Organic geochemistry (Rock-Eval) and maturation rank of the Garumnian coalin the Central Pyrenees (Spain)

Maturity and source rock potential of coal and organic matter-rich levels i n the Tremp Formation in Berga, Tremp and Ager (Central Pyrenees) are analy zed by optical and geochemical techniques. The organic matter has a humic c onstitution, and is mainly included in a carbonatic rock matrix. The averag e vitrinite reflectance were found between 0.35 and 0.45%, corresponding to organic-rich levels and coal levels, respectively; these values are charac teristic of a low maturity. This parameter shows a good correlation with fl uorescence colors, calorific value higher than 24 MJ/kg wet sample without ashes, mineral matter diagenesis and average T-max (430 degrees), and it in dicates that the range of maturity fits the immature diagenetic state borde ring maturity, near to the oil window. Composition and maturity of organic and inorganic matter are similar in the Berga, Tremp and Ager areas. The th ree areas were part of a single basin located to the north, corresponding t he Ager zone to the distal environment episode and thus, paleoenvironments were similar in all the studied zones. These materials suffered a low-grade transformation, consequence of a low lithostatic pressure. So, the Garumni an Tremp Formation coal may be classified as sub-bituminous, corresponding to a low rank of maturity. (C) 2000 Elsevier Science Ltd. All rights reserv ed.