--> Abstract: Climate Controlled Gravity-Flow Deposits In The Eolian New Mountain Sandstone (Devonian), Antarctica, by M. C. Wizevich; #90928 (1999).

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WIZEVICH, MICHAEL C.
Department of Physical Sciences, Kutztown University, Kutztown, PA

Abstract: Climate Controlled Gravity-Flow Deposits in the Eolian New Mountain Sandstone (Devonian), Antarctica

The 228 m thick New Mountain Sandstone at Table Mountain (South Victoria Land) consists of lower and upper subunits deposited in a mixed eolian and fluvial system, and a middle subunit deposited in an eolian dune field.

The middle subunit contains large-scale transverse eolian dune (cross beds up to 9 m thick) and wet (massive sandstones, ripple marks, and thin mudstones) and dry (wind ripple laminae, and deflation scour) interdune deposits. Massive sandstones occur as both meter-scale, channel-based beds within the cross beds, and as lenticular- to tabular-shaped beds. Channels rarely contain vague cross beds and angular blocks of wind-ripple foresets; margins are commonly near vertical to slightly undercut. Tabular-shaped beds dominate interdune sequences up to 12 m thick, and extend laterally for several 100's of meters before interfingering with large-scale cross beds. Many tabular beds have thin mudstone caps, some containing flame structures or desiccation cracks. Massive beds are interpreted as sediment gravity-flow deposits derived from slipfaces of large-scale dunes and emplaced in interdune ponds. Gravity-flow deposits were generated from failure of the dunes (brecciation, slumping, and liquefied flows) during catastrophic rainfall events.

Two scales of climatic control on deposition are recognized. Interbedded wet and dry interdune deposits indicate that rainfall events were ephemeral, and the interdune areas only at times (seasonal?) flooded. During storms interdune ponds filled with deposits generated from the mass-wasting of the dunes. During and periods, ponds dried and eolian processes dominated. Thick sequences of tabular massive beds represent periods of large-scale degradation of transverse dunes, part of a longer term (glacial/interglacial?) climatic cycle.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas