STUDIUM SPODNOBADENSKÝCH BAZÁLNÍCH KLASTIK V OBLASTI PODZEMNÍHO ZÁSOBNÍKU PLYNU LOBODICE

Abstract

The depositional environment and the provenance of the Lower Badenian basal clastics in the area of Lobodice subsurface gas storage were described during the studies of these sediments.Drill cores of Lobodice wells were studied in the total length of 110 m for the purpose of depositional environment evaluation. The textures and structures were described on these cores and on this basis three lithofacies were recognized. The lithofacies A is represented by grey matrix supported, granule conglomerate, very poorly sorted. This lithofaces has been interpreted as the product of deposition of a coarse grained delta. The lithofacies B is formed by fine and medium sandstone with ripple cross lamination, very well sorted sandstone. This facies was interpreted as the result of a relatively low energy of traction current, probably deposited in marine environment. The lithofacies C is formed by greyish clay siltstone, locally with planar lamination and common bioturbation. The lithofacies C was interpreted as the product of deposition in the off shore condition (outer part of the shelf?).The results of pebble analysis and analysis of the chemistry of garnets and rutiles were used for the evaluation of the source areas of the Lower Badenian basal clastics.Pebble analysis shows that the studied Lower Badenian clastics are polymict. Grey limestones dominate in the pebble spectra and also oft en represent the largest clasts. Light-coloured limestones, shales and graywackes (most probably Culmian), quartzes and dolomites are relatively common. The content of pebbles of crystalline rocks is relative low. These results indicate the prevalence of sedimentary rocks in the source area and/or recycling of the source material. This results together with garnet and rutile analysis point to the source from the Culmian rock of Drahanská Vrchovina Upland and Nízký Jeseník Highland (especially the rocks of the Myslejovice Formation) and also probably from the Carpathian Flysch Belt.