Materia orgánica y diagénesis de la formación de margas del Mas d´Ascla (Jurásico superior) en la cuenca del Maestrazgo (Cadena Ibérica oriental)

Abstract

The Mas d'Ascla marls Fm. (Upper Kimmeridgian to lowermost Tithonian) in the Maestrat Basin (Salzedella sub-basin, Castellò de la Plana) displays two organic-carbon-rich horizons which indicate anoxic conditions. The maximum anoxic event is located at the base of the formation corresponding to the lower part of the trangressive system tract. In both horizons the kerogen is mainly of marine origin with algal and amorphous sapropelic organic matter, a low organic carbon content (0.5% - 1.26%) and a low potential yield of hydrocarbons (HC). These data and the Tmax. suggest a mature source-rock which has already generated nearly all HC. Extractable organic matter is fundamentally composed of asphaltenes and resins predominating over saturate and aromatic compounds which have been probably expulsed out of the source rock.