Hidden tunnel valleys of the past: early glacial insights from George V Basin, East Antarctica

The George V Basin (GVB) of the East Antarctic sector is a glacially carved trough that served as sediment basin, preserving the early history of sediment supply and glacial dynamics. In this study, we present the first conclusive evidence of meltwater channels eroding into the sedimentary substrate within the GVB, interpreted as tunnel valleys—the largest reported to date from Antarctica, measuring 450 meters in depth and ranging from 1.7 to 5 kilometers in width. 2D seismic data reveal a complex sedimentary infill within the valleys, showing considerable lateral variability that reflects distinct depositional processes. Seismic stratigraphy and facies analysis, in conjunction with data from IODP site U1360, suggest that these valleys formed sometime between the Eocene-Oligocene (E-O) boundary and the early Miocene. The ancient tunnel valleys reported at the east sector of the Wilkes Land margin, adding to evidence for the existence of melt-rich glacial systems during Oligocene time. Additional seismic data and backstripping analyses indicate that the GVB experienced 400–600 meters of uplift due to subsidence and fluctuations in ice volume around the E-O boundary and the early Miocene time. The morphology, orientation, and sedimentary infill of the valleys provide insights into past subglacial hydrology, erosion by meltwater, and the dynamic nature of glacial systems in the region, which significantly influenced the sedimentation patterns and topography of the Antarctic continental shelf.