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The second generation Antarctic magnetic anomaly compilation for the region south of 60°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.Plain Language Summary Given the ubiquitous polar cover of snow, ice, and seawater, the magnetic anomaly compilation offers important constraints on the global tectonic processes and crustal properties of the Antarctic. It also links widely separated areas of outcrop to help unify disparate geologic studies and provides insights on the lithospheric transition between Antarctica and adjacent oceans, as well as the geodynamic evolution of the Antarctic lithosphere in the assembly and breakup of the Gondwana, Rodinia, and Columbia supercontinents and key piercing points for reconstructing linkages between the protocontinents. The magnetic data together with ice-probing radar and gravity information greatly facilitate understanding the evolution of fundamental large-scale geological processes such as continental rifting, intraplate mountain building, subduction and terrane accretion processes, and intraplate basin formation.

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East Antarctica hosts large subglacial basins into which the East Antarctic Ice Sheet (EAIS) likely retreated during past warmer climates. However, the extent of retreat remains poorly constrained, making quantifying past and predicted future contributions to global sea level rise from these marine basins challenging. Geomorphological analysis and flexural modeling within the Wilkes Subglacial Basin are used to reconstruct the ice margin during warm intervals of the Oligocene-Miocene. Flat-lying bedrock plateaus are indicative of an ice sheet margin positioned >400-500 km inland of the modern grounding zone for extended periods of the Oligocene-Miocene, equivalent to a 2-m rise in global sea level. Our findings imply that if major EAIS retreat occurs in the future, isostatic rebound will enable the plateau surfaces to act as seeding points for extensive ice rises, thus limiting extensive ice margin retreat of the scale seen during the early EAIS. Plain Language SummaryThe Wilkes Subglacial Basin is a large, low-lying topographic depression situated beneath the Antarctic Ice Sheet. Because the land surface of the basin is currently situated below sea level, it is a potential site of ice sheet collapse and rapid retreat in a warming world. Understanding this landscape and how it has evolved through time in relation to past climate and sea level is therefore key to understanding the future dynamics of this part of the ice sheet. Here we report the discovery, using ice-penetrating radar data sets, of extensive subglacial bedrock plateaus within the Wilkes Subglacial Basin. We analyze the geomorphology of these plateau surfaces and reconstruct the evolution of the subglacial landscape through time. Our results indicate that this part of the Wilkes Subglacial Basin was free of ice for extensive and prolonged periods of time during the early stages of ice sheet development. These constraints on past ice sheet extent, together with our landscape reconstruction, can be used by the ice sheet modeling community to better understand the likely future dynamics of this part of the Antarctic Ice Sheet.

Subglacial outburst floods at the margins of the Antarctic and Laurentide Ice Sheets have been linked to changes in global ocean circulation and climate. The impact of palaeo-hydrological systems beneath the East Antarctic Ice Sheet (EAIS) has, however, remained elusive. By analysing bed morphology in the Wilkes Subglacial Basin, we hypothesise the occurrence of a major palaeo-subglacial lake and associated outburst floods in the interior of East Antarctica. At 70 km wide and over 100 km long, the inferred area of outburst flooding is the most extensive in Antarctica, and the palaeo-subglacial lake from which the floods originated is the second largest after Lake Vostok. The scale of inferred outburst flooding is similar to mega-floods beneath the Laurentide Ice Sheet. We suggest that this major hydrological system developed during expansion of the EAIS in the middle Miocene and probably affected ice sheet stability, ocean circulation and climate evolution

Reconstructions of the bedrock topography of Antarctica since the Eocene‐Oligocene Boundary (approximately 34 Ma) provide important constraints for modeling Antarctic ice sheet evolution. This is particularly important in regions where the bedrock lies below sea level, since in these sectors the overlying ice sheet is thought to be most susceptible to past and future change. Here we use 3‐D flexural modeling to reconstruct the evolution of the topography of the Wilkes Subglacial Basin (WSB) and Transantarctic Mountains (TAM) in East Antarctica. We estimate the spatial distribution of glacial erosion beneath the East Antarctic Ice Sheet, and restore this material to the topography, which is also adjusted for associated flexural isostatic responses. We independently constrain our post‐34 Ma erosion estimates using offshore sediment stratigraphy interpretations. Our reconstructions provide a better‐defined topographic boundary condition for modeling early East Antarctic Ice Sheet history. We show that the majority of glacial erosion and landscape evolution occurred prior to 14 Ma, which we interpret to reflect more dynamic and erosive early ice sheet behavior. In addition, we use closely spaced 2‐D flexural models to test previously proposed hypotheses for a flexural origin of the TAM and WSB. The pre‐34 Ma topography shows lateral variations along the length of the TAM and WSB that cannot be explained by uniform flexure along the front of the TAM. We show that some of these variations may be explained by additional flexural uplift along the south‐western flank of the WSB and the Rennick Graben in northern Victoria Land.

Vertical-gradient microgravity and electrical-resistivity tomography geophysical surveys were performed over a shallow cave in the Italian Armetta Mountain karst area, close to the Liguria-Piedmont watershed. The aim of this study was to test the geophysical response of a known shallow cave. The shallowest portion of the cave exhibits narrow passages and, at about 30 meters below the entrance, a fossil meander linking two large chambers, the target of the geophysical survey. The integrated results of the two surveys show a clear geophysical response to the cave. The surveys exhibited high resistivity values and a negative gravity anomaly over the large cave passages. This work confirms the ability of these geophysical techniques to give the precise location of the voids, even in complex environments. The application of these techniques can be successful for site surveying where the presence of hollows may be expected.