Organic Facies And Thermal Maturity Of Lower Cretaceous Sediments In Northern Sinai (Egypt)

KIM, JUNGHYUN; WAGNER*, THOMAS; KUSS, JOCHEN; and BACHMANN, MARTINA, University of Bremen, FB 5 - Geosciences, Germany

Organic geochemical and organic petrological investigations were performed on Late Aptian to Early Cenomanian sediments along a S-N transect in the northern Sinai in order to characterize the facies and thermal maturity of organic matter.
The results of organic geochemical analyses (C/N ratios, Hydrogen indices) indicate a dominance of hydrogen-depleted organic matter, probably of terrestrial or degraded marine origin, presenting a mixture of kerogen types III and IV. Maceral analysis shows mainly reworked or oxidized particulate organic matter, e.g. a mixture of vitrinite, migrabitumen, graphite, and traces of inertinite. The organic facies of Cretaceous northern Sinai deposits are classified to be C to D, indicating a proximal fluvio-deltaic or oxic shelf depositional environment.
Tmax values suggest an immature maturity level of the organic matter, although some suppression of Tmax values is attributed to the occurrence of migrabitumen. Because of the deficiency of vitrinite, reflectance measurements were also carried out on migrabitumen. Corrected mean reflectance values of migrabitumen and mean reflectance values of vitrinite range from 0.6 to 0.7 Rm%, indicating a high volatile bituminous coalification stage. Assuming a normal geothermal gradient for the study area a maximum burial depth between 1.2 and 2.0 km is estimated for the Cretaceous strata of the northern Sinai.

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