Source Rock Potential of the Organic Rich Turonian - Upper Campanian Carbonates of Northern Lebanon

Samer Bou Daher, Fadi H. Nader, and Ralf Littke

The Upper Cretaceous rock succession in the eastern Mediterranean includes several horizons of increased organic matter content. 209 samples from shallow cores covering the Turonian - Upper Campanian rock succession in North Lebanon were analyzed for total organic carbon, total inorganic carbon, and total sulfur (TS). A representative selection of samples was used for Rock Eval pyrolysis, macerals analysis, vitrinite reflectance, and molecular organic geochemistry of the aliphatic fractions by means of gas chromatography-flame ionization detection (GC-FID).

The elemental analysis revealed a very good source rock potential for the Upper Santonian - Upper Campanian 150 m interval, with an average of 1.9% Corg. A positive correlation between Corg and TS implies a system controlled by the availability of organic matter for sulfate reduction and hence a deposition in a dysoxic marine environment (oxygen depleted). This is also reflected in the Pr/Ph ratios ranging between 0.63 to 1.1, as well as the Pr/nC17 and Ph/nC18 ratios. A negative correlation between Corg and CaCO3 is due to the variable preservation of organic matter induced by fluctuation of oxygen content in sea water and/or variation in organic matter primary productivity related to fluctuation in upwelling intensity. The latter is supported by TS/Corg ratios implying a productivity controlled organic matter deposition. Dominance of alginite macerals vis-à-vis terrestrial macerals also indicates a marine depositional environment and matches the high HI values characterizing these source rocks as type I kerogen. Tmax values and vitrinite reflectance both show a very immature organic matter.

This characterization of exposed organic rich rock succession leads to a better reconstruction of the paleogeographic, paleobathymetric, and paleoclimatic setting of the SE Tethys margin during the Late Cretaceous, and is crucial for understanding source rock distribution and petroleum systems within the Levant Basin and Margin.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013