Compaction of organic-rich carbonate and siliceous mud: mechanism, rate, typical structures. Case studies from Domanik Formation (Russia).

This article examines the compaction of organic-rich siliceous-carbonate sediments, using Upper Devonian-Lower Carboniferous deposits in the southeastern East European Platform as an example. The study is based on the analysis of deep-well core samples containing rocks with varying organic carbon contents. The methodology includes petrographic analysis of thin sections and sedimentological study of the core. Typical features of compaction were identified: the formation of folded calcite veins filled with calcite, the development of saucer-shaped concretions, and flat-pebble breccias. It was established that the degree of rock compaction can exceed threefold. Particular attention is paid to the study of deformation structures arising during compaction. It was found that specific structures reflecting the plastic state of the sediment are formed in layers with high organic matter contents. The mechanisms of silica and calcite redistribution during compaction, as well as the interactions between compacting and early lithified layers, were studied. The results obtained provide a better understanding of sedimentary rock transformation processes and can be used to reconstruct depositional environments and subsequent diagenetic transformations. This study contributes to our understanding of the mechanisms of deformation structure formation in organic-rich sediments.