Nannostratigraphy of Upper Cretaceous Sediments Northern Slopes of Central Alborz
Subject Areas :
آذین Ahifar
1
(کارشناس ارشد چینهشناسی و فسیلشناسی دانشگاه شهید بهشتی، تهران)
انوشیروان Kani
2
(عضو هیئت علمی دانشگاه شهید بهشتی تهران)
معصومه Noori
3
(کارشناس ارشد چینهشناسی و فسیلشناسی دانشگاه شهید بهشتی، تهران)
Keywords: upper cretaceous, Polezoghal section, Alamde galandrud section, , calcareous nannofossils, paleogeography,
Abstract :
Taking into account the extent of upper cretaceous deposits of Alborz region, determination of stageboundaries within the successions at different parts of the basin by the use of calcareous nannoflora wasput on the agenda. Two stratigraphic sections viz. Alamde galandrud and Pol e zoghal were sampled atpredetermined intervals. back to the laboratory, the samples were prepared using gravity settlingtechnique and the resulting thin sections.The nannofloral assemblage of the upper cretaceous rocks of northern Alborz region reveal coniacianmaastrichtian age at Pol e zoghal (west) and campanian-early paleocene age at Alamde galandrud (east).moreover, the region was situated at low paleolatitudes and experienced a low marginal environment ofdeposition at the said time. the outcomes of nannostratigraphic investigations carried out in Pol e zoghalsection along with the resalts of earlier studies in Alamde galandrud reveals that during the latecretaceous times the depositional center of the basin was lacated on the west and gradually shiftedtowards east. (i.e. sedimentation started earlier in the western parts and lasted longer in the eastern partsof the basin during late cretaceous times.)