STRATIGRAPHY, SEDIMENTARY FACIES, AND PALYNOLOGY OF A TEMPORARY EXPOSURE OF THE SEMINOLE FORMATION (PENNSYLVANIAN, MISSOURIAN), TULSA CO., OKLAHOMA

Road construction along OK Highway 75 southwest of Tulsa provided an opportunity to study facies of the upper Seminole Formation that are usually poorly exposed in surface outcrop. The 10m succession includes evidence for tidally influenced deposition. The lower seven meters consist of heterolithic facies composed of unbioturbated mud-draped fine sandstone with pinstripe lamination and wavy to flaser bedding. These strata are organized into dm-scale alternations of shale-rich and shale-poor packages that may reflect seasonal variation in storm influence, as in the modern Changjiang Estuary of China (Fan and Li, 2002). The heterolithic facies likely records deposition in a tidally influenced interdistributary delta plain or, possibly, an estuary. The shales contain low diversity terrestrial palynomorph assemblages. The heterolithic facies is abruptly overlain by a 40cm interval of laminated mudstone and shale with organic-rich laminae that culminates in a thin (4cm) coal. The shale and mudstone include abundant plant remains and palynomorphs. This interval probably represents supratidal swamps with abundant tree ferns and medullosan seed plants, and an understory of diverse ferns. Monosaccate pollen (e.g., Florinites) increases in abundance near the coal. The coal is succeeded abruptly by dark-grey to black shale with a fauna of pyritized bivalves and lingulid brachipods that indicate a shift to marginal marine to brackish conditions. Terrestrial palynomorph diversity remains high and may even increase in these shales. The coal and overlying shale record a relative sea level rise and may be part of a transgressive systems tract (TST). If of estuarine origin, the underlying heterolithic facies is also part of the TST. The Checkerboard Limestone, a regional marker bed, caps the roadcut. About a meter thick, it is a condensed marine wackestone with brachiopod-rich rudstone horizons that reflect storm winnowing. The limestone records further transgression and sharp reduction in siliciclastic input. The top of the unit may represent a maximum flooding surface, and the overlying, poorly exposed marine shales of the Coffeyville Formation can be interpreted as highstand deposits. Coffeyville shale samples contain few terrestrial palynomorphs but abundant woody debris.