Cambrian (older, deeper buried) rather than Carboniferous sandstones. Cementation by iron oxide, quartz, calcite and kaolinite reduced porosity to 12-15%, except in silcretes and some ferricretes where porosity was reduced to <5%. Significant secondary porosity was created (5.8 and 5.1 % for Cambrian and Carboniferous sandstones, respectively ) chiefly by dissolution of feldspar. Kaolinite (maximum of 20%) is the most deleterious cement because it has high microporosity, which causes high residual water saturation, and occurs as tiny crystals that have the potential to break loose during rapid fluid flow and block the pore throats. The present-day porosity in these sandstones averages 19% and ranges from 1.5 to 32%. Many sandstone samples (47% of a total of 178 samples) have permeability values higher than 1000 md. The plot of porosity versus the log of permeability has a good correlation indicating that microporosity, even though locally important, does not significantly influence reservoir quality. In spite of their age and the large volumes of groundwater that probably passed through them, these Palaeozoic sandstones retain sufficient porosity and permeability to possess excellent reservoir quality.

  17. Life cycle and morphology of a cambrian stem-lineage loriciferan.

    Science.gov (United States)

    Peel, John S; Stein, Martin; Kristensen, Reinhardt Møbjerg

    2013-01-01

    Cycloneuralians form a rich and diverse element within Cambrian assemblages of exceptionally preserved fossils. Most resemble priapulid worms whereas other Cycloneuralia (Nematoda, Nematomorpha, Kinorhyncha, Loricifera), well known at the present day, have little or no fossil record. First reports of Sirilorica Peel, 2010 from the lower Cambrian Sirius Passet fauna of North Greenland described a tubular lorica covering the abdomen and part of a well developed introvert with a circlet of 6 grasping denticles near the lorica. The introvert is now known to terminate in a narrow mouth tube, while a conical anal field is also developed. Broad muscular bands between the plates in the lorica indicate that it was capable of movement by rhythmic expansion and contraction of the lorica. Sirilorica is regarded as a macrobenthic member of the stem-lineage of the miniaturised, interstitial, present day Loricifera. Like loriciferans, Sirilorica is now known to have grown by moulting. Evidence of the life cycle of Sirilorica is described, including a large post-larval stage and probably an initial larva similar to that of the middle Cambrian fossil Orstenoloricusshergoldii.

  18. Life cycle and morphology of a cambrian stem-lineage loriciferan.

    Directory of Open Access Journals (Sweden)

    John S Peel

    Full Text Available Cycloneuralians form a rich and diverse element within Cambrian assemblages of exceptionally preserved fossils. Most resemble priapulid worms whereas other Cycloneuralia (Nematoda, Nematomorpha, Kinorhyncha, Loricifera, well known at the present day, have little or no fossil record. First reports of Sirilorica Peel, 2010 from the lower Cambrian Sirius Passet fauna of North Greenland described a tubular lorica covering the abdomen and part of a well developed introvert with a circlet of 6 grasping denticles near the lorica. The introvert is now known to terminate in a narrow mouth tube, while a conical anal field is also developed. Broad muscular bands between the plates in the lorica indicate that it was capable of movement by rhythmic expansion and contraction of the lorica. Sirilorica is regarded as a macrobenthic member of the stem-lineage of the miniaturised, interstitial, present day Loricifera. Like loriciferans, Sirilorica is now known to have grown by moulting. Evidence of the life cycle of Sirilorica is described, including a large post-larval stage and probably an initial larva similar to that of the middle Cambrian fossil Orstenoloricusshergoldii.

  19. Conodont Biostratigraphy of the Middle Cambrian through Lowermost Ordovician in Hunan, South China

    Institute of Scientific and Technical Information of China (English)

    DONG Xiping; John E. REPETSKI; Stig M. BERGSTR(O)M

    2004-01-01

    Since 1985, samples with a total weight of more than 14,000 kg, mainly from three key sections in western and northwestern Hunan, South China, have been processed for conodonts. In strata older than the late Late Cambrian paraconodonts have proved useful for stratigraphic subdivision and correlation. Thirteen conodont zones are proposed in the Middle Cambrian through lowermost Ordovician. The correlation between these zones and those of North China, western U.S.A., western Newfoundland, Canada, and Iran is discussed. In ascending order, these 13 zones are as follows: The Gapparodus bisulcatus-Westergaardodina brevidens Zone, Shandongodus priscus-Hunanognathus tricuspidatus Zone,Westergaardodina quadrata Zone, Westergaardodina matsushitai-W. grandidens Zone, Westergaardodina lui-W. ani Zone,Westergaardodina cf. calix-Prooneotodus rotundatus Zone, Proconodontus tenuiserratus Zone, Proconodontus Zone,Eoconodontus Zone, Cordylodus proavus Zone, Cordylodus intermedius Zone, Cordylodus lindstromi Zone, and Cordylodus angulatus Zone (lower part). The Westergaardodina lui-W. ani and Westergaardodina cf. calix-Prooneotodus rotundatus Zones replace the Westergaardodina proligula and Westergaardodina cf. behrae-Prooneotodus rotundatus Zones, respectively, in the lowermost Upper Cambrian. Two new species (Westergaardodina lui and Westergaardodina ani)and one conditionally identified species (Westergaardodina cf. calix) are described.

  20. Cambrian stem-group annelids and a metameric origin of the annelid head.

    Science.gov (United States)

    Parry, Luke; Vinther, Jakob; Edgecombe, Gregory D

    2015-10-01

    The oldest fossil annelids come from the Early Cambrian Sirius Passet and Guanshan biotas and Middle Cambrian Burgess Shale. While these are among the best preserved polychaete fossils, their relationship to living taxa is contentious, having been interpreted either as members of extant clades or as a grade outside the crown group. New morphological observations from five Cambrian species include the oldest polychaete with head appendages, a new specimen of Pygocirrus from Sirius Passet, and an undescribed form from the Burgess Shale. We propose that the palps of Canadia are on an anterior segment bearing neuropodia and that the head of Phragmochaeta is formed of a segment bearing biramous parapodia and chaetae. The unusual anatomy of these taxa suggests that the head is not differentiated into a prostomium and peristomium, that palps are derived from a modified parapodium and that the annelid head was originally a parapodium-bearing segment. Canadia, Phragmochaeta and the Marble Canyon annelid share the presence of protective notochaetae, interpreted as a primitive character state subsequently lost in Pygocirrus and Burgessochaeta, in which the head is clearly differentiated from the trunk.

  1. Tentaculate fossils from the Cambrian of Canada (British Columbia and China (Yunnan interpreted as primitive deuterostomes.

    Directory of Open Access Journals (Sweden)

    Jean-Bernard Caron

    Full Text Available Molecular and morphological evidence unite the hemichordates and echinoderms as the Ambulacraria, but their earliest history remains almost entirely conjectural. This is on account of the morphological disparity of the ambulacrarians and a paucity of obvious stem-groups. We describe here a new taxon Herpetogaster collinsi gen. et sp. nov. from the Burgess Shale (Middle Cambrian Lagerstätte. This soft-bodied vermiform animal has a pair of elongate dendritic oral tentacles, a flexible stolon with an attachment disc, and a re-curved trunk with at least 13 segments that is directed dextrally. A differentiated but un-looped gut is enclosed in a sac suspended by mesenteries. It consists of a short pharynx, a conspicuous lenticular stomach, followed by a narrow intestine sub-equal in length. This new taxon, together with the Lower Cambrian Phlogites and more intriguingly the hitherto enigmatic discoidal eldoniids (Cambrian-Devonian, form a distinctive clade (herein the cambroernids. Although one hypothesis of their relationships would look to the lophotrochozoans (specifically the entoprocts, we suggest that the evidence is more consistent with their being primitive deuterostomes, with specific comparisons being made to the pterobranch hemichordates and pre-radial echinoderms. On this basis some of the earliest ambulacrarians are interpreted as soft-bodied animals with a muscular stalk, and possessing prominent tentacles.

  2. Tentaculate fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) interpreted as primitive deuterostomes.

    Science.gov (United States)

    Caron, Jean-Bernard; Conway Morris, Simon; Shu, Degan

    2010-03-08

    Molecular and morphological evidence unite the hemichordates and echinoderms as the Ambulacraria, but their earliest history remains almost entirely conjectural. This is on account of the morphological disparity of the ambulacrarians and a paucity of obvious stem-groups. We describe here a new taxon Herpetogaster collinsi gen. et sp. nov. from the Burgess Shale (Middle Cambrian) Lagerstätte. This soft-bodied vermiform animal has a pair of elongate dendritic oral tentacles, a flexible stolon with an attachment disc, and a re-curved trunk with at least 13 segments that is directed dextrally. A differentiated but un-looped gut is enclosed in a sac suspended by mesenteries. It consists of a short pharynx, a conspicuous lenticular stomach, followed by a narrow intestine sub-equal in length. This new taxon, together with the Lower Cambrian Phlogites and more intriguingly the hitherto enigmatic discoidal eldoniids (Cambrian-Devonian), form a distinctive clade (herein the cambroernids). Although one hypothesis of their relationships would look to the lophotrochozoans (specifically the entoprocts), we suggest that the evidence is more consistent with their being primitive deuterostomes, with specific comparisons being made to the pterobranch hemichordates and pre-radial echinoderms. On this basis some of the earliest ambulacrarians are interpreted as soft-bodied animals with a muscular stalk, and possessing prominent tentacles.

  3. Ecological innovations in the Cambrian and the origins of the crown group phyla.

    Science.gov (United States)

    Budd, Graham E; Jackson, Illiam S C

    2016-01-05

    Simulation studies of the early origins of the modern phyla in the fossil record, and the rapid diversification that led to them, show that these are inevitable outcomes of rapid and long-lasting radiations. Recent advances in Cambrian stratigraphy have revealed a more precise picture of the early bilaterian radiation taking place during the earliest Terreneuvian Series, although several ambiguities remain. The early period is dominated by various tubes and a moderately diverse trace fossil record, with the classical 'Tommotian' small shelly biota beginning to appear some millions of years after the base of the Cambrian at ca 541 Ma. The body fossil record of the earliest period contains a few representatives of known groups, but most of the record is of uncertain affinity. Early trace fossils can be assigned to ecdysozoans, but deuterostome and even spiralian trace and body fossils are less clearly represented. One way of explaining the relative lack of clear spiralian fossils until about 536 Ma is to assign the various lowest Cambrian tubes to various stem-group lophotrochozoans, with the implication that the groundplan of the lophotrochozoans included a U-shaped gut and a sessile habit. The implication of this view would be that the vagrant lifestyle of annelids, nemerteans and molluscs would be independently derived from such a sessile ancestor, with potentially important implications for the homology of their sensory and nervous systems.

  4. 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...

  5. Climatic-oceanic forcing on the organic accumulation across the shelf during the Early Cambrian (Age 2 through 3) in the mid-upper Yangtze Block, NE Guizhou, South China

    Science.gov (United States)

    Yeasmin, Rumana; Chen, Daizhao; Fu, Yong; Wang, Jianguo; Guo, Zenghui; Guo, Chuan

    2017-02-01

    The organic-rich sediments were widely deposited over the entire Yangtze Block during the Early Cambrian (late Nemakit-Daldynian to Botomian). In the mid-upper Yangtze region, northeastern Guizhou, South China, they comprise, in ascending order, the Niutitang, Jiumenchong and lower Bianmachong formations which are dominated by black shales except the middle one characterized by interbedded shales-limestones. Three third-order depositional sequences are identified in the two studied sections located on the upper slope to basin of the open shelf. The organic-rich sediments were mostly deposited notably during transgressions on the shallower upper slope-margin (TOC up to 25 wt.%) where they are characterized by co-increases in C, P, Fe, and Ba concentrations, indicating the highest organic productivity and coupled C, P and Fe cycling there. In contrast, in the shelf basin, the concomitant organic-rich sediments yield lower organic (TOC state in the basin due to the relatively low sulfate level. Meanwhile, episodic depletion of trace elements in the deeper basin during the higher organic productivity also reconciles the concomitantly enhanced upwelling from the somewhat restricted deep watermass likely silled by the underwater upland seaward. The coincidence of organic-rich intervals with more arid climate epoches, as shown by increased Ti/Al ratios indicative of increased aeolian fluxes, reconciles a subtropical arid climate of Yangtze Block within the north mid-low-latitude trade-wind zone during deposition (the Early Cambrian). As such, enhanced offshore currents driven by the trade winds could have further induced the upwelling of nutrient-rich deep waters along the shelf during the transgressions, although tended to wane onwards, leading to the tempo-spatial heterogeneities in organic production and redox state across the shelf sea.

  6. Cambrian ensialic rift-related magmatism in the Ossa-Morena Zone (Évora Aracena metamorphic belt, SW Iberian Massif): Sm Nd isotopes and SHRIMP zircon U Th Pb geochronology

    Science.gov (United States)

    Chichorro, M.; Pereira, M. F.; Díaz-Azpiroz, M.; Williams, I. S.; Fernández, C.; Pin, C.; Silva, J. B.

    2008-12-01

    The Late Ediacaran (c. 560-550 Ma) Série Negra sediments of the Évora-Aracena metamorphic belt, Ossa-Morena Zone, SW Iberian Massif, preserve a record of the erosion of an Avalonian-Cadomian magmatic arc and subsequent related turbiditic sedimentation. Detrital zircon from the Série Negra is characterized by predominantly Ediacaran and Cryogenian ages, with few Paleoproterozoic and Archean cores, and a marked lack of Grenvillian ages. These features, when combined with the metasediments' enrichment in LREE (La/Yb = 14), negative Eu-anomalies, low 147Sm/ 144Nd values (0.121) and negative ɛNd 550 = - 5.5, indicate that the protolith Série Negra sediments were derived from a continental magmatic arc. A period of Late Cadomian (ca. 560-540 Ma) tectonism was followed by an extended episode of widespread bimodal magmatism related to Cambrian (ca. 540-500 Ma) rifting. This tectonic inversion is expressed in the geological record by a regional Early Cambrian unconformity. SHRIMP zircon U-Th-Pb ages from four felsic orthogneisses from the Évora Massif record Cambrian (527 ± 10 Ma, 522 ± 5 Ma, 517 ± 6 Ma and 505 ± 5 Ma) crystallization ages for their igneous protoliths. This confirms the existence of widespread Lower Paleozoic igneous activity in the Ossa-Morena Zone: (i) a Lower Cambrian (ca. 535-515 Ma) igneous-felsic dominated-sedimentary complex (with calc-alkaline signature and associated carbonate and siliciclastic deposition), and (ii) a Middle Cambrian-?Ordovician (ca. 515-490 Ma) igneous-bimodal-sedimentary complex (with calc-alkaline and tholeiitic signatures and associated dominant siliciclastic deposition, but also carbonate sediments). The Cambrian felsic magmatism was characterized by negative Eu-anomalies, (La/Lu) N = 0.8-11, 147Sm/ 144Nd = 0.1289-0.1447 and ɛNd 500 ranging from - 1.5 to - 0.8. A tendency towards peraluminous compositions suggests late fractionation, low degrees of partial melting, or the mixing of crustal and mantle

  7. Evolution of oceanic molybdenum and uranium reservoir size around the Ediacaran-Cambrian transition: Evidence from western Zhejiang, South China

    Science.gov (United States)

    Xiang, Lei; Schoepfer, Shane D.; Shen, Shu-zhong; Cao, Chang-qun; Zhang, Hua

    2017-04-01

    The ;Cambrian explosion; is one of the most fascinating episodes of diversification in the history of life; however, its relationship to the oxygenation of the oceans and atmosphere around the Ediacaran-Cambrian transition is not fully understood. Marine inventories of redox-sensitive trace elements reflect the relative balance of oxidative weathering on land and deposition in anoxic water masses, and can be used to explore the evolution of oceanic and atmospheric redox conditions. For this study, we conducted a series of geochemical analyses on the upper Lantian, Piyuancun, and Hetang formations in the Chunye-1 well, part of the lower Yangtze Block in western Zhejiang. Iron speciation results indicate that the entire studied interval was deposited under anoxic conditions, with three intervals of persistent euxinia occurring in the uppermost Lantian Fm., the lower Hetang Formation (Fm.), and the upper Hetang Fm. Molybdenum (Mo) and uranium (U) contents and Mo/TOC and U/TOC ratios from the anoxic/euxinic intervals of the Chunye-1 well, combined with published data from the sections in the middle and upper Yangtze Block, suggest that the oceanic Mo reservoir declined consistently from the Ediacaran to Cambrian Stage 3, while the size of the oceanic U reservoir remained relatively constant. Both metals were depleted in the ocean in lower Cambrian Stage 4, before increasing markedly at the end of Stage 4. The lack of an apparent increase in the size of the marine Mo and U reservoir from the upper Ediacaran to Cambrian Stage 3 suggests that oxic water masses did not expand until Cambrian Stage 4. The increase in marine Mo and U availability in the upper Hetang Fm. may have been due to the expansion of oxic water masses in the oceans, associated with oxygenation of the atmosphere during Cambrian Stage 4. This expansion of oxic waters in the global ocean postdates the main phase of Cambrian diversification, suggesting that pervasive oxygenation of the ocean on a large

  8. Controls on gut phosphatisation: the trilobites from the Weeks Formation Lagerstatte (Cambrian; Utah.

    Directory of Open Access Journals (Sweden)

    Rudy Lerosey-Aubril

    Full Text Available Despite being internal organs, digestive structures are frequently preserved in Cambrian Lagerstätten. However, the reasons for their fossilisation and their biological implications remain to be thoroughly explored. This is particularly true with arthropods--typically the most diverse fossilised organisms in Cambrian ecosystems--where digestive structures represent an as-yet underexploited alternative to appendage morphology for inferences on their biology. Here we describe the phosphatised digestive structures of three trilobite species from the Cambrian Weeks Formation Lagerstätte (Utah. Their exquisite, three-dimensional preservation reveals unique details on trilobite internal anatomy, such as the position of the mouth and the absence of a differentiated crop. In addition, the presence of paired pygidial organs of an unknown function is reported for the first time. This exceptional material enables exploration of the relationships between gut phosphatisation and the biology of organisms. Indeed, soft-tissue preservation is unusual in these fossils as it is restricted to the digestive structures, which indicates that the gut played a central role in its own phosphatisation. We hypothesize that the gut provided a microenvironment where special conditions could develop and harboured a source of phosphorus. The fact that gut phosphatization has almost exclusively been observed in arthropods could be explained by their uncommon ability to store ions (including phosphorous in their digestive tissues. However, in some specimens from the Weeks Formation, the phosphatisation extends to the entire digestive system, suggesting that trilobites might have had some biological particularities not observed in modern arthropods. We speculate that one of them might have been an increased capacity for ion storage in the gut tissues, related to the moulting of their heavily-mineralised carapace.

  9. A Cambrian micro-lobopodian and the evolution of arthropod locomotion and reproduction

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The evolutionary success of arthropods, the most abundant and diverse animal group, is mainly based on their segmented body and jointed appendages, features that had evolved most likely already before the Cambrian. The first arthropod-like animals, the lobopodians from the Early Cambrian, were unsclerotized and worm-like, and they had unjointed tubular legs. Here we describe the first three-dimensionally preserved Cambrian lobopodian. The material presented of Orstenotubulus evamuellerae gen. et sp. nov. is the smallest and youngest of a lobopodian known. O. evamuellerae shows strikingly detailed similarities to Recent tardigrades and/or onychophorans in its cellular-structured cuticle and the telescopic spines. It also shows similarities to other, longer known lobopodians, but which are ten times as large as the new form. These similarities include the finely annulated body and legs, which is characteristic also for Recent onychophorans, and paired humps continuing into spines situated dorsally to the leg insertions, a feature lacking in the extant forms. The morphology of O. evamuellerae not only elucidates our knowledge about lobopodians, but also aids in a clearer picture of the early evolution of arthropods. An example is the single ventral gonopore between a limb pair of O. evamuellerae, which indicates that a single gonopore, as developed in onychophorans, tardigrades, pentastomids, myriapods and insects, might represent the plesiomorphic state for Arthropoda, while the paired state in chelicerates and crustaceans was convergently achieved. Concerning life habits, the lateral orientation of the limbs and their anchoring spines of the new lobopodian imply that early arthropods were crawlers rather than walkers.

  10. Controls on gut phosphatisation: the trilobites from the Weeks Formation Lagerstätte (Cambrian; Utah).

    Science.gov (United States)

    Lerosey-Aubril, Rudy; Hegna, Thomas A; Kier, Carlo; Bonino, Enrico; Habersetzer, Jörg; Carré, Matthieu

    2012-01-01

    Despite being internal organs, digestive structures are frequently preserved in Cambrian Lagerstätten. However, the reasons for their fossilisation and their biological implications remain to be thoroughly explored. This is particularly true with arthropods--typically the most diverse fossilised organisms in Cambrian ecosystems--where digestive structures represent an as-yet underexploited alternative to appendage morphology for inferences on their biology. Here we describe the phosphatised digestive structures of three trilobite species from the Cambrian Weeks Formation Lagerstätte (Utah). Their exquisite, three-dimensional preservation reveals unique details on trilobite internal anatomy, such as the position of the mouth and the absence of a differentiated crop. In addition, the presence of paired pygidial organs of an unknown function is reported for the first time. This exceptional material enables exploration of the relationships between gut phosphatisation and the biology of organisms. Indeed, soft-tissue preservation is unusual in these fossils as it is restricted to the digestive structures, which indicates that the gut played a central role in its own phosphatisation. We hypothesize that the gut provided a microenvironment where special conditions could develop and harboured a source of phosphorus. The fact that gut phosphatization has almost exclusively been observed in arthropods could be explained by their uncommon ability to store ions (including phosphorous) in their digestive tissues. However, in some specimens from the Weeks Formation, the phosphatisation extends to the entire digestive system, suggesting that trilobites might have had some biological particularities not observed in modern arthropods. We speculate that one of them might have been an increased capacity for ion storage in the gut tissues, related to the moulting of their heavily-mineralised carapace.

  11. 3D-Mapping of Dolomitized Structures in Lower Cambrian Phosphorites

    Science.gov (United States)

    Hippler, Dorothee; Stammeier, Jessica A.; Brunner, Roland; Rosc, Jördis; Franz, Gerhard; Dietzel, Martin

    2016-04-01

    Dolomitization is a widespread phenomenon in ancient sedimentary rocks, particularly close to the Precambrian-Cambrian boundary. Dolomite can form in synsedimentary or hydrothermal environments, preferentially via the replacement of solid carbonate precursor phases. Synsedimentary dolomite formation is often associated with microbial activity, such as bacterial sulfate reduction or methanogenesis. In this study, we investigate dolomitic phosphorites from the Lowermost Cambrian Tal Group, Mussoori Syncline, Lesser Himalaya, India, using micro-CT 3D-mapping, in order to unravel the complex diagenetic history of the rocks. The selected sample shows alternating layering of phosphatic mudstones and sparitic dolostone, in which brecciated layers of phosphorite or phosphatic mudstones are immersed in a dolomite-rich matrix. Lamination occurs on a sub-millimetre scale, with lamination sometimes wavy to crinkly. This fabric is interpreted as former microbial mats, providing the environment for early diagenetic phosphatization. Preliminary electron backscatter imaging with scanning microscopy revealed that dolomite crystals often occur in spherical to ellipsoidal structures, typically with a high porosity. This dolomite is associated with botryoidal apatite, organic matter and small amounts of calcite. Micro-CT 3D-mappings reveal that dolomite structures are cigar-shaped, elongated and up to 600 μm long. They are further arranged in a Mikado-like oriented framework spanning a layer thickness of a few millimetres. Analyses of ambient pore space, with similar elongated outlines and filled with organic matter, suggest a potential coherence of ambient pore space and shape of the dolomite structures. Allowing for other associated mineral phases, such as pyrite and silicates, and their spatial distribution, the present approach can be used to unravel distinct diagenetic reaction pathways, and might thus constrain the proxy potential of these Lower Cambrian dolomitic phosphorites

  12. Sourcing sediment using multiple tracers in the catchment of Lake Argyle, Northwestern Australia.

    Science.gov (United States)

    Wasson, R J; Caitcheon, Gary; Murray, Andrew S; McCulloch, Malcolm; Quade, Jay

    2002-05-01

    Control of sedimentation in large reservoirs requires soil conservation at the catchment scale. In large, heterogeneous catchments, soil conservation planning needs to be based on sound information, and set within the framework of a sediment budget to ensure that all of the potentially significant sources and sinks are considered. The major sources of sediment reaching the reservoir, Lake Argyle, in tropical northwestern Australia, have been determined by combining measured sediment fluxes in rivers with spatial tracer-based estimates of proportional contributions from tributaries of the main stream entering the lake, the Ord River. The spatial tracers used are mineral particle magnetics, the strontium isotopic ratio, and the neodymium isotopic ratio. Fallout of 137Cs has been used to estimate the proportion of the sediment in Lake Argyle eroded from surface soils by sheet and rill erosion, and, by difference, the proportion eroded from subsurface soils by gully and channel erosion. About 96% of the sediment in the reservoir has come from less than 10% of the catchment, in the area of highly erodible soils formed on Cambrian-age sedimentary rocks. About 80% of the sediment in the reservoir has come from gully and channel erosion. A major catchment revegetation program, designed to slow sedimentation in the reservoir, appears to have had little effect because it did not target gullies, the major source of sediment. Had knowledge of the sediment budget been available before the revegetation program was designed, an entirely different approach would have been taken.

  13. Carbon isotope composition and correlation across the Cambrian-Ordovician boundary in Kalpin Region of the Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    JING XiuChun; DENG ShengHui; ZHAO ZongJu; LU YuanZheng; ZHANG ShiBen

    2008-01-01

    Biostratigraphically constrained sequences at the Wushi Yingshan and Kalpin Cement Plant sections (Kalpin Region; Tarim Basin) were densely sampled for geochemical studies.Carbonates across the Cambrian-Ordovician boundary of both sections mainly record negative carbon isotope values.Stable isotope curves show four negative and four positive excursions appearing alternately at the Wushi Yingshan section and five negative alternating with five positive excursions at the Kalpin Cement Plant section.The carbon isotope logs of these two sections are correlated with the international Cambrian-Ordovician boundary key sections: (1) Dayangcha section in China, (2) Green Point section in Canada, (3) Black mountain section in Australia and (4) Lowson Cove section in USA.These correlations suggest that the Cambrian-Ordovician boundary of the Wushi Yingshan section and the Kalpin Cement Plant section can be placed within a particular horizon that also corresponds to the observed biostratigraphic units.

  14. Carbon isotope composition and correlation across the Cambrian-Ordovician boundary in Kalpin Region of the Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Biostratigraphically constrained sequences at the Wushi Yingshan and Kalpin Cement Plant sections (Kalpin Region; Tarim Basin) were densely sampled for geochemical studies. Carbonates across the Cambrian-Ordovician boundary of both sections mainly record negative carbon isotope values. Stable isotope curves show four negative and four positive excursions appearing alternately at the Wushi Yingshan section and five negative alternating with five positive excursions at the Kalpin Cement Plant section. The carbon isotope logs of these two sections are correlated with the international Cambrian-Ordovician boundary key sections: (1) Dayangcha section in China, (2) Green Point section in Canada, (3) Black mountain section in Australia and (4) Lowson Cove section in USA. These correlations suggest that the Cambrian-Ordovician boundary of the Wushi Yingshan section and the Kalpin Cement Plant section can be placed within a particular horizon that also corresponds to the observed biostratigraphic units.

  15. New Record of Palaeoscolecids from the Early Cambrian of Yunnan, China

    Institute of Scientific and Technical Information of China (English)

    HU Shixue; LI Yong; LUO Huilin; FU Xiaoping; YOU Ting; PANG Jiyuan; LIU Qi; Michael STEINER

    2008-01-01

    A new palaeoscolecid, Guanduscolex minor Hu, Luo et Fu gen. et sp. nov., with preserved soft parts of introvert and intestines comes from the Lower Cambrian Guanshan fauna of Yunnan,South China. Microstructural details of the cuticle revealed by scanning electron microscopy (SEM)show that each annulation bears three rows of plates and each plate bears 9-10 marginal and 4-5 central nodes. This discovery sheds new light on the relationships and evolutionary pathway of the palaeoscolecids and other early priapulids.

  16. Early Cambrian phosphatized blastula-and gastrula-stage animal fossils from southern Shaanxi

    Institute of Scientific and Technical Information of China (English)

    HUA Hong; CHEN Zhe; ZHANG Luyi

    2004-01-01

    Marine invertebrate animal embryos and their early developmental products are of great significance to the study of taxonomy and phylogeny of early animals. A great number of phosphatized globular fossils were collected from the early Cambrian Kuanchuanpu Member (upper Dengying Formation), southern Shaanxi, and a nearly complete developmental sequence--from a fertilized egg, via blastodisc formation, blastula development, blastodisc enlargement toward gastrulae, to tissue differentiation--can be discerned in this collection. This discovery provides unmatchable material for studies on the origin, taxonomy, radiation,and ontogeny of early metazoans.

  17. Organic carbon isotopes of the Sinian and Early Cambrian black shales on Yangtze Platform, China

    Institute of Scientific and Technical Information of China (English)

    李任伟; 卢家烂; 张淑坤; 雷加锦

    1999-01-01

    Organic matter of the Sinian and early Cambrian black shales on the Yangtze Platform belongs to the light carbon group of isotopes with the δ13C values from - 27 % to -35 % , which are lower than those of the contemporaneously deposited carbonates and phosphorites. A carbon isotope-stratified paleooceanographic model caused by upwelling is proposed, which can be used not only to interpret the characteristics of organic carbon isotopic compositions of the black shales, but also to interpret the paleogeographic difference in the organic carbon isotope compositions of various types of sedimentary rocks.

  18. Peritidal lithologies of Cambrian carbonate islands, Carrara Formation, southern Great Basin

    Science.gov (United States)

    Halley, Robert B.

    1975-01-01

    The Carrara Formation is a heterogeneous sequence of quartzites, siltstones, shales, limestones, dolostones, and mixed terrigenous-carbonate rocks. It is Early and Middle Cambrian in age (Stewart, 1970; Palmer, 1971). Figure 32-1 illustrates the general distribution of Carrara lithologies along a transect approximately normal to depositional strike (Fig. 32-2). The formation contains three “grand cycles” (Aitken, 1966; Palmer, 1971), which terminate at the top of massive limestone members. A fourth cycle begins with the uppermost shale of section 9 and is not illustrated in sections 3 through 8. This fourth cycle grades into the overlying Bonanza King Formation.

  19. Stratigraphic Implications of Skeletal Microfossils from the Cambrian of Korea: A Preliminary Report

    Institute of Scientific and Technical Information of China (English)

    Byung-Su LEE

    2008-01-01

    Diverse small shelly fossils and other associated fossils were recently recovered from the Cambrian Hanaeri section, southwestern Mungyeong, Korea. The fauna includes conoidal problematica, poriferans (sponge spicules), coeloscleritophorans (chancelloriids), brachiopods, monoplacophorans, trilobite (?) fragments, echinoderms, and conodonts. A preliminary assessment of fauna! associations, Stratigraphic implications, and the correlation of these skeletal fossils is given, based on occurrences of Actinotheca cf. mira (He), Microcornus sp., Torellela laevigata (Linnarsson), Torellela sp., Archiasterella quadratina Lee, Chancelloria sp., Lingulella sp., Prototreta sp., Phakelodus tennis (Miiller), Phakelodus elongates (An), Hertzina sp., and Furnishina sp.

  20. Vermicular fossils in the Early Cambrian Xidashan Formation in the Quruqtagh region of Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    YANG Ruidong; ZHANG Chuanlin; SONG Guoqi; LUO Xinrong

    2006-01-01

    Large amounts of vermicular fossils and a minor amount of sponge animal fossils have been found in the Early Cambrian Xidashan Formation in the region of Quruqtagh, Xinjiang. Vermicular fossils are generally more than 50 mm long and 0.3-1.4 mm wide; their wrinkled lamellae are microfine with 3-10 pieces within the length of every each millimeter. The fossils are considered to be Sabellidites cambriensis Sokolov (1965). The Xidashan Formation is the highest stratum in which Sabellidites occur, as has been so far reported.

  1. Pediculate Brachiopod Diandongia pista from the Lower Cambrian of South China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhifei; HAN Jian; ZHANG Xingliang; LIU Jianni; SHU Degan

    2003-01-01

    The Chengjiang Lagerstatte has been celebrated for prolific soft-bodied fossils. Based on specimens recentlyexcavated in the Chengjiang Lagerstatte by the Early Life Institute, Northwest University, Diandongiapista Rong, 1974, isdirectly revealed to be a pediculate brachiopod, assigned to the Family Botsfordiidae, as is further confirmed by theexceptionally preserved vascular system including dorsal and ventral mantle canals. These specimens described hereinexhibit some peculiarities, notably the extremely thin and long pedicles, which suggest that Diandongia is epifaunal ratherthan burrowing brachiopod. A study of this group of animals indicates that they may be vital to understand the relationshipbetween the lingulids and the remaining brachiopods, and the character evolution of the early Cambrian brachiopods.

  2. A molecular and isotopic study of palaeoenvironmental conditions through the middle Cambrian in the Georgina Basin, central Australia

    Science.gov (United States)

    Pagès, Anais; Schmid, Susanne; Edwards, Dianne; Barnes, Stephen; He, Nannan; Grice, Kliti

    2016-08-01

    The Cambrian period marks an important point in Earth's history with profound changes in the ocean's biogeochemistry and the occurrence of the most significant evolutionary event in the history of life, the Cambrian explosion. The Cambrian explosion is described as a succession of complex cycles of extinctions and radiations. This study integrates biomarkers and their compound-specific stable carbon isotopes to investigate the palaeoenvironmental depositional conditions in middle Cambrian (Series 3) sedimentary rocks (Thorntonia Limestone, Inca Formation and Currant Bush Limestone) from two drillholes in the Undilla Sub-basin in the eastern Georgina Basin, central Australia. The occurrence of photic zone euxinia (PZE) was detected throughout these three formations by the identification of green sulfur bacteria Chlorobiaceae-derived biomarkers, including a series of 2,3,6-aryl isoprenoids and the intact biomarker isorenieratane. Pulses of enhanced PZE conditions were detected in two core intervals (90-110 mKB, Currant Bush Limestone and 170-200 mKB, Inca Formation) by an increase in the 2,3,6-aryl isoprenoids and C19 biphenyl concentrations. These enhanced PZE conditions were followed by blooms of phytoplankton, as demonstrated by the increase in algal-derived biomarker (i.e. pristane, phytane and the C19n-alkane) concentrations and compound-specific isotopes. These observations confirm that palaeoenvironmental conditions were similar to those reported for the Permian/Triassic and Triassic/Jurassic mass extinction events. The sterane distributions varied across the three formations reflecting possible changes in the phytoplanktonic communities through time. Although a rise in atmospheric oxygen during the Cambrian has been previously associated with the rapid evolution of metazoans, the ecological challenges related to widespread anoxia must have had a major influence on the evolution of life in Cambrian oceans.

  3. Cambrian Evolutionary Radiation: Context, correlation, and chronostratigraphy—Overcoming deficiencies of the first appearance datum (FAD) concept

    Science.gov (United States)

    Landing, Ed; Geyer, Gerd; Brasier, Martin D.; Bowring, Samuel A.

    2013-08-01

    Use of the first appearance datum (FAD) of a fossil to define a global chronostratigraphic unit's base can lead to intractable correlation and stability problems. FADs are diachronous—they reflect species' evolutionary history, dispersal, biofacies, preservation, collection, and taxonomy. The Cambrian Evolutionary Radiation is characterised by diachronous FADs, biofacies controls, and provincialism of taxa and ecological communities that confound a stable Lower Cambrian chronostratigraphy. Cambrian series and stage definitions require greater attention to assemblage zone successions and non-biostratigraphic, particularly carbon isotope, correlation techniques such as those that define the Ediacaran System base. A redefined, basal Cambrian Trichophycus pedum Assemblage Zone lies above the highest Ediacaran-type biotas (vendobionts, putative metazoans, and calcareous problematica such as Cloudina) and the basal Asteridium tornatum-Comasphaeridium velvetum Zone (acritarchs). This definition and the likely close correspondence of evolutionary origin and local FAD of T. pedum preserves the Fortune Head, Newfoundland, GSSP of the Cambrian base and allows the presence of sub-Cambrian, branched ichnofossils. The sub-Tommotian-equivalent base of Stage 2 (a suggested "Laolinian Stage") should be defined by the I'/L4/ZHUCE δ13C positive peak, bracketed by the lower ranges of Watsonella crosbyi and Aldanella attleborensis (molluscs) and the Skiagia ornata-Fimbrioglomerella membranacea Zone (acritarchs). The W. crosbyi and A. attleborensis FADs cannot define a Stage 2 base as they are diachronous even in the Newfoundland "type" W. crosbyi Zone. The Series 2 base cannot be based on a species' FAD owing to the provincialism of skeletalised metazoans in the Terreneuvian-Series 2 boundary interval and global heterochrony of the oldest trilobites. A Series 2 and Stage 3 (a suggested "Lenaldanian Series" and "Zhurinskyan Stage," new) GSSP base is proposed at the Siberian lower

  4. Sequence stratigraphy of the Upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: Transgressing assumptions of cratonic flooding

    Science.gov (United States)

    Eoff, Jennifer D.

    2014-01-01

    New data from detailed measured sections permit comprehensive analysis of the sequence framework of the Furongian (Upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. The sequence-stratigraphic architecture of the lower part of the Sunwaptan Stage at the base of the Tunnel City Group, at the contact between the Wonewoc Formation and Lone Rock Formation, records the first part of complex polyphase flooding (Sauk III) of the Laurentian craton, at a scale smaller than most events recorded by global sea-level curves. Flat-pebble conglomerate and glauconite document transgressive ravinement and development of a condensed section when creation of accommodation exceeded its consumption by sedimentation. Thinly-bedded, fossiliferous sandstone represents the most distal setting during earliest highstand. Subsequent deposition of sandstone characterized by hummocky or trough cross-stratification records progradational pulses of shallower, storm- and wave-dominated environments across the craton before final flooding of Sauk III commenced with carbonate deposition during the middle part of the Sunwaptan Stage. Comparison of early Sunwaptan flooding of the inner Laurentian craton to published interpretations from other parts of North America suggests that Sauk III was not a single, long-term accommodation event as previously proposed.

  5. Molecular timetrees reveal a Cambrian colonization of land and a new scenario for ecdysozoan evolution.

    Science.gov (United States)

    Rota-Stabelli, Omar; Daley, Allison C; Pisani, Davide

    2013-03-04

    Ecdysozoans have been key components of ecosystems since the early Cambrian, when trilobites and soft-bodied Burgess Shale-type ecdysozoans dominated marine animal communities. Even today, the most abundant animals on Earth are either nematode worms or plankton-forming crustaceans, whereas the most diverse are the insects. Throughout geological time, several ecdysozoan lineages independently colonized land, shaping both marine and terrestrial ecosystems and providing an adequate environment for successive animal terrestrialization. The timing of these events is largely uncertain and has been investigated only partially using molecular data. Here we present a timescale of ecdysozoan evolution based on multiple molecular data sets, the most complete set of fossil calibrations to date, and a thorough series of validation analyses. Results converge on an Ediacaran origin of all major ecdysozoan lineages (∼587-543 million years ago [mya]), followed by a fast Cambrian radiation of the pancrustaceans (∼539-511 mya), a Cambro-Ordovician colonization of land of different arthropod lineages (∼510-471 mya), and a relatively recent radiation of extant nematodes, onychophorans, and tardigrades (∼442 mya). Arthropods colonized land nearly synchronously with land plants. Further diversification within flying insects, nematodes and onychophorans might be related to the evolution of vascular plants and forests.

  6. Brachiopods hitching a ride: an early case of commensalism in the middle Cambrian Burgess Shale

    Science.gov (United States)

    Topper, Timothy P.; Holmer, Lars E.; Caron, Jean-Bernard

    2014-10-01

    Ecological interactions, including symbiotic associations such as mutualism, parasitism and commensalism are crucial factors in generating evolutionary novelties and strategies. Direct examples of species interactions in the fossil record generally involve organisms attached to sessile organisms in an epibiont or macroboring relationship. Here we provide support for an intimate ecological association between a calcareous brachiopod (Nisusia) and the stem group mollusc Wiwaxia from the Burgess Shale. Brachiopod specimens are fixed to Wiwaxia scleritomes, the latter showing no signs of decay and disarticulation, suggesting a live association. We interpret this association as the oldest unambiguous example of a facultative ectosymbiosis between a sessile organism and a mobile benthic animal in the fossil record. The potential evolutionary advantage of this association is discussed, brachiopods benefiting from ease of attachment, increased food supply, avoidance of turbid benthic conditions, biofoul and possible protection from predators, suggesting commensalism (benefiting the symbiont with no impact for the host). While Cambrian brachiopods are relatively common epibionts, in particular on sponges, the association of Nisusia with the motile Wiwaxia is rare for a brachiopod species, fossil or living, and suggests that symbiotic associations were already well established and diversified by the ``middle'' (Series 3, Stage 5) Cambrian.

  7. A predatory bivalved euarthropod from the Cambrian (Stage 3) Xiaoshiba Lagerstätte, South China

    Science.gov (United States)

    Yang, Jie; Ortega-Hernández, Javier; Lan, Tian; Hou, Jin-Bo; Zhang, Xi-Guang

    2016-06-01

    Bivalved euarthropods represent a conspicuous component of exceptionally-preserved fossil biotas throughout the Lower Palaeozoic. However, most of these taxa are known from isolated valves, and thus there is a limited understanding of their morphological organization and palaeoecology in the context of early animal-dominated communities. The bivalved euarthropod Clypecaris serrata sp. nov., recovered from the Cambrian (Stage 3) Hongjingshao Formation in Kunming, southern China, is characterized by having a robust first pair of raptorial appendages that bear well-developed ventral-facing spines, paired dorsal spines on the trunk, and posteriorly oriented serrations on the anteroventral margins of both valves. The raptorial limbs of C. serrata were adapted for grasping prey employing a descending stroke for transporting it close the mouth, whereas the backwards-facing marginal serrations of the bivalved carapace may have helped to secure the food items during feeding. The new taxon offers novel insights on the morphology of the enigmatic genus Clypecaris, and indicates that the possession of paired dorsal spines is a diagnostic trait of the Family Clypecarididae within upper stem-group Euarthropoda. C. serrata evinces functional adaptations for an active predatory lifestyle within the context of Cambrian bivalved euarthropods, and contributes towards the better understanding of feeding diversity in early ecosystems.

  8. Experimental mineralization of crustacean eggs: new implications for the fossilization of Precambrian–Cambrian embryos

    Directory of Open Access Journals (Sweden)

    D. Hippler

    2012-05-01

    Full Text Available Phosphatized globular microfossils from the Ediacaran and lower Cambrian of South China represent an impressive record of early animal evolution and development. However, their phylogenetic affinity is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are crucial for a reliable interpretation of their phylogenetic position. We conducted phosphatization experiments on eggs of the marbled crayfish Procambarus that indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope. Our experiments replicated the different preservational stages of degradation observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4 · 2H2O and calcite. The mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment were likely similar during fossilization of Cambrian embryos.

  9. Decoupling biogeochemical records, extinction, and environmental change during the Cambrian SPICE event

    Science.gov (United States)

    Schiffbauer, James D.; Huntley, John Warren; Fike, David A.; Jeffrey, Matthew Jarrell; Gregg, Jay M.; Shelton, Kevin L.

    2017-01-01

    Several positive carbon isotope excursions in Lower Paleozoic rocks, including the prominent Upper Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE), are thought to reflect intermittent perturbations in the hydrosphere-biosphere system. Models explaining these secular changes are abundant, but the synchronicity and regional variation of the isotope signals are not well understood. Examination of cores across a paleodepth gradient in the Upper Cambrian central Missouri intrashelf basin (United States) reveals a time-transgressive, facies-dependent nature of the SPICE. Although the SPICE event may be a global signal, the manner in which it is recorded in rocks should and does vary as a function of facies and carbonate platform geometry. We call for a paradigm shift to better constrain facies, stratigraphic, and biostratigraphic architecture and to apply these observations to the variability in magnitude, stratigraphic extent, and timing of the SPICE signal, as well as other biogeochemical perturbations, to elucidate the complex processes driving the ocean-carbonate system. PMID:28275734

  10. Kodymirus and the case for convergence of raptorial appendages in Cambrian arthropods

    Science.gov (United States)

    Lamsdell, James C.; Stein, Martin; Selden, Paul A.

    2013-09-01

    Kodymirus vagans Chlupáč and Havlíček in Sb Geol Ved Paleontol 6:7-20, 1965 is redescribed as an aglaspidid-like arthropod bearing a single pair of enlarged raptorial appendages, which are shown to be the second cephalic appendage. A number of early Palaeozoic arthropods, recognized from predominantly Cambrian Konservat-Lagerstätten, are known to have borne single pairs of large raptorial appendages. They are well established for the iconic yet problematic anomalocarids, the common megacheirans, and the ubiquitous bivalved Isoxys. Further taxa, such as fuxianhuiids and Branchiocaris, have been reported to have single pairs of specialized cephalic appendages, i.e., appendages differentiated from a largely homonomous limbs series, members of which act in metachronal motion. The homology of these raptorial appendages across these Cambrian arthropods has often been assumed, despite differences in morphology. Thus, anomalocaridids, for instance, have long multiarticulate "frontal appendages" consisting of many articles bearing an armature of paired serial spines, while megacheirans and Isoxys have short "great appendages" consisting of few articles with well-developed endites or elongate fingers. Homology of these appendages would require them to belong to the same cephalic segment. We argue based on morphological evidence that, to the contrary, the raptorial appendages of some of these taxa can be shown to belong to different cephalic segments and are the result of convergence in life habits. K. vagans is yet another important example for this, representing an instance for this morphology from a marginal marine environment.

  11. GEOLOGICAL MARKS OF A POSSIBLE EXTRATERRESTRIAL IMPACT EVENT ON THE BOUNDARY BETWEEN SINIAN/CAMBRIAN IN TIANMENSHAN IN WESTERN HUNAN

    Institute of Scientific and Technical Information of China (English)

    HUANG Huaiyong; WANG Daojing; CHEN Guanghao; YIN Hanhui

    2004-01-01

    Geologic marks related to extraterrestrial impact events, such as impact split gravels, impact brecciate layers, impact dikes, microirghizites, microtektites, especially meteoritic residues, were discovered on the boundary between Sinian/Cambrian at Tianmenshan of Western Hunan, which may possibly demonstrate that an extraterrestrial impact event has ever occurred there on the S/C boundary.

  12. Experimental mineralization of crustacean eggs leads to surprising tissue conservation: new implications for the fossilization of Precambrian-Cambrian embryos

    OpenAIRE

    2011-01-01

    Phosphatized globular microfossils from the Ediacaran and Lower Cambrian of South China represent an impressive record of early animal evolution and development, however their affinity based on putative embryonic metazoan, bacterial and inorganic features is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are therefore crucial for a reliable interpretation of their phylogenetic position. Taphonomic experime...

  13. The paleomagnetism of the Salt Pseudomorph Beds of Middle Cambrian age from the Salt Range, West Pakistan

    NARCIS (Netherlands)

    Wensink, H.

    1972-01-01

    Oriented cores for a paleomagnetic investigation were collected from ten sites in the sedimentary redbeds of the Salt Pseudomorph Beds of Middle Cambrian age in the Salt Range near Khewra. All samples were subjected to progressive, thermal demagnetization procedures which revealed the characteristic

  14. The paleomagnetism of the salt pseudomorph beds of middle cambrian age from the salt range, West Pakistan

    NARCIS (Netherlands)

    Wensink, H.

    1972-01-01

    Oriented cores for a paleomagnetic investigation were collected from ten sites in the sedimentary redbeds of the Salt Pseudomorph Beds of Middle Cambrian age m the Salt Range near Khcwra. All samples were subjected to progressive, thermal demagnetization procedures which revealed the characteristic

  15. Negative carbon isotopic excursion on the Lower/Middle Cambrian boundary of Kaili Formation, Taijiang County,Guizhou Province, China: Implications for mass extinction and stratigraphic division and correlation

    Institute of Scientific and Technical Information of China (English)

    YANG; Ruidong(杨瑞东); ZHU; Lijun(朱立军); WANG; Shijie(王世杰)

    2003-01-01

    The stratigraphic division and correlation of the Lower/Middle Cambrian boundary is a global problem that has not yet been perfectly solved up to now. That is because there existed two global biogeographic regions during the period from Early Cambrian to Middle Cambrian. Although much work has been done from the angle of paleontology and great achievements have been acquired in this aspect, no biological assemblage has yet been established for global stratigraphic correlations due to the coexistence of the two global biogeographic regions -- the Atlantic biogeographic region and the Indian-Pacific biogeographic region during the Early-Middle Cambrian. So, to develop and establish other approaches to the stratigraphic division and correlation of the Lower/Middle Cambrian on a global scale is a possible way to solve the puzzling problem. This work systematically studied acritarch fossils from the Early-Middle Cambrian Kaili Formation at Taijiang County, Guizhou Province. The Lower/Middle Cambrian boundary was divided in terms of acritarch fossil assemblage. The divided boundary is generally consistent with what was divided by trilobite and can be correlated with the Lower/Middle Cambrian boundaries divided by acritarch assemblage in Siberia and Europe. On this basis, the Lower/Middle Cambrian boundary is divided in terms of an obvious carbon isotopic excursion on a global scale during the transitional period from Early Cambrian to Middle Cambrian boundaries in Siberia and North America. The method for the stratigraphic division and correlation of the Lower/Middle Cambrian boundary in terms of carbon isotopic oscillations is helpful to solving the global problem on the division and correlation of the Lower/Middle Cambrian boundary. It is also evidenced that the extinction of a lot of trilobites at the end of Early Cambrian is closely related with this event of carbon isotopic excursion.

  16. Lower Cambrian Black Rock Series and Associated Stratiform Deposits in Southern China

    Institute of Scientific and Technical Information of China (English)

    陈南生; 范德廉; 等

    1990-01-01

    Widespread in more than ten provinces of southern China are the Lower Cambrian black argillaceous-arenaceous rock series consisting of black carbonaceous shales,black carbonaceousargillo-siliceous rocks,black carbonaceous silicolite and black silicolite and black carbonaceous argillaceous siltstone.The Ni,Mo,V,Cu,U,Ba,Ag,P contents of these series are usually several to tens of times higher than their average values in shales.As viewed from lithological sequence,element association and evolution,these black series can be diveided into two types.There occur a variety of deposits in the black rock series,such as phosphorite deposits,Ni-Mo-V polymetal deposits and "Stone coal" seams.According to ore composition,texture and structure,the phosphorite deposits fall into three types,i.e.,thick-bedded,lenticular and nodular,The Ni-Mo-V polymetal deposits,V deposits and reworked sedimentary CU-U-Cd polymetal deposits in terms of their element assiciation and ore genesis.As for the stratiform deposits in the black rock series,three mineralization stages have been recognized,i.e.,the formation of phosphorite deposits,of Ni-Mo polymetal deposits and of V-Cu-U-Cd polymetal deposits as well as of ":stone coal" seams.Evidence strongly suggests that lower organisms have played an important role in mineralization. Our studies indicate that the Lower Cambrian black argillaceous-arenaceous rock series in southern China and their associated stratiform deposits occur generally in the basal parts of a big sedimentary cycle,i.e.,the initial period of a transgression,or in the fine detrital-siliceous formation between two carbonate formatons,formed in a humid climatic zone between two arid ones.As for the environment of deposition,it is suggested that the Lower Cambrian black argillaceous-arenaceous rock series and associated stratiform deposits(excluding thick-bedded phosphorite deposits)were formed mainly in a restricted and poorly-fed sea basin of stagnant shallow water containing

  17. A highly redox-heterogeneous ocean in South China during the early Cambrian (˜529-514 Ma): Implications for biota-environment co-evolution

    Science.gov (United States)

    Jin, Chengsheng; Li, Chao; Algeo, Thomas J.; Planavsky, Noah J.; Cui, Hao; Yang, Xinglian; Zhao, Yuanlong; Zhang, Xingliang; Xie, Shucheng

    2016-05-01

    The "Cambrian Explosion" is known for rapid increases in the morphological disparity and taxonomic diversity of metazoans. It has been widely proposed that this biological event was a consequence of oxygenation of the global ocean, but this hypothesis is still under debate. Here, we present high-resolution Fe-S-C-Al-trace element geochemical records from the Jinsha (outer shelf) and Weng'an (outer shelf) sections of the early Cambrian Yangtze Platform, integrating these results with previously published data from six correlative sections representing a range of water depths (Xiaotan, Shatan, Dingtai, Yangjiaping, Songtao, and Longbizui). The integrated iron chemistry and redox-sensitive trace element data suggest that euxinic mid-depth waters dynamically coexisted with oxic surface waters and ferruginous deep waters during the earliest Cambrian, but that stepwise expansion of oxic waters commenced during Cambrian Stage 3 (∼ 521- 514 Ma). Combined with data from lower Cambrian sections elsewhere, including Oman, Iran and Canada, we infer that the global ocean exhibited a high degree of redox heterogeneity during the early Cambrian, consistent with low atmospheric oxygen levels (∼ 10- 40% of present atmospheric level, or PAL). A large spatial gradient in pyrite sulfur isotopic compositions (δ34Spy), which vary from a mean of - 12.0 ‰ in nearshore areas to + 22.5 ‰ in distal deepwater sections in lower Cambrian marine units of South China imply low concentrations and spatial heterogeneity of seawater sulfate, which is consistent with a limited oceanic sulfate reservoir globally. By comparing our reconstructed redox chemistry with fossil records from the lower Cambrian of South China, we infer that a stepwise oxygenation of shelf and slope environments occurred concurrently with a gradual increase in ecosystem complexity. However, deep waters remained anoxic and ferruginous even as macrozooplankton and suspension-feeding mesozooplankton appeared during

  18. 40Ar/39Ar dating of exceptional concentration of metals by weathering of Precambrian rocks at the Precambrian–Cambrian boundary

    DEFF Research Database (Denmark)

    Parnell, John; Mark, Darren F.; Frei, Robert;

    2014-01-01

    with mobilization on land of redox sensitive metals by oxidative terrestrial weathering. This unprecedented flushing of metals from the weathered Precambrian surface would have contributed to the chemistry of the earliest Cambrian ocean at a time of marked faunal evolution.......The sub-Cambrian surface, including diverse metalliferous deposits, shows evidence of intense weathering of Precambrian rocks to form supergene-enriched ores and metalliferous placers, followed by widespread peneplanation. Much of the metal would have been flushed to the Cambrian ocean during...

  19. The Cambrian "explosion" of metazoans and molecular biology: would Darwin be satisfied?

    Science.gov (United States)

    Conway-Morris, Simon

    2003-01-01

    The origins of metazoan bodyplans and the extent to which they are coincident with the Cambrian "explosion" are both areas of continuing debate. The fossil record has a unique advantage in terms of historical perspective, but remains highly contentious on account of the often controversial interpretations of particular groups (e.g. halkieriids, vetulicolians) and the heavy reliance on "windows" of exceptional preservation (e.g. Chengjiang, Burgess Shale). Molecular and developmental biology offer other unique insights, but may be problematic in terms of conflicting phylogenetic signals and questions revolving around gene co-option, evolution of developmental systems and even convergence. Such topics, far from frustrating the enterprise, actually widen our understanding of the nature of the evolutionary process with the exciting promise of the discovery of more general principles.

  20. A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale.

    Science.gov (United States)

    Caron, Jean-Bernard; Scheltema, Amélie; Schander, Christoffer; Rudkin, David

    2006-07-13

    Odontogriphus omalus was originally described as a problematic non-biomineralized lophophorate organism. Here we re-interpret Odontogriphus based on 189 new specimens including numerous exceptionally well preserved individuals from the Burgess Shale collections of the Royal Ontario Museum. This additional material provides compelling evidence that the feeding apparatus in Odontogriphus is a radula of molluscan architecture comprising two primary bipartite tooth rows attached to a radular membrane and showing replacement by posterior addition. Further characters supporting molluscan affinity include a broad foot bordered by numerous ctenidia located in a mantle groove and a stiffened cuticular dorsum. Odontogriphus has a radula similar to Wiwaxia corrugata but lacks a scleritome. We interpret these animals to be members of an early stem-group mollusc lineage that probably originated in the Neoproterozoic Ediacaran Period, providing support for the retention of a biomat-based grazing community from the late Precambrian Period until at least the Middle Cambrian.

  1. Why did life develop on the surface of the Earth in the Cambrian?

    Directory of Open Access Journals (Sweden)

    Carlo Doglioni

    2016-11-01

    Full Text Available Life was limited for most of Earth's history, remaining at a primitive stage and mostly marine until about 0.55 Ga. In the Paleozoic, life eventually exploded and colonized the continental realm. Why had there been such a long period of delayed evolution of life? Early life was dominated by Archaea and Bacteria, which can survive ionizing radiation better than other organisms. The magnetic field preserves the atmosphere, which is the main shield of UV radiation. We explore the hypothesis that the Cambrian explosion of life could have been enabled by the increase of the magnetic field dipole intensity due to the solidification of the inner core, caused by the cooling of the Earth, and the concomitant decrease with time of the high-energy solar flux since the birth of the solar system. Therefore, the two phenomena could be responsible for the growth and thickening of the atmosphere and the development of land surface life.

  2. Why did life develop on the surface of the Earth in the Cambrian?

    Institute of Scientific and Technical Information of China (English)

    Carlo Doglioni; Johannes Pignatti; Max Coleman

    2016-01-01

    Life was limited for most of Earth’s history, remaining at a primitive stage and mostly marine until about 0.55 Ga. In the Paleozoic, life eventually exploded and colonized the continental realm. Why had there been such a long period of delayed evolution of life? Early life was dominated by Archaea and Bacteria, which can survive ionizing radiation better than other organisms. The magnetic field preserves the at-mosphere, which is the main shield of UV radiation. We explore the hypothesis that the Cambrian ex-plosion of life could have been enabled by the increase of the magnetic field dipole intensity due to the solidification of the inner core, caused by the cooling of the Earth, and the concomitant decrease with time of the high-energy solar flux since the birth of the solar system. Therefore, the two phenomena could be responsible for the growth and thickening of the atmosphere and the development of land surface life.

  3. Cephalic and appendage morphology of the Cambrian arthropod Sidneyia inexpectans Walcott, 1911

    DEFF Research Database (Denmark)

    Stein, Martin

    2013-01-01

    as an evidence for variability of head segment counts in Cambrian arthropods, and to falsify the hypothesis of a head with three postantennular segments in the euarthropod ground pattern. Restudy of a substantial amount of material of S. inexpectans shows that previous interpretations of a short head were based...... understood, but the exopod seemed to differ from that of other artiopodans, except for the shared presence of lamellae. The head was considered to comprise only the ocular and antennular segments, these being covered entirely on the ventral side by a large doublure. This short head was often taken...... postantennular appendage bearing segments. The appendage morphology is shown to be consistent with artiopodan affinities. The exopod is of the bilobate flap-like type with lamellae inserting on the proximal portion, earlier proposed as a potential autapomorphy of Artiopoda. Reinforcement of artiopodan affinities...

  4. Dolomitization of Carbonate Periplatform Deposit,Machari Formation (Middle to Late Cambrian),Korea

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The petrography, the geochemistry and the burial history all constrain the origin and modification history of dolomites in an ancient periplatform carbonate slope deposit,the Machari Formation (late Miclclle to early Late Cambrian),Korea. The formation is mainly composed of rhythmic bedding. laminated to bedded lime mudstone alternating with argillaceous lime mudstone. The rhythmic bedding is a product of the deposition of offshore periplatform ooze and hemipelagic clay on a periplatform slope. This formation also shows minor and intermittent influx of other lithofacies including the bioclastic-peloidal packstone, peloidal wackestone, and intraclasts deposited as turbidites. Five types of dolomite occur in the Machari Formation, whose occurrence.texture and geochemistry provide an insight into origin and modification history.

  5. Histological observation of some primitive euconodonts of Late Cambrian from Liaoning

    Institute of Scientific and Technical Information of China (English)

    GUO Wei; DONG Xiping; ZENG Xiaochun; ZHAO Le

    2005-01-01

    The histology of some euconodonts of Late Cambrian from Benxi and Fuxian County, Liaoning Province is studied by the oil-immersion technique. The histological characteristics of six primitive species of euconodonts - Proconodontus muelleri, Proconodontus tenuiserratus, Granatodontus ani, Rotundoconus tricarinatus, Teridontus nakamurai and Cordylodus proavus are describedin detail. Tubular dentine and atubular (parallel- and wavy-lamellar) dentine are found in the basal bodies of the primitive euconodonts Proconodontus tenuiserratus and Proconodontus muelleri, respectively. The tubular dentine and spherulitic dentine are also recognized from the basal bodies of Granatodontus ani and Rotundoconus tricarinatus. Since the histological characteristics of the studied six species of euconodonts belonging to Proconodontus lineage and Teridontus lineage Sensu Miller (Univ Kansas Paleontol Contr, 1980, 99: 1-39)seems to be almost the same, euconodonts are proposed as possibly monophyletic herein.

  6. The anatomy, taphonomy, taxonomy and systematic affinity of Markuelia: Early Cambrian to Early Ordovician scalidophorans

    Science.gov (United States)

    Dong, X.-P.; Bengtson, S.; Gostling, N.J.; Cunningham, J.A.; Harvey, T.H.P.; Kouchinsky, A.; Val'Kov, A.K.; Repetski, J.E.; Stampanoni, M.; Marone, F.; Donoghue, P.C.J.

    2010-01-01

    Markuelia is a vermiform, annulated introvertan animal known as embryonic fossils from the Lower Cambrian to Lower Ordovician. Analysis of an expanded and revised dataset for Introverta shows that the precise position of Markuelia within this clade is dependent on the taxa included. As a result, Markuelia is assigned to the scalidophoran total group to reflect uncertainty as to whether it is a stem-scalidophoran or a stem-priapulid. The taxonomy of the genus is revised to provide an improved taxonomic framework for material assigned to Markuelia. Five species are recognized: M. secunda Val'kov, M. hunanensis Dong and Donoghue, M. lauriei Haug et al., M. spinulifera sp. nov. and M. waloszeki sp. nov. Finally, the preservation of Markuelia is evaluated in the light of both the taphonomy of the fossil embryos themselves and the experimental taphonomy of the priapulid Priapulus caudatus, which has been proposed as both a close relative and an anatomical analogue of Markuelia. ?? The Palaeontological Association.

  7. A new stalked filter-feeder from the middle Cambrian Burgess Shale, British Columbia, Canada.

    Science.gov (United States)

    O'Brien, Lorna J; Caron, Jean-Bernard

    2012-01-01

    Burgess Shale-type deposits provide invaluable insights into the early evolution of body plans and the ecological structure of Cambrian communities, but a number of species, continue to defy phylogenetic interpretations. Here we extend this list to include a new soft-bodied animal, Siphusauctum gregarium n. gen. and n. sp., from the Tulip Beds (Campsite Cliff Shale Member, Burgess Shale Formation) of Mount Stephen (Yoho National Park, British Columbia). With 1,133 specimens collected, S. gregarium is clearly the most abundant animal from this locality.This stalked animal (reaching at least 20 cm in length), has a large ovoid calyx connected to a narrow bilayered stem and a small flattened or bulb-like holdfast. The calyx is enclosed by a flexible sheath with six small openings at the base, and a central terminal anus near the top encircled by indistinct openings. A prominent organ, represented by six radially symmetrical segments with comb-like elements, surrounds an internal body cavity with a large stomach, conical median gut and straight intestine. Siphusauctum gregarium was probably an active filter-feeder, with water passing through the calyx openings, capturing food particles with its comb-like elements. It often occurs in large assemblages on single bedding planes suggesting a gregarious lifestyle, with the animal living in high tier clusters. These were probably buried en masse more or less in-situ by rapid mud flow events.Siphusauctum gregarium resembles Dinomischus, another Cambrian enigmatic stalked animal. Principal points of comparison include a long stem with a calyx containing a visceral mass and bract-like elements, and a similar lifestyle albeit occupying different tiering levels. The presence in both animals of a digestive tract with a potential stomach and anus suggest a grade of organization within bilaterians, but relationships with extant phyla are not straightforward. Thus, the broader affinities of S. gregarium remain largely unconstrained.

  8. Phylogeny and life habits of Early Arthropods-Predation in the Early Cambrian Sea

    Institute of Scientific and Technical Information of China (English)

    Andreas MAAS; Dieter WALOSZEK; CHEN Junyuan; Andreas BRAUN; WANG Xiuqiang; HUANG Diying

    2004-01-01

    We investigated two new arthropods from the Maotianshan-Shale fauna of southern China in the course of our research on life strategies, particularly predation, in Early Cambrian marine macrofaunal biota. One form clearly belongs to the so-called "great-appendage" arthropods, animals that were, most likely, active predators catching prey with their first pair of large, specialized frontoventral appendages. Based on this, we hypothesize that the new species and many others, if not all, of the "great-appendage" arthropods were derivatives of the chelicerate stem lineage and not forms having branched off at different nodes along the evolutionary lineage of the Arthropoda. Rather, we consider the "great-appendage" arthropods as belonging to a monophyletic clade, which modified autapomorphically their first pair of appendages (antennae in general arthropod terminology) into raptorial organs for food capture. The second new form resembles another Maotianshan-Shale arthropod, Fuxianhuia protensa, in sharing a head made of only two separate segments, a small segment bearing oval eyes laterally, and another bearing a large tergite, which forms a wide shield freely overhanging the subsequent narrow trunk segments. This segment bears a single pair of rather short anteriorly directed uniramous appendages, considered as the "still" limb-shaped antennae. Particularly the evolutionary status of head and limbs of these two forms suggests that both are representatives of the early part of the stem lineage toward the crown-group of Arthropoda, the Euarthropoda. These forms appear rather unspecialized, but may have been but simple predators. This adds to our hypothesis that predation was a common, if not dominant feeding strategy in the Cambrian, at least for arthropods.

  9. A new stalked filter-feeder from the middle Cambrian Burgess Shale, British Columbia, Canada.

    Directory of Open Access Journals (Sweden)

    Lorna J O'Brien

    Full Text Available Burgess Shale-type deposits provide invaluable insights into the early evolution of body plans and the ecological structure of Cambrian communities, but a number of species, continue to defy phylogenetic interpretations. Here we extend this list to include a new soft-bodied animal, Siphusauctum gregarium n. gen. and n. sp., from the Tulip Beds (Campsite Cliff Shale Member, Burgess Shale Formation of Mount Stephen (Yoho National Park, British Columbia. With 1,133 specimens collected, S. gregarium is clearly the most abundant animal from this locality.This stalked animal (reaching at least 20 cm in length, has a large ovoid calyx connected to a narrow bilayered stem and a small flattened or bulb-like holdfast. The calyx is enclosed by a flexible sheath with six small openings at the base, and a central terminal anus near the top encircled by indistinct openings. A prominent organ, represented by six radially symmetrical segments with comb-like elements, surrounds an internal body cavity with a large stomach, conical median gut and straight intestine. Siphusauctum gregarium was probably an active filter-feeder, with water passing through the calyx openings, capturing food particles with its comb-like elements. It often occurs in large assemblages on single bedding planes suggesting a gregarious lifestyle, with the animal living in high tier clusters. These were probably buried en masse more or less in-situ by rapid mud flow events.Siphusauctum gregarium resembles Dinomischus, another Cambrian enigmatic stalked animal. Principal points of comparison include a long stem with a calyx containing a visceral mass and bract-like elements, and a similar lifestyle albeit occupying different tiering levels. The presence in both animals of a digestive tract with a potential stomach and anus suggest a grade of organization within bilaterians, but relationships with extant phyla are not straightforward. Thus, the broader affinities of S. gregarium remain

  10. Geodatabase of the datasets used to represent the four aquifer subunits of the Cambrian-Ordovician aquifer system, Illinois, Iowa, Michigan, Minnesota, and Wisconsin

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This geodatabase includes spatial datasets that represent the Cambrian-Ordovician aquifer system in the States of Wisconsin, Michigan, Minnesota, Iowa, and Illinois....

  11. Microthermometric measurement of fluid inclusions and its constraints on genesis of PGE-polymetallic deposits in Lower Cambrian black rock series, southern China

    Institute of Scientific and Technical Information of China (English)

    WANG Min; SUN Xiaoming; MA Mingyang

    2005-01-01

    Systematic microthermometric measurements of fluid inclusions in the PGE-polymetallic deposits hosted in the Lower Cambrian black rock series in southern China were performed, and the results suggest: (1) there exist two types of fluid inclusions. TypeⅠis of NaCl-H2O system with low-medium salinity, and its homogenization temperatures (Th) and salinities are 106.9- 286.4℃ and ( 0.8- 21.8) wt%NaCl eq. respectively; TypeⅡ is of CaCl2-NaCl-H2O system with medium-high salinities, and its homogenization temperatures and salinities range from 120.1℃ to 269.6℃ and ( 11.4- 31.4) wt%NaCl eq., respectively. The typeⅡ fluid inclusions have been discovered for the first time in this kind of deposits; (2) two generations of ore-forming fluids were recognized. Characteristics of fluid inclusions in the PGE-polymetallic ores and carbonate-quartz stockworks in the underlying phosphorites are almost of no difference, they may represent ore-forming fluids at the main metallogenic stage. The peak value of homogenization temperature of those fluid inclusions is about 170℃, while their salinities possess a remarkable bimodal distribution pattern with two peak values of (27-31) wt%NaCl eq. and (4-6) wt%NaCl eq. On the contrary, fluid inclusions in the carbonate-quartz veins in the hanging wall may represent ore-forming fluids at the post-metallogenetic stage. The homogenization temperatures and the peak values of salinities are mostly 130-170℃ and (12-14) wt%NaCl eq., respectively; (3) nobel gas isotopic composition analyses in combination with the microthermometric measurements of fluid inclusions suggest that the ore-forming fluids at the main metallogenetic stage were probably derived from mixing of basinal hot brines with the CaCl2-NaCl-H2O system and seawater with the NaCl-H2O system; (4) in the Early Cambrian, the basinal hot brines were trapped in the Caledonian basins, which were distributed along the southern margin of the Yangtze Craton, and where giant thick

  12. A New Arthropod, Guangweicaris Luo, Fu et Hu gen. nov.from the Early Cambrian Guanshan Fauna, Kunming, China

    Institute of Scientific and Technical Information of China (English)

    LUO Huilin; FU Xiaoping; HU Shixue; LI Yong; HOU Shuguang; YOU Ting; PANG Jiyuan; LIU Qi

    2007-01-01

    The Guanshan Fauna is a soft-bodied fauna dominated by arthropods (including trilobites,trilobitoides, Tuzoia, Isoxys, and bradorids) in association with priapulids, brachiopods,anomalocaridids, vetulicoliids, sponges, chancellorids, and echinoderms. This paper reports and describes a new arthropod from the yellowish green mudstone at the lower part of the Wulongqing Formation, Canglangpuan Stage, Lower Cambrian in Kunming, Yunnan, China. The stratigraphic and geographic distribution, classification, fossil preservation, life style of this new arthropod and comparisons with other fossil arthropods are also discussed in details. The discovery and research of the non-mineralized arthropod, Guangweicaris Luo, Fu et Hu gen. nov. from the Guanshan Fauna adds new members to the taxonomic list and provides new information to the evolution of early arthropods.Furthermore, this study would shed new light into the "Cambrian Explosion" and the evolution of early life.

  13. Cambrian Ichnofossils from the Zhoujieshan Formation (Quanji Group) Overlying Tillites in the Northern Margin of the Qaidam Basin, NW China

    Institute of Scientific and Technical Information of China (English)

    Yue Wang; Xunlian Wang; Ye Wang

    2015-01-01

    The Quanji Group is composed of siliciclastics and carbonates and was deposited on a relatively stable block, in the northern margin of the Qaidam Basin, NW China. It is one of the research hotspots in the Qilian-Qinling-Kunlun tectonic zones. However, it has long been argued whether the up-per Quanji Group should be assigned to the Precambrian or the Cambrian for lack of convincing fossil evidence. The discovery of ichnofossils, including Rusophycus, Cruziana, Dimorphichnus, Treptichnus, Skolithos, Arenicolites, Palaeophycus, and Helminthopsis, indicates that the upper member of the Zhou-jieshan Formation (top Quanji Group) is Cambrian in age, and at least above the Treptichnus (Phycodes) pedum Biozone, the lowermost biozone in the Cambrian. The lower member of the Zhoujieshan Forma-tion should belong to the Cambrian. During the time when the upper member of the Zhoujieshan For-mation was deposited, the northern margin of the Qaidam Basin was dominated by the Cruziana Ichno-facies, characterizing a lower-energy shelf (shallow) sea environment with moderate-rich oxygen con-tents. In addition, the conglomerates in the Hongtiegou Formation of the Quanji Group underlying the Zhoujieshan Formation were generally regarded as tillites. However, the dolostones of the lower member of the Zhoujieshan Formation are, in lithology and geochemistry, different from the typical cap-dolostones of the Doushantuo Formation in South China, so it is necessary to further study the ori-gins of the lower member of the Zhoujieshan Formation and the conglomerates of the Hongtiegou For-mation.

  14. 再论鄂尔多斯盆地寒武纪岩相古地理及沉积构造演化%Further Study on Lithofacies Palaeogeography and Sedimentary-Tectonic Evolution of Cambrian in Ordos Basin,North China

    Institute of Scientific and Technical Information of China (English)

    陈启林; 白云来; 马玉虎; 刘晓光

    2013-01-01

    It is now a hot spot to prospect oil and gas in deep of Ordos basin,North China.Seven new lithofacies palaeogeography maps on Ordos have been sketched out,according to the guideline of which tectonism controls sedimentation,applying the sequence stratigraphy theory,on the ground of field outcrops observations,core observations,logging data and seismic profiles,applying the method of single factor analysis and comprehensive mapping,and taking tectonic-sediment evolution as storyline, and reservoir-accumulation as the goal.The research has shown that there was a dynamic evolution process in Cambrian in Ordos,in which carbonate ramps formed platforms and restricted platforms.The carbonate ramps were characterized by exchanging of clear water and muddy water.The research also shows that drought in early became relative humidity in late.There was a tectonic differentiation in south-north earlier and west-east later.Southern Ordos margin appeared aulacogen.Ancient Ordos Land (AOL)was,fundamentally,covered by seawater except the parts of north and west margin in the Middle-Late Cambrian.A conversion in which land was changed to sea had been completed.The characteristic of palaeogeography was mainly a shallow-water carbonate platform on the continental sea. The forming of “Ancient Ordos Sea”(AOS)was a turning point.The west arises in Late Cambrian, which is a rudiment of “Central Paleouplift”(CP)which mainly had formed in Ordovician.The Late Cambrian uplift ran in north to south and is basically the same range as “Ordovician Central Paleouplift”.Therefore,it has been proved that the earliest age of forming “Central Ordos Paleouplift”is from Cambrian Furongian to the Early Ordovician.It has also been proved that tidal flat is dominating facies in the Early Cambrian,oliticbeachs are distributed around the land in Zhangxia Formation in the Middle Cambrian and porous dolostones which distributed in whole areas mainly occur in the top of Cambrian

  15. Secondary Phosphatization of the Earliest Cambrian Small Shelly Fossil Anabarites from Southern Shaanxi

    Institute of Scientific and Technical Information of China (English)

    Yali Chen; Xuelei Chu; Xingliang Zhang; Mingguo Zhai

    2016-01-01

    Biomineralization may have an extremely long evolutionary history since the Paleoarchean, while the widespread biomineralization among metazoan lineages started at the earliest Cambrian. However, the primary mineralogy of Anabarites shell remains controversial. Optical microscopic observations combined with the Back-Scattered Electron (BSE) and Energy-Dispersive X-ray Spectroscopy (EDS) analyses are used to study the shell of the fossil Anabarites from the Kuanchuanpu fauna in southern Shaanxi Province in China, which is correlated to the Cambrian Fortunian Stage. The EDS analysis shows that the phosphorus-rich layer closely adjacent to the calcified layer exhibits a Ca: P: C ratio compositionally similar to the mineral fluorapatite (Ca5(PO4,CO3)3(F,CO3). The result that the calcified layer and the phosphorus-rich layer have different chemical compositions is consistent with the optical observation that there is an obvious gap between these two layers and the phosphorus-rich layer can extend to the phosphatic material inside of the tube, suggesting the phosphorus-rich layer doesn’t belong to the original shell. We suggest that the phosphorous-rich layer is diagenetic in origin, precipitated as a result of phosphorus release during the decay of organic matter by microbes. Considering the outermost shell layer (OMS, biologically controlled carbonate shell layer) should display different isotopic information from the carbonate matrix (i.e., OMS is 12C concentrated due to the biogenic organic matter template is readily rich in 12C), NanoSIMS was used to map ion distributions of C and N in the shell of Anabarites and matrix. However, ion images show that the concentration differences of 12C, 13C and 26CN among the OMS and the matrix are unclear, while 12C and 26CN are supposed to be enriched in the OMS. Therefore, the minor isotopic differences between the shell and the matrix is hard to be detected by NanoSIMS, at least in our sample, probably due to alteration of

  16. New stylophorans (Echinodermata) from the Upper Cambrian of Guangxi, South China

    Institute of Scientific and Technical Information of China (English)

    HAN NaiRen; CHEN GuiYing

    2008-01-01

    This paper describes for the first time the cornute stylophorans (Echinodermata) in China. The new material came from the Guole Formation of the Furongian (Late Cambrian) in the Guole area of Jingxi,Guangxi Province, South China. These new cornute specimens are preserved in situ and found along with well-preserved trilobites and brachiopods. One new species, Phyllocystis jingxiensis sp. nov., is proposed to accommodate these unusual materials. The new species is defined by the small,heart-shaped theca with the frame composed of ten narrow, smooth and thick marginal plates, three adoral plates and distinctive zygal and aulacophore. Both supracentrals and infracentrals are polygonal-outlined. The marginal plate M/ on the inferior face extends posteriorly to form zygal that possesses a broadened proximal end and the proximal portion joining with the conjunction between M4 and M5 on the inferior face. Aulacophore comprises ten segments at its proximal part and is conical at the middle part (named stylocone). Its distal portion is rather long and bears conspicuous ambulacrum grooves. Tectals are horizontally arranged on superior face and obliquely arranged on inferior face.Both cothurnopore and anal pyramid are vaguely seen on the right anterior corner and the extremity of theca's superior face.

  17. New stylophorans(Echinodermata) from the Upper Cambrian of Guangxi,South China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This paper describes for the first time the cornute stylophorans (Echinodermata) in China. The new material came from the Guole Formation of the Furongian (Late Cambrian) in the Guole area of Jingxi, Guangxi Province, South China. These new cornute specimens are preserved in situ and found along with well-preserved trilobites and brachiopods. One new species, Phyllocystis jingxiensis sp. nov., is proposed to accommodate these unusual materials. The new species is defined by the small, heart-shaped theca with the frame composed of ten narrow, smooth and thick marginal plates, three adoral plates and distinctive zygal and aulacophore. Both supracentrals and infracentrals are polygonal-outlined. The marginal plate M1’ on the inferior face extends posteriorly to form zygal that possesses a broadened proximal end and the proximal portion joining with the conjunction between M4 and M5 on the inferior face. Aulacophore comprises ten segments at its proximal part and is conical at the middle part (named stylocone). Its distal portion is rather long and bears conspicuous ambulacrum grooves. Tectals are horizontally arranged on superior face and obliquely arranged on inferior face. Both cothurnopore and anal pyramid are vaguely seen on the right anterior corner and the extremity of theca’s superior face.

  18. Cambrian Burgess Shale-type deposits share a common mode of fossilization

    Science.gov (United States)

    Gaines, Robert R.; Briggs, Derek E. G.; Yuanlong, Zhao

    2008-10-01

    Although Cambrian Burgess Shale-type (BST) biotas arefundamental to understanding the radiation of metazoans, thenature of their extraordinary preservation remains controversial.There remains disagreement about the importance of the roleof early mineral replication of soft tissues versus the conservationof primary organic remains. Most prior work focused on soft-bodiedfossils from the two most important BST biotas, those of theBurgess Shale (Canada) and Maotianshan Shale (Chengjiang, China).Fossils from these two deposits do not provide ideal candidatesfor specimen-level taphonomic study because they have been altered:the Burgess Shale by greenschist facies metamorphism and theMaotianshan Shale by intensive subsurface weathering. Elementalmapping of soft-bodied fossils from 11 other BST deposits worldwidedemonstrates that BST preservation represents a single majortaphonomic pathway that may share a common cause wherever itoccurs. The conservation of organic tissues, and not early authigenicmineralization, is the primary mechanism responsible for thepreservation of BST assemblages. Early authigenic mineral replacementpreserves certain anatomical features of some specimens, butthe preservation of non-biomineralized BST fossils requiressuppression of the processes that normally lead to the degradationof organic remains in marine environments.

  19. Experimental taphonomy and the anatomy and diversity of the earliest fossil vertebrates (Chengjiang Biota, Cambrian, China)

    Science.gov (United States)

    Purnell, Mark; Gabbott, Sarah; Murdock, Duncan; Cong, Peiyun

    2016-04-01

    The oldest fossil vertebrates are from the Lower Cambrian Chengjiang biota of China, which contains four genera of fish-like, primitive vertebrates: Haikouichthys, Myllokunmingia, Zhongjianichthys and Zhongxiniscus. These fossils play key roles in calibrating molecular clocks and informing our view of the anatomy of animals close to the origin of vertebrates, potentially including transitional forms between vertebrates and their nearest relatives. Despite the evident importance of these fossils, the degree to which taphonomic processes have affected their anatomical completeness has not been investigated. For example, some or all might have been affected by stemward slippage - the pattern observed in experimental decay of non-biomineralised chordates in which preferential decay of synapomorphies and retention of plesiomorphic characters would cause fossil taxa to erroneously occupy more basal positions than they should. This hypothesis is based on experimental data derived from decay of non-biomineralised chordates under laboratory conditions. We have expanded this analysis to include a broader range of potentially significant environmental variables; we have also compared and combined the results of experiments from several taxa to identify general patterns of chordate decay. Examination of the Chengjiang vertebrates in the light of these results demonstrates that, contrary to some assertions, experimentally derived models of phylogenetic bias are applicable to fossils. Anatomical and phylogenetic interpretations of early vertebrates that do not take taphonomic biases into account risk overestimating diversity and the evolutionary significance of differences between fossil specimens.

  20. Phylogeny and evolutionary significance of vermiform animals from the Early Cambrian Chengjiang Lagersttte

    Institute of Scientific and Technical Information of China (English)

    David; BAINES

    2010-01-01

    The Early Cambrian Chengjiang Biota of China has preserved many species of vermiform animals in exquisite detail,which provide a unique window into the origin and early evolution of different vermiform phyla.This article reviews and discusses the forty-five Chengjiang vermiform animals discovered so far,and specifically comments on the phylogeny,modes of life,evolutionary significance as well as existing debates concerning the Chengjiang priapulid and lobopodian phyla.This article analyzes existing problems with Chengjiang vermiform morphological research and highlights various factors that affect the final preserved fossil morphology,including taphonomy and shape change caused by vermiform movement,as well as proposing that Anningvermis multispinosa and Corynetis brevis are synonymous.Chengjiang vermiform animals displayed a great diversity of morphologies and ecological roles,which is significant for understanding the origin and evolution of early metazoans;the potential for future research is enormous but needs to be broadened by interdisciplinary work involving taphonomy,geochemistry,cladistics,and genetics.

  1. Preservation and phylogeny of Cambrian ecdysozoans tested by experimental decay of Priapulus

    Science.gov (United States)

    Sansom, Robert S.

    2016-09-01

    The exceptionally preserved Cambrian fossil record provides unique insight into the early evolutionary history of animals. Understanding of the mechanisms of exceptional soft tissue preservation frames all interpretations of the fauna and its evolutionary significance. This is especially true for recent interpretations of preserved nervous tissues in fossil ecdysozoans. However, models of soft tissue preservation lack empirical support from actualistic studies. Here experimental decay of the priapulid Priapulus reveal consistent bias towards rapid loss of internal non-cuticular anatomy compared with recalcitrant cuticular anatomy. This is consistent with models of Burgess Shale-type preservation and indicates that internal tissues are unlikely to be preserved with fidelity if organically preserved. This pattern, along with extreme body margin distortion, is consistent with onychophoran decay, and is therefore resolved as general for early ecdysozoans. Application of these patterns to phylogenetic data finds scalidophoran taxa to be very sensitive to taphonomically informed character coding, but not panarthropodan taxa. Priapulid decay also have unexpected relevance for interpretation of myomeres in fossil chordates. The decay data presented serve not only as a test of models of preservation but also a framework with which to interpret ecdysozoan fossil anatomies, and the subsequent evolutionary inferences drawn from them.

  2. Geochemistry of the Cambrian Sirius Passet Lagerstätte, Northern Greenland

    Science.gov (United States)

    Boudec, Ange Le; Ineson, Jon; Rosing, Minik; Døssing, Lasse; Martineau, François; Lécuyer, Christophe; Albarède, Francis

    2014-04-01

    lower Cambrian Sirius Passet Lagerstätte (˜518 Ma) consists of mudstones about 8 m thick located in the Franklinian Basin of North Greenland. We analyzed major and trace elements plus the S, C, Cu, Fe, Zn, and Mo isotope compositions. Factor analysis allowed the lithology of the mudstone to be broken down into variable proportions of two inputs, a dry felsic component and a hydrous mafic component (smectite or chlorite). Zircons U-Pb ages indicate multiple sources, the local Proterozoic basement of Northern Greenland (1250-2400 Ma) and Pan-African felsic magmas (620-650 Ma) from across the Iapetus ocean. Diagenesis involved the reduction of Fe, S, and Mo from seawater and pyritization. The Sirius Passet Lagerstätte formed in oxygen-starved muds inhibiting degradation of organic matter underneath a well-ventilated water column. The chemistry of the samples, their very fine grain size, their apparent lack of graded bedding, and the age of zircons suggest that the Lagerstätte may represent wind-blown dust deposited on the continental slope.

  3. Early Cambrian eodiscoid trilobites of the Yangtze Platform and their stratigraphic implications

    Institute of Scientific and Technical Information of China (English)

    YANG Aihua; ZHU Maoyan; ZHANG Junming; LI Guoxiang

    2003-01-01

    Analysis of the taxonomy and stratigraphic distribution of the Early Cambrian eodiscoid trilobites of the Yangtze Platform indicates that species of Tsunyidiscus and Hupeidiscus can be used for biostratigraphic correlation. T. aclis occurs only in the lower Qiongzhusian, T. armatus occurs in the lower and middle Qiongzhusian, while T. niutitangensis and T. tingi occur mainly in the middle and upper Qiongzhusian, with only T. tingi extending upward into the lower Canglangpuian. H. orientalis first appears in the upper Qiongzhusian, reaching peak abundance in the lower Canglangpuian and becoming extinct above the Drepanuroides Zone. Biostratigraphic and lithostratigraphic correlations indicate that the limestone in the lower part of the Mingxinsi Formation, the Upper Member of Jiumenchong Formation, and the upper part of the Middle Member of the Huangbailing Formation, can be correlated with each other as Hupediscus, an index fossil of the lower Canglangpuian, is abundant in all these units. The lower part of the Niutitang and Jiumenchong formations in eastern Guizhou, which mainly represent Qiongzhusian strata, can be correlated with the Lower Member of the Huangbailing Formation. The basal part of the Niutitang Formation, which may be equivalent to the Upper Meishucunian Shiyantou Formation in eastern Yunnan, is very condensed. Well-preserved sponge faunas and non-mineralized fossils in the lower part of the Niutitang and Hetang formations are not older than Qiongzhusian in age.

  4. Cambrian Kherlen ophiolite in northeastern Mongolia and its tectonic implications: SHRIMP zircon dating and geochemical constraints

    Science.gov (United States)

    Miao, Laicheng; Baatar, Munkhtsengel; Zhang, Fochin; Anaad, Chimedtseren; Zhu, Mingshuai; Yang, Shunhu

    2016-09-01

    The Kherlen terrane, which contains the Kherlen ophiolitic complex, is located between two Precambrian continental blocks in the northeastern Mongolia. We present new geochemical and SHRIMP zircon U-Pb data for the Kherlen ophiolitic complex and for granitic plutons intruding the complex, providing constraints on the regional evolution in Early Paleozoic time. The Kherlen ophiolite, which is geochemically similar to SSZ-type ophiolites, was originated from two distinct mantle sources, a N-MORB-like source and an E-MORB-like source. A gabbro and a plagiogranite dike intruding the gabbro from the Kherlen ophiolite yielded similar SHRIMP zircon U-Pb ages of ca. 500 Ma, suggesting that the ophiolite formed in Late Cambrian time. Post- or syn-collisional granites intruding the ophiolitic complex yielded crystallization ages of ca. 440 Ma, which is interpreted to record the minimum age of the tectonic emplacement of the ophiolite. These new data demonstrate that the Kherlen ophiolite belt is an Early Paleozoic suture between the Ereendavaa and the Idermeg continental terranes, which is generally coeval with the Bayankhongor belt in central Mongolia, indicating that they are regionally correlated, and thus they define a major Early Paleozoic suture between two Precambrian continental blocks in the central-northeastern Mongolia.

  5. Cambrian cinctan echinoderms shed light on feeding in the ancestral deuterostome.

    Science.gov (United States)

    Rahman, Imran A; Zamora, Samuel; Falkingham, Peter L; Phillips, Jeremy C

    2015-11-07

    Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidating the early evolution of feeding in chordates and allied phyla; however, it is debated whether the ancestral deuterostome was a tentaculate feeder or a pharyngeal filter feeder. To address this, we evaluated the hydrodynamics of feeding in a group of fossil stem-group echinoderms (cinctans) using computational fluid dynamics. We simulated water flow past three-dimensional digital models of a Cambrian fossil cinctan in a range of possible life positions, adopting both passive tentacular feeding and active pharyngeal filter feeding. The results demonstrate that an orientation with the mouth facing downstream of the current was optimal for drag and lift reduction. Moreover, they show that there was almost no flow to the mouth and associated marginal groove under simulations of passive feeding, whereas considerable flow towards the animal was observed for active feeding, which would have enhanced the transport of suspended particles to the mouth. This strongly suggests that cinctans were active pharyngeal filter feeders, like modern enteropneust hemichordates and urochordates, indicating that the ancestral deuterostome employed a similar feeding strategy.

  6. Stable isotope (δ13Cker, δ13Ccarb, δ18Ocarb distribution along a Cambrian outcrop section in the eastern Tarim Basin, NW China and its geochemical significance

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    Hu Liu

    2017-01-01

    Full Text Available This study investigated the geochemical features of the lower Paleozoic strata of Yaerdang Mountain outcrop along with the core samples from well TD2∈ in the eastern Tarim Basin, NW China. The total organic carbon abundance, hydrocarbon-generating precursor biospecies, and stable isotope ratios of organics and carbonate (δ13Cker, δ13Ccarb and δ18Ocarb were comprehensively studied for their possible correlative constraints during sedimentary evolution. The results revealed that the δ13Cker (VPDB of Cambrian kerogens along the outcrop section varied from −34.6‰ to −28.4‰, indicating an increasing tendency from the lower Cambrian to the upper Cambrian. This was on the whole accompanied by the variation in the δ13Ccarb and δ18Ocarb along the profile, which might be associated with the changes in the sea level and also in the compositional variation of benthic and planktonic biomass. The large variation in the stable carbon isotope ratios up to 6‰ along the outcrop section reflected the heterogeneity of the Cambrian source rocks from the eastern Tarim Basin. Hence, the 13C-enriched crude oils from well TD2∈ might have been derived from a localized stratum of Cambrian source rocks. The results from this study showed the possibility of multiple source kitchens in the Cambrian–lower Ordovician portion of Tarim Basin.

  7. Stable isotope record of coexisting apatite and dolomite in Early Cambrian phosphorites, Meishucun section, South China

    Science.gov (United States)

    Wegwerth, Antje; Struck, Ulrich; Segl, Monika; Vennemann, Torsten W.; Gehlken, Peer-L.; Heubeck, Christoph; Böttcher, Michael E.

    2010-05-01

    The Precambrian-Cambrian transition forms one of the most dramatic time periods in Earth's history, as global changes in tectonics, climate and chemistry in the atmosphere and oceans favoured the worldwide Cambrian Radiation and a concomitant ecosphere revolution. This time interval is paralleled by the first appearance of the widespread giant phosphorites. The well-known Meishucun section (South China), a former candidate section for the Pc-C boundary, documents phosphorite genesis amongst a rapid biodiversification, immediately following the end of the Precambrian in a low-latitude, shallow-water carbonate shelf. This contribution aims to elucidate the relation between simultaneous phosphorite deposition and global environmental conditions at the Pc-C boundary by using stable carbon and oxygen isotope analyses. Accurate determinations of d13C and d18O values may allow conclusions about ancient ocean circulation, paleo-productivity, paleo-temperatures, and most prominently diagenetic processes. The investigated samples from the Meishucun section basically consist of apatite, dolomite, and quartz that may be further devided into a lower and upper phosphorite as well as an overlying dolostone intervall. Additionally, calcite and siderite occur as minor compounds in some samples. Bulk d13C values of the carbonate fraction correlate with dolomite abundance throughout the section ranging from -4 to 1 per mil. Furthermore, several horizons suggest a relation between d13C values and apatite content, implying lower d13C values in apatites compared to coexisting dolomite. A slight negative d13C excursion at the top of the lower phosphorite coincides with the first appearance of small shelly fossils. Corresponding bulk d18O values generally show a stratigraphic-upward trend towards lower values throughout the record with slightly higher values in dolomite-rich sections. This may either indicate a warming trend during deposition, an isotopic shift in sea water composition

  8. Population Structure, Life Strategies and Systematics of Phosphatocope Ostracods from the Middle Cambrian of Bornholm

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    I. Hinz-Schallreuter

    1998-01-01

    Full Text Available She Middle Cambrian Borregård Member of Bornholm which is the stratigraphical equivalent to the Baltoscandian Exsulans Limestone yielded a rich and comparatively diverse ostracod fauna in its upper part. It comprises eight species out of four genera. They belong to three known subfamilies that are redefined on the basis of special characters of the contact margin. An ontogenetic character unknown from typical ostracods is documented in several species: during early ontogeny the gestalt (l:h ratio develops constantly in becoming increasingly longer until the so-called ontogenetical turning point (OTP from which the direction of growth focusses on carapace height. This phenomenon may be explained by changes in body morphology. The Borregård association represents an ecologic community type differing from other yet recorded Middle Cambrian communities in the Baltoscandic region. Apart from Vestrogothia longispinosa which is a common faunal element in Baltoscandian ostracod faunas, the yet recorded species of Bidimorpha are unknown from other Baltoscandian occurrences. Vice versa, the known species of Bidimorpha described from Swedish occurrences have not been recognized in the rich Borregård community. Similarly, Falites insula and Hesslandona abdominalis may be of local significance, too, but the respective records from contemporaneous Swedish localities are insufficient in this respect, yet. Due to specific morphological adaptations, the four genera are assumed to represent different benthic life strategies. New taxa are: Bidimorpha arator n. sp., Bidimorpha labiator n. sp., Bidimorpha sexspinosa n. sp., Falites insula n. sp., Hesslandona abdominalis n. sp., Vestrogothia herrigi n. sp. and Vestrogothia minilaterospinata n. sp. Aus dem mittelkambrischen Borregård Member von Bornholm, einem zeitlichen Äquivalent des baltoskandischen Exsulanskalkes, wurde eine reiche und vergleichsweise diverse Ostrakodenfauna gewonnen. Sie umfaßt 8 Arten aus

  9. From Cycles to Sequences: Sequence Stratigraphy and Relative Sea Level Change for the Late Cambrian of the North China Platform

    Institute of Scientific and Technical Information of China (English)

    MEI Mingxiang; MA Yongsheng; DENG Jun; CHEN Huijun

    2005-01-01

    In the Late Cambrian, the North China Platform was a typical carbonate ramp platform. The Upper Cambrian of the northern part of the North China Platform is famous for the development of bioherm limestones and storm calcirudites and can be divided from bottom to top into the Gushan, Changshan and Fengshan formations. In this set of strata, the deep-ramp mudstone and marls and the shallow-ramp packstones and grainstones constitute many carbonate meter-scale cycles of subtidal type. More tidal-flat dolomites are developed in the Upper Cambrian of the southern margin of the North China platform, in which limestone and dolomite beds also constitute many carbonate meter-scale cycles of the peritidal type. These cycles are marked by a variety of litho-facies successions. There are regularly vertical stacking patterns of meter-scale cycles in long-term third-order sequences, which is the key to discerning such sequences. Thirdorder sequence is marked by a particular sedimentary-facies succession that is the result of the environment-changing process of deepening and shoaling, which is genetically related to third-order sea level changes. Furthermore, four thirdorder sequences can be grouped in the Upper Cambrian of the North China Platform. The main features of these four thirdorder sequences in the northern part of the platform can be summarized as follows: firstly, sequence-boundaries are characterized by drowning unconformities; secondly, the sedimentary-facies succession is generally constituted by one from deep-ramp facies to shallow-ramp facies; thirdly, a succession of "CS (?)+HST" (i.e., "condensed section and highstand system") forms these four third-order sequences. The chief features for the third-order sequences in the southern part of the North China Platform comprises: more dolomites are developed in the HSTs of third-order sequences and also developed more carbonate meter-scale cycles of peritidal types; the sedimentary-facies succession of the third

  10. Genesis mechanism of the Sinian-Cambrian reservoirs in the Anyue Gas Field, Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Zhou Jingao

    2015-03-01

    Full Text Available The Lower Cambrian Longwangmiao Fm, the 4th and 2nd members of the Sinian Dengying Fm are the three major gas layers in the Anyue Gas Field of the Sichuan Basin. Their main characteristics and genesis mechanism were investigated, and the following three findings were obtained. First, according to sedimentary microfacies, lithology and porosity, the Longwangmiao Fm is identified as fractured-vuggy dolomite reservoir of grain shoal facies, the 4th member of the Dengying Fm as fractured-vuggy (cavernous dolomite reservoir of cyanobacteria mound beach facies, and the 2nd member of the Dengying Fm as fractured-vuggy dolomite reservoirs of cyanobacteria mound beach facies. Second, the Longwangmiao Fm is mainly grain dolomite, with dissolution pores and vugs as major reservoir space, at an average porosity of 4.24% and an average thickness of 36 m. The 4th member of the Dengying Fm made up of cyanobacteria dolomite has dissolution pores, vugs and caverns as major reservoir space with an average porosity of 3.22% and an average thickness of 70 m. The 2nd member of the Dengying Fm composed of cyanobacteria dolomite has fractures and vugs as major reservoir space with an average porosity of 3.34% and an average thickness of 80 m. Third, those reservoirs experienced multiple evolutionary stages including porosity development, hydrothermal mineral filling, asphalt filling etc. Penecontemporaneous dissolution and supergene karstification are the key factors controlling the formation of the reservoir space and the evolution models of the reservoirs were figured out.

  11. The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago

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    Todd E Feinberg

    2013-10-01

    Full Text Available Vertebrates evolved in the Cambrian Period before 520 million years ago, but we do not know when or how consciousness arose in the history of the vertebrate brain. Here we propose multiple levels of isomorphic or somatotopic neural representations as an objective marker for sensory consciousness. All extant vertebrates have these, so we deduce that consciousness extends back to the group’s origin. The first conscious sense may have been vision. Then vision, coupled with additional sensory systems derived from ectodermal placodes and neural crest, transformed primitive reflexive systems into image forming brains that map and perceive the external world and the body’s interior. We posit that the minimum requirement for sensory consciousness and qualia is a brain including a forebrain (but not necessarily a developed cerebral cortex/pallium, midbrain and hindbrain. This brain must also have 1 hierarchical systems of intercommunicating, isomorphically organized, processing nuclei that extensively integrate the different senses into representations that emerge in upper levels of the neural hierarchy; and 2 a widespread reticular formation that integrates the sensory inputs and contributes to attention, awareness, and neural synchronization. We propose a two-step evolutionary history, in which the optic tectum was the original center of multi-sensory conscious perception (as in fish and amphibians: step 1, followed by a gradual shift of this center to the dorsal pallium or its cerebral cortex (in mammals, reptiles, birds: step 2. We address objections to the hypothesis and call for more studies of fish and amphibians. In our view, the lamprey has all the neural requisites and is likely the simplest extant vertebrate with sensory consciousness and qualia. Genes that pattern the proposed elements of consciousness (isomorphism, neural crest, placodes have been identified in all vertebrates. Thus, consciousness is in the genes, some of which are

  12. Depositional and diagenetic variability within the Cambrian Mount Simon Sandstone: Implications for carbon dioxide sequestration

    Science.gov (United States)

    Bowen, B.B.; Ochoa, R.I.; Wilkens, N.D.; Brophy, J.; Lovell, T.R.; Fischietto, N.; Medina, C.R.; Rupp, J.A.

    2011-01-01

    The Cambrian Mount Simon Sandstone is the major target reservoir for ongoing geologic carbon dioxide (CO2) sequestration demonstrations throughout the midwest United States. The potential CO2 reservoir capacity, reactivity, and ultimate fate of injected CO2 depend on textural and compositional properties determined by depositional and diagenetic histories that vary vertically and laterally across the formation. Effective and efficient prediction and use of the available pore space requires detailed knowledge of the depositional and diagenetic textures and mineralogy, how these variables control the petrophysical character of the reservoir, and how they vary spatially. Here, we summarize the reservoir characteristics of the Mount Simon Sandstone based on examination of geophysical logs, cores, cuttings, and analysis of more than 150 thin sections. These samples represent different parts of the formation and depth ranges of more than 9000 ft (>2743 m) across the Illinois Basin and surrounding areas. This work demonstrates that overall reservoir quality and, specifically, porosity do not exhibit a simple relationship with depth, but vary both laterally and with depth because of changes in the primary depositional facies, framework composition (i.e., feldspar concentration), and diverse diagenetic modifications. Diagenetic processes that have been significant in modifying the reservoir include formation of iron oxide grain coatings, chemical compaction, feldspar precipitation and dissolution, multiple generations of quartz overgrowth cementation, clay mineral precipitation, and iron oxide cementation. These variables provide important inputs for calculating CO2 capacity potential, modeling reactivity, and are also an important baseline for comparisons after CO2 injection. Copyright ??2011. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

  13. Effects of fracture reactivation and diagenesis on fracture network evolution: Cambrian Eriboll Formation, NW Scotland

    Science.gov (United States)

    Hooker, J. N.; Eichhubl, P.; Xu, G.; Ahn, H.; Fall, A.; Hargrove, P.; Laubach, S.; Ukar, E.

    2011-12-01

    The Cambrian Eriboll Formation quartzarenites contain abundant fractures with varying degrees of quartz cement infill. Fractures exist that are entirely sealed; are locally sealed by bridging cements but preserve pore space among bridges; are mostly open but lined with veneers of cement; or are devoid of cement. Fracture propagation in the Eriboll Formation is highly sensitive to the presence of pre-existing fractures. Fracture reactivation occurs in opening mode as individual fractures repeatedly open and are filled or bridged by syn-kinematic cements. As well, reactivation occurs in shear as opening of one fracture orientation coincides with shear displacement along pre-existing fractures of different orientations. The tendency for pre-existing fractures to slip varies in part by the extent of cement infill, yet we observe shear and opening-mode reactivation even among sealed fractures. Paleotemperature analysis of fluid inclusions within fracture cements suggests some fractures now in outcrop formed deep in the subsurface. Fractures within the Eriboll Formation may therefore affect later fracture propagation throughout geologic time. With progressive strain, fault zones develop within fracture networks by a sequence of opening-mode fracture formation, fracture reactivation and linkage, fragmentation, cataclasis, and the formation of slip surfaces. Cataclasite within fault zones is commonly more thoroughly cemented than fractures in the damage zone or outside the fault zone. This variance of cement abundance is likely the result of (1) continued exposure of freshly broken quartz surfaces within cataclasite, promoting quartz precipitation, and (2) possibly more interconnected pathways for mass transfer within the fault zone. Enhanced cementation of cataclasite results in strengthening or diagenetic strain hardening of the evolving fault zone. Further slip is accommodated by shear localization along discrete slip surfaces. With further linkage of fault segments

  14. The Middle Cambrian fossil Pikaia and the evolution of chordate swimming

    Directory of Open Access Journals (Sweden)

    Lacalli Thurston

    2012-07-01

    Full Text Available Abstract Conway Morris and Caron (2012 have recently published an account of virtually all the available information on Pikaia gracilens, a well-known Cambrian fossil and supposed basal chordate, and propose on this basis some new ideas about Pikaia’s anatomy and evolutionary significance. Chief among its chordate-like features are the putative myomeres, a regular series of vertical bands that extends the length of the body. These differ from the myomeres of living chordates in that boundaries between them (the myosepta are gently curved, with minimal overlap, whereas amphioxus and vertebrates have strongly overlapping V- and W-shaped myomeres. The implication, on biomechanical grounds, is that myomeres in Pikaia exerted much less tension on the myosepta, so the animal would have been incapable of swimming as rapidly as living chordates operating in the fast-twitch mode used for escape and attack. Pikaia either lacked the fast-twitch fibers necessary for such speeds, having instead only slow-twitch fibers, or it had an ancestral fiber type with functional capabilities more like modern slow fibers than fast ones. The first option is supported by the sequence of development in zebrafish, where both myoseptum formation and fast fiber deployment show a dependence on slow fibers, which develop first. For Pikaia, the absence of fast fibers has both behavioral and anatomical implications, which are discussed. Among the latter is the possibility that a notochord may not have been needed as a primary stiffening device if other structures (for example, the dorsal organ could perform that role.

  15. Geochronology and sources of late Neoproterozoic to Cambrian granites of the Saldania Belt

    Science.gov (United States)

    Chemale, F.; Scheepers, R.; Gresse, P. G.; van Schmus, W. R.

    2011-04-01

    The Saldania Belt (SB), located in the southernmost part of South Africa, contains S-, I-, and A-type granites. Whole-rock Sm-Nd data for the Saldania granites indicate the presence of a juvenile as well as inherited crustal signature. The earlier S-type granites have ɛNd( t) values from -4.2 to -3.28 (for t = 550 Ma). In contrast, the intermediate I-type and youngest A-type and highly fractionated I-type granites display ɛNd values ranging from -1.44 to -3.68 (for t = 540 Ma) and from +3.66 to +5.1(for t = 530 Ma), respectively. The U-Pb single zircon data of A-type granites exposed in the Western Branch of the SB yielded dates from 524 ± 8 to 510 ± 4 Ma, whereas an S-type granite, situated in the Southern Branch of the SB and represented by the syn- to late-tectonic Rooiklip Granite, yielded an age of 527 ± 8 Ma. The volcano-sedimentary rocks intruded by these granites display Nd model ages from Ga to 1.67 Ga and ɛNd( t) values from -6.58 to +3.34 (for t = 560 Ma) with isotope signature similar to those of the granites. The S- and I-type granitic magmatism is mostly a product of melting of an earlier crust (Mesoproterozoic to Paleoproterozoic) with different degree of juvenile contribution. The obtained isotope data and field relationship support the hypothesis that the lithological units of the SB were affected by the late Neoproterozoic to Early Cambrian tectonism, related to compressive deformational processes at the southern margin of the Kalahari Plate and probably correlated with the Sierra La Ventana Belt basement.

  16. Biostratigraphy and chronostratigraphy of the Cambrian-Ordovician great American carbonate bank

    Science.gov (United States)

    Taylor, John F.; Repetski, John E.; Loch, James D.; Leslie, Stephen A.

    2012-01-01

    The carbonate strata of the great American carbonate bank (GACB) have been subdivided and correlated with ever-increasing precision and accuracy during the past half century through use of the dominant organisms that evolved on the Laurentian platform through the Cambrian and the Ordovician. Trilobites and conodonts remain the primary groups used for this purpose, although brachiopods, both calcareous and phosphatic, and graptolites are very important in certain facies and intervals. A series of charts show the chronostratigraphic units (series and stages) currently in use for deposits of the GACB and the biostratigraphic units (zones, subzones, and biomeres) whose boundaries delineate them. Older and, in some cases obsolete, stages and faunal units are included in the figures to allow users to relate information from previous publications and/or industry databases to modern units. This chapter also provides a brief discussion on the use of biostratigraphy in the recognition and interregional correlation of supersequence boundaries within the Sauk and Tippecanoe megasequences, and the varied perspectives on the nature of biostratigraphic units and their defining taxa during the past half century. Also included are a concise update on the biomere concept, and an explanation of the biostratigraphic consequences of a profound change in the dynamics of extinction and replacement that occurred on the GACB in the Early Ordovician when the factors responsible for platformwide biomere-type extinctions faded and ultimately disappeared. A final section addresses recent and pending refinements in the genus and species taxonomy of biostratigraphically significant fossil groups, the potential they hold for greatly improved correlation, and the obstacles to be overcome for that potential to be realized.

  17. Multiple High-Frequency Carbon Isotope Excursions Across the Precambrian-Cambrian Boundary: Implications for Correlations and Environmental Change

    Science.gov (United States)

    Smith, E. F.; Macdonald, F. A.; Schrag, D. P.; Laakso, T.

    2014-12-01

    The GSSP Precambrian-Cambrian boundary in Newfoundland is defined by the first appearance datum (FAD) of Treptichnus pedum, which is considered to be roughly coincident with the FAD of small shelly fossils (SSFs) and a large negative carbon isotope excursion. An association between the FAD of T. pedum and a negative carbon isotope excursion has previously been documented in Northwest Canada (Narbonne et al., 1994) and Death Valley (Corsetti and Hagadorn, 2000), and since then has been used as an chronostratigraphic marker of the boundary, particularly in siliciclastic poor sections that do not preserve T. pedum. Here we present new high-resolution carbon isotope (δ13C ) chemostratigraphy from multiple sections in western Mongolia and the western United States that span the Ediacaran-Cambrian transition. High-resolution sampling (0.2-1 m) reveals that instead of one large negative excursion, there are multiple, high-frequency negative excursions with an overall negative trend during the latest Ediacaran. These data help to more precisely calibrate changes in the carbon cycle across the boundary as well as to highlight the potential problem of identifying the boundary with just a few negative δ13C values. We then use a simple carbon isotope box model to explore relationships between phosphorous delivery to the ocean, oxygenation, alkalinity, and turnovers in carbonate secreting organisms. Corsetti, F.A., and Hagadorn, J.W., 2000, Precambrian-Cambrian transition: Death Valley, United States: Geology, v. 28, no. 4, p. 299-302. Narbonne, G.M., Kaufman, A.J., and Knoll, A.H., 1994, Integrated chemostratigraphy and biostratigraphy of the Windermere Supergroup, northwestern Canada: Implications for Neoproterozoic correlations and the early evolution of animals: Geological Society of America Bulletin, v. 106, no. 10, p. 1281-1292.

  18. A xandarellid artiopodan from Morocco – a middle Cambrian link between soft-bodied euarthropod communities in North Africa and South China

    Science.gov (United States)

    Ortega-Hernández, Javier; Azizi, Abdelfattah; Hearing, Thomas W.; Harvey, Thomas H. P.; Edgecombe, Gregory D.; Hafid, Ahmid; El Hariri, Khadija

    2017-01-01

    Xandarellida is a well-defined clade of Lower Palaeozoic non-biomineralized artiopodans that is exclusively known from the early Cambrian (Stage 3) Chengjiang biota of South China. Here we describe a new member of this group, Xandarella mauretanica sp. nov., from the middle Cambrian (Stage 5) Tatelt Formation of Morocco, making this the first non-trilobite Cambrian euarthropod known from North Africa. X. mauretanica sp. nov. represents the youngest occurrence of Xandarellida – extending its stratigraphic range by approximately 10 million years – and expands the palaeobiogeographic distribution of the group to the high southern palaeolatitudes of West Gondwana. The new species provides insights into the lightly sclerotized ventral anatomy of Xandarellida, and offers stratigraphically older evidence for a palaeobiogeographic connection between Burgess Shale-type euarthropod communities in North Africa and South China, relative to the (Tremadocian) Fezouata biota. PMID:28211461

  19. A xandarellid artiopodan from Morocco - a middle Cambrian link between soft-bodied euarthropod communities in North Africa and South China.

    Science.gov (United States)

    Ortega-Hernández, Javier; Azizi, Abdelfattah; Hearing, Thomas W; Harvey, Thomas H P; Edgecombe, Gregory D; Hafid, Ahmid; El Hariri, Khadija

    2017-02-17

    Xandarellida is a well-defined clade of Lower Palaeozoic non-biomineralized artiopodans that is exclusively known from the early Cambrian (Stage 3) Chengjiang biota of South China. Here we describe a new member of this group, Xandarella mauretanica sp. nov., from the middle Cambrian (Stage 5) Tatelt Formation of Morocco, making this the first non-trilobite Cambrian euarthropod known from North Africa. X. mauretanica sp. nov. represents the youngest occurrence of Xandarellida - extending its stratigraphic range by approximately 10 million years - and expands the palaeobiogeographic distribution of the group to the high southern palaeolatitudes of West Gondwana. The new species provides insights into the lightly sclerotized ventral anatomy of Xandarellida, and offers stratigraphically older evidence for a palaeobiogeographic connection between Burgess Shale-type euarthropod communities in North Africa and South China, relative to the (Tremadocian) Fezouata biota.

  20. Geochemistry of the Cambrian-Ordovician aquifer system in the northern Midwest, United States: D in Regional aquifer-system analysis

    Science.gov (United States)

    Siegel, D.I.

    1989-01-01

    Distributions of solutes in aquifers of Cambrian and Ordovician age were studied in Minnesota, Wisconsin, Iowa, Illinois, northwestern Indiana, and northern Missouri to determine the sources of solutes and the probable chemical mechanisms that control regional variations in water quality. This work is part of the Northern Midwest Regional Aquifer-System Analysis project, whose objective is to describe and model the regional hydrogeology of the Cambrian- Ordovician aquifer system in the study region. The data base used included more than 3,000 ground-water-quality analyses from all major aquifers, but especially from the St. Peter, Jordan, and Mount Simon Sandstones and their equivalents. Regional variations in the water chemistry of glacial drift and other sedimentary units that overlie the Cambrian-Ordovician aquifer system in recharge areas in Minnesota, Iowa, Wisconsin, and Illinois were also studied, but to a lesser degree.

  1. A xandarellid artiopodan from Morocco – a middle Cambrian link between soft-bodied euarthropod communities in North Africa and South China

    Science.gov (United States)

    Ortega-Hernández, Javier; Azizi, Abdelfattah; Hearing, Thomas W.; Harvey, Thomas H. P.; Edgecombe, Gregory D.; Hafid, Ahmid; El Hariri, Khadija

    2017-02-01

    Xandarellida is a well-defined clade of Lower Palaeozoic non-biomineralized artiopodans that is exclusively known from the early Cambrian (Stage 3) Chengjiang biota of South China. Here we describe a new member of this group, Xandarella mauretanica sp. nov., from the middle Cambrian (Stage 5) Tatelt Formation of Morocco, making this the first non-trilobite Cambrian euarthropod known from North Africa. X. mauretanica sp. nov. represents the youngest occurrence of Xandarellida – extending its stratigraphic range by approximately 10 million years – and expands the palaeobiogeographic distribution of the group to the high southern palaeolatitudes of West Gondwana. The new species provides insights into the lightly sclerotized ventral anatomy of Xandarellida, and offers stratigraphically older evidence for a palaeobiogeographic connection between Burgess Shale-type euarthropod communities in North Africa and South China, relative to the (Tremadocian) Fezouata biota.

  2. Dam sediment tracking using spectrometry and Landsat 8 satellite image, Taleghan Basin, Iran.

    Science.gov (United States)

    Afshar, Sirous; Shamsai, Abolfazl; Saghafian, Bahram

    2016-02-01

    Sedimentation in reservoirs, in addition to reducing water storage capacity, causes serious environmental impacts including intensification of river erosion. Detection of sediment origins plays a determining role in control and prevention of sedimentation. Nowadays, with the help of studies on sedimentation and erosion, sediment origins can be detected with high accuracy. This research integrated geographic information system (GIS) and remote sensing (RS) techniques to detect the primary source of sediment to Taleghan Dam in northern Iran. After collecting samples of sediment from the basin outlet, they were divided into two parts. One part was sent to the Mineralogy Laboratory in order to determine the percentage of each mineral in the samples using X-ray. A few were sent to the Spectroscopy Laboratory to determine their spectral signature using the spectrometer. The laboratory test results determined the wavelength of the minerals. In the next step, those spots on the satellite image whose spectral reflectance fell within the spectral signature of the minerals were detected and enhanced by mixture-tuned matched filtering (MTMF) method. These spots were overlapped with the map of geological formations. Accordingly, the origin of the minerals was detected. The greatest proportion of trace minerals was found in sample 4 including 6% of Illite trace mineral, while sample 2 contains only 2% of trace minerals. Accordingly, the origin of the minerals was detected. The obtained results revealed that mudstone, red siltstone, and conglomerate formations, Karaj formation in section Poldokhtar, acidic tuffs, alcanic lavas of Karaj Formation, mudstone and gypsum of upper red formation, and Cambrian dolomites were recognized as the most possible origins of the dam sediments. These formations are vulnerable to erosion and should be conserved so as to substantially prevent the volume of sedimentation in the reservoir.

  3. Study of Noble Metal Elements in Lower Cambrian Black Rock Series of Guizhou-Hunan Provinces, China

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Systematic analyses of noble metal elements in the Lower Cambrian black rock series of South China are reported. Correlations of w(Os)/w(Ir), w(Au)/w(Ir), w(Ag)/w(Au), w(Pt+Pd)/w(Os+Ru+Rh+Ir), relations of noble metal and platinum group element (PGE) distribution patterns reveal that the noble metals are not directly from extraterrestrial materials. Studying the data of 9 aspects, the authors conclude that the noble metals were mainly from ultramafic-mafic igneous rocks and their enrichment in black rocks is mainly controlled by hydrothermal fluid.

  4. High-Precision U-Pb Geochronology and Correlation: An example Using the Neoproterozic-Cambrian Transition

    Science.gov (United States)

    Bowring, S. A.; Grotzinger, J. P.; Amthor, J.; Martin, M. E.

    2001-05-01

    The precise, global correlation of Precambrian and Paleozoic sedimentary rocks can be achieved using temporally calibrated chemostratigraphic records. This approach is essential for determining rates and causes of environmental and faunal change, including mass extinctions. For example, The Neoproterozoic is marked by major environmental change, including periods of global glaciation, large fluctuations in the sequestration of carbon and major tectonic reorganization followed by the explosive diversification of animals in the earliest Cambrian. The extreme climatic change associated with these glaciations have been implicated as a possible trigger for the Cambrian explosion. The recognition of thin zircon-bearing air-fall ash in Neoproterozoic and Cambrian rocks has allowed the establishment of a high-precision temporal framework for animal evolution and is helping to untangle the history of glaciations. In some cases analytical uncertainties translate to age uncertainties of less than 1 Ma and when integrated with chemostratigraphy, the potential for global correlations at even higher resolution. Progress in the global correlation of Neoproterozoic strata has been achieved through the use of C and Sr isotope chemostratigraphy although it has been hampered by a lack of precise geochronological and faunal control. For example, the period from ca 800-580 Ma is characterized by at least two and perhaps as many as four glacial events that are interpreted by many to be global glaciations on a "Snowball Earth". A lack of precise chronological constraints on the number and duration of glaciations, multiple large excursions in the carbon isotopic record, and an absence of detailed biostratigraphy have complicated global correlation and hindered our understanding of this important period of Earth history. However, the ongoing integration of chemostratigraphic and geochronological data are improving temporal resolution and detailed correlations. These data are critical for

  5. Hydrogeology of the Cambrian-Ordovician aquifer system in the northern Midwest: B in Regional aquifer-system analysis

    Science.gov (United States)

    Young, H.L.; Siegel, D.I.

    1992-01-01

    The Cambrian-Ordovician aquifer system contains the most extensive and continuous aquifers in the northern Midwest of the United States. It is the source of water for many municipalities, industries, and rural water users. Since the beginning of ground-water development from the aquifer system in the late 1800's, hydraulic heads have declined hundreds of feet in the heavily pumped Chicago-Milwaukee area and somewhat less in other metropolitan areas. The U.S. Geological Survey has completed a regional assessment of this aquifer system within a 161,000-square-mile area encompassing northern Illinois, northwestern Indiana, Iowa, southeastern Minnesota, northern Missouri, and Wisconsin.

  6. REE Enrichment in Early Cambrian Gezhongwu Formation Phosphorous Rock Series in Sanjia, Zhijin County, Guizhou Province, China

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Phosphate concretions from the Gezhongwu Formation at Sanjia, Zhijin County, China, were studied systematically in this work. In terms of the rules of variation of REE, trace elements, major elements and oxides, in combination with the concentration characteristics of small shelly fossils, it is considered that small shelly fossils occurring at the bottom of the Cambrian System contribute a lot to the phosphate concretions and that there are two stages of REE and phosphorus minerogenesis. The phosphate concretions have a good correlation with the contents of REE and phosphorus rather than the abundance of small shelly fossils.

  7. New geochemical and geochronological data of early Cambrian of (SW Iberia): Calc-alkaline magmatism in the transition from active to passive continental margin in North Gondwana

    OpenAIRE

    Sanchez-Garcia, Teresa; Pereira, M. Francisco; Bellido, Felix; Chichorro, Martim; Silva, J. Brandao; Valverde-Vaquero, Pablo; Pin, Christian; Solá, Rita

    2011-01-01

    The Ossa-Morena Zone (SW Iberia) displays a well-preserved record of the history of the northern Gondwana margin in Late Ediacaran-Early Cambrian times. This period of time is marked by the late-stage evolution of the Cadomian magmatic arc and related back-arc basins (c. 590-545 Ma), and the onset of rifting and widespread magmatism (c. 530-500 Ma) that led to the opening of the Rheic Ocean. Here we present new geochemical and geochronological data on some Cambrian granitoids of Ossa-Morena ...

  8. From Basin Black Shales to Platform Carbonate Rocks: A Study on Sequence Stratigraphy for the Lower Cambrian of the Upper-Yangtze Region in South China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In the Upper-Yangtze region, especially in Guizhou Province and its adjacent areas, the Lower Cambrian is well developed and is marked by a succession from black shales of the basin facies to carbonate rocks of the platform facies. The drowning event of the platform occurring at the turn from Sinian to Cambrian resulted in a set of black shales, i.e. the Niutitang Formation, which makes up the bottom part of the Lower Cambrian. With the shoaling of the sedimentary environment, a set of carbonate rocks, i.e. the Qingxudong Formation, was formed in the top part of the Lower Cambrian. Thus, the Lower Cambrian in the study area makes up one second-order sequence that can be further subdivided into five third-order sequences, and forms a regularly cyclic succession of transgression-regression. There is a regularly vertical stacking pattern for the third-order sequences in the second-order sequence. From bottom to top, the succession of the "CS (condensed section)+HST (high-stand system tract)" of the third-order sequences is changed into the succession of the "TST (transgressive system tract)+CS+HST". Correspondingly, the drowning-type sequence boundary is changed into the exposure-type one. Therefore, both the second-order and the third-order sequences have similar sedimentary-facies architectures. A concomitant with these temporal changes,the Lower Cambrian with a thickness of 1000 m that contains five third-order sequences is changed into a condensed succession that cannot identify third-order sequences toward the southeast with the deepening of the sedimentary environment. According to the elementary features of the third-order sequences, i.e. the regularity o sedimentary-facies successions in space and the synchronism of sedimentary-environment changes in time, the detailed division of the third-order sequences at main logged sections in different paleogeographical background becomes the basis to establish the sequence-stratigraphic framework that can demonstrate

  9. A kind of coccoid dinoflagel-lates-like fossils gives a new explanation of source of dinosterane in the Early- Middle Cambrian

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The coccoid fossils covered with thick gelatinous envelop containing several gametes are discovered in gyps and salt deposits of Cambrian, H4 well and chert bed of the base of Yuertus Formation (∈11) of Xiaoerbulake Section. The fossils are described and compared with coccoid dino-flagellates. These fossils may be a coccoid life-cycle stage (vegetative cyst) of coccoid dinoflagellates. If this identifica-tion is correct, the coccoid dinoflagellates-like fossils could give a reasonable explanation of the dinoflagellate-specific biomarkers from Cambrian, H4 well, Tarim Basin.

  10. National Geochemical Database: Sediment

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Geochemical analysis of sediment samples from the National Geochemical Database. Primarily inorganic elemental concentrations, most samples are of stream sediment...

  11. Ocean Sediment Thickness Contours

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ocean sediment thickness contours in 200 meter intervals for water depths ranging from 0 - 18,000 meters. These contours were derived from a global sediment...

  12. Center for Contaminated Sediments

    Data.gov (United States)

    Federal Laboratory Consortium — The U.S. Army Corps of Engineers Center for Contaminated Sediments serves as a clearinghouse for technology and expertise concerned with contaminated sediments. The...

  13. National Geochemical Database: Sediment

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Geochemical analysis of sediment samples from the National Geochemical Database. Primarily inorganic elemental concentrations, most samples are of stream sediment in...

  14. Organic Carbon Isotopic Evolution during the Ediacaran-Cambrian Transition Interval in Eastern Guizhou, South China: Paleoenvironmental and Stratigraphic Implications

    Institute of Scientific and Technical Information of China (English)

    YANG Xinglian; ZHU Maoyan; GUO Qingjun; ZHAO Yuanlong

    2007-01-01

    Secular variations of carbon isotopic composition of organic carbon can be used in the study of global environmental variation, the carbon cycle, stratigraphic delimitation, and biological evolution, etc. Organic carbon isotopic analysis of the Nangao and Zhalagou sections in eastern Guizhou reveals a negative excursion near the Precambrian-Cambrian boundary that correlates with a distinct carbonate carbon isotopic negative excursion at this boundary globally. Our results also demonstrate that several alternating positive and negative shifts occur in the Meishucunian, and an obvious negative anomaly appears at the boundary between the Meishucunian and Qiongzhusian. The isotope values are stable in the middle and lower parts but became more positive in the upper part of the Qiongzhusian. Evolution of organic carbon isotopes from the two sections in the deepwater facies can be well correlated with that of the carbonate carbon isotopes from the section in the shallow water facies. Integrated with other stratigraphic tools, we can precisely establish a lower Cambrian stratigraphic framework from shallow shelf to deep basin of the Yangtze Platform.

  15. Oxygen-isotope trends and seawater temperature changes across the Late Cambrian Steptoean positive carbon-isotope excursion (SPICE event)

    Science.gov (United States)

    Elrick, M.; Rieboldt, S.; Saltzman, M.; McKay, R.M.

    2011-01-01

    The globally recognized Late Cambrian Steptoean positive C-isotope excursion (SPICE) is characterized by a 3???-5??? positive ??13C shift spanning SPICE represents a widespread ocean anoxic event leading to enhanced burial/preservation of organic matter (Corg) and pyrite. We analyzed ??18O values of apatitic inarticulate brachiopods from three Upper Cambrian successions across Laurentia to evaluate paleotemperatures during the SPICE. ??18O values range from ~12.5??? to 16.5???. Estimated seawater temperatures associated with the SPICE are unreasonably warm, suggesting that the brachiopod ??18O values were altered during early diagenesis. Despite this, all three localities show similar trends with respect to the SPICE ??13C curve, suggesting that the brachiopod apatite preserves a record of relative ??18O and temperature changes. The trends include relatively high ??18O values at the onset of the SPICE, decreasing and lowest values during the main event, and an increase in values at the end of the event. The higher ??18O values during the global extinction at the onset of the SPICE suggests seawater cooling and supports earlier hypotheses of upwelling of cool waters onto the shallow shelf. Decreasing and low ??18O values coincident with the rising limb of the SPICE support the hypothesis that seawater warming and associated reduced thermohaline circulation rates contributed to decreased dissolved O2 concentrations, which enhanced the preservation/burial of Corg causing the positive ??13C shift. ?? 2011 Geological Society of America.

  16. Three-dimensionally preserved minute larva of a great-appendage arthropod from the early Cambrian Chengjiang biota

    Science.gov (United States)

    Liu, Yu; Melzer, Roland R.; Haug, Joachim T.; Haug, Carolin; Briggs, Derek E. G.; Hörnig, Marie K.; He, Yu-yang; Hou, Xian-guang

    2016-05-01

    A three-dimensionally preserved 2-mm-long larva of the arthropod Leanchoilia illecebrosa from the 520-million-year-old early Cambrian Chengjiang biota of China represents the first evidence, to our knowledge, of such an early developmental stage in a short-great-appendage (SGA) arthropod. The larva possesses a pair of three-fingered great appendages, a hypostome, and four pairs of well-developed biramous appendages. More posteriorly, a series of rudimentary limb Anlagen revealed by X-ray microcomputed tomography shows a gradient of decreasing differentiation toward the rear. This, and postembryonic segment addition at the putative growth zone, are features of late-stage metanauplii of eucrustaceans. L. illecebrosa and other SGA arthropods, however, are considered representative of early chelicerates or part of the stem lineage of all euarthropods. The larva of an early Cambrian SGA arthropod with a small number of anterior segments and their respective appendages suggests that posthatching segment addition occurred in the ancestor of Euarthropoda.

  17. Experimental mineralization of crustacean eggs leads to surprising tissue conservation: new implications for the fossilization of Precambrian-Cambrian embryos

    Science.gov (United States)

    Hippler, D.; Hu, N.; Steiner, M.; Scholtz, G.; Franz, G.

    2011-12-01

    Phosphatized globular microfossils from the Ediacaran and Lower Cambrian of South China represent an impressive record of early animal evolution and development, however their affinity based on putative embryonic metazoan, bacterial and inorganic features is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are therefore crucial for a reliable interpretation of their phylogenetic position. Taphonomic experiments on eggs of the marbled crayfish indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope, producing different preservational stages of degradation resembling the various decay stages observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4·2H2O) over calcite as the dominating mineral phase. Although the endochorional envelope was not preserved, experiments resulted in exceptional preservation of the embryonic tissue at the cellular level. Thus our findings suggest that the mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment and during fossilization of Cambrian embryos were likely operating at a similar rationale.

  18. Experimental mineralization of crustacean eggs leads to surprising tissue conservation: new implications for the fossilization of Precambrian-Cambrian embryos

    Directory of Open Access Journals (Sweden)

    D. Hippler

    2011-12-01

    Full Text Available Phosphatized globular microfossils from the Ediacaran and Lower Cambrian of South China represent an impressive record of early animal evolution and development, however their affinity based on putative embryonic metazoan, bacterial and inorganic features is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are therefore crucial for a reliable interpretation of their phylogenetic position. Taphonomic experiments on eggs of the marbled crayfish indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope, producing different preservational stages of degradation resembling the various decay stages observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4·2H2O over calcite as the dominating mineral phase. Although the endochorional envelope was not preserved, experiments resulted in exceptional preservation of the embryonic tissue at the cellular level. Thus our findings suggest that the mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment and during fossilization of Cambrian embryos were likely operating at a similar rationale.

  19. Geochemistry of black shale at the bottom of the Lower Cambrian in Tarim Basin and its significance for lithosphere evolution

    Institute of Scientific and Technical Information of China (English)

    YU; Bingsong; (于炳松); CHEN; Jianqiang; (陈建强); LI; Xingwu; (李兴武); LIN; Changsong; (林畅松)

    2003-01-01

    The systematic analyses of trace elements, REEs and PGEs of black shale at the bottom of the Lower Cambrian in Tarim Basin have been made for the first time in this work. The basic geochemical features are that some trace elementshaving something to do with the deep-level fluids are highly enriched, including V, Cr, Ni, Cu, Zn, Ge, As, Sr, Y, Mo, Ag, Cd, Sb, Ba, Pb and U, and the Th/U and Th/Sc ratios decreased compared with those in the same kind of rocks in the crust, that the enriched degrees of LREEs are reduced, Eu and Ce depleted distinctly in the chondrite-normalized REE patterns, and that the contents of PGEs and Au are increased. These characteristics indicate that there were more mafic interior sources in the basin when the black shale was deposited. Generally, the interior sources show an extensional tectonic setting of lithosphere. It can be seen from the change of the characteristics of trace elements, REEs and PGEs along the black shale section that the quantity of interior source from inner earth isgradually increased upwards in the lower part of the section, reaches the peakvalue as shown by sample No. 4 (XCM7-1), and then decreased, which might indicate the episodic extension of lithosphere in the beginning of the Lower Cambrian.

  20. Late Neoproterozoic to early Cambrian sulphur cycle-An isotopic investigation of sedimentary rocks from the Yangtze Platform

    Institute of Scientific and Technical Information of China (English)

    Tatiana GOLDBERG; Harald STRAUSS; GUO Qingjun; LIU Congqiang

    2003-01-01

    The sulphur cycle responds to changes in seawater chemistry, biological evolution and tectonic activity. We follow an isotopic approach in order to constrain the state of the ocean/atmosphere system during late Neoproterozoic and early Cambrian. For this purpose, a sedimentary succession deposited on the Yangtze Platform, South China, was analysed for its sulphur isotopic composition in different S-bearing phases. Redox changes were defined by the degree of pyritization (DOP) values in order to show variations in the oxygenation of the depositional environment. The sulphur isotopic composition of late Neoproterozoic to early Cambrian seawater sulphate ranges from +30‰ to +35‰ as evident from trace sulphate in unaltered carbonates and phosphorites. The isotopic composition for pyrite and organic sulphur varies between -16‰ and +23‰. The apparent sulphur isotopic fractionation between seawater sulphate and pyrite as well as organically bound sulphur varies between 7‰ and 50‰. This large fractionation, as well as its variability suggests a biological origin for pyrite and organically bound sulphur. The temporal evolution of different geochemical proxy signals is comparable for different successions across the Yangtze Platform.

  1. Phylogenomic insights into the cambrian explosion, the colonization of land and the evolution of flight in arthropoda.

    Science.gov (United States)

    Wheat, Christopher W; Wahlberg, Niklas

    2013-01-01

    The timing of the origin of arthropods in relation to the Cambrian explosion is still controversial, as are the timing of other arthropod macroevolutionary events such as the colonization of land and the evolution of flight. Here we assess the power of a phylogenomic approach to shed light on these major events in the evolutionary history of life on earth. Analyzing a large phylogenomic dataset (122 taxa, 62 genes) with a Bayesian-relaxed molecular clock, we simultaneously reconstructed the phylogenetic relationships and the absolute times of divergences among the arthropods. Simulations were used to test whether our analysis could distinguish between alternative Cambrian explosion scenarios with increasing levels of autocorrelated rate variation. Our analyses support previous phylogenomic hypotheses and simulations indicate a Precambrian origin of the arthropods. Our results provide insights into the 3 independent colonizations of land by arthropods and suggest that evolution of insect wings happened much earlier than the fossil record indicates, with flight evolving during a period of increasing oxygen levels and impressively large forests. These and other findings provide a foundation for macroevolutionary and comparative genomic study of Arthropoda.

  2. Chemostratigraphies of carbon, oxygen and strontium isotopes and oxygen contents across the Precambrian-Cambrian boundary

    Science.gov (United States)

    Komiya, T.; Sawaki, Y.; Ishikawa, T.

    2007-12-01

    The Precambrian-Cambrian (PC-C) boundary is one of the most important intervals for evolution of life. However, the scarcity of well-preserved outcrops through the boundary makes it ambiguous to decode change of the surface environment and biological evolution. In south China, strata through the PC-C boundary are continuously exposed and contain many fossils, suitable for study of environmental and biological change. In addition, we conducted excavations at four sites of Three Gorge area to obtain continuous and fresh samples. We measured the delta13C, delta18O and 87Sr/86Sr values of the drill core samples and REE compositions of fresh carbonate rocks, respectively. We identified two positive and two negative isotope excursions of delta13Ccarb within this interval: a moderate increase from 0 to +2 permil and a subsequent dramatic drop to -7 permil at the PC-C boundary, and a continuous increase to +5 permil at the upper part of the Nemakit-Daldynian (ND) stage and the subsequent sharp decrease to -9 permil just below the basal Tommotian unconformity, respectively. The continuous pattern of the delta13C shift is irrespective of lithotype and is comparable to fragmented records of other sections within and outside of the Yangtze Platform, indicating that the profile represents global change of seawater chemistry. A chemostratigraphy of 87Sr/86Sr ratios of the drilled samples also displays a smooth curve and its large positive anomaly just below the PC-C boundary. The estimate of oxygen content of seawater from REE composition of carbonate minerals shows significant decreases around PC-C and ND-Tommotian boundaries, respectively. The combination of chemostratigraphies of delta13C, 87Sr/86Sr and pO2 indicates that the 87Sr/86Sr excursions preceded the delta13C negative excursion at PC-C boundary, and suggests that global regression or formation of the Gondwana supercontinent, evident in increase of influx of continental materials, caused biological depression together

  3. Evidence for a lack of biological P-cycling in a Cambrian soil

    Science.gov (United States)

    Wei, Z.; Peng, Y.; Bao, H.

    2015-12-01

    The earliest fossil land plants are known to exist in the Mid-Ordovician at 472 to 468 Ma and protein sequence analyses suggest that the onset of land colonization may have begun at as early as ca. 700-1000 million years ago (Ma) . However, fully established soil ecosystem may not be in place until after the Devonian (ca. 400 Ma) or even later. Dearth of fossil record on possible fungi- and/or bacteria-dominated early land biota renders it difficult to establish the early history of land colonization on Earth. Here we present a proxy for soil biological P- cycling. Igneous rock contains typically 0.005-0.4% (wt) phosphate (PO4-3). In a biologically active soil weathering profile, phosphorus (P) is cycled by land biota including by those of the most primitive kingdoms. During, for example, pyrophosphate hydrolysis, the P-O bonds in PO4-3 breaks and exchange oxygen with ambient water. The biologically processed PO4-3 will have typically much higher δ18Ovalues (15-24‰ VSMOW) than the ones inherited from igneous sources (ca. 6‰). Therefore, an increase in the δ18OPO4 from pristine igneous rocks to the upper more weathered ones should be expected if there was an active soil biological P-cycling. An igneous-PO4 δ18O value in the more weathered rocks would otherwise indicate a lack of biologically-mediated P-cycling, thus a lack of or very limited land colonization. We examined a weathering profile in the Elk Point Formation (520-503Ma), South Dakota, a paleosol developed on a metagabbro in a subtropical climate of the Mid-Cambrian. Phosphate was extracted from a drill core of this profile and was analyzed for δ18OPO4. The δ18OPO4 for the weathered and un-weathered igneous rocks are all within a narrow range of 4.8-8.2‰, suggesting that biological P-cycling was insignificant during the weathering of Elk Point metagabbro at ca. 500 Ma. Subaerial, biologically mediated weathering probably did not play a role in geochemical cycling on Earth until much later in

  4. Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution☆

    Science.gov (United States)

    Fritz, H.; Abdelsalam, M.; Ali, K.A.; Bingen, B.; Collins, A.S.; Fowler, A.R.; Ghebreab, W.; Hauzenberger, C.A.; Johnson, P.R.; Kusky, T.M.; Macey, P.; Muhongo, S.; Stern, R.J.; Viola, G.

    2013-01-01

    The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world́s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara–Congo–Kalahari Cratons in the west and Neoproterozoic India in the east. Orogen consolidation was achieved during distinct phases of orogeny between ∼850 and 550 Ma. The northern part of the orogen, the Arabian–Nubian Shield, is predominantly juvenile Neoproterozoic crust that formed in and adjacent to the Mozambique Ocean. The ocean closed during a protracted period of island-arc and microcontinent accretion between ∼850 and 620 Ma. To the south of the Arabian Nubian Shield, the Eastern Granulite–Cabo Delgado Nappe Complex of southern Kenya, Tanzania and Mozambique was an extended crust that formed adjacent to theMozambique Ocean and experienced a ∼650–620 Ma granulite-facies metamorphism. Completion of the nappe assembly around 620 Ma is defined as the East African Orogeny and was related to closure of the Mozambique Ocean. Oceans persisted after 620 Ma between East Antarctica, India, southern parts of the Congo–Tanzania–Bangweulu Cratons and the Zimbabwe–Kalahari Craton. They closed during the ∼600–500 Ma Kuungan or Malagasy Orogeny, a tectonothermal event that affected large portions of southern Tanzania, Zambia, Malawi, Mozambique, Madagascar and Antarctica. The East African and Kuungan Orogenies were followed by phases of post-orogenic extension. Early ∼600–550 Ma extension is recorded in the Arabian–Nubian Shield and the Eastern Granulite–Cabo Delgado Nappe Complex. Later ∼550–480 Ma extension affected Mozambique and southern Madagascar. Both extension phases, although diachronous,are interpreted as the result of lithospheric delamination. Along the strike of the East African Orogen, different geodynamic settings

  5. Relations between spatial distribution and sequence types of the Cambrian-Ordovician marine source rocks in Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Marine source rocks are considered to be mainly composed of the Cambrian-Ordovician deposit in Tarlm Basin. Based on the previous studies made by other researchers, the authors calculated the thickness and distribution scale of these Cambrian-Ordovician source rocks by integrating sequence stratigraphy with investigations on sedimentary environments, well-shooting demarcating and calibrating the thickness of unknown source rocks with the thickness of the known ones according to characteristics of the source rocks that have "double track" seismic lineup reflectance. The results showed that the distribution area of the Lower-Cambrian Yuertusi Fm. source rock in platform inner depressions, slopes and deep basins is much bigger than that of the Middle Cambrian evaporite-lagoon source rock. Moreover, the former is superior to the latter In terms of the source rock quality. Likewise,the Middle-Ordovician Heituao Fm. source rock in the slopes and deep basins has a much wider distribution and better quality than the Upper Ordovician, and its quality is also better than those of the Shaergan and Yinggan Fms. source rock within platforms as well as the lime-mud-mound source rock along the fringe of the Upper-Ordovician platform. Most good Lower-Cambrian source rocks of the Kalpin outcrop lie on the initial ingression surface or in the condensed member of the Type Ⅰ sequence.In this section, the source rock in Type Ⅱ is inferior to that in Type Ⅰ, even being far from an effective one (TOC: <0.5%). Likewise, the good Middle-Ordovician Heituao source rock also lies on the initial ingression surface or in the condensed member of the Type Ⅰ sequence, while the poor Yinggan source rock and the lime-mud-mound along the fringe of the platform develop all in the Type Ⅱ sequence. Under the condition of the same sea-level rising altitude and time, the Ingression displacement (S1) at the base border in Type lis larger than S2 in Type Ⅱ. Thus, the distribution of the source

  6. The Sirius Passet Lagerstätte: silica death masking opens the window on the earliest mat ground community of the Cambrian Explosion

    NARCIS (Netherlands)

    Strang, Katie M; Armstrong, Howard; Harper, David A. T.; Trabucho-Alexandre, João

    2016-01-01

    The Sirius Passet Lagerstätte (SP), Peary Land, North Greenland, occurs in black slates deposited at or just below storm wave base. It represents the earliest Cambrian microbial mat community with exceptional preservation, predating the Burgess Shale by 10 million years. Trilobites from the SP are p

  7. Santos estuarine sediments, Brazil - metal and trace element assessment by neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Amorim, Eduardo P.; Favaro, Deborah I.T., E-mail: ducamorim@yahoo.com.b, E-mail: defavaro@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP) Sao Paulo, SP (Brazil); Berbel, Glaucia; Braga, Elisabete S., E-mail: edsbraga@usp.b [Universidade de Sao Paulo (USP), SP (Brazil). Inst. Oceanografico. Lab. de Nutrientes, Micronutrientes e Tracos nos Oceanos (LABNUT)

    2009-07-01

    The Santos estuary system is an intricate pattern of tidal channels and small rivers originating from the adjacent Pre-Cambrian slopes. These two major estuaries share a common area in the upper portion of the region which interacts with each other. The largest harbor in Latin America is located at the eastern outlet of the Santos estuary. This intricate and sensitive ecosystem is highly susceptible to human impact from industrial activities, urban sewage and polluted solid wastes disposal. Due to its high vulnerability CETESB (Environmental Control Agency of the Sao Paulo State) sporadically monitors the contamination levels of water, sediment and marine organisms in this region. The present study reports results concerning the distribution of some major, trace and rare earth elements in the Santos estuarine marine sediments. Thirty two bottom sediment samples (SS0601 to SS0616 (summer) and SW0601 to SW0616 (winter) were collected in this estuary, including regions of Sao Vicente, Santos, Cubatao and Vicente de Carvalho, by a vanVeen sampler in the summer and winter of 2006. Multielemental analysis was carried out by instrumental neutron activation analysis (INAA). The concentration values obtained for As and metals Cr and Zn in the sediment samples were compared to Canadian Council of Minister of the Environment (CCME) oriented values (TEL and PEL values) and are adopted by CETESB. (author)

  8. A Cambrian intra-oceanic subduction system in the Bozshakol area, Kazakhstan

    Science.gov (United States)

    Shen, Ping; Pan, Hongdi; Seitmuratova, Eleonora; Yuan, Feng; Jakupova, Sholpan

    2015-05-01

    adakites. Therefore, Bozshakol intrusive rocks were also derived from the mantle wedge and minor slab melts. We propose a model of intra-oceanic subduction for the Middle to Late Cambrian magmatic evolution of magmatic arcs in northwestern central Kazakhstan.

  9. Lack of inhibiting effect of oil emplacement on quartz cementation: Evidence from Cambrian reservoir sandstones, Paleozoic Baltic Basin

    DEFF Research Database (Denmark)

    Molenaar, Nicolaas; Cyziene, Jolanta; Sliaupa, Saulius;

    2008-01-01

    Currently, the question of whether or not the presence of oil in sandstone inhibits quartz cementation and preserves porosity is still debated. Data from a number of Cambrian sandstone oil fields and dry fields have been studied to determine the effects of oil emplacement on quartz cementation...... cementation is derived from internal sources. Rather, in spite of large variation in porosity and quartz cement content, a regular pattern of porosity decrease is related to increasing temperature or depth. The observed heterogeneity is due to local factors that influence the precipitation of quartz cement......, including sandstone architecture, i.e., distribution of shales within the sandstone bodies, and sandstone thickness. Heterogeneity is inherent to sandstone architecture and to the fact that silica for quartz cementation is derived from heterogeneously distributed local pressure solution. Models predicting...

  10. Bryophyte-like Fossil (Parafunaria sinensis) from Early-Middle Cambrian Kaili Formation in Guizhou Province, China

    Institute of Scientific and Technical Information of China (English)

    YANGRui-Dong; MAOJia-Rer; ZHANGWei-Hua; JIANGLi-Jun; GAOHui

    2004-01-01

    Abundant well-preserved animal and macroalgal fossils were discovered in the Early-MiddleCambrian Kaili Formation of Taijiang County, Guizhou Province, China, which constitute the Kaili Biota,named as one of the three important Burgess Shale-type faunas. The bryophyte-like fossil (Parafunariasinensis Yang gen. et sp. nov) was discovered in the horizon of occurrence of Macroalgal fossils. The fossilof P. sinensis possesses typical characters of bryophyte, such as whorled leaves, capsule and seta, andcomplex rhizoid or foot. We infer that the bryophyte-like fossil could be the ancestor of bryophyte. Thediscovery provides a new lead for further study on the origin and evolution of bryophyte or land plant.

  11. Skara hunanensis a new species of Skaracarida (Crustacea)from Upper Cambrian (Furongian) of Hunan, south China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The fossils of Orsten-type preservation are as famous as Chengjiang Fauna in the world, but it was not until 2005 that the Orsten-type fossils represented by Skaracarida and Phosphatocopida were first reported to be found in western Hunan, South China.Here, we report the systematic paleontology of all the exquisitely preserved specimens belonging to Skaracarida. They were found at a same horizon of Upper Cambrian (Furongian) in Wangcun section, western Hunan, south China, assigned to a new species Skara hunanensis herein. Skara hunanensis is characterized by small, soft-integumented, marine forms with slender, annulate body; labrum large and ventrocaudally directed; uniramous antennulae; biramous antennae and mandibulae; maxillas and maxillipeds of the same shape; all postantennular limbs join a short cephalic filter apparatus. The body has two tagmata: a cephalon with five pairs of well developed appendages and a trunk composed of 11 rig-shaped conical segments.

  12. Siliceous spicules in a vauxiid sponge (Demospongia) from the Kaili Biota(Cambrian Stage 5), Guizhou, South China

    Science.gov (United States)

    Yang, X.-L.; Zhao, Y.-L.; Babcock, L. E.; Peng, J.

    2017-02-01

    Fossils of the sponge Angulosuspongia sinensis from calcareous mudstones of the middle and upper part of the Kaili Formation (Cambrian Stage 5) in the Jianhe area of Guizhou province, South China, exhibit an apparently reticulate pattern, characteristic of the Vauxiidae. Energy Dispersive X-Ray Spectrometry (EDS) and Raman spectroscopy analysis indicate the presence of silica in the skeletal elements of these fossils, suggesting that this taxon possessed a skeleton comprised of spicules. This is the first confirmation of siliceous skeletal elements in fossils of the family Vauxiidae, and it lends support to the hypothesis that some early demosponges possessed biomineralized siliceous skeletons, which were subsequently lost and replaced by spongin later in the evolutionary history of this lineage. The new materials provide critical insight into the phylogeny and evolution of biomineralization in the Demosopongiae.

  13. Phosphatized Punctatus with mouthparts and its embryo fossils from the Lower Cambrian of Ningqiang, south Shaanxi, China

    Institute of Scientific and Technical Information of China (English)

    LIU Yunhuan; LI Yong; SHAO Tiequan; ZHU Zhixin; YU Bo; WANG Zhuo; ZHANG Wanqian; LI Rongxi

    2007-01-01

    The appearance of coelenterates marks the real beginning ofmetazoan evolution. It therefore has a prominent position in the origin and evolutionary history of organisms,and is also a pivotal question of evolutionary biology.Punctatus is an extinct, ancient marine animal from the early stage of the Cambrian explosion, occurring at. The lowermost Cambrian of both Kuanchuanpu (Ningqiang, Shaanxi) and Maidiping (Emei, Sichuan) areas. Punctatus has been studied for many years since the discovery of its fragments. System-atic and phylogenetic analysis has long been limited because of the rarity of complete specimens. In order to improve research into Punctatus, more than ten thousand globular fossils were recovered by means of "Chemistry Retting". On the basis of the study of these globular fossils, a series of Punctatus fossils with cone parts and finely preserved soft-tissue mouthparts and fossilized metazoan embryo were recovered. Through research on characteristics such as shape,modality and structure of these fossils symbiotic with Punctatus emeiensis, the author found many possible embryo fossils including the evidence of gastrula-stage animal fossils.The sequence of fetation might have appeared on the corol-liform oral region of Punctatus emeiensis. A study of the soft tissues, functional morphology and the sequence of embryo fossils shows evidence that Punctatus resembles coelenterate polyps in systematic classification. Perhaps it also represents an ancestor of the coelenterate with an original tentacle. A comparison with the real "tentacle animal" found in the Chengjiang Fauna, shows that the original tentacle is very tiny and its function range is limited. This reveals the primi-tive nature of the animal. Although the original tentacle is so small, it does exist, representing the first big step towards the real flexible tentacle with a strong function from the early evolving tentacle.

  14. Sediment Core Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides instrumentation and expertise for physical and geoacoustic characterization of marine sediments.DESCRIPTION: The multisensor core logger measures...

  15. Sediment Core Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides instrumentation and expertise for physical and geoacoustic characterization of marine sediments. DESCRIPTION: The multisensor core logger measures...

  16. Tracing euxinia by molybdenum concentrations in sediments using handheld X-ray fluorescence spectroscopy (HHXRF)

    DEFF Research Database (Denmark)

    Dahl, Tais W.; Ruhl, Micha; Hammarlund, Emma U.

    2013-01-01

    Elevated molybdenum (Mo) contents in organic-rich sediments are indicative of deposition from an anoxic and sulfide-rich (euxinic) water-column. This can be used for tracing past euxinic conditions in ancient oceans from sedimentary archives. Conventional analytical detection of elevated molybdenum...... with Mo: 47 ppm and NIST-2702 with Mo: 10 ppm) for analytical control. Analytical precision (1 sigma) after 30, 120, and 300 seconds of measuring time was 4, 2, and 1 ppm, with a respective detection limit of 11, 5, 3 ppm (3 sigma, noise level). The data were accurate to within the given precision (1...... sigma) after a daily calibration to samples covering a range of Mo concentrations from 0 to >30 ppm. Hand-held XRF equipment also allows Mo measurements directly on fresh rock surfaces, both in the field and under laboratory conditions. Rock-samples from a Cambrian drill core closely match ICPMS...

  17. Cambrian substrate revolution :from matgrounds to bioturbated mixgrounds%寒武纪底质革命:从微生物席底到生物扰动混合底

    Institute of Scientific and Technical Information of China (English)

    齐永安; 王敏; 李妲; 代明月

    2012-01-01

    前寒武纪生态系以微生物的繁盛为特征,以叠层石和微生物成因沉积构造的大量发育为标志.后生动物及其遗迹化石出现在新元古代“雪球事件”之后,并与微生物席组成“埃迪卡拉花园”.新元古代的海底以发育完好的微生物席底和微弱的垂向生物扰动为特征,沉积物含水量低、沉积物.水界面平滑稳定;到寒武纪,由于垂向生物扰动的大量增加,微生物席底逐渐衰弱,“显生宙式”的海底沉积物含水量高、上下层沉积物易于混合和悬浮、沉积物一水界面模糊.自寒武纪开始,随着后生动物活动在浅海环境中不断地增多,遗迹化石习性类型趋于多样化和复杂化,微生物席底开始向较深的陆架乃至深海迁移并逐渐消亡.%Precambrian ecosystems are characterized by the flourish of microbiota and wide occurrence of stro- matolites and microbially induced sedimentary structures. Metazoans and their trace fossils, occurong after the Neoproterozoic "Snowball Earth" event, made up of "The Garden of Ediacara" with microbial mats. Late Neoproterozoic seafloor were characterized by well-developed microbial mats and poor development of vertical- ly-oriented bioturbation, thus it provied a fairly stable, relatively low water content sediment surface With a sharp water-sediment interface. Microbially-bound seafloor became increasingly scarce in shallow-marine set- tings of Cambrian, largely due to evolution of burrowing organisms with an increasing vertically-oriented com- ponent to their bioturbation. This " Phanerozoic-style" seafloor had a blurry water-sediment interface, greater water content, and lacked well-developed microbial mats. With the reworking increase of metazoans in Cam- brian shallow marine settings, the trace fossils tended to be more diverse and complex, and microbial mat- grounds retreated to deep sea and gradually disappeared.

  18. Evidence For Diffusion Dominant Solute Transport In The Ordovician Sediments Of The Michigan Basin

    Science.gov (United States)

    Sykes, J. F.; Normani, S. D.; Yin, Y.

    2011-12-01

    A Deep Geologic Repository (DGR) for Low and Intermediate Level Radioactive Waste has been proposed by Ontario Power Generation for the Bruce site near Tiverton, Ontario, 225 km northwest of Toronto. The DGR concept envisions a repository excavated at a depth of 680 m within the low permeability (less than 10e-14 m/s) limestone Cobourg Formation beneath 200 m of Ordovician age shale. The attributes of the hydrogeologic environment for the DGR, and the potential for solute transport from a repository, were assessed using numerical models for hypothesis testing and numerical experiments. Data for the analyses included Westbay pressure measurements from the DGR site investigation boreholes. These data indicate that the Cambrian sandstone and the Niagaran Group in the Silurian are over-pressured relative to density corrected hydrostatic levels while the Ordovician limestone and shale are significantly under-pressured. The abnormal pressures provide evidence that solute transport in the low permeable Ordovician sediments is diffusion dominant. Sedimentary basins, when at hydrological equilibrium, normally show a near-hydrostatic pressure distribution. Under certain conditions, some excess pressure or pressure greater than hydrostatic can develop in low-permeability layers or other hydraulically isolated parts of systems. The processes commonly invoked to explain these over-pressures are compaction, hydrocarbon migration, diagenesis, tectonic stress or more simply topographic effects. Explanations of abnormal under-pressures include osmosis, exhumation, glaciation unloading, crustal flexure and the presence of a non-wetting gas phase in pores. A requirement of both abnormal over-pressures and under-pressures is low hydraulic conductivity in either the formation in which the abnormal pressures are observed, or in the overlying and underlying formations. Hydraulic conductivity estimates from straddle packer tests in the DGR boreholes confirm that the hydraulic

  19. Sediment supply to beaches

    DEFF Research Database (Denmark)

    Aagaard, Troels

    2014-01-01

    and this reduces confidence in predictions of long-term shoreline change. In this paper, field measurements of suspended sediment load and cross-shore transport on the lower shoreface are used to derive a model for sediment supply from the lower to the upper shoreface at large spatial and temporal scales. Data...

  20. δ13Ccarb and Ceanom excursions in the post-glacial Neoproterozoic and Early Cambrian interval in Guizhou,South China

    Institute of Scientific and Technical Information of China (English)

    FENG Hongzhen; LING Hongfei; JIANG Shaoyong; YANG Jinghong

    2004-01-01

    Secular δ 13Ccarb and Ceanom profiles in the post-glacial Neoproterozoic and Early Cambrian interval are reported from Guizhou on the southeasten border of the Yangtze platform, South China. Overall, the δ 13Ccarb profile drifts to negative values in the post-glacial Nantuo and lower to middle Doushantuo Formations, and then to positive values in the upper Doushantuo and Dengying Formations of Neoproterozoic, followed by negative values in the Lower Cambrian Gezhongwu and Niutitang Formations. A detailed investigation of the relationship between the δ 13Ccarb and Ceanom profiles reveals that the main anoxic and oxic episodes are coupled with negative and positive δ 13Ccarb values, respectively. This may suggest a control of alternation between ocean stratification and mixing on variations in 13C abundance in the ancient ocean of the investigated areas.

  1. The fossils of Orsten-type preservation from Middle and Upper Cambrian in Hunan,China-- Three-dimensionally preserved soft- bodied fossils (Arthropods)

    Institute of Scientific and Technical Information of China (English)

    DONG Xiping; Philip C. J Donoghue; LIU Zheng; LIU Jie; PENG Fan

    2005-01-01

    Exquisitely preserved three-dimensional soft- bodied fossils and typical Orsten-type preservation have been found from the strata of Middle and Late Cambrian in western Hunan, China. A preliminary description is provided for Hesslandona sp. (Phosphatocopida, Crustacea, Arthropoda) and Skara sp. (Skaracarida, Crustaceam, Arthropoda). The scientific significance of Orsten-type preservation and prospects for future work on these fossils from Hunan are outlined.

  2. Early Cambrian granitoids of North Gondwana margin in the transition from a convergent setting to intra-continental rifting (Ossa-Morena Zone, SW Iberia)

    Science.gov (United States)

    Sánchez-García, T.; Pereira, M. F.; Bellido, F.; Chichorro, M.; Silva, J. B.; Valverde-Vaquero, P.; Pin, Ch.; Solá, A. R.

    2014-07-01

    Two distinct Cambrian magmatic pulses are recognized in the Ossa-Morena Zone (SW Iberia): an early rift-(ER) and a main rift-related event. This Cambrian magmatism is related to intra-continental rifting of North Gondwana that is thought to have culminated in the opening of the Rheic Ocean in Lower Ordovician times. New data of whole-rock geochemistry (19 samples), Sm-Nd-Sr isotopes (4 samples) and ID-TIMS U-Pb zircon geochronology (1 sample) of the Early Cambrian ER plutonic rocks of the Ossa-Morena Zone are presented in this contribution. The ER granitoids (Barreiros, Barquete, Calera, Salvatierra de los Barros and Tablada granitoid Massifs) are mostly peraluminous granites. The Sm-Nd isotopic data show moderate negative ɛNdt values ranging from -3.5 to +0.1 and TDM ages greatly in excess of emplacement ages. Most ER granitoids are crustal melts. However, a subset of samples shows a transitional anorogenic alkaline tendency, together with more primitive isotopic signatures, documenting the participation of lower crust or mantle-derived sources and suggesting a local transient advanced stage of rifting. The Barreiros granitoid is intrusive into the Ediacaran basement of the Ossa-Morena Zone (Série Negra succession) and has yielded a crystallization age of 524.7 ± 0.8 Ma consistent with other ages of ER magmatic pulse. This age: (1) constrains the age of the metamorphism developed in the Ediacaran back-arc basins before the intrusion of granites and (2) defines the time of the transition from the Ediacaran convergent setting to the Lower Cambrian intra-continental rifting in North Gondwana.

  3. SIMS U-Pb zircon age of a tuff layer in the Meishucun section, Yunnan, southwest China: Constraint on the age of the Precambrian-Cambrian boundary

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Determination of the age of the Precambrian-Cambrian boundary is critical in understanding early evolution of life on Earth. SIMS U-Pb zircon analyses of the Bed 5 tuff layer of the Meishucun section were carried out closely following the guidance of cathodoluminescence images, and the majority of analyses were conducted on the oscillatory zircon grains. Thirteen measurements yield a highly reliable Concordia U-Pb age of 536.7 ± 3.9 Ma for the Bed 5 horizon. A grand mean of 206Pb/238U age of 535.2± 1.7 Ma (MSWD = 0.53) is calculated based on 13 concordant SIMS measurements of this study and 4 nano-SIMS measurements of Sawaki et al., which is the best estimate of the deposition age of the tuff layer within Bed 5 in the Meishucun section. This age has provided a robust age constraint on the significant Precambrian-Cambrian boundary strata in southern China, which independently suggested the placement of the Precambrian-Cambrian boundary at the bottom of the Xiaowaitoushan Member (Marker A).

  4. Evidence for an extensive Phanerozoic sediment cover on the Canadian and Fenno-Scandian shields

    Energy Technology Data Exchange (ETDEWEB)

    Laine, E.P.; Dickson, S.M.

    1985-01-01

    Examination of the age and diameter of 75 terrestrial meteorite impact craters taken from platform and shield regions throughout the world suggest that both the Canadian and Fenno-Scandian Shields were covered by a sedimentary blanket during a portion of the Phanerozoic. Subsequent erosion, fostered perhaps by a combination of glacial and tectonic processes, has exposed both of these shields to reveal an anomalous distribution of craters through time. The primary evidence for sedimentary cover and subsequent erosion is in the form of a 280 Myr gap in the record of craters less than 15 km in diameter. Small craters of Cambrian, Ordovician and Silurian age are found in shield regions, suggesting either a thin or non-existent sediment cover during this period. However, there is no record of small diameter craters on either shield of Devonian, Carboniferous, Permian, Triassic, or Jurassic age (400 to 120 Myr). This 280 Myr gap suggests that the shields were protected from smaller body impacts by a sedimentary cover. In contrast, the record of impacts on platform sediments implies no such hiatus in the infall of cosmic bodies to the earth's surface between the Devonian and the Early Cretaceous. Subsequent erosion, perhaps by Early Cretaceous time, exposed the shields to further bombardment. In addition, pre-Devonian craters became exhumed. Thus, the record of impact craters suggests that the Canadian and Fenno-Scandian Shields were covered by sediments while part of Pangaea.

  5. Provenance of sandstones from Caledonian nappes in Finnmark, Norway: Implications for Neoproterozoic-Cambrian palaeogeography

    Science.gov (United States)

    Zhang, W.; Roberts, D.; Pease, V.

    2016-11-01

    U-Pb detrital zircon age spectra from four formations in the Laksefjord and Kalak nappe complexes, Finnmark Caledonides, northern Norway, show peaks ranging from Neoarchaean through Late Palaeoproterozoic to Late Mesoproterozoic. Together with an extensive database of palaeocurrent flow measurements indicating derivation of the sediments from source regions to the S-SE on the Fennoscandian Shield, the successions in the lower thrust sheets of the Kalak Nappe Complex and the entire Laksefjord Nappe Complex are inferred to be of Baltican origin. These results are contrary to a previous suggestion that the sandstone-dominated Middle Allochthon is exotic to Baltica. The lithostratigraphical successions in these two nappe complexes show a south to north progression from alluvial-fan conglomerates through extensive fluvial to shallow-marine facies into deeper-marine turbiditic sequences. This pattern reflects the palaeogeographic transition from the shallow platform to deep-basinal oceanic development recorded along the c. 2000 km pre-Timanian passive margin of the northeastern Fennoscandian Shield.

  6. Offshore Surficial Sediment

    Data.gov (United States)

    California Department of Resources — This data layer (PAC_EXT.txt and PAC_PRS.txt) represents two of five point coverages of known sediment samples, inspections, and probes from the usSEABED data...

  7. Radiochronology of lake sediments

    Energy Technology Data Exchange (ETDEWEB)

    Erten, H.N. [Bilkent Univ., Ankara (Turkey). Dept. of Chemistry

    1997-01-01

    Sediment cores from Lakes Zurich, Constance, from the Sea of Marmara and from southern Turkey, northern Cyprus and eastern Spain were dated using natural {sup 210}Pb, fallout {sup 137}Cs and cosmic-ray produced {sup 7}Be radionuclides. Constant activity regions in the uppermost sections of sediments from Lake Zurich and the Sea of Marmara were attributed to post-depositional mobility of {sup 210}Pb in the former case and to bioturbation in the latter. A serious discrepancy exists between the {sup 210}Pb dating of Sea of Marmara sediments and those obtained by organic carbon based methods. The elements Zn, Cu, P and Pb were enriched in the upper sections of the sediment cores corresponding to the last 200 years. The increased metallurgical activities as a result of reforms in the Ottoman Army during the 18th century could be the most likely cause. (Author).

  8. Sediment Resuspension Data

    Data.gov (United States)

    U.S. Environmental Protection Agency — The full report on sediment resuspension in drinking water storage tanks and a link to an animation of results. This dataset is associated with the following...

  9. Rapid Sediment Characterization Tools

    Science.gov (United States)

    2008-09-01

    Organic (PAHs), inorganic (metals) Mobile field Lab or lab * Biomarkers (P450RGS dioxin screening assay) Dioxins , PAHs Lab Biological *cDNA...7 Immunoassays for PCBs, PAHs, Pesticides, and Dioxins ...9 P450RGS Dioxin Screening Assay for Sediment

  10. Geochemistry of sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.

    . Hydrothermal activity as revealed by sediment geochemistry in various studies such as fish debris from Red Sea recording hydrothermal activity; 2) episodic hydrothermal activity in Thetis Deep; 3) hydrothermal activity at Rodriguez Triple Junction were reviewed...

  11. Cell aggregation and sedimentation.

    Science.gov (United States)

    Davis, R H

    1995-01-01

    The aggregation of cells into clumps or flocs has been exploited for decades in such applications as biological wastewater treatment, beer brewing, antibiotic fermentation, and enhanced sedimentation to aid in cell recovery or retention. More recent research has included the use of cell aggregation and sedimentation to selectively separate subpopulations of cells. Potential biotechnological applications include overcoming contamination, maintaining plasmid-bearing cells in continuous fermentors, and selectively removing nonviable hybridoma cells from perfusion cultures.

  12. 地质名山馒头山及其附近早寒武世古地震沉积事件研究%Paleoseismic Depositional Events of the Famous Geological Mountain-Mantoushan and Its Vicinity in the Early Cambrian

    Institute of Scientific and Technical Information of China (English)

    张邦花; 田洪水; 张增奇; 杜圣贤

    2012-01-01

    蜚声中外的地质名山馒头山处在济南南部山区。通过野外调查和室内研究,从馒头山及其附近的青杨村东山、红叶谷、滚球山等地的下寒武统中,鉴别出了许多地震引起的同沉积变形构造(震积岩),主要有卷曲变形(震褶岩)、粒序微断层、滑移构造、滑塌褶曲、负载构造、枕状体、混插沉积、软硅质脉、软硅质层底辟构造、硅藻叠层石变形、沉陷构造、触变楔、布丁、震裂缝、震裂角砾岩及震碎角砾岩等。本文较详细地阐述了它们的特征和形成机理。触变楔属国内首次发现。触变楔和沉陷构造发育在夹软硅质层的白云岩中,其原始沉积物是含软硅质层的白云质灰泥。受强震触动,因软硅质沉积物(SiO2·nH2O)的粘度变小,软硅质层的粘度变小而变得更软,灰泥同时发生液化;在竖向震动力作用下,软硅质层被断开、继而沉陷形成了沉陷构造;沉陷构造向下延伸,结果使断开的硅质层汇聚,形成了触变楔。根据早寒武世古构造板块与地震带的分布,认为这些地震沉积遗迹是早寒武世板内地震记录,推测由古郯庐带的构造活动的响应。这些古地震事件记录的发现,丰富了济南南部山区、尤其是馒头山的地质科学内涵。%The well known geological mountain-Mantoushan is located in the The standard (stratotype) profile from the Longwangmiao Stage to the Zhangxia mountain area of southern Jinan city. Stage of the Lower middle Cambrian of the North China is established here. Here, geological traces are so rich and research history is so long that Mantoush- an mount is famous at home and abroad. The Jinan area lies in the west side of the Tanlu fault and seismic zone. Dur- ing the early Cambrian, a set of terrigenous clastic sediments consisted of sand and mud intercalated with carbonate were deposited in the western Shandong region including Jinan

  13. Exceptionally preserved Cambrian trilobite digestive system revealed in 3D by synchrotron-radiation X-ray tomographic microscopy.

    Directory of Open Access Journals (Sweden)

    Mats E Eriksson

    Full Text Available The Cambrian 'Orsten' fauna comprises exceptionally preserved and phosphatised microscopic arthropods. The external morphology of these fossils is well known, but their internal soft-tissue anatomy has remained virtually unknown. Here, we report the first non-biomineralised tissues from a juvenile polymerid trilobite, represented by digestive structures, glands, and connective strands harboured in a hypostome from the Swedish 'Orsten' fauna. Synchrotron-radiation X-ray tomographic microscopy enabled three-dimensional internal recordings at sub-micrometre resolution. The specimen provides the first unambiguous evidence for a J-shaped anterior gut and the presence of a crop with a constricted alimentary tract in the Trilobita. Moreover, the gut is Y-shaped in cross section, probably due to a collapsed lumen of that shape, another feature which has not previously been observed in trilobites. The combination of anatomical features suggests that the trilobite hypostome is functionally analogous to the labrum of euarthropods and that it was a sophisticated element closely integrated with the digestive system. This study also briefly addresses the preservational bias of the 'Orsten' fauna, particularly the near-absence of polymerid trilobites, and the taphonomy of the soft-tissue-harbouring hypostome.

  14. The earliest-known ancestors of Recent Priapulomorpha from the Early Cambrian Chengjiang Lagerst(``a)tte

    Institute of Scientific and Technical Information of China (English)

    HAN Jian; SHU Degan; ZHANG Zhifei; LIU Jianni

    2004-01-01

    The taxonomy of an early ancestor of Recent Priapulidae, Xiaoheiqingella peculiaris (= Yunnanpriapulus halteroformis Huang et al., 2004) from the Early Cambrian Chengjiang fossil LagerstStte, is revised. Morphological characters comprise a pair of caudal appendages rather than a single appendage flanking the trunk end and a possible urogenital duct found inside the preanal region. An additional extremely rare fossil priapulid worm, Paratubiluchus bicaudatus gen. nov., sp. nov. is also described herein. Its diagnostic characters are: an introvert bearing 25 longitudinal rows of scalids, a distinct neck region, no annulus on the oval trunk, and a pair of caudal appendages. The proportion of body parts is similar in size to that of loricate larvae of Recent priapulids and larva-formed Palaeopriapulitidae. Taking account of the features of Xiaoheiqingella, bicaudal appendages are considered to be a synapomorphy of Priapulidae and Tubiluchidae. Paratubiluchus gen. nov. is most likely a candidate for the ancestor of the Tubiluchidae; it probably originated from a larva-formed priapulid with 25 rows of scalids, thus representing an intermediate link between the priapulids in mature-form and the priapulids with Iorica.

  15. Characteristics of sulfur species and their implications in Lower Cambrian black shales from southern margin of Yangtze Platform

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    There are different sulfur forms in the black shales from theEarly Cambrian of the Yangtze platform. With its emphasis on pyrite and organosulfur, this paper discusses their distribution and formation. The research shows that sulfur phases take regular variations laterally as well as vertically in the research areas. In western researched profile with high terrigenous supply at the time it formed, there exists a larger amount of pyrite and less organosulfur, and pyrite amount declines while organosulfur content increases upwards along the profile. This black shale profile is characterized by relatively light sulfur isotope composition with evolution trend of becoming heavier both for pyrite and organosulfur from bottom to top along the profile. Opposite situation occurs in eastern profiles which were located farther away from terrigenous land. Here pyrite amount obviously decreases and organic matter has combined more sulfur, although these two kinds of sulfur species take similar trend in content variation along profiles to that for western profile. At the same time more 34S is accumulated in sulfur species of black shale samples from eastern profile, and sulfur isotope composition gradually turns lighter from bottom to top. In combination with other information of iron, organic carbon contents and petrographic features, it can be established that sea-level change, supply of terrigenous matters, tectonic background and natures of paleoceanic chemistry have exerted great influence on the distribution of sulfur species in these black shales.

  16. Suspected microbial-induced sedimentary structures (MISS) in Furongian (Upper Cambrian; Jiangshanian, Sunwaptan) strata of the Upper Mississippi Valley

    Science.gov (United States)

    Eoff, Jennifer D.

    2014-01-01

    The Furongian (Upper Cambrian; Jiangshanian and Sunwaptan) Tunnel City Group (Lone Rock Formation and Mazomanie Formation), exposed in Wisconsin and Minnesota, represents a shallow-marine clastic environment during a time of exceptionally high sea level. Lithofacies from shoreface to transitional-offshore settings document deposition in a wave- and storm-dominated sea. Flooding of the cratonic interior was associated with formation of a condensed section and the extensive development of microbial mats. Biolamination, mat fragments, wrinkle structures, and syneresis cracks are preserved in various sandstone facies of the Lone Rock Formation, as is evidence for the cohesive behavior of sand. These microbial-induced sedimentary structures (MISS) provide unique signals of biological–physical processes that physical structures alone cannot mimic. The MISS are associated with a trilobite extinction event in the Steptoean–Sunwaptan boundary interval. This may support recent claims that Phanerozoic microbial mats were opportunistic disaster forms that flourished during periods of faunal turnover. Further investigation of stratigraphic, taphonomic, and other potential biases, however, is needed to fully test this hypothesis.

  17. Geodynamic setting and geochemical signatures of Cambrian?Ordovician rift-related igneous rocks (Ossa-Morena Zone, SW Iberia)

    Science.gov (United States)

    Sánchez-García, T.; Bellido, F.; Quesada, C.

    2003-04-01

    An important rifting event, accompanied by massive igneous activity, is recorded in the Ossa-Morena Zone of the SW Iberian Massif (European Variscan Orogen). It likely culminated in the formation of a new oceanic basin (Rheic ocean?), remnants of which appear presently accreted at the southern margin of the Ossa-Morena Zone. Rifting propagated diachronously across the zone from the Early Cambrian to the Late Ordovician, but by Early Ordovician time, the existence of a significant tract of new ocean is evidenced by a breakup unconformity. Although early stages of rifting were not accompanied by mantle-derived igneous activity, a pronounced increase of the geothermal gradient is indicated by partial melting of metasedimentary protoliths in the upper and middle crust, and by coeval core-complex formation. Geochemistry of the main volume of igneous rocks, emplaced some million years later during more mature stages of rifting, suggests an origin in a variably enriched asthenospheric source, similar to that of many OIB, from which subsequent petrogenetic processes produced a wide range of compositions, from basalt to rhyolite. A tectonic model involving collision with, and subsequent overriding of, a MOR is proposed to account for the overall evolution, a present-day analogue for which lies in the overriding of the East Pacific Rise by North America and the rifting of Baja California.

  18. Halomonas sulfidaeris-dominated microbial community inhabits a 1.8 km-deep subsurface Cambrian Sandstone reservoir.

    Science.gov (United States)

    Dong, Yiran; Kumar, Charu Gupta; Chia, Nicholas; Kim, Pan-Jun; Miller, Philip A; Price, Nathan D; Cann, Isaac K O; Flynn, Theodore M; Sanford, Robert A; Krapac, Ivan G; Locke, Randall A; Hong, Pei-Ying; Tamaki, Hideyuki; Liu, Wen-Tso; Mackie, Roderick I; Hernandez, Alvaro G; Wright, Chris L; Mikel, Mark A; Walker, Jared L; Sivaguru, Mayandi; Fried, Glenn; Yannarell, Anthony C; Fouke, Bruce W

    2014-06-01

    A low-diversity microbial community, dominated by the γ-proteobacterium Halomonas sulfidaeris, was detected in samples of warm saline formation porewater collected from the Cambrian Mt. Simon Sandstone in the Illinois Basin of the North American Midcontinent (1.8 km/5872 ft burial depth, 50°C, pH 8, 181 bars pressure). These highly porous and permeable quartz arenite sandstones are directly analogous to reservoirs around the world targeted for large-scale hydrocarbon extraction, as well as subsurface gas and carbon storage. A new downhole low-contamination subsurface sampling probe was used to collect in situ formation water samples for microbial environmental metagenomic analyses. Multiple lines of evidence suggest that this H. sulfidaeris-dominated subsurface microbial community is indigenous and not derived from drilling mud microbial contamination. Data to support this includes V1-V3 pyrosequencing of formation water and drilling mud, as well as comparison with previously published microbial analyses of drilling muds in other sites. Metabolic pathway reconstruction, constrained by the geology, geochemistry and present-day environmental conditions of the Mt. Simon Sandstone, implies that H. sulfidaeris-dominated subsurface microbial community may utilize iron and nitrogen metabolisms and extensively recycle indigenous nutrients and substrates. The presence of aromatic compound metabolic pathways suggests this microbial community can readily adapt to and survive subsurface hydrocarbon migration.

  19. Morphology and function in the Cambrian Burgess Shale megacheiran arthropod Leanchoilia superlata and the application of a descriptive matrix

    Directory of Open Access Journals (Sweden)

    Haug Joachim T

    2012-08-01

    Full Text Available Abstract Background Leanchoilia superlata is one of the best known arthropods from the middle Cambrian Burgess Shale of British Columbia. Here we re-describe the morphology of L. superlata and discuss its possible autecology. The re-description follows a standardized scheme, the descriptive matrix approach, designed to provide a template for descriptions of other megacheiran species. Results Our findings differ in several respects from previous interpretations. Examples include a more slender body; a possible hypostome; a small specialised second appendage, bringing the number of pairs of head appendages to four; a further sub-division of the great appendage, making it more similar to that of other megacheirans; and a complex joint of the exopod reflecting the arthropod’s swimming capabilities. Conclusions Different aspects of the morphology, for example, the morphology of the great appendage and the presence of a basipod with strong median armature on the biramous appendages indicate that L. superlata was an active and agile necto-benthic predator (not a scavenger or deposit feeder as previously interpreted.

  20. First Ediacaran Fauna Occurrence in Northeastern Brazil (Jaibaras Basin, ?Ediacaran-Cambrian: Preliminary Results and Regional Correlation

    Directory of Open Access Journals (Sweden)

    FRANCISCO R.G. BARROSO

    2014-09-01

    Full Text Available This study reports the first known occurrence of the Ediacaran fauna in northeastern Brazil (at Pacujá Municipality, northwestern state of Ceará and presents preliminary interpretations of its significance. Regional correlation indicates that the fossils originated in the Jaibaras Basin and that they may represent a new geological system. The depositional environment can be attributed to a fluviomarine system. Nine Ediacaran species can be identified, including members of pandemic groups (e.g., Charniodiscus arboreus Glaessner, 1959; ?Charniodiscus concentricus Ford, 1958; Cyclomedusa davidi Sprigg, 1947; Ediacaria flindersi Sprigg, 1947; and Medusinites asteroides Sprigg, 1949 and endemic groups (e.g., Kimberella quadrata Glaessner & Wade, 1966; Palaeophragmodictya reticulata Gehling & Rigby, 1996; Parvancorina minchami Glaessner, 1958; and Pectinifrons abyssalis Bamforth, Narbonne, Anderson, 2008. Three ichnogenera are also present: Arenicolites Salter, 1857; Palaeophycus Hall, 1987; and Planolites Nicholson, 1873. The relative age of the deposits is between ?Ediacaran and Cambrian, and the fauna resembles the White Sea Assemblage. The bioturbation presents typical unbranched Ediacaran ichnogenera with little depth in the substrate. This previously unknown occurrence of the Ediacaran fauna reinforces the importance of the state of Ceará to Brazilian and global palaeontology.

  1. New observations of the lobopod-like worm Facivermis from the Early Cambrian Chengjiang Lagerst(a)tte

    Institute of Scientific and Technical Information of China (English)

    LIU Jianni; HAN Jian; SIMONETTA A. M.; HU Shixue; ZHANG Zhifei; YAO Yang; SHU Degan

    2006-01-01

    Facivermis yunnanicus (Hou & Chen, 1989), from the Early Cambrian Chengjiang Lagerst(a)tte, a worm-like fossil with 5 pairs of tentacles and a perceived shrunken end, has been regarded as related to polychaetes, later it has been variously interpreted as lobopods, Pentastoma and lophophorates. Newly discovered complete specimens by the ELI field team show that the taxon has, in addition to the 5 pairs of appendages, a pear-shaped trunk end bearing two or three circles of hooks. Accordingly, based on these important morphological characters, reconsideration of its affinities is provided and the taxonomy is remedied herein. Because the five pairs of appendages of Facivermis yunnanicus resemble the appendages of the fore-trunk of lobopod Miraluolishania (Liu & Shu, 2004), it seems that they are homologous structures. Therefore, the affinities of Facivermis are regarded here as being close to the lobopods, in addition, the lobe-like appendages of Facivermis are very crucial to exploring the origin of the appendages of lobopods and arthropods.

  2. The internal structure of Early Cambrian fossil embryo Olivooides revealed in the light of Synchrotron X-ray Tomographic Microscopy

    Institute of Scientific and Technical Information of China (English)

    CHEN Fang; DONG XiPing

    2008-01-01

    Countless fossil embryo Olivooides and the hatched larvae, juveniles and adults (the latter two kinds are Punctatus) are recovered by means of acid maceration from the fine-crystalline to medium-crystalline phosphatic limestone and phosphatic micrite of Early Cambrian Kuanchuanpu Formation at the Shizhonggou section, near Kuanchuanpu Village, Ningqiang County, Shaanxi Province, China. Using the technique of Synchrotron X-ray Tomographic Microscopy, the 3D internal structure of Olivooides and Punctatus is reconstructed. The morphological and statistic analyses are also given to the stellae structure of Olivooides and Punctatus, which indicates that this structure is a result of adaptive evolution to a lifestyle of fast-attaching after hatching, probably with the function of mucilage secretion. The internal structure of Punctatus is described and discussed. The ovum-like structure, a common internal feature of Punctatus, is considered as the taphonomic structure, rather than eggs or other biological structure. This structure is thought to be formed after the burial of the animal and before or during the mineralization. The original internal structure of Punctatus is assumed to be tabulae-filled, with soft body grown on them.

  3. Carbonate Platform Margin Slope Characteristics of Cambrian Chefu Age in Baojing-Fenghuang and Adjacent Areas, Western Hunan, China

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The Cambrian paleogeography in south China can be divided into Yangtze platform, platform margin slope (including upper slope and lower slope) and basin. The carbonate gravity deposits are well developed there, particularly in the Yangtze platform adjacent areas. This paper mainly deals with declivity fan characters of the Chefu age in Fenghuang adjacent areas, western Hunan Province. According to their distribution and thickness, three main declivity fans have been divided in the study areas,namely, Dama ( ∈ c-dsf), Machong ( ∈ c-msf) and Huangheyuan ( ∈ c-hsf) declivity fans. Each fan's characters are described in detail in this paper. Based on their distribution range, scale and fossiliferous layers, two peak periods (fair developmental period) are distinguished: (1) Linguagnostus reconditus Zone (time), and (2) Glyptagnostus reticulatus Zone (time). They were characterized by huge thick limestone breccia layers (single layer 3-4 rn thick) and closely spaced spread. Besides, there are also two developmental periods: (1) Lejopyge laevigata- Proagnostus bulbus Zone (time), and (2) Agnostus inexpectans-Proceratopyge protracta Zone (time) to Erixanium Zone (time) to Corynexochus plumula-Sinoproceratopyge cf. kiangshanensis Zone (time), while Glyptagnostus stolidotus Zone (time) was an interstitial period (without or rare limestone breccias). All these features may verify the relative movement of the earth crust and paleoclimate variety of the Chefu age in the study areas.

  4. Isotopic evidence for glacial meltwater recharge to the Cambrian-Ordovician aquifer, north-central United States

    Science.gov (United States)

    Siegel, D.I.; Mandle, R.J.

    1984-01-01

    The chemistry of water in the Cambrian-Ordovician aquifer in six midwestern states has been studied as part of the Northern Midwest Regional Aquifer-System Analysis of the U.S. Geological Survey. Dissolved-solids concentrations generally increase perpendicular to the direction of regional groundwater flow, from less than 400 mg/liter in southeast Minnesota, southwest Wisconsin, and northeast Iowa to more than 10,000 mg/liter in northwest Missouri. Isotopic ratios of hydrogen and oxygen are significantly depleted from north to south, with an areal distribution approximately parallel to the distribution of dissolved solids. For example, ??18O in southern Iowa and northern Missouri is about 6 parts per thousand lighter than ??18O of modern recharge water in Minnesota and Wisconsin. Covariance between ??18O and ??D of the groundwater, similar to that of modern precipitation, suggests that the differences in isotopic ratios between groundwater and modern recharge water reflect meteoric signatures of water during past recharge events rather than geochemical processes such as isotopic exchange with aquifer materials. The pronounced parallelism between the distribution of isotopes and dissolved solids over large areas probably reflects largescale recharge of Pleistocene glacial meltwater into the aquifer system, which probably had a paleoflow system with a gradient from northeast to southwest rather than from northwest to southeast. ?? 1984.

  5. Hydrodynamics of sediment threshold

    Science.gov (United States)

    Ali, Sk Zeeshan; Dey, Subhasish

    2016-07-01

    A novel hydrodynamic model for the threshold of cohesionless sediment particle motion under a steady unidirectional streamflow is presented. The hydrodynamic forces (drag and lift) acting on a solitary sediment particle resting over a closely packed bed formed by the identical sediment particles are the primary motivating forces. The drag force comprises of the form drag and form induced drag. The lift force includes the Saffman lift, Magnus lift, centrifugal lift, and turbulent lift. The points of action of the force system are appropriately obtained, for the first time, from the basics of micro-mechanics. The sediment threshold is envisioned as the rolling mode, which is the plausible mode to initiate a particle motion on the bed. The moment balance of the force system on the solitary particle about the pivoting point of rolling yields the governing equation. The conditions of sediment threshold under the hydraulically smooth, transitional, and rough flow regimes are examined. The effects of velocity fluctuations are addressed by applying the statistical theory of turbulence. This study shows that for a hindrance coefficient of 0.3, the threshold curve (threshold Shields parameter versus shear Reynolds number) has an excellent agreement with the experimental data of uniform sediments. However, most of the experimental data are bounded by the upper and lower limiting threshold curves, corresponding to the hindrance coefficients of 0.2 and 0.4, respectively. The threshold curve of this study is compared with those of previous researchers. The present model also agrees satisfactorily with the experimental data of nonuniform sediments.

  6. Sedimentation of Knotted Polymers

    CERN Document Server

    Piili, Joonas; Kaski, Kimmo; Linna, Riku

    2012-01-01

    We investigate the sedimentation of knotted polymers by means of the stochastic rotation dynamics, a molecular dynamics algorithm which takes hydrodynamics fully into account. We show that the sedimentation coefficient s, related to the terminal velocity of the knotted polymers, increases linearly with the average crossing number n_c of the corresponding ideal knot. To the best of our knowledge, this provides the first direct computational confirmation of this relation, postulated on the basis of experiments in "The effect of ionic conditions on the conformations of supercoiled DNA. I. sedimentation analysis" by Rybenkov et al., for the case of sedimentation. Such a relation was previously shown to hold with simulations for knot electrophoresis. We also show that there is an accurate linear dependence of s on the inverse of the radius of gyration R_g^-1, more specifically with the inverse of the R_g component that is perpendicular to the direction along which the polymer sediments. Intriguingly, the linear de...

  7. An arthropod cis-regulatory element functioning in sensory organ precursor development dates back to the Cambrian

    Directory of Open Access Journals (Sweden)

    Simpson Pat

    2010-09-01

    Full Text Available Abstract Background An increasing number of publications demonstrate conservation of function of cis-regulatory elements without sequence similarity. In invertebrates such functional conservation has only been shown for closely related species. Here we demonstrate the existence of an ancient arthropod regulatory element that functions during the selection of neural precursors. The activity of genes of the achaete-scute (ac-sc family endows cells with neural potential. An essential, conserved characteristic of proneural genes is their ability to restrict their own activity to single or a small number of progenitor cells from their initially broad domains of expression. This is achieved through a process called lateral inhibition. A regulatory element, the sensory organ precursor enhancer (SOPE, is required for this process. First identified in Drosophila, the SOPE contains discrete binding sites for four regulatory factors. The SOPE of the Drosophila asense gene is situated in the 5' UTR. Results Through a manual comparison of consensus binding site sequences we have been able to identify a SOPE in UTR sequences of asense-like genes in species belonging to all four arthropod groups (Crustacea, Myriapoda, Chelicerata and Insecta. The SOPEs of the spider Cupiennius salei and the insect Tribolium castaneum are shown to be functional in transgenic Drosophila. This would place the origin of this regulatory sequence as far back as the last common ancestor of the Arthropoda, that is, in the Cambrian, 550 million years ago. Conclusions The SOPE is not detectable by inter-specific sequence comparison, raising the possibility that other ancient regulatory modules in invertebrates might have escaped detection.

  8. The origin of increased salinity in the Cambrian-Vendian aquifer system on the Kopli Peninsula, northern Estonia

    Science.gov (United States)

    Karro, Enn; Marandi, Andres; Vaikmäe, Rein

    Monitoring of the confined Cambrian-Vendian aquifer system utilised for industrial water supply at Kopli Peninsula in Tallinn over 24 years reveals remarkable changes in chemical composition of groundwater. A relatively fast 1.5 to 3.0-fold increase in TDS and in concentrations of major ions in ed groundwater is the consequence of heavy pumping. The main sources of dissolved load in Cambrian-Vendian groundwater are the leaching of host rock and the other geochemical processes that occur in the saturated zone. Underlying crystalline basement, which comprises saline groundwater in its upper weathered and fissured portion, and which is hydraulically connected with the overlying Cambrian-Vendian aquifer system, is the second important source of ions. The fractured basement and its clayey weathering crust host the Ca-Cl type groundwater, which is characterised by high TDS values (2-20 g/L). Intensive water ion accelerates the exchange of groundwaters and increases the area of influence of pumping. Chemical and isotopic studies of groundwater indicate an increasing contribution of old brackish water from the crystalline basement and rule out the potential implication of an intrusion of seawater into aquifer. L'origine de la salinité croissante dans le système aquifère du Cambrien-Vendien dans la péninsule de Kopli, nord de l'Estonie Le suivi à long terme du système aquifère captif du Cambrien-Vendien utilisé pour l'approvisionnement d'eaux industrielles dans la Péninsule de Kopli, nord de l'Estonie, révèle de remarquables changements dans la composition chimique des eaux souterraines. Une augmentation de facteur 1.5 à 3 de la TDS et des concentrations en ions majeurs dans l'eau souterraine est la conséquence de pompages intensifs. Les sources principales des charges dissoutes dans les eaux de l'aquifère du Cambrien-Vendien sont le lessivage des roches et d'autres phénomènes géochimiques ayant lieu dans la zone saturée. Le soubassement rocheux cristallin

  9. Cambrian rift-related magmatism in the Ossa-Morena Zone (Iberian Massif): Geochemical and geophysical evidence of Gondwana break-up

    Science.gov (United States)

    Sarrionandia, F.; Carracedo Sánchez, M.; Eguiluz, L.; Ábalos, B.; Rodríguez, J.; Pin, C.; Gil Ibarguchi, J. I.

    2012-10-01

    Volcanic rocks of Cambrian age from Zafra (Ossa-Morena Zone, Iberian Massif) are the result of rift processes that affected Cadomian arc units accreted to the NW edge of Gondwana during the Neoproterozoic-Early Cambrian transition. Tephrite to rhyolite volcanics define an alkaline transitional association (Coombs type). Basic-ultrabasic rocks exhibit typical alkaline REE-patterns, strongly enriched in LREE with respect to HREE. Two parental magmas are identified, one with a mantle signature, lack of Nb negative anomaly and εNd500Ma + 3.8 to + 4.2; another with crustal contribution, minor Nb negative anomaly and εNd500Ma + 0.8 to + 1.8. Intermediate-acid rocks show variable REE fractionation and share geochemical characteristics of both basic-ultrabasic groups with restricted εNd500Ma + 2.2 to 3.1 and general absence of Nb negative anomaly. Basic-ultrabasic melts resulted from different amounts of partial melting of a homogeneous source and segregation at the garnet-spinel transition zone. We argue that the "Hales transition" recently recognized in reflection seismic experiments of SW Iberia might image such a source region. Mantle-derived magmas ponded at the base of the crust and weakly interacted with crustal rocks/melts, whilst intermediate-acid rocks were generated by plagioclase ± clinopyroxene ± amphibole fractionation. Melt ascent took place through fractures, with limited crustal interaction. Based upon the new geochemical results and complementary cartographic and geophysical data, a model is presented for the Cambrian break-up of North Gondwana due to magma ascent from the mantle.

  10. Evaluating the primary and/or diagenetic origin of rare earth element abundances in Ediacaran to early Cambrian phosphate deposits, Yangtze Platform (South China) by LA-ICPMS

    Science.gov (United States)

    Hippler, Dorothee; Klügel, Andreas; Biedermann, Nicole; Guo, Qingjun; Franz, Gerhard

    2014-05-01

    The Precambrian-Cambrian time interval represents one of the greatest phosphogenic episodes in Earth's history with giant and well-preserved phosphate deposits occurring on the Yangtze Platform in South China. We investigated concentrations of rare earth elements (REE) and yttrium of shallow and deep-water sedimentary phosphate deposits of the Ediacaran Doushantou Formation and the early Cambrian Zhongyicun Formation by using LA-ICP mass spectrometry. The aim is to examine the temporal and spatial variability of seawater chemistry in conjunction with the conditions of phosphate formation and the evaluation of the extent of diagenetic modification. The mineralogical and textural composition of the samples was pre-screened using SEM and XRD, and polished thick sections were prepared for subsequent high-resolution LA-ICPMS analyses. Overall concentrations in REE range between 18 and 657 ppm, with elevated concentrations (> 200 ppm) in apatite from the deep-water phosphate deposits. REE+Y patterns of shallow-water phosphate deposits exhibit the evolution from flat shale-like to gently inclined seawater-derived patterns, with the early Cambrian phosphate deposits revealing distinct negative Ce- and positive Y-anomalies indicative for oxygenated surface waters. REE+Y patterns of phosphate deposits of the deep-water facies are flat to highly enriched in MREE, which is manifested in variably pronounced concave-down patterns. In detail, these patterns display different Ce-anomalies, as well as small positive Eu-anomalies. We propose that REE+Y patterns of Ediacaran and early Cambrian sedimentary phosphate deposits can inherit both primary and secondary signatures reflecting either seawater composition or diagenetic modification and fluid flow. The combination of imaging techniques and in-situ LA-ICPMS thereby enables a more sophisticated examination of the potential sources and processes than whole rock determinations. Placing the results in stratigraphic order and assuming

  11. SEDIMENT CONTROL FOR IRRIGATION INTAKES

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The analysis of the sediment problems in irrigation engineeringwas carried out, and the layout, the method as well as the effect of sediment control for irrigation intake structures in China were briefly introduced.

  12. Electrodialytic remediation of sediments

    DEFF Research Database (Denmark)

    Jensen, Pernille Erland

    , in many cases, prohibit this due to contamination by primarily heavy metals and TBT. Similarly, sediments of fresh waters could potentially be used as soil amendment material for poor agricultural soils utilizing their often high content of phosphate and nitrogen. However, again, heavy metal contamination...

  13. Dynamics of Cohesive Sediments

    DEFF Research Database (Denmark)

    Johansen, Claus

    to the erosion, deposition, settling velocity and consolidation of cohesive sediments. All experiments were evaluated considering the reproducibility of the individual experiments. The erosion and deposition experiments were conducted in a circular flume. The measurements of the settling velocity were carried...

  14. Cable Bacteria in Freshwater Sediments

    OpenAIRE

    Risgaard-Petersen, Nils; Kristiansen, Michael; Frederiksen, Rasmus B.; Dittmer, Anders Lindequist; Bjerg, Jesper Tataru; Trojan, Daniela; Schreiber, Lars; Damgaard, Lars Riis; Schramm, Andreas; Nielsen, Lars Peter

    2015-01-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the fre...

  15. Deep-water sediment bypass

    NARCIS (Netherlands)

    Stevenson, Christopher J.; Jackson, Christopher A L; Hodgson, David M.; Hubbard, Stephen M.; Eggenhuisen, Joris T.

    2015-01-01

    Submarine gravity flows are a key process for transporting large volumes of sediment from the continents to the deep sea. The location, volume, and character of the sediment bypassed by these flows dictates the areal extent and thickness of the associated deposits. Despite its importance, sediment b

  16. Sediment problems in reservoirs. Control of sediment deposits

    Energy Technology Data Exchange (ETDEWEB)

    Jacobsen, Tom

    1997-12-31

    When a reservoir is formed on a river, sediment will deposit in the reservoir. Such processes are unfortunate, for instance, for the implementation of hydroelectric energy. This thesis studies the problem of reservoir sedimentation and discusses methods of removing the sediments. Various aspects of reservoir sedimentation are discussed. Anthropogenic impacts seem to greatly affect the erosion processes. Temporal distribution is uneven, mainly because of the very large flood events. A world map showing the Reservoir Capacity: Annual Sediment Inflow ratio for reservoirs with volume equal to 10% of annual inflow has been prepared. The map shows that sedimentation is severe in the western parts of North and South America, eastern, southern and northern Africa, parts of Australia and most of Asia. The development of medium-sized reservoirs is difficult, as they are too large for conventional flushing technique and too small to store the sediment that accumulates during their economic lifetime. A computer model, SSIIM, was used with good results in a case study of two flood drawdown trials in Lake Roxburg, New Zealand. Two techniques have been developed that permits controlled suction of sediment and water into a pipe: the Slotted Pipe Sediment Sluicer (SPSS) and the Saxophone Sediment Sluicer (SSS). The techniques exploit the inflow pattern in through a slot in a pipe. An equation describing this inflow pattern was derived and verified experimentally. The SPSS is fixed near the reservoir bed, and sediment that deposits on top of it is removed in the sluicing process. The SSS sluices sediment from the surface of the sediment deposits. Some technical and economic conditions affecting the economics of sediment removal from reservoirs have been identified and studied. 79 refs., 112 figs., 14 tabs.

  17. Paleomagnetism of the Late Proterozoic Sierras Bayas Group and the Ediacaran-Cambrian Apparent Polar Wander Path of the Rio de la Plata Craton

    Science.gov (United States)

    Rapalini, A. E.; Trindade, R. I.; Poiré, D. G.; Vieira, L.

    2007-05-01

    The apparent polar wander path (APWP) of the Rio de la Plata craton (RP) for the Late Proterozoic and Early Paleozoic is of significance to reconstruct the tectonic processes that led to the amalgamation of Gondwana. In order to define the Ediacaran-Cambrian APWP for RP, a systematic paleomagnetic study was carried out in the Sierras Bayas Group exposed in the province of Buenos Aires, Argentina. 328 samples from 44 sites were collected in the Cryogenian to Ediacaran Villa Mónica Fm., the Ediacaran Cerro Largo, Loma Negra and Las Aguilas Fms. and the Cambrian (?) Cerro Negro Fm. Sampling included mainly limestone and dolomite, red claystone and marls. Although most sites presented secondary magnetizations of likely recent and Permian (?) age, a few sites from the Cerro Largo and uppermost Villa Mónica Fms. carry a pre-tectonic magnetization that yielded a preliminary paleomagnetic pole at 34.6°S, 211.3° (6.4°/10-9°; n: 18 samples), while a pre-tectonic remanence from the Cerro Negro Fm. yielded a paleomagnetic pole at 10.9°N, 323.5°E (9.7°/13.3°, n:17 samples). These two preliminary paleomagnetic poles for the Sierras Bayas Group together with previously published ones permit to define with confidence the APWP of RP from ca. 600 to ca. 500 Ma.

  18. Paleogeographic and tectonic implications of the first paleomagnetic results from the Middle Late Cambrian Mesón Group: NW Argentina

    Science.gov (United States)

    Spagnuolo, Cecilia M.; Rapalini, Augusto E.; Astini, Ricardo A.

    2008-02-01

    The first paleomagnetic data from autochthonous Cambrian rocks in NW Argentina is reported to constrain the apparent polar wander path (APWP) of Gondwana during the Early Paleozoic. The paleomagnetic pole (Lat 4.5°S; Long 359.0°E; dp = 5.5; dm = 8.8; n = 26) was obtained from the red to purple sandstones of the Campanario Formation. These rocks present a characteristic remanence carried by fine-grained hematite. The pole indicates that during the Late Cambrian, rocks now exposed in the Eastern Cordillera of NW Argentina were deposited at relatively low latitudes (≈26°S), consistent with intense chemical alteration during wet and warm climates, as indicated from petrography of apparent first-cycle quarzites of the Mesón Group. However, the pole position is anomalous with respect to the most accepted apparent polar wander paths for Gondwana, suggesting that the study area (22°50'S, 65°00'W) underwent clockwise rotation of 38° ± 8°, likely related to the Cenozoic central Andes rotation pattern characteristic of the region.

  19. Proposed stratotype for the base of the highest Cambrian stage at the first appearance datum of Cordylodus andresi, Lawson Cove section, Utah, USA

    Science.gov (United States)

    Miller, J.F.; Ethington, Raymond L.; Evans, K.R.; Holmer, L.E.; Loch, James D.; Popov, L.E.; Repetski, J.E.; Ripperdan, R.L.; Taylor, John F.

    2006-01-01

    We propose a candidate for the Global Standard Stratotype-section and Point (GSSP) for the base of the highest stage of the Furongian Series of the Cambrian System. The section is at Lawson Cove in the Ibex area of Millard County, Utah, USA. The marker horizon is the first appearance datum (FAD) of the conodont Cordylodus andresi Viira et Sergeyeva in Kaljo et al. [Kaljo, D., Borovko, N., Heinsalu, H., Khazanovich, K., Mens, K., Popov, L., Sergeyeva, S., Sobolevskaya, R., Viira, V., 1986. The Cambrian-Ordovician boundary in the Baltic-Ladoga clint area (North Estonia and Leningrad Region, USSR). Eesti NSV Teaduste Akadeemia Toimetised. Geologia 35, 97-108]. At this section and elsewhere this horizon also is the FAD of the trilobite Eurekia apopsis (Winston et Nicholls, 1967). This conodont characterizes the base of the Cordylodus proavus Zone, which has been recognized in many parts of the world. This trilobite characterizes the base of the Eurekia apopsis Zone, which has been recognized in many parts of North America. The proposed boundary is 46.7 m above the base of the Lava Dam Member of the Notch Peak Formation at the Lawson Cove section. Brachiopods, sequence stratigraphy, and carbon-isotope geochemistry are other tools that characterize this horizon and allow it to be recognized in other areas. ?? 2006 Nanjing Institute of Geology and Palaeontology, CAS.

  20. Phosphatized rare star-like mouth disc of Punctatus and its functional morphology from the earliest Cambrian of the South Shaanxi China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Meishucun stage is the prelude in decipher-ing the Cambrian Explosion. In this prominent stage, rapid radioactive evolution and body-plan innovation have taken place and different associations of organism have been shaped. In this paper we report several 3D-preserved rare star-like fossils with finely preserved soft tissues which were recovered from the Kuanchuanpu Member of the Dengying Formation in South Shaanxi, China in 2003. By studying on functional morphology and analogy with mouthpart of Punctatus, there are evidences that this star-like organism approaches the coelenterates in systematic classification and the centre of star-like organism is its mouth. The appearance of coelenterates marks the real beginning of metazoan evolution. Therefore, it has the prominent position in the origin and evolutionary history of organisms. Perhaps the star-like organism represents the early types of coelenterate with original tentacles. These new materials provide new evidence for the origin, evolution and the functional evolution of the metazoan during the early stage of the Cambrian Explosion.

  1. An Ediacaran–Cambrian thermal imprint in Rajasthan, western India: Evidence from 40Ar-39Ar geochronology of the Sindreth volcanics

    Indian Academy of Sciences (India)

    Archisman Sen; Kanchan Pande; Hetu C Sheth; Kamal Kant Sharma; Shraboni Sarkar; A M Dayal; Harish Mistry

    2013-12-01

    The Sindreth Group exposed near Sirohi in southern Rajasthan, western India, is a volcanosedimentary sequence. Zircons from Sindreth rhyolite lavas and tuffs have yielded U–Pb crystallization ages of ∼768–761 Ma, suggesting that the Sindreth Group is a part of the Malani magmatic event. Earlier 40Ar-39Ar studies of other Malani volcanic and plutonic rocks yielded disturbed argon release spectra, ascribed to a ∼550 Ma thermal event possibly related to the Pan-African orogeny. To test and confirm this possibility, we dated two whole-rock and three feldspar separate samples of the Sindreth volcanics by the 40Ar-39Ar method. All samples yield disturbed argon release spectra suggesting radiogenic argon loss and with plateau segments at 550 Ma or 490 Ma. We interpret these as events of argon loss at 550–490 Ma related to an Ediacaran–Cambrian thermal event, possibly related to the Malagasy orogeny. The combined older and new 40Ar-39Ar results are significant in showing that whereas Ediacaran–Cambrian magmatic and metamorphic events are well known from many parts of India, they left thermal imprints in much of Trans-Aravalli Rajasthan as well. The overall evidence is consistent with a model of multiphase assembly of Gondwanaland from separate continental landmasses.

  2. Constraining dolomitization by Mg isotopes: A case study from partially dolomitized limestones of the middle Cambrian Xuzhuang Formation, North China

    Science.gov (United States)

    Peng, Yang; Shen, Bing; Lang, Xian-Guo; Huang, Kang-Jun; Chen, Ji-Tao; Yan, Zhen; Tang, Wen-bo; Ke, Shan; Ma, Hao-Ran; Li, Fang-Bing

    2016-03-01

    The "dolomite problem" refers to the rare dolomite formation in modern oceans that is in sharp contrast to the widespread ancient dolostone in rock record, as well as failure of laboratory inorganic dolomite precipitation at near Earth-surface temperature. Novel Mg isotope systematics provides a promising tool in resolving the "dolomite problem". Here, we develop a protocol to place constraints on the dolomitization process by using Mg isotopes. In this study, we measured Mg isotopic compositions (δ26Mg) of two batches of partially dolomitized limestone samples from the middle Cambrian Xuzhuang Formation in North China. δ26Mg varies between -0.55‰ and -3.18‰, and shows a negative linear correlation with 1>/[Mg>], suggesting that δ26Mg can be described by a binary mixing between the calcite and dolomite components. Mg isotopic composition of the dolomite component (δ26Mgdol) for the lower sample set that is collected from a 4 m stratigraphic interval containing three high-frequency ribbon rock-packstone cycles is -1.6‰, while δ26Mgdol for the upper sample set (from a thick sequence of ribbon rock) is significantly higher (-0.3‰). However, neither mineralogical and elemental compositions, carbon and oxygen isotopes, nor crystal morphologies of dolomite provides diagnostic criteria to differentiate these two batches of samples. δ26Mgdol of the Xuzhuang limestone is simulated by the Advective Flow (AF) and the Diffusion-Advection-Reaction (DAR) models. The AF model assumes that Mg is transported by advective fluid flows, while the DAR model simulates a contemporaneous seawater dolomitization process, in which Mg is delivered by diffusion. The AF modeling result indicates that δ26Mg of the dolomitization fluid is +0.4‰ and +1.7‰ for the lower and upper sample sets, respectively. These values are significantly higher than modern and Cenozoic seawater Mg isotopic composition, suggesting that the dolomitization fluid is not contemporaneous seawater. The

  3. Elasto-Plastic Constitutive Behavior in Three Lithofacies of the Cambrian Mt. Simon Sandstone, Illinois Basin, USA

    Science.gov (United States)

    Dewers, T.; Newell, P.; Broome, S. T.; Heath, J. E.; Bauer, S. J.

    2012-12-01

    The Mt. Simon Formation, a basal Cambrian sandstone underlying the Illinois Basin in the Central US, is a target for underground storage and waste injection which require an assessment of geomechanical behavior. The range of depositional environments, from braided streams and minor eolean features in the lower Mt Simon, to tidally-influenced near- and on-shore sands in the upper Mt. Simon, yield a heterogeneous formation with a range in porosity, permeability, and mechanical properties. We examine the experimental deformational behavior of three distinct Mt. Simon lithofacies via axisymmetric compressional testing. Initial yielding is confirmed with acoustic emissions in many of the tests and failure envelopes are determined for each lithofacies. The evolution of (assumed) isotropic elastic moduli are examined during testing by use of unload-reload cycles, which permit the separation of total measured strains into elastic and plastic (permanent) strains. The upper Mt Simon samples deform largely elastically at stresses encountered in the Illinois Basin, with very little modulus degradation. The lower Mt. Simon facies are weaker and deform plastically, with varying amounts of modulus degradation. Results are interpreted via petrographic observation of textural contrasts. This range in constitutive response is captured up to failure with a phenomenological elasto-plasticity model. Essential aspects to describe observed behavior used in the model include non-associative plasticity, stress-invariant dependent failure, an elliptical cap surface capturing shear effects on pore collapse, kinematic and isotropic hardening, nonlinear elasticity and elastic-plastic coupling, among other features. Static moduli derived from laboratory tests are compared to dynamic moduli from wellbore log response which can allow experimental results and model to be extrapolated to Mt. Simon occurrences across the basin. This work was funded in part by the Center for Frontiers of Subsurface

  4. Evidence for gill slits and a pharynx in Cambrian vetulicolians: implications for the early evolution of deuterostomes

    Directory of Open Access Journals (Sweden)

    Ou Qiang

    2012-10-01

    Full Text Available Abstract Background Vetulicolians are a group of Cambrian metazoans whose distinctive bodyplan continues to present a major phylogenetic challenge. Thus, we see vetulicolians assigned to groups as disparate as deuterostomes and ecdysozoans. This divergence of opinions revolves around a strikingly arthropod-like body, but one that also bears complex lateral structures on its anterior section interpreted as pharyngeal openings. Establishing the homology of these structures is central to resolving where vetulicolians sit in metazoan phylogeny. Results New material from the Chengjiang Lagerstätte helps to resolve this issue. Here, we demonstrate that these controversial structures comprise grooves with a series of openings. The latter are oval in shape and associated with a complex anatomy consistent with control of their opening and closure. Remains of what we interpret to be a musculature, combined with the capacity for the grooves to contract, indicate vetulicolians possessed a pumping mechanism that could process considerable volumes of seawater. Our observations suggest that food captured in the anterior cavity was transported to dorsal and ventral gutters, which then channeled material to the intestine. This arrangement appears to find no counterpart in any known fossil or extant arthropod (or any other ecdysozoan. Anterior lateral perforations, however, are diagnostic of deuterostomes. Conclusions If the evidence is against vetulicolians belonging to one or other group of ecdysozoan, then two phylogenetic options seem to remain. The first is that such features as vetulicolians possess are indicative of either a position among the bilaterians or deuterostomes but apart from the observation that they themselves form a distinctive and recognizable clade current evidence can permit no greater precision as to their phylogenetic placement. We argue that this is too pessimistic a view, and conclude that evidence points towards vetulicolians being

  5. Petrophysics of Palaeogene sediments

    DEFF Research Database (Denmark)

    Awadalkarim, Ahmed

    ) the siliceous ooze sediments from the Norwegian Sea, and 3) the Palaeogene shale from both the Atlantic and the Danish basins. The three geological settings differ in water depths, temperature, effective stress and pressure. If the factors governing physical properties of the studied lithologies are well....... This Ph.D. study includes results of petrophysical and the amplitude versus offset (AVO) analyses of siliceous ooze. Based on fundamental relationships, ways of correcting density and neutron porosity logs were proposed. Additionally, the values of β and the AVO signature of water saturated siliceous ooze...... right, especially for the deep-sea cemented sediments where the water depth is high, and it may underestimate the real effective stress which may lead to severe engineering consequences such as a petroleum reservoir may suffer compaction or deformations as a result of changing in stress state during...

  6. Community Sediment Transport Model

    Science.gov (United States)

    2007-01-01

    are used to determine that model results are consistent across compilers, platforms, and computer architectures , and to ensure that changes in code do...Mississippi State University: Bhate During the early months of this project, the focus was on understanding ROMS-CSTM model, architecture , and...Marchesiello, J.C. McWilliams, & K.D. Stolzenbach, 2007: Sediment transport modeling on Southern Californian shelves: A ROMS case study. Continental

  7. SEDIMENTATION AND EROSION STUDIES

    Institute of Scientific and Technical Information of China (English)

    Chih Ted YANG

    2005-01-01

    @@ The river systems observed today is the cumulative result of surface, rill, and gully erosion, and sediment transport, scour, and deposition. The divisions of approach between these two related areas are man-made, and are not based on sound science. Most of the erosion studies are done by geologists and agricultural engineers who are concerned of the surface, rill, and gully erosion and the loss of agricultural land productivity. Hydraulic engineers are more interested in the study of sediment transport, scour, and deposition, and their impacts on river engineering and hydraulic structures in rivers and reservoirs. Erosion studies are often based on empirical relationships or field data to determinate the annual sediment yield from a watershed. On the other hand, hydraulic engineers focus their attention on solving equations based on assumed initial and boundary conditions with a time scale of days, hours, or seconds. Both approaches have their complementary strengths and weaknesses. It is important to provide a forum for specialists in both areas to communicate, exchange ideas, and learn from each other.

  8. Magnetism of quaternary sediments

    Science.gov (United States)

    Heller, Friedrich

    Magnetism of Quaternary sediments was the topic of a well-attended symposium held during the 13th INQUA (International Union of Quaternary Research) congress in Beijing, China, August 2-9. More than 40 papers were delivered by scientists from Belgium, England, France, Germany, Japan, New Zealand, Sweden, Switzerland, Taiwan, the United States, the Soviet Union, Yugoslavia, and other countries. The host country contributed to a productive session that was part of the first large scientific meeting to take place in Beijing after the June 4, 1989, upheaval.Nearly half of the studies focused on paleomagnetic and rock magnetic properties of loess in Alaska, Central Asia, China, and New Zealand. Magnetostratigraphic polarity dating was done at some sections in the western (Shaw et al.) and central Chinese loess plateau (Bai and Hus; Wang and Evans; Yue). The interpretation of the polarity pattern found in the western loess plateau still is not unambiguous. In the central part, certain polarity boundaries, such as the Brunhes/Matuyama (B/M) boundary, are found in slightly different stratigraphic positions (Hus et al.; Yue). In deep-sea sediments the lock-in depth of natural remanent magnetization (NRM) at the B/M boundary seems to be a linear function of sedimentation rate (de Menocal et al.). Although the magnetization process in the Chinese loess is not well understood, detailed records of polarity transitions have been reported for the B/M and the Jaramillo R→N transition (Ma et al.; Rolph).

  9. Beryllium Desorption from Sediments

    Science.gov (United States)

    Boschi, V.; Willenbring, J. K.

    2015-12-01

    Beryllium isotopes have provided a useful tool in the field of geochronology and geomorphology over the last 25 years. The amount of cosmogenic meteoric 10Be and native 9Be absorbed to soils often scales with the residence time and chemical weathering of sediments in a landscape, respectively. Thus, the concentrations in river sediment may be used to quantify the denudation of specific watersheds. When deposited in ocean sediment, these concentrations are thought to record the history of denudation on Earth over the last ~10 Ma. The use of both isotopes often relies on the premise of beryllium retention to sediment surfaces in order to preserve a landscape's erosion and weathering signature. Changes in setting, en route from the soil to fluvial system to the ocean, can cause beryllium desorption and may preclude some applications of the 10Be/9Be system. Four mechanisms were tested to determine the desorption potential of beryllium including a reduction in pH, an increase in ionic strength and complexation with soluble organic and inorganic species. These processes have the potential to mobilize beryllium into solution. For example, by both reducing the pH and increasing the ionic strength, competition for adsorption sites increases, potentially liberating beryllium from the sediment surface. In addition, organic and inorganic ligands can complex beryllium causing it to become mobilized. To determine which of these alterations influence beryllium desorption and to quantify the effect, we prepared separate solutions of beryllium bound to minerals and organic compounds and measured beryllium concentrations in solution before and after adjusting the pH, ionic strength, and changing inorganic and organic ligand concentrations. We conclude from our observations that overall, beryllium sorbed to organic compounds was more resistant to desorption relative to mineral-associated beryllium. Among the methods tested, a reduction in pH resulted in the greatest amount of

  10. Cyclic Sediment Trading Between Channel and River Bed Sediments

    Science.gov (United States)

    Haddadchi, A.

    2015-12-01

    Much of the previous work on sediment tracing has focused on determining either the initial sources of the sediment (soils derive from a particular rock type) or the erosion processes generating the sediment. However, alluvial stores can be both a source and sink for sediment transported by streams. Here geochemical and fallout radionuclide tracing of river-bed and alluvial sediments are used to determine the role of secondary sources, sediment stores, as potential sources of sediment leaving Emu Creek catchment, southeastern Queensland, Australia. Activity concentrations of 137Cs on the river sediments are consistent with channel erosion being the dominant source at all sites sampled along the river. To characterise the deposition and remobilisation cycles in the catchment, a novel geochemical tracing approach was used. Successive pockets of alluvium were treated as discrete sink terms within geochemical mixing models and their source contributions compared with those of river bed sediments collected adjacent to each alluvial pocket. Three different size fractions were examined; silts and clays (soil/rock type sources to river bed and alluvial sediments at each sampling site was identical for all three different size fractions, but varied along the stream. Combining these findings it is concluded that proximal alluvial stores dominated the supply of sediment to the river at each location, with this being particularly evident at the catchment outlet. Identical contribution of rock type sources to both river bed and alluvial pockets together with the dominant erosion being from channel banks indicates a high degree of 'trading' between the fluvial space and the alluvial space. Hence, management works aimed at primarily reducing the supply of sediments to the outlet of Emu Creek should focus on rehabilitation of channel banks in the lower catchment.

  11. Sediment yields of Wisconsin streams

    Science.gov (United States)

    Hindall, S.M.; Flint, R.F.

    1970-01-01

    Sediment in Wisconsin streams causes economic and engineering problems in water management and reduces the value of water for nearly all uses. Sediment produces problems such as reduced reservoir capacity, navigation hazards, increased cost of water treatment, property damage, temporary loss of farmland, destruction of feeding and nesting grounds of fish, and destruction of wildlife habitat. Sediment in water also reduces the aesthetic value of surface waters and is detrimental to the State's tourist and recreation industry.

  12. Respiration in ocean margin sediments

    OpenAIRE

    Andersson, J.H.

    2007-01-01

    The aim of this thesis was the study of respiration in ocean margin sediments and the assessments of tools needed for this purpose. The first study was on the biological pump and global respiration patterns in the deep ocean using an empirical model based on sediment oxygen consumption data. In this thesis the depth dependence of respiration patterns was modelled using a compiled data set of sediment oxygen consumption rates. We showed that the depth relationship can best be described by a do...

  13. Cambrian intermediate-mafic magmatism along the Laurentian margin: Evidence for flood basalt volcanism from well cuttings in the Southern Oklahoma Aulacogen (U.S.A.)

    Science.gov (United States)

    Brueseke, Matthew E.; Hobbs, Jasper M.; Bulen, Casey L.; Mertzman, Stanley A.; Puckett, Robert E.; Walker, J. Douglas; Feldman, Josh

    2016-09-01

    The Southern Oklahoma Aulocogen (SOA) stretches from southern Oklahoma through the Texas panhandle and into Colorado and New Mexico, and contains mafic through silicic magmatism related to the opening of the Iapetus Ocean during the early Cambrian. Cambrian magmatic products are best exposed in the Wichita Mountains (Oklahoma), where they have been extensively studied. However, their ultimate derivation is still somewhat contentious and centers on two very different models: SOA magmatism has been suggested to occur via [1] continental rifting (with or without mantle plume emplacement) or [2] transform-fault related magmatism (e.g., leaky strike-slip faults). Within the SOA, the subsurface in and adjacent to the Arbuckle Mountains in southern Oklahoma contains thick sequences of mafic to intermediate lavas, intrusive bodies, and phreatomagmatic deposits interlayered with thick, extensive rhyolite lavas, thin localized tuffs, and lesser silicic intrusive bodies. These materials were first described in the Arbuckle Mountains region by a 1982 drill test (Hamilton Brothers Turner Falls well) and the best available age constraints from SOA Arbuckle Mountains eruptive products are ~ 535 to 540 Ma. Well cuttings of the mafic through intermediate units were collected from that well and six others and samples from all but the Turner Falls and Morton wells are the focus of this study. Samples analyzed from the wells are dominantly subalkaline, tholeiitic, and range from basalt to andesite. Their overall bulk major and trace element chemistry, normative mineralogy, and Srsbnd Nd isotope ratios are similar to magmas erupted/emplaced in flood basalt provinces. When compared with intrusive mafic rocks that crop out in the Wichita Mountains, the SOA well cuttings are geochemically most similar to the Roosevelt Gabbros. New geochemical and isotope data presented in this study, when coupled with recent geophysical work in the SOA and the coeval relationship with rhyolites, indicates

  14. APPLICABILITY OF SEDIMENT TRANSPORT FORMULAS

    Institute of Scientific and Technical Information of China (English)

    Chih Ted YANG; Caian HUANG

    2001-01-01

    The paper provides a comprehensive testing of the applicability of 13 sediment transport formulas under different flow and sediment conditions. The dimensionless parameters used for testing the reliability and sensitivity of formulas are dimensionless particle diameter, relative depth, Froude number, relative shear velocity, dimensionless unit stream power, and sediment concentration. A total of 3,391 sets of laboratory and river data are used in the tests. Engineers may find the test results useful to their selection of formulas under different flow and sediment conditions.

  15. Sediment Geo-Probe System

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides wideband in situ measurement capability of compressional wave speed and attenuation and their spatial variability in marine sediments.DESCRIPTION:...

  16. Transport model of underground sediment in soils.

    Science.gov (United States)

    Jichao, Sun; Guangqian, Wang

    2013-01-01

    Studies about sediment erosion were mainly concentrated on the river channel sediment, the terrestrial sediment, and the underground sediment. The transport process of underground sediment is studied in the paper. The concept of the flush potential sediment is founded. The transport equation with stable saturated seepage is set up, and the relations between the flush potential sediment and water sediment are discussed. Flushing of underground sediment begins with small particles, and large particles will be taken away later. The pore ratio of the soil increases gradually. The flow ultimately becomes direct water seepage, and the sediment concentration at the same position in the water decreases over time. The concentration of maximal flushing potential sediment decreases along the path. The underground sediment flushing model reflects the flushing mechanism of underground sediment.

  17. Alluvial-eolian interaction in a Cambrian rift margin: the Pedra das Torrinhas and Pedra Pintada formations (Guaritas Group, RS

    Directory of Open Access Journals (Sweden)

    André Marconato

    2009-12-01

    Full Text Available This work presents a study of selected outcrops from the Pedra das Torrinhas Formation of the Guaritas Group (Cambrian, Camaquã Basin, near the basin bordering Encantadas Fault Zone. The studied succession includes alluvial fan deposits that pass laterally into eolian deposits. Sedimentary facies and architectural element analysis were performed, followed by sedimentary petrography and microscopic porosity analysis, aiming to characterize the porosity of the deposits and its spatial distribution. The main objective was to contribute to a better understanding of the porosity spatial distribution in depositional systems characterized by the interaction between alluvial and eolian processes, with special reference to deposits formed prior to the development of terrestrial plants. Porosity values are related to depositional processes, with higher porosities associated to eolian dune deposits (mean of 8.4%, and lower porosity related to interdunes (mean of 3.4% and alluvial fans (mean of 4.3%. Architectural elements analysis revealed the spatial relationships of these deposits, a response to the interplay of the eolian and alluvial processes. The integration of porosity data reveals that the interaction of alluvial and eolian processes results in heterogeneous distribution of porosity at the facies association scale. Eolian reworking of alluvial facies increases porosity whereas sheet-flood and other alluvial processes in the interdune areas reduce porosity.O presente trabalho consiste no estudo de afloramentos da Formação Pedra das Torrinhas do Grupo Guaritas (Cambriano, Bacia Camaquã, próximo à Zona de Falha das Encantadas. As sucessões estudadas incluem depósitos de leques aluviais que passam lateralmente para depósitos eólicos. Foram realizadas análises de fácies e de elementos arquiteturais, seguidos de petrografia sedimentar e análise microscópica de porosidade, com o objetivo de caracterizar a porosidade da unidade e sua

  18. Optical sedimentation recorder

    Science.gov (United States)

    Bishop, James K.B.

    2014-05-06

    A robotic optical sedimentation recorder is described for the recordation of carbon flux in the oceans wherein both POC and PIC particles are captured at the open end of a submersible sampling platform, the captured particles allowed to drift down onto a collection plate where they can be imaged over time. The particles are imaged using three separate light sources, activated in sequence, one source being a back light, a second source being a side light to provide dark field illumination, and a third source comprising a cross polarized light source to illuminate birefringent particles. The recorder in one embodiment is attached to a buoyancy unit which is capable upon command for bringing the sedimentation recorder to a programmed depth below the ocean surface during recordation mode, and on command returning the unit to the ocean surface for transmission of recorded data and receipt of new instructions. The combined unit is provided with its own power source and is designed to operate autonomously in the ocean for extended periods of time.

  19. The origin of life near deep-sea hydrothermal systems during the Cambrian explosion: data from the Kyzyl Tashtyg sulphide deposit (Central Asia)

    Science.gov (United States)

    Simonov, Vladimir; Terleev, Alexander; Safonova, Inna; Kotlyarov, Alexey; Stupakov, Sergey; Tokarev, Dmitry

    2015-04-01

    On Earth the solar radiation and the hydrothermal circulation both affect life evolution. Recent extensive studies of the World Ocean have shown that the biodiversity of Earth is linked with hydrothermal activity on the oceanic floor. These deep-sea ecosystems use chemical energy, not solar radiation. In the last quarter of the XX century, a new type of hydrothermal systems, so-called black smokers, was discovered in mid-oceanic ridges. As black smokers form sulfide ores and are surrounded by abundant bio-oases or symbioses, identification of their analogues in ancient orogenic belts is necessary for studying life origin and evolution. Of special importance are problems of life associated with deep-sea hydrothermal systems acted at the Precambrian-Cambrian boundary - the time of Cambrian explosion (Maruyama et al., 2013). During that explosion life significantly evolved and diversified due to dramatic changes of Earth's environment. Consequently, the early Cambrian - late Precambrian Kyzyl Tashtyg sulphide deposit of East Tuva in the Central Asian Orogenic Belt is of special interest. This deposit was formed on the bottom of ancient back-arc deep-sea basin as a result of black smoker hydrothermal activity and is hosted by volcanogenic-sedimentary rocks altered by the high temperature solutions. The altered Kyzyl Tashtyg basalts have an amygdules (filled by albite, epidote and carbonates), contain brown-green microfossils, often attached to their walls. The microfossils are thin tubes 5 to 25 microns in diameter and 500 microns long. This tubes are empty and have straight, curved or branching shape. Chemically, the tube material is close to epidote. In consideration of microscopic dimensions, simple morphology and similarity with modern tubular microorganisms, the studied tube-shaped microfossils can be related to cyanobacteria. Almost the same fossils, associated with oceanic basalt complexes, were described earlier (Furnes et al., 2007; Mcloughlin et al., 2007

  20. Two new species of Vestrogothia (Phosphatocopina, Crustacea) of Orsten-type preservation from the Upper Cambrian in western Hunan, South China

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Although fossils of Orsten-type preservation represented by Skaracarida and Phosphatocopina were first reported from the Middle and Upper Cambrian in western Hunan, South China in 2005, diversified phosphatocopine species have never been appropriately described and elucidated in terms of their evolutionary relationships. Here, we described two new species of Phosphatocopina, Vestrogothia anterispinata sp. nov. and V. bispinata sp. nov. The evolutionary relationship among all the valid species of Phosphatocopina is discussed and the phylogeny of Phosphatocopina is reestablished using cladistic analysis. Accordingly, phosphatocopines primitively evolved along two lineages: one evolved towards the emergence of lobes; the other evolved towards the emergence of dorsal spines. Respectively, lobes originated independently three times, and dorsal spines originated only once. With regard to the dorsal rims, interdorsum originated first, whereas dorsal furrow originated independently twice on the basis of interdorsum. Probably Hesslandona may represent a polyphyletic group, whereas Vestrogothia a monophyletic group.

  1. A comparison of the biological,geological events and environmental backgrounds between the Neoproterozoic-Cambrian and Permian-Triassic transitions

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The Neoproterozoic-Cambrian(N-C) and Permian-Triassic(P-T) transitions have been regarded the two most critical transitions in earth history because of the explosive biological radiation in the early Cambrian(the Cambrian Explosion) and the largest mass extinction at the end-Permian.Previous studies suggest that these two critical transitions showed certain comparability in major evolutionary events.In other words,a series of biological,geological,and geochemical events that had happened in the N-C transition occurred repeatedly during the P-T transition.Those events included continental re-configuration related to the deep mantle dynamics,global-scale glaciations,large C-,Sr-,and S-isotope perturbations indicating atmospheric and oceanic changes,abnormal precipitation of carbonates,and associated multiple biological radiations and mass extinctions.The coupling of those events in both N-C and P-T transitions suggests that deep mantle dynamics could be a primary mechanism driving dramatic changes of environment on the earth’s surface,which in turn caused major biological re-organizations.A detailed comparison of those events during the two critical transitions indicates that despite their general comparability,significant differences do exist in magnitude,duration,and frequency.The supercontinent Rodinia began to rift before the Snowball Earth time.By contrast,the supercontinent Pangea entered the dispersal stage after the greatest glaciation from the Late Carboniferous to Cisuralian.Quantitative data and qualitative analyses of different fossil groups show a more profound mass extinction during the N-C transition than at the end-Permian in terms of ecosystem disruption.This is indicated by the disappearance of the whole Ediacaran biota at the N-C boundary.The subsequent appearances of many new complex animals at phylum level in the early Cambrian mark the establishment of a brand new ecosystem.However,the end-Permian mass extinction is manifested mainly by the

  2. Gorceixite from the Upper Cambrian Rocks of the podwiśniówka Mine Pit, Holy Cross Mountains (South-Central Poland)

    Science.gov (United States)

    Migaszewski, Zdzisław M.; Starnawska, Ewa; Gałuszka, Agnieszka

    2007-01-01

    This report presents the results of a petrographical, mineralogical (SEM/EDS, XRD) and geochemical (XRF, CV-AAS, ICP-MS) study of gorceixite (barium aluminophosphate) from the abandoned Podwiśniówka mine pit. This site is highlighted by the presence of highly acidic pit pond whose chemistry is strongly affected by the exposed pyrite-bearing zone. The gorceixite occurs in the Upper Cambrian carbonaceous clayey shales, quartzites and tuffs in form of minute accumulations varying from about 0.5 to 100 μm in diameter. These accumulations infill voids, cavities, cracks and partly fissures in the rocks examined. The other minerals of the crandallite series, i.e. florencite and goyazite, can be found only in trace amounts. The gorceixite-bearing rocks, especially carbonaceous clayey shales, are characterized by the highest concentrations of REE reaching 455.09 mg·kg-1. In addition, these rocks are distinctly enriched in light rare earth elements (LREE), with the La/Yb ratio ranging from 24.44 through 36.30. Some of the examined gorceixite accumulations are paragenetically linked to the veined pyrite and nacrite. The latter mineral is indicative of crystallization temperatures of about 200 to 300°C. The coexistence of gorceixite with the veined nacrite or pyrite mineralization and the volcaniclastic rocks, as well as the microtextural features and high concentrations of REE in the gorceixite-bearing parent rocks suggest that this mineral formed as a result of both hydrothermal and volcanic activity in a shallow-marine basin during the late Cambrian.

  3. Paleoproterozoic mojaveprovince in northwestern Mexico? Isotopic and U-Pb zircon geochronologic studies of precambrian and Cambrian crystalline and sedimentary rocks, Caborca, Sonora

    Science.gov (United States)

    Lang, Farmer G.; Bowring, S.A.; Matzel, J.; Maldonado, G.E.; Fedo, C.; Wooden, J.

    2005-01-01

    Whole-rock Nd isotopic data and U-Pb zircon geochronology from Precambrian crystalline rocks in the Caborca area, northern Sonora, reveal that these rocks are most likely a segment of the Paleoproterozoic Mojave province. Supporting this conclusion are the observations that paragneiss from the ??? 1.75 Ga Bamori Complex has a 2.4 Ga Nd model age and contains detrital zircons ranging in age from Paleo- proterozoic (1.75 Ga) to Archean (3.2 Ga). Paragneisses with similar age and isotopic characteristics occur in the Mojave province in southern California. In addition, "A-type" granite exposed at the southern end of Cerro Rajon has ca 2.0 Ga Nd model age and a U-Pb zircon age of 1.71 Ga, which are similar to those of Paleoproterozoic granites in the Mojave province. Unlike the U.S. Mojave province, the Caborcan crust contains ca. 1.1 Ga granite (Aibo Granite), which our new Nd isotopic data suggest is largely the product of anatexis of the local Precambrian basement. Detrital zircons from Neoproterozoic to early Cambrian miogeoclinal arenites at Caborca show dominant populations ca. 1.7 Ga, ca. 1.4 Ga, and ca. 1.1 Ga, with subordinate Early Cambrian and Archean zircons. These zircons were likely derived predominately from North American crust to the east and northeast, and not from the underlying Caborcan basement. The general age and isotopic similarities between Mojave province basement and overlying miogeoclinal sedimentary rocks in Sonora and southern California is necessary, but not sufficient, proof of the hypothesis that Sonoran crust is allochthonous and was transported to its current position during the Mesozoic along the proposed Mojave-Sonora megashear. One viable alternative model is that the Caborcan Precambrian crust is an isolated, autochthonous segment of Mojave province crust that shares a similar, but not identical, Proterozoic geological history with Mojave province crust found in the southwest United States ?? 2005 Geological Society of America.

  4. Zircon U-Pb age and geochemical constraints on the origin and tectonic implication of Cadomian (Ediacaran-Early Cambrian) magmatism in SE Turkey

    Science.gov (United States)

    Beyarslan, Melahat; Lın, Yu-Chin; Bingöl, A. Feyzi; Chung, Sun-Lin

    2016-11-01

    The Bitlis-Pütürge Massifs and Derik volcanics that crop out in the Southeast Anatolian Belt are parts of the Cadomian domain in Anatolia where relicts of the oldest continental crust of Turkey are exposed. The Bitlis-Pütürge Massifs contain a Neoproterozoic basement, with overlying Phanerozoic rocks that were imbricated, metamorphosed and thrust over the edge of Arabia during the Alpine orogeny. The basement consists mainly of granitic to tonalitic augen gneisses and metagranites, associated with schists, amphibolites and paragneisses. Based on whole-rock geochemical data, the augen gneisses are interpreted to have protoliths crystallized from subduction zone magmas. This study conducted the first zircon dating on two augen gneisses that gave 206Pb/238U dates of 551 ± 6 and 544 ± 4 Ma, interpreted as the formation ages of the Pütürge Massif, broadly coeval to those of the Bitlis metagranites and the Derik volcanics that occurred from ca. 581 to 529 Ma (the Ediacaran-early Cambrian). The ɛHf(t) values (+1.2 to -5.3) of the dated zircons, with crustal model ages (TDMC) from 1.4 to 1.8 Ga, indicate that formation of the Pütürge Massif involves an older, most likely the Mesoproterozoic, continental crust component. Similar to the Bitlis-Pütürge gneisses, coeval basement rocks are widespread in the Tauride-Anatolide platform (e.g., the Menderes Massif). All these dispersed Cadomian basement rocks are interpreted as fragments of the Ediacaran-Early Cambrian continental arcs bordering the active margin of northern Gondwana.

  5. Rhenium-osmium isotope constraints on the age and source of the platinum mineralization in the Lower Cambrian black rock series of Hunan-Guizhou provinces, China

    Institute of Scientific and Technical Information of China (English)

    李胜荣; 肖启云; 申俊峰; 孙丽; 刘波; 阎柏琨; 江永宏

    2003-01-01

    The shale at the bottom of the Lower Cambrian black series in South China is rich in nonferrous metals, noble metals, rare and dispersed elements and radioactive elements, known as "polyelement-rich bed". In order to date and trace the source of the platinum group elements, 6 samples were collected from the Zhongnan region of Guizhou Province, and the Ganzi- ping-Sancha region of Hunan Province. The contents and isotopes of Re and Os were measured. Re and Os are positively correlated with each other and the correlation coefficient between 187Os/188Os and 187Re/188Os is 0.99856. On the 187Os/188Os-187Re/188Os diagram, 6 sample points are well-distributed along the (542±11) Ma fitting isochron in high coincidence and with 0.84±0.12 as the initial 187Os/188Os value. The result displays that the age value of the major mineralization of Re, Os and other platinum group elements is (542±11) Ma, which is identical with the stratigraphical age of the wall rocks; the 'polyelement beds' in Hunan and Guizhou provinces bear high isochroneity; the differences of the forming times of different materials in the 'polyelement bed' of the same area do not surpass the error limit permissible for Re-Os date fitting; there exists no distinct time interval between the formation of the diagenetic veinlets and that of the 'polyelement bed', or the Re-Os isotope composition has not been distinctly changed by the former process; basaltic crust might be the major source of Re, Os, other platinum group and trace elements in the Lower Cambrian 'polyelement bed' of Hunan and Guizhou provinces.

  6. Re-Os isotopes and PGE geochemistry of black shales and intercalated Ni-Mo polymetallic sulfide bed from the Lower Cambrian Niutitang Formation, South China

    Institute of Scientific and Technical Information of China (English)

    JIANG Shaoyong; YANG Jinghong; LING Hongfei; FENG Hongzhen; CHEN Yongquan; CHEN Jianhua

    2003-01-01

    The Lower Cambrian Niutitang Formation consists of a thick black shale sequence with a regionally distributed conformable Ni-Mo polymetallic sulfide horizon and a chert bed at its basal strata on theYangtze Platform, South China. In this paper, we discuss all available data on Re-Os isotopes and Platinum Group Element (PGE) distribution pattern of the Ni-Mo polymetallic sulfide ore and its host rocks (black shales, cherts, and phosphorites) from Guizhou and Hunan provinces. Our results show that the black shales and the Ni-Mo sulfide ore have a high initial 187Os/188Os ratio of 0.78~0.86, indicating that the Early Cambrian ocean across the Yangtze Platform had a highly radiogenic Os value. This ratio is slightly lower than but still similar to present-day seawater, possibly as a result of high continental weathering at that time. The Ni-Mo sulfide ore yields a Re-Os isochron of 537±10 Ma (MSWD=11.9), possibly representing the depositional age of the Niutitang Formation. The chondrite-normalized PGE pattern, Pt anomaly (Pt/Pt*), Pt/Pd, Ir/Pd, Au/Ir and Re/Mo ratios of the Ni-Mo sulfide ore and its host rocks from South China indicate a varying source contribution of the PGE and other metals for different rocks. It is suggested that the cherts and Ni-Mo sulfide ore may have a significant proportion of PGE and probably other metals deriving from submarine-hydrothermal fluids with a mantle signature.

  7. Intensive landfarming of contaminated sediments

    NARCIS (Netherlands)

    Wieggers, H.J.J.; Bezemer, H.W.

    1995-01-01

    The biodegradation of polycyclic aromatic hydrocarbons (PAH) and mineral oil was investigated in heavily and normally polluted sediments. The aims of the research were: to improve the knowledge of dewatering and ripening of sediments in an open land-farm, to quantify the biodegradation in two sedime

  8. Luminescence dating of Netherland's sediments

    NARCIS (Netherlands)

    Wallinga, J.; Davids, F.; Dijkmans, J.W.A.

    2007-01-01

    Over the last decades luminescence dating techniques have been developed that allow earth scientists to determine the time of deposition of sediments. In this contribution we revity: 1) the development of the methodology, 2) tests of the reliability of luminescence dating on Netherlands' sediments;

  9. Modeling microalgal flocculation and sedimentation

    NARCIS (Netherlands)

    Salim, S.; Gilissen, L.J.W.J.; Rinzema, A.; Vermuë, M.H.; Wijffels, R.H.

    2013-01-01

    In this study, a combined flocculation and sedimentation model is developed. The model predicts the time needed to reach a desired concentration of microalgal suspension in a sedimentation tank. The concentration of the particles as function of the time and the position in the tank is described. The

  10. Reservoir sedimentation; a literature survey

    NARCIS (Netherlands)

    Sloff, C.J.

    1991-01-01

    A survey of literature is made on reservoir sedimentation, one of the most threatening processes for world-wide reservoir performance. The sedimentation processes, their impacts, and their controlling factors are assessed from a hydraulic engineering point of view with special emphasis on mathematic

  11. Study on the Reutilization of River Sediment

    Institute of Scientific and Technical Information of China (English)

    LIU Gui-yun; JIANG Pei-hua; XI Dan-li

    2002-01-01

    Main components and properties of river sediment are introduced. Secondary pollution of river sediments to the water quality of the river is clarified. The methods of the reutilization of river sediment are elucidated.

  12. Geochemistry of Sediments from the PLUTO Database

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Geochemical data for unconsolidated sediments (stream sediments, lake sediments, etc.) collected in the US and analyzed by the USGS. These data were originally...

  13. Targeting sediment management strategies using sediment quantification and fingerprinting methods

    Science.gov (United States)

    Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; hUallacháin, Daire Ó.

    2016-04-01

    Cost-effective sediment management is required to reduce excessive delivery of fine sediment due to intensive land uses such as agriculture, resulting in the degradation of aquatic ecosystems. Prioritising measures to mitigate dominant sediment sources is, however, challenging, as sediment loss risk is spatially and temporally variable between and within catchments. Fluctuations in sediment supply from potential sources result from variations in land uses resulting in increased erodibility where ground cover is low (e.g., cultivated, poached and compacted soils), and physical catchment characteristics controlling hydrological connectivity and transport pathways (surface and/or sub-surface). Sediment fingerprinting is an evidence-based management tool to identify sources of in-stream sediments at the catchment scale. Potential sediment sources are related to a river sediment sample, comprising a mixture of source sediments, using natural physico-chemical characteristics (or 'tracers'), and contributions are statistically un-mixed. Suspended sediment data were collected over two years at the outlet of three intensive agricultural catchments (approximately 10 km2) in Ireland. Dominant catchment characteristics were grassland on poorly-drained soils, arable on well-drained soils and arable on moderately-drained soils. High-resolution (10-min) calibrated turbidity-based suspended sediment and discharge data were combined to quantify yield. In-stream sediment samples (for fingerprinting analysis) were collected at six to twelve week intervals, using time-integrated sediment samplers. Potential sources, including stream channel banks, ditches, arable and grassland field topsoils, damaged road verges and tracks were sampled, oven-dried (account for particle size and organic matter selectivity processes. Contributions from potential sources type groups (channel - ditches and stream banks, roads - road verges and tracks, fields - grassland and arable topsoils) were

  14. Dating of sediments and determination of sedimentation rate. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Illus, E. [ed.

    1998-08-01

    The Second NKS (Nordic Nuclear Safety Research)/EKO-1 Seminar was held at the Finnish Centre for Radiation and Nuclear Safety (STUK) on April 2-3, 1997. The work of the NKS is based on 4-year programmes; the current programme having been planned for the years 1994-1997. The programme comprises 3 major fields, one of them being environmental effects (EKO). Under this umbrella there are 4 main projects. The EKO-1 project deals with marine radioecology, in particular bottom sediments and sediment processes. The programme of the second seminar consisted of 8 invited lecturers and 6 other scientific presentations. Dating of sediments and determination of sedimentation rate are important in all types of sedimentological study and model calculations of fluxes of substances in the aquatic environment. In many cases these tasks have been closely related to radioecological studies undertaken in marine and fresh water environments, because they are often based on measured depth profiles of certain natural or artificial radionuclides present in the sediments. During recent decades Pb-210 has proved to be very useful in dating of sediments, but some other radionuclides have also been successfully used, e.g. Pu-239,240, Am-241 and Cs-137. The difficulties existing and problems involved in dating of sediments, as well as solutions for resolving these problems are discussed in the presentations

  15. 寒武纪早期大气-海洋氧含量与生命大爆发%Atmosphere-Ocean Oxygen Levels and Biotic Explosion in the Early Cambrian

    Institute of Scientific and Technical Information of China (English)

    李超; 金承胜

    2015-01-01

    The relationship between the Earth environment and the biotic explosion in early Cambrian (ca.541 -5 10,Ma) is one top geobiological issue.Here,we systematically summarized three major hypotheses for the relationship between the atmosphere-ocean oxygen level and the biotic evolution in early Cambrian,including that (1)increasing oxygenation of at-mosphere and ocean caused the Cambrian explosion,(2)the emergence and evolution of lives resulted in oxygenation of atmosphere and ocean,(3)the atmosphere-ocean oxygen level and the evolution of lives are not interrelated.Although each hypothesis is supported by specific evidences,these hypotheses show significantly inconsistent with partial ocean chemistry records in early Cambrian and investigations of lives in modern ocean analogues.In addition,the spatiotemporal heterogeneity of early Cambrian life evolution is not considered in these hypotheses.By synthesizing these major hypotheses with available data on Cambrian tectonic activities,terrestrial fluxes,ocean chemistry and life evolution patterns,we dis-cussed the possible relationship between the Earth environment and the biotic radiation in early Cambrian.We found that an interactions and co-evolution relationship instead of those simple unidirectional relationships emphasized by above three hypotheses should exist between the Earth environment and the biotic radiation in early Cambrian.%寒武纪早期(541~510,Ma)地球环境与这一时期生命大爆发之间的关系一直是地球生物学研究的热点问题之一。本文系统总结了目前寒武纪早期大气-海洋氧含量与这一时期生命辐射之间关系的3种假说:大气-海洋的氧含量增加导致了寒武纪生命大爆发;寒武纪生命大爆发导致了大气-海洋氧化以及二者之间没有因果关系。3种假说均有相应的支持证据,但也存在与寒武纪早期海洋化学记录、与现代海洋观察不符和上述假说均未考虑寒武纪早期生命

  16. Haw River sediment quality assessment

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report documents an evaluation of chemical contaminants in, and toxicity of, sediments collected from impoundments created by dams on the Haw River in Alamance...

  17. Cable Bacteria in Freshwater Sediments

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Kristiansen, Michael; Frederiksen, Rasmus

    2015-01-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable...... bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures...... marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary...

  18. SEDIMENT MANAGEMENT IN HYDROELECTRIC PROJECTS

    Institute of Scientific and Technical Information of China (English)

    K.G.RANGA RAJU; U.C.KOTHYARI

    2005-01-01

    Withdrawal of water from a river into a canal involves the construction of a barrage or a dam across the river depending on whether the river is perennial or not. The design of the reservoir upstream of the dam and of the canal requires consideration of the sediment load carried by the river in case the river is sediment-laden. The basic equations concerning morphological changes in such rivers are discussed with particular reference to computation of reservoir sedimentation. The hydraulics of lined canals carrying wash load is examined from the point of view of limiting transport capacity and changes in frictional resistance. Lastly,the methods of design of sediment extraction devices like settling basins and vortex chambers are presented.

  19. Seafloor Surficial Sediments (Deck 41)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The National Geophysical Data Center (NGDC) "Deck41" database contains surficial sediment descriptions for over 36,000 seafloor samples worldwide. The file was begun...

  20. Evidence for Cambrian petroleum source rocks in the Rome trough of West Virginia and Kentucky, Appalachian basin: Chapter G.8 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

    Science.gov (United States)

    Ryder, Robert T.; Harris, David C.; Gerome, Paul; Hainsworth, Timothy J.; Burruss, Robert A.; Lillis, Paul G.; Jarvie, Daniel M.; Pawlewicz, Mark J.; Ruppert, Leslie F.; Ryder, Robert T.

    2014-01-01

    A 130-foot-thick Cambrian black shale sampled from a core between 11,150 and 11,195 feet in the Exxon No. 1 Smith well in Wayne County, W. Va., has been identified as a good to very good source rock. The black shale is located in the Middle Cambrian Rogersville Shale of the Conasauga Group. Total organic carbon (TOC) values of four samples that range from 1.2 to 4.4 weight percent (average 2.6 weight percent) are the highest reported to date in the pre-Knox section of the Rome trough. Although the samples are probably in the zone of gas generation based on their low hydrogen index values (55 to 63) and temperature maximum of second hydrocarbon peak (S2) values of about 465°C, first hydrocarbon peak (S1) values of 0.81 to 2.71 indicate that they contain free extractable hydrocarbons. A bitumen sample extracted from the Rogersville Shale is characterized by (1) a broad spectrum of n-alkanes from n-C11 through n-C30, (2) strong odd-carbon predominance in the n-C13 to n-C19 range, and (3) small but detectable amounts of isoprenoids pristane and phytane. The strong odd-carbon predominance of the n-C15 to n-C19 n-alkanes is commonly attributed to the Ordovician alga Gloeocapsomorpha prisca. This occurrence of G. prisca is among the first to be reported in Cambrian rocks. Thin black shale beds collected from the Lower to Middle Cambrian Rome Formation in the Texaco No. 1 Kirby well in Garrard County, Ky., have TOC values as high as 3.2 percent, hydrogen index values as high as 417, and bitumen extract characteristics similar to the Rogersville Shale.

  1. Luminescence dating of Netherlands’ sediments

    OpenAIRE

    Wallinga, J.; Davids, F.; Dijkmans, J.W.A.

    2007-01-01

    Over the last decades luminescence dating techniques have been developed that allow earth scientists to determine the time of deposition of sediments. In this contribution we review: 1) the development of the methodology; 2) tests of the reliability of luminescence dating on Netherlands’ sediments; and 3) geological applications of the method in the Netherlands. Our review shows that optically stimulated luminescence dating of quartz grains using the single aliquot regenerative dose method yi...

  2. Mathematical theory of sedimentation analysis

    CERN Document Server

    Fujita, Hiroshi; Van Rysselberghe, P

    1962-01-01

    Mathematical Theory of Sedimentation Analysis presents the flow equations for the ultracentrifuge. This book is organized into two parts encompassing six chapters that evaluate the systems of reacting components, the differential equations for the ultracentrifuge, and the case of negligible diffusion. The first chapters consider the Archibald method for molecular weight determination; pressure-dependent sedimentation; expressions for the refractive index and its gradient; relation between refractive index and concentration; and the analysis of Gaussian distribution. Other chapters deal with th

  3. RESEARCH PROGRESS AND SIGNIFICANCE OF THE CAMBRIAN SMALL CARBONACEOUS FOSSILS (SCFs)%寒武系小碳化石(SCFs)的研究进展及意义

    Institute of Scientific and Technical Information of China (English)

    李向峰; 毛颖颜; 林日白

    2013-01-01

    所谓SCFs (Small Carbonaceous Fossils),可译为“小碳化石”,其大小跨越了传统的微观与宏观界线(以肉眼可见与否为标准),是一个特定化石群体的统称.它的实质含义,是指通过氢氟酸(HF)等无机酸浸泡泥岩/页岩样品后经过滤、浓缩而获得的一类体积微小的有机碳质薄膜化石,包括后生动物残片、丝状藻/菌类碎片、疑源类等类型.在小碳化石概念被正式提出之前,国外学者曾先后用有机质壁微体化石(Organic-walled microfossils)、碳质微体化石(Carbonaceous microfossils)与布尔吉斯页岩型微体化石(Burgess Shale-type microfossils)来表述此类化石.目前在国际上,与布尔吉斯页岩型(BST)化石库和奥斯坦(Orsten)型化石库一样,小碳化石已经成为寒武纪古生物学及生物埋藏学等领域研究的一个重要的新窗口;同时,通过三类特异埋藏化石的对比研究,实现优势互补,从而能够更好地阐述早期生物的演化与多样性.%The term "SCFs" stands for Small Carbonaceous Fossils,which defines a special group of fossils,with size ranges across the conventional boundary between microscopic and macroscopic views.SCFs are also known as "organic-walled microfossils","carbonaceous microfossils",and/or "Burgess Shale type microfossils".Due to more findings worldwide SCFs is now becoming a new important window for Cambrian palaeontological and taphonomical studies because it can bridge the preservation gaps between Cambrian Lagerst(a)tten,including Burgess Shale-type (BST)macrofossils and Orsten-type fossils.SCFs were recovered through a series of procedures as followed:macerate each sample of mudstone/shale with hydrofluoric acid (HF) until it disaggregated,dilute the solution to neutrality,filter the sample through a sieve and then concentrate the residues.Concentrated residues can be picked for SCFs,including metazoan fragments,filamental algae/fungi and acritarchs.Furthermore,SCFs combined with

  4. Trace fossils and sedimentary facies from a Late Cambrian-Early Ordovician tide-dominated shelf (Santa Rosita Formation, northwest Argentina): Implications for ichnofacies models of shallow marine successions

    Science.gov (United States)

    Mangano, M.G.; Buatois, L.A.; Acenolaza, G.F.

    1996-01-01

    The Santa Rosita Formation is one the most widely distributed lower Paleozoic units of northwest Argentina. At the Quebrada del Salto Alto section, east of Purmamarca, Jujuy Province, it is represented by four sedimentary facies: thick-bedded planar cross-stratified quartzose sandstones (A), thin-bedded planar cross-stratified quartzose sandstones and mudstones (B), wave-rippled sandstones and bioturbated mudstones (C), and black and greenish gray shales (D). Paleocurrent data, sandstone architecture, and sedimentary structures from facies A and B indicate bipolar/bimodal paleoflows, suggesting the action of tidal currents. The succession is interpreted as that of a tide-dominated shelf, with only secondary influence of wave processes. Trace fossils are restricted to facies B and C. The Cruziana ichnocoenosis is preserved on the soles of thin-bedded planar cross-stratified quartzose sandstones (facies B). This ichnocoenosis consists of Conostichus isp., Cruziana omanica, C. semiplicata, C. cf. tortworthi, Cruziana isp. Helminthopsis abeli, Monomorphichnus bilinearis, M. multilineatus, Palaeophycus tubularis, Rusophycus carbonarius, R. latus, and R. isp. The occurrence of Cruziana semiplicata, C. omanica, C. cf. tortworthi, and Rusophycus latus supports a Late Cambrian-Tremadoc age. Slabbing of Cruziana shows complex interactions between biologic and sedimentologic processes, and suggests a predominance of exhumed traces, washed out and recast by tractive sand deposition. Sandstone soles are densely packed with biogenic structures and exhibit distinctive clusters of Rusophycus isp. that most likely represent trilobite nesting burrows. The Cruziana ichnocoenosis records the resident fauna of a protected, lower intertidal to subtidal interbar setting. The Skolithos ichnocoenosis is represented by high to low density vertical burrows of Skolithos linearis, which extend downwards to the quartzose sandstone soles of facies B and cross the Cruziana ichnocoenosis. The

  5. Rock magnetic and other geophysical signatures of relative sea level change in the Middle Cambrian Wheeler Formation, Drum Mountains, West-Central Utah

    Science.gov (United States)

    Halgedahl, S. L.; Jarrard, R. D.

    2011-12-01

    The Wheeler Formation of West-Central Utah is a succession of mixed carbonate-siliciclastic rocks deposited during the Middle Cambrian along a passive continental margin of Laurentia (western margin, in today's coordinates). The depositional setting was a gentle ramp, bounded by a normal fault on the south. The present study focuses on the Wheeler Formation in the Drum Mountains, Utah, which is thought to have recorded Middle Cambrian sea level changes and which is known to yield exceptionally-preserved fossils with soft parts, similar to the famed Burgess shale. An integrated approach has been used here to investigate the following: (1) high-resolution changes in water depth (sea level changes?) with stratigraphic position; (2) where exceptionally preserved fossils are most likely to occur; and (3) mineralogical indicators of sea level change, such as magnetic susceptibility and other rock magnetic properties. Rocks consist of limestones, argillaceous limestones, and finely-bedded mudstones (shales). Methods used here are: measurements of magnetic susceptibility, natural remanent magnetization, and viscous remanent magnetization; hysteresis loops; spectral gamma ray; coulometry to determine calcite content; X-ray diffraction; and field mapping. In these rocks, mineralogical analyses indicate primarily a 2-component system of calcite and terrigenous minerals, mainly illite. Magnetic susceptibility, gamma ray, and coulometry results strongly indicate that magnetic susceptibility stems primarily from the paramagnetic clay component, namely, illite. Thus, both magnetic susceptibility and gamma ray increase linearly with decreasing calcite content throughout the section studied. Deep-water shales yield very high values of gamma ray and magnetic susceptibility; by contrast, carbonates with low gamma ray and low magnetic susceptibilities were deposited in relatively shallow water. These results lead to the following conclusions: (1) changes in relative water depth have

  6. 中国寒武纪双壳类研究之评述%REVIEW OF THE STUDY OF CAMBRIAN BIVALVES IN CHINA

    Institute of Scientific and Technical Information of China (English)

    方宗杰

    2004-01-01

    The genus Yangtzedonta Yu,1985 have not been accepted by bivalve specialists as a bivalve as Yu originally reported in studying early phylogeny and evolution of the class Bivalvia. Recently,Qian Yi(2001)solved this puzzle.He confirms that Y.primitiva Yu is only an incomplete specimen of Xianfengella prima He et Yang,a problematical small shelly fossil.It is a pity that Qian confused Xianfengoconcha elliptica Zhang with the oldest certain bivalve. It is necessary to review comprehensively the study of Cambrian bivalves in China.Xiangfengoconcha Zhang,1980 shows an elongate,weakly inclined anterior and posterior toothlike structure on each side of the beak.This is an obolellid type hinge structure rather than the bivalve palaeoheterodont type.Moreover lamellar teeth of palaeoheterodonts were derived from the fusion of discrete teeth of palaeotaxodont type.Therefore,it is unlikely that the most primitive bivalve was such a form with lamellar teeth as Xianfengoconcha elliptica Zhang.At present,Pojetaia Jell,1980 is the only undoubted Cambrian bivalve in China.%长期以来,双壳类研究者虽未将扬子蛤(Yangtzedonta Yu)纳入到双壳类早期系统演化的研究范畴,却又难以予以完全否定.最近,钱逸的工作终于解决了这一悬案,这是寒武纪带壳软体动物研究的一项重要进展.然而,钱逸对双壳类早期演化的理解仍存在着误解,例如,将Xianfengoconcha Zhang当作是"最古老的双壳类",为此有必要对近二十年来我国寒武纪双壳类的研究进行回顾与总结.Xianfengoconcha发育有两侧对称排列的所谓"片状齿",实属腕足类小圆货贝型铰合构造.化石证据表明,真正的片状齿是由古栉齿型铰齿演化而来,因此,古异齿型不是双壳类最古老的铰齿类型.目前,我国没有争议的寒武纪双壳类只有Pojetaia Jell一属.

  7. 塔里木盆地沙雅隆起星火1井寒武系烃源岩特征%Characteristics of Cambrian source rocks in well XH1, Shaya Uplift, Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    朱传玲; 闫华; 云露; 韩强; 马慧明

    2014-01-01

    在对塔里木盆地北部星火1井寒武系玉尔吐斯组灰黑、黑色碳质泥岩进行一系列有机地球化学特征测试分析的基础上,从有机碳、氯仿沥青“A”、生烃潜量、热解峰温、海相镜状体反射率、烃源岩可溶抽提物和饱和烃色质特征等方面着手,对该烃源岩的有机质丰度、成熟度及类型进行分析。结合前人研究成果,讨论了这套烃源岩与以往报道的寒武系烃源岩的异同,并开展了与塔河原油的油-岩对比分析。结果表明,该套烃源岩有机质丰度高,而且已达高成熟热演化阶段,与柯坪露头肖尔布拉克剖面下寒武统玉尔吐斯组烃源岩特征类似;星火1井下寒武统黑色碳质页岩有机质地化特征与塔河油田原油具亲源性。%In the northwestern Shaya Uplift of the Tarim Basin, gray and black carbonaceous mudstones were collected from the Cambrian Yuertusi Formation in the well XH1, and were tested for organic geochemistry. The analyses included the determinations of organic carbon (TOC), chloroform bitumen “A”, hydrocarbon generation potential, pyrolysis peak temperature, marine vitrinite, soluble extraction of source rock, gas chromatography and so on. The organic matter abundance, maturity and type of source rocks were studied. The Cambrian source rocks in the well XH1 were compared with other Cambrian source rocks in previous reports. Oil-source correlation of the studied source rocks was made compared to those from the Tahe oilfield. The studied source rocks have high organic matter abundance, and have entered the high-mature stage for thermal evolution, which is similar with the source rocks in the Lower Cambrian Yuertusi Formation on the Xiaoerbulak profile in the Keping area. There are some similar geochemical characteristics between the Lower Cambrian black carbonaceous shale and the crude oil from the Tahe oilfield.

  8. River sediment supply, sedimentation and transport of the highly turbid sediment plume in Malindi Bay, Kenya

    Institute of Scientific and Technical Information of China (English)

    JOHNSON U.Kitheka

    2013-01-01

    The paper presents results of a study on the sediment supply and movement of highly turbid sediment plume within Malindi Bay in the Northern region of the Kenya coast.The current velocities,tidal elevation,salinity and suspended sediment concentrations (TSSC)were measured in stations located within the bay using Aanderaa Recording Current Meter (RCM-9),Turbidity Sensor mounted on RCM-9,Divers Gauges and Aanderaa Temperature-Salinity Meter.The study established that Malindi Bay receives a high terrigenous sediment load amounting to 5.7 × 106 ton·yr-1.The river freshwater supply into the bay is highly variable ranging from 7 to 680 m3·s-1.The high flows that are > 150 m3·s-1 occurred in May during the South East Monsoon (SEM).Relatively low peak flows occurred in November during the North East Monsoon (NEM) but these were usually <70 m3·s-1.The discharge of highly turbidity river water into the bay in April and May occurs in a period of high intensity SEM winds that generate strong north flowing current that transports the river sediment plume northward.However,during the NEM,the river supply of turbid water is relatively low occurring in a period of relatively low intensity NEM winds that result in relatively weaker south flowing current that transports the sediment plume southward.The mechanism of advection of the sediment plume north or south of the estuary is mainly thought to be due to the Ekman transport generated by the onshore monsoon winds.Limited movement of the river sediment plume southward towards Ras Vasco Da Gama during NEM has ensured that the coral reef ecosystem in the northern parts of Malindi Marine National Park has not been completely destroyed by the influx of terrigenous sediments.However,to the north there is no coral reef ecosystem.The high sediment discharge into Malindi Bay can be attributed to land use change in the Athi-Sabaki River Basin in addition to rapid population increase which has led to clearance of forests to open land

  9. Two new species of Vestrogothia (Phosphatocopina,Crustacea) of Orsten-type preservation from the Upper Cambrian in western Hunan,South China

    Institute of Scientific and Technical Information of China (English)

    ZHANG HuaQiao; DONG XiPing

    2009-01-01

    Although fossils of Orsten-type preservation represented by Skaracarida and Phosphatocopina were first reported from the Middle and Upper Cambrian in western Hunan,South China in 2005,diversified phosphatocopine species have never been appropriately described and elucidated in terms of their evolutionary relationships.Here,we described two new species of Phosphatocopina,Vestrogothia anterispinata sp.nov.and V.bispinata sp.nov.The evolutionary relationship among all the valid spe-cies of Phosphatocopina is discussed and the phylogeny of Phosphatocopina is reestablished using cladistic analysis.Accordingly,phosphatocopines primitively evolved along two lineages:one evolved towards the emergence of lobes; the other evolved towards the emergence of dorsal spines.Respec-tively,lobes originated independently three times,and dorsal spines originated only once.With regard to the dorsal rims,interdorsum originated first,whereas dorsal furrow originated independently twice on the basis of interdorsum.Probably Hesslandona may represent a polyphyletic group,whereas Vestrogothia a monophyletic group.

  10. Cable Bacteria in Freshwater Sediments.

    Science.gov (United States)

    Risgaard-Petersen, Nils; Kristiansen, Michael; Frederiksen, Rasmus B; Dittmer, Anders Lindequist; Bjerg, Jesper Tataru; Trojan, Daniela; Schreiber, Lars; Damgaard, Lars Riis; Schramm, Andreas; Nielsen, Lars Peter

    2015-09-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures and electric fields indicated electron transfer between vertically separated anodic and cathodic half-reactions. Fluorescence in situ hybridization revealed the presence of Desulfobulbaceae filaments. In addition, in situ measurements of oxygen, pH, and electric potential distributions in the waterlogged banks of Giber Å demonstrated the presence of distant electric redox coupling in naturally occurring freshwater sediment. At the same site, filamentous Desulfobulbaceae with cable bacterium morphology were found to be present. Their 16S rRNA gene sequence placed them as a distinct sister group to the known marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary origin of the cable phenotype within Desulfobulbaceae with subsequent diversification into a freshwater and a marine lineage.

  11. Precambrian clastic sedimentation systems

    Science.gov (United States)

    Eriksson, P. G.; Condie, K. C.; Tirsgaard, H.; Mueller, W. U.; Altermann, W.; Miall, A. D.; Aspler, L. B.; Catuneanu, O.; Chiarenzelli, J. R.

    1998-09-01

    The unique and evolving nature of the Precambrian geological environment in many ways was responsible for significant differences between Precambrian clastic sedimentary deposits and their Phanerozoic-modern equivalents. Some form of plate tectonics, with rapid microplate collisions and concomitant volcanic activity, is inferred to have led to the formation of greenstone belts. Explosive volcanism promoted common gravity-flow deposits within terrestrial greenstone settings, with braided alluvial, wave/storm-related and tidal coastline sediments also being preserved. Late Archaean accretion of greenstone terranes led to emergence of proto-cratons, where cratonic and rift sedimentary assemblages developed, and these became widespread in the Proterozoic as cratonic plates stabilised. Carbonate deposition was restricted by the paucity of stable Archaean terranes. An Early Precambrian atmosphere characterised by greenhouse gases, including CO 2, in conjunction with a faster rotation of the Earth and reduced albedo, provide a solution to the faint young Sun paradox. As emergent continental crust developed, volcanic additions of CO 2 became balanced by withdrawal due to weathering and a developing Palaeoproterozoic microbial biomass. The reduction in CO 2, and the photosynthetic production of O 2, led to aerobic conditions probably being achieved by about 2 Ga. Oceanic growth was allied to atmospheric development, with approximately 90% of current ocean volume being reached by about 4 Ga. Warm Archaean and warm, moist Palaeoproterozoic palaeoclimates appear to have become more arid after about 2.3 Ga. The 2.4-2.3 Ga Huronian glaciation event was probably related to continental growth, supercontinent assembly and weathering-related CO 2 reduction. Despite many analogous features among both Precambrian and younger sedimentary deposits, there appear to be major differences as well. Two pertinent examples are rare unequivocal aeolian deposits prior to about 1.8 Ga and an

  12. Sediment transport under breaking waves

    DEFF Research Database (Denmark)

    Christensen, Erik Damgaard; Hjelmager Jensen, Jacob; Mayer, Stefan

    2000-01-01

    The sediment transport in the surf zone is modelled by combining a Navier-Stokes solver, a free surface model, a turbulence model, and a sediment transport model. The flow solver is based on the finite volume technique for non-orthogonal grids. The model is capable of simulating the turbulence...... generated at the surface where the wave breaks as well as the turbulence generated near the bed due to the wave-motion and the undertow. In general, the levels of turbulent kinetic energy are found to be higher than experiments show. This results in an over prediction of the sediment transport. Nevertheless......, some qualitative features have been modelled with success such as the onshore transport under plunging breakers and offshore transport under spilling breakers....

  13. Modeling microalgal flocculation and sedimentation.

    Science.gov (United States)

    Salim, S; Gilissen, L; Rinzema, A; Vermuë, M H; Wijffels, R H

    2013-09-01

    In this study, a combined flocculation and sedimentation model is developed. The model predicts the time needed to reach a desired concentration of microalgal suspension in a sedimentation tank. The concentration of the particles as function of the time and the position in the tank is described. The model was validated with experimental data for Ettlia texensis. The concentration changes measured in time at different heights in the sedimentation vessel corresponded well with model predictions. The model predicts that it takes 25 h to reach a final concentration of 5.2 gDW L(-1), when the initial concentration is 0.26 gDW L(-1) and the tank height is 1m. This example illustrates the use of this model for the design of the settling tank needed for pre-concentration of microalgal biomass before further dewatering.

  14. Beryllium-10 in continental sediments

    Energy Technology Data Exchange (ETDEWEB)

    Brown, L.; Sacks, I.S.; Tera, F. (Carnegie Institution of Washington, DC (USA). Dept. of Terrestrial Magnetism); Klein, J.; Middleton, R. (Pennsylvania Univ., Philadelphia (USA). Dept. of Physics)

    1981-11-01

    The concentration of /sup 10/Be has been measured in 10 samples taken from a transect of surface sediments beginning in the Atchafalaya River and extending across the Bay 136 km into the Gulf of Mexico. If corrected for a lower retentivity of sand for Be, they have a concentration that is constant within 13%. This concentration is about an order of magnitude smaller than that of deep ocean sediments. For comparison, measurements of /sup 10/Be in rainwater, in a sample of soil and in a deep ocean core were made.

  15. Sediment reworking rates in deep sediments of the Mediterranean Sea

    Energy Technology Data Exchange (ETDEWEB)

    Barsanti, M., E-mail: mattia.barsanti@enea.it [ENEA, Marine Environment Research Centre, La Spezia (Italy); Delbono, I., E-mail: ivana.delbono@enea.it [ENEA, Marine Environment Research Centre, La Spezia (Italy); Schirone, A., E-mail: antonio.schirone@enea.it [ENEA, Marine Environment Research Centre, La Spezia (Italy); Langone, L., E-mail: leonardo.langone@bo.ismar.cnr.it [CNR, ISMAR Istituto di Scienze Marine, U.O.S. Bologna (Italy); Miserocchi, S., E-mail: stefano.miserocchi@bo.ismar.cnr.it [CNR, ISMAR Istituto di Scienze Marine, U.O.S. Bologna (Italy); Salvi, S., E-mail: stefano.salvi@enea.it [ENEA, Research Centre Brasimone, Camugnano (Italy); Delfanti, R., E-mail: roberta.delfanti@enea.it [ENEA, Marine Environment Research Centre, La Spezia (Italy)

    2011-07-01

    Different pelagic areas of the Mediterranean Sea have been investigated in order to quantify physical and biological mixing processes in deep sea sediments. Herein, results of eleven sediment cores sampled at different deep areas (> 2000 m) of the Western and Eastern Mediterranean Sea are presented. {sup 210}Pb{sub xs} and {sup 137}Cs vertical profiles, together with {sup 14}C dating, are used to identify the main processes characterising the different areas and, finally, controlling mixing depths (SML) and bioturbation coefficients (D{sub b}). Radionuclide vertical profiles and inventories indicate that bioturbation processes are the dominant processes responsible for sediment reworking in deep sea environments. Results show significant differences in sediment mixing depths and bioturbation coefficients among areas of the Mediterranean Sea characterised by different trophic regimes. In particular, in the Oran Rise area, where the Almeria-Oran Front induces frequent phytoplankton blooms, we calculate the highest values of sediment mixing layers (13 cm) and bioturbation coefficients (0.187 cm{sup 2} yr{sup -1}), and the highest values of {sup 210}Pb{sub xs} and {sup 137}Cs inventories. Intermediate values of SML and D{sub b} ({approx} 6 cm and {approx} 0.040 cm{sup 2} yr{sup -1}, respectively) characterise the mesothrophic Algero-Balearic basin, while in the Southern Tyrrhenian Sea mixing parameters (SML of 3 cm and D{sub b} of 0.011 cm{sup 2} yr{sup -1}) are similar to those calculated for the oligotrophic Eastern Mediterranean (SML of 2 cm and D{sub b} of {approx} 0.005 cm{sup 2} yr{sup -1}). - Research highlights: {yields} Physical and biological mixing processes in the Mediterranean Sea are investigated. {yields} Results of 11 sediment cores in deep areas of the Mediterranean Sea are shown. {yields} {sup 210}Pb{sub xs} and {sup 137}Cs vertical profiles are analysed. {yields} New data on {sup 210}Pb and {sup 137}Cs inventories of Mediterranean deep sediments are

  16. Biota-Sediment Accumulation Factor Data

    Data.gov (United States)

    U.S. Environmental Protection Agency — The Biota-Sediment Accumulation Factor contains approximately 20,000 biota-sediment accumulation factors (BSAFs) from 20 locations (mostly Superfund sites) for...

  17. STUDY ON TOTAL SEDIMENT TRANSPORT BY FLOW

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Total sediment transport under the action of flow includes generally three forms of sediment transport, suspended load, density current and bed load. How to realize simultaneously these three forms of sediment movement in an identical physical model was studied in this paper. For the suspended load, fall and pickup similarities were used to design sediment gradation, and similarities of sediment-carrying capacity and scouring and depositing time were be insured. For the density current its occurrence condition should be similar, and similarities of sediment concentration and depositing time were insured. For the bed load, sediment gradation was designed by the similarity of incipient motion, and similarities of sediment discharge and scouring and depositing time were satisfied. And a physical model test was conducted.

  18. Longshore sediment transport along the Indian coast

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    An empirical sediment transport model has been developed based on longshore energy flux equation. Ship reported waves, published in Indian Daily Weather Reports, are compiled for 19 y and used for estimation of sediment transport. Annual gross...

  19. Green PCB Remediation from Sediment Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The GPRSS technology is an in situ remediation technique for PCB-contaminated sediments. The technique provides an effective and safe method for sediment cleanup...

  20. Gradation effects in sediment transport

    NARCIS (Netherlands)

    de Meijer, RJ; Bosboom, J; Cloin, B; Katopodi, [No Value; Kitou, N; Koomans, RL; Manso, F

    2002-01-01

    To determine the effects of grain size and density gradation in oscillatory sheet-flow, experiments are conducted in an oscillating water tunnel. A formal derivation of a schematised transport model shows that the transport rates per sediment fraction can be determined with and without the assumptio

  1. SEDIMENT TRANSPORT AND STREAM POWER

    Institute of Scientific and Technical Information of China (English)

    Chih Ted YANG

    2002-01-01

    This paper provides a step-by-step derivation of the sediment transport functions by Engelund and Hansen (1967) and by Ackers and White (1973). The theoretical derivations demonstrate that these two functions are closely related to Bagnold's (1966) stream power and efficiency concepts.

  2. Flocculation Dynamics of cohesive sediment

    NARCIS (Netherlands)

    Maggi, F.

    2005-01-01

    Cohesive sediment suspended in natural waters is subject not only to transport and deposition processes but also to reactions of flocculation, \\textit{i.e.} aggregation of fine particles, and breakup of aggregates. Although aggregation and breakup occur at small and very small length scales compared

  3. Sediment availability on burnt hillslopes

    Science.gov (United States)

    Nyman, Petter; Sheridan, Gary; Moody, John; Smith, Hugh; Noske, Philip; Lane, Patrick

    2013-04-01

    In general, erosion has been modeled as being proportional to some form of energy or force (such as shear stress or stream power) with the proportionality constant being erodibility, which is a characterization of sediment availability. It is unclear if erodibility is constant with depth on recently burnt hillslopes. This study used both field- and laboratory based experiments to quantify sediment availability as a depth-dependent parameter on burnt hillslopes. An explicit representation of fire-effect on sediment availability was achieved by assuming that fire-effects produce a non-cohesive soil layer of variable depth. This depth is characterized as a probability density function with a single parameter that changed during recovery (0-3 years) as the available soil was depleted. Measurements in southeastern Australia found that initially after a wildfire the hillslope had a layer (0.75-0.91 cm in depth) of non-cohesive soil, which represented 97-117 t/ha of transport limited sediment. The thickness of this layer decreased exponentially with time since the wildfire. Additional results showed that fine roots (soils for depths soil depth and root density accounted for ~60 % of variation in the erodibility at soil depths soil properties (% silt and clay in particular) became more important as predictors of erodibility. The results are organized into a conceptual framework for modeling fire-effects on sediment availability for systems with low and high pre-fire erodibility. The fire-effect produces an equal depth of non-cohesive soil for both systems but this represents a greater perturbation for systems with low pre-fire erodibility than for those systems with a high pre-fire erodibility.

  4. Upstream sediment input effects on experimental dune trough scour in sediment mixtures

    NARCIS (Netherlands)

    Kleinhans, M.G.

    2005-01-01

    Understanding causes of dune irregularity, especially dune trough scour, is important for the modeling of vertical sorting of sediment mixtures in morphological models of rivers with sediment mixtures. Sediment in dunes is generally sorted in a fining-upward manner, which affects the sediment transp

  5. Sediment-accumulatie in transportleidingen af waterproductiebedrijven

    NARCIS (Netherlands)

    Beverloo, H.; Vreeburg, J.H.G.; Zwaga, A.

    2014-01-01

    In drinkwatertransportleidingen hoopt zich sediment op, ondanks het feit dat de maximale stroomsnelheid hoger is dan de snelheid die voor distributieleidingen zelfreinigend is. Opwervelend sediment zorgt voor klachten over de kwaliteit van het drinkwater. Het sediment accumuleert vooral dicht bij he

  6. Palaeoenvironmental and geochemical approach of Archaeocyath-rich facies from Lower Cambrian of Western Gondwana margin at Central Iberian Zone (Urda, Toledo Mountains, Spain)

    Science.gov (United States)

    Menéndez, Silvia; Rodríguez-Martínez, Marta; Moreno-Eris, Elena; Perejón, Antonio; Reitner, Joachim

    2010-05-01

    Archaeocyath-rich facies are located in a quarry close to Urda village, at Toledo Mountains, Spain. The outcrops belong to the Caliza de los Navalucillos Formation and they record a considerably high diverse archaeocyath assemblage in the Lower Cambrian successions from the Central Iberian Zone (Julivert et al. 1972 [1974]). In fact, it is first time recorded the presence of Agyrekocyathus, Dokidocyathus, and Plicocyathus in the Central Iberian Zone. Therefore Plicocyathus is no longer exclusive to biozone VI in Spain. The presence of Anthomorpha is characteristic for the early Botomian, presently early Stage 4 (ICS, 2009), and the assemblage corresponds to the biozone VII (late Ovetian, following the biozonation of Perejón & Moreno-Eiris, 2006). The fossiliferous part of the succession is formed by seven lithofacies, all of them tectonically folded and with a low grade metamorphic overprint. They are comprised by two main groups of facies: (a) mound-shaped to massive lithofacies (A1, A2, A3, A4) and (b) massive to bedded and nodular lithofacies (B1, B2, B3). Archaeocyaths occur in several facies: (A1) mound-shaped white marble with irregular to stromatactoid cavities; (A2) massive mottled white to grey limestone; (A3) massive grey limestone with slumps levels; (A4) massive archaeocyath-rich orange limestone; as well as in carbonate nodules embedded in siltstones and cherts (B1, B2 and B3). The best preserved assemblage comes from the nodule record, where fossils are partially pyritized. This type of preservation is exceptional and has never been described before. XRD and wavelength-dispersive electron microprobe analyses reveal the presence of pyrite and pyrrotine partially altered to iron oxides and hydroxides (hematite and goethite) surrounding the archaeocyath cups. In Central Iberian Zone, the development of mounds and nodular facies like those described here is unusual, although the Botomian marks the peak for Early Cambrian archaeocyathan-microbial mounds

  7. The Neoproterozoic-Cambrian Paraguay Belt, central Brazil: Part I - New structural data and a new approach on the regional implications

    Science.gov (United States)

    Silva, Luiz José Homem D'el-Rey; Walde, Detlef Hans-Gerd; Saldanha, Davi Oliveira

    2016-04-01

    Together with the Araguaia and Brasília belts, the Paraguay belt forms in central Brazil, the Tocantins Province that is one of the largest orogens of western Gondwana. The Corumbá area occupies the site where the northern and southern parts of the Paraguay belt form, together with the Chiquitos-Tucavaca aulacogen (stretching E-W in the adjacent Bolivian territory) an R-R-R basin system opened-filled in the ~ 700/650-540 Ma interval within the Amazon-Rio Apa paleo-continent. The sedimentary (volcanic) rocks of the Jacadigo and Corumbá Groups found around the Corumbá city record part of the Neoproterozoic-Cambrian passive margin precursor of the Paraguay belt. Our pioneer structural analysis reveals that these rocks experienced progressive deformation (phases D1-D2-D3) and low-grade metamorphism during the Brasiliano Cycle (540-513 Ma). The crystalline basement was also involved, according to structural data and K-Ar ages in the literature. The paleo-passive margin was thickened during the D1-D2 deformation and was lately shortened (D3) in two orthogonal directions, SE-NW (D3P) and SW-NE (D3T). Developed co-axially and verging to NW, D1-D2-D3P structures record the closure of the basin precursor of the Paraguay belt, whereas D3T structures seem related to the inversion of the aulacogen. Although the tectonic transport to NW, as observed in the Corumbá area, matches the reported transport of Paraguay belt's supracrustal rocks towards the eastern margin of the Rio Apa block and Araguaia belt's rocks towards the Amazon craton, the transport direction is opposite in other parts of the Paraguay belt. Our comprehensive discussion of these facts brings to light profound regional implications.

  8. Geochemistry of Platinum Group and Rare Earth Elements of the Polymetallic Layer in the Lower Cambrian,Weng'an,Guizhou Province

    Institute of Scientific and Technical Information of China (English)

    FU Yong; WU Chaodong; GUAN Ping; QU Wenjun; CHEN Jiafu

    2009-01-01

    The black shales of the Lower Cambrian Niutitang Formation in Weng'an.on the Yangtze platform of south China,contain voluminous polymetallic sulfide deposits.A comprehensive geochemical investigation of trace,rare earth,and platinum group elements(PGE)has been undertaken in order to discuss its ore genesis and correlation with the tectono.depositional setting.The ore-bearing layers enrich molybdenum(Mo),nickeI(Ni),vanadium(V),lead(Pb),strontium(Sr), bariam(Ba),uranium(U),arsenic(As),and rare earth elements(REE)in abundance.High uranium/thorium(U/Th)ratios(U/Th>1)indicated that mineralization was mainly influenced by the hydrothermal process.The δU value Was above 1.9.showing a reducing sedimentary condition.The REE patterns showed high enrichment in Iight rare earth elements (LREE)(heavy rare earth elements (HREE)(LREE/HREE=5-17),slightly negative europium(EU)and cerium(Ce)anomalies(δEu=0.81-0.93).and positive Ce anomalies(δCe=0.76-1.12).PGE abundance was characterized by the PGE-type distribution patterns,enriching platinum(Pt),palladium(Pd),ruthenium(RuJ and osmium(Os).The Pt,Pd ratio was 0.8.which is close to the ratios of seawater and ultramafic rocks.AII of these geochemical features suggest that the mineralization was triggered by hydrothermal activity in an extensionai setting in the context of break-up of the Rodinian supercontinent.

  9. Petroleum source rock evaluation of the Alum and Dictyonema Shales (Upper Cambrian-Lower Ordovician) in the Baltic Basin and Podlasie Depression (eastern Poland)

    Science.gov (United States)

    Kosakowski, Paweł; Kotarba, Maciej J.; Piestrzyński, Adam; Shogenova, Alla; Więcław, Dariusz

    2017-03-01

    We present geochemical characteristics of the Lower Palaeozoic shales deposited in the Baltic Basin and Podlasie Depression. In the study area, this strata are represented by the Upper Cambrian-Lower Ordovician Alum Shale recognized in southern Scandinavia and Polish offshore and a equivalent the Lower Tremadocian Dictyonema Shale from the northern Estonia and the Podlasie Depression in Poland. Geochemical analyses reveal that the Alum Shale and Dictyonema Shale present high contents of organic carbon. These deposits have the best source quality among the Lower Palaeozoic strata, and they are the best source rocks in the Baltic region. The bituminous shales complex has TOC contents up to ca. 22 wt%. The analysed rocks contain low-sulphur, oil-prone Type-II kerogen deposited in anoxic or sub-oxic conditions. The maturity of the Alum and Dictyonema Shales changes gradually, from the east and north-east to the west and south-west, i.e. in the direction of the Tornquist-Teisseyre Zone. Samples, located in the seashore of Estonia and in the Podlasie region, are immature and in the initial phase of "oil window". The mature shales were found in the central offshore part of the Polish Baltic Basin, and the late mature and overmature are located in the western part of the Baltic Basin. The Alum and Dictyonema Shales are characterized by a high grade of radioactive elements, especially uranium. The enrichment has a syngenetic or early diagenetic origin. The measured content of uranium reached up to 750 ppm and thorium up to 37 ppm.

  10. Evidence of syntectonic tephrites with nepheline in the Sidi Saïd Maâchou Cambrian basin (coastal Meseta, Morocco; geodynamic implications

    Directory of Open Access Journals (Sweden)

    El Hatimi, N.

    2009-12-01

    Full Text Available Based on a combined structural, petrographic, and geochemical analysis, a new interpretation of the basic magmatism of Sidi Saïd Maâchou (coastal Meseta in two stages of emplacement is proposed. The first stage is characterized by transitional pyroclastic flows that have accompanied the opening of the West-Mesetian basin, during the Cambrian; the second stage is made of dykes of basalts, dolerites, and tephrites bearing nepheline. The emplacement of this undersaturated alkaline magma is associated to a sinistral submeridian shear zone which has been activated at the end of the Caledonian orogenesis, by a mantellic advection.

    Basée sur des critères structuraux, pétrographiques et géochimiques, une réinterprétation du magmatisme basique de Sidi Saîd Maâchou (meseta côtière en deux stades de mise en place est proposée. Le premier stade est caractérisé par des coulées pyroclastiques transitionnelles accompagnant l’ouverture du bassin ouest mésétien au Cambrien. Le second stade, de nature fissural, comprend des basaltes, dolérites et téphrites à néphéline spécifiques d’un magmatisme alcalin sous-saturé. La mise en place de ce dernier est associée à un couloir de cisaillement senestre subméridien activé à la fin de l’orogenèse calédonienne, engendrant un flux géothermique élevé.

  11. The Ocean Redox State Evolution and Its Controls during the Cambrian Series 1-2:Evidence from Lijiatuo Section, South China

    Institute of Scientific and Technical Information of China (English)

    Lei Xiang; Chunfang Cai; Xunyun He; Lei Jiang; Yuyang Yuan; Tiankai Wang; Lianqi Jia; Lei Yu

    2016-01-01

    ABSTRACT:Well-exposed Lijiatuo Section was chosen to explore the temporal evolution and controls of the oceanic redox state, primary productivity and seawater sulfate levels during the Cambrian Series 1–2, South China. This section consists of Xiaoyanxi Formation (Fm.) mudstones and Liuchapo Fm. cherts that deposited in the slope and basin environment. Five oxic-anoxic cycles were identified based on V/Sc, Th/U and the enrichment factors of Mo, U, V, Ni and Cu. The Middle-Upper Liuchapo Fm. and the Middle Xiaoyanxi Fm. were deposited under oxic-suboxic conditions, and the rest of the strata were under anoxic conditions. The Re/Mo ratio demonstrated that the oxic-suboxic conditions in the Middle Xiaoyanxi Fm. were accompanied by transient sulfidic conditions, and the rest of the section was underanoxic and non-sulfidic conditions. All the TOC and the enrichment factors of Ba, Ni, Cu, Zn and Cd demonstrated that both the sinking and burial flux of organic matter (OM) in Liuchapo Fm. were lower than that in the overlying Xiaoyanxi Fm. The highest sinking and burial flux of OM in the Xiaoyanxi Fm. appeared at its lower parts; however, the lowest sinking and burial flux of OM in the Xiaoyanxi Fm. appeared in its middle parts. TOC/TS, TS and the vertical trend ofδ34Spy demonstrated that the seawater was dominated by low oceanic sulfate levels, which resulted in the absence of free H2S. The rise of the atmospheric oxygen content may be the principal driver for the associated, transient suboxic-oxic and nearly sulfidic environment in the middle Xiaoyanxi Fm.

  12. Petroleum source rock evaluation of the Alum and Dictyonema Shales (Upper Cambrian-Lower Ordovician) in the Baltic Basin and Podlasie Depression (eastern Poland)

    Science.gov (United States)

    Kosakowski, Paweł; Kotarba, Maciej J.; Piestrzyński, Adam; Shogenova, Alla; Więcław, Dariusz

    2016-05-01

    We present geochemical characteristics of the Lower Palaeozoic shales deposited in the Baltic Basin and Podlasie Depression. In the study area, this strata are represented by the Upper Cambrian-Lower Ordovician Alum Shale recognized in southern Scandinavia and Polish offshore and a equivalent the Lower Tremadocian Dictyonema Shale from the northern Estonia and the Podlasie Depression in Poland. Geochemical analyses reveal that the Alum Shale and Dictyonema Shale present high contents of organic carbon. These deposits have the best source quality among the Lower Palaeozoic strata, and they are the best source rocks in the Baltic region. The bituminous shales complex has TOC contents up to ca. 22 wt%. The analysed rocks contain low-sulphur, oil-prone Type-II kerogen deposited in anoxic or sub-oxic conditions. The maturity of the Alum and Dictyonema Shales changes gradually, from the east and north-east to the west and south-west, i.e. in the direction of the Tornquist-Teisseyre Zone. Samples, located in the seashore of Estonia and in the Podlasie region, are immature and in the initial phase of "oil window". The mature shales were found in the central offshore part of the Polish Baltic Basin, and the late mature and overmature are located in the western part of the Baltic Basin. The Alum and Dictyonema Shales are characterized by a high grade of radioactive elements, especially uranium. The enrichment has a syngenetic or early diagenetic origin. The measured content of uranium reached up to 750 ppm and thorium up to 37 ppm.

  13. A normalised seawater strontium isotope curve. Possible implications for Neoproterozoic-Cambrian weathering rates and the further oxygenation of the Earth

    Energy Technology Data Exchange (ETDEWEB)

    Shields, G.A. [Muenster Univ. (Germany). Geologisch-Palaeontologisches Inst.

    2007-07-01

    The strontium isotope composition of seawater is strongly influenced on geological time scales by changes in the rates of continental weathering relative to ocean crust alteration. However, the potential of the seawater {sup 87}Sr/{sup 86}Sr curve to trace globally integrated chemical weathering rates has not been fully realised because ocean {sup 87}Sr/{sup 86}Sr is also influenced by the isotopic evolution of Sr sources to the ocean. A preliminary attempt is made here to normalise the seawater {sup 87}Sr/{sup 86}Sr curve to plausible trends in the {sup 87}Sr/{sup 86}Sr ratios of the three major Sr sources: carbonate dissolution, silicate weathering and submarine hydrothermal exchange. The normalised curve highlights the Neoproterozoic-Phanerozoic transition as a period of exceptionally high continental influence, indicating that this interval was characterised by a transient increase in global weathering rates and/or by the weathering of unusually radiogenic crustal rocks. Close correlation between the normalised {sup 87}Sr/{sup 86}Sr curve, a published seawater {delta}{sup 34}S curve and atmospheric pCO{sub 2} models is used here to argue that elevated chemical weathering rates were a major contributing factor to the steep rise in seawater {sup 87}Sr/{sup 86}Sr from 650 Ma to 500 Ma. Elevated weathering rates during the Neoproterozoic-Cambrian interval led to increased nutrient availability, organic burial and to the further oxygenation of Earth's surface environment. Use of normalised seawater {sup 87}Sr/{sup 86}Sr curves will, it is hoped, help to improve future geochemical models of Earth System dynamics. (orig.)

  14. Paleomagnetic study of Cambrian Ordovician rocks in the Eastern Precordillera of Argentina: some constraints on the Andean uplift of this block

    Science.gov (United States)

    Rapalini, A. E.; Bordonaro, O.; Berquo, T. S.

    2000-11-01

    A paleomagnetic study on several carbonatic units (limestones to dolomites) of the Argentine Precordillera, spanning the Middle Cambrian to Arenig, is reported. Sampling was done at 23 sites (140 samples) in five localities of the Eastern Precordillera of San Juan province: Zonda (1), Juan Pobre (2) and La Flecha (3) creeks, Loma Redonda (4) and Cerro Pedernal de los Berros (5). Standard AF and thermal demagnetization indicated two different magnetic behaviors. Samples from localities 1 and 2 showed a single, post-tectonic magnetic component attributed to a Recent viscous or chemical remagnetization. Samples from localities 3 to 5 showed two magnetic components: a low unblocking temperature (350°C) magnetization coincident with that found at the previous localities and a high temperature one (up to 500°C). This second component was also found to be post-folding (post-Devonian?) and its in situ mean direction is Dec: 277.1°, Inc: 69.4, α95: 9.3°, N=10. This is not consistent with any expected direction for the study area between Carboniferous and Recent times. It is therefore inferred that the rocks carrying it underwent substantial tectonic rotation since its recording. Comparison with the magnetization carried by similar Early Ordovician limestones in the Central Precordillera and the San Rafael Block, and assigned to a Permian remagnetizing event, suggests that the same process affected the carbonatic rocks in the Eastern Precordillera and, therefore, the age of the component is likely Permian. Restoration of the in situ mean direction to the expected direction for a Permian remagnetization can be obtained by a 40° ccw rotation around an axis plunging 30° to N30°E. This is compatible with uplifting of the Eastern Precordillera as a series of quasi-rigid blocks along a major E dipping N to NE backthrust during the Andean orogeny.

  15. Ediacaran to Cambrian magmatic suites in the Rio Grande do Norte domain, extreme Northeastern Borborema Province (NE of Brazil): Current knowledge

    Science.gov (United States)

    do Nascimento, Marcos Antonio Leite; Galindo, Antonio Carlos; de Medeiros, Vladimir Cruz

    2015-03-01

    The Ediacaran-Cambrian plutonic activity is one of the most important geological features of the Rio Grande do Norte Domain (Borborema Province, NE Brazil). It is represented by several batholiths, stocks and dykes. Based on the petrographic, geochemical and geochronological characteristic of different rocks, this plutonic activity can be grouped in six separate suites: shoshonitic (Shos), porphyritic high-K calc-alkaline (PHKCalcAlk), equigranular high K calc-alkaline (EHKCalcAlk), calc-alkaline (CalcAlk), alkaline (Alk) and charnockitic alkaline (ChAlk). Geochemically, the Shos, CalcAlk and Alk suites are differentiated from the others, while ChAlc can be distinguished from the others in some diagrams. The greatest difficulty lies in distinguishing between the chemically similar PHKCalcAlk and EHKCalcAlk. To this end, existing geochronological data as well as related petrographic and textural field aspects may be used to distinguish the two mentioned suites (PHKCalcAlk and EHKCalcAlk). Petrographically, the Shos suite has composition between gabbro/diorite and quartz monzonite. Monzogranites (with subordinate granodiorites and quartz monzonites) predominate in both PHKCalcAlk and EHKCalcAlk. Calc is composed of granodiorites to tonalites. Alc is formed by alkali feldspar granites (with subordinate alkali feldspar quartz syenites and syenogranites), whereas ChAlc has quartz mangerites and charnockites. The suites were emplaced between the Ediacaran (635-541 Ma) and Cambrian (541-485 Ma), predominantly in the Ediacaran, based on 34 U-Pb datings (zircon, titanite, monazite and columbite-tantalite), 17 Rb-Sr (whole rock) and 1 Sm-Nd (total rock and mineral) internal isochrons. The Shos suite has U-Pb ages varying from 599 ± 16 (Poço Verde pluton) to 579 ± 7 (Acari and São João do Sabugi plutons), slightly older than those of the PHKCalcAlk suite, which ranges between 591 ± 4 Ma (Totoró pluton) and 544 ± 7 Ma (São José de Espinharas pluton). The Calc

  16. Density gradation in cross-shore sediment transport

    NARCIS (Netherlands)

    Koomans, RL; de Meijer, RJ

    2004-01-01

    One of the fundamental properties of a coastline is its sediment composition. Coastal sediments are rarely composed of one type of sediment. Due to these differences, the sediments are sorted on the beach and foreshore. The effect of density variations of the sediment on coastal sediment transport h

  17. Les argiles bleues du Cambrien inférieur de Saint-Pétersbourg et leur fissuration. Implications pour des stockages souterrainsLower Cambrian Saint Petersburg blue clays and their fissuration. Implication for underground stages

    Science.gov (United States)

    Arnould, Marcel; Boisson, Jean-Yves; Ivanov, Ivan P.

    2002-12-01

    The Lower Cambrian Saint Petersburg blue clays are composed of predominant illite and chlorite, sometimes accompanied by kaolinite. The <0.1 μm fraction has a high content of illite-smectite mixed layers. Particle-size distribution is more than 50% of clay particles and about 30% of silts. These blue clays correspond to plastic (and soft) clays; they may be compared to the Callovian clays of Bure (France), where storage of natural waste is envisaged. To cite this article: M. Arnould et al., C. R. Geoscience 334 (2002) 1135-1140.

  18. Sediment Transport in Rivers and Coastal Waters

    Institute of Scientific and Technical Information of China (English)

    杨树清; 余建星; 王元战

    2003-01-01

    Following Bagnold′s approach, a relationship between sediment transport and energy dissipation is developed. The major assumption made in the study is that the near bed velocity plays a dominant role in the process of sediment transport. A general relationship between energy dissipation and sediment transport is first proposed. Then the equations for total sediment transport are derived by introducing the appropriate expression of energy dissipation rate under different conditions, such as open channel flows, combination of wave and current, as well as longshore sediment transport. Within the flows investigated, the derived relationships are fairly consistent with the available data over a wide range of conditions.

  19. A Sediment Budget Case Study: Comparing Watershed Scale Erosion Estimates to Modeled and Empirical Sediment Loads

    Science.gov (United States)

    McDavitt, B.; O'Connor, M.

    2003-12-01

    The Pacific Lumber Company Habitat Conservation Plan requires watershed analyses to be conducted on their property. This paper summarizes a portion of that analysis focusing on erosion and sedimentation processes and rates coupled with downstream sediment routing in the Freshwater Creek watershed in northwest California. Watershed scale erosion sources from hillslopes, roads, and channel banks were quantified using field surveys, aerial photo interpretation, and empirical modeling approaches for different elements of the study. Sediment transport rates for bedload were modeled, and sediment transport rates for suspended sediment were estimated based on size distribution of sediment inputs in relation to sizes transported in suspension. Recent short-term, high-quality estimates of suspended sediment yield that a community watershed group collected with technical assistance from the US Forest Service were used to validate the resulting sediment budget. Bedload yield data from an adjacent watershed, Jacoby Creek, provided another check on the sediment budget. The sediment budget techniques and bedload routing models used for this study generated sediment yield estimates that are in good agreement with available data. These results suggest that sediment budget techniques that require moderate levels of fieldwork can be used to provide relatively accurate technical assessments. Ongoing monitoring of sediment sources coupled with sediment routing models and reach scale field data allows for predictions to be made regarding in-channel sediment storage.

  20. Modeling Transport of Flushed Reservoir Sediment

    Science.gov (United States)

    Dubinski, I. M.

    2014-12-01

    Drawdown flushing of a reservoir is often part of a reservoir sediment management program. Flushing can deliver higher than normal sediment loads to the river channel located downstream of a reservoir. The flushed sediment may contain a higher proportion of finer sediment than what was delivered to a channel prior to the presence of the reservoir. The extent of long-term impacts caused by the flushed sediment on the channel morphology and habitat will in part depend on the residence time of the sediment within the channel. In this study we used MIKE 21C to model the fate of flushed sediment through a river channel where the bed material consists of an armoring layer of gravels overlying finer sediment. MIKE 21C is a two-dimensional curvilinear morphological model for rivers developed by DHI. Curvilinear means that the model grid may curve to better follow the channel and flow direction, for example in a meandering channel. Multiple bed material layers are included in the model to represent the armoring and underlying layers existing in the bed separately from the overlying flushed sediment. These layers may also mix. The nature of the interactions between these two layers helps regulate transport and deposition of the flushed sediment, thus are critical to assessing the fate of the flushed sediment and associated potential impacts.

  1. NUMERICAL SIMULATION OF SEDIMENT RELEASE FROM RESERVOIRS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    For the computation of the sediment quantity released from reservoirs, a vertical two-dimensional hydrodynamic model is combined with a sediment transport model. The hydrodynamic model is based on the equations of mass and momentum conservation along with a k - ε model for closure of the Reynolds stresses. The sediment transport model is based on the convection-diffusion equation of sediment concentration and the sediment continuity equation. Both the hydrodynamic and sediment transport models are developed in a boundary-fitted curvilinear co-ordinate system. Comparison of the predicted mean velocity field with laboratory results indicates that the present model captures most experimental trends with reasonable accuracy. Also good agreement is found in comparison of the sediment transport results for the numerical model and the experimental model.

  2. SEDIMENT TRANSPORT EXPERIMENTSIN UNSTEADY FLOWS

    Institute of Scientific and Technical Information of China (English)

    DE SUTTER R.; HUYGENS M.; VERHOEVEN R.

    2001-01-01

    By means of a test flume with semi-circular cross-section, bedload and suspended-sediment transport of non-cohesive material have been studied in transient flow. The experimental facility enables us to investigate the time evolution of friction and transport parameters. Preliminary measurements with a fixed bottom instead of a sediment bed yield a reliable assessment of flow and friction characteristics. Time sequence in unsteady flow of the relevant parameters is revealed. The influence of turbulence variation and shear stress variation on the transport is investigated. As existing transport equations are found to be in poor agreement with experimental data, a new "engineering" concept is constructed which relates friction velocity to transport.

  3. Vertical distribution of sediment concentration

    Institute of Scientific and Technical Information of China (English)

    Sai-hua HUANG; Zhi-lin SUN; Dan XU; Shan-shan XIA

    2008-01-01

    A simple formula is proposed to predict the vertical distribution of a suspended load concentration in a 2D steady turbulent flow.The proposed formula significantly improves the well-known Rouse formula where sediment concentration has an infinitely large value at the channel bottom and a zero value at the water surface.Based on this formula and the logarithmic ve-locity profile,a theoretical elementary function for the transport rate of a suspended load is developed.This equation improves the Einstein equation in which the unit-width suspended sediment discharge must be solved by numerical integration and a contra-diction between the lower limit of the integral and that of velocity distribution exists.

  4. MITIGATION OF SEDIMENTATION HAZARDS DOWNSTREAM FROM RESERVOIRS

    Institute of Scientific and Technical Information of China (English)

    Ellen WOHL; Sara RATHBURN

    2003-01-01

    Many reservoirs currently in operation trap most or all of the sediment entering the reservoir,creating sediment-depleted conditions downstream. This may cause channel adjustment in the form of bank erosion, bed erosion, substrate coarsening, and channel planform change. Channel adjustment may also result from episodic sediment releases during reservoir operation, or from sediment evacuation following dam removal. Channel adjustment to increased sediment influx depends on the magnitude, frequency, duration and grain-size distribution of the sediment releases, and on the downstream channel characteristics. Channel adjustment may occur as a change in substrate sizedistribution, filling of pools, general bed aggradation, lateral instability, change in channel planform,and/or floodplain aggradation. The increased sediment availability may alter aquatic and riparian habitat, reduce water quality, distribute adsorbed contaminants along the river corridor, and provide germination sites for exotic vegetation. Mitigation of these sedimentation hazards requires: (1)mapping grain-size distribution within the reservoir and estimating the grain-size distributions of sediment that will be mobilized through time; (2) mapping shear stress and sediment transport capacity as a function of discharge on the basis of channel units for the length of the river likely to be affected; (3) mapping potential depositional zones, and aquatic habitat and "acceptable losses," along the downstream channel, and comparing these volumes to the total sediment volume stored in the reservoir as a means of estimating total transport capacity required to mobilize reservoir sediment delivered to the channel; (4) designing discharge and sediment release regime (magnitude, frequency,duration) to minimize adverse downstream impacts; and (5) developing plans to remove, treat, contain,or track contaminants, and to restrict establishment of exotic vegetation. The North Fork Poudre River in Colorado is used to

  5. Monitoring of pollution in sediments

    Directory of Open Access Journals (Sweden)

    Renee I. Abdallah

    2016-03-01

    Full Text Available Polycyclic aromatic hydrocarbons (PAHs and aliphatic hydrocarbons (AHs were analyzed in surface sediments collected from Suez till Hurgharda coasts to establish baseline levels for various types of organic pollutants before the anticipated identification of anthropogenic activities, petrogenic and biogenic. AHs for all samples were dominated by unresolved complex mixture (UCM, and petrogenic mixed with biogenic sources. Results also revealed that sedimentary PAHs mainly originated from pyrolysis sources.

  6. Oligocene tectonics and sedimentation, California

    Science.gov (United States)

    Nilsen, T.H.

    1984-01-01

    During the Oligocene epoch, California was marked by extensive nonmarine sedimentation, in contrast to its pre-Oligocene and post-Oligocene depositional history. The Oligocene continental deposits are especially widespread in southern California and fill a number of small and generally partly restricted basins. Fluvial facies in many basins prograded over previously deposited lower Tertiary turbidites. Volcanism, from widespread centers, was associated with the nonmarine sedimentation. However, some basins remained marine and a few contain Oligocene turbidites and pelagic sediments deposited at bathyal depths. The Oligocene redbeds of California do not form a post-orogenic molasse sequence comparable to the Old Red Sandstone or Alpine molasse. They are synorogenic and record local uplift of basins and surrounding source areas. Late Cretaceous to contemporary orogenesis in California has been generally characterized by the formation of small restricted basins of variable depth adjacent to small upland areas in response to strike-slip faulting. Deposition of Oligocene redbeds was associated with climatic change from warm and humid to cold and semiarid, and a global lowering of sea level. Oligocene tectonism occurred during the transition from subduction of the Farallon Plate to initiation of the modern San Andreas transform system. However, the major influence that caused uplift, formation of fault-bounded basins, and extensive redbed deposition, especially in southern California, was the approach of the Pacific-Farallon spreading ridge to the western margin of California. ?? 1984.

  7. Sediment transport measurements: Chapter 5

    Science.gov (United States)

    Diplas, P.; Kuhnle, R.; Gray, J.; Glysson, D.; Edwards, T.; García, Marcelo H.

    2008-01-01

    Sediment erosion, transport, and deposition in fluvial systems are complex processes that are treated in detail in other sections of this book. Development of methods suitable for the collection of data that contribute to understanding these processes is a still-evolving science. Sediment and ancillary data are fundamental requirements for the proper management of river systems, including the design of structures, the determination of aspects of stream behavior, ascertaining the probable effect of removing an existing structure, estimation of bulk erosion, transport, and sediment delivery to the oceans, ascertaining the long-term usefulness of reservoirs and other public works, tracking movement of solid-phase contaminants, restoration of degraded or otherwise modified streams, and assistance in the calibration and validation of numerical models. This chapter presents techniques for measuring bed-material properties and suspended and bed-load discharges. Well-established and relatively recent, yet adequately tested, sampling equipment and methodologies, with designs that are guided by sound physical and statistical principles, are described. Where appropriate, the theory behind the development of the equipment and guidelines for its use are presented.

  8. Quantification of Gravel Rural Road Sediment Production

    Science.gov (United States)

    Silliman, B. A.; Myers Toman, E.

    2014-12-01

    Unbound rural roads are thought to be one of the largest anthropogenic sources of sediment reaching stream channels in small watersheds. This sediment deposition can reduce water quality in the streams negatively impacting aquatic habitat as well as impacting municipal drinking water sources. These roads are thought to see an increase in construction and use in southeast Ohio due to the expansion of shale gas development in the region. This study set out to quantify the amount of sediment these rural roads are able to produce. A controlled rain event of 12.7 millimeters of rain over a half hour period was used to drive sediment production over a 0.03 kilometer section of gravel rural road. These 8 segments varied in many characteristics and produced from 2.0 to 8.4 kilograms of sediment per 0.03 kilometers of road with the average production over the 8 segments being 5.5 kilograms of sediment. Sediment production was not strongly correlated with road segment slope but traffic was found to increase sediment production from 1.1 to 3.9 times as much sediment after traffic use. These results will help inform watershed scale sediment budgeting, and inform best management practices for road maintenance and construction. This study also adds to the understanding of the impacts of rural road use and construction associated with the changing land use from agricultural to natural gas extraction.

  9. Sediment load reduction in Chinese rivers

    Institute of Scientific and Technical Information of China (English)

    Cheng LIU; Jueyi SUI; Zhao-Yin WANG

    2008-01-01

    In this Paper,the changes in the annual runoff and sediment transport have been assessed by using the long term observation data from 10 gauging stations on 10 large rivers across China from far north to far south.It is found that the annual sediment yield has generally had a decreasing trend in the past half century.According to the changes in annual runoff and the sediment yield per area.rivers in China can be classified into the following three groups:1)rivers with decreasing annual sediment transport and stable runoff:2)rivers with both decreasing annual sediment transport and runoff and 3)rivers with greatly reduced annual sediment transport and decreasing annual runoff.The results indicate that,in all southern rivers(to the south of the Huaihe River including the Huaihe River),there has been little change in average annual runoff but a dramatic decrease in annual sediment transport.In the northern rivers.however,both the annual sediment yield and the runoff show significant evidence of reduction.To further investigate the recent changes in annual runoff and sediment transport.the short-term observation data from these 10 gauging stations in the recent 10 years have been assessed.Results show that both the annual sediment transport and the runoff have decreased significantly in the northern rivers in the past 10 years.Using the Yellow River at the Lijin Station as an example,the average annual runoff for the last 10 years is only 1/3 of the long term average value and the average annual sediment yield of the last 10 years is only 1/4 of the long term average value.More unusually,in the Yongding River the annual sediment yield has approached zero and the runoff has decreased significantly.In addition,the impacts of human activities on the changes in both runoff and sediment transport have been discussed.

  10. Geological Characteristics and Prospecting Potential of the Copper and Zinc Ore Deposits in the Sinian and Cambrian Systems of the Northern Daba Shan%北大巴山震旦寒武系中铜锌矿特征及找矿前景

    Institute of Scientific and Technical Information of China (English)

    龚银杰; 邹先武; 崔森; 夏杰; 张遵遵; 刘小龙; 刘劲松

    2013-01-01

    北大巴山属南秦岭造山带,在震旦-寒武纪形成一套以深水滞流盆地相为主的硅质炭质碎屑岩夹碳酸盐岩沉积.自开展地质大调查工作以来,该区域发现大量的铜锌矿点.根据矿体赋存位置、成因及矿石类型,铜锌矿可分为韧性剪切带型、石英脉型及岩浆岩接触变质型三种类型.通过对区内铜锌矿成矿规律的总结及成矿条件的分析,认为北大巴山具有良好的矿源层、完善的输导系统、丰富的储矿空间,因而具有较大的找矿潜力.指出深大断裂带附近的庄子沟组中碳酸盐岩为有利的赋矿部位.%The northern Daba Shan is part of the South Qinling orogenic belt, where deposited a set of siliceous - carbonaceous clastic rocks interbed-ded with carbonate sediments dominated by deep stagnant basin facies formed in the Sinian - Cambrian epoch. Previous exploration has discovered a large number of copper and zinc mineral occurrences or ore deposits, which are classified into the ductile shear zone type, quartz vein type and magmatic rocks contact metamorphic type according to the occurrence location, genesis of ore - bodies and types of the ores. Studies on the metallogenic conditions and regularities of these copper and zinc ore deposits suggest that the northern Daba Shan owns good source beds,perfect transporting and conducting systems and rich ore - storage space,indicating its large prospecting potential. It is pointed out that the of Zhuangzigou Fm. carbonate rocks adjacent to the deep and large faults are favorable ore - bearing loci.

  11. DISCOVERY OF MACROALGAE FROM THE CAMBRIAN TSINGHSUTUNG FORMATION OF GUIZHOU%贵州剑河八郎寒武系都匀阶“清虚洞组”宏观藻类化石的发现

    Institute of Scientific and Technical Information of China (English)

    傅晓平; 伍孟银; 赵元龙; 朱伟华; 杨宇宁

    2012-01-01

    文中首次报导贵州寒武系黔东统都匀阶“清虚洞组”(或乌训组)宏观藻类,计2属2种:环圈螺旋抚仙藻Fuxianospira gyrata Chen and Zhou,1997和云南中华细丝藻Sinocylindra yunnanensis Chen and Erdtmann,1991,它们是澄江生物群最常见的两类宏观藻类具有澄江生物群宏观藻类的组合特征.“清虚洞组”位于黔东统上部,介于杷榔组和凯里组之间,该组宏观藻类的发现,为寒武纪宏观藻类演化链的完整研究提供了有价值的资料.%This paper provides the first report of two species of Cambrian macroalgae, representing two different genera, from the Tsinghsutung Formation (Duyunian Stage, Qiandongian Series) of Jianhe county, Guizhou. They are Fuxianospira gyrata Chen and Zhou, 1997 and Sinocylindricayunnanensis Chen and Erdtmann, 1991. These are the two most common species of macroalgae in the Chengjiang biota, so the macroalgal biota of the Tsinghsutung Formation therefore appears to be similar. These fossils provide new information on the palaeobiogeography and evolutionary history of macroalgae in the Cambrian, and on the relationship of the evolution of these algae to their environment.

  12. Early Cambrian Post-collisional volcanosedimentary Rey Bouba greenstone belt in northern Cameroun: LA-MC-ICP-MS U-Pb geochronology and implications for the geodynamic evolution of the Central African Fold Belt (CAFB).

    Science.gov (United States)

    Bouyo, Merlain

    2014-05-01

    The Rey Bouba Greenstone Belt (RBGB) is a greenschist volcanosedimentary basin representing the youngest accretion event that characterized the geodynamic evolution of the CAFB of Northern Cameroon. LA-MC-ICP-MS U-Pb detrital zircon data indicate that both older PP to MP and younger NP to Early Cambrian sources from ca 2000 to ca 540 Ma, with main provenance being zircon grains from Cryogenian igneous rocks (between ca 850 and ca 650 Ma) were involved in the formation of the RBGB basin. Considering the age of metamorphism inferred from high pressure granulites at ca 600 Ma within the CAFB of northern Cameroon as the most direct evidence for the timing of continental collision, we conclude that the deformation associated with migmatites and post-collisional granites which fed the Rey Bouba basin mostly with NP zircon lasts until post 540 Ma, in correlation with the final amalgamation of the Gondwana Supercontinent during Latest Neoproterozoic-Earliest Cambrian. Therefore, the RBGB may represent the youngest post-collisional metavolcanosedimentary basin within the CAFB.

  13. 四川盆地南部地区寒武系油气勘探前景%Oil and Gas Exploration Prospects of Cambrian in Southern Sichuan Basin

    Institute of Scientific and Technical Information of China (English)

    王佳; 刘树根; 黄文明; 张长俊; 曾祥亮

    2011-01-01

    为明确四川盆地南部地区寒武系常规油气和页岩气的勘探前景,应用岩相学和地球化学分析手段相结合,对研究区中上寒武统娄山组和下寒武统清虚洞组的厚度、孔隙度、渗透率、孔隙类型和下寒武统筇竹寺组的厚度、总有机碳质量分数w(TOC)、镜质体反射率Ro、矿物组分等进行了深入剖析.结果表明:①川南地区烃源岩厚度大(80~100m),w(TOC)高(3%~5%),为一套中—好的过成熟后期阶段烃源岩(Ro为3.0%~4.8%),矿物组分与美国重要页岩气产层Barnett页岩相似,其中石英、长石和黄铁矿的体积分数为31%~50%,黏土矿物体积分数为29%~53%;②威远地区下寒武统九老洞组黑色页岩含气量达0.43~0.86 m3/t;微孔隙发育,主要为粒间孔,孔隙直径达5~10μm,裂缝密度一般为30~50条/m;③中上寒武统娄山组和下寒武统清虚洞组总体上是寒武系最重要的常规储层,储层内部沥青质量分数一般为3%~6%,储集空间主要为粒间溶孔—晶间孔等,平均孔隙度为1.85%,平均渗透率为2.25×10-3μm2;④在川东南地区靠近盆地边缘的斜坡带,寒武系具有较好的常规油气藏勘探前景,而川东南缘和川西南地区筇竹寺组下部具有较大的页岩气勘探潜力.%In order to identify the exploration prospect of Cambrian conventional oil and gas and shale gas in southern Sichuan Basin, this paper, combining the petrographic and geochemical methods, makes a tho-rugh analysis of the thickness, porosity, permeability, porosity type of Middle-Upper Cambrian Loushan-guan Formation and Lower Cambrian Qingxudong Formation, as well as the thickness, TOC, Ro, mineral composition of Lower Cambrian Qiongzhusi Formation. The results show that: (1) The hydrocarbon source rocks in southern Sichuan Basin are thick(80 -100 m)and of high organic matter content (3%-5%). It is a set of general-good late-mature stage of hydrocarbon source

  14. Sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads

    Science.gov (United States)

    Dean, David; Topping, David; Schmidt, John C.; Griffiths, Ronald; Sabol, Thomas

    2016-01-01

    The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form. In this study, physically based analyses suggest that channel change in the Rio Grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales. Channel narrowing is primarily caused by substantial deposition of sediment supplied to the Rio Grande during tributary-sourced flash floods. Tributary floods have large suspended-sediment concentrations, occur for short durations, and attenuate rapidly downstream in the Rio Grande, depositing much of their sediment in downstream reaches. Long-duration floods on the mainstem have the capacity to enlarge the Rio Grande, and these floods, released from upstream dams, can either erode or deposit sediment in the Rio Grande depending upon the antecedent in-channel sediment supply and the magnitude and duration of the flood. Geomorphic and sediment transport analyses show that the locations and rates of sand erosion and deposition during long-duration floods are most strongly controlled by spatial changes in flow strength, largely through changes in channel slope. However, spatial differences in the in-channel sediment supply regulate sediment evacuation or accumulation over time in long reaches (greater than a kilometer).

  15. Suspended sediment and sediment-associated contaminants in San Francisco Bay

    Science.gov (United States)

    Schoellhamer, D.H.; Mumley, T.E.; Leatherbarrow, J.E.

    2007-01-01

    Water-quality managers desire information on the temporal and spatial variability of contaminant concentrations and the magnitudes of watershed and bed-sediment loads in San Francisco Bay. To help provide this information, the Regional Monitoring Program for Trace Substances in the San Francisco Estuary (RMP) takes advantage of the association of many contaminants with sediment particles by continuously measuring suspended-sediment concentration (SSC), which is an accurate, less costly, and more easily measured surrogate for several trace metals and organic contaminants. Continuous time series of SSC are collected at several sites in the Bay. Although semidiurnal and diurnal tidal fluctuations are present, most of the variability of SSC occurs at fortnightly, monthly, and semiannual tidal time scales. A seasonal cycle of sediment inflow, wind-wave resuspension, and winnowing of fine sediment also is observed. SSC and, thus, sediment-associated contaminants tend to be greater in shallower water, at the landward ends of the Bay, and in several localized estuarine turbidity maxima. Although understanding of sediment transport has improved in the first 10 years of the RMP, determining a simple mass budget of sediment or associated contaminants is confounded by uncertainties regarding sediment flux at boundaries, change in bed-sediment storage, and appropriate modeling techniques. Nevertheless, management of sediment-associated contaminants has improved greatly. Better understanding of sediment and sediment-associated contaminants in the Bay is of great interest to evaluate the value of control actions taken and the need for additional controls. ?? 2007 Elsevier Inc. All rights reserved.

  16. Evidence for multi-cycle sedimentation and provenance constraints from detrital zircon U-Pb ages: Triassic strata of the Lusitanian basin (western Iberia)

    Science.gov (United States)

    Pereira, M. F.; Gama, C.; Chichorro, M.; Silva, J. B.; Gutiérrez-Alonso, G.; Hofmann, M.; Linnemann, U.; Gärtner, A.

    2016-06-01

    Laser ablation ICP-MS U-Pb analyses were conducted on detrital zircons of Triassic sandstone and conglomerate from the Lusitanian basin in order to: i) document the age spectra of detrital zircon; ii) compare U-Pb detrital zircon ages with previous published data obtained from Upper Carboniferous, Ordovician, Cambrian and Ediacaran sedimentary rocks of the pre-Mesozoic basement of western Iberia; iii) discuss potential sources; and iv) test the hypothesis of sedimentary recycling. U-Pb dating of zircons established a maximum depositional age for this deposit as Permian (ca. 296 Ma), which is about sixty million years older compared to the fossil content recognized in previous studies (Upper Triassic). The distribution of detrital zircon ages obtained points to common source areas: the Ossa-Morena and Central Iberian zones that outcrop in and close to the Porto-Tomar fault zone. The high degree of immaturity and evidence of little transport of the Triassic sediment suggests that granite may constitute primary crystalline sources. The Carboniferous age of ca. 330 Ma for the best estimate of crystallization for a granite pebble in a Triassic conglomerate and the Permian-Carboniferous ages (< ca. 315 Ma) found in detrital zircons provide evidence of the denudation of Variscan and Cimmerian granites during the infilling of continental rift basins in western Iberia. The zircon age spectra found in Triassic strata are also the result of recycling from the Upper Carboniferous Buçaco basin, which probably acted as an intermediate sediment repository. U-Pb data in this study suggest that the detritus from the Triassic sandstone and conglomerate of the Lusitanian basin is derived from local source areas with features typical of Gondwana, with no sediment from external sources from Laurussia or southwestern Iberia.

  17. On luminescence bleaching of tidal channel sediments

    DEFF Research Database (Denmark)

    Fruergaard, Mikkel; Pejrup, Morten; Murray, Andrew S.

    2015-01-01

    We investigate the processes responsible for bleaching of the quartz OSL signal from tidal channel sediment. Tidal dynamics are expected to play an important role for complete bleaching of tidal sediments. However, no studies have examined the amount of reworking occurring in tidal channels...... and on tidal flats due to the mixing caused by currents and waves. We apply bed level data to evaluate the amount of vertical sediment reworking in modern tidal channels and at a tidal flat. Cycles of deposition and erosion are measured with a bed level sensor, and the results show that gross sedimentation...... on the quantitative measures of sediment reworking, we suggest that repeated depositional and erosional cycles allow for complete bleaching of the tidal flat sediment, and we infer that quartz OSL dating can provide accurate ages for shallow tidal channel fill....

  18. SKELETALIZATION CHARACTERS, CLASSIFICATION AND EVOLUTIONARY SIGNIFICANCE OF EARLY CAMBRIAN MONOPLACOPHORAN MAIKHANELLIDS%早寒武世马哈螺类的骨骼化特征、分类和演化意义

    Institute of Scientific and Technical Information of China (English)

    冯伟民; 孙卫国; 钱逸

    2001-01-01

    , with a rich and well-preserved collection from the Early Cambrian Meishucunian Stage in eastern Yunnan of China. This paper shows that the family Maikhanellidae consists of two subfamilies and all together six genera, including Maikhanella, Ramenta, Ramentoides gen. nov. and Mediata gen. nov. under the Maikhanellinae subfamily nov. and Yunnanopleura and Purella under the Purellinae subfamily nov. Although these genera are obviously different in shape and some other aspects of morphology, they are all characterized by possessing a distinct bare apex, with the rest of outer surface ornamented by closely distributed projective granular structures. Their phylogenic relationships and evolutionary trends are recognized as developing in two directions, one from Maikhanella, Ramentoides gen. nov. to Ramenta, and the other from Maikhanella, Mediata gen. nov., Yunnanopleura to Purella. Maikhanellids occurred mainly in the early and middle Meishucunian Stage. The most primitive form is Maikhanella, which first appeared in the Xiaowaitoushan Member of the early Meishucunian Stage and then developed as the only kind of maikhanellids in the lower part of Zhongyicun Member. Abundant and diverse maikhanellids appeared in the upper part of the Zhongyicun Member of the middle Meishucunian Stage, but all six genera disappeared suddenly in the succeeding Dahai Member without drastic changes in sedimentation. Maikhanellid shells were previously described as consisting of “spicule exoskeleton”, “sclerite exoskeleton” or “spicules embedded in an intermediate matrix” by different authors. The present research, however, indicates that the wall of maikhanellid shells, represented by Maikhanella pristinis and Ramenta cambrina, is layered and that the inner layer of shell is composed of horizontally crossed fibrous structures, a feature that is common in the Monoplacophora. Described in this paper are two new subfamilies, two new genera and five new species, viz., Maikhanellinae

  19. Sedimentation

    Digital Repository Service at National Institute of Oceanography (India)

    Rixen, T.; Guptha, M.V.S.; Ittekkot, V.

    The Monsoonal impact on the deep ocean fluxes, organic carbon export into the ocean's interior, and the difference between the deep-sea organic carbon fluxes and sedimentary organic carbon burial rates in the Arabian Sea were assessed...

  20. Continental margin sedimentation: from sediment transport to sequence stratigraphy

    Science.gov (United States)

    Nittrouer, Charles A.; Austin, James A.; Field, Michael E.; Kravitz, Joseph H.; Syvitski, James P.M.; Wiberg, Patricia L.; Nittrouer, Charles A.; Austin, James A.; Field, Michael E.; Kravitz, Joseph H.; Syvitski, James P. M.; Wiberg, Patricia L.

    2007-01-01

    This volume on continental margin sedimentation brings together an expert editorial and contributor team to create a state-of-the-art resource. Taking a global perspective, the book spans a range of timescales and content, ranging from how oceans transport particles, to how thick rock sequences are formed on continental margins. - Summarizes and integrates our understanding of sedimentary processes and strata associated with fluvial dispersal systems on continental shelves and slopes - Explores timescales ranging from particle transport at one extreme, to deep burial at the other - Insights are presented for margins in general, and with focus on a tectonically active margin (northern California) and a passive margin (New Jersey), enabling detailed examination of the intricate relationships between a wide suite of sedimentary processes and their preserved stratigraphy - Includes observational studies which document the processes and strata found on particular margins, in addition to numerical models and laboratory experimentation, which provide a quantitative basis for extrapolation in time and space of insights about continental-margin sedimentation - Provides a research resource for scientists studying modern and ancient margins, and an educational text for advanced students in sedimentology and stratigraphy

  1. DYNAMIC RESOURCES OF RIVER SEDIMENTS

    Institute of Scientific and Technical Information of China (English)

    George GERGOV; Tzviatka KARAGIOZOVA

    2005-01-01

    The currently enforced Bulgarian water legislation [the Water Act (1999),the Environmental Protection Act (2002),etc.] requires conducting special studies for accurate assessments of sand and gravel flux along the rivers,prior to the issue of the license for operation of the quarries,where they will be dredged. The activity of a quarry necessitates special investigations because of the large dimensions of the damages inflicted on the environment. Ours studies have shown that there are two types of river reaches,in which abstracion of sand and gravel is performed. The first one refers usually to the plain area river reaches. The other type is mountainous with high rate of sediment load,which consists of coarse solid matter. The "on-the-spot" study on the environmental impact of the sand and gravel dredging has revealed that in the area of the quarry the riverbed cuts into the alluvial sediments to about 6-7 m and this ditch has spread by attenuation at a distance of more than 25 km upstream. Downstream the pit the picture is replicated and at the 8th km a local scour on the riverbed,amounting to more than 1.80 - 2.00 m,has been measured near the foundation of a massive bridge in the centre of city of Plovdiv. Such assessments of dynamic resources of sand and gravel materials are expected to serve for the purposes of gradual limitation of this activity in river sections close to renewable resources. The amount of sediment load,which may be abstracted in the area of the Orizare quarry in Bulgaria on a yearly basis has been calculated as 6000 m3/a. It ensures that the resources will not be exhausted and irreversible distortion of the riverbed will be prevented. This is an environmentally safe limit.

  2. Analysis of sedimentation of canals

    Directory of Open Access Journals (Sweden)

    Agunwamba, J.C.,

    2013-03-01

    Full Text Available The dredged canals in the Niger Delta coastal flood plain are being threatened by siltation. This study is limited to those canals in Rivers State of Nigeria, which are under the influence of tidal waves. A total of eight canals were considered with four each from Ekulama and Cawthorne Channel. Different approaches were used to carry out this study, which includes field reconnaissance survey, hydrographic survey, soil sample analysis and collection of all available data and information. The typical bed materials size (D50 is approximately 0.01mm; which gives a settling velocity of 0.09mm/sec using stroke’s law. Hydrographic survey of the canals from 1992 to 1996 revealed an average siltation rate of 2.35m/yr. A regression equation was also derived which relates the cost of dredging to canal area, rate of siltation and average aggregation. A plot of canal centre profile; entrance, middle and end cross sections showing sediment distribution along the canal profile, shows that majority of the particles that form the sediment enter the canal from the rivers. The sedimentation is caused by the reduction in water current, which has average value of 0.0145m/sec. The bathyorographical check on the canals revealed that the sum of the two exterior angles of the canal with the river at the point of connection has to lie within 1800 + 50 for an effective flow that will minimize settlement of particles. In addition, the canals should be constructed to start and terminate on a moving water body, to avoid dead ends. A regression equation was determined which relates the cost of dredging to canal area, rate of siltation and average aggradations.

  3. Sediment Movement in Periodic Alternating Current

    Institute of Scientific and Technical Information of China (English)

    CAO Zude; KONG Lingshuang; LIU Defu

    2002-01-01

    The present paper summarizes the results of previous studies, including the structure and principle of the rotaryring flume for researching the fine sediment movement, the mechanism of the flume, method of eliminating the influence ofthe centrifugal force and sediment movement experiments with periodic alternating current. Also included are the experi-ment-based relationship among sediment concentration, bed shear stress and silt carrying capacity, a proposed erosion-depo-sition function and bed erosion-deposition calculation together with the results of verification.

  4. Urine sediment from a Chihuahua.

    Science.gov (United States)

    Pallatto, Valarie; Wood, Michael; Grindem, Carol

    2005-12-01

    A 6-year-old, intact male Chihuahua was presented with stranguria and painful urination of 5 days duration. Cystine crystals were observed in low numbers in unstained urine sediment preparations, and a diagnosis of cystinuria was made. Uroliths were removed surgically from the urethra and the bladder, and mineral analysis indicated the stones were composed of 100% cystine. Cystinuria results from an inherited defect in renal tubular transport of cystine that affects many breeds and has been found as an autosomal recessive trait in Newfoundlands. Accurate identification of cystine crystals in urine is an important means of diagnosing cystinuria.

  5. Sediment Sources in the Persian Gulf

    Science.gov (United States)

    Mahoutian, Mehrab

    2014-05-01

    Sediment Constituent Analysis is an effective tool for identifying sediment sources. Based on several sediment samples taken from different sites all over the Iranian coastlines, we have been able to show that an important portion of sediment on the beaches in the Persian Gulf is bio-clastic; that is, biologically created from the coral environment as well as other marine habitats. Unlike mineral (clastic) sediments, carbonate sediments are born not made. Furthermore, carbonate sand constituents are generally less durable than their quartz and mineral counterparts, and break down relatively quickly. Therefore, destruction of reefs and degradation of marine habitat are certain to reduce the sand supply to the shoreline in the Persian Gulf that is necessary to maintain beaches. Carbonate sands are also found on the coastline of the Oman Sea. One of the striking things about the sediments along the coastline of Iran is the high percentage of carbonate material. Molluscan debris is common, even ubiquitous. This reflects the populations living in the offshore waters. Some molluscs thrive in high-energy sandy environments, others like finer sediments. Some live at the surface, while some burrow down as much as a half-metre. A great deal of information can be gained from the study of the species of mollusk and their distribution in the sediments. This paper introduces a few case studies done in different parts of the Persian Gulf by using this method as a general assessment toolbox.

  6. STUDY ON STARTING VELOCITY OF COHESIVE SEDIMENTATION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, with the starting velocity experiments of natural cohesive sedimentation, the author proposes an assumption concerning the starting mechanism of cohesive sedimentation and gives a formula to determine the starting velocity of compact clay. It is pointed out that the fluctuating function of flow is a main factor for the starting of sedimentation. And the component and the structure of cohesive sedimentation are also the affecting factors for the starting. Consequently, the study shows that modern results of soil mechanics, clay mineralogy and fluid mechanics are helpful in the investigation of this kind of engineering problem.

  7. Release of metals from anoxic sediment

    DEFF Research Database (Denmark)

    Larsen, Martin Mørk; Jacobsen, Gitte

    The Bornholm Deep is anoxic every summer, and samples were collected in the fall 2012 and stored dark and cold (4°C in climate room), degassing regularly with Ar(g) to keep the overlying water column anoxic. Nine sediments columns were selected and divided into three groups, (1) where the water w...... without crabs, but cloudy, indicating re-suspension in the group with crabs. The metal release from sediments will be discussed in the context of re-oxygenation of anoxic or low-oxic sediments and the effect of organism that digs into the sediment in recently re-oxidised bottom waters....

  8. Arsenic mobility in contaminated lake sediments

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaidis, Nikolaos P.; Dobbs, Gregory M.; Chen, Jing; Lackovic, Jeffrey

    2004-06-01

    An arsenic contaminated lake sediment near a landfill in Maine was used to characterize the geochemistry of arsenic and assess the influence of environmental conditions on its mobility. A kinetic model was developed to simulate the leaching ability of arsenic in lake sediments under different environmental conditions. The HM1D chemical transport model was used to model the column experiments and determine the rates of arsenic mobility from the sediment. Laboratory studies provided the information to construct a conceptual model to demonstrate the mobility of arsenic in the lake sediment. The leaching ability of arsenic in lake sediments greatly depends on the flow conditions of ground water and the geochemistry of the sediments. Large amounts of arsenic were tightly bound to the sediments. The amount of arsenic leaching out of the sediment to the water column was substantially decreased due to iron/arsenic co-precipitation at the water-sediment interface. Overall, it was found that arsenic greatly accumulated at the ground water/lake interface and it formed insoluble precipitates. - Arsenic accumulates at the ground water/lake interface, where it forms insoluble precipitates.

  9. Hawaii Regional Sediment Management (RSM): Regional Sediment Budget for the West Maui Region

    Science.gov (United States)

    2016-06-01

    margin backed by steep mountainous terrain that has been vastly altered by agricultural and urbanized development. Shoreline hardening is being...majority of sediment transport (northward-directed in summer and southward-directed in winter). Because of these seasonal patterns, the net transport ...of sediment is small. There is evidence of nearshore eddy formation that increases the complexity of sediment transport in the region with sediment

  10. Upstream sediment input effects on experimental dune trough scour in sediment mixtures

    OpenAIRE

    Kleinhans, M. G.

    2005-01-01

    Understanding causes of dune irregularity, especially dune trough scour, is important for the modeling of vertical sorting of sediment mixtures in morphological models of rivers with sediment mixtures. Sediment in dunes is generally sorted in a fining-upward manner, which affects the sediment transport composition depending on the scour depth distribution of the dunes. Why dunes become more irregular and develop deep scour holes in some conditions is only partially understood. Moreover, there...

  11. Seasonal variations in pore water and sediment geochemistry of littoral lake sediments (Asylum Lake, MI, USA)

    OpenAIRE

    Miller Douglas; Haas Johnson R; Koretsky Carla M; Ndenga Noah T

    2006-01-01

    Abstract Background Seasonal changes in pore water and sediment redox geochemistry have been observed in many near-surface sediments. Such changes have the potential to strongly influence trace metal distribution and thus create seasonal fluctuations in metal mobility and bioavailability. Results Seasonal trends in pore water and sediment geochemistry are assessed in the upper 50 cm of littoral kettle lake sediments. Pore waters are always redox stratified, with the least compressed redox str...

  12. Cross-shore suspended sediment transport in the surf zone: A fieldbased parameterization

    DEFF Research Database (Denmark)

    Aagaard, Troels; Black, Kerry; Greenwood, Brian

    2002-01-01

    sediment transport, sediment concentrations, incident waves, undertow, morphodynamics, beach processes......sediment transport, sediment concentrations, incident waves, undertow, morphodynamics, beach processes...

  13. FRACTIONAL TRANSPORT OF SEDIMENT MIXTURES

    Institute of Scientific and Technical Information of China (English)

    Baosheng WU; Albert MOLINAS; Anping SHU

    2003-01-01

    A new method based on the Transport Capacity Fraction (TCF) concept is proposed to compute the fractional transport rates for nonuniform sediment mixtures in sand-bed channels. The TCF concept is derived from the understanding that the measurements and predictions of bed-material load are more accurate and reliable than the measurements and predictions of fractional loads. First the bed-material load is computed using an appropriate equation, then the fractional transport rates are determined by distributing the bed-material load into size groups through a transport capacity distribution function. For the computation of bed-material loads, the Aekers and White, Engelund and Hansen, and Yang equations are used in this study. Two new transport capacity distribution functions are developed for flows in sand-bed channels. The new expressions presented in this paper account for the sheltering and exposure effects that exist in mixtures. Comparisons with measured data show that the proposed method can significantly improve the predictions of fractional transport rates for nonuniform sediment mixtures.

  14. ESTUARINE AND COASTAL SEDIMENTATION PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    Leo C.VAN RIJN

    2005-01-01

    This keynote lecture addresses engineering sedimentation problems in estuarine and coastal environments and practical solutions of these problems based on the results of field measurements,laboratory scale models and numerical models. The three most basic design rules are: (1) try to understand the physical system based on available field data; perform new field measurements if the existing field data set is not sufficient (do not reduce on the budget for field measurements); (2) try to estimate the morphological effects of engineering works based on simple methods (rules of thumb,simplified models,analogy models,i.e. comparison with similar cases elsewhere); and (3) use detailed models for fine-tuning and determination of uncertainties (sensitivity study trying to find the most influencial parameters). Engineering works should be designed in such a way that side effects (sand trapping,sand starvation,downdrift erosion) are minimum. Furthermore,engineering works should be designed and constructed or built in harmony rather than in conflict with nature. This 'building with nature' approach requires a profound understanding of the sediment transport processes in morphological systems.

  15. Modern sedimentation and sediment dispersal pattern off southwestern Taiwan

    Science.gov (United States)

    Hsu, Sheng-Ting; Su, Chih-Chieh; Tsai, Po-Hsuan; Cheng, Yiya

    2015-04-01

    Taiwan is located at the collision zone between the Eurasian and Philippine Sea Plates and also on the Western North Pacific corridor of typhoons. Every year, three to four typhoons will invaded Taiwan and brought heavy rainfall. The active tectonic setting and climatic conditions create the extremely high sediment yield and export to the ocean. Our study area is located offshore southwestern Taiwan which is mainly composed of a narrow Gaoping Shelf and broad Gaoping Slope. Four major submarine canyons, the Shoshan Submarine Canyon, Kaohsiung Submarine Canyon, Gaoping Submarine Canyon, and Fangliao Submarine Canyon, extended into deep sea, through Penghu Submarine Canyon and subsequently merged into north terminus of Manila Trench. Over 50 box and gravity cores were collected by using R/V Ocean Research 1, 3 and 5 from 2005 to 2014. The cores were split and conducted core description and surface photographs at the Core Laboratory of the Taiwan Ocean Research Institute (TORI). The following analyses, including X-radiography, bulk density, particle size, Pb-210 chronology, were accomplished at the Marine Radioactivity and Sedimentology Lab at the Institute of Oceanography, National Taiwan University. The grain size analysis result shows a finer trend from coastal to deep water , except for the lower Fangliao basin which the grain size is larger than the expected value. According to the previous studies on the Pingtung Earthquake induced submarine geohazard, the Fangliao Submarine Canyon and the Lower Fangliao Basin is an important conduit for gravity flow which triggered large scale submarine cable breakages and left coarse sediments on the passage. By using the excess Pb-210 derived sediment accumulation rates, Huh et al. (2009) suggested the depocenter off the southwestern Taiwan is located at the flank of the Gaoping Canyon over the upper slope with the highest rate >1 cm/yr. In this study we integrate the Pb-210 inventory data which covered the area from the

  16. Influence of wave and current flow on sediment-carrying capacity and sediment flux at the water-sediment interface.

    Science.gov (United States)

    Zheng, Jun; Li, Ruijie; Yu, Yonghai; Suo, Anning

    2014-01-01

    In nearshore waters, spatial and temporal scales of waves, tidal currents, and circulation patterns vary greatly. It is, therefore, difficult to combine these factors' effects when trying to predict sediment transport processes. This paper proposes the concept of significant wave velocity, which combines the effects of waves, tides, and ocean currents using the horizontal kinetic energy superposition principle. Through a comparison of the relationship between shear stress at the water-sediment interface and sediment-carrying capacity, assuming equilibrium sediment flux, a new formula for sediment-carrying capacity, which incorporates the concept of significant wave velocities, is derived. Sediment-carrying capacity is a function of the critical velocity, which increases with water depth and decreases with increasing relative roughness of the sea bed. Finally, data from field observation stations and simulations are used to test the proposed formula. The results show that the new formula is in good agreement with both field and simulation data. This new formula for sediment-carrying capacity can be used to simulate nearshore sediment transport.

  17. Suspended sediment yield in Texas watersheds

    Science.gov (United States)

    Coonrod, Julia Ellen Allred

    The Texas Water Development Board collected suspended sediment samples across the state of Texas for approximately 60 years. Until this research, no comprehensive analysis of the data had been conducted. This study compiles the suspended sediment data along with corresponding streamflow and rainfall. GIS programs are developed which characterize watersheds corresponding to the sediment gauging stations. The watersheds are characterized according to topography, climate, soils, and land use. All of the data is combined to form several SAS data sets which can subsequently be analyzed using regression. Annual data for all of the stations across the state are classified temporally and spatially to determine trends in the sediment yield. In general, the suspended sediment load increases with increasing runoff but no correlation exists with rainfall. However, the annual average rainfall can be used to classify the watersheds according to climate, which improves the correlation between sediment load and runoff. The watersheds with no dams have higher sediment loads than watersheds with dams. Dams in the drier parts of Texas reduce the sediment load more than dams in the wetter part of the state. Sediment rating curves are developed separately for each basin in Texas. All but one of the curves fall into a band which varies by about two orders of magnitude. The study analyzes daily time series data for the Lavaca River near Edna station. USGS data are used to improve the sediment rating curve by the addition of physically related variables and interaction terms. The model can explain an additional 41% of the variability in sediment concentration compared to a simple bivariate regression of sediment load and flow. The TWDB daily data for the Lavaca River near Edna station are used to quantify temporal trends. There is a high correlation between sediment load and flowrate for the Lavaca River. The correlation can be improved by considering a flow-squared term and by

  18. Accounting for Long Term Sediment Storage in a Watershed Scale Numerical Model for Suspended Sediment Routing

    Science.gov (United States)

    Keeler, J. J.; Pizzuto, J. E.; Skalak, K.; Karwan, D. L.; Benthem, A.; Ackerman, T. R.

    2015-12-01

    Quantifying the delivery of suspended sediment from upland sources to downstream receiving waters is important for watershed management, but current routing models fail to accurately represent lag times in delivery resulting from sediment storage. In this study, we route suspended sediment tagged by a characteristic tracer using a 1-dimensional model that implicitly includes storage and remobilization processes and timescales. From an input location where tagged sediment is added, the model advects suspended sediment downstream at the velocity of the stream (adjusted for the intermittency of transport events). Deposition rates are specified by the fraction of the suspended load stored per kilometer of downstream transport (presumably available from a sediment budget). Tagged sediment leaving storage is evaluated from a convolution equation based on the probability distribution function (pdf) of sediment storage waiting times; this approach avoids the difficulty of accurately representing complex processes of sediment remobilization from floodplain and other deposits. To illustrate the role of storage on sediment delivery, we compare exponential and bounded power-law waiting time pdfs with identical means of 94 years. In both cases, the median travel time for sediment to reach the depocenter in fluvial systems less than 40km long is governed by in-channel transport and is unaffected by sediment storage. As the channel length increases, however, the median sediment travel time reflects storage rather than in-channel transport; travel times do not vary significantly between the two different waiting time functions. At distances of 50, 100, and 200 km, the median travel time for suspended sediment is 36, 136, and 325 years, orders of magnitude slower than travel times associated with in-channel transport. These computations demonstrate that storage can be neglected for short rivers, but for longer systems, storage controls the delivery of suspended sediment.

  19. Quantifying sediment connectivity in Wadi Al-Arab (NW Jordan) using a sediment budget approach

    Science.gov (United States)

    Kraushaar, Sabine; Pöppl, Ronald

    2015-04-01

    Due to data scarcity, sediment connectivity most often only qualitatively describes the potential transfer of sediments through a landscape. However, quantitative information on sediment delivery is of special relevance for modelling approaches as well as for sustainable land and water management, especially in water scarce regions such as Jordan, where valuable water reservoirs suffer from sediment pollution. Measurements are needed to quantify sediment outputs of the different land units and to trace their pathways though the catchments. This study uses the outcomes of a multiple response sediment budget approach conducted in the Wadi al-Arab catchment in northwest Jordan (263.5 km²) to quantify sediment connectivity. The catchment shows a Mediterranean to semi arid climate and consists of carbonatic and marly geology of the Upper Cretaceous. The topography ranges from rolling hills in the East to steeper mountainous areas in the North and West were olive orchards are the main agricultural use. Soil erosion measurements in the main land use units and relevant sediment sources, such as olive orchards, agricultural fields, and natural vegetated slopes uncovered the potential ranges of soil erosion rates in these units. Furthermore, the annual sediment yield in the Wadi Al Arab water reservoir was calculated. With the extrapolation of the erosion rates of the main contributing land use units and the annual sediment amount that reaches the sink, a maximum value of lateral sediment connectivity could be quantified, reaching up to 18%. A multiple sediment fingerprint method was used to delineate the relative contribution of each measured source to the sink based on the lake sediment samples. Supported by additional 137Cs analysis of terrace samples and a survey of the Wadi bed a high longitudinal connectivity could be derived. The applied method mix allowed the quantification of lateral sediment connectivity on catchment scale and gave a comprehensive understanding of

  20. 广西大瑶山—大明山地区寒武纪砂岩-泥岩的地球化学特征及沉积-构造环境分析%Geochemical characteristics and sedimentary-tectonic setting of the Cambrian sandstones and mudstones in Dayaoshan-Damingshan area,Guangxi

    Institute of Scientific and Technical Information of China (English)

    杜晓东; 邹和平; 苏章歆; 劳妙姬; 陈诗艾; 丁汝鑫

    2013-01-01

    The Daoyaoshan-Damingshan area is located in the southwestern section of the Qinzhou-Hangzhou juncture between the Yangtze Block and the Cathayian Block.The study of the early Paleaozoic sedimentary environment and tectonic setting of this area is a key to understanding the geotectonic problems in South China.Major and trace elements of 27 pieces of samples from Cambrian sandstones and mudstones in this area were analyzed and discussed.The samples generally have high ratios of Al2O3/TiO2 (in the range of 11.95~36.26,20.81on average) and lower ratios of Rb/Cs(in the range of 13.02~68.27,32.21 on average) and Cr/Zr(ranging 0.14~1.15,averagely 0.59).Geochemical characteristics,such as the plots of Ni-TiO2,Th/Sc-La/Sc and La/Th-Hf,indicate that the Cambrian sediments in the Daoyaoshan-Damingshan area were mainly sourced from the upper crustal felsic quartz rocks,with the addition of a small amount of igneous sources and ancient recirculation sediments.The distribution of trace and rare-earth elements and the data of La-Th-Sc,K2O/Na2O-SiO2,δ Ce,δEu,Tb/Yb,La/Sc,La/Th,Th/U as well as the comparison with different tectonic settings show that the study area belonged to a passive continent-marginal setting.In addition,such evidence as the marks of shallow-sea deposits,the data of sedimentary palaeogeography,regional geology and geochemistry suggests that during the Early Paleozoic there existed no geochemical evidence for the so called "ancient ocean in South China".%大瑶山-大明山地区位于钦杭结合带西南段,是研究华南大地构造问题的关键部位.对区内寒武纪地层中采集的27件砂岩、泥岩样品进行了主量元素、微量元素测试和地球化学特征分析.结果表明,样品普遍具有较高的A12O3/TiO2(11.95~36.26,平均20.81)、低Rb/Cs(13.02~68.27,平均32.21,接近上地壳值)和低Cr/Zr(0.14~1.15,平均0.59)比值.在砂岩-泥岩物源判别函数和Ni-TiO2、Th/Sc-La/Sc、La/Th-Hf图解中,投点特征均

  1. Formación Alojamiento (Cámbrico en su localidad tipo. Paleoambiente sedimentario del margen continental eopaleozoico, Precordillera mendocina The Alojamiento Formation (Cambrian in its type locality. Sedimentary paleoenvironment of the Eopaleozoic continental margin, Precordillera Mendocina

    Directory of Open Access Journals (Sweden)

    A.L. Banchig

    2006-09-01

    Full Text Available Como consecuencia del tectonismo dominante en el área de la Precordillera occidental los afloramientos eopaleozoicos están frecuentemente truncados tectónicamente y muchas veces los efectos sobreimpuestos suelen confundirse con procesos de deformación sinsedimentarios. Estos afloramientos constituyen escamas tectónicas con extensión lateral y vertical limitada y se distribuyen en forma saltuaria y de norte a sur a lo largo de la Precordillera cuyana. Un detallado análisis integral desde el punto de vista nomenclatural, geológico, litoestratigráfico, paleontológico y paleoambiental sobre sedimentitas carbonáticas cámbricas aflorantes en la localidad de Los Alojamientos es presentado aquí con el objeto de actualizar el conocimiento geológico de este sector de la Precordillera, bajo la luz de hallazgos paleontológicos y de nuevas evidencias geológicas observadas recientemente. Las características sedimentológicas y asociaciones litofaciales de la secuencia estudiada, revelan condiciones del paleoambiente sedimentario para el intervalo cámbrico medio alto - cámbrico superior de la cuenca de la Precordillera e identifican un entorno paleogeográfico interpretado como correspondiente a un margen de plataforma. Arreglos litofaciales internos revelan condiciones de una somerización progresiva que se atribuyen a procesos de regresión eustática y se correlacionan con aquellos identificados en secuencias carbonáticas de la misma edad en la Precordillera oriental.Due to the tectonic activity in the western Precordillera area, the Eopaleozoic outcrops are tectonically truncated and the overprint effect many times is misinterpreted as synsedimentary deformation processes. These outcrops constitute tectonic bodies with lateral and vertical extension limited by reverse faults and they have isolated distribution from north to south along to the Cuyo Precordillera. A detailed and complete analysis of the Cambrian limestones outcropping in

  2. Luminescence dating of storm-surge sediment

    NARCIS (Netherlands)

    Cunningham, A.C.

    2011-01-01

    Geological evidence of storm surges has the potential to provide vital information on storm-surge risk. Sediment from the coastal dunes of the Netherlands contains evidence of extreme floods that occurred before reliable measurements of water level began. For these sediments to be useful in flood-ri

  3. SEDIMENT TRANSPORT IN THE YANGTZE RIVER ESTUARY

    Institute of Scientific and Technical Information of China (English)

    SHEN Zhigang

    2001-01-01

    The hydrodynamic and the sediment transport patterns within the estuary of the Yangtze River are complex because of interaction of fluvial and the tidal forces, depending on freshwater discharge and tidal range. Based on the data measured in recent years, this paper discusses the characteristics of flow and sediment movement in the Yangtze River Estuary and their influences on the evolution of the estuary.

  4. Sediment transport capacity of hyperconcentrated flow

    Institute of Scientific and Technical Information of China (English)

    SHU AnPing; FEI XiangJun

    2008-01-01

    As one of the most important components of river mechanics, sediment transport capacity of sediment-laden flows has attracted much attention from many re-searchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow, an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional, steady, uniform, fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data, which were obtained through two kinds of sediment transport experiments in the state of equilibrium, in combi-nation with the basic rheological and sediment transporting characteristics of hy-perconcentrated flow, the main parameters in the structural expression of sediment transport capacity were calibrated, and a new formula of sediment transport ca-pacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River, Wuding River, and Yangtze River, etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for man-agement of rivers carrying high concentration of sediments.

  5. Bioavailability of Metals in Contaminated Sediments

    Directory of Open Access Journals (Sweden)

    Paller M. H.

    2013-04-01

    Full Text Available Bioavailability controls the transfer of metals from sediments to ecological receptors and humans. It can rarely be predicted from total metal concentrations because it is affected by metal geochemistry in sediments as well as the biochemistry, physiology, and behavior of benthic organisms. There is no single approach for including bioavailability in risk assessments because of variability in site specific conditions and the difficulty of validating methods. Acid-volatile sulfide and simultaneously extracted metals are useful in predicting bioavailability in anoxic sediments containing sulfides that react to form insoluble metal complexes. This method can be improved by adjusting for organic carbon and other ligands that also bind free metals. Site-specific desorption Kd values calculated by sequential extraction methods can be useful in predicting bioavailable metal fractions in oxic and anoxic sediments. A modified desorption distribution coefficient (Kdg can be calculated by extraction with the digestive gut fluids of sediment feeding organisms to account for the effects of ingestion on metal release from sediments. Recently developed in situ measurement technologies can accumulate dissolved metals in a controlled fashion that may correspond with bioavailable metal fractions in sediment. Successful evaluation of bioavailability requires the selection of methods suitable for the organisms and sediment environments under consideration. A weight-of-evidence approach that incorporates multiple lines of evidence can help address uncertainties and increase the likelihood of incorporating bioavailability into remedial decisions.

  6. Sediment transport capacity of hyperconcentrated flow

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    As one of the most important components of river mechanics,sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow,an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional,steady,uniform,fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data,which were obtained through two kinds of sediment transport experiments in the state of equilibrium,in combination with the basic rheological and sediment transporting characteristics of hyperconcentrated flow,the main parameters in the structural expression of sediment transport capacity were calibrated,and a new formula of sediment transport capacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River,Wuding River,and Yangtze River,etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments.

  7. Mercury-contaminated sediments affect amphipod feeding.

    Science.gov (United States)

    Bundschuh, Mirco; Zubrod, Jochen P; Seitz, Frank; Newman, Michael C; Schulz, Ralf

    2011-04-01

    A 125-mile reach of the South River, Virginia, was contaminated with mercury during the first half of the 20th century. As increased concentrations of mercury have persisted, researchers have carefully studied its distribution in the river biota and estimated associated risks. The present study evaluated the influence of mercury on feeding rate and uptake by the amphipod Hyalella azteca. The test organisms were exposed for 7 days with leaf discs to reference and contaminated field sediment during the preliminary experiment and additionally to Sedimite (a commercial mercury-sequestering agent) amended sediments during the final experiment. The preliminary experiment demonstrated a decreased feeding rate (approximately 35%) of H. azteca in sediment from a contaminated site relative to sediment from a reference site. The test design of the final experiment took advantage of the knowledge gained in the preliminary experiment by increasing the number of replicates, which decreased the type II error rate. First, the results of the final experiment confirmed the results of the preliminary experiment by again demonstrating differences in the feeding rate of approximately 35% between reference and contaminated sediment. Second, the results indicated a lower feeding rate in reference sediment in the presence of Sedimite. Third, an opposite tendency, although not significant, was apparent for Sedimite-amended contaminated sediment. Thus, Sedimite appears to decrease sediment quality, whereas this conclusion is based on the feeding rate of H. azteca. However, Sedimite and its value as a mercury-sequestering agent requires further evaluation.

  8. Sediment chemoautotrophy in the coastal ocean

    Science.gov (United States)

    Vasquez-Cardenas, Diana; Meysman, Filip J. R.; van Breugel, Peter; Boschker, Henricus T. S.

    2016-04-01

    A key process in the biogeochemistry of coastal sediments is the reoxidation of reduced intermediates formed during anaerobic mineralization which in part is performed by chemoautotrophic micro-organisms. These microbes fix inorganic carbon using the energy derived from reoxidation reactions and in doing so can fix up to 32% of the CO2 released by mineralization. However the importance and distribution of chemoautotrophy has not been systematically investigated in these environments. To address these issues we surveyed nine coastal sediments by means of bacterial biomarker analysis (phospholipid derived fatty acids) combined with stable isotope probing (13C-bicarbonate) which resulted in an almost doubling of the number of observations on coastal sedimentary chemoautotrophy. Firstly, sediment chemoautotrophy rates from this study and rates compiled from literature (0.07 to 36 mmol C m-2 d-1) showed a power-law relation with benthic oxygen uptake (3.4 to 192 mmol O2 m-2 d-1). Benthic oxygen uptake was used as a proxy for carbon mineralization to calculate the ratio of the CO2 fixed by chemoautotrophy over the total CO2 released through mineralization. This CO2 efficiency was 3% in continental shelf, 9% in nearshore and 21% in salt marsh sediments. These results suggest that chemoautotrophy plays an important role in C-cycling in reactive intertidal sediments such as salt marshes rather than in the organic-poor, permeable continental shelf sediments. Globally in the coastal ocean our empirical results show that chemoautotrophy contributes ˜0.05 Pg C y-1 which is four times less than previous estimates. Secondly, five coastal sediment regimes were linked to the depth-distribution of chemoautotrophy: 1) permeable sediments dominated by advective porewater transport, 2) bioturbated sediments, and cohesive sediments dominated by diffusive porewater transport characterized by either 3) canonical sulfur oxidation, 4) nitrate-storing Beggiatoa, or 5) electrogenic sulfur

  9. Uncertainty in tsunami sediment transport modeling

    Science.gov (United States)

    Jaffe, Bruce E.; Goto, Kazuhisa; Sugawara, Daisuke; Gelfenbaum, Guy R.; La Selle, SeanPaul M.

    2016-01-01

    Erosion and deposition from tsunamis record information about tsunami hydrodynamics and size that can be interpreted to improve tsunami hazard assessment. We explore sources and methods for quantifying uncertainty in tsunami sediment transport modeling. Uncertainty varies with tsunami, study site, available input data, sediment grain size, and model. Although uncertainty has the potential to be large, published case studies indicate that both forward and inverse tsunami sediment transport models perform well enough to be useful for deciphering tsunami characteristics, including size, from deposits. New techniques for quantifying uncertainty, such as Ensemble Kalman Filtering inversion, and more rigorous reporting of uncertainties will advance the science of tsunami sediment transport modeling. Uncertainty may be decreased with additional laboratory studies that increase our understanding of the semi-empirical parameters and physics of tsunami sediment transport, standardized benchmark tests to assess model performance, and development of hybrid modeling approaches to exploit the strengths of forward and inverse models.

  10. Snake and Columbia Rivers Sediment Sampling Project

    Energy Technology Data Exchange (ETDEWEB)

    Pinza, M.R.; Word, J.Q; Barrows, E.S.; Mayhew, H.L.; Clark, D.R. (Battelle/Marine Sciences Lab., Sequim, WA (United States))

    1992-12-01

    The disposal of dredged material in water is defined as a discharge under Section 404 of the Clean Water Act and must be evaluated in accordance with US Environmental Protection Agency regulation 40 CFR 230. Because contaminant loads in the dredged sediment or resuspended sediment may affect water quality or contaminant loading, the US Army Corps of Engineers (USACE), Walla Walla District, has requested Battelle/Marine Sciences Laboratory to collect and chemically analyze sediment samples from areas that may be dredged near the Port Authority piers on the Snake and Columbia rivers. Sediment samples were also collected at River Mile (RM) stations along the Snake River that may undergo resuspension of sediment as a result of the drawdown. Chemical analysis included grain size, total organic carbon, total volatile solids, ammonia, phosphorus, sulfides, oil and grease, total petroleum hydrocarbons, metals, polynuclear aromatic hydrocarbons, pesticides, polychlorinated biphenyls, and 21 congeners of polychlorinated dibenzodioxins and dibenzofurans.

  11. Effects of oil sands sediments on fish

    Energy Technology Data Exchange (ETDEWEB)

    Parrott, J.; Colavecchia, M.; Hewitt, L.; Sherry, J.; Headley, J. [Environment Canada, Ottawa, ON (Canada); Turcotte, D.; Liber, K. [Saskatchewan Univ., Regina, SK (Canada)

    2010-07-01

    This paper described a collaborative project organized by Natural Resources Canada (NRCan) Panel of Energy Research and Development (PERD) with researchers from Environment Canada and the University of Saskatchewan. The 4-year study was conducted to assess the toxicity of oil sands sediments and river waters, and reclamation ponds and sediments on laboratory-raised fish. Three sediments from rivers were evaluated for their potential to cause adverse impacts on fathead minnow eggs and larvae for a period of 18 days. The study monitored hatching, larval survival, development, and growth. Naphthenic acids (NA), polycyclic aromatic hydrocarbons (PAHs) and metals were measured in the sediments to determine if the compounds can be correlated with observed toxicity. The study will also assess walleye eggs exposed to sediments, and in situ fish exposures. Toxicity identification and evaluation (TIE) studies will be conducted to isolate the fractions that may affect fish development and growth.

  12. A MATHEMATICAL MODEL OF RESERVOIR SEDIMENTATION

    Institute of Scientific and Technical Information of China (English)

    HUANG Jinchi

    2001-01-01

    Reliable quantitative estimation of bed aggradation or degradation is important for river-training and water management projects. With the development of water resources, sediment problems associated with a dam are becoming more severe. This paper describes some special problems in mathematical model for calculation of degradation and aggradation in a reservoir. The main efforts of this study are on the treatment of some physical processes of fine sediment transport (<0.05 mm). Problems in a reservoir are obviously different from a natural stream, such as the turbid current flow, orifice sediment flushing;and the initiation and consolidation of cohesive sediment deposition. The case of Liujiaxia Reservoir,which is located in the upper reaches of the Yellow River, is employed to verify the model. The results show that the model is applicable in the evaluation of an engineering planing with plenty of fine sediment movement.

  13. Water-sediment flow models for river reaches sediment related pollution control.

    Science.gov (United States)

    Sil, Briti Sundar; Choudhury, Parthasarathi

    2012-07-01

    Hybrid water-sediment flow models for river reaches have been for predicting sediment and sediment related pollutions in water courses. The models are developed by combining sediment rating model and the Muskingum model applicable for a reach. The models incorporate sediment concentration and water discharge variables for a river reach; allow defining downstream sediment rating curve in terms of upstream water discharges. The model is useful in generating sediment concentration graph for a station having no water discharge records. The hybrid models provide forecasting forms that can be used to forecast downstream sediment concentration/water discharges 2kx time unit ahead. The forecasting models are useful for applications in real time namely, in the real time management of sediment related pollution in water courses and in issuing flood warning. Integration of sediment rating model and the Muskingum model increases model parameters and nonlinearity requiring efficient estimation technique for parameter identification. To identify parameters in the hybrid models genetic algorithm (GA) based optimization technique can be used. The new model relies on the Muskingum model, obey continuity requirement and the parameters can be used in the Muskingum model with water discharges to estimate/predict downstream water discharge values. The proposed model formulations are demonstrated for simulating and forecasting sediment concentration and water discharges in the Mississippi River Basin, USA. Model parameters are estimated using non-dominated sorting Genetic Algorithm II (NSGA-II). Model results show satisfactory model performances.

  14. A probabilistic sediment cascade model of sediment transfer in the Illgraben

    Science.gov (United States)

    Bennett, G. L.; Molnar, P.; McArdell, B. W.; Burlando, P.

    2014-02-01

    We present a probabilistic sediment cascade model to simulate sediment transfer in a mountain basin (Illgraben, Switzerland) where sediment is produced by hillslope landslides and rockfalls and exported out of the basin by debris flows and floods. The model conceptualizes the fluvial system as a spatially lumped cascade of connected reservoirs representing hillslope and channel storages where sediment goes through cycles of storage and remobilization by surface runoff. The model includes all relevant hydrological processes that lead to runoff formation in an Alpine basin, such as precipitation, snow accumulation, snowmelt, evapotranspiration, and soil water storage. Although the processes of sediment transfer and debris flow generation are described in a simplified manner, the model produces complex sediment discharge behavior which is driven by the availability of sediment and antecedent wetness conditions (system memory) as well as the triggering potential (climatic forcing). The observed probability distribution of debris flow volumes and their seasonality in 2000-2009 are reproduced. The stochasticity of hillslope sediment input is important for reproducing realistic sediment storage variability, although many details of the hillslope landslide triggering procedures are filtered out by the sediment transfer system. The model allows us to explicitly quantify the division into transport and supply-limited sediment discharge events. We show that debris flows may be generated for a wide range of rainfall intensities because of variable antecedent basin wetness and snowmelt contribution to runoff, which helps to understand the limitations of methods based on a single rainfall threshold for debris flow initiation in Alpine basins.

  15. Reservoir quality and petrophysical properties of Cambrian sandstones and their changes during the experimental modelling of CO2 storage in the Baltic Basin

    Directory of Open Access Journals (Sweden)

    Kazbulat Shogenov

    2015-08-01

    Full Text Available The objectives of this study were (1 to review current recommendations on storage reservoirs and classify their quality using experimental data of sandstones of the Deimena Formation of Cambrian Series 3, (2 to determine how the possible CO2 geological storage (CGS in the Deimena Formation sandstones affects their properties and reservoir quality and (3 to apply the proposed classification to the storage reservoirs and their changes during CGS in the Baltic Basin. The new classification of the reservoir quality of rocks for CGS in terms of gas permeability and porosity was proposed for the sandstones of the Deimena Formation covered by Lower Ordovician clayey and carbonate cap rocks in the Baltic sedimentary basin. Based on permeability the sandstones were divided into four groups showing their practical usability for CGS (‘very appropriate’, ‘appropriate’, ‘cautionary’ and ‘not appropriate’. According to porosity, eight reservoir quality classes were distinguished within these groups. The petrophysical, geochemical and mineralogical parameters of the sandstones from the onshore South Kandava and offshore E6 structures in Latvia and the E7 structure in Lithuania were studied before and after the CO2 injection-like alteration experiment. The greatest changes in the composition and properties were determined in the carbonate-cemented sandstones from the uppermost part of the South Kandava onshore structure. Partial dissolution of pore-filling carbonate cement (ankerite and calcite and displacement of clay cement blocking pores caused significant increase in the effective porosity of the samples, drastic increase in their permeability and decrease in grain and bulk density, P- and S-wave velocity, and weight of the dry samples. As a result of these alterations, carbonate-cemented sandstones of initially ‘very low’ reservoir quality (class VIII, ‘not appropriate’ for CGS, acquired an ‘appropriate’ for CGS

  16. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, Élisabeth

    2011-01-21

    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations of the velocities of spheres to increase with the size of the container, whereas experiments found no such variation. Two ideas have increased our understanding. First, the correlation length of the velocity fluctuations was found experimentally to be 20 interparticle separations. Second, in dilute suspensions, a vertical variation in the concentration due to the spreading of the front with the clear fluid can inhibit the velocity fluctuations. In a very dilute regime, a homogeneous suspension of fibers suffers a spontaneous instability in which fast descending fiber-rich columns are separated by rising fiber-sparse columns. In a semidilute regime, the settling is hindered, more so than for spheres. © 2011 by Annual Reviews. All rights reserved.

  17. Assessing the potential toxicity of resuspended sediment

    Energy Technology Data Exchange (ETDEWEB)

    Bonnet, C.; Babut, M.; Ferard, J.F.; Martel, L.; Garric, J.

    2000-05-01

    Two moderately contaminated freshwater sediments (Sorel Harbour, St. Lawrence River, Canada) were subjected to a suspension event. The objective was to assess the environmental impact of the disposal of dredged material in water, in particular, the short-term effects of dumping on the water column and the long-term effects of dredged sediment deposits. In a series of microcosms, the sediments were left to stand for 25 d under flow-through conditions. In a second series of microcosms, sediments were vigorously suspended for 15 min before being left to settle and were submitted to the same treatment as reference sediments during the following 25 d. Physicochemical and biological parameters (Daphnia magna and Hydra attenuata survival) were measured in overlying water throughout the experiment. Sediment toxicity was assessed with Chironomus tentans and Hyalella azteca exposed to sediments collected at both the beginning and end of the 25-d period. Pore-water toxicity was evaluated with D. magna. During the suspension process, in the Sorel Harbour mixed sediment overlying water, the authors observed effects on H. attenuata survival and ammonia and metals (chromium, copper, and zinc) releases. Meanwhile, in reference (nonmixed) and mixed sediments as well as in associated pore waters, there were no significant chemical modifications no biological effects after the 25-d experiments. The developed approach, which attempts to simulate a dumping process, aims at allowing the assessment of the short- and long-term hazards resulting from a resuspension process in overlying water and in resettled sediments using both chemical and biological measurements.

  18. Biogenic silicate accumulation in sediments, Jiaozhou Bay

    Institute of Scientific and Technical Information of China (English)

    LI Xuegang; SONG Jinming; DAI Jicui; YUAN Huamao; LI Ning; LI Fengye; SUN Song

    2006-01-01

    It has been widely recognized that low silicate content in seawater is a major limiting factor to phytoplankton primary production in Jiaozhou Bay. However the reason of Si-limitation remains poorly understood. In the present study we measured the biogenic silicate content and discussed the accumulation of silicate in Jiaozhou Bay sediment. The results show that the biogenic silica content in the sediment of the Jiaozhou Bay is obviously much higher than those in the Yellow Sea and the Bohai Sea. The BSi:TN ratios and BSi:16P ratios in the sediment are > 1 and the OC:BSi ratio in sediment is lower than these of Redfield ratio (106:16), indicating that the decomposition rate of OC is much higher than that for BSi in similar conditions. Therefore, the majority of the biogenic silicate was buried and thus did not participate in silicate recycling. Silicate accumulation in sediment may explain why Si limits the phytoplankton growth in the Jiaozhou Bay. Comparing the flux of biogenic silicate from sediments with primary production rate, it can be concluded that only 15.5% of biogenic silicate is hydrolyzed during the journey from surface to bottom in seawater, thus approximate 84.5% of biogenic silicate could reach the bottom. The silicate releasing rate from the sediment to seawater is considerably lower than that of sedimentation of biogenic silicate, indicating silicate accumulation in sediment too. In a word, the silicate accumulation in sediment is the key reason of silicate limiting to phytoplankton growth in Jiaozhou Bay.

  19. Hanford contaminated sediment stabilization studies

    Energy Technology Data Exchange (ETDEWEB)

    Bruns, L.E.; Key, K.T.; Higley, B.A.

    1977-03-01

    The major problems with radionuclide waste sites in the 200 Area plateau on the Hanford Reservation is the high degree of toxicity or Hazard Index (HI). Transport Factors (TF) are fortunately low but can increase with time and certainly with episodic events such as explosions or earthquakes. Two major tests involving surface affixation were sponsored by the Atlantic Richfield Hanford Company, one by Dowell using M-166 and the other by Battelle-Northwest comparing many different surface affixants. The latex emulsion, M-166, appeared to be well suited for the Hanford desert type area. Of the many surface affixants tested by Battelle-Northwest, Coherex and Aerospray appeared to be the best. As an emergency precaution, 200 barrels of M-166 were purchased for surface affixation in case of a range fire. The subsurface affixants laboratory and field tests include organic polymers, asphalt emulsions, concrete, AM-9, and sodium silicate-calcium chloride-foramide grouts. The applications were second containment (or leak prevention) of subsurface waste tanks and piping, grouting water wells to prevent contamination leaking to the water table, and encompassing cribs, trenches, burial grounds, and other subsurface sediment contaminations. Organic polymers added strength to the soil, but penetration of the viscous liquid was not as deep as desired; it may be good for situations requiring only a few inches penetration, such as well grouting. The asphalt emulsion looked promising as an easily injected well grouting material and it may also be good for encompassing subsurface contaminated sediment plumes. The sodium silicate-calcium chloride-foramide affixant appeared best for second containment of waste tanks but may require the help of asphalt emulsion to ensure good coverage.

  20. Interstitial brines in playa sediments

    Science.gov (United States)

    Jones, B.F.; Van Denburgh, A.S.; Truesdell, A.H.; Rettig, S.L.

    1969-01-01

    Study of several closed drainages in the Great Basin has shown that the interstitial solutions of shallow, fine-grained playa deposits store a large quantity of dissolved solids and are often more concentrated than associated lakes and ponds, except in peripheral zones of stream or ground-water inflow. These interstitial fluids, when compared with local runoff, impoundments, or spring waters, commonly have a distinctive ionic composition which sometimes cannot be explained by either simple mixing of surface and subsurface inflow or by evaporative concentration. At Abert Lake, Oregon, the interstitial solute concentrations increased with depth to values as much as five times greater than the lake, except where springs indicate significant ground-water input. Where Na+, Cl, and CO2 species constitute more than 90% of the solutes, Na+ Cl- ratios in the lake water are lower than in interstitial solutions of bottom cores and higher than in playa fluids. At the same time, Na+ K+ ratios are highest in the fluids of lake bottom muds and lowest in playa interstitials. In deeper playa profiles, interstitial Na+ Cl- tended to decrease with depth (5 ft. maximum). In the Abert Lake area, as in other parts of the western Great Basin, Na+ Cl- ratios are indicative of total CO2 in solution and the effects of organic decay in surficial sediments. These ratios, coupled with data on silica and bulk density, show that higher PCO2 accompanying decay promotes silicate dissolution and hydrogen ion exchange, stripping alkalis from sediment which had preferentially adsorbed K+ when entering the lake. On subsequent loss of pore fluid in the playa regime, silica initially released to solution in the lake environment is readsorbed on dissolution products. ?? 1969.

  1. Effects of tubificid bioturbation on pore structures in sediment and the migration of sediment particles.

    Science.gov (United States)

    Li, Yaorui; Hua, Xiuyi; Zheng, Fang; Dong, Deming; Liang, Dapeng; Guo, Zhiyong

    2016-04-01

    In this study, the effects of tubificid bioturbation near the water-sediment interface on pore structures and the migration of sediment particles were evaluated using a series of simulations. In these experiments, the distribution and variation of the tubificid burrows and the macropores in the sediment were investigated by X-ray computed tomography (CT) and digital image collecting, without sampling or disturbing the sediment. The migration of the sediment particles was also determined using CT by adding BaSO4 microspheres to the sediment as a tracer. The effects of tubificid bioturbation on the distribution and migration of contaminants in the sediment were verified by adding Pb-containing sediment layers to the sediment. The results indicate that after the addition of the tubificids, both the burrows and the macropores in the sediments increased with time, and the rate of increase slowed gradually. With the increased worm density, the burrows and the pore structures also increased. The in-depth distribution of the burrows and macropores was determined by the settlement time of the worms: with the settlement time increasing from 3 to 19 days, the depth of the zone with the highest density of burrows and macropores increased from 0-30 to 30-50 mm and from 0-10 to 30-60 mm, respectively. The distribution of the burrows and macropores was closely related to the distribution of the tubificids. Thickening of the oxidized zones in the superficial sediments in the presence of tubificid bioturbation was also observed. The main action of tubificids on the sediment particles was the transport of particles from the inner sediment (especially in the range of 30-50 mm in depth) to the water-sediment interface. The migration of Pb in the contaminated sediment with tubificid bioturbation could be interpreted by the variation in the burrows and macropores and the migration of sediment particles. Both the formation and the variation in the burrows and macropores, as well as

  2. 华中西南区一条国际前寒武系与寒武系界线层型补充剖面%A SUPPLEMENTAL PRECAMBRIAN-CAMBRIAN BOUNDARY GLOBAL STRATOTYPE SECTION IN SW CHINA

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Since 1992, the siliciclastic Fortune Head section(southeastern Newfoundland, Canada) and the base of the Trichophycus pedium trace fossil zone have together served as the Precambrian-Cambrian(PreC-C) boundary global stratotype section and point(GSSP). However, the fact that the Fortune Head section consists mainly of siliciclastic rocks makes it difficult to correlate this section with boundary sections consisting mainly of carbonate rocks, which contain abundant small shelly fossils(SSFs) and can also be correlated using stable carbon isotope data. We propose that a predominantly carbonate section near the town of Dahai, eastern Yunnan Province, southwestern China, be designated a supplementary stratotype for the PreC-C boundary GSSP, for the following reasons:(1) the Dahai section is continuous, consisting of the Neoproterozoic Baiyanshao and Daibu members conformably overlain by the Early Cambrian Zhongyicun and Dahai members and Shiyantou Formation; (2) the Early Cambrian units contain abundant SSFs representing four assemblage zones; (3) the Dahai section can be correlated with numerous other sections using stable C isotopic chemostratigraphy; (4) the famous Meishucun section, located not far from Dahai, contains both abundant SSFs and trace fossils and can be readily correlated with the SSF-rich Dahai section. We further propose that the base of the Cambrian System be placed at the base of the first SSF assemblage zone(the Anabarites-Protohertzina Zone), which in the Dahai section coincides with the base of Bed 11.%1992年,全球前寒武系与寒武系界线层型剖面和层型点确定在加拿大纽芬兰东南幸运角剖面,并以遗迹化石带Trichophycus pedium的底作为前寒武系与寒武系的分界点。但是,幸运角剖面主要是以硅质碎屑岩相为主,难以与含有丰富小壳化石和具有可对比的稳定同位素资料的碳酸盐相界线剖面进行对比。为此,提出我国云南会泽大海附近的一条以

  3. 浙黔桂地区寒武纪硅质岩的地球化学特征及其形成背景%Geochemistry and tectonic setting of the Cambrian siliceous rocks in the Zhejiang-Guangxi-Guizhou zone

    Institute of Scientific and Technical Information of China (English)

    黄华; 王国芝

    2011-01-01

    The tectonic setting of the Cambrian siliceous rocks in the Zhejiang-Guangxi-Guizhou zone are discussed with the aid of major and rare earth element geochemistry. In the siliceous rocks, Al2O3/( A12O3 + Fe2O3) ratios range from 0.56 to 0.87. Ce/Ce * ratios equal to 0.74 ± 0.19. Lan/Cen ratios range from 0.90 to 1.58. Average values of Lan/Ybn ratios equal to 6.38. All these results show that the Cambrian siliceous rocks in the Zhejiang-Guangxi-Guizhou zone were formed in the continental-margin environment or transitional zone from the continental margin to deep sea. LREEs are more enriched in the siliceous rocks from early rift basins than those from the ancient Huanan residual oceanic basin and Yangtze block. The siliceous rocks formed during tectonic extension tend to have hydrothermal origin, and display the REE distribution patterns of being depleted in LREE and positive Eu anomaly. The siliceous rocks formed during stable tectonism tend to be sedimentary in origin, and display the REE distribution patterns of being relative enriched in LREE and slight negative Eu anomaly. The differences in the REE distribution patterns cited above indicate the episodic extension during the Cambrian. The negative Ce anomaly in the siliceous rocks on the margins of the Yangtze platform implies that the large-scale EW-trending overthrusting once occurred in the Jiangnan orogenic zone after the Cambrian.%本文采用常量和稀土元素地球化学方法对浙黔桂地区寒武纪硅质岩的形成背景进行了研究.研究表明,硅质岩的AlO/(AlO+FeO)为0.56~0.87;Ce/Ce为0.74±0.19;La/Ce为0.90~1.58;La/Yb平均为6.38,轻稀土明显富集,这些特征表明研究区硅质岩形成于大陆边缘环境或大陆边缘与深海过渡带.形成于裂陷盆地初期的硅质岩,比古华南残留洋盆和扬子陆块边缘的硅质岩轻稀土元素更加富集.构造拉张期形成的硅质岩为热液成因硅质岩,其稀土配分模式显示出轻稀土相对亏损

  4. Managing Fine Sediment in Regulated Rivers

    Science.gov (United States)

    Schmidt, J. C.

    2015-12-01

    A paradigm useful in managing dams and diversions is that the combined effects of changing flow regime and sediment supply perturb regulated rivers into sediment deficit or sediment surplus. In the U.S. Southwest, large dams constructed on interregional rivers typically create sediment deficit segments >100 km long. Further downstream, sediment surplus may occur if desert tributaries deliver sufficient amounts of fine sediment, such as parts of the Rio Grande, lower Green River, and Colorado River delta. Sediment surplus also occurs on most smaller regional rivers. The protocols for managing rivers perturbed into sediment deficit have been refined for the Colorado River downstream from Glen Canyon Dam but are nonetheless challenged by externally determined water-supply agreements that require annual water deliveries that sometimes occur when there has been little tributary resupply. Virtually all of the naturally supplied sand to the depleted, 100-km long Marble Canyon comes from the Paria River. The sand delivery rate since 2012 was sufficiently large to trigger short-duration controlled floods under the High Flow Experiment (HFE) Protocol. The sand mass balance of Marble Canyon since 2012 when the HFE Protocol was adopted was positive due to the combination of relatively large sand delivery from the Paria River and average total annual flows. Large total annual flows have the potential to export large amounts of sand and create a negative sand mass balance. Despite the challenge of managing a scarce and highly variable sand supply and occasional years of large reservoir releases, the long-term (2006-2015) sand mass balance for the upstream half of Marble Canyon is indeterminant and is positive for the downstream half of Marble Canyon. The apparent success of managing sand in Grand Canyon under deficit conditions suggests that fine sediment management protocols might be developed for other regulated rivers. Implementation would require establishment of networks of

  5. Temporal variability of suspended sediment sources in an alpine catchment combining river/rainfall monitoring and sediment fingerprinting

    OpenAIRE

    Navratil, O.; Evrard, O.; Esteves, Michel; Legout, C.; Ayrault, S.; Nemery, J.; Mate-Marin, A.; .M. Ahmadi; Lefevre, I.; Poirel, A.; Bonte, P.

    2012-01-01

    Influence of the rainfall regime on erosion and transfer of suspended sediment in a 905-km(2) mountainous catchment of the southern French Alps was investigated by combining sediment monitoring, rainfall data, and sediment fingerprinting (based on geochemistry and radionuclide concentrations). Suspended sediment yields were monitored between October 2007 and December 2009 in four subcatchments (22-713km(2)). Automatic sediment sampling was triggered during floods to trace the sediment origin ...

  6. Comparative research on Cambrian Burgess Shale-type soft-bodied fossil biotas in South China%华南布尔吉斯页岩型软躯体化石生物群对比研究

    Institute of Scientific and Technical Information of China (English)

    段艳红; 韩健; 张志飞; 刘建妮

    2012-01-01

    Aim To combing from the Burgess Shale-type fossil biotas in South China at the sight of horizon, biological composition and sedimentary environment. Methods Ten Burgess Shale-type soft-bodied fossil biotas in South China are investigated by comparing the geological settings, biological composition and their substrates. Results Except for the Yanjiahe biota, the other nine Cambrian Burgess Shale-type soft-bodied fossil biotas in South China represent a series of closely-related biological communities lived in muddy-sandy substrates which show gradually transitions in biological composition in time-space distributions. Conclusion The Burgess Shale-type fossil biota in South China should have a wider distribution during the Middle-Late Cambrian.%目的 梳理华南布尔吉斯页岩型软躯体化石生物群的产出层位、生物面貌和沉积环境.方法 对10个华南布尔吉斯页岩型软躯体化石生物群进行对比研究.结果 除了岩家河生物群之外的9个布尔吉斯页岩型生物群代表了一系列生活在泥砂质基底的、从时空分布上逐渐过渡的具有高度相关性的生物群落.结论 布尔吉斯页岩型化石生物群在中晚寒武世应该会有更大规模的分布.

  7. The Cambrian initiation of intra-oceanic subduction in the southern Paleo-Asian Ocean: Further evidence from the Barleik subduction-related metamorphic complex in the West Junggar region, NW China

    Science.gov (United States)

    Liu, Bo; Han, Bao-Fu; Xu, Zhao; Ren, Rong; Zhang, Jin-Rui; Zhou, Jing; Su, Li; Li, Qiu-Li

    2016-06-01

    In this study, we present new evidence from the Barleik subduction-related metamorphic complex in the southern West Junggar region, northwestern China, for the Cambrian initiation of intra-oceanic subduction in the southern Paleo-Asian Ocean. The Barleik metamorphic complex is mainly composed of blueschist and amphibolite blocks within an ophiolitic mélange and their protoliths are calc-alkaline andesite and alkali and tholeiitic basalts. The calc-alkaline andesite has a zircon U-Pb age of 502 ± 2 Ma, obtained from magmatic cores of zircon grains, and shares geochemical features similar to the 515-485 Ma intra-oceanic arc magmatic rocks in the West Junggar region. By contrast, the alkali and tholeiitic basalts have trace element features similar to ocean island and enriched mid-ocean ridge basalts, respectively. Rutile and sodic-calcic amphibole from the amphibolite have a U-Pb age of 502 ± 25 Ma and a 40Ar/39Ar age of ∼504 Ma, respectively, which are in good agreement within errors with a 40Ar/39Ar age of 492 ± 4 Ma for phengite from the blueschist. These metamorphic ages of ∼500 Ma are interpreted to represent the timing of Pacific-type subduction-related metamorphism and are also compatible with ages of the oldest supra-subduction zone ophiolites (531-512 Ma) and intra-oceanic arc plutons (515-485 Ma) in the southern West Junggar region. Being one of the oldest subduction-related metamorphic complexes (509-490 Ma) in the southern Central Asian Orogenic Belt, the Barleik metamorphic complex, together with the oldest arc plutons, definitely indicate the initial intra-oceanic subduction in the southern Paleo-Asian Ocean at least in the Early Cambrian.

  8. Deposited sediment settlement and consolidation mechanisms

    Directory of Open Access Journals (Sweden)

    Shuai-jie Guo

    2015-10-01

    Full Text Available In order to study deposited sediment settlement and consolidation mechanisms, sediment settlement experiments were conducted using a settlement column. Based on the experimental results, sediment settlement stage definition, excessive pore pressure (EPP dissipation, and consolidation constitutive equations are discussed. Three stages, including the free settlement, hindered settlement, and self-weight consolidation settlement stages, are defined. The results of this study show that sediment settlement is mainly affected by the initial sediment concentration and initial settlement height, and the interface settlement rate is attenuated linearly with time on bilogarithmic scales during the hindered settlement and self-weight consolidation settlement stages. Moreover, the deposited sediment layer in the self-weight consolidation settlement stage experiences large strains, and the settlement amount in this stage is about 32% to 59% of the initial height of deposited sediment. EPP is nonlinearly distributed in the settlement direction, and consolidation settlement is faster than EPP dissipation in the self-weight consolidation settlement stage. Consolidation constitutive equations for the hydraulic conductivity and effective stress, applicable to large-strain consolidation calculation, were also determined and fitted in the power function form.

  9. Erosion, sediment transportation and accumulation in rivers

    Institute of Scientific and Technical Information of China (English)

    N.I.ALEKSEEVSKIY; K.M.BERKOVICH; R.S.CHALOV

    2008-01-01

    The present paper analyses the interrelation between erosion,sediment transportation and accumulation proposed by N.I.Makkaveyev (1908-1983) and its further development in modem studies of river channel processes in Russia.Spatio-temporal linkages between erosion and accumulation are defined considering channel processes at different scales - river longitudinal profile,channel morphological patterns,alluvial bedforms (bars,dunes) and individual sediment particles.Relations between river geomorphic activity,flow transportation capacity and sediment budgets are established (sediment input and output;channel bed erosion and sediment entrainment into flow -termination of sediment transport and its deposition).Channel planforms,floodplain segments separated by the latter and alluvial channel bedforms are shown to be geomorphic expressions of sediment transport process at different spatial and temporal scales.This paper is dedicated to the 100th anniversary of N.I.Makkaveyev,Professor of the Moscow State University,author of the book "River channel and erosion in its basin" (1955).That book is regarded in Russia as the pioneering work which initiated the complex hydrological and geographical studies of channel processes and laid a basis for the theory of unified fluvial erosion-accumulation process.

  10. Multi-Fraction Bayesian Sediment Transport Model

    Directory of Open Access Journals (Sweden)

    Mark L. Schmelter

    2015-09-01

    Full Text Available A Bayesian approach to sediment transport modeling can provide a strong basis for evaluating and propagating model uncertainty, which can be useful in transport applications. Previous work in developing and applying Bayesian sediment transport models used a single grain size fraction or characterized the transport of mixed-size sediment with a single characteristic grain size. Although this approach is common in sediment transport modeling, it precludes the possibility of capturing processes that cause mixed-size sediments to sort and, thereby, alter the grain size available for transport and the transport rates themselves. This paper extends development of a Bayesian transport model from one to k fractional dimensions. The model uses an existing transport function as its deterministic core and is applied to the dataset used to originally develop the function. The Bayesian multi-fraction model is able to infer the posterior distributions for essential model parameters and replicates predictive distributions of both bulk and fractional transport. Further, the inferred posterior distributions are used to evaluate parametric and other sources of variability in relations representing mixed-size interactions in the original model. Successful OPEN ACCESS J. Mar. Sci. Eng. 2015, 3 1067 development of the model demonstrates that Bayesian methods can be used to provide a robust and rigorous basis for quantifying uncertainty in mixed-size sediment transport. Such a method has heretofore been unavailable and allows for the propagation of uncertainty in sediment transport applications.

  11. Modeling sediment transport in river networks

    Science.gov (United States)

    Wang, Xu-Ming; Hao, Rui; Huo, Jie; Zhang, Jin-Feng

    2008-11-01

    A dynamical model is proposed to study sediment transport in river networks. A river can be divided into segments by the injection of branch streams of higher rank. The model is based on the fact that in a real river, the sediment-carrying capability of the stream in the ith segment may be modulated by the undergone state, which may be erosion or sedimentation, of the i-1th and ith segments, and also influenced by that of the ith injecting branch of higher rank. We select a database about the upper-middle reach of the Yellow River in the lower-water season to test the model. The result shows that the data, produced by averaging the erosion or sedimentation over the preceding transient process, are in good agreement with the observed average in a month. With this model, the steady state after transience can be predicted, and it indicates a scaling law that the quantity of erosion or sedimentation exponentially depends on the number of the segments along the reach of the channel. Our investigation suggests that fluctuation of the stream flow due to random rainfall will prevent this steady state from occurring. This is owing to the phenomenon that the varying trend of the quantity of erosion or sedimentation is opposite to that of sediment-carrying capability of the stream.

  12. 寒武系盐盆地的分布特征及其对中国成盐找钾的意义%Distribution of Cambrian Salt Basin and Its Significance for Halite and Potash Explorations in China

    Institute of Scientific and Technical Information of China (English)

    王淑丽; 郑绵平

    2013-01-01

    寒武系膏盐岩在世界范围内广泛分布,以亚洲寒武系分布最为广泛,含盐岩系主要分布在俄罗斯东西伯利亚、伊朗—印度—巴基斯坦—阿曼和中国.东西伯利亚、伊朗—印度—巴基斯坦均有钾盐发现.构造基底性质对钾盐盆地的形成具有关键性控制作用:稳定构造区在准稳定区有利聚钾;准稳定区在局部稳定构造区利于聚盐成钾,如形成于早寒武世的涅帕钾盐矿床——世界上大型钾盐矿之一,即位于前寒武纪地层为基底的古拗陷区.中国主要的古代盐盆地多发育于以前寒武纪为基底的准克拉通(陆块)中.近年来,随着油气勘查和盐业开发工作,中国上扬子陆块、华北陆块和塔里木陆块相继发现了4个大型的膏盐岩盆地.上扬子陆块与塔里木陆块发现单层厚度较大的岩盐沉积及较好的成钾水化学显示,为在中国寒武系蒸发岩盆地开展成盐找钾工作提供了重要依据.%The wide distribution of the Cambrian rock gypsum and salt is an important feature of older strata in Asia. The Cambrian salt-bearing sequences are mainly distributed in East Siberia of Russia, Iran, Oman, India, Pakistan, and China. Potash salts are also found in East Siberia, Iran, India, and Pakistan. The nature of the tectonic basement is a key controlling factor for the formation of potash basins. The stable tectonic region is favorable for the potash concentration in a quasi-stable region, and the quasi-stability is favorable for the salt concentration and the potash formation in a local stable tectonic region. For example, one of the largest potash deposits in the world-the Siberian Nepa potash deposit was formed in the Early Cambrian in the palae-depression of Precambrian strata. China's major ancient saline basins are in quasi-cratons (continental block) with the Precambrian basement. In China, only one solid potash deposit in Yunnan can be exploited. However, there are a number of

  13. Equilibrium sediment transport in lower Yellow River during later sediment-retaining period of Xiaolangdi Reservoir

    Institute of Scientific and Technical Information of China (English)

    Shao-lei Guo; Dong-po Sun; En-hui Jiang; Peng Li

    2015-01-01

    The Xiaolangdi Reservoir has entered the later sediment-retaining period, and new sediment transport phenomena and channel re-estab-lishing behaviors are appearing. A physical model test was used to forecast the scouring and silting trends of the lower Yellow River. Based on water and sediment data from the lower Yellow River during the period from 1960 to 2012, and using a statistical method, this paper analyzed the sediment transport in sediment-laden flows with different discharges and sediment concentrations in the lower Yellow River. The results show that rational water-sediment regulation is necessary to avoid silting in the later sediment-retaining period. The combination of 3 000 m3/ssediment concentration) at the Huayuankou section is considered an optimal combination for equilibrium sediment transport in the lower Yellow River over a long period of time.

  14. The suspended sediment transport equation and its near-bed sediment flux

    Institute of Scientific and Technical Information of China (English)

    LI RuiJie; LUO Feng; ZHU WenJin

    2009-01-01

    The suspended sediment transport equation and its near-bed sediment flux are one of the key prob-lems of sediment transport research under nonequilibrium condition. Based on the three-dimensional primitive suspended transport equation, the two-dimensional suspended sediment transport equation is deduced. The derived process indicates that the physical essence of the near-bed sediment flux is right the bottom boundary condition for the suspended sediment transport equation. This paper ana-lyzes the internal relations between the two methods of sediment carrying capacity and shear stress in common use, points out the consistency of these two methods in terms of form and physical meaning, and unifies these two methods theoretically. Furthermore, based on the analysis and comparison of the expressions of the near-bed sediment flux, this paper summarizes some problems to which attention should be paid, thus offering a novel approach to the study and the solution of the problems of sus-pended sediment transport and exchange flux of near-bed water sediment.

  15. A process-based model for aeolian sediment transport and spatiotemporal varying sediment availability

    Science.gov (United States)

    Hoonhout, Bas M.; Vries, Sierd de

    2016-08-01

    Aeolian sediment transport is influenced by a variety of bed surface properties, like moisture, shells, vegetation, and nonerodible elements. The bed surface properties influence aeolian sediment transport by changing the sediment transport capacity and/or the sediment availability. The effect of bed surface properties on the transport capacity and sediment availability is typically incorporated through the velocity threshold. This approach appears to be a critical limitation in existing aeolian sediment transport models for simulation of real-world cases with spatiotemporal variations in bed surface properties. This paper presents a new model approach for multifraction aeolian sediment transport in which sediment availability is simulated rather than parameterized through the velocity threshold. The model can cope with arbitrary spatiotemporal configurations of bed surface properties that either limit or enhance the sediment availability or sediment transport capacity. The performance of the model is illustrated using four prototype cases, the simulation of two wind tunnel experiments from literature and a sensitivity analysis of newly introduced parameters.

  16. Investigation about data reduction and sedimentation distance of sedimentation balance method

    Energy Technology Data Exchange (ETDEWEB)

    Fukui, K.; Yoshida, H.; Shiba, M.; Tokunaga, Y. [Hiroshima University, Hiroshima (Japan). Dept. of Chemical Engineering

    2000-06-01

    The sedimentation balance type particle size analyzer is improved. The slurry supply device was automated and the height of peripheral wall of the detective tray was raised. As a result we can acquire data of the sedimentation mass change accurately. Moreover, the ratio of measured total sedimentation mass to the theoretical total sedimentation mass was kept constant ranging from 1.00 to 1.02 independent of particle size. By the above improvement, we can develop a more precious sedimentation balance. Twomey's non-linear iteration method was applied to retrieve a particle size distribution from the sedimentation curve measured with a sedimentation balance method. It is found that the non-linear iteration method can calculate size distributions accurately. Furthermore, the influence of the thickness at the base of the detective tray on the sedimentation distance was also investigated. As a result, it is clarified that the change in detected mass did not depend on thickness at the base of the tray. Therefore, it is concluded that the sedimentation distance in the sedimentation balance method should be defined as the distance between the lower surface of the base of the tray and suspension surface. (author)

  17. The suspended sediment transport equation and its near-bed sediment flux

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The suspended sediment transport equation and its near-bed sediment flux are one of the key problems of sediment transport research under nonequilibrium condition. Based on the three-dimensional primitive suspended transport equation, the two-dimensional suspended sediment transport equation is deduced. The derived process indicates that the physical essence of the near-bed sediment flux is right the bottom boundary condition for the suspended sediment transport equation. This paper analyzes the internal relations between the two methods of sediment carrying capacity and shear stress in common use, points out the consistency of these two methods in terms of form and physical meaning, and unifies these two methods theoretically. Furthermore, based on the analysis and comparison of the expressions of the near-bed sediment flux, this paper summarizes some problems to which attention should be paid, thus offering a novel approach to the study and the solution of the problems of suspended sediment transport and exchange flux of near-bed water sediment.

  18. Microbial interactions with naturally occurring hydrophobic sediments: Influence on sediment and associated contaminant mobility.

    Science.gov (United States)

    Droppo, I G; Krishnappan, B G; Lawrence, J R

    2016-04-01

    The erosion, transport and fate of sediments and associated contaminants are known to be influenced by both particle characteristics and the flow dynamics imparted onto the sediment. The influential role of bitumen containing hydrophobic sediments and the microbial community on sediment dynamics are however less understood. This study links an experimental evaluation of sediment erosion with measured sediment-associated contaminant concentrations and microbial community analysis to provide an estimate of the potential for sediment to control the erosion, transport and fate of contaminants. Specifically the paper addresses the unique behaviour of hydrophobic sediments and the role that the microbial community associated with hydrophobic sediment may play in the transport of contaminated sediment. Results demonstrate that the hydrophobic cohesive sediment demonstrates unique transport and particle characteristics (poor settling and small floc size). Biofilms were observed to increase with consolidation/biostabilization times and generated a unique microbial consortium relative to the eroded flocs. Natural oil associated with the flocs appeared to be preferentially associated with microbial derived extracellular polymeric substances. While PAHs and naphthenic acid increased with increasing shear (indicative of increasing loads), they tended to decrease with consolidation/biostabilization (CB) time at similar shears suggesting a chemical and/or biological degradation. PAH and napthenic acid degrading microbes decreased with time as well, which may suggest that there was a reduced pool of PAHs and naphthenic acids available resulting in their die off. This study emphasizes the importance that any management strategies and operational assessments for the protection of human and aquatic health incorporate the sediment (suspended and bed sediment) and biological (biofilm) compartments and the energy dynamics within the system in order to better predict contaminant

  19. Improving Fishpond Sediment by Aquatic Vegetable Rotation

    Directory of Open Access Journals (Sweden)

    Ling Tao

    2012-10-01

    Full Text Available Continuously intensive fish farming results in pond degradation that needs to be improved. Therefore, the experiment rotating intensive fish culture with two aquatic vegetables lotus (Nelumbo nucifera and water chestnuts (Eleocharis dulcis cultivation is conducted aiming at determining the effect of rotation as a sediment management technique on improving the pond sediment and assessing the food safety risk of the vegetables cultivated in the pond sediment from the aspects of heavy metal. The results showed that after rotation, the content of Total Nitrogen (TN and Organic Matter (OM in the upper 10 cm sediment decreased significantly (p<0.05, with TN content reduced 1.05 and 0.74 g/kg; OM content reduced 0.59 and 0.37%, respectively. The contents of Organic-Phosphorus (OP and Fe/Al-bound Phosphorus (Fe/Al-P in the sediment decreased significantly (p<0.05, with OP reduced 0.05 and 0.04 g/kg, Fe/Al-P reduced 0.19 and 0.15 g/kg, respectively. The heavy metal contents of As, Pb, Cd, Hg, Cr and Zn except Cu in the pond sediment were under Chinese National II Soil Criterion and the contents of As, Pb, Cd, Hg, Cr, Cu and Zn in edible vegetable rhizomes satisfied Safety Requirements for Non-environmental Pollution Vegetable. Rotation of fish culture with aquatic vegetables cultivation effectively mitigated excessive nutrient load in the sediment while recycled the nutrient in the sediment to produce safe vegetables. It could be considered as a viable sediment quality improving technique.

  20. Sedimentation in mountain streams: A review of methods of measurement

    Science.gov (United States)

    Hedrick, Lara B.; Anderson, James T.; Welsh, Stuart; Lin, Lian-Shin

    2013-01-01

    The goal of this review paper is to provide a list of methods and devices used to measure sediment accumulation in wadeable streams dominated by cobble and gravel substrate. Quantitative measures of stream sedimentation are useful to monitor and study anthropogenic impacts on stream biota, and stream sedimentation is measurable with multiple sampling methods. Evaluation of sedimentation can be made by measuring the concentration of suspended sediment, or turbidity, and by determining the amount of deposited sediment, or sedimentation on the streambed. Measurements of deposited sediments are more time consuming and labor intensive than measurements of suspended sediments. Traditional techniques for characterizing sediment composition in streams include core sampling, the shovel method, visual estimation along transects, and sediment traps. This paper provides a comprehensive review of methodology, devices that can be used, and techniques for processing and analyzing samples collected to aid researchers in choosing study design and equipment.

  1. Remediation technologies for oil-contaminated sediments.

    Science.gov (United States)

    Agarwal, Ashutosh; Liu, Yu

    2015-12-30

    Oil-contaminated sediments pose serious environmental hazards for both aquatic and terrestrial ecosystems. Innovative and environmentally compatible technologies are urgently required to remove oil-contaminated sediments. In this paper, various physical, chemical and biological technologies are investigated for the remediation of oil-contaminated sediments such as flotation and washing, coal agglomeration, thermal desorption, ultrasonic desorption, bioremediation, chemical oxidation and extraction using ionic liquids. The basic principles of these technologies as well as their advantages and disadvantages for practical application have been discussed. A combination of two or more technologies is expected to provide an innovative solution that is economical, eco-friendly and adaptable.

  2. Non-uniform sediment incipient velocity

    Institute of Scientific and Technical Information of China (English)

    Haitao XU; Jinyou LU; Xiaobin LIU

    2008-01-01

    Based on the mechanism of non-uniform sediment incipient motion,the dragging force and uplift force coefficient expressions are put forward for the non-uniform bed material exposure and close alignment state.The incipient veiocity formula of the non-uniform sediment is then established.It is shown that the formula structure is reasonable,and fine particles of the non-uniform sediment are more difficult to set into motion than the same sized uniform particles,whereas coarser particles are easier to set into motion than their uniform equivalents.The validity of the formula is verified by field and experiment data.

  3. Mercury enrichment in sediments of Amba estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Ram, A.; Rokade, M.A.; Zingde, M.D.

    transferred to clean polyethylene bags and frozen at -20°C until analysed. Prior to analysis, the sediment was dried below 60°C in an electric oven and powdered in an agate mortar. A weighed portion of the powdered sediment was digested in aqua regia...-1 as against the certified value of 4.57 ± 0.16 µg g-1. For the estimation of Al, Fe and Mn, the powdered sediment sample was brought into solution22 by digesting with concentrated HF, HClO4 and HNO3 and the residue remaining after evaporation...

  4. What controls sediment flux in dryland channels?

    Science.gov (United States)

    Michaelides, K.; Singer, M. B.

    2010-12-01

    Theories for the development of longitudinal and grain size profiles in perennial fluvial systems are well developed, allowing for generalization of sediment flux and sorting in these fluvial systems over decadal to millennial time scales under different forcings (e.g., sediment supply, climate changes, etc). However, such theoretical frameworks are inadequate for understanding sediment flux in dryland channels subject to spatially and temporally discontinuous streamflow, where transport capacity is usually much lower than sediment supply. In such fluvial systems, channel beds are poorly sorted with weak vertical layering, poorly defined bar forms, minimal downstream fining, and straight longitudinal profiles. Previous work in dryland channels has documented sediment flux at higher rates than their humid counterparts once significant channel flow develops, pulsations in bed material transport under constant discharge, and oscillations in dryland channel width that govern longitudinal patterns in erosion and deposition. These factors point to less well appreciated controls on sediment flux in dryland valley floors that invite further study. This paper investigates the relative roles of hydrology, bed material grain size, and channel width on sediment flux rates in the Rambla de Nogalte in southeastern Spain. Topographic valley cross sections and hillslope and channel particle sizes were collected from an ephemeral-river reach. Longitudinal grain-size variation on the hillslopes and on the channel bed were analysed in order to determine the relationship between hillslope supply characteristics and channel grain-size distribution and longitudinal changes. Local fractional estimates of bed-material transport in the channel were calculated using a range of channel discharge scenarios in order to examine the effect of channel hydrology on sediment transport. Numerical modelling was conducted to investigate runoff connectivity from hillslopes to channel and to examine the

  5. Sediment pollution and dynamic in the Mar Piccolo of Taranto (southern Italy): insights from bottom sediment traps and surficial sediments.

    Science.gov (United States)

    Bellucci, Luca Giorgio; Cassin, Daniele; Giuliani, Silvia; Botter, Margherita; Zonta, Roberto

    2016-07-01

    Major and trace element, PAH, and PCB concentrations were measured in surface sediments and particles from sediment traps collected in the First and Second Basin of the Mar Piccolo (Gulf of Taranto) in two periods (June-July and August-September, 2013). The aim of the study was to evaluate pollution degree, sediment transport and particle redistribution dynamic within the area. Results confirm the higher contamination of sediments from the First Basin observed by previous researches, particularly for Cu, Hg, Pb, total PAHs, and total PCBs. Advective transport from the First to the Second Basin appears to be the leading transfer mechanism of particles and adsorbed contaminants, as evidenced by measured fluxes and statistical analyses of contaminant concentrations in surficial sediments and particles from sediment traps. Long-range selective transports of PAHs and microbial anaerobic degradation processes for PCBs have been also observed. These results are limited to a restricted time window but are consistent with the presence of transport fluxes at the bottom of the water column. This mechanism deserves further investigation and monitoring activities, potentially being the main responsible of pollutant delivering to the less contaminated sectors of the Mar Piccolo.

  6. A probabilistic sediment cascade model of sediment transfer through a mountain basin

    Science.gov (United States)

    Bennett, G. L.; Molnar, P.; McArdell, B. W.; Lane, S. N.; Burlando, P.

    2013-12-01

    Mountain basin sediment discharge poses a significant hazard to the downstream population, particularly in the form of debris flows. The importance and sensitivity of snow and ice melt processes in mountain basins along with their rapid rainfall-runoff response makes mountain basin sediment discharge particularly responsive to climate change. It is important to understand and model sediment transfer through mountain basins to be able to predict sediment discharge under a changing climate. We developed a probabilistic sediment cascade model, SedCas, to simulate sediment transfer in a mountain basin (Illgraben, Switzerland) where sediment is produced by hillslope landslides and exported out of the basin by debris flows and floods. We present the model setup, the calibration of the model for the period 2000 - 2009 and the application of SedCas to model sediment discharge in the Illgraben over the 19th and 20th centuries. SedCas conceptualizes the fluvial system as a spatially lumped cascade of connected reservoirs representing hillslope and channel storages where sediment goes through multiple cycles of storage and remobilization by surface runoff. Sediment input is drawn from a probability distribution of slope failures produced for the basin from a time series of DEMs and the model is driven by observed climate. The model includes all relevant hydrological processes that lead to runoff in an Alpine basin, such as snow cover accumulation, snowmelt, evapotranspiration, and soil water storage. Although the processes of sediment transfer and debris flow generation are described in a simplified manner, SedCas produces highly complex sediment discharge behavior which is driven by the availability of sediment and antecedent moisture (system memory) as well as triggering potential (climate). The model reproduces the first order properties of observed debris flows over the period 2000-2009 including their probability distribution, seasonal timing and probability of

  7. Sediment availability on burned hillslopes

    Science.gov (United States)

    Nyman, Petter; Sheridan, Gary J.; Moody, John A.; Smith, Hugh G.; Noske, Philip J.; Lane, Patrick N. J.

    2013-12-01

    describes the inherent resistance of soil to erosion. Hillslope erosion models typically consider erodibility to be constant with depth. This may not be the case after wildfire because erodibility is partly determined by the availability of noncohesive soil and ash at the surface. This study quantifies erodibility of burned soils using methods that explicitly capture variations in soil properties with depth. Flume experiments on intact cores from three sites in western United States showed that erodibility of fire-affected soil was highest at the soil surface and declined exponentially within the top 20 mm of the soil profile, with root density and soil depth accounting for 62% of the variation. Variation in erodibility with depth resulted in transient sediment flux during erosion experiments on bounded field plots. Material that contributed to transient flux was conceptualized as a layer of noncohesive material of variable depth (dnc). This depth was related to shear strength measurements and sampled spatially to obtain the probability distribution of noncohesive material as a function of depth below the surface. After wildfire in southeast Australia, the initial dnc ranged from 7.5 to 9.1 mm, which equated to 97-117 Mg ha-1 of noncohesive material. The depth decreased exponentially with time since wildfire to 0.4 mm (or < 5 Mg ha-1) after 3 years of recovery. The results are organized into a framework for modeling fire effects on erodibility as a function of the production and depletion of the noncohesive layer overlying a cohesive layer.

  8. Shallow sediment transport flow computation using time-varying sediment adaptation length

    Institute of Scientific and Technical Information of China (English)

    Jaan Hui PU; Khalid HUSSAIN; Song-dong SHAO; Yue-fei HUANG

    2014-01-01

    Based on the common approach, the adaptation length in sediment transport is normally estimated astemporally independent. However, this approach might not be theoretically justified as the process of reaching the sediment transport equilibrium stage is affected by the flow conditions in time, especially for fast moving flows, such as scour-hole developing flows. In this study, the two-dimensional (2D) shallow water formulation together with a sediment continuity-concentration (SCC) model were applied to flow with mobile sediment boundary. A time-varying approach was proposed to determine the sediment transport adaptation length to simulate the sediment erosion-deposition rate. The proposed computational model was based on the Finite Volume (FV) method. The Monotone Upwind Scheme of Conservative Laws (MUSCL)-Hancock scheme was used with the Harten Lax van Leer-contact (HLLC) approximate Riemann solver to discretize the FV model. In the flow applications of this paper, a highly discontinuous dam-break, fast sediment transport flow was used to calibrate the proposed time-varying sediment adaptation length model. Then the calibrated model was further applied to two separate experimental sediment transport flow applications documented in the literature, i.e. a highly concentrated sediment transport flow in a wide alluvial channel and a sediment aggradation flow. Good agreement with the experimental data were obtained with the proposed model simulations. The tests prove that the proposed model, which was calibrated by the discontinuous dam-break bed scouring flow, also performed well to represent rapid bed change and steady sediment mobility conditions.

  9. Delaware River and Upper Bay Sediment Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The area of coverage consists of 192 square miles of benthic habitat mapped from 2005 to 2007 in the Delaware River and Upper Delaware Bay. The bottom sediment map...

  10. Deck41 Surficial Seafloor Sediment Description Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Deck41 is a digital summary of surficial sediment composition for 36,401 seafloor samples worldwide. Data include collecting source, ship, cruise, sample id,...

  11. Landfill liners from dam reservoir sediments

    Directory of Open Access Journals (Sweden)

    Koś Karolina

    2016-03-01

    Full Text Available Landfill liners from dam reservoir sediments. Every municipal solid waste landfill has to be properly secured to protect the natural environment from possible leachate. Most often an artificial sealing is used, which is based on a soil liner from cohesive soils (clays, silts. Usability evaluation of bottom sediments from Rzeszowski Reservoir for building these liners was presented in the paper. Sediments from dam reservoirs, gathered as a result of the siltation process, can be a valuable material for earthworks purposes. Determination of their possible ways of usage is important, especially before the planned dredging, because thanks to that this material will not be put on a heap. Based on the analysis of the geotechnical parameters of these sediments it was stated that this material can be preliminary allowed for using in liners.

  12. Microplastic pollution in deep-sea sediments.

    Science.gov (United States)

    Van Cauwenberghe, Lisbeth; Vanreusel, Ann; Mees, Jan; Janssen, Colin R

    2013-11-01

    Microplastics are small plastic particles (microplastics have been accumulating in the marine environment for decades and have been detected throughout the water column and in sublittoral and beach sediments worldwide. However, up to now, it has never been established whether microplastic presence in sediments is limited to accumulation hot spots such as the continental shelf, or whether they are also present in deep-sea sediments. Here we show, for the first time ever, that microplastics have indeed reached the most remote of marine environments: the deep sea. We found plastic particles sized in the micrometre range in deep-sea sediments collected at four locations representing different deep-sea habitats ranging in depth from 1100 to 5000 m. Our results demonstrate that microplastic pollution has spread throughout the world's seas and oceans, into the remote and largely unknown deep sea.

  13. Scripps Sediment Description File- OCSEAP Portion

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Scripps Institution of Oceanography compiled descriptions of sediment samples in the Alaskan Outer Continental Shelf area, funded through the NOAA Outer...

  14. The NGDC Seafloor Sediment Geotechnical Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NGDC Seafloor Sediment Geotechnical Properties Database contains test engineering properties data coded by students at NGDC from primarily U.S. Naval...

  15. Sediment transport in ice-covered channels

    Institute of Scientific and Technical Information of China (English)

    Ian KNACK; Hung-tao SHEN

    2015-01-01

    The existence of ice cover has important effects on sediment transport and channel morphology for rivers in areas with an annual occurrence of an ice season. The interaction of sediment transport and surface ice is poorly understood. In this paper, data from existing flume experiments, each with a limited range of flow and sediment transport conditions, are analyzed. The analysis showed that the bed load transport in ice-covered channels can be described by conventional relationships for the equivalent free-surface flow if the flow strength is expressed in terms of the bed shear stress. A modified Rouse formulation considering the effect of the ice cover on velocity and turbulent diffusion is shown to be applicable for calculating the suspended sediment transport discharge.

  16. Flux saturation length of sediment transport.

    Science.gov (United States)

    Pähtz, Thomas; Kok, Jasper F; Parteli, Eric J R; Herrmann, Hans J

    2013-11-22

    Sediment transport along the surface drives geophysical phenomena as diverse as wind erosion and dune formation. The main length scale controlling the dynamics of sediment erosion and deposition is the saturation length Ls, which characterizes the flux response to a change in transport conditions. Here we derive, for the first time, an expression predicting Ls as a function of the average sediment velocity under different physical environments. Our expression accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which can be estimated directly from independent experiments. We show that our expression is consistent with measurements of Ls in both aeolian and subaqueous transport regimes over at least 5 orders of magnitude in the ratio of fluid and particle density, including on Mars.

  17. Sediment generation and provenance: processes and pathways

    Science.gov (United States)

    Caracciolo, L.; Garzanti, E.; von Eynatten, H.; Weltje, G. J.

    2016-05-01

    The ability to trace sediments from their sources to sedimentary basins is a prerequisite for quantitative analysis of Earth-surface dynamics. The comparatively recent revival of sedimentary provenance analysis goes hand-in-hand with the ever expanding range of analytical tools available for quantifying sediment properties (isotopic, mineral, chemical, and petrographic composition, grain-size and shape distributions, age spectra, etc.), and for interpreting such data in paleo-geographic, -tectonic and -climatic terms. The breakdown of sediment budgets into source-specific contributions - one of the most important tasks of provenance analysis - permits quantification of rates of surface processes in the geological past ("deep time"), even in cases where the source areas themselves have been destroyed by global tectonics. Quantitative sedimentary provenance analysis is therefore crucial to the reconstruction of ancient sediment-routing systems, the fundamental units of mass transfer at the Earth's surface.

  18. Effects of intensive mariculture on sediment biochemistry

    DEFF Research Database (Denmark)

    Pusceddu, Antonio; Fraschetti, Simonetta; Mirto, Simone

    2007-01-01

    The exponential growth of off-shore mariculture that has occurred worldwide over the last 10 years has raised concern about the impact of the waste produced by this industry on the ecological integrity of the sea bottom. Investigations into this potential source of impact on the biochemistry...... of the sea floor have provided contrasting results, and no compelling explanations for these discrepancies have been provided to date. To quantify the impact of fish-farm activities on the biochemistry of sediments, we have investigated the quantity and biochemical composition of sediment organic matter...... regions, with the exception of seagrass sediments in Spain, the biochemistry of the sediments showed significant differences between the control and fish-farm locations. However, the variables explaining the differences observed varied among the regions and between habitats, suggesting idiosyncratic...

  19. Pattern recognition of laminated sediments methodology

    Science.gov (United States)

    Barba-Rojo, Perla Karina; Solorza-Calderón, Selene; González-Fernández, Antonio

    2016-12-01

    This work presents a different aproach for laminae counting and thickness measurements on laminated sediment images. This is done by the use of morphological operations and minimum variance quantization.

  20. BENTHIC COMMUNITY RESPONSE TO SEDIMENT AMENDMENTS

    Science.gov (United States)

    The amendments apatite, organoclay, acetate, chitin, and geotextile reactive mats containing apatite and apatite + organoclay are currently under examination for remediation of contaminated sediments. The objective of this research is to evaluate toxicity to several estuarine an...