--> ABSTRACT: A Basinward-Thickening Condensed Section, the Heebner Shale Member of Oread Formation (Virgilian), Southeastern Kansas and Northeastern Oklahoma, by Wan Yang, Michael Bruemmer, Monica Turner-Williams, and Abdelmajid Jalal; #90906(2001)

Datapages, Inc.Print this page

Wan Yang1, Michael Bruemmer1, Monica Turner-Williams1, Abdelmajid Jalal1

(1) Wichita State University, Wichita, KS

ABSTRACT: A Basinward-Thickening Condensed Section, the Heebner Shale Member of Oread Formation (Virgilian), Southeastern Kansas and Northeastern Oklahoma

The widespread Heebner Shale of the Pennsylvanian Oread Cyclothem was deposited on the inland Kansas shelf and adjacent basins in a paleoequatorial belt during a maximum marine flooding. It overlies persistent and thin (~50 cm) transgressive Leavenworth Limestone and underlies persistent but variably thick (1-8 m) regressive Plattsmouth Limestone on 30 measured sections in a 100x20 km2 area in southeastern Kansas and northeast Oklahoma. On the shelf, the Heebner is thin (1-3 m) and dominantly black with abundant phosphatic nodules, indicating anoxic conditions. At the shelf margin and slope to the south, however, the Heebner thickens abruptly to ~10 m and consists of green, moderately fossiliferous shale and silty shale, indicating aerobic to dysaerobic conditions. Preliminary interpretation suggests that sediment source and dispersal pattern, oceanic circulation, eustasy, and depositional topography combined to cause the basinward changes of the Heebner Shale. The basinward thickening, which differs from the basinward-thinning trend of the passive-margin sequence stratigraphic model, was caused by prodeltaic progradation across the filled Arkoma Basin, suggesting an episode of deltaic progradation during maximum flooding. Shelf anoxia was probably caused by stagnant circulation induced by freshwater atop dense oceanic water on the shelf because of the large freshwater influx in the doldrums. In contrast, aerobic/dysaerobic conditions at the shelf margin and slope were caused by intensified oceanic circulation related to large influx of prodeltaic sediments and river runoff.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado