Lower Silurian corals of the Leningrad region
Abstract
In the Ordovitch deposits of the schist mine region by Gdov the Rugosa corals occur in two bioecoses as follows: the Bryozoa biogenosis in the upper parts of the Jeva layers with a considerable amount of bronchy and lamellated colonies of Bryozoa and individual representatives of Rugosa. This biocenosis has existed in conditions of an alternating regime of slow currents and precipitations of slime and other matters. The coralline Brachypode biocenosis of the Middle-Wezenberg layers with a considerable amount of individual corals, Brachypodes, spherical colonies of Bryozoa and other fauns. A constant regime prevailed here, strong currents, absence of foreign matters in the sediments of lime. In the deposits of the Middle-Wezenberg layers corals were found that preserved their natural position and were still fastened to the former sea bottom. The rim of their calyx being horizontal to the surface and their convex part oriented towards the gentle slope of the rollers on the sea bottom — as it is shown on the sketch (fig. 4). The analyses of the rollers and the geological structure of this region both indicate that the corals were generally oriented by their convex part towards the currents that prevailed here, which is corroborated by the theoretical assumptions of prof. N. N. Yakovlev and stands in direct opposition to the scheme of Weissermel (fig. 2).
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References
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