--> Abstract: Significance of Estuarine Valleys in the Cores of Clastic Wedges: Ericson Formation, Wyoming, by Carolina A. Gomez and Ron Steel; #90039 (2005)

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Significance of Estuarine Valleys in the Cores of Clastic Wedges: Ericson Formation, Wyoming

Carolina A. Gomez and Ron Steel
University of Texas at Austin, Austin, TX

The Ericson Formation in southwestern Wyoming has conventionally been considered the fluvial core of a thick, marine-fringed clastic wedge that built out from Fold-and-Thrust uplands to the west and north into the late Campanian Western Interior Seaway. The recent discovery of numerous tidally-influenced valleys in the Ericson, both in the Rusty (Martinsen et al., 1999) and in the Trail members evidences (1) the great magnitude of regressive and transgressive transits of deltas/strandplains and estuaries and (2) the additional significant upstream penetration of tidal effects in the Ericson rivers, during clastic wedge construction. The landward ends of the impinging estuaries are being characterized in detail. They are of modest size (few kilometers long and between 15 and 35 meters thick), sometimes contain lowstand fluvial carpets and bayhead deltas, are otherwise dominated by tidal dunes and composite dunes in channels of flood- and/or ebb-tide origin. They appear to have been developed in relatively fresh water, and are capped by intertidal/supratidal deposits.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005