Environmental impacts on the ichnofossil diversity of the lower part of the Elika Formation (Lower Triassic), Moro Mountain, NW Iran

Document Type : Regular Paper


1 Department of Geology, Faculty of Science, University of Zanjan, Zanjan 38791–45371, Iran

2 Department of Geology, University of Payam Nor, P.O. Box 19395-3697, Tehran, Iran


Early Triassic carbonate ramp sediments of the lower part of the Elika Formation are known as Vermicular limestone. In the Moro Mountain, northwest Iran, the Vermicular limestone includes bioturbated dolomitic mudstone, bioclastic packstone and grainstone, algal calcirudite and intraclastic grainstone. These sediments accumulated in their lower part in open marine subtidal and shoal environments, changing upward to lagoonal and intertidal environments. Heavily bioturbated gray mudstone formed under quiet water conditions in lagoon and lower intertidal environments. Storm processes and high salinity indicative of an arid environment influenced the activities and distribution of euryhaline and/or opportunistic trace-makers. The low biodiversity of the trace-maker community is reflected by the low ichno-diversity, the sole trace fossil being abundant Planolites.