Tekstury stylolitowe w cechsztyńskich skałach węglanowych poziomu W1 monokliny przedsudeckiej

Abstract

STYLOLITIC TEXTURES IN THE ZECHSTEIN CARBONATE ROCKS OF THE HORIZON Wl OF THE FORE-SUDETIC MONOCLINESummaryIn the Zechstein W1 (Ca1) carbonate rocks of the Fore-Sudetic monocline, the stylolitic textures are very common. There are distinguished here microstylolites, stylolites and slickolites (J. H. Bretz, 1950). According to their morphology both stylolites and microstylolites reveal columnar forms (Table III, Fig. 11), saddle-shaped and dentate forms (Table III, Fig. 12), and mixed forms, mainly of columnar-dentate nature. It has been ascertained that stylolite sutures occur in homogenous rock environment (Table I, Fig. 1), and also at the boundaries of various environments. This is a very characteristic phenomenon, in which the stylolite sutures separate rocks of different, but petrographically identical textures (Table I, Fig. 4), or rocks of different structure and petrographical feature (Table II, Fig. 5).The stylolite sutures are filled in eith a clay-coaly substance with detrital quartz admixture, as well as of carbonate rock mass (residual elements). Gypsum, barite, fluorite and ore minerals are here allochthonous components. The carbonate rocks of Wl also reveal some slickolites (Table IV, Fig. 16), which are strongly related to tectonics, their course (NW-SE) being approximate to the main directions of features (NW-SE and NNW-SSE). The observations of the slickolites demonstrate that they are formed due to horizontal movements on the surfaces which are perpendicular to the bedding. The examinations of the carbonate rocks and of the stylolites found in them point to a lot of dependences, among which the following are most important: 1 - stylolites intersect the primary sedimentary structures, 2 - stylolites formed at the contact of crystalline limestones and limestones with ooides intersect the individual ooides, 3 - in the silicified carbonate rocks stylolites are destroyed by quartz crystals or aggregates, 4 - vein formations (gypsum, calcite or fluorite-barite ones) intersect the stylotites, 5 - in breccias of carbonate rocks the stylolite sutures are disrupted and destroyed, 6 - both rock fractures and slickolites also are responsible for the breaking of continuity in stylolites. It results that the separation of non-carbonate compounds during the recrystallization of rocks is the main factor in the formation of the stylolites. On the other hand, the formation of stylolites is related to both pressure and difference in plasticity, which exist between the carbonate environment and the residual environment formed due to the separation. This leads to the formation of strains between these two environments, resulting in the differentiated morophology of the stylotites under examination. According to the authors’ opinion the stylolites found in the carbonate rocks of the Fore-Sudetic monocline should be recognized as diagenetic-epigenetic and tectoepigenetic ones.