Stratygrafia młodszego trzeciorzędu niecki orawsko-nowotarskiej na podstawie makrofauny słodkowodnej i lądowej

Abstract

STRATIGRAPHY OF THE YOUNGER TERTIARY IN THE ORAWA – NOWY TARG BASIN ON THE BASIS OF FRESH-WATER AND CONTINENTAL MACROFAUNASummaryTertiary continental deposits of the Orawa –NowyTargBasinwere described for the first time by F. Foetterle in 1851. Yet, until recently, the fauna of these deposits has not been examined and the age of these rocks has not been defined in detail. The present study is based on rich lithological and palaeontological material obtained from two boreholes: in Czarny Dunajec and Koniówka. Upper Tertiary deposits drilled in Czarny Dunajec measured922 min thickness, while Miocene and Pliocene rocks drilled in Koni6wka were452.30 mthick (Fig. 1).In borehole Czarny Dunajec IG-1, these deposits represent a monotonous clayey series with intercalations of brown coal. In some places there are quite frequent fragments of charred plants and few deformed shells of mostly continental mollusks and some fresh-water molluscs. Of the 33 species determined here 30 represent land forms and only three species have been defined as fresh-water forms. This shows that it was rather the continental type of deposition that prevailed here.Thus we can assume that, in the Neogene, the Orawa –NowyTargBasinformed and extensive intramountainous basin of continuous subsidence, filled with clastic material which was carried by atmospheric waters from the surrounding mountains.In this borehole, intercalations of deposits with fresh-water molluscs were encountered at a depth of 159.30 –511.00 m. This shows that in some periods the subsidence of the basin was quicker than the accumulation of the deposits and, as a result of this, swampy environments were formed.Rocks with Pliocene land gastropods occur at a depth of 28.00 – 65.30 m(Podczerwone Beds), while Upper Miocene deposits with fauna (Koniówka Beds) occur at a depth of 65.30 – 230.00 m. Of the 14 species of gastropods identified here, 10 species belong to the Upper Miocene, two species extend from the Upper Miocene to the Lower Pliocene, while two species range from the Middle to the Upper Miocene. Two species represent fresh-water forms while 12 species have been identified as land gastropods. Middle Miocene rocks (Orawa Beds, 230.00 – 488.50 m) are poor in fauna, which is represented only by five Middle Miocene species of land gastropods. Lower Miocene deposits (Czarny Dunajec Beds, 488.50–950.00 m) contain 12 species of land gastropods and one species of fresh-water lamellibranchs, Pisidium sp. All of these species, except for the Lower Miocene Helix devexa Reuss, range from the Upper Oligocene to the Lower Miocene.Similar conditions have been found to occur in borehole Koniówka IG-l. However, the thickness of Tertiary deposits here is only half as big as in borehole Czarny Dunajec IG-1 and the number of gastropod species is also smaller.