264-4 Understanding Controls on Organic Carbon Enrichment in Permian Deep-Marine Siltstones of the Delaware Basin: A Tribute to Brad Sageman

Abstract:

Organic carbon-rich siltstone (ORS) marker beds in the Permian Brushy Canyon and lower Cherry Canyon formations record organic carbon enrichment within a basin-restricted deep-marine system. This research integrates stratigraphic mapping of continuous shelf-to-basin exposures with geochemical proxy relationships to evaluate mechanisms controlling particulate organic carbon (POC) accumulation.

Organic carbon enrichment was driven chiefly by hydrodynamic concentration of POC within sediment gravity flows, rather than by suspension fallout in surface waters modulated by production, destruction, and dilution processes. Poor to negative correlations between POC and geochemical proxies for these processes, together with positive correlations between POC and the vertical and longitudinal interval thickness of ORS marker beds, indicate enrichment under high sedimentation rates and efficient burial. Across the 55-km exposure of the 450-m-thick deep-marine siliciclastic succession, 25 to 33 ORS marker beds mapped over 245 km² provide a stratigraphic framework for correlating organic enrichment trends across second- through fifth-order deepwater episodes.

Submarine canyons incised the carbonate shelf margin and directed sediment transport into down-profile fairway, interfairway, and extra-channel regions. Catastrophic floods generated hyperpycnal flows that delivered shelf-derived POC to the basin during sea-level rise, when external sand supply was low and shelf inorganic and organic carbon productivity was high. Slope enrichment reflects stripping from super-elevated flows, whereas channel-fairway enrichment supports a shelf-derived source. Together, these relationships indicate that sea level directly controlled sediment sources and indirectly controlled sediment flux by modulating flow initiation by flood or failure. More broadly, hyperpycnal sediment gravity flows provide a plausible mechanism for POC accumulation in onshore basins and where carbonate shelves source off-platform deep-marine settings.

Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026

doi: 10.1130/abs/2026AM-20578

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