High-frequency sequence stratigraphy of a mixed siliciclastic–carbonate system: the Pennsylvanian Strawn Group, eastern shelf of the Permian Basin, Texas

Mixed siliciclastic–carbonate systems are inherently complex from bed to basin scale because of inherent vertical and lateral lithologic variability driven by in situ carbonate production and extrabasinal siliciclastic sediment influx. The Middle to Upper Pennsylvanian Strawn Group is a major conventional hydrocarbon exploration target in the Permian Basin, Texas. Despite its economic importance, a thorough understanding of facies variability for prediction and stratigraphic correlation across different parts of the basin remains limited due to its highly complex stratigraphic architecture. This complexity reflects its mixed siliciclastic–carbonate character and cyclic deposition driven by multiple autogenic (local basin configuration, carbonate buildups, and deltaic input) and allogenic (tectonic subsidence, high-frequency glacioeustasy, and hinterland sediment supply) controls. We integrate core data, well-log correlations, and biostratigraphy to characterize the upper Strawn Group on the northern part of the Eastern Shelf of the Permian Basin in north-central Texas. A sequence-stratigraphic framework is applied to an area comprising a structurally controlled deltaic system (Haskell delta–Knox-Baylor trough) adjacent to an uplift-hosted carbonate buildup (Red River uplift). The objective is to determine how high-frequency sequences are expressed across distinct strike- and dip-oriented depositional domains, including their bounding surfaces, stacking patterns, and thickness variations. This approach further allows evaluation of how autogenic and allogenic processes are recorded within this mixed siliciclastic–carbonate system and provides insight into the spatio-temporal nature of siliciclastic–carbonate mixing within a sequence-stratigraphic framework. Characterization of the Strawn Group in north-central Texas demonstrates key elements for defining high-frequency depositional sequences and for correlating them between siliciclastic-dominated and carbonate-dominated domains. These results are applicable to other complex areas of the Permian Basin and to mixed siliciclastic–carbonate systems elsewhere in which stratigraphic architecture is governed by high-frequency cyclicity and complex basin configuration.