Abstract: | This paper presents the results of an investigation into the variability of echinoderm assemblages
from Bathonian ore-bearing clays from Gnaszyn. Remains of Crinoidea, Asteroidea, Ophiuroidea,
Echinoidea, and Holothuroidea have been studied from 38 rock samples. The most common echinoderms
represented are the crinoids Balanocri- nus berchteni and Chariocrinus andreae and a few species of
the holothurian genera Priscopedatus, Calclamna, Staurocaudina, Eocaudina, Achistrum, Theelia and
Hemisphaeranthos. The echinoderms from Gnaszyn show var- ious life strategies: benthic or
epibenthic forms, sessile sestonophages (Crinoidea), motile macrophages (Asteroidea) and
detritivores (Asteroidea, Ophiuroidea, Echinoidea), infaunal and epifaunal detritus feeders,
sediment feeders or rake-feeders (Holothuroidea). Their presence suggests well oxygenated and
presumably relatively cold bottom marine waters. The parts of the Gnaszyn section around concretion
horizons and characterized by the ubiquitous occurrence of the holothurian Theelia and echinoids
were deposited during phases of optimal living conditions with sufficient influx of plant detritus
and good oxygenation of the sea bottom. These parts commonly host echin- oderm associations
dominated by crinoid remains, which occasionally are still articulated (or disarticulated but re-
maining intact) – this points to a quiet environment with normal oxygenation of the
bottom waters but anaerobic/dysaerobic conditions in the sediment. |