Environmental change on the eastern Arabian shelf during the early Aptian Oceanic Anoxic Event (OAE1a): A chemostratigraphic approach

The effect of the early Aptian Oceanic Anoxic Event (OAE1a) on the southern Tethyan carbonate sedimentation on the eastern Arabian shelf is investigated. Chemostratigraphic platform-to-basin correlation of published and new outcrop and well core data allows for a lateral and temporal investigation of the changes in the depositional environment and reassessing the paleoenvironmental impact of OAE1a. Our results demonstrate that sedimentation rates varied spatially, influenced primarily by accommodation space and sediment redistribution rather than by effects of global carbon-cycle perturbations on carbonate production. Contrary to previous hypotheses, geochemical proxies do not support widespread anoxia on the Arabian shelf; instead, intermittent oxygen depletion was limited to specific basinal settings. Likewise, with the stratigraphic resolution of this study, no evidence of ocean acidification was detected, challenging models linking global carbonate platform demise to ocean acidification. Facies analysis reveals that transgressive-regressive cycles played a dominant role in shaping carbonate deposition. The transition from rudist–coral to orbitolinid–Bacinella assemblages reflects sea-level changes rather than nutrient stress. The spatial variations of δ¹³C_carb indicate hydrodynamic isolation within the platform interior, affecting local carbon budgets. Sediment preservation rates align with other Tethyan carbonate platforms, reinforcing the role of sea-level fluctuations in controlling carbonate production and accumulation.