Subglacial geology and palaeo flow of Pine Island Glacier from combining glacial erratics with geophysics

Subglacial geology plays a key role in determining the rate of ice flow and sensitivity of the glacial system to atmospheric or ocean warming. However, bedrock geology is often poorly known because direct information from subglacial samples is extremely challenging to obtain. Here, we combine the distribution, petrology, crystallisation age and thermochronology of glacial erratics with geophysical analyses to provide evidence for Middle Jurassic (~175 Ma) granitic bedrock extending beneath Pine Island Glacier, West Antarctica. Our results constrain the range of past ice flow pathways across the adjacent Hudson Mountains, providing information needed to improve models of ice sheet evolution in this vulnerable region. This work demonstrates the utility of integrating erratic geochemistry, geochronology and aerogeophysics for the study of subglacial environments and confirms erratics as a valuable, but largely untapped, source of evidence for what lies beneath the world’s ice sheets.