Paleoceanography of the Bering Sea Across the Mid-to Late Pleistocene PDF Download

Author: Henrieka Detlef
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: David Moody Hopkins
Publisher: Stanford University Press
ISBN: 9780804702720
Category : Science
Languages : en
Pages : 524

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Data of geology, oceanography, paleontology, plant geography, and anthropology focus on problems and lessons of Beringia. Includes papers presented at Symposium held at VII Congress of International Association for Quaternary Research, Boulder, Colorado, 1965.

Author: Kozo Takhashi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Farzaneh Haj Soltan
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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The latest Pliocene-earliest Pleistocene (2.828 Ma to 2.401 Ma) interval from Integrated Ocean Drilling Program Site U1341, Bowers Ridge, southern Bering Sea, northern North Pacific has been analyzed for dinoflagellate cysts, acritarchs and other palynomorphs. Based on 86 samples, with a spacing equivalent to between 500 and 6000 years, this is the most stratigraphically detailed late Cenozoic marine palynological study yet undertaken in the Bering Sea. The dinoflagellate cyst assemblages are characterized by low taxonomic richness: round brown cysts including Brigantedinium simplex, Lejeunecysta cinctoria, L. fallax, Selenopemphix nephroides, and Trinovantedinium variabile (heterotrophic taxa), and Nematosphaeropsis labyrinthus, Impagidinium cf. japonicum, and Impagidinum spp. indet. (phototrophic taxa). Marine acritarchs are represented by Cymatiosphaera? icenorum and abundant C.? invaginata. Two informal assemblage biozones and their subzones are proposed: biozone MP-A (~2.828 Ma to 2.497 Ma) and biozone MP-B (~2.477-2.401 Ma). The co-dominance of round brown cysts and the extinct high-latitude acritarch Cymatiosphaera? invaginata in biozone MP-A reflects predominantly cold and reduced-salinity surface waters with intermittent incursions of warm and higher salinity waters from the Alaskan Stream. Neither the intensification of northern hemisphere glaciation at 2.7 Ma nor intense glaciation at 2.6 Ma are clearly represented within biozone MP-A, reflecting the enclosed nature of the Bering Sea and low taxonomic richness of the marine palynomorph record. However, the MP-A/ MP-B biozone boundary at 2.47 Ma marks a major change in the hydrography of the Bering Sea, as expressed by an abrupt decline in Cymatiosphaera? invaginata and increased percentages of fresh-water algae and terrestrial plant matter, all suggesting an important increase in the influence of river discharge at Site U1341. The reduced salinity might have largely excluded Cymatiosphaera? invaginata. Biological productivity during the summer months was nonetheless sustained or even elevated judging from the relatively high concentrations of round brown cysts and invertebrate fragments throughout biozone MP-B. Sporadic incursions of the Alaska Stream continued during this time. The overall conclusions of the present study compare favourably with published interpretations based on diatoms, although the major hydrographic change at 2.47 Ma has not yet been detected in other studies of the Bering Sea.

Author: Kozo Takahashi
Publisher:
ISBN:
Category : Paleoceanography
Languages : en
Pages : 312

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Author: Miriam Jones
Publisher: Frontiers Media SA
ISBN: 2889633373
Category :
Languages : en
Pages : 208

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The vast area of the North Pacific, spanning ~55˚ longitude, represents a challenge for documenting and understanding the geologic history of ocean, atmosphere, and terrestrial environmental change. Nevertheless, its importance for many issues, including our fundamental understanding of ocean and atmospheric circulation patterns and teleconnections with natural modes of climate variability through time, has led to a steady rise in the numbers of study sites and proxy types. By bringing together a wide range of proxies and timescales that examine the impacts of paleoclimate on ecosystems, water, carbon, and humans, and interactions between marine and terrestrial processes, this Research Topic contributes to an improved understanding of the region’s significance at global, hemispheric, and regional scales.

Author: Geological Society of London
Publisher: Geological Society of London
ISBN: 9781862391819
Category : Science
Languages : en
Pages : 342

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The Early-Middle Pleistocene transition (around 1.2 to 0.5 Ma) marks a profound shift in Earth's climate state. Low-amplitude 41 ka climate cycles, dominating the earlier part of the Pleistocene, gave way progressively to a 100 ka rhythm of increased amplitude that characterizes our present glacial-interglacial world. This volume assesses the biotic and physical response to this transition both on land and in the oceans: indeed it examines the very nature of Quaternary climate change. Milankovitch theory, palaeoceanography using isotopes and microfossils, marine organic geochemistry, tephrochronology, the record of loess and soil deposition, terrestrial vegetational change, and the migration and evolution of hominins as well as other large and small mammals, are all considered. These themes combine to explore the very origins of our present biota.

Author: Randall Steven Marquard
Publisher:
ISBN:
Category : Paleoclimatology
Languages : en
Pages : 234

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Author: Thomas R. Loughlin
Publisher:
ISBN:
Category : Bering Sea
Languages : en
Pages : 848

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Dynamics of the Bering Sea is a valuable resource for scientists, students, and managers working in the Bering Sea and similar ecosystems worldwide. The international scientific organization PICES has successfully brought together the findings of scientists, of many disciplines and countries, to provide a perspective on physical, chemical, and biological research on the Bering Sea, one of the world's most productive ecosystems.

Author: Mea Young Sohn Cook
Publisher:
ISBN:
Category : Marine sediments
Languages : en
Pages : 126

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In this thesis, I present high-resolution stable-isotope and planktonic-fauna records from Bering Sea sediment cores, spanning the time period from 50,000 years ago to the present. During Marine Isotope Stage 3 (MIS3) at 30-20 ky BP (kiloyears before present) in a core from 1467m water depth near Umnak Plateau, there were episodic occurrences of diagenetic carbonate minerals with very low 13C ( -22.4%), high 18O (6.5%), and high [Mg]/[Ca], which seem associated with sulfate reduction of organic matter and possibly anaerobic oxidation of methane. The episodes lasted less than 1000 years and were spaced about 1000 years apart. During MIS3 at 55-20 ky BP in a core from 2209m water depth on Bowers Ridge, N. pachyderma (s.) and Uvigerina 18O and 13C show no coherent variability on millennial time scales. Bering Sea sediments are dysoxic or laminated during the deglaciation. A high sedimentationrate core (200 cm/ky) from 1132m on the Bering Slope is laminated during the Blling warm phase, Allerd warm phase, and early Holocene, where the ages of lithological transitions agree with the ages of those climate events in Greenland (GISP2) to well within the uncertainty of the age models. The subsurface distribution of radiocarbon was estimated from a compilation of published and unpublished North Pacic benthic-planktonic 14C measurements (475{2700 m water depth). There was no consistent change in 14C probles between the present and the Last Glacial Maximum, Blling-Allerd, or the Younger Dryas cold phase. N. pachyderma (s.) 18O in the Bering Slope core decreases rapidly (in less than 220 y) by 0.7-0.8h at the onset of the Blling and the end of the Younger Dryas. These isotopic shifts are accompanied by transient decreases in the relative abundance of N. pachyderma (s.), suggesting that the isotopic events are transient warnings and sustained freshenings.