Document Type: Original paper (Research paper)
and Mineral Exploration of mashhad, earth science of museum, mashhad, Iran
university of lorestan
University of lorestan
In order to determine the accurate sequence stratigraphy and paleoenvironmental conditions of the Oligo- Miocene deposits, four stratigraphic sections was studied in the central of the Urumieh- Dokhtar inter-arc zone. Based on distribution of the larger benthic foraminifera three assemblage zones have been recognized. Assemblages 1 and 2 indicate Chattian; assemblage 3 is restricted to Aquitanian. Two major depositional environments have been identified on the basis of a study of 228 hard and soft samples taken from the Qom Formation and by means of the analysis of biofacies and lithofacies features: The estuary( alluvium channel, the barrier, central basin and intertidal) and the shelf (inner, middle and outer shelf). The distribution of the larger benthic foraminifera with red algae and bryozoans indicates that shallow marine carbonate sediments of the Qom Formation have deposited at the studied area in the photic zone and at the uppermost aphotic zone in the tropical to subtropical environments. Based on the microfacies analysis and sequence stratigraphic studies, four third-order sequences were observed in studied sections.