Eocene to Oligocene nannofossils stratigraphy and environmental conditions in Izeh Province, Zagros Basin, East Tethys

Journal of Palaeogeography

Farah Jalili¹  Saeedeh Senemari² 

[1] Department of Geology, Faculty of Science, University of Birjand, Birjand, Iran;Department of Mining, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran;

关键词: Biostratigraphy;    Calcareous nannofossils;    Ecological indicators;    Tethys domain;    Zagros;    Paleogene;   

DOI  :  10.1186/s42501-021-00092-2

来源: Springer

【 摘 要 】

Data obtained from the calcareous nannofossils, distributed in the upper part of the Pabdeh Formation (Priabonian–Rupelian) and the lower part of the Asmari Formation (Chattian) in the Bid-Zard section, were used to investigate the Eocene to Oligocene palaeoenvironmental conditions in the southwest of Izeh, southwestern Iran (eastern Tethys). The upper part of the Pabdeh Formation was composed of shale, thin-bedded pelagic limestone and dolostone, which is disconformably overlain by the Asmari Formation. For the first time, 29 species of calcareous nannofossils belonging to 13 genera were identified in the studied section. The calcareous nannofossils in the upper part of the Pabdeh Formation indicate the Isthmolithus recurvus Zone/Sphenolithus pseudoradians Zone (combined zone), Ericsonia subdisticha Zone, Helicosphaera reticulata Zone and Sphenolithus praedistentus Zone, from the Priabonian to the Rupelian. The Sphenolithus ciperoensis Zone of the Chattian was identified in the lower part of the Asmari Formation. Calcareous nannofossil stratigraphy across the upper Eocene–Oligocene interval also reveals a disconformity at the Rupelian/Chattian transition due to a bio-event. Shallowing of the basin and environmental changes in this part of the Tethyan domain could have led to the lithostratigraphic and biostratigraphic changes. In fact, during the late Eocene to late Oligocene, marine phytoplankton was sensitive to climate changes such as decreasing temperature, as well as possibly to a nutrient increase and changes in basin depth.

【 授权许可】

CC BY