Lower Silurian corals of the Leningrad region (distribution and lifestyle)

Abstract

In the Oidovich deposits in the area of the Gdov shale mines, Rugosa corals are found in the following two biocenoses: 1) Bryozoa hiogenosis in the upper parts of the Jeva layers with a significant number of bronchial and lamellar colonies of bryozoans and individual representatives of Rugosa. This biocenosis existed in the conditions of an alternating regime of slow currents and sediments of mucus and other substances. 2) Coral brachiopod biocenosis of the Middle Wesenberg layers with a significant number of individual corals, brachypods, spherical colonies of bryozoans and other fauns. A constant regime reigned here, strong currents, and the absence of foreign impurities in the lime deposits. In the sediments of the Middle Wesenberg strata, corals were discovered that had retained their natural position and were still attached to the former seabed. The edge of their cup is located horizontally to the surface, and the convex part is oriented towards the gentle slope of the rolls on the seabed - as shown in the figure. Analysis of the swells and the geological structure of this region show that the corals were mainly oriented with their convex part towards the currents prevailing here, which is confirmed by the theoretical assumptions of Prof. N. Yakovlev and is in direct opposition to Weissermel’s scheme. Paleontological office of LGI.