Abstract

Ruteh Formation is composed of dark bioclastic limestone and marl layers in the Baghdarreh section, Soltanieh Mountains (northwest Iran). It is about 43 meters in thick. Ruteh Formation is Murghabian in age based on foraminifers’ assemblages. Carbonate layers contain Zoophycos, Chondrites, Planolites and Rhizocorallium trace fossils, which Zoophycos is the main and abundant among other rare trace fossil. Microfacies analysis (10 identified microfacies) shows sediments of Ruteh Formation deposited in three facies belts including inner, middle and outer homoclinal carbonate ramp. Zoophycos only present in the outer ramp to open marine microfacies with anaerobic and low tolerances conditions, below storm weather base. Where the depth increased, size of Zoophycos and its burrow diameter increases which fellowed by development of bioturbation. Ruteh Formation’s Zoophycos have no lobate structure and it formed in organic bearing carbonate sediments.