Nannostratigraphy of Upper Cretaceous Sediments Northern Slopes of Central Alborz

Taking into account the extent of upper cretaceous deposits of Alborz region, determination of stage boundaries within the successions at different parts of the basin by the use of calcareous nannoflora was put on the agenda. Two stratigraphic sections viz. Alamde galandrud and Pol e zoghal were sampled at predetermined intervals. back to the laboratory, the samples were prepared using gravity settling technique 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 of deposition at the said time. the outcomes of nannostratigraphic investigations carried out in Pol e zoghal section along with the resalts of earlier studies in Alamde galandrud reveals that during the late cretaceous times the depositional center of the basin was lacated on the west and gradually shifted towards east. (i.e. sedimentation started earlier in the western parts and lasted longer in the eastern parts of the basin during late cretaceous times.)