Уникальные геологические структуры района купола Лоу и ледников Вандерфорда и Тоттена (Земля Уилкса) по данным геофизических исследований

Wilkes Land is a key region for Gondwana reconstruction, however it remains one of the largest regions on Earth with poorest knowledge of geology. This study comprehensively reviews the ICECAP/ IceBridge geophysical data for the Law Dome region including Vanderford and Totten adjacent glaciers over Wilkes Land and their role in obtaining new insight on the East Antarctic geology hidden under the ice cover. We analyzed more than 100,000 line kilometers of new magnetic, gravity and subglacial bedrock topography data that are available through the National Snow and Ice Data Center (USA). The newly acquired data supports our previous idea of the continuous rift structure existence at the southern boundary of Law Dome that runs between Vanderford and Totten Glaciers. The rift length exceeds 400 km and width varies from 50 to 100 km. In accordance with results of depth to Moho estimations and density modelling, for axial part of the rift it is characteristic an essential thinning of the Earth crust thickness, it is raised up to 24–26 km and continue to be elevated along entire length of this structure. The thickness of sedimentary rocks within the rift exceeds 3 km, their high density probably evidence that they were formed during Late Paleozoic – Early Mesozoic. The results of our investigations support tectonic nature of this structure as continuous rift developed since the Mesozoic extension phase (~160 Ma) of the Wilkes Land continental margin. Second distinctive structure is the strong reversely magnetized Law Dome magnetic anomaly with an area of about 9,500 km2. This anomaly would map out one of the largest mafic/ultramafic intrusions of the Earth, similar in extent to Norway’s Bjerkreim-Sokndal layered intrusion, the Coompana Block gabbro in Australia, or even the granitic-gneiss complex in the Adirondack Mountains of North America.В работе анализируются геофизические данные проекта ICECAP/IceBridge для района купола Лоу на Земле Уилкса, которые подтверждают ранее высказанную идею о существовании рифтогенной структуры, подстилающей ледники Вандерфорда и Тоттена. Протяженность рифта превышает 400 км, а его ширина варьирует от 50 до 100 км. Результаты расчетов глубин до поверхности Мохоровичича свидетельствуют, что для осевой части рифта характерно существенное утонение коры до 24–26 км. Мощность осадочных отложений в пределах рифта превышает 3 км. Интенсивная отрицательная магнитная аномалия на куполе Лоу обусловлена обратным намагничением пород, ее площадь составляет порядка 9500 км2. Как наиболее вероятный источник аномалии рассматриваются породы гранитного или гранито-гнейсового состава

Recent magnetic views of the Antarctic lithosphere

Magnetic anomaly investigations are a key tool to help unveil subglacial geology, crustal architecture and the tectonic and geodynamic evolution of the Antarctic continent. Here, we present the second generation Antarctic magnetic anomaly compilation ADMAP 2.0 (Golynsky et al., 2018), that now includes a staggering 3.5 million line-km of aeromagnetic and marine magnetic data, more than double the amount of data available in the first generation effort. All the magnetic data were corrected for the International Geomagnetic Reference Field, diurnal effects, high-frequency errors and leveled, gridded,and stitched together. The new magnetic anomaly dataset provides tantalising new views into the structure and evolution of the Antarctic Peninsula and the West Antarctic Rift System within West Antarctica, and Dronning Maud Land, the Gamburtsev Subglacial Mountains, the Prince Charles Mountains, Princess Elizabeth Land, and Wilkes Land in East Antarctica, as well as key insights into oceanic gateways. Our magnetic anomaly compilation is helping unify disparate regional geologic and geophysical studies by providing larger-scale perspectives into the major tectonic and magmatic processes that affected Antarctica from Precambrian to Cenozoic times, including e.g. the processes of subduction and magmatic arc development, orogenesis, accretion, cratonisation and continental rifting, as well as continental margin and oceanic basin evolution. The international Antarctic geomagnetic community remains very active in the wake of ADMAP 2.0, and we will showcase some of their key ongoing study areas, such as the South Pole and Recovery frontiers, the Ross Ice Shelf, Dronning Maud Land and Princess Elizabeth Land

Air and shipborne magnetic surveys of the Antarctic into the 21st century

The Antarctic geomagnetics' community remains very active in crustal anomaly mapping. More than 1.5 million line-km of new air- and shipborne data have been acquired over the past decade by the international community in Antarctica. These new data together with surveys that previously were not in the public domain significantly upgrade the ADMAP compilation. Aeromagnetic flights over East Antarctica have been concentrated in the Transantarctic Mountains, the Prince Charles Mountains – Lambert Glacier area, and western Dronning Maud Land (DML) — Coats Land. Additionally, surveys were conducted over Lake Vostok and the western part of Marie Byrd Land by the US Support Office for Aerogeophysical Research projects and over the Amundsen Sea Embayment during the austral summer of 2004/2005 by a collaborative US/UK aerogeophysical campaign. New aeromagnetic data over the Gamburtsev Subglacial Mountains (120,000 line-km), acquired within the IPY Antarctica's Gamburtsev Province project reveal fundamental geologic features beneath the East Antarctic Ice sheet critical to understanding Precambrian continental growth processes. Roughly 100,000 line-km of magnetic data obtained within the International Collaboration for Exploration of the Cryosphere through Aerogeophysical Profiling promises to shed light on subglacial lithology and identify crustal boundaries for the central Antarctic Plate. Since the 1996/97 season, the Alfred Wegener Institute has collected 90,000 km of aeromagnetic data along a 1200 km long segment of the East Antarctic coast over western DML. Recent cruises by Australian, German, Japanese, Russian, British, and American researchers have contributed to long-standing studies of the Antarctic continental margin. Along the continental margin of East Antarctica west of Maud Rise to the George V Coast of Victoria Land, the Russian Polar Marine Geological Research Expedition and Geoscience Australia obtained 80,000 and 20,000 line-km, respectively, of integrated seismic, gravity and magnetic data. Additionally, US expeditions collected 128,000 line-km of shipborne magnetic data in the Ross Sea sector

Revealing the crustal architecture of the least understood composite craton on Earth: East Antarctica

East Antarctica hosts one of the largest Precambrian cratons on Earth. Meager coastal exposures and sediment provenance studies provide glimpses into up to 3 billion years of its geological history. Extensive ice sheet cover hampers however our knowledge of crustal architecture, and consequently the geodynamic processes responsible for the growth and amalgamation of East Antarctica have remained elusive. Here we exploit recent aerogeophysical exploration efforts to help unveil the large-scale crustal architecture of East Antarctica. We focus on three sectors of East Antarctica: the Transantarctic Mountains and Wilkes Basin area; the Recovery/Dronning Maud Land area and the Gamburtsev Province. These areas provide new insights into both the margins of the so called Mawson craton and the processes that affected its interior. A 1,900 km-long linear magnetic and gravity boundary is imaged along the western flank of the Wilkes Basin and interpreted here as a crustal-scale Paleoproterozoic suture zone (ca 1.7 Ga) that inverted a former passive margin. Two ribbon-like Archean and Paleoproterozic microcontinents were assembled during this stage, resembling modes of amalgamation of Paleoproterozoic microcontinental ribbons in Australia. The proposed Proterozoic sutures and microcontinent boundaries also influenced Neoproterozoic rifted margin and early Cambrian back-arc basins in the Wilkes Basin/Transantarctic Mountains region. In the Recovery/Dronning Maud Land region our new potential field compilations reveal a wide tract of anastomising crustal-scale shear zones, likely of Pan-African age that flank and variably deform the margins of several distinct Archean, Paleo-Mesoproterozoic and Grenvillian age crustal blocks. In the Gamburtsev Province new magnetic and gravity models provide insights into the Gamburtsev Suture (Ferraccioli et al., 2011, Nature) that separates the Ruker Province from an inferred Grenvillian-age orogenic Gamburtsev Province with remarkably thick crust (up to 60 km thick) and thick lithosphere (over 200 km thick). We suggest that a recently inferred Tonian-age accretionary belt identified in the Sor Rondane region continues further inland in the Gamburtsev Province and was likely also reactivated during Pan-African age transpression linked to Gondwana assembly

New Magnetic Anomaly Map of the Antarctic

The second generation Antarctic magnetic anomaly compilation for the region south of 60 degrees S includes some 3.5 million line-km of aeromagnetic and marine magnetic data that more than doubles the initial map's near-surface database. For the new compilation, the magnetic data sets were corrected for the International Geomagnetic Reference Field, diurnal effects, and high-frequency errors and leveled, gridded, and stitched together. The new magnetic data further constrain the crustal architecture and geological evolution of the Antarctic Peninsula and the West Antarctic Rift System in West Antarctica, as well as Dronning Maud Land, the Gamburtsev Subglacial Mountains, the Prince Charles Mountains, Princess Elizabeth Land, and Wilkes Land in East Antarctica and the circumjacent oceanic margins. Overall, the magnetic anomaly compilation helps unify disparate regional geologic and geophysical studies by providing new constraints on major tectonic and magmatic processes that affected the Antarctic from Precambrian to Cenozoic times.Korea Polar Research Institute (KOPRI) programs, PM15040 and PE17050Germany's AWI/Helmholtz Center for Polar and Marine ResearchFederal Institute for Geosciences and Natural ResourcesBritish Antarctic Survey/Natural Environmental Research CouncilItalian Antarctic Research ProgrammeRussian Ministry of Natural ResourcesU.S. National Science Foundation and National Space and Aeronautics AdministrationAustralian Antarctic Division and Antarctic Climate & Ecosystem Cooperative Research CentreFrench Polar InstituteGlobal geomagnetic observatories network (INTERMAGNET

Bathymetry Beneath Ice Shelves of Western Dronning Maud Land, East Antarctica, and Implications on Ice Shelf Stability

Antarctica's ice shelves play a key role in stabilizing the ice streams that feed them. Since basal melting largely depends on ice-ocean interactions, it is vital to attain consistent bathymetry models to estimate water and heat exchange beneath ice shelves. We have constructed bathymetry models beneath the ice shelves of western Dronning Maud Land by inverting airborne gravity data and incorporating seismic, multibeam, and radar depth references. Our models reveal deep glacial troughs beneath the ice shelves and terminal moraines close to the continental shelf breaks, which currently limit the entry of Warm Deep Water from the Southern Ocean. The ice shelves buttress a catchment that comprises an ice volume equivalent to nearly 1 m of eustatic sea level rise, partly susceptible to ocean forcing. Changes in water temperature and thermocline depth may accelerate marine-based ice sheet drainage and constitute an underestimated contribution to future global sea level rise

A new heat flux model for the Antarctic Peninsula incorporating spatially variable upper crustal radiogenic heat production

A new method for modelling heat flux shows the upper crust contributes up to 70% of the Antarctic Peninsula's subglacial heat flux, and that heat flux values are more variable at smaller spatial resolutions than geophysical methods can resolve. Results indicate a higher heat flux on the east and south of the Peninsula (mean 81 mWm-2) where silicic rocks predominate, than on the west and north (mean 67 mWm-2) where volcanic arc and quartzose sediments are dominant. Whilst the data supports the contribution of HPE-enriched granitic rocks to high heat flux values, sedimentary rocks can be of comparative importance dependent on their provenance and petrography. Models of subglacial heat flux must utilize a heterogeneous upper crust with variable radioactive heat production if they are to accurately predict basal conditions of the ice sheet. Our new methodology and dataset facilitate improved numerical model simulations of ice sheet dynamics

Holocene glacial activity in Barilari Bay, west Antarctic Peninsula, tracked by magnetic mineral assemblages: Linking ice, ocean, and atmosphere

We investigate the origin and fate of lithogenic sediments using magnetic mineral assemblages in Barilari Bay, west Antarctic Peninsula (AP) from sediment cores recovered during the Larsen Ice Shelf System, Antarctica (LARISSA) NBP10-01 cruise. To quantify and reconstruct Holocene changes in covarying magnetic mineral assemblages, we adopt an unsupervised mathematical unmixing strategy and apply it to measurements of magnetic susceptibility as a function of increasing temperature. Comparisons of the unmixed end-members with magnetic observations of northwestern AP bedrock and the spatial distribution of magnetic mineral assemblages within the fjord, allow us to identify source regions, including signatures for ‘‘inner bay,’’ ‘‘outer bay,’’ and ‘‘northwestern AP’’ sources. We find strong evidence that supports the establishment of a late Holocene ice shelf in the fjord coeval with the Little Ice Age. Additionally, we present new evidence for late Holocene sensitivity to conditions akin to positive mean Southern Annual Mode states for western AP glaciers at their advanced Neoglacial positions