In order to study the biostratigraphy of the Upper Cretaceous deposits in north of Lut block, one stratigraphic section in Bahabad south-west Bajestan area was selected and sampled. The thickness of the Upper Cretaceous deposits in this section is 152.48 meters and based on lithological changes it is divided into five rock units: clastics rocks, gypsiferous marl, lower limestone, marl and upper limestone. The lower boundary due to lack of outcrop is not recognizable and the upper boundary underlies the recent erosional deposits. In biostratigraphic studies with the exception of two basal rock units that have no fossils in the other three rock units: lower limestone, marl and upper limestone 53 genera and 47 species of benthic foraminifera were recognized and two biozones identified as follows:
Biozone 2: Rotorbinella campaniola- Pararotalia tuberculifera- Pseudocyclammina massiliensis assemblage zone
Biozone 1: Rotorbinella mesogeensis- Pararotalia boixae- Dicyclina sampoi assemblage zone.
According to the determined biozones and fossils associations the age of four basal rock units are Cenomanian and upper limestone unit is Santonian- Early Campanian. A sedimentary gap is visible during Turonian- Coniacian between marl and upper limestone rock units in this section.

Keywords: Biostratigraphy, Upper Cretaceous, Lut block, Bahabad, Bajestan, Northeast of Iran

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