Fluvial‐aeolian interactions: Part II, ancient systems

Abstract

ABSTRACTAn understanding of fluvial‐aeolian deposition derived from modern case‐examples in a previous study is applied to the Permian Cutler Formation and Cedar Mesa Sandstone on the Colorado Plateau. These formations supply an excellent three‐dimensional exposure of intertonguing fluvial and aeolian strata. Four distinct facies associations form the bulk of the Cutler Formation and Cedar Mesa Sandstone: (1) aeolian dune deposits; (2) wet interdune deposits; (3) fluvial channel deposits; and (4) overbank‐interdune deposits. In addition, two distinctive types of erosion surfaces are found within the Cutler Formation and Cedar Mesa Sandstone: pebble‐ to granule‐rich erosion surfaces (aeolian deflation surfaces) and flood surfaces.Fluvial and aeolian intertonguing result in extensive tabular sheets of aeolian sandstone separated by flood surfaces and overbank‐interdune deposits. Fluvial channels are associated with the deposits overlying flood surfaces and are incised into the underlying aeolian sandstones. Overbank‐interdune deposits and wet interdune deposits cover flood surfaces and intertongue with overlying aeolian sandstones.The primary characteristics of ancient fluvial‐aeolian deposition are overbank‐interdune deposits and pronounced extensive erosion surfaces (flood surfaces), which are parallel to underlying fluvial sandstones and thus trend parallel to the palaeoslope and palaeohydrological gradient.