77 Paleontology IV - Environmental Controls on Ecology and Evolution

Monday, 1 November 2010
8:00 AM - 12:00 PM
Room 605

PALYNOLOGY OF THE PENNSYLVANIAN-PERMIAN TRANSITION, WOOD SIDING (VIRGILIAN) TO WELLINGTON (LEONARDIAN) FORMATIONS, IN NORTH-CENTRAL OKLAHOMA

Paper number: 77-12
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Abstract

At the coarsest scales, Pennsylvanian vegetation was characterized by spore-producing plants, e.g., lycopsids, horsetails, and ferns, and was replaced by a Permian vegetation characterized by seed plants, particularly conifers and “seed ferns.” Likewise, conventional wisdom avers that the climate changed from wet in the Pennsylvanian, evidenced by coals, to arid in the Permian, evidenced by red beds and evaporites. However, research in Texas has demonstrated that this dichotomy obscures an oscillatory transition in climate and vegetation in south-central North America.

The palynology of five correlated cores­–92 samples taken from 397 meters of composite section–spanning the latest Pennsylvanian through the Early Permian from Kay and adjacent Osage Counties in north-central Oklahoma is discussed in this preliminary study. With a conodont-defined Pennsylvanian-Permian boundary at the base of the Bennett Shale (Red Eagle Limestone), 10 productive samples were studied from the upper Wabaunsee and lower Council Grove groups (upper Virgilian); 18, from upper Council Grove and Chase groups (Wolfcampian); and 25, from the lower Sumner Group (Leonardian). Overall, spores dominate Pennsylvanian samples, while pollen dominate Permian samples. Striate bisaccates are present in Pennsylvanian samples, but rare and of low diversity. The diversity and abundance of bisaccate and striate pollen grains increases from the Council Grove Group to Sumner Group.

In accord with prior investigations in Kansas, no sharp discontinuity in palynological assemblages is apparent at the boundary. However, as documented in Texas megafloras, the palynological transition suggests that the transition from a persistent wet climate to a persistent dry climate passed through a phase of oscillation. Although our sampling is limited, it is notable that striate pollen are common in the Johnson Shale, which immediately underlies the Red Eagle Limestone (=Pennsylvanian-Permian boundary) and which contains the stratigraphically lowest “red bed” paleosol in this composite section. Above the Red Eagle Limestone and overlying red shale interval (Roca Shale), spores briefly increase in abundance in a mudstone within the Grenola Formation before bisaccates and striate pollen continue their expansion.