Download or read book Insights Into West Antarctica s Geology and Late Pleistocene Ice Sheet Behaviour from Isotopic Sedimentary Provenance Studies written by Patric Simoes Pereira and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Antarctica s Geologic and Ice Sheet History from Isotopic Sedimentary Provenance Studies written by Elizabeth Lane Pierce and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Within the constraints of uncertainty in the nature of erosion and transport in the sub-glacial environment, the study of glacialy-derived material from marine sediments located off the margin of East Antarctica provides a means for characterizing the sub-glacial geology obscured by the more than 98% ice cover of the continent. These insights into the geology of East Antarctica in turn provide characterization of sedimentary source areas, the knowledge of which can be applied to sediment provenance studies of ice rafted detritus (IRD) and thus about East Antarctic ice sheet history. Much of what has been learned of East Antarctica's Cenozoic ice sheet evolution has been achieved through the study of marine sediments, as ice sheets tend to erode their own history and much of what is preserved is, like the geology, obscured the ice sheet. Determining the provenance of ice-rafted detritus allows for spatial and temporal reconstructions of ice sheet behavior. Accordingly sedimentary provenance studies are key to documenting how Antarctica's ice sheet evolved through the Cenozoic.
Download or read book Inferring West Antarctic Subglacial Basin History and Ice Stream Processes Using Siliceous Microfossils written by Jason James Coenen and published by . This book was released on 2016 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: In January of 2013 and 2015 the WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) science team collected sediment cores from Subglacial Lake Whillans (SLW), and the Whillans Grounding Zone (WGZ) which are both part of the Whillans Ice Stream (WIS) in West Antarctica. These sediment cores along with sediment samples from the California Institute of Technology (Caltech) Glaciology group, which include sediments from Kamb Ice Stream (KIS) and Bindschadler Ice Stream (BIS) are compared with published micropaleontological data from the WIS Upstream B camp (UpB), the Crary Ice Rise (CIR) and the Ross Ice Shelf Project (RISP), using observations on preservation of microfossils in these deposits. Diatoms and other microfossils provide biostratigraphic and paleoenvironmental constraints on past marine deposition in West Antarctica interior basins, as well as inferences regarding ice stream erosion, particulate provenance and glacial mixing. Most subglacial samples contain a mixture of eroded diatoms that reflect initial deposition throughout the Cenozoic. Pleistocene diatoms are widespread but never abundant, reflecting erosion of marine sediments deposited in the West Antarctic marine basin during Quaternary ice sheet retreat events. Geologic drilling near Ross Island (the ANDRILL McMurdo Ice Shelf Project) provided abundant evidence for Pliocene and early Pleistocene retreat of the West Antarctic Ice Sheet, yet Pliocene diatoms are rare in sediments recovered from beneath grounded ice, which suggests erosion of Pliocene deposits in the Ross Embayment. Miocene age diatoms are dominant in subglacial and sub-ice shelf deposits, reflecting extensive Miocene deposition in the basin prior to entering a dominantly glacial phase. Additionally, Paleogene fossils, both marine and non-marine, occur widely, reflecting deeper erosion and providing insights into earlier basin history. SLW contains Upper Miocene fossils with a mix of younger and older taxa. These ages and taxa are consistent with previously published results from samples recovered ~200 km upstream from the UpB sites, suggesting a connection between the sites with little evidence of new subglacial erosion of material. Diatom abundance is on average lower than UpB in samples, suggesting sediments at SLW have experienced additional cumulative shearing and transport. WGZ cores exhibit stratigraphic variation in microfossil abundance as well as a transition in age dominance of taxa. Four lithostratigraphic units were observed in grounding zone cores, but a fifth unit is recognized based on microfossil data. Unit I is thought to be rain out from the base of the debris rich ice, which has a dominant Upper Miocene assemblage. Unit II is described as subglacial and is dominated by long ranging taxa, with a mix of younger material. Unit III is thought to be sub-ice shelf, which is consistent with diatomite microclasts (silt-sized aggregates) and a radiolarian that has a Late Pleistocene diatom assemblage. Unit IV is described as subglacial, based on the lithostratigraphy, however, microfossils are well-preserved, allowing definition of subunits, Unit IV-B and Unit IV-A. The stratigraphic variability at the grounding zone indicates changes in sediment provenance, indicating a variable glaciological regime, which suggesting a dynamic grounding line. Higher overall diatom abundance at WGZ indicates less cumulative glacial shear strain within the sediments than in SLW and UpB tills. KIS is one of the ice streams on the Siple Coast that has been shut down for the last 150 years. Most KIS sediments contain Upper Miocene fossils that are relatively unmixed and well-preserved, containing an order to two orders of magnitude higher diatom abundance than for all WIS samples. An exception is one sample from the KIS sticky spot (SS) that has low abundance and poor preservation indicating high cumulative shear strain. The unmixed Upper Miocene assemblage and preservation of the rest of these samples suggests close proximity to Miocene source rocks at this site. BIS is the northern-most active ice stream from this study in the Siple Coast area. These deposits contain no microfossils younger than Oligocene, suggesting tectonic processes, subglacial processes or change in source for this area. The age transition is also observed in other microfossil groups, which likely indicates a different source of sediments for BIS. Paleogene microfossils at this site are well preserved and relatively abundant. Biostratigraphic characterization of the Ross Embayment using age-specific diatoms help constrain basin scale productivity events that are linked to warm interglacial periods. Assessing when these events happened and diatom fragmentation patterns from different subglacial environments adds new insights into sediment-ice interactions and modern subglacial processes.
Download or read book The West Antarctic Ice Sheet written by Richard B. Alley and published by . This book was released on 2001 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Antarctic Glacial History and World Palaeoenvironments written by E.M. Zinderen van Bakker and published by CRC Press. This book was released on 2020-08-26 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, based on the proceedings of third symposium held on 17th August 1977 during the Xth INQUA Congress at Birmingham, UK, focuses on the influence the Antarctic glaciation had on world palaeoenvironments.
Download or read book Exploration of Subsurface Antarctica written by M.J. Siegert and published by Geological Society of London. This book was released on 2018-01-08 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our appreciation of glaciological processes in Antarctica suffers from a lack of observations in regions where numerical models indicate the ice sheet to be susceptible to ocean and/or atmospheric warming. The solution lies in the use and development of glacier geophysics. In this volume we present a series of papers that demonstrate how geophysics can be deployed in Antarctica to comprehend: (1) boundary conditions that influence ice flow such as subglacial topography, the distribution of basal water and ice-sheet rheology; (2) phenomena that might affect ice-flow processes, such as complex internal ice-sheet structures and the proposition of large stores of hitherto unappreciated groundwater; and (3) how glacigenic sediments and formerly glaciated terrain on, and surrounding, the continent can inform us about past ice-sheet dynamics. The volume also takes a historical view on developments leading to current knowledge, examines active ice-sheet processes, and points the way forward on how geophysics can advance quantitative understanding of Antarctic ice-sheet behaviour.
Download or read book Insights Into the Behaviour of the Pliocene East Antarctic Ice Sheet from Provenance Studies of Marine Sediments Using Radiogenic Isotopoes written by Carys Patricia Cook and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Letter written by Timothy Naish and published by . This book was released on 2009 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch (~5-3Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming. Here we present a marine glacial record from the upper 600m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, ~40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to ~3°C warmer than today and atmospheric CO2 concentration was as high as ~400p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model that simulates fluctuations in Antarctic ice volume of up to +7m in equivalent sea level associated with the loss of the WAIS and up to +3m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt under conditions of elevated CO2.
Download or read book Antarctic Climate Evolution written by Fabio Florindo and published by Elsevier. This book was released on 2008-10-10 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: Antarctic Climate Evolution is the first book dedicated to furthering knowledge on the evolution of the world's largest ice sheet over its ~34 million year history. This volume provides the latest information on subjects ranging from terrestrial and marine geology to sedimentology and glacier geophysics. - An overview of Antarctic climate change, analyzing historical, present-day and future developments - Contributions from leading experts and scholars from around the world - Informs and updates climate change scientists and experts in related areas of study
Download or read book Geology and Seismic Stratigraphy of the Antarctic Margin written by Alan K. Cooper and published by Wiley-AGU. This book was released on 1997-01-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Antarctic Ice Sheet has greatly affected global climate, sea level, ocean circulation, and southern hemisphere biota during Cenozoic times. Much of our understanding of the evolution of the ice sheet has been inferred from isotopic studies on distant deep-ocean sediments, because few Cenozoic rocks are exposed on the Antarctic continent. Yet, large differences occur between past ice volumes inferred from isotopic studies and those inferred from low-latitude sea-level variation. The massive quantities of glacially transported terrigenous sediments that lie beneath the Antarctic continental margin provide an additional, more direct record of the inferred ice sheet fluctuations. Volume 68 addresses the history of ice sheet fluctuations as recorded by geological and geophysical investigations of selected areas of the Antarctic continental margin. As described below, the volume gives data and results from on-going research by a major multinational project directed toward better understanding the impact of Antarctic Ice Sheet fluctuations on global sea levels and climates.
Download or read book Geology and Seismic Stratigraphy of the Antarctic Margin written by Alan K. Cooper and published by American Geophysical Union. This book was released on 1997-01-23 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Antarctic Research Series, Volume 71. The Antarctic Ice Sheet has greatly affected global climate, sea level, ocean circulation, and southern hemisphere biota during Cenozoic times. Much of our understanding of the evolution of the ice sheet has been inferred from isotopic studies on distant deep-ocean sediments, because few Cenozoic rocks are exposed on the Antarctic continent. Yet, large differences occur between past ice volumes inferred from isotopic studies and those inferred from low-latitude sea-level variation. The massive quantities of glacially transported terrigenous sediments that lie beneath the Antarctic continental margin provide an additional, more direct record of the inferred ice sheet fluctuations. Volume 68 addresses the history of ice sheet fluctuations as recorded by geological and geophysical investigations of selected areas of the Antarctic continental margin. As described below, the volume gives data and results from on-going research by a major multinational project directed toward better understanding the impact of Antarctic Ice Sheet fluctuations on global sea levels and climates.
Download or read book Geology and Seismic Stratigraphy of the Antarctic Margin written by Alan K. Cooper and published by American Geophysical Union. This book was released on 1997-01-23 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Antarctic Research Series, Volume 71. The Antarctic Ice Sheet has greatly affected global climate, sea level, ocean circulation, and southern hemisphere biota during Cenozoic times. Much of our understanding of the evolution of the ice sheet has been inferred from isotopic studies on distant deep-ocean sediments, because few Cenozoic rocks are exposed on the Antarctic continent. Yet, large differences occur between past ice volumes inferred from isotopic studies and those inferred from low-latitude sea-level variation. The massive quantities of glacially transported terrigenous sediments that lie beneath the Antarctic continental margin provide an additional, more direct record of the inferred ice sheet fluctuations. Volume 68 addresses the history of ice sheet fluctuations as recorded by geological and geophysical investigations of selected areas of the Antarctic continental margin. As described below, the volume gives data and results from on-going research by a major multinational project directed toward better understanding the impact of Antarctic Ice Sheet fluctuations on global sea levels and climates.
Download or read book Upper Miocene History of the West Antarctic Ice Sheet Inferred from Sequence Stratigraphy Clay Mineralogy and Paleoecology of the Andrill 1B Core written by Ty M. Engler and published by . This book was released on 2018 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Upper Miocene succession (Motif 3, ~758-1073 meters below sea floor) of the ANDRILL 1B core was recovered from below the McMurdo Ice Shelf, in the flexural moat around the volcanic Ross Island, Antarctica. Clay mineral assemblages and microfossils of the succession have the potential to be used as paleoenvironmental and provenance indicators, which when placed in a glacial sequence stratigraphic framework, may be used to help constrain past dynamics of the West Antarctic Ice Sheet (WAIS) under warm paleoclimatic conditions. Smectite and illite clay mineral assemblages dominate Motif 3 and chlorite (+kaolinite) is a minor component. High relative smectite percentages may be directly related to volcanic units of the McMurdo Volcanic Complex, located locally to the drill site. Higher relative percentages of illite, combined with lower smectite proportions, may be sourced from weathered schists, amphibolites and gneisses of the Koettlitz Group, granitoids of the Granite Harbor Intrusives, and other basement rocks along the coast to the south and west of the drill site within the Transantarctic Mountains. That clay assemblage is considered an indicator of transport by the WAIS from the south and that assemblage was then mixed with reworked, locally derived sediment (the volcaniclastic smectite clays). Clays of the mudstones showed little excess Si, which is used to infer that low numbers of diatoms were present during deposition, even in open-water settings. A paucity of diatoms in this interval had been attributed to either loss by diagenesis or a lack of productivity in brackish surface waters rich in suspended muds coming from temperate-polythermal ice. Data presented here indicate the latter option is most likely, and agree with other facies indicators. Diagenesis and authigenesis may also be expressed in the recorded clay signatures. Post-depositional alteration can occur within sedimentary successions and it is often difficult to discriminate between smectites occurring from primary detrital volcanic grains, and those grown in situ either by authigenic growth from hydrothermal fluids, or by alteration during diagenetic reactions within the original parent sedimentary rock. Understanding the sediment provenance established using clay mineralogy in the Upper Miocene may provide a better understanding of ice dynamics by helping constrain the inferred glacial sequences that are used to interpret past WAIS dynamics. This pilot study has shown the way forward, but more detailed sampling and more advanced analytical techniques should be performed in the future to fully develop the concept. These data along with more detailed microfossil analyses should allow for the development of an enhanced and perhaps more reliable sequence stratigraphic model, which could lead to better-constrained interpretations of WAIS dynamics under warmer climatic conditions. Understanding how the ice reacted to past major cooling and warming events will allow for better model predictions for the future.
Download or read book Antarctic Peninsula Climate Variability written by Eugene Domack and published by American Geophysical Union. This book was released on 2003-01-10 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Antarctic Research Series, Volume 79. The Antarctic Peninsula region represents our best natural laboratory to investigate how earth's major climate systems interact and how such systems respond to rapid regional warming. The scale of environmental changes now taking place across the region is large and their pace rapid but the subsystems involved are still small enough to observe and accurately document cause and affect mechanisms. For example, clarification of ice shelf stability via the Larsen Ice Shelf is vital to understanding the entire Antarctic Ice Sheet, its climate evolution, and its response to and control of sea level. By encompassing the broadest range of interdisciplinary studies, this volume provides the global change research and educational communities a framework in which to advance our knowledge of the causes behind regional warming, the dramatic glacial and ecological responses, and the potential uniqueness of the event within the region's paleoclimate record. The volume also serves as a vital resource for public policy and governmental funding agencies as well as a means to educate the large number of ecotourists that visit the region each austral summer.
Download or read book Ice Ages and Interglacials written by Donald Rapp and published by Springer Science & Business Media. This book was released on 2009-08-22 with total page 275 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book studies the history and gives an analysis of extreme climate change on Earth. In order to provide a long-term perspective, the first chapter briefly reviews some of the wild gyrations that occurred in the Earth’s climate hundreds of millions of years ago: snowball Earth and hothouse Earth. Coming closer to modern times, the effects of continental drift, particularly the closing of the Isthmus of Panama are believed to have contributed to the advent of ice ages in the past three million years. This first chapter sets the stage for a discussion of ice ages in the geological recent past (i.e. within the last three million years, with an emphasis on the last few hundred thousand years). The second chapter discusses geological evidence for ice ages – how geologists surmised their existence prior to actual subsurface data that proved the theory. The following two chapters look at ice cores (primarily from Greenland and Antarctica). Chapter 3 discusses how ice core data is processed and Chapter 4 summarizes data obtained from ice cores. Chapter 5 discusses the processing of data obtained from ocean sediments, and summarizes the results, while the following chapter discusses data from other sources, such as "Devil’s Cave." Chapter 7 summarizes the experimental results from Chapters 4, 5, and 6. It provides the foundation for comparison with theories in later chapters. In a perfect world, this data would be totally separate and disconnected from theory. Unfortunately, as the author shows, dating of much of the data was accomplished by "tuning" to the astronomical theory, which introduces circular reasoning. Chapter 8 provides a brief overview of the various theories that have been devised to "explain" the patterns of alternating ice ages and interglacials that have occurred over the past three million years. This serves as an introduction to the following three chapters which presents the astronomical theory in its various manifestations, compare the astronomical theory with data, and then compare other theories with data. Finally, Chapter 12 summarizes what we think we know about ice ages and, more importantly, what we don’t know.
Download or read book Late Pleistocene Holocene retreat of the West Antarctic ice sheet system in the Ross Sea written by E.W. DOMACK and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Late Pleistocene Holocene retreat of the West Antarctic ice sheet system in the Ross Sea written by S. SHIPP and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
