Acta Palaeontologica
Polonica 42, 2, 333-359 (1997) Dzik, J.,Sulej, T., Kaim, A. & Niedwiedzki, R. Abstract. Five types of brachiopod bivalve
assemblages occur in Terebratula Beds and in the lower part of the Karchowice
Beds (Middle Triassic, Muschelkalk) from the Strzelce Opolskie Quarry (Upper
Silesia). These are: (1) Brachiopod Coquina Assemblage dominated by the
terebratulid brachiopod Coenothyris vulgaris; (2) Crumpled/Wavy
Limestone Assemblage including bivalves and brachiopods; (3) Bivalve Coquina
Assemblage dominated by pseudocorbulid bivalves; (4) Hardground Assemblage
dominated by the brachiopod Tetractinella trigonella; and (5) Crinoid
Limestone Assemblage dominated by crinoid columnals and the brachiopod Punctospirella
fragilis. The distribution of the assemblages correlates with the
eustatically controlled lithological variation in the carbonate dominated
sequence of the Upper Silesian Muschelkalk. The brachiopod coquinas are
parautochtonous remnants of terebratulid banks which thrived during the high
bioproductivity but low oxygen conditions. Those conditions were caused by the
biogenic influx generated from the terrains flooded during the Middle Triassic
transgression. During the regressive phase, that resulted in the gradual
decrease in bioproductivity and parallel increase in oxygen levels, the
terebratulid banks were replaced by pseudocorbulid banks. With the further
regression and thus, the further increase in oxygen level pseudocorbulid banks
were replaced by the assemblages indicative of well oxygenated oligotrophic
environments (Hardground and Crinoid Limestone Assemblages). The observed
changes in the faunal composition reflect mainly differences in metabolism and
feeding strategy among dominant taxa. |