Palynological analysis of the upper Strawn Group on the Eastern Shelf of the Permian Basin, Katz Field, Stonewall County, Texas, USA

The Pennsylvanian Strawn Group on the Eastern Shelf of the Permian Basin is a regionally important mixed siliciclastic–carbonate succession that hosts diverse hydrocarbon reservoirs. However, the evolution of its depositional systems and internal stratigraphic architectures is only recently becoming better understood. Despite its considerable economic value and the importance of accurate stratigraphic correlations across the Eastern Shelf, palynological studies of the Strawn Group remain limited. In fact, the economically significant upper Strawn interval has not previously been analyzed using dedicated palynological or palynofacies methods. To partially address this, we sampled the Phillips Petroleum CB Long C-16 core from the Katz Field in Stonewall County, Texas, USA, which contains the upper Strawn deposits. Twenty-three core samples were palynologically studied, revealing a low-diversity assemblage of 12 sporomorph taxa. The presence of Camptotriletes certus likely limits the stratigraphic age to Desmoinesian, aligning with established chronostratigraphic frameworks for the Eastern Shelf. Quantitative palynofacies analysis, based on 200 palynomorph counts per sample, indicates a systematic upward transition through the section from a lower interval dominated by amorphous marine organic matter (AMOM), reflecting offshore-to-distal delta-front depositional environments, to an upper interval rich in phytoclasts, consistent with a shallowing-upward succession through higher-energy delta-front-to-shoreface and tidal-shelf depositional environments, recording a basinward deltaic progradation across the Eastern Shelf. These findings offer new biostratigraphic and paleoenvironmental insights into the regional stratigraphic framework of the upper Strawn Formation on the Eastern Shelf.