Stratigraphy of Jurassic pyroclastic rocks in the Transantarctic Mountains

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 2 40 m of silicic tuffs, tuffaceous sandstones, and subordinate quartzose san dstones of probable Early Jurassic age. It is overlain by basaltic pyroclas tic rocks of the Prebble Formation. Similar basaltic rocks also crop out in Victoria Land and constitute the Mawson and Exposure Hill Formations. Thes e basaltic pyroclastic rocks and the overlying Kirkpatrick Basalt lavas are Middle Jurassic. The pyroclastic rocks comprise thick tuff-breccias with m inor lapilli-tuffs and tuffs; sequences are as much as 400 m thick. These s ilicic and basaltic pyroclastic rocks record the transition from foreland b asin fluvial sedimentation of the Antarctic Gondwana sequence to an extensi onal tectonic regime associated with flood basalts and Gondwana break-up. ( C) 2000 Elsevier Science Limited. All rights reserved.