ZMIENNOŚĆ FIZYCZNO-MECHANICZNYCH WŁAŚCIWOŚCI UTWORÓW GÓRNYCH WARSTW LGOCKICH MIĘDZY SUŁKOWICAMI A MYŚLENICAMI

Abstract

VARIABILITY OF PHYSICAL AND MECHANICAL PROPERTIES OF THE UPPER LGOTA ROCKS BETWEEN SUŁKOWICE AND MYŚLENICE

Abstract. The author investigated the relation between lithological development, controlled by sedimentary conditions and diagenetic changes, and physical and mechanical properties of rocks of the Upper Lgota Beds. The strata belong to a fragment of the Silesian Unit in the Beskid Wyspowy Mts and are situated between Sułkowice and Myślenice. The characteristic profiles are exposed in three quarries on I the southern slopes of the Barnasiówka rangę: Jasienica I, Jasienica II and Bysina II. They contain the most typical and fully developed sets of strata that have been included after Ghibaudo (1992) into ten subfacies, composed of seven facies types. The dominant are sand-stone-mudstone couplets (SM) and sandstone-mudstone couplets with hornstones (SMH). The strata of the remaining facies: conglomeratic sandstones (SC), sandstones (S), mudstone-sandstone couplets (MS), mudstones (M) and hornstones (H) occur less frequently. The author have shown that the lithological features of the Upper Lgota strata such as the minerał composition, grain size distribution, type and amount of cement and the character of textures within the layers, are controlled by sedimentary conditions and diagenetic changes that affected the sediments. The material deposited by density currents of variable energy was prone to the action of diagenetic processes, mainly dissolution, cementation, replacement and recrystalization, different than those characteristic of a given subfacies. These processes affected to a considerable degree development of physical and mechanical properties of rocks, controlling applicability of the given rock commodity. The hornstones (H) and the sandstones with intercalations of hornstones (subfacies mSMH and lSMH) reveal the most favourable parameters. This fact can be explained by the presence of siliceous intergranular cement and authigenic silica rims on detrital grains. The silica most probably originated from dissolution of siliceous sponge spicules and detrital quartz grains. Strong silicification of the Upper Lgota Beds strata was favoured by a rather strong porosity of not fully consolidated sediments, and additionally increased by dissolution of their carbonate components. In the layers of the mS, lSM and mlS subfacies this process was less intense and, as a result, the amount of siliceous cement is lower. Therefore, the physical and mechanical properties of the sandstones belonging to these subfacies are worse.