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SUMMARY

An attempt was made to find the ways for quantitative estimation of changes of the sedimentation processes and paleogeographic environments in the geological past. Quantitative regularities on the basis of rock volume measurements were found in the history of sedimentation and environmental conditions on the Russian Platform beginning in Late Riphean (Pt3) until Quaternary, through the main geotectonic cycles (Caledonian, Hercynian and Alpine).

It was shown that there were no major differences between sand and clay abundance (26.0% and 30.1%, respectively). Limestones are most abundant among carbonate rocks (17.0%), followed by dolomites (10.2%), then marls (7.5%) and finally chalk (2.0%). Surprising was the very high abundance of gypsum and anhydrite (2.7%) and of salts (3.1 %). Being in agreement with data of many other regions of the world, this fact has far reaching consequences, first of all, concerning the history of ocean salinity and, secondly, for the knowledge of geochemical cycles of Na, C1 and S.

A predominance of terrigenous sedimentation has been found for the Caledonian and Alpine cycles, whereas a greater abundance of chemical and biochemical sedimentation occurred in the Hercynian (Variscian) cycle. Each of these cycles is characterized by the common scheme of periodical recurrence of main rock types from the initial to the final stages. (Fig. 2).

Fig. 8 shows the prevailing role of uplift and erosion on the Russian Platform (76% of the total platform area); only 5.7% of the area falls on the continental sedimentation, 1.8% on the lagoon environments, and 16.5% on the marine sedimentation. This is in contrast to the geosynclines which were dominated by marine sedimentation. Considering now only the regions of stable subsidence and “fixed” sedimentation of the Russian Platform (Fig. 5) we find that here marine sedimentation dominated (68.9% of the areas of stable subsidence) in comparison with the continental environments (23.6%). As well as the abundance of sediments, the distribution of the main types of paleogeographical conditions changed during the cycles with extreme regularity according the periodic law. (Fig. 6,7). The periodicity of sedimentation and the alteration of paleogeographical conditions were finally determined by the periodical rhythm of platform epirogenic movements.