Trace Fossils, Ichnofacies and Paleoenvironment of the Mishan Formation in the Dezful Embayment, SW Iran

Authors

1 Ph. D., student. Dept., of Earth sciences, Islamic Azad University (IAU), Science and Research Branch, Tehran, Iran

2 Assoc. Prof., Dept., of Geology, Faculty of Science, Lorestan University, Khorramabad, Iran

3 Assist. Prof., Dept., of Earth sciences, Islamic Azad University (IAU), Science and Research Branch, Tehran, Iran

4 Prof., Dept., of Earth sciences, Islamic Azad University (IAU), Science and Research Branch, Tehran, Iran

Abstract

In this study, a detailed investigation the trace fossils of Mishan Formation in the Omidieh section has been carried out. The Miocene Mishan Formation has a diverse collection of trace fossils, which includes 4 ichnogenera and 5 ichnospecies. These trace fossils show locomotion, feeding, sheltering and grazing behaviors and include Protovirgularia cf. pennatus, Planolites isp., Helminthopsis isp., Thalassinoides isp. and Thalassinoides suevicus. The trace fossils of Mishan Formation are in the alternation of massive, medium to thick beded limestone, medium to thick beded sandstones, and marl. In this study, 5 bioturbation indexes were identified according to the standard bioturbation indicators, as well as 5 ichnofabrics related to delta, tidal flat and lagoon environments. The great variety of ethological classification including locomotion, feeding, sheltering and grazing, along with the trace fossil record of sediment feeding organisms and, to a lesser extent, suspension feeding animals, confirm very shallow sedimentary environment with a high oxidation content.

Keywords