Depositional environments and paragenetic porosity controls, upper Red River Formation, North Dakota
The upper Red River Formation in North Dakota comprises a subtidal/intertidal facies overlain by three evaporitic sequences of four lithologic units each. Four porosity zones are recognized in the upper Red River: the subtidal/intertidal facies forms one porosity zone, and each evaporitic sequence contains another. Each unit in a sequence is thinner and less widespread than its preceding counterpart. All strata are laterally continuous across the main part of the Williston basin in North Dakota, but the porosity zones eventually disappear to the east as they approach the basin margin. Porosity within any given zone varies from one part of the basin to another, often within relatively short distances. The D porosity zone consists of two primary lithologic facies: a shallow subtidal burrowed mudstone and skeletal wackestone, and an impermeable, often laminated, black organic skeletal wackestone and packstone deposited in an intertidal or supratidal barred pond environment. Porosity in the subtidal burrowed facies is due to syndepositional dolomitization and later calcite solution and microfracturing. Maximum porosity values related to dolomitization and calcite dissolution occur in the burrowed horizons immediately above the impermeable organic units, which acted as barriers to interstitial fluid movement. The basal unit of each of the sequences overlying the D zone consists of open shelf bioturbated skeletal wackestone of characteristically low porosity. Porous, fine-grained primary supratidal dolomite overlies the subtidal facies, and these units form the C, B, and A porosity zones. A very thin argillaceous marker bed of non-calcareous shale completes each sequence. Porosity in the upper three zones varies across the basin and is directly related to degree of exposure of the sediment in the supratidal environment, during which dolomitization occurred.
- OSTI ID:
- 5287217
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580100* -- Geology & Hydrology-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
CARBON COMPOUNDS
CARBONATE ROCKS
CARBONATES
DOLOMITE
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGICAL SURVEYS
GEOLOGY
LIMESTONE
LITHOLOGY
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERALS
NORTH AMERICA
NORTH DAKOTA
ORDOVICIAN PERIOD
OXYGEN COMPOUNDS
PALEOZOIC ERA
POROSITY
RESERVOIR ROCK
ROCKS
ROCKY MOUNTAIN REGION
SEDIMENTARY ROCKS
STRATIGRAPHY
SURVEYS
USA