Palaeozoic to Mesozoic polyphase deformation of the Patuxent Range, Pensacola Mountains, Antarctica

Abstract

The Patuxent Range forms the most southerly third of the Pensacola Mountains, East Antarctica. Largely unstudied since the original geological survey work of the 1960s, the Patuxent Range was thought to expose metasediments deformed by a single Precambrian event. However, new structural data collected from two geographically separate areas in the central Patuxent Range reveal the presence of three distinct generations of structures. A synthesis of the regional geology together with new data suggests that the Patuxent Formation was mildly deformed during end Cambrian times as part of the late stage Ross Orogeny. However, the most intense deformation, although poorly constrained in age, probably occurred during the Permo-Triassic Gondwanian Orogeny. A third phase of deformation predates the intrusion of 183 Ma lamprophyre dykes and involved an inferred vertical axis rotation of the pre-existing D₁ and D₂ structures and the localized development of a spaced foliation and mesoscale folding. These D₃ structures may be the first evidence of an Early Jurassic deformation event in the Transantarctic Mountains, which correlates with the Peninsula and Rangitata I orogenies of the Antarctic Peninsula and New Zealand, respectively.