Mapping and geochemical characterization of the Toarcian organic matter in the Mediterranean Tethys and Middle East

Abstract

Organic matter from Toarcian outcrops and boreholes in several basins around the Mediterranean Sea and Middle East has been studied. Rock-Eval pyrolysis, elemental analyses of kerogens and gas chromatography of chloroform extracts within these different basins have been used to determine the amount, petroleum potential and type of the organic matter. The results have been used to compile a mapping of the organic matter for the Toarcian stage, which shows heterogeneities in the distribution and type of organic matter: 1. (1) Marine organic matter (type II) occurs in different environments of deposition. Whereas high contents (>5% total organic carbon) correspond to thick deposits within the West European realm (Great Britain, North Sea, Paris Basin and Germany), the organic matter is less abundant in the Mediterranean area where lower concentrations (1–2% TOC), preserved in Lower Toarcian thin levels, are limited only to restricted basins (northern Italy, Greece). 2. (2) The predominance of continental organic matter (type III) along the northern margin of the Tethys corresponds to a deltaic environment. 3. (3) There is a predominance of altered organic matter within the carbonated platforms around the Mediterranean Tethys. These results, supplemented with the data issuing from the literature, add a geochemical dimension to the paleogeography of the Tethys.