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Full-Text Articles in Physical Sciences and Mathematics
Environmental Magnetic Records Of Mid-Late Pleistocene Drift Sedimentary Sequences From The Antarctic Peninsula, Pacific Margin, A. Venuti, F. Florindo, A. Caburlotto
Environmental Magnetic Records Of Mid-Late Pleistocene Drift Sedimentary Sequences From The Antarctic Peninsula, Pacific Margin, A. Venuti, F. Florindo, A. Caburlotto
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The Pacific Continental Margin of the Antarctic Peninsula was the area of interest of the Sediment Drift of The Antarctic Offshore Project (SEDANO Project). A paleomagnetic and environmental study was carried out on four Pleistocene sequences from Drift 7. High resolution measurements were performed on u-channels and about forty-three discrete samples. This work focus on the definition of the mineralogy of the main magnetic carriers which is still matter of debate and on the study of the short time variability of magnetite grain-size which results particularly evident during the last glaciation. ARM/κ magnetic parameter resulted to be a good record …
A Pleistocene Warming Event At 1 Ma In Prydz Bay, East Antarctica: Evidence From Odp Site 1165, G. Villa, C. Lupi, F. Florindo, Stephan Pekar
A Pleistocene Warming Event At 1 Ma In Prydz Bay, East Antarctica: Evidence From Odp Site 1165, G. Villa, C. Lupi, F. Florindo, Stephan Pekar
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Magneto-stratigraphic and nannofossil assemblage data from ODP Site 1165 evidence an anomalous warming event of the surface waters in and around Prydz Bay during the Early Pleistocene. This results from an increase in the abundance of nannofossils at Site 1165, that occurred at 1 Ma. High-resolution sampling permits a new bio-magnetostratigraphic interpretation for ODP Site 1165. A decrease in δ18O values at Sites 1165 and 1167 also occurs at this time, supporting the presence of warming conditions in the Prydz Bay area. A return to colder surface waters, indicated by the absence or rare occurrence of nannofossils in …
100 Million Years Of Antarctic Climate Evolution: Evidence From Fossil Plants, J. E. Francis, A. Ashworth, D. J. Cantrill, J. A. Crame, J. Howe, R. Stephens, A.-M. Tosolini, V. Thorn
100 Million Years Of Antarctic Climate Evolution: Evidence From Fossil Plants, J. E. Francis, A. Ashworth, D. J. Cantrill, J. A. Crame, J. Howe, R. Stephens, A.-M. Tosolini, V. Thorn
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The evolution of Antarctic climate from a Cretaceous greenhouse into the Neogene icehouse is captured within a rich record of fossil leaves, wood, pollen, and flowers from the Antarctic Peninsula and the Transantarctic Mountains. About 85 million years ago, during the mid-Late Cretaceous, flowering plants thrived in subtropical climates in Antarctica. Analysis of their leaves and flowers, many of which were ancestors of plants that live in the tropics today, indicates that summer temperatures averaged 20°C during this global thermal maximum. After the Paleocene (~60 Ma) warmth-loving plants gradually lost their place in the vegetation and were replaced by floras …
Herbivory In Antarctic Fossil Forests: Evolutionary And Palaeoclimatic Significance, C. M. Mcdonald, J. E. Francis, S. G.A. Compton, A. Haywood, A. C. Ashworth, Luis Felipe Hinojosa, J. Smellie
Herbivory In Antarctic Fossil Forests: Evolutionary And Palaeoclimatic Significance, C. M. Mcdonald, J. E. Francis, S. G.A. Compton, A. Haywood, A. C. Ashworth, Luis Felipe Hinojosa, J. Smellie
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Many collections of Eocene Fossil leaves from Antarctica contain a rich store of insect trace fossils, indicating that insects were an important component of the unique forests that grew in polar regions. However, insect body fossils themselves are rare and so insect traces provide an excellent opportunity to examine both the palaeoentomology and the palaeoclimate of Antarctica. The fossils studied include Eocene leaves from both Seymour Island and King George Island on the Antarctic Peninsula. A database of all insect traces on the Antarctic fossil leaves was compiled and analysed in terms of the diversity of palaeoherbivory. The fossil leaves …
The Neogene Biota Of The Transantarctic Mountains, A. C. Ashworth, A. R. Lewis, D. R. Marchant, R. A. Askin, D. J. Cantrill, J. E. Francis, M. J. Leng, A. E. Newton, J. I. Raine, M. Williams, A. P. Wolfe
The Neogene Biota Of The Transantarctic Mountains, A. C. Ashworth, A. R. Lewis, D. R. Marchant, R. A. Askin, D. J. Cantrill, J. E. Francis, M. J. Leng, A. E. Newton, J. I. Raine, M. Williams, A. P. Wolfe
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Neogene fossil assemblages are described from three localities in the Transantarctic mountains. The plant fossils, include diatoms and algal spores, megaspores of Isoetes, pollen of angiosperms and gymnosperms, wood and leaves of Nothofagus, cushion growth forms of a vascular plant and a moss species, mats of exceptionally well- preserved moss species with delicate leaves attached to stems, and achenes and fruits of vascular plant species including Ranunculus. The invertebrate fossils include disarticulated chitinous parts of beetles and flies, cypridoidean ostracods and the shells of freshwater molluscs. The only vertebrate fossil is that of a fish. The fossil …
Terminal Cretaceous Climate Change And Biotic Response In Antarctica, V. C. Thorn, J. E. Francis, J. B. Riding, R. W. Raiswell, D. Pirrie, A. Haywood, J. A. Crame, J. M. Marshall
Terminal Cretaceous Climate Change And Biotic Response In Antarctica, V. C. Thorn, J. E. Francis, J. B. Riding, R. W. Raiswell, D. Pirrie, A. Haywood, J. A. Crame, J. M. Marshall
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Latest Cretaceous to early Palaeogene climates in Antarctica are being investigated from an exceptional sedimentary sequence on Seymour Island (James Ross Basin, Antarctic Peninsula) to determine the nature of climate change at the end of the Cretaceous. It has been suggested that, following peak mid Cretaceous warmth, cooling during the Maastrichtian (~71-65 Ma) may have been severe enough for short-term glaciations at high latitudes, challenging the current view of an ice-free, Cretaceous greenhouse world. High resolution records of palaeontological, sedimentological, and geochemical signals are being obtained to investigate the climate and environmental context at the Antarctic margin prior to the …
Divergent Flow Of The West Antarctic Ice Sheet On The Outer Continental Shelf Of The Amundsen Sea During The Late Quaternary, T. J. Deen, R. D. Larter, K. Gohl, A. G.C. Graham, C.-D. Hillenbrand, G. Kuhn, J. A. Smith
Divergent Flow Of The West Antarctic Ice Sheet On The Outer Continental Shelf Of The Amundsen Sea During The Late Quaternary, T. J. Deen, R. D. Larter, K. Gohl, A. G.C. Graham, C.-D. Hillenbrand, G. Kuhn, J. A. Smith
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Understanding the past glacial history of regions undergoing potential rapid deglaciation is essential in order to estimate the possible threat of sea level rise. Recently acquired data have given new images of mega-scale glacial lineations on the sea floor of the Amundsen Sea, which provide us a new understanding of the direction of glacial flow on the continental shelf of the Amundsen Sea region. Two adjacent areas of seafloor on the outer shelf of the Amundsen Sea embayment exhibit remarkably different styles of glacial lineations, and allow the interpretation of a divergent glacial trough for the Pine Island Glacier during …
Late Quaternary Ice Sheet Dynamics And Deglaciation History Of The West Antarctic Ice Sheet In The Amundsen Sea Embayment: Preliminary Results From Recent Research Cruises, A. G.C. Graham, R. D. Larter, K. Gohl, C.-D. Hillenbrand, J. A. Smith, J. S. Johnson, G. Kuhn
Late Quaternary Ice Sheet Dynamics And Deglaciation History Of The West Antarctic Ice Sheet In The Amundsen Sea Embayment: Preliminary Results From Recent Research Cruises, A. G.C. Graham, R. D. Larter, K. Gohl, C.-D. Hillenbrand, J. A. Smith, J. S. Johnson, G. Kuhn
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The threat, in terms of sea level rise, posed by the potential rapid deglaciation of West Antarctica means there is an urgent need to know more about the speed and style of marine ice sheet retreat. Quaternary deglacial events recorded in marine sediments provide an opportunity to understand the future of the modern day ice sheet. In this context, we examine the glacial history of a particularly poorly understood sector of the West Antarctic continental shelf – the Amundsen Sea Embayment –using new data from two recent research cruises. This extended abstract describes how marine geological and geophysical data are …
Buried Oligocene Glacial Topography Beneath A Smooth Middle Miocene Unconformity In The Southeast Ross Sea: Evolution Of West Antarctic Glaciation, C. C. Sorlien, D. S. Wilson, B. P. Luyendyk, L. R. Bartek, R. C. Decesari, J. B. Diebold
Buried Oligocene Glacial Topography Beneath A Smooth Middle Miocene Unconformity In The Southeast Ross Sea: Evolution Of West Antarctic Glaciation, C. C. Sorlien, D. S. Wilson, B. P. Luyendyk, L. R. Bartek, R. C. Decesari, J. B. Diebold
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Buried U-shaped troughs as much as 20 km-wide and flat-topped ridges adjacent to western Marie Byrd Land have recently been proposed as the result of late Oligocene West Antarctic glaciation. Here, additional evidence for pre-25 Ma glaciation is presented for the southeast Ross Sea, together with a different stratigraphic correlation path that establishes age constraints. Buried rough glacial topography interpreted to be of Oligocene age contrasts with a buried smooth and planar middle Miocene “Red” angular unconformity. The Red unconformity extends east-west 160 km near the ice shelf edge, and is 700 m-deep. Part of a 2 km section of …
Contrasting Sub-Ice Shelf, Sub Glacial And Glacial Marine Deposition: Implications For Ice Shelf Stability, L. W. Boyd, L. R. Bartek, B. P. Luyendyk, D. Wilson
Contrasting Sub-Ice Shelf, Sub Glacial And Glacial Marine Deposition: Implications For Ice Shelf Stability, L. W. Boyd, L. R. Bartek, B. P. Luyendyk, D. Wilson
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Data from cores collected from sites that were beneath the Ross Ice Shelf until 2000 and 2002 indicate that sub-ice shelf lithofacies are distinguishable from sub-glacial and glacial marine facies. Glacial marine sediment is characterized by diatom-rich, low-density, olive-green, sandy-muds, whereas sub-ice shelf sediment is defined by a lack of diatoms and muds that are enriched in silt and fine sand. Sub-glacial sediment is composed of diatom-poor, high density, coarse grained sandy-mud, rich in fine to coarse sized pebbles. Repetitive, fining-up packages, composed of fine-sand/silty-mud (distal sub ice-shelf deposits), grading into coarse pebbly-mud (sub ice-shelf proximal to the grounding line), …
Cretaceous And Tertiary Extension Throughout The Ross Sea, Antarctica, Robert C. Decesari, D. S. Wilson, B. P. Luyendyk, Michael Faulkner
Cretaceous And Tertiary Extension Throughout The Ross Sea, Antarctica, Robert C. Decesari, D. S. Wilson, B. P. Luyendyk, Michael Faulkner
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Marine geophysical data from the deep sea adjacent to the Ross Sea, Antarctica suggest that 170 km of extension occurred between East and West Antarctica from 46 to 21 Ma. The Northern and Victoria Land Basins in the western Ross Sea adjacent to the Transantarctic Mountains accommodated 95 km of this extension. Several kilometers of Oligocene sediments are found in the Central Trough and Eastern Basin in the eastern Ross Sea. Subsidence modeling accounts for these accumulations with about 40 km of extension in each basin centered on 35 Ma; therefore Ross Sea-wide Tertiary extension was comparable to extension in …
Regional Seismic Stratigraphic Correlations Of The Ross Sea: Implications For The Tectonic History Of The West Antarctic Rift System, R. C. Decesari, C. C. Sorlien, B. P. Luyendyk, D. S. Wilson, L. R. Bartek, John Diebold, Sarah E. Hopkins
Regional Seismic Stratigraphic Correlations Of The Ross Sea: Implications For The Tectonic History Of The West Antarctic Rift System, R. C. Decesari, C. C. Sorlien, B. P. Luyendyk, D. S. Wilson, L. R. Bartek, John Diebold, Sarah E. Hopkins
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Using existing and new seismic reflection data, new and updated correlations of late Oligocene-early Miocene RSS-2 strata were made between the southern parts of Ross Sea basins. Previous studies documented Cretaceous extension across much of Ross Sea. We interpret that Cenozoic extension also occurred across Ross Sea. Subsidence during and following this extension deepened existing basins and may have initiated basins in the west, subsiding ridges between basins below sea level during the late Oligocene. Pre-Oligocene strata record cessation of L. Cretaceous extension in easternmost Ross Sea. Successively younger Cenozoic extension occurred from east to west across the rest of …
Scale Of Subglacial To Sub-Ice Shelf Facies Variability, Eastern Basin, Ross Sea, Audrey S. Loth, L. R. Bartek Iii, B. P. Luyendyk, D. S. Wilson, Christopher C. Sorlien
Scale Of Subglacial To Sub-Ice Shelf Facies Variability, Eastern Basin, Ross Sea, Audrey S. Loth, L. R. Bartek Iii, B. P. Luyendyk, D. S. Wilson, Christopher C. Sorlien
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The Eastern Basin within the Ross Sea records changes in the volume of the West Antarctic Ice Sheet (WAIS). Examination of multibeam data revealed four acoustic facies that vary from west to east in a 900 km2 area. It is hypothesized that these facies, that formed nearly contemporaneously, are the result of differences in proximity to the grounding line and its relationship with the seafloor. The four facies are 1. Mega-Scale Lineation, 2. Slightly-Lineated Ridge Crest, 3. Discontinuous Ridges, 4. Irregular Mounds. These trends were also seen in SCS data, distinctively on the seafloor and mutedly at depth. Through determining …
40Ar-39Ar Age Constraints On Volcanism And Tectonism In The Terror Rift Of The Ross Sea, Antarctica, S. E. Rilling, S. B. Mukasa, T. J. Wilson, L. A. Lawver
40Ar-39Ar Age Constraints On Volcanism And Tectonism In The Terror Rift Of The Ross Sea, Antarctica, S. E. Rilling, S. B. Mukasa, T. J. Wilson, L. A. Lawver
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Volcanic sills and dikes inferred from seismic reflection profiles and geophysical studies of the Ross Sea are thought to be related to the rift basins in the region, and their emplacement to be coeval with extension. However, lack of precise geochronology in the Terror Rift of the Ross Sea region has left these inferred relationships poorly constrained and has hindered neotectonic studies, because of the large temporal gaps between seismic reflectors of known ages. New 40Ar/39Ar geochronology presented here for submarine volcanic rocks provides better age constraints for neotectonic interpretations within the Terror Rift. Several samples from …
Lu−Hf Systematics Of The Ultra-High Temperature Napier Complex, East Antarctica: Evidence For The Early Archean Differentiation Of Earth’S Mantle, S. B. Mukasa, S. H. Choi, A. V. Andronikov, Y. Osanai, S. L. Harley, N. M. Kelly
Lu−Hf Systematics Of The Ultra-High Temperature Napier Complex, East Antarctica: Evidence For The Early Archean Differentiation Of Earth’S Mantle, S. B. Mukasa, S. H. Choi, A. V. Andronikov, Y. Osanai, S. L. Harley, N. M. Kelly
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The Napier Complex comprises some of the oldest rocks on earth (~3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean−Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing an equilibrated assemblage from this belt yield a Lu−Hf isochron age of 2,403 ± 43 Ma. Preservation of the UHT mineral assemblage in the rock analyzed suggests rapid cooling with closure likely to have occurred for the Lu−Hf system at post-peak UHT conditions near a temperature of ~800°C. Zircon εHf values measured “see through” the UHT metamorphism and show that the source of …
A Sediment Model And Retreat History For The Ross Ice (Sheet) Shelf In The Western Ross Sea Since The Last Glacial Maximum, R. M. Mckay, G. B. Dunbar, T. R. Naish, P. J. Barrett, L. Carter, M. Harper
A Sediment Model And Retreat History For The Ross Ice (Sheet) Shelf In The Western Ross Sea Since The Last Glacial Maximum, R. M. Mckay, G. B. Dunbar, T. R. Naish, P. J. Barrett, L. Carter, M. Harper
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Three sediment gravity cores collected from beneath the McMurdo Ice Shelf and six piston cores from the Erebus Basin (in McMurdo Sound) and the Lewis Basin (north of Ross Island) were analysed in order to construct a retreat history for the West Antarctic Ice Sheet in the Ross embayment since the Last Glacial Maximum. The cores display a characteristic succession of sedimentary facies that record a transition from deposition beneath a marine terminating ice sheet to open-marine conditions. The base of the succession comprises a slightly consolidated, clast-rich muddy diamict dominated by basement clasts from the Transantarctic Mountains, and interpreted …
Showing A Strong Link Between Climatic And PCo2 Changes: Resolving Discrepancies Between Oceanographic And Antarctic Climate Records For The Oligocene And Early Miocene (34-16 Ma), Stephan Pekar, N. Christie-Blick
Showing A Strong Link Between Climatic And PCo2 Changes: Resolving Discrepancies Between Oceanographic And Antarctic Climate Records For The Oligocene And Early Miocene (34-16 Ma), Stephan Pekar, N. Christie-Blick
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An apparent mismatch between published oxygen isotope data and other paleoclimate proxies for the span from 26-16 Ma is resolved by calibration against eustatic estimates obtained from backstripped continental margin stratigraphy. Ice-volume estimates from calibrated oxygen isotope data compare favorably with stratigraphic and palynological data from Antarctica, and with estimates of atmospheric carbon dioxide for the early Oligocene through early Miocene (34-16 Ma). These isotopic data suggest that the East Antarctic Ice Sheet grew to as much as 30% greater than the present-day ice volume at glacial maxima. This conclusion is corroborated by seismic reflection and stratigraphic data from the …
Constraints From Detrital Zircon Geochronology On The Early Deformation Of The Ross Orogen, Transantarctic Mountains, Antarctica, Edmund Stump, George Gehrels, Franco M. Talarico, Rodolfo Carosi
Constraints From Detrital Zircon Geochronology On The Early Deformation Of The Ross Orogen, Transantarctic Mountains, Antarctica, Edmund Stump, George Gehrels, Franco M. Talarico, Rodolfo Carosi
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New ages of detrital zircons constrain the timing of the onset of deformation in the Ross orogen. In the Skelton Glacier area, Skelton Group was deformed before cross-cutting intrusion at 551 Ma. The youngest, significant, age-probability peaks from three samples of Skelton Group are 649 Ma, 684 Ma, and 691 Ma. The 649 Ma peak may be considered the maximum depositional age of Skelton Group, constraining the period of deformation to between 649 Ma and 551 Ma. In the upper Scott Glacier area, La Gorce Formation was deformed prior to cross-cutting intrusion at 526 Ma. The youngest, significant, age-probability peaks …
Gold Bearing Veining Linked To Transcrustal Fault Zones In The Transantarctic Mountains (Northern Victoria Land, Antarctica), L. Crispini, G. Capponi, L. Federico, F. Talarico
Gold Bearing Veining Linked To Transcrustal Fault Zones In The Transantarctic Mountains (Northern Victoria Land, Antarctica), L. Crispini, G. Capponi, L. Federico, F. Talarico
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Gold mineralization is associated with the paleo-Pacific margin of Gondwana and is related to processes of subduction/accretion and magmatism. Northern Victoria Land (Antarctica) was part of this margin during the Paleozoic, however no occurrence of gold has been reported up to now in the Transantarctic Mountains. Here we describe for the first time gold-bearing quartz veins in northern Victoria Land. The veins are hosted primarily by metabasalts and occur in a brittle-ductile high strain zone with curved geometry and reverse kinematic. Veins are extensional and shear veins; they often have ribbon/banded texture typical of crack and seal processes. Preliminary petrographic …
Geology Of The Byrd Glacier Discontinuity (Ross Orogen): New Survey Data From The Britannia Range, Antarctica, R. Carosi, F. Giacomini, F. Talarico, Edmund Stump
Geology Of The Byrd Glacier Discontinuity (Ross Orogen): New Survey Data From The Britannia Range, Antarctica, R. Carosi, F. Giacomini, F. Talarico, Edmund Stump
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Field activities in the Britannia Range (Transantarctic Mountains, Antarctica) highlighted new geological features around the so-called Byrd Glacier discontinuity. Recent field surveys revealed the occurrence of significant amounts of medium- to high-grade metamorphic rocks, intruded by abundant coarse-grained porphyritic granitoids. Most of the granitoids are deformed, with foliation parallel to the regional foliation in the metamorphics. Two main episodes of deformation are observed. Tight to isoclinal folds and penetrative axial plane foliation are related to the D1 phase, open folds to the D2. The main foliation (D1) trends nearly E-W in agreement with the trend in the southern portion of …
Summary And Highlights Of The 10th International Symposium On Antarctic Earth Sciences, T. J. Wilson, R. E. Bell, P. Fitzgerald, S. B. Mukasa, R. D. Powell, C. Finn
Summary And Highlights Of The 10th International Symposium On Antarctic Earth Sciences, T. J. Wilson, R. E. Bell, P. Fitzgerald, S. B. Mukasa, R. D. Powell, C. Finn
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The 10th International Symposium on Antarctic Earth Sciences (10th ISAES) was convened at the University of California, Santa Barbara, in August 2007. At the symposium about 350 researchers presented talks and posters with new results on major topics, including climate change, biotic evolution, magmatic processes, surface processes, tectonics, geodynamics, and the cryosphere. The symposium resulted in 335 papers and extended abstracts (Cooper et al., 2007, and this volume). Many science discoveries were presented spanning the last 2 billion years, from times when Antarctica was part of former supercontinents Rodinia and Gondwana to the present when Antarctica is an isolated, ice-covered …
A High-Resolution Aeromagnetic Survey Over The Cape Roberts Rift Basin: Correlations With Seismic Reflection And Magnetic Susceptibility Log Data, E. Armadillo, F. Ferraccioli, M. Gambetta, F. Talarico, A. Zunino, M. Zangani, E. Bozzo
A High-Resolution Aeromagnetic Survey Over The Cape Roberts Rift Basin: Correlations With Seismic Reflection And Magnetic Susceptibility Log Data, E. Armadillo, F. Ferraccioli, M. Gambetta, F. Talarico, A. Zunino, M. Zangani, E. Bozzo
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A high-resolution aeromagnetic survey (altitude 125 m asl, spacing 500 m , area 800 km2) was carried out in 1994 offshore of Cape Roberts by the GITARA (German ITalian Aeromagnetic Research in Antarctica) Group. The availability from drilling of whole-core physical properties logs for magnetic susceptibility, P-wave velocity and density/porosity data allows new insights to be inferred from reprocessed and reviewed HRAM aeromagnetic data. Aeromagnetic data have been reprocessed to image with greater detail the structural framework along the western flank of the Victoria Land Basin. New processing includes 2D Werner and 3D Euler deconvolution, the production of …