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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 5. (May)

First Page: 846

Last Page: 846

Title: Burial History of Upper Cretaceous and Tertiary Rocks Interpreted from Vitrinite Reflectance, Northern Green River Basin, Wyoming: ABSTRACT

Author(s): Warren W. Dickinson, B. E. Law

Article Type: Meeting abstract

Abstract:

The burial history of Upper Cretaceous and Tertiary rocks in the northern Green River basin is difficult to reconstruct for three reasons: (1) most of these rocks do not crop out, (2) there are few stratigraphic markers in the subsurface, and (3) regional uplift beginning during the Pliocene caused erosion that removed most upper Tertiary rocks. To understand better the burial and thermal history of the basin, published vitrinite reflectance (Ro) data from three wells were compared to TTI (time-temperature index) maturation units calculated from Lopatin reconstructions. For each well, burial reconstructions were made as follows. Maximum depth of burial was first estimated by stratigraphic and structural evidence and by extrapolation to a paleosurface intercept f Ro = 0.2%. This burial was completed by early Oligocene (35 Ma), after which there was no net deposition. The present geothermal gradient in each well was used because there is no geologic evidence for elevated paleotemperature gradients.

Using these reconstructions, calculated TTI units agreed with measured Ro values when minor adjustments were made to the estimated burial depths. Reconstructed maximum burials were deeper than present by 2,500-3,000 ft (762-914 m) in the Pacific Creek area, by 4,000-4,500 ft (1,219-1,372 m) in the Pinedale area, and by 0-1,000 ft (0-305 m) in the Merna area. However, at Pinedale, geologic evidence can only account for about 3,000 ft (914 m) of additional burial. This discrepancy is explained by isoreflectance lines, which parallel the Pinedale anticline and indicate that approximately 2,000 ft (610 m) of structural relief occurred after maximum burial. In other parts of the basin, isoreflectance lines also reveal significant structural deformation after maximum burial durin early Oligocene to early Pliocene time.

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Copyright 1997 American Association of Petroleum Geologists