Genetic sequence relationships of Winnipegosis platform carbonates, Southern Elk Point basin, North Dakota

Conference · Fri Jul 01 04:00:00 EDT 1988 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:6126401

Shanley, K W; Cross, T A

Examination of cores and well-log data from the Winnipegosis Formation (Givetian) within a study area of approximately 11,500 mi/sup 2/ (30,000 km/sup 2/) in northern North Dakota allows recognition of seven time-stratigraphic progradational units within the Winnipegosis Formation. Together with the underlying Ashern Formation, these units are arranged in landward-stepping, vertical stacking, and seaward-stepping geometric patterns, which reflect changes in relative sea level. Abrupt juxtaposition of shallow over deeper water lithologies, evidence for subaerial exposure, and onlap geometries further suggest that these progradational units form two larger Vail-type sequences separated by regionally persistent unconformities or their correlative conformities. Sea level rise during the early Eifelian caused southeastward onlap of the Ashern Formation onto Middle Silurian carbonates of the Interlake Formation. Maximum flooding, expressed by deepest marine facies and a hardground surface, suggests the existence of a condensed section at the top of the Ashern Formation. This section was developed during the maximum rate of sea level rise. A decrease in the rate of sea level rise resulted in aggradation of lower Winnipegosis units on a gently dipping ramp. These units are presented by nodular and burrowed open-marine limestones with scattered stromatoporoid patch reefs and grainstone shoals. During the subsequent sea level fall, represented by Temple units, a shelf margin with pronounced depositional topography and adjacent starved basin were developed. Temple strata include coral-brachiopod-stromatoporoid reefs and productive fore-reef talus deposits along the shelf-margin rim. With increased rates of sea level fall, the platform interior and shelf margin were subaerially exposed, slope carbonates were dolomitized, and the E-shale was deposited as a lowstand wedge.

• Research Organization: Colorado School of Mines, Golden (USA)
• OSTI ID: 6126401
• Report Number(s): CONF-8808223-
• Conference Information: Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 72:7
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGY
MINERAL RESOURCES
NORTH AMERICA
NORTH DAKOTA
PALEOZOIC ERA
PETROLEUM DEPOSITS
RESERVOIR ROCK
RESOURCES
SILURIAN PERIOD
STRATIGRAPHY
USA