Jurassic corals from the Shemshak Formation of the Alborz Mountains, Iran

Nineteen taxa of scleractinian corals are described and figured from the Toarcian-Lower Bajocian part of the Shemshak Formation of the Alborz Mountains. Dominant taxa are Isastrea, Microsolena, Trigerastraea, Periseris, and Collignonastraea. Most of these corals occur near the top of the formation (Lower Bajocian), close to the top of a large-scale shallowing cycle. Scattered specimens are found in transgressive lags of small-scale parasequences in the Toarcian part of the succession. Corals are very rare in the Shemshak Formation with the exception of Rian, NE of Semnan, where strongly reduced sedimentation rates facilitated the establishment of coral meadows and a patch reef in a mixed carbonate-siliciclastic setting on the crest of a tilted fault block.