174-4 Evaluation of ecological changes in carbonate platforms during the early Aptian

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

Presenting Author:

Alexis Godet

Authors:

Godet, Alexis¹, Sharpe, Justin², Glore, Ross Alexander³, Suarez, Marina B.⁴, Adatte, Thierry⁵, Frijia, Gianluca⁶, Morsilli, Michele⁷

Abstract:

During the Early Cretaceous a warmer climate and the configuration of continental landmasses allowed the development of large carbonate platforms. Because of their sensitivity to environmental conditions, these carbonate-producing ecosystems recorded perturbations in seawater temperature and chemistry at different scales. During the early Aptian, the Oceanic Anoxic Event (OAE) 1a unfolded as a result from submarine volcanism in the Pacific and increased greenhouse conditions. This major paleoceanographic event triggered the drowning of some carbonate platforms while others evolved toward ecological associations more adapted to changing paleoenvironmental conditions. Previous studies and unpublished data suggest that the largest amount of ecological changes occurred at higher paleolatitude where a more humid climate facilitated the transfer of nutrients and detrital particles into shallow seas; this deterioration in the environment pushed ecosystems to adapt. We tested this hypothesis in two regions of France (Vercors and Corbières) and two regions of Italy (Apennines and Gargano Promontory) that aligned along a latitudinal transect during the Aptian. At higher latitude (Vercors), rudist- and coral-bearing ecosystems collapsed in the wake of the OAE1a because of enhanced nutrient and detrital input, and pre-OAE1a fossil associations did not reappear. Point counting analysis data highlight a drop in ecosystem biodiversity of up to 46%. At mid latitude (Corbières), rudists, corals, and benthic foraminifera characterized the ecosystems prior to the OAE1a. They are replaced by marls where large benthic foraminifera and oysters make up a poorly diverse ecosystem during the OAE1a, and where geochemical data indicate high nutrient and detrital input. After the OAE1a, rudists and corals reappear as more oligotrophic paleoenvironmental conditions resumed. On the other hand, carbonate deposits in Italy, show a dominance of facies with the bivalve Chondrodonta directly prior to and during the OAE1a reflecting stressful conditions; yet carbonate production was maintained as paleoenvironmental conditions did not experience major shifts. Thus, our data confirm that the intensity of paleoenvironmental changes decreased toward lower latitude and that lower paleoenvironmental stress favored the resilience of carbonate ecosystems and their biodiversity.

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

doi: 10.1130/abs/2025AM-8717

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