Faunal dynamics of bivalves and scaphopods in the Bathonian (Middle Jurassic) ore-bearing clays at Gnaszyn, Kraków-Silesia Homocline, Poland

Abstract

ABSTRACT Kaim, A. and Sztajner, P. 2012. Faunal dynamics of bivalves and scaphopods in the Bathonian (Middle Jurassic) ore-bearing clays at Gnaszyn, Kraków-Silesia Homocline, Poland. Acta Geologica Polonica, 62(3), 381- 395. Warszawa. The environment at the Gnaszyn section - as deduced from bivalve and scaphopod dynamics - was controlled by the substrate consistency and possibly oxygen deficiency near the sediment-water interface and/or oxygen content fluctuations. The middle part of the section dominated by nuculoid and corbulid bivalves and Laevidentalium -type scaphopods probably reflects a soupy substrate and possibly oxygen deficiency in the sediment. Slightly coarser and better-oxygenated silts in the upper and lower parts of the section offered a less soupy substrate consistency, allowing the development of communities dominated by astartids, byssate bivalves, and Dentalium - and Plagioglypta-type scaphopods.