Organic facies of some Mesozoic source rocks on Alaskan North Slope
Geochemical screening (TOC and Rock-Eval pyrolysis) of picked cuttings of Mesozoic age from seven wells located between Prudhoe Bay and the Colville delta distinguished three types of organic facies and one subtype. This paper demonstrates relationships between organic facies of the sediments and their inferred depositional environment. The organic matter type and quantity serve to separate the Mesozoic stratigraphy into five intervals: (a) Shublik Formation; (b) basal Kingak Shale; (c) upper Kingak Shale; (d) Pebble Shale/Hot Zone; and (e) Torok/Seabee Formation. The Shublik Formation in the study area was deposited on a carbonate platform with a deep basin lying to the south. High organic-carbon content and relatively high hydrogen content of the Shublik can be explained by preservation of marine organic matter in anoxic lagoons or local depressions. Deposition of the basal Kingak Shale and of the Pebble Shale/Hot Zone is the result of major transgressions during the Jurassic and the Neocomain, respectively. Both intervals were deposited as bottomsets of prograding sequences (prodelta) and contain high quantities of relatively hydrogen-rich organic matter. The upper Kingak Shale and the Torok/Seabee Formations are of a similar organic facies that is characterized by relatively low quantities of hydrogen-poor organic matter. Both intervals were deposited as foresets in a progradational sequence. The organic facies of these intervals are the result of clastic dilution, increased input of terrigenous organic matter, and increased bioturbation during early burial.
- Research Organization:
- Mobil Exploration and Producing Services, Inc., Dallas, TX
- OSTI ID:
- 6183356
- Report Number(s):
- CONF-8304200-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 67:3; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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03 NATURAL GAS
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Geology
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ALASKA
ALASKAN NORTH SLOPE
CLASSIFICATION
DEPOSITION
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGY
MESOZOIC ERA
NORTH AMERICA
ORGANIC MATTER
SOURCE ROCKS
STRATIGRAPHY
USA