222-4 Swamps, shorelines, and sea level: Redefining coal facies models for a dynamic coastal system

Session: Delta Evolution from Rivers to the Shelf: Past, Present and Future Perspectives for Society (Posters)

Presenting Author:

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Abstract:

During the Cretaceous the Western Interior Seaway divided North America, with coastlines stretching from the Artic in the north, to Mexico in the south. Extensive peat-forming coastal swamps formed along the margins of the Seaway during the Late Cretaceous, which were particularly productive on the western margin. The Straight Cliffs Formation, which outcrops on the Kaiparowits Plateau in southern Utah, preserves one of the final episodes of marine deposition along the Western Seaway margin before the seaway closed. Within this formation the Coniacian-Santonian aged John Henry Member consists of a succession of shoreface, lagoon, swamp, and fluvial deposits, and is the primary coal-bearing unit.

Clastic shoreface deposits and economic potential of the coals of the John Henry Member have been well studied, however the broader depositional context of the coals and their relationship to shoreline processes and sea-level changes remains less well understood. This project aims to correlate coals of the John Henry Member with coeval paleoshoreline systems, to better understand peat-forming environments along the Western Interior Seaway during the Late Cretaceous. By integrating outcrop, core, and well log data, we examine the stratigraphic architecture of the John Henry Member across the Kaiparowits Plateau. Ultimately this work will improve understanding of the relationship between peat accumulation and dynamic coastal conditions, and contribute to broader understanding of the stratigraphy of coal-forming environments in the geologic record.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7464

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