54 research outputs found
Environmental and climate changes in Antarctica in the Geological Past
No full textIn the Cretaceous time, Antarctica was characterized by subtropical and tropical climate. The Early Eocene was warmest in the Antarctic history but this Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica at about 34 Ma ago. There is indirect evidence that small ice caps developed within central Antarctica in the Late Eocene (42−34 Ma). From the Early Oligocene to the Middle Miocene (34−13 Ma) ice sheet was wet-based and fluctuated considerably in volume, but about 14 m.y. ago it became dry-based and more stable. Seismic data collected on the East Antarctic margin give valuable information on dynamics of the past ice sheets. These data shows that the sedimentary cover of the western Wilkes Land margin includes a giant (c. 200 000 km2) deep-water fan which formed between c. 43 and 34 Ma ago. The average rate of sedimentation in the central part of fan was 230–250 m/m.y. Active input of terrigenous sediments into deep-water denotes high-energy fluvial system within the Wilkes Land. Emergence of this fluvial system evidences earliest glaciation in the Antarctic interior which fed full-flowing rivers. The thickness of strata deposited during post-Early Oligocene glaciations on the Antarctic margin generally reflects the averaged energy of depositional environments. The thickest sediments (up to 2.0 km, i.e. almost twice more than in other parts of East Antarctic margin) and inferred highest energy are seen in the central Cooperation Sea, on the central Wilkes Land margin and in the D'Urville Sea. The areas with the thickest post-Early Oligocene strata correlate with places where present-day ice discharge is highest, such as via the Lambert, Totten and Mertz/Ninnis Glaciers. The correlation points to high ice (and sediment) flux in the same areas since the Early Oligocene
Compilation of shipborne magnetic and gravity data images crustal structure of Prydz Bay (East Antarctica)
No full textA magnetic anomaly map and a free air anomaly map of Prydz Bay, of the adjacent slope and over the continental rise area (63°S-69.5°S, 69°E-81°E) were compiled using Russian, Australian, Japanese and other available data (more than 20 000 km in total length). Adjustment of different data sets was performed before gridding and making contour maps. Crossover differences of the magnetic data were significantly reduced by removing data segments with short-period time variations, by applying time variation corrections of Mawson Station to Australian and Japanese data, and by giving a constant bias to each trackline. Crossover differences of the gravity data were also substantially reduced by applying a constant bias to each cruise/leg. According to the compiled gravity data, in the western part of Prydz Bay the continent ocean boundary is inferred to be situated around the shelf edge at the seaward end of Prydz Channel, while it is in the continental rise in the eastern part. The gravity data also suggest the presence of sediments in the Prydz Bay basin reaching a thickness of about 8 km and overlying a "granitic" layer; the Moho beneath the basin is located at a depth of about 22 km. According to the magnetic data, highly-magnetized rocks occur at shallow depths northwest of the Prydz Bay basin and other parts of Prydz Bay.JCR Journalope
Current-controlled sedimentation in the north-western Weddell Sea
Get PDFThe sedimentary basins of the north-western Weddell Sea are characterized by a variety of contourite drifts. This study is aimed at their identification, spatial mapping and temporal evolution and based on the integration of a large amount of seismic data collected by different countries including the recent data of the Russian Antarctic Expedition. Most of the drifts in the region being studied are classified as separated, confined, plastered or sheeted. The chain of sediment wave fields is mapped in the western and northern Powell Basin. The earliest contourite drifts started to form in the Early Miocene or, possibly, in the Late Oligocene. The changes in the depositional pattern in the Middle Miocene and then in the Late Pliocene are thought to have resulted from successive intensification of the bottom currents. Контуритовые наносы, формируемые придонными течениями, могут использоваться для изучения циркуляции водных масс, так как по их параметрам и характеру распространения можно судить о направленности и относительной энергии придонных течений. В данной работе рассматриваются контуритовые наносы в северо-западной части моря Уэдделла, приводится схема распространения наносов и их классификация, а также реконструируется циркуляция водных масс в глубоководных бассейнах района. Исследования основаны на обобщении и интерпретации сейсмических данных отечественных и зарубежных экспедиций, большая часть которых доступна из международной библиотеки сейсмических данных по Антарктике. В результате анализа сейсмических данных в районе исследований в диапазоне глубин от 2000 до 4500 м выявлены отделенные, ограниченные, пластерные и покровные контуритовые наносы. Зарождение донных течений в северо-западной части моря Уэдделла началось с раскрытия бассейна Пауэлл, и развитие самых ранних контуритовых наносов предполагается 24–23 млн лет назад. В среднем миоцене и в позднем плиоцене отмечается усиление интенсивности донных течение и более широкое развитие контуритовых наносов.
Combined palaeotopography and palaeobathymetry of the Antarctic continent and the Southern Ocean since 34 Ma
No full textHigh-resolution palaeotopographic and -bathymetric models of the Southern Ocean and the Antarctic continent facilitate detailed investigation of past ice sheet and ocean circulation development from land to sea, which is essential for robust reconstructions of the paleoclimate, palaeocryosphere, and palaeoceanography.
These important boundary conditions have been newly reconstructed based on all available geophysical and geological data and merged together to form complete grids of the Southern Ocean and Antarctica. For detailed information on the reconstructions, please refer to Paxman et al. (2019) and Hochmuth et al. (2020) for the palaeotopography and the palaeobathymetry, respectively. For further information on the merging process, please see the attached readme document.
We present a compilation of the merged palaeotopography and palaeobathymetry for five key time slices in the Cenozoic development of the Antarctic continent and the Southern Ocean:
(i) Eocene/Oligocene Boundary (34 Ma), (ii) Oligocene/Miocene Transition (23 Ma), (iii) middle Miocene (14 Ma), (iv) early Pliocene (5 Ma), and (v) Pliocene/Pleistocene Boundary (2.6 Ma).
Note: The primary authors of the original publications, G. Paxman and K. Hochmuth are equally contributing joint first authors of this dataset compilation
Radio-Echo Sounding Investigations of Western Gronning Maud Land and North-Eastern Coats Land, East Antarctica
No full textStructure and Origin of the Earth´s Crust in the Weddell Sea Embayment (beneath the Front of the Filchner and Ronne Ice Shelves) from Deep Seismic Sounding data
No full textRemote sensing and mathematical modelling of Lake Vostok, East Antarctica: past, present and future research
No full textThe paper presents a review of the studies carried out in the area of the subglacial Lake Vostok (East Antarctica) to date. They include geophysical, glaciological, geodesic, and geological investigations. The most important geophysical investigations were carried out by the Polar Marine Geosurvey Expedition. They included reflection and refraction seismic, and also radio-echo sounding. The major contribution to the study of this region was made by American researchers, who in the 2000/01 field season performed a complex airborne geophysical survey on a regular network. Their work included magnetometric, gravimetric, and radio-echo sounding measurements. All the research conducted found that the water surface area is 15790 km2, and its altitudinal height changes from -600 to -150 m. The average depth of Lake Vostok is 400 m, and the maximum marks reach 1200 m. The water body volume is estimated at 6 100 km3. There are 11 islands in the lake, and their total area is 365 km2. In addition, 56 isolated subglacial water bodies were found around the lake. A special section is devoted to a review of mathematical models of heat and mass transfer processes in the glacier and water movement in Lake Vostok.Fil: Popov, S. V.. Polar Marine Geosurvey Expedition; Rusia. Saint Petersburg State University; RusiaFil: Boronina, A. S.. State Hydrological Institute; RusiaFil: Ekaykin, A. A.. Arctic And Antarctic Research Institute; RusiaFil: Klepikov, A. V.. Arctic And Antarctic Research Institute; RusiaFil: Leitchenkov, G. L.. All-Russia Research Institute for Geology and Mineral Resources of the World Ocean; Rusia. Saint Petersburg State University; RusiaFil: Lipenkov, V. Ya.. Arctic And Antarctic Research Institute; RusiaFil: Lukin, V. V.. Arctic And Antarctic Research Institute; RusiaFil: Masolov, V. N.. Polar Marine Geosurvey Expedition; RusiaFil: Richter, Andreas Jorg. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Laboratorio Maggia; Argentina. Technische Universität Dresden; AlemaniaFil: Vorobiov, D. M.. Polar Marine Geosurvey Expedition; RusiaFil: Cui, X.. Polar Research Institute Of China; ChinaFil: Qiao, G.. Tongji University; ChinaFil: Scheinert, M.. Technische Universität Dresden; AlemaniaFil: Dietrich, R.. Technische Universität Dresden; Alemani
Late Pleistocene glaciation and retreat of ice sheet on the shelf of the South Orkney Plateau, West Antarctica
Get PDFThe research aims to provide insight into reconstruction of the Late Pleistocene glaciations and ice retreat that followed the Last Glacial Maximum. The study is based on multi-channel seismic profiling and multibeam survey conducted on the shelf during the 63-rd Russian Antarctic Expedition (2018) on RV «Akademik Alexander Karpinsky». The 560-channel, 7000-m-long streamer and the Atlas Hydrosweep MD-3/30 multibeam echo-sounder were used for seismic and multibeam survey, respectively. In addition, previously collected seismic data available from the Antarctic Seismic Data Library System and bathymetry data from the «International Bathymetry Chart of the Southern Ocean» (IBCSO) Project were involved for interpretation. The multibeam survey was carried out within the Signy Trough and its flanks with depths ranging from 180 to 400 m, and covered the area of about 1500 km2. The data were collected along 43 profiles spaced at 750 m to ensure enough overlap between swaths. Variety of submarine glacial landforms formed by grounded ice was identified on shelf of the South Orkney Plateau with use of seismic and multibeam data. The most prominent of these features is the large terminal moraine at the middle shelf (previously described as the mid-shelf break) marking the greatest ice extent at the LGM. Oceanward of the large terminal moraine, the plateau-like feature (delineated by 350 and 425 m isobaths) with relatively steep outer slope is recognized from seismic data and interpreted as the distal terminal moraine formed during the pre-LGM Pleistocene glaciation. Within the Signy Trough, submarine glacial landforms mapped by multibeam survey, reflect ice retreat after the LGM; these landforms include: subglacial lineation at the western flank of the northern Signy Trough indicating fast flowing grounded ice, transverse recessional moraine ridges, lateral shear moraine on the western flank and lateral marginal moraine on the eastern flank of the Trough, two grounding zone wedges, streamlined features (drumlins) and an ice-proximal fan (presumably). The end moraine was also identified in the eastern flank of Signy Trough. It is thought to be formed due to ice (outlet glacier) re-advance during the Antarctic Cold Reversal. Numerous iceberg plough-marks were observed at least down to 370 m water depths
NUMERICAL MODELLING OF THE AUSTRALIA – ANTARCTICA CONJUGATE MARGINS USING THE GALO SYSTEM: PART 1. THE BREMER SUB‐BASIN, SW AUSTRALIA
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