Organic microfossil assemblages from the late Ediacaran rocks of the Małopolska Block, southeastern Poland

Abstract

 The results of palynological investigations of the oldest siliciclastic strata recognized in the Małopolska Block, situated in southeastern Poland, within the Trans-European Suture Zone (TESZ), are summarized in this paper. Siliciclastic flysch-type rocks without macrofossils have been encountered in over 1000 boreholes within the Małopolska Block, below Paleozoic, Mesozoic, and Cenozoic deposits of various ages (from Ordovician up Miocene). The lithostratigraphy of the pre-Ordovician basement in the Małopolska Block is not fully known. Thin tuffs or tuffites layers have been found in many sections of these rocks. In some of the boreholes (e.g., Książ Wielki IG 1), a late Ediacaran age has been determined for a tuffite interlayer of the rocks underlying Ordovician strata, by U-Pb dating of zircons recovered from that tuffite, that indicated 549 ±3 Ma. This article describes the palynology of samples from twelve selected profiles which contained recognizable organic microfossils, in various states of preservation. The associations recovered are dominated by small spherical forms, without any ornamentation, belonging to the Leiosphaeridia, and by fossil cyanobacteria represented by straight or coiled thread-like fragmentary specimens. Similar organic microfossil associations, with poorly differentiated species and genera, are known from many late Ediacaran occurrences.