Late Mesozoic sedimentation in the northern Antarctic Peninsula and its relationship to the southern Andes

Two distinct phases of island-are evolution are recognized in late Mesozoic sedimentary rocks of the northern Antarctic Peninsula. During late Jurassic (Kimmeridgian-Tithonian) times, alternating radiolaria-rich mudstones and ash-fall tuffs were deposited under shallow marine euxinic conditions in association with restricted volcanic centres. The name Nordenskjöld Formation is proposed for this lithostratigraphic unit. Subsequently, during the early Cretaceous, a major episode of volcanism and uplift led to the construction of an emergent are-terrane. Simultaneous development of a retro-arc basin resulted in the accumulation of coarse volcaniclastic detritus along the eastern side of the arc. Retro-are sedimentation and intermittent volcanism continued into the late Cretaceous and early Tertiary. Although the pattern of sedimentation in the northern Antarctic Peninsula is broadly comparable to that of the southern Andes, an active marginal basin has not been recognized in the former area. Interbedded mudstones and tuffs, identical to those of the Nordenskjöld Formation, were deposited in the southern Andes and South Georgia during the late Jurassic - early Cretaceous.