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Mutti, Emiliano1, Roberto Tinterri1 
(1) Parma University, Parma, Italy 

ABSTRACT: Cross-Stratified Sandstones and Multiple Beds: Evidence of Internal Flow Divergence in Turbidity Currents Caused by Submarine Topography

Careful analysis of several exposed turbidite systems deposited in tectonically active settings indicates that wherever turbidity currents experience deflections and reflections caused by gentle bounding slopes flow stripping occurs resulting in divergence between the path of the denser part of the current and that of the more dilute one. As a result, very distinctive facies types are generated by this process, ranging from coarse-grained and internally-stratified sandstone beds to stacked thinning-upward sandstone-mudstone couplets deposited by the same flow upon flow separation. The sediments related to topography-induced flow separation display a variety of intergradational features mostly related to the original flow characteristics at the point where separation occurs and the type of submarine relief encountered. 
In this paper we discuss in detail some specific examples emphasizing in particular the importance of coarse-grained thin sandstone beds associated with the cross-current transition between massive sandstone facies deposited by dense flows and thinly bedded fine sandstones and mudstones deposited by turbulent flows. Settings of this type can be easily mistaken for channel-levee deposits. Criteria for the correct interpretation are discussed.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.