Combined use of palynology and organic geochemistry in petroleum potential evaluation and paleoenvironmental interpretation of the Kazhdumi Formation (Aptian-Cenomanian) in the southwestern Zagros Basin, Iran

The Kazhdumi Formation of the Bangestan Group is a well-known and important source rock in most oil-fields in the Zagros Basin. In order to examine productivity of this formation in southwestern Iran, and to correlate petrographical and palynological data with geochemical properties, one of the best outcrops of this formation, located in Tange-Maghar 45 km northwest of Behbahan city, was sampled. Fifty-two rock samples were collected from the 270 m thick section which is made up of dark shales with intercalations of marl and limestones, and treated palynologically. Three palynofacies were differentiated based on statistical studies of palynological slides and the rock samples representing these palynofacies were geochemically analyzed. Palynofacies results were then correlated against the geochemical analysis. Palynofacies I (PF-1) with 90 to 100% Amorphous Organic Matter (AOM) presents high hydrogen index (HI) and total organic carbon (TOC) values. PF-1 contains kerogen type I/II and could potentially produce oil. The second palynofacies (PF-2) contains reduced amounts of AOM, HI and TOC and the kerogen is of type II/III, potentially producing oil and gas.