Stratigraphy of Jurassic pyroclastic rocks in the Transantarctic Mountains

Abstract

Jurassic pyroclastic rocks cap the Antarctic Gondwana sequence and document an important event in the evolution of the continent. The Hanson Formation, which crops out in the central Transantarctic Mountains, consists of ca 240 m of silicic tuffs, tuffaceous sandstones, and subordinate quartzose sandstones of probable Early Jurassic age. It is overlain by basaltic pyroclastic rocks of the Prebble Formation. Similar basaltic rocks also crop out in Victoria Land and constitute the Mawson and Exposure Hill Formations. These basaltic pyroclastic rocks and the overlying Kirkpatrick Basalt lavas are Middle Jurassic. The pyroclastic rocks comprise thick tuff-breccias with minor lapilli-tuffs and tuffs; sequences are as much as 400 m thick. These silicic and basaltic pyroclastic rocks record the transition from foreland basin fluvial sedimentation of the Antarctic Gondwana sequence to an extensional tectonic regime associated with flood basalts and Gondwana break-up.