Late Pleistocene–Holocene environmental and climatic history of a freshwater paramo ecosystem in the northern Andes

2020 ◽  
Vol 35 (8) ◽  
pp. 1046-1056
Author(s):  
Luisa Patiño ◽  
Maria Isabel Velez ◽  
Marion Weber ◽  
César A. Velásquez‐r ◽  
Santiago David ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Northern Andes ◽  
History Of ◽  
Climatic History

Paleontology and stratigraphy of Middle Eocene rock units in the southern Green River and Uinta Basins, Wyoming and Utah

2017 ◽  
Vol 4 ◽  
pp. 1-53 ◽  
Author(s):  
Paul Murphey ◽  
K.E. Townsend ◽  
Anthony Friscia ◽  
James Westgate ◽  
Emmett Evanoff ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Middle Eocene ◽  
Green River Basin ◽  
Green River ◽  
Scientific Exploration ◽  
History Of ◽  
Climatic History ◽  
Field Excursion ◽  
Land Mammal ◽  
Bridger Formation

The Bridger Formation is restricted to the Green River Basin in southwest Wyoming, and the Uinta and Duchesne River Formations are located in the Uinta Basin in Utah. These three rock units and their diverse fossil assemblages are of great scientific importance and historic interest to vertebrate paleontologists. Notably, they are also the stratotypes from oldest to youngest for the three middle Eocene North American Land Mammal Ages—the Bridgerian, Uintan, and Duchesnean. The fossils and sediments of these formations provide a critically important record of biotic, environmental, and climatic history spanning approximately 10 million years (49 to 39 Ma). This article provides a detailed field excursion through portions of the Green River and Uinta Basins that focuses on locations of geologic, paleontologic, and historical interest. In support of the field excursion, we also provide a review of current knowledge of these formations with emphasis on lithostratigraphy, biochronology, depositional, and paleoenvironmental history, and the history of scientific exploration.

scholarly journals Ultrastructure, dissolution and "pyritization" of Late Quaternary and Recent echinoderms

1987 ◽  
Vol 36 ◽  
pp. 275-287
Author(s):  
Margit Jensen ◽  
Elsebeth Thomsen
Keyword(s):  
Late Pleistocene ◽  
Sea Water ◽  
Late Quaternary ◽  
Pore Space ◽  
Water Interface ◽  
Sea Stars ◽  
Northern Norway ◽  
History Of ◽  
Organic Tissue ◽  
Diagenetic History

The diagenetic history of the skeletal elements of Late Pleistocene-Holocene Ophiura sarsi from the shelf off northern Norway (Andfjorden, Malangsdjupet) is elucidated by comparison with natural and induced degradation of the skeletal elements of Recent ophiuroids (brittle stars) and asteroids (sea stars) from Danish waters. Dissolution features ("core-and-rind") in the trabeculae of fossil and Recent echinoderm stereom are initiated during death and early decay of organic tissue in the animals. The trabeculae have a polycrystal­line lamellar ultrastructure and lose their older central part during later stages of dissolution, which are dependant on undersaturation of the sea-water with regard to CaC03• The presence of undersaturated sea-water is supported by palaeoecological studies (Thomsen & Vorren 1984, 1986) implying oxygen deficient periods in the Late Pleistocene and an increased biogenic production in the Holocene. Pyrite framboids are situated in the secondary voids within the trabeculae and in the pore space of the stereom of the Late Pleistocene elements. No pyrite is observed within the polycrystalline lamellar ultrastructure of the trabeculae. The Late Pleistocene "pyritization" took place during oxygen deficient periods at the sediment-water interface or within the reduced zone of the topmost sediment.

scholarly journals ĐẶC ĐIỂM HỆ THỐNG SÔNG CỔ VÀ TÁC ĐỘNG NHÂN SINH DỰA TRÊN KẾT QUẢ MÔ HÌNH TIẾN HÓA TỈ LỆ LỚN KHU VỰC CHÂU THỔ SÔNG HỒNG

2020 ◽  
Vol 19 (4) ◽  
pp. 463-478
Author(s):  
Mai Duc Dong ◽  
Phung Van Phach ◽  
Nguyen Trung Thanh ◽  
Duong Quoc Hung ◽  
Pham Quoc Hiep ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
River System ◽  
River Network ◽  
River Delta ◽  
Red River ◽  
River Systems ◽  
Red River Delta ◽  
The World ◽  
History Of

The Simclast model has been verified and applied effectively in simulating the delta development for some major deltas in the world. In this study, we applied the model Simclast for simulating the history of the Red river delta development in late Pleistocene-Holocene. Results of the model reveal that the mainland of study area had reduced rapidly during transgression period (10,000-8,000 BP). The morphology changed significantly in the paleo-Red and Day river systems, but slightly in the paleo Thai Binh river system. The paleo-river network had been active in upper part before 11,000 BP and then shifted seaward until 2,000 BP. The river-sea interaction causes erosion and accumulation; as a result the morphology changed remarkably. The paleo-Thai Binh river had been inactive until 5,500 BP and then it was active but the morphology had not varied remarkably. The recent coastline generated from Simclast is relatively in accordance with the present coastline.

scholarly journals Plio-Quaternary history of the Turkish coastal zone of the Enez-Evros Delta: NE Aegean Sea

2001 ◽  
Vol 2 (2) ◽  
pp. 95 ◽  
Author(s):  
B. ALPAR
Keyword(s):  
Late Pleistocene ◽  
Sand Dunes ◽  
Aegean Sea ◽  
Interglacial Period ◽  
Shelf Area ◽  
Sea Level Changes ◽  
Seismic Profiles ◽  
Alluvial Deposits ◽  
History Of ◽  
Quaternary History

The Enez-Evros Delta, NE Aegean Sea, is located in one the most important wetlands in the world with its sandy offshore islands, abandoned channel mouths, sand-dunes, shoals, marshlands, saline lagoons and saltpans. It comprises very well developed sedimentary units and a prodelta lying on an older submarine delta. The present day elevations of the middle-late Pleistocene marine terraces indicate a regional tectonic uplift in the area. Due to lack of geophysical and bore hole data and partly due to its strategic position, the structural and stratigraphic features of the submarine extension of the delta are not known in detail. In this paper, Plio-Quaternary history of this delta and its submarine part on the Turkish shelf was explored by using high-resolution shallow reflection seismic profiles. The delta is formed by the alluvial deposits of the Enez-Evros River and shaped by their interaction with the sea. It takes place in front of a large and protected ancient bay which was filled rapidly over millennia. The sediments in the plateau off the river are principally pro-deltaic with muddy areas near the river mouths changing to muddy sand further out. The sea-level changes in Plio-Quaternary were characterised by three different seismic stratigraphic units on the folded Miocene limestone basement. In the late Pleistocene, the shelf area over an Upper Miocene basement was flooded during the Riss-Würm interglacial period, exposed in the Würm glacial stage, and flooded once again during the Holocene transgression.

scholarly journals Atmospheric speciation of rocky planets from magma ocean outgassing

2020 ◽  
Author(s):  
Tim Lichtenberg ◽  
Dan J. Bower ◽  
Mark Hammond ◽  
Ryan Boukrouche ◽  
Shang-Min Tsai ◽  
...  
Keyword(s):  
Coupled Model ◽  
Initial Distribution ◽  
Occurrence Rate ◽  
Magma Ocean ◽  
Mantle Dynamics ◽  
Mantle Geochemistry ◽  
Prebiotic Chemical ◽  
History Of ◽  
Climatic History ◽  
Rocky Planets

<p>The earliest atmospheres of rocky planets originate from extensive volatile release during one or more magma ocean epochs that occur during primary and late-stage assembly of the planet (1). These epochs represent the most extreme cycling of volatiles between the interior and atmosphere in the history of a planet, and establish the initial distribution of the major volatile elements (C, H, N, O, S) between different chemical reservoirs that subsequently evolve via geological cycles. Crucially, the erosion or recycling of primary atmospheres bear upon the nature of the long-lived secondary atmospheres that will be probed with current and future observing facilities (2). Furthermore, the chemical speciation of the atmosphere arising from magma ocean processes can potentially be probed with present-day observations of tidally-locked rocky super-Earths (3). The speciation in turn strongly influences the climatic history of rocky planets, for instance the occurrence rate of planets that are locked in long-term runaway greenhouse states (4). We will present an integrated framework to model the build-up of the earliest atmospheres from magma ocean outgassing using a coupled model of mantle dynamics and atmospheric evolution. We consider the diversity of atmospheres that can arise for a range of initial planetary bulk compositions, and show how even small variations in volatile abundances can result in dramatically different atmospheric compositions and affect earliest mantle geochemistry and atmospheric speciation relevant for surficial prebiotic chemical environments (5). Only through the lense of coupled evolutionary models of terrestrial interiors and atmospheres can we begin to deconvolve the imprint of formation from that of evolution, with consequences for how we interpret the diversity revealed by astrophysical observables, and their relation to the earliest planetary conditions of our home world.</p> <div class=""><em>References</em></div> <ol> <li>Bower, D. J., Kitzmann, D., Wolf, A. S., et al. (2019). Astron. Astrophys. 631, A103.</li> <li>Bonati, I., Lichtenberg, T., Bower, D. J., et al. (2019). Astron. Astrophys. 621, A125.</li> <li>Kreidberg, L., Koll, D. D., Morley, C., et al. (2019). Nature 573, 87-90.</li> <li>Hamano, K., Abe, Y., Genda, H. (2013). Nature 497, 607-610.</li> <li>Sasselov, D. D., Grotzinger, J. P., Sutherland, J. D. (2020). Sci. Adv. 6, eaax3419.</li> </ol>

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