Biostratigraphy and palaeoecology of the Asmari Formation at southwest of Firozabad

رخساره‌های رسوبی

Article 7, Volume 3, Issue 1, February 2011   

Document Type: مقالات پژوهشی

DOI: 10.22067/sed.facies.v3i1.2717

Authors

Behnaz Kalanat^* ; Hossein Vaziri Moghaddam; Azizollah Taheri

Abstract

Three assemblage zones (Rupelian-Chattian age) have been identified by distribution of large benthic foraminifera in the study area. The Firozabad section was compared with Chahangir (Rupelian) and Dil (Chattian-Burdigalian) sections. Early Oligocene carbonate (Firozabad and Chahangir sections) was deposited at the edge of Zagros foreland basin whereas towards the center of the basin, the Pabdeh Formation continued to accumulate. The Miocene part of the Asmari Formation, as seen in the Dil section, is absent in Firozabad and Chahangir sections. This suggests that Oligocene sea level fall restricted marine deposition and Asmari Formation replaced laterally by the Gachsaran Formation. The biotic associations and palaeolatitudinal reconstructions suggest that carbonate sedimentation took place in tropical waters under oligotrophic conditions in the study area, a favorable environment for photozoan assemblages. The dominance of heterozoan assemblages seems to be related to the palaeoecology and evolution of zooaxanthellate corals, which were not able to construct reefs against the destructive waves; actually they lived in the meso-oligotrophic zone.

Keywords

Oligocene; heterozoan assemblages; Biostratigraphy; Asmari Formation; large benthic foraminifers

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