Dolostones show abundant relict corals and 'algae' in massive unbedded strata  of the Yaptikshor Fm., which are identified as 50m thick reefs (ibid., p.102, 116): these have a Holorhynchus, Mesofavosites, Paleophyllum  fauna of Hirnantian age, suggesting that  these reefs were like those of the Baltic area.