Biostratigraphy of the nummulitids and lepidocyclinids bearing Qom Formation based on larger benthic foraminifera (Sanan
- PDF / 2,359,597 Bytes
- 21 Pages / 595.276 x 790.866 pts Page_size
- 18 Downloads / 162 Views
ORIGINAL PAPER
Biostratigraphy of the nummulitids and lepidocyclinids bearing Qom Formation based on larger benthic foraminifera (Sanandaj–Sirjan fore-arc basin and Central Iran back-arc basin, Iran) Ebrahim Mohammadi & Mohammad-Reza Vaziri & Mohammad Dastanpour
Received: 22 February 2013 / Accepted: 20 September 2013 # Saudi Society for Geosciences 2013
Abstract Qom Formation in the Sanandaj–Sirjan fore-arc and Central Iran back-arc basins was studied in order to determine its accurate age. Larger benthic foraminifera (mainly Lepidocyclinidae, Nummulitidae, and Neoalveolina ) are biostratigraphically the main biota of the Qom Formation in the study areas. There are some debates concerning the age dating of the Qom Formation layers based on the presence or absence of Nummulites and Eulepidina. However, the last true Nummulites spp. became extinct at the top of Late Rupelian and all of the in situ Nummulites bearing layers of the Qom Formation belong to Rupelian in age. Lepidocyclinids, which originated in the Americas during the Middle Eocene, reached Iran in the Rupelian. The first appearance of Lepidocyclina spp. in our study sections, before the last occurrence of Nummulites spp., clearly indicates that the earliest Lepidocyclinidae reached Iran in the Rupelian. The Lepidocyclinids are widespread in the Chattian marine deposits of Iran. The presence of in situ Nummulites (with or without Eulepidina) in Qom Formation successions indicates an Early Oligocene (Rupelian) age, and the presence of Eulepidina without Nummulites suggests a Late Oligocene age (Chattian; possibly into Aquitanian). Moreover, Nummulites intermedius-Nummulites vascus Assemblage zone of Wynd (1965) and Eulepidina-Nephrolepidina-Nummulites E. Mohammadi (*) : M.
Data Loading...
