Turbidite fans in Upper Cretaceous Pierre Shale, Eagle Basin, Colorado: a new reservoir facies
Two fans intercalate with the Upper Cretaceous Pierre Shale and form cliffs over more than 10 mi (16 km) of continuous outcrop in the Eagle basin, north of Walcott, Colorado. Both units exhibit progradational sequences typical of turbidite fans. A common vertical succession of sedimentary structures consists of starved ripples, flat-bottomed ripple beds, thin flat beds grading into ripples of climbing ripples, and amalgamated flat beds. Massive to graded beds are rare and occur only in the upper part of each sandstone body. Associated sedimentary features include parting lineation, grooves, prod marks, mud chips, contorted bedding, and flute casts. Broad, low-relief channels occur at the top of the lower, more well-developed sequence. The sedimentary structures described correlate well with accepted models for turbidite-fan sedimentation. Alternative interpretations of these laterally continuous, progradational sandstone bodies might include deposition in a distal shoreface or offshore bar environment. Hummocky cross-stratification and large-scale cross-stratified bed forms are not common in the sequence, as would be expected in a shoreface or marine-bar environment. Turbidite-fan deposits similar to those studied could be economically significant because of their extreme lateral continuity, updip seals, intercalation with hydrocarbon source rock, and possible overpressuring. The presence of submarine fans within the Cretaceous Western Interior seaway may increase significantly the hydrocarbon potential of previously unexplored, shaly portions of the basin.
- Research Organization:
- Reservoirs, Inc., Denver, CO
- OSTI ID:
- 6326068
- Report Number(s):
- CONF-8304200-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 67:3; Conference: Annual AAPG/SEPM/EMD/DPA convention, Dallas, TX, USA, 17 Apr 1983
- Country of Publication:
- United States
- Language:
- English
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