Microbial deposits as anachronistic facies occur in the lower Triassic succession of Abegarm area, Qazvin province, north-west Iran. These can be classified into two major groups: Microbialites and microbially coated grains. Microbialites are present in form of thrombolite and stromatolite. Thrombolites include microgastropods, foraminifers and ostracods, which indicate at least fairly oxygenated environment. Ooids and coated grains are also an important components after the end-Permian extinction in Abegarm area. Thin section studies corroborates that some of these allochems are microbial in origin. Pre-microbialite ooids (deposited right after extinction event) are recrystallized but their concentric, dense nature may imply to a microbial origin. Post-microbialite ooids and coated grains display a better preservation and their cloudy cortices and asymmetric forms are characteristics of microbial influence. Cortoids with constructive micrite envelops and pyrite-rich encrusted grains are another evidence of microbial contribution in carbonate sedimentation aftermath the end-Permian extinction. The results of this study shows that unusual lower Triassic facies developed in Abegarm area as in several other regions worldwide. Faunas included in microbialites indicates an oxygenated situation through their development. However microbialites and microbially coated grains expansion demonstrates an atypical, stressful condition following end-Permian extinction.
