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. (
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