66-5 CARBONATE STABILITY UNDER STRESS: ENVIRONMENTAL CONTROLS ON THE SOUTHEASTERN ARABIAN PLATFORM DURING OAE1A

Session: Environmental Instability During Greenhouse Periods: Impact on Terrestrial and Marine Ecosystems (Posters)

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The Early Cretaceous Oceanic Anoxic Event 1a (OAE1a) was a major paleoceanographic crisis driven by volcanic activity associated with the Ontong Java Plateau in the Pacific. This event led to elevated atmospheric pCO₂, disruptions in the global carbon cycle, ocean acidification, and widespread ecological stress. The thick carbonate successions of the Kahmah Group in Oman, part of the Arabian Platform, provide a well-exposed and continuous record of OAE1a, offering critical insights into how equatorial shallow marine carbonate platforms responded to this global perturbation. This study examines the resilience of Oman’s carbonate ecosystems during OAE1a, with the central hypothesis that the region’s arid climate and low nutrient influx enabled sustained carbonate production despite widespread environmental stress. Our focus is a ~220 m-thick stratigraphic section at Wadi Muaydin, where previous research suggests a partial record of OAE1a is preserved. Methodologies include petrographic microfacies analysis following Dunham’s classification, stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope geochemistry to assess diagenetic alteration and support chemostratigraphic correlation with global reference sections, and X-ray fluorescence (XRF) analysis to evaluate geochemical proxies related to paleo-productivity. Preliminary interpretations suggest that limited terrigenous input and minimal nutrient enrichment during OAE1a favored a shift in facies within the Upper Kharaib Formation—from rudist- and coral-dominated assemblages to Lithocodium-Bacinella-rich facies, characterized by wackestone to packstone textures. In contrast, the overlying Shu’aiba Formation is marked by a return to miliolid- and rudist-rich deposits with grainstone to rudstone facies, with no field evidence for increased detrital influx. These observations suggest ecological adaptation and sustained platform productivity, highlighting the resilience of this carbonate system during a time of global environmental upheaval.

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

doi: 10.1130/abs/2025AM-11166

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