Porównanie piaskowców dolnego i środkowego odcinka warstw lubelskich (westfal) w Lubelskim Zagłębiu Węglowy

Abstract

Scharakteryzowano porównawczo skład mineralny, pozycję systematyczną i warunki sedymentacji piaskowców dolnego i środkowego odcinka warstw lubelskich. Stwierdzono znaczny wzrost wulkanogenicznych skaleni w wakach środkowego odcinka w porównaniu z wakami odcinka dolnego, przy generalnie wyższym udziale tych skaleni w obrębie wak w stosunku do piaskowców s.s. W piaskowcach dolnego odcinka spotyka się utwory plażowe, natomiast piaskowce środkowego odcinka warstw lubelskich powstawały w środowisku rzecznym, wydmowym lub wód spokojnych. Zarówno nasilenie wulkanizmu, jak też udział utworów pochodzenia plażowego zmniejszają się w kierunku północnym lub północno-zachodnim.COMPARISON OF SANDSTONFS OF THE LOWER AND THE MIDDLE PARTS OF THE LUBLIN BEDS (WESTPHALIAN) IN THE LUBLIN COAL BASIN A comparison has been made between two sandstone horizons occurring in the lower and the middle parts of the Lublin Beds. Position of the first horizon is determined by the bottom of the Westphalian formation and the coal Seam 391, while another exists between the coal Seams 391 and 379. Samples being a basis for laboratory examination have been collected from boreholes, location of which is showin Figs 1 - 3. A microscopic planimeter has been used to classify the sandstones under study and the results have been plotted on F.J. Pettijohn's, P. Potter's, and R. Siever's (1972) triangular diagram modified later by M. Nice and R. Unrug (1979). This has allowed for distinguishing the sandstones s.s. and the wackes (Fig. 5). When considering the sandstones 5.5. then a high content of quartz in total amount of the clastic components appears to be a common feature of both the horizons. The difference consists in moderate increase in feldspar participation in case of the middle sandstone horizon. This is a reason why the area covered by it on the Iithologic triangle is larger than that of the lower sandstons. If compared with the sandstones s.s., a higher participation of feldspars is a common feature of both the wacke horizons of the Lublin Beds. Feldspars are mainly of high-temperature nature, and their content in the middle part is visibly higher than in the lower one; this suggests a possible intensification of volcanism manifestations within the middle part of the Lublin Beds, Direction north-west of the Chełm 8 borehole (Figs 2, 3) shows a decreasing trend in feldspar participation in result of decline in volcanic processes. From relation of a skewness (GSK) and mean diameter (GSS, Fig. 6), as well as of a mean diameter (GSS) and a mean deviation (GSO, Fig. 7) a conclusion can he deducted that a beachy formation occurs within the sandstones of the lower part of the Lublin Beds, while only alluvial or dune types are the representative sediments within the middle part. The sea ingressions are evidenced by the beachy formations under and above the Seam 397 and above the Seam 393 as well. The beachy formations have been found in the southern part of the Lublin Coal Basin only; their lack has been proved in boreholes penetrating the central and the northern part of the Basin. This provides a basis for drawing a conclusion that the sea ingressions were coming from the southern direction.