Evolution of a Tethyan carbonate platform through the Jurassic tectonic and climatic upheavals

This study aims to quantify the response of carbonate producers to eustasy, tectonics and climate changes in intracontinental basins. We examined Middle to Late Jurassic carbonate systems (Aalenian to Oxfordian, c. 175 to 155 Ma) of the northern Aquitaine Basin (France). The detailed description of 67 outcrops and the large-scale correlation of 21 transgressive-regressive cycles allows for reconstruction of various evolving depositional environments. A westward dipping carbonate ramp developed from the Aalenian to Early Oxfordian, replaced by a rimmed-platform during the Middle to Late Oxfordian. Accommodation space indicates long wavelength flexures, locally disrupted by normal fault activity, that could relate to the extension of the western Tethys margin or the opening of the North Atlantic Ocean. The Aalenian and Callovian to Early Oxfordian display low carbonate accumulation rates (≈ 10 m Myr−1) that result from (1) limited accommodation space during the Aalenian, possibly caused by the “Mid Cimmerian” uplift, and (2) the development of a wet climate during the Callovian to Early Oxfordian, which enhanced continental weathering and siliciclastic input. The Late Bajocian, Bathonian and Middle to Late Oxfordian are stages of high neritic carbonate production, ranging from 25 to 70 m Myr−1 on the shallow platform. The thriving of ooid, photozoan and ‘Micrite and Microbial’ (M)-factories was favored by a dry climate disturbed by short episodes of intense precipitation in the Tethyan realm, leading to oligo-mesotrophic waters and calcium carbonate supersaturation. The M-factory flourished in lagoons throughout the Middle Jurassic and Oxfordian, independent of climate and tectonic upheavals.