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ABSTRACT: Tectonically Controlled Sedimentation in the Mesozoic Basins of the Antarctic Peninsula

David I. M. MacDonald, Peter J. Butterworth

The Antarctica Peninsula (AP) lies on a medium-size block of continental crust and is one of a mosaic of west Antarctica crustal blocks that underwent a complex tectonic evolution during Gondwana breakup. The peninsula represents the eroded roots of a microcontinental volcanic arc; this arc lay above the easterly subducting proto-Pacific plate, and was active throughout the Mesozoic.

The exposed Mesozoic basins display a complex stratigraphy, reflecting local tectonic and volcanic events. There are a few general trends. Almost all basins are post-late Oxfordian, their fill is entirely clastic, and is largely derived from the Antarctica peninsula volcanic arc. Most basins were affected by a period of arc expansion in the latest Jurassic or earliest Cretaceou, which manifests itself as inputs of lava or coarse volcaniclastic sediment overlying mudstones with an open marine fauna. Barriasian and older mudstones are generally finer grained and darker than mudstones from post-Berriasian strata. However, it must be emphasized that these are only general trends. Deformation is variable, commonly progressive. No lithostratigraphic units can be correlated between any two b sins, nor are there any interregional unconformities. No matching is possible with basins of equivalent age in formerly contiguous areas of Gondwana.

There is evidence that some global eustatic events are recorded in the sedimentary records of at least two of the AP Mesozoic basins, but these have effect only in periods of local tectonic quiescence. The dominant control on sedimentation in this large segment of the Pacific rim was arc tectonics.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990