Energy Technology Data Exchange (ETDEWEB)

A conceptual hydrodynamic model in the Holocene and upper Pleistocene beneath the Louisiana wetlands is described in terms of safety distributions. Porewater safety is calculated from electrical measurements, including resistivity soundings, electric logs, and electromagnetic profiling. Electrical measurements support the primary, basin-wide groundwater flow model; however, the data also indicate secondary contributions from expulsion of fluids under geopressure along active growth faults and from original waters of deposition. Expulsion of water from growth faults has been described previously for deeper sections of the Pleistocene, but has not been reported for the Holocene or upper Pleistocene beneath the Louisiana wetlands. Porewater chemistry variations beneath the coastal wetlands are a consequence of the following (in order of importance): (1) environment of deposition; (2) a basin-wide, regional flow system; (3) expulsion from ...

British Library Electronic Table of Contents (United Kingdom)

Here we present a revision of the fossil record of chitons (Mollusca, Polyplacophora) of Late Pleistocene and Holocene marine deposits of Uruguay and discuss their potential for palaeoenvironmental reconstruction. Chitons were recorded as isolated valves in bivalve- and gastropod-rich assemblages. They are represented by the species Chaetopleura angulata (Spengler), C. isabellei (d'Orbigny), C. asperrima (Gould) and Ischnochiton striolatus (Gray). The last two species are recorded for the first time as fossils not only in Uruguay but also in South America. Exclusively recorded for the Late Pleistocene is the warm water species I. striolatus, whose current southern range limit is located in Santa Catarina, Brazil. Higher temperatures than at present are inferred for the Uruguayan coast duri...

Energy Technology Data Exchange (ETDEWEB)

The Upper Jurassic Hith Anhydrite is a major hydrocarbon seal in the Arabian Gulf region. Outcrops, core samples from the subsurface, and the literature indicate that the Hith Formation is composed mainly of anhydrite. In most locations where a section of the Hith Formation has been measured, this unit contains less than 20% carbonate much of which is in the form of thin laminations. This lack of carbonate, locally thick layers of salt, and the predominance of anhydrite favor a playa for the setting in which this sediment was accumulated. In fact, much of the Hith has the sedimentary characteristics of the Holocene Lake MacLeod playa of Western Australia, which is dominated by layers of gypsum and halite (what little carbonate that occurs is found in layers at the base of the section). Locally the Hith appears to have accumulated in a sabkha setting, particularly toward central Abu Dhabi where it pinches out into shallow-water, and peritidal carbonate. This sabkha ...

Science.gov (United States)

The lower continental slope of the northwestern Gulf of Mexico is characterized by a hummocky topography with shallow salt masses interspersed by numerous salt-withdrawal basins containing thick Plio-Pleistocene and older sediments. Analysis of over 7500 km of multichannel seismic reflection data from the Keathley Canyon Area and vicinity defined the Wisconsinan-Holocene sequence and its seismic facies. In interbasinal areas and in the southern part of the study area where salt is shallow, the Wisconsinan-Holocene sequence consists mainly of low-amplitude (LA) facies underlain by strong basal-reflection (SBR) facies. The LA facies occasionally show subtle onlaps against SBR facies and grade upward into a draping pattern. Onlapping LA facies are interpreted to be a lowstand systems tract deposited by widespread low-energy turbidity currents. Draping LA facies at the top may consist of hemipelagic or pelagic sediments. The SBR facies are ...

British Library Electronic Table of Contents (United Kingdom)

The North-West Borneo Trough is bordered along its south-east margin by a melange wedge that has been the subject of disagreement with insufficient discussion. Offshore Palawan it has been interpreted as an accretionary prism that has been preserved in place when subduction ceased in the Middle Miocene. It is unconformably overlain by undeformed Upper Miocene to Holocene draping strata. Farther south-west along the Trough, the seismically identical melange wedge has been named a Major Thrust Sheet System, which was assumed to have been thrust as a nappe north-westwards over the autochthonous Dangerous Grounds terrane of attenuated continental crust of the South China Sea passive margin. The accretionary prism model is the simplest, resulting in interpretation of the North-West Borneo Troug...

British Library Electronic Table of Contents (United Kingdom)

Batadomba-lena, a rockshelter in the rainforest of southwestern Sri Lanka, has yielded some of the earliest evidence of Homo sapiens in South Asia. H. sapiens foragers were present at Batadomba-lena from ca. 36,000 cal BP to the terminal Pleistocene and Holocene. Human occupation was sporadic before the global Last Glacial Maximum (LGM). Batadomba-lena's Late Pleistocene inhabitants foraged for a broad spectrum of plant and mainly arboreal animal resources (monkeys, squirrels and abundant rainforest snails), derived from a landscape that retained equatorial rainforest cover through periods of pronounced regional aridity during the LGM. Juxtaposed hearths, palaeofloors with habitation debris, postholes, excavated pits, and animal and plant remains, including abundant Canarium nutshells, ref...

British Library Electronic Table of Contents (United Kingdom)

The erosion of rocks rich in organic matter typically leads to the complete mineralization of the organic material. However, in some cases, it is re-deposited to become a part of sediments once more. This process should be considered to be a part of global carbon cycle, possibly much more significant than assumed to-date. The research presented here aims to characterize re-worked organic matter occurring in post-glacial sediments of southern part of Poland, in the Oder river valley (the Racib?rz town region, Miocene, Pleistocene and Holocene age). Organic substances extracted from the sediments originated from organic matter that had resided in rocks eroded by glaciers. Sediments were sampled in two boreholes which sediments were correlated. Sediments were extracted and extracts analyzed w...

British Library Electronic Table of Contents (United Kingdom)

Villarrica (Chile) is one of the most active volcanoes in South America having erupted about 60 times in the last 460years. Although its historical eruptive activity has been mainly effusive and weakly explosive, it had strong explosive behaviour in postglacial times. Chaimilla (<3.1ka) is one of the best exposed and widely dispersed pyroclastic deposits, related to both fall and flow activity. The deposit is dispersed over an area of 250km^2 and consists of 8 units (A-H) which were grouped into four sequences. Stratigraphic data suggest that the eruption had a relatively short duration and evolved from i) an Opening phase, dispersing ash, lapilli clasts, accretionary lapilli, blocks and bombs, to ii) a Pulsatory phase, originating a series of magmatic explosions, to iii) a Collapsing phas...

Science.gov (United States)

The Eagle Flat basin, an intermontane basin in Trans-Pecos Texas, is being considered as a possible site for the Texas repository of low-level radioactive wastes. Intermontane basins and associated normal faults formed in response to Basin and Range tectonism that began about 24 Ma ago. The most active late Tertiary and Quaternary faults occur within the Hueco Bolson (HB) and the Salt Basin/Salt Flat/Lobo Valley, west and east, respectively, of the proposed repository. Several faults of the southeast HB which are within 50 km of the site, displace middle Pleistocene deposits 10 to 24 m. The most recent surface rupture in the southeast HB probably occurred on the Amargosa fault during the Holocene. Upper Pleistocene deposits are offset 2.5 to 4.5 m, and middle Pleistocene deposits are displaced 24 m. Fault scarps within 50 km east of the proposed repository are associated with faults bounding the Salt Basin/Salt Flat/Lobo Valley. In the southern Salt Basin and ...

Energy Technology Data Exchange (ETDEWEB)

A petrographic comparison of Triassic, fluvial sandstones from the Deep River Basin in the eastern piedmont of North Carolina with nearby Holocene stream sands (1) indicates that he Triassic climate was more arid than today's and (2) distinguishes an eastern, more plutonic terrane from a western, more metamorphic source terrane. The paleoclimatic interpretation is based on differences in framework composition between modern and ancient sands of the same grain size, derived from the same rock type, transported similar distances and deposited in similar settings. The Triassic sandstones contain more lithic-fragments but less quartz than otherwise equivalent, modern sand in the Deep River Basin. Feldspar content is more complex, controlled by both source-rock composition and climate. Sand from the more plutonic terrane contains more feldspar and plutonic lithic-fragments than sand from the more metamorphic terrane, which contains more quartz and metamorphic ...

DEFF Research Database (Denmark)

Owing to exceptional biomolecule preservation, fossil avian eggshell has been used extensively in geochronology and palaeodietary studies. Here, we show, to our knowledge, for the first time that fossil eggshell is a previously unrecognized source of ancient DNA (aDNA). We describe the successful isolation and amplification of DNA from fossil eggshell up to 19 ka old. aDNA was successfully characterized from eggshell obtained from New Zealand (extinct moa and ducks), Madagascar (extinct elephant birds) and Australia (emu and owl). Our data demonstrate excellent preservation of the nucleic acids, evidenced by retrieval of both mitochondrial and nuclear DNA from many of the samples. Using confocal microscopy and quantitative PCR, this study critically evaluates approaches to maximize DNA recovery from powdered eggshell. Our quantitative PCR experiments also demonstrate that moa eggshell has approximately 125 times lower bacterial load than bone, making it a highly suitable substrate for ...

Energy Technology Data Exchange (ETDEWEB)

Southeastern Finland belongs to the area covered by the Weichselian ice sheet, where the release of the ice load caused a rapid isostatic rebound during the postglacial time. While the mean overall apparent uplift is of the order of 2 mm/yr today, in the early Holocene time it was several times higher. A marked decrease in the rebound rate occurred around 8500 BP, however, since then the uplift rate has remained high until today, with a slightly decreasing trend towards the present time. According to current understanding there have neither been temporary increases nor decreases in the rate of uplift during the postglacial time. Even so, it is not known for sure whether there are regional irregularities on the rebound in Finland. Concurrently with land uplift, relative sea-level changes in the Baltic basin were also strongly affected by the global eustatic rise of sea-level. During the early Litorina Sea stage on the southern coast of Finland around 7000 BP, the ...

Energy Technology Data Exchange (ETDEWEB)

Finland has some 10 million hectares of peatland, accounting for almost a third of its total area. Macroclimatic conditions have varied in the course of the Holocene growth and development of this peatland, and with them the habitats of the peat-forming plants. Temperatures and moisture conditions have played a significant role in determining the dominant species of mire plants growing there at any particular time, the resulting mire types and the accumulation and deposition of plant remains to form the peat. While in a natural state the mires of Finland have functioned as carbon dioxide sinks throughout the post-glacial period, but the ditching of peatland for forestry and agriculture, amounting to some 5,7 million hectares in Finland, has affected their water balance, especially over the last hundred years, and has thereby altered the quantity and species composition of the mire vegetation. The invasion of trees and woody plants to replace the typical mire plants ...