174-3 Paleogeographic Controls on Carbonate Factory Recovery After Oceanic Anoxic Events: A Texas-Sized Window into Patterns of Reestablishment Following OAE1a

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

Presenting Author:

Kelly Hattori

Author:

Hattori, Kelly E.¹

Abstract:

The greenhouse climate of the Cretaceous, overall characterized by deglaciation, long, slow sea level oscillations, and a generally warm, stable climate, is an ideal background for evaluating the short and long-term effects of event-based perturbations such as massive volcanism and bolide impacts. The Cretaceous is particularly well known for a series of oceanic anoxic events (OAEs), each of which has been found to have different drivers and variable impacts on Earth systems, most especially the marine realm. OAE1a (Early Aptian), which resulted from massive large igneous province volcanism and led to deposition of distinctive black shales globally, had a profound effect on the productivity and health of carbonate factories at a global scale, driving nearly complete carbonate platform shutdown across the tropical Tethys. Numerous studies have documented sedimentation changes within the OAE interval, but fewer have investigated the record of shallow-shelf carbonate factory recovery following the event. This study provides a sedimentological perspective on the recovery of key carbonate fauna on the giant Comanche Platform of Texas following OAE1a, highlighting in particular the role of preexisting paleogeographic features in stepwise carbonate factory recovery. The Cow Creek (outcrop) or James (subsurface) Limestone of the Pearsall Formation preserves a record of early stages of carbonate factory reestablishment and recovery across the northern Gulf Coast in Texas. Carbonate factory “recovery” is illustrated by a slow increase in carbonate sedimentation accompanied by faunal diversification. A review of multiple locales across Texas and the broader Gulf Coast reveals that recovery following OAE1a varied spatially and temporally. In Texas, most regions did not achieve full carbonate factory recovery (e.g., diverse fauna, photozoans, robust sedimentation rate) during deposition of the Cow Creek; instead, nearshore to mid-shelf reestablishment communities were dominantly composed of eutrophic faunas (e.g., oysters and algae) that would have flourished in high-turbidity nearshore waters affected by accelerated weathering cycles. However, in some select regions a diverse productive photozoan fauna (e.g., coral and rudist reefs) was successfully established. These communities are observed in the mid-shelf realm on topographic highs (e.g., salt domes, arches, fault blocks), suggesting that oceanic conditions were optimal for carbonate reestablishment in the shallow-water realm of the mid-shelf, while the deeper seafloor of the mid-shelf extending up into nearshore inner shelf environments remained unsuitable for full carbonate recovery.

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

doi: 10.1130/abs/2025AM-4646

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