sedimentological and geochemical studies of a paleosol horizon at the boundary of the Neyzar and Kalat Formations (Upper Cretaceous) in the eastern Kopet-Dagh basin

The studied section is located at the Tange-Neyzar, 115 km NE Mashhad. The upper part of the Neyzar Formation consists of shale and marl, while the basal parts of Kalat Formatiom is composed of sandstone unit with interbedded shale. An oxisol type has been identified at the boundary between these formations. There are characteristics macromorphological and micromorphological features in this oxisol unit. The occurrence of beta microfabric indicates the role of micro-organisms activities in the formation of the palaeosol. The geochemical studies indicate that the average paleotemperature is 11˚ C. The paleo-rainfall varies from 818.66 to 1563 mm (with an average 1200 mm). The pressure of CO2 was measured from 2237.10 to 2981.08, which is 7.99 to 10.65 times the current value. It corresponds to the modeled values for that geological time in the other areas of the world. In addition, the fluctuation of water-stable (falling at sea level) played a critical role in the development of palaeosol in this section.