PRELIMINARY SURVEY OF WELLINGTON FORMATION (PERMIAN, OKLAHOMA) PALEOBOTANY

In Oklahoma, the Permian Period (299-251 million years ago) is stereotyped as represented by widespread, thick red beds—red mudstones, siltstones, and sandstones—taken as evidence of equally widespread warmth and aridity. Among these red beds are evaporites—dolomites, gypsums, and salts—also indicative of aridity. However, the earliest Permian in Oklahoma is represented by marine limestones and shales. The Wellington Formation (lower Sumner Group, Leonardian) records the transition from persistently wet to intermittently dry climates in Oklahoma with the first appearance of red beds and evaporites. Permian strata (globally) preserve the shift in terrestrial ecosystems from domination by spore-producing plants (e.g., ferns, lycopsids, etc.) to domination by seed plants (e.g., conifers, cycads, etc.).

This study begins the examination of the vegetational response in Oklahoma to the onset of arid conditions by investigating the paleobotany of the Wellington Formation. The Wellington Formation crops out in central Oklahoma (and Kansas) and is famous for the insects preserved in dolomites (Elmo and Midco Beds). It is up to 250m thick in north-central Oklahoma and contains red/green/gray shales, sandstone lenses, and thin dolomite beds. In the subsurface in western Oklahoma, it attains a thickness of over 400m and also contains halite and gypsum (as anhydrite) beds that are especially common and thick near its base.

Paleobotanical surveys record a variety of palynofloral and macrofloral assemblages throughout the outcrop area. The palynofloral assemblages have been recovered from sediments representing wet habitats (dark gray shales) to drier habitats (light gray shales). The palynofloras reflect this heterogeneity in the observed abundance of spores versus pollen, but are usually dominated by bisaccate gymnospermous pollen types (probably coniferous) regardless. Many of the pollen types are striate/taeniate and suggestive of arid-adapted taxa. Macrofloras are typically restricted to fluvial deposits and contain a preponderance of peltasperms (including gigantopterids), with individual bedding planes dominated by taeniopterids or walchian conifers. Highly localized deposited are dominated by cordaites.