Characteristics of Near-Surface Part of the Orzesze Beds in the Region of the Main Saddle in View of Weathering Processes

Abstract

AbstractThe article presents the characterization of a near-surface part of Orzesze beds in the region of the main saddle. The lithological profile of the region in concern has been confirmed to contain claystones with interburdens of sandstones and sands occurring at the surface. Among the claystones, a coal bed was drilled into.Field observations with a video camera, direct observations made in the boreholes and laboratory studies of the obtained rock samples have indicated high levels of weathering of the clastic formations.The weathering processes within the sandstones form fissures and rock voids by means of which rainwater flows freely into the deeper parts of the rock mass.The mineral composition of the sandstones includes mostly quartz, accompanied by plagioclases, micas, breccias and heavy minerals in smaller amounts. The binding material is cement-type and clayey-carbonate. The sands occurring at the surface constitute their eluvium, which is evidenced by similar texture qualities of both the sediments. The claystones contain mostly kaolinite and quartz; in their composition minerals from smectite group were also found. They are characterized by very high absorbability, which leads to their swelling and washing out. It has been found that the weathered parts of rocks indicate significantly lowered compressive strength in comparison to the values assumed in case of the rocks of the Orzesze beds.