Depositional architecture and sequence stratigraphy of the Mid-Cretaceous Dakota Formation, NE Utah--NW Colorado
- Univ. of Rochester, NY (United States). Dept. of Geological Sciences
The Albian-Cenomanian Dakota Formation in NE Utah and NW Colorado records the transition from nonmarine to marine deposition during mid-Cretaceous development of the Cordilleran foreland basin. The Dakota Formation unconformably overlies the Cretaceous Cedar Mountain Formation and is capped by the Cenomanian Mowry Shale Member of the Mancos Formation. Contained within the Dakota Formation are 15--35 meters of fluvial, tidal, and marine facies that were deposited in response to increased accommodation development. The base of the Dakota Formation consists of trough cross-stratified sandstone and chert pebble conglomerate representing braided fluvial deposition filling valleys cut as much as 15 meters into the underlying Cedar Mountain Formation. Overbank mudstones are laterally associated with these fluvial facies. In the upper portions of the valley fills, decreased fluvial gradient resulted in development of laterally discontinuous channels and increased overbank deposition. Overlying these sediments are braided fluvial facies indicating a rejuvenation of fluvial gradient. The upper portions of these facies show tidal influences on fluvial deposition. At some localities these tidal facies are overlain by shoreface sandstone. The sequence is capped by a thin chert pebble lag which represents a marine flooding surface, and is overlain by the Mowry Member. Deposition of Dakota Formation facies represents a transgressive systems tract going from lowstand conditions and valley incision at the base, to deposition of fluvial, tidal, and marine facies during rising base-level conditions. This overall rise is marked by slight drops in relative base-level resulting in minor rejuvenation of Dakota fluvial facies. The increased accommodation development that allowed Dakota Formation deposition resulted from combined increase in eustatic sea-level and basin subsidence.
- OSTI ID:
- 5436546
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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