Green Algae (Dasycladales) from Paleocene deposits in Western Birjand (Grong section)

The study area is located between Lut and Helmand blocks. This area is named Eastern Iran Flysch Basin. This basin is surrounded between Nehbandan fault in the west and Harirrud fault in the east (Stöcklin, 1968). Post Cretaceous deposits of Birjand area are composed of different facies with variations thickness. Paleogene deposits in Birjand area formed after Laramid orogeny phase in Paleocene and ended in late Middle Eocene (Eftekharnezhad, 1986).
The studied section is located about 60 kilometers west of Birjand. Access to the outcrop is along Birjand-Kerman road. After passing through Khusf city and Dastgerd village, a gravel road separated from Birjand-Kerman road. The measured section is near Gorong village. The geographical position of the section is 32o 52′ north latitude and 58o 52′ east longitude. This section is about 26 kilometers North West of Khusf City.
Paleocene deposits in the study area include sandstone and conglomerate at the base, then changes to sandy limestone, marly limestone, thick bedded to massive limestone in middle and upper parts, and marly limestone and conglomerate in uppermost part.
In order to study algae in carbonate beds, samples collected from different intervals. Sampling interval is between 1/5 meters and 3 meters, which in clastic beds the intervals are greater than carbonate beds. Ninety samples have been collected in the field and thin sections prepared from all samples.. The photomicrograph of fossils prepared and based on references, genera and species of algae, identified, described and introduced. The thickness of measured stratigraphical section is 342/5 meters and could be divided into four units. There are conglomerate beds above the boundary (unit A and B). In uppermost part of unit D also there are conglomerate beds. It seems the lower and upper boundaries are disconformable. The lithology of units are as follows:Unit A- The lower part of this unit is covered, then 53 meters of marl and with thin intercalated limestone beds are present.
Unit B- This unit include 111 meters of conglomerate at the base, then changes to sandstone and massive limestone.
Unit C- This unit is composed of 144.5 meters of thick bedded limestone with marly limestone.
Unit D- This unit is composed of 34 meters marly limestone in lower part and conglomerate and sandstone in upper part.
After studing thin sections of units B and C, the following algae are identified; Clypeina occidentalis, Clypeina aff. dragastani, Clypeina cf. haglani, Clypeina elliotti, Clypeina cf. elliotti Clypeina cf. lucana, Cymopolia cf. frugifera, Cymopolia edwarsi, Cymopolia cf. mayaensis, Cymopolia drobneae, Cymopolia satyavanti, Dissocladella aff. longijangensis, ?Broeckella sp., Orioporella villattai, and Ovulites cf. arabica. In all identified genera and species, all parameters such as outer and inner diameters, branch diameter in proximal and distal, number of branches in every verticil were measured. Although the Paleocene deposits in western Birjand consist of clastic and carbonate sequences, the carbonate deposits contain a good variety of algae especially green algae. The most important identified genera and species are Clypeina occidentalis, Clypeina aff. dragastani, Clypeina cf. haglani, Clypeina elliotti, Clypeina cf. elliotti Clypeina cf. lucana, Cymopolia cf. frugifera, Cymopolia edwarsi, Cymopolia cf. mayaensis, Cymopolia drobneae, Cymopolia satyavanti, Dissocladella aff. longijangensis, ?Broeckella sp., Orioporella villattai, Ovulites cf. arabica. The assemblage algae confirm Paleocene age and foraminifera such as Kathina sp., Mississippiana binkhorsti, Mississippiana sp., Rotorbinella detrecta, Rotalia sp. also support this age.