Jurajska pokrywa Lubelskiego Zagłębia Węglowego

Abstract

Przedstawiono charakterystykę osadów jurajskich. które w LZW bezpośrednio przykrywają utwory karbońskie. Osady jury reprezentowane są przez szereg charakterystycznych typów skał o łącznej miąż­szości do 210 m. Stratygraficznie są to utwory wyższej jury środkowej i jury górnej. Najniższą część pokrywy jurajskiej stanowią utwory nierozdzielnego batonu i keloweju lub dolnego oksfordu. Wyższą część budują utwory oksfordu środkowego i górnego oraz kimerydu. Utwory portlandu w LZW nie występują.JURASSIC COVER IN THE LUBLIN COAL BASIN Jurassic deposits form a cover of the Carboniferous almost in the whole area of the Lublin Coal Basin. The Carboniferous is overlain by Jurassic rocks varying in age: Upper Bothonian, Lower Oxfordian, and Middle and Upper Oxfordian (Fig. 1), Basal surface of the Jurassic is here clearly monoclinally inclined. It occurs al depth of about 300 m in the east and about 900 m in the west and the dip is below 3° (Fig. 2). At present. thickness or the Jurassic ranges from 10 200 m in the Lublin Coaal Basin (Fig. 3). In result of pre-Cretaceous erosion, marked pans of the Jurassic section became removed: the Portlandian and a part of Kimmeridgian in the west and also Oxfordian in the east (Fig. 4). The area of the Lublin Coal Basin is relatively small but. nevertheless. Jurassic deposits are markedly differentiated here. In the west and north. the Jurassic section begins with Bathonian deposits (Figs. 5, 6, 7): gray calcareous sandstones with carbonized flora and fine debris of bivalve shells. Basal conglomerate of transgressive nature is lacking here. Higher members of the Middle Jurassic are represented by rusty organodetrital crinoidal limestones with pisolites and limonitic crusts. Middle Jurassic deposits are less than 20 m thick in northern part of the studied area and they are lacking between Chełm and Hrubieszów and north-west of that region. Lower Oxfordian deposits are more widely distributed (Fig. 5). They are developed as two lithostraligraphic formations: Kraśnik Formation, represented by spongy limestones with cherts, and Zakrzew Formation - gray, brittle sandstones and siltstones with carbonized plant remains (Figs. 5, 8, 9). In the Lublin Coal Basin, the Kraśnik Formation is up to 20 m, and the Zakrzew - from a few to about a dozen meters thick at the average, being the thickest (36 m thick) in the borehole column Lublin IG 1. The deposits are overlain by those of the Jasieniec Formation in western part of the Lublin Coal Basin, and the Coral Formation in the eastern part. The former is represented by organodetrital crinoidal limestones and the latter - by coral limestones. Upper part of the Oxfordian is developed as the Bełżyce Formation (oolitic and pelitic limestones) almost in the whole area of the LubIin Coal Basin, being only locally (Hrubieszów region) represented by terrigenous deposits of the Tyszowce Formation (Figs. 5 - 9). Kimmeridgian deposits are confined to south-eastern part of the studied area (Fig. 5), where they are developed as the Głowaczów Formation: gray marls and marly limestones with numerous bivalve lumachelles. In the Hrubieszów region, they are represented by dolomitic rocks of the Ruda Lubycka Formation (Fig. 8). Portlandian deposits. originally forming rather thin cover of the Kimmeridgian, are lacking at present in the Lublin Coal Basin.