The structure and mechanisms of the formation of coastal terrigenous rocks in Permian epicontinental basins of northern Russia

Structure and mechanisms of the formation of coastal paragenetic associations are widespread in the Permian terrigenous sequences of northern Russia. They are examined using the Kungurian-Ufimian rocks of northeastern Pai-Khoi as an example. Analysis of bed successions in the 620-m-thick section interval made it possible to distinguish 37 cyclothems, each being the result of execution of one transgression-regression sedimentation cycle. Based on the results obtained, the structural-genetic characteristics of bed successions of two types are given. The first type is represented by the Liur-Yaga ideal cyclothem related to landscapes of open coasts, which exist in both transgression and regression phases of sedimentation. The second type is represented by the Tab-Yu ideal cyclothem related to the formation of lagoon-bar systems in the regression phase of the sedimentation cycle and their destruction during transgressions. In the Pechora and Taimyr basins, bed successions of the two types were revealed in similar (with respect to composition and structure) Permian formations of different ages. It is likely that the proposed models are universal enough to be applicable for studying the terrigenous epicontinental rocks of humid zones irrespective of their age.