NEW TECTONIC BOUNDARY AND GONDWANA MARGIN INHERITANCE REVEALED IN CRUST BENEATH ROSS ICE SHELF, ANTARCTICA, THROUGH ROSETTA-ICE PROJECT INTEGRATION OF AEROGEOPHYSICS, GEOLOGY, AND OCEAN DATA

The East Gondwana convergent margin–now consisting of submerged plateaus and rises bordering Australia, Zealandia and Antarctica—consists of a belt of accreted terranes that was stitched by magmatic arcs, then attenuated to form throughgoing continental ribbons separated by narrow failed rift basins. This crustal architecture was discerned from marine geophysical exploration for the midlatitude coastal plateaus and rises. The ROSETTA-ICE project, a new airborne study of the little-known Ross Ice Shelf region, aims to determine crustal makeup, locate tectonic boundaries and calculate seafloor bathymetry using potential fields data. LC130 aircraft equipped with gravimeters, magnetometer and geopositioning are surveying 91 E-W lines at 10 km and 15 N-S tie lines at 55 km spacing, positioned to overfly 1970s depth and gravity points.

ROSETTA-ICE geophysics provides magnetic anomalies, Werner depth-to-basement solutions, a new gravity-based bathymetric model at 20-km resolution, and mapping of crustal density tied to the 1970s data. Contrary to current knowledge, the data reveal a major lithospheric boundary 300 km east of the Transantarctic Mountains beneath the floating sector of the West Antarctic ice sheet (WAIS), and demarcate two crustal regions that have contrasting geophysical characteristics and bathymetry. The East Antarctic side consists of a relatively dense integrated column of rock, with low amplitude magnetic anomalies, and deep bathymetry. The West Antarctic side displays high amplitude magnetic anomalies, lower overall density and shallower water depths. The Central High, a basement structure cored at DSDP Site 270 and seismically imaged in the Ross Sea, continues southward as a prominent ribbon of fault-riven continental crust that coincides with the tectonic boundary. Integrated with surface geology bordering the Ross Ice Shelf, the geophysical properties indicate a continuity of Gondwana margin crustal architecture beneath the WAIS, and the need for revision of the existing tectonic framework for West Antarctica. The crustal boundary—well-separated from the Transantarctic Mountains front, and associated narrow rift basins and transfer zones, control the bathymetry, influence oceanographic circulation, and may affect fluids and heat flow beneath the Ross Ice Shelf.