Miocen z otworów wiertniczych okolic Skoczowa

Wilhelm Krach


Miocene from bore-holes of the Skoczów region

Top Miocene deposits containing macrofauna were studied from three bore-holes of the Skoczów area near Bielsko: Dębowiec 45, Simoradz 26 and 27. The deposits under consideration are overthrusted by the flysch units. Their thickness is not known but judging from the neighbouring wells, it amounts to several hundred metres. They are grey, silty, marly clays, with numerous sandy and gravelly intercalations. The macrofauna is scant in clays and usually abundant but damaged in conglomerates; it sometimes forms lumachella streaks. The fauna in claystone consists of pelecypods and gastropods with thin shells; the majority of them belong to the benthos, a small part — to the plankton. It is of an autochtonous character and is indicative of quiet and deeper waters. The presence of sandy and conglomeratic parts of cores can be explained by submarine slides with allochthonous organic material, which comes from the littoral zone (littoral, sublittoral). Planktonie gastropods-Pteropoda, of the genus Clio and Vaginella, and a number of benthonic genera with thin shells, among others: Tellina, Ervilia, Corbula, Nucula, Leda, Solenomya, Chlamys, Drillia, Scaphander, Dentalium, are characteristic of deeper environment. According to recent bathymetric disposition of cited genera the depth of the basin amounted to 200 metres. Thick shell molluscs occur in clastic intercalations. They are partly destroyed during redeposition from shallower areas (30—100 m). The salinity of the zone ranges from normal to somewhat brackish as indicated by the presence of Cardium, Cerithium, Melanopsis. Normal salinity remained on the axis of the basin. The studied formations belong to the Badenian (Tortonian, Table 1), probably to its lowest part (Lower Opolian).

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