Antarctic Phanerozoic landscape evolution along the Transantarctic basin from thermochronology

Abstract

Geophysical studies reveal a rugged landscape underlying the Antarctic ice sheets, but the geologic factors that led to this highly variable bedrock topography remain unresolved. Subsidence of Transantarctic Mountains crust, induced, for example, by long-term crustal extension before Cenozoic exhumation and Cretaceous–Cenozoic rifting, has been previously inferred from geologic and thermochronological records. There are, however, uncertainties about the thermochronological history of basement rocks in the Transantarctic Mountains, particularly for the Paleozoic following the late Neoproterozoic to early Paleozoic Ross-Delamerian orogeny. Here we show that K-feldspar ⁴⁰Ar/³⁹Ar cooling ages (∼350–150 °C closure temperature) from granitoid bodies collected from a large region across the Transantarctic Mountains are consistent with local punctuated exhumation of basement highs in the Silurian–Devonian, Carboniferous–Triassic, and Cretaceous–Paleocene. Times of increased exhumation correlate with periods of erosion and nearby sedimentation, including the Late Paleozoic Ice Age glaciation. They also correlate with the known timing of outboard plate-margin tectonism, suggesting the presence of dynamic inboard Paleozoic-Mesozoic landscapes influenced by cycles of crustal deformation and possibly, glaciation along the Pacific-Gondwana margin. The results indicate a geologic history like Antarctica’s contiguous margin in eastern Australia and highlight the importance of collecting comprehensive time-temperature data to fully understand the evolution of bedrock relief. The data suggest similar thermochronological analyses of subglacial bedrock of East Antarctica and submarine rocks of the West Antarctic rift system have significant potential to provide new insight into the origin of Antarctica’s subglacial bedrock topography and its potential influence on Paleozoic and Cenozoic glacial cycles.