Małżoraczki środkowego miocenu (badenu) z otworu Broniszowice (SW Polska)

Abstract

W otworze Broniszowice (śląska część zapadliska przedkarpackiego) stwierdzono zespół małżoraczków starszego badenu. Wyróżniono 20 gatunków należących do 15 rodzajów z 9 rodzin rzędu Podocopida. Prześledzono ilościowy udział i znaczenie poszczególnych taksonów w badanej populacji. Dominacja okazów z rodzaju Cytheridea, Aurila i Loxoconcha sugeruje środowisko infralitoralne, stanowiące płytszą część strefy sublitoralnej (nie przekraczającą 50 m).

THE MIDDLE MIOCENE (BADENIAN) OSTRACODS FROM BRONISZOWICE BOREHOLE

(SW POLAND)

This article results of micropalaeontological and biostratigraphical analysis of ostracod assemblage from samples (depth 99.80-98.10 m), taken from the Broniszowice borehole (SW Poland -

Silesian part of the Carpathian Foredeep). It was the first study of this faunal group from Fore-Sudetic Region and one of few - up till now - studies of Miocene ostracods from Polish area. 20 species were distinguished in studied assemblage, among which the most frequent were specimens of genera Cytherdea and Aurila (65% of all population).Variable valves preservation and species frequency within population indicated infralittoral environment with varying dynamics and significant optimum at depth of 20-40 m (shallower part of sublittoral zone). In examined assemblage, co-occurrence of species: Acanthocythereis hystrix and Eocytheroptheron inflatum, which are, according to R. Jiricek (1983), typical for differents zones (NO-7 and NO-8), causes the evoluation of zonal range very difficult. According to faclt Acanthocythereis hystrix was noted in Middle Badenian of Central Poland (J. Szczechura, A. Pisera, 1986) it could be assumed, that ostracod assemblage from Broniszowice represents Older Badenian, not necessary Lower Badenian assemblage.

On the Parathetys area described ostracod assemblage has most similarites to assemblage known from the Vienna Basin, studied by r. Cicha (1978) from Zidlochovice (facies stratotype of Moravian) and by A. E. Reuss (1850) from Kostel (this work was revised by J. Zelenka, 1985). On the Thetys region similar assemblage was described by W. Sissingh (1976) on Crete and referred to Serravalian – Torton.