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Abstract New geophysical data from Antarctica's Ross Embayment reveal the structure and subglacial geology of extended continental crust beneath the Ross Ice Shelf. We use airborne magnetic data from the ROSETTA‐Ice Project to locate the contact between magnetic basement and overlying sediments. We delineate a broad, segmented basement high with thin (0–500m) non‐magnetic sedimentary cover which trends northward into the Ross Sea's Central High. Before subsiding in the Oligocene, this feature likely facilitated early glaciation in the region and subsequently acted as a pinning point and ice flow divide. Flanking the high are wide sedimentary basins, up to 3700m deep, which parallel the Ross Sea basins and likely formed during Cretaceous‐Neogene intracontinental extension. NW‐SE basins beneath the Siple Coast grounding zone, by contrast, are narrow, deep, and elongate. They suggest tectonic divergence upon active faults that may localize geothermal heat and/or groundwater flow, both important components of the subglacial system. 

The work is Chapter Three in a volume that provides a comprehensive overview of the geology of the Antarctic continent. The book represents the first comprehensive update of Antarctic geology in 25 years or more. Knowledge of the geology of Antarctica -- even if based on the meager <2% of rock exposure for this continent-- has immeasurably increased over that quarter-century. Individual chapters cover the regional geology of the seven main physiographic regions of Antarctica: -the Antarctic Peninsula, -West Antarctica (Marie Byrd Land and Enderby Land), -Transantarctic Mountains, -the Shackleton Range and its surroundings (including the Bertrab, Littlewood and Moltke Nunataks), -Dronning Maud Land, -Lambert Glacier and the area surrounding it, -East Antarctica from Kaiser-Wilhelm-II.-Land to George V Land/Terre Adélie. Each chapter contains a topographic, historical and geological overview, a description of the respective geological units, their stratigraphy and related data and the tectonic structure of the respective region. The seven chapters were written by acknowledged specialists in their field who place the regional geology into a continent-wide/plate tectonic/geological context.