New occurrences of Paseky Shale near Podlesí NW of Příbram and microfossils from the Nové Podlesí locality (Cambrian, Holšiny-Hořice Formation, Příbram-Jince Basin)

Abstract

Previously unrecorded occurrences of the Paseky Shale were found in the course of geological mapping at three localities NW of Příbram near Podlesí (Fig. 1). This shale makes a part of the Cambrian Series 2, Holšiny-Hořice Formation in the Příbram-Jince Basin. The shale was documented ca. 250 m S and about 80 m NE of the Malá Dubová hora summit as abundant loose rock fragments (Fig. 2) and soil skeleton (Fig. 3), respectively. An outcrop of the Paseky Shale was found in a small quarry near Nové Podlesí (Figs 4 to 9). The Paseky Shale has a significant position within the geological record of the Barrandian area as it hosts the oldest macrofossil fauna in the Czech Republic, most notably the aglaspid-like arthropod Kodymirus vagans Chlupáč & Havlíček 1965 (Chlupáč – Havlíček 1965, Lamsdell et al. 2013). A microfossil analyses of samples from the quarry near Nové Podlesí has been carried out. The microfossils are relatively sparse and generally rather poorly preserved. The assemblage consists mostly of filaments belonging to the genus Siphonophycus Schopf 1968, emend. Knoll et al. 1991 (Fig. 10 A, D, E, F) ranging from ca. 8 to 50 µm in width. Less common are representatives of Leiosphaeridia minutissima Naumova 1949, emend. Jankauskas in Jankauskas et al. 1989 (Fig. 10 B, C). No other acritarchs were found. Residues further include poorly identifiable fragments of organic-walled microfossils, most likely representing degraded filaments (Fig. 10 G). The studied assemblage is consistent with findings from other localities of the Paseky Shale. However, further relatively rarer components of the microfossil assemblages known from other localities (see Fatka – Konzalová 1995, Kovář – Fatka 2023) are missing. This is most likely due to the low abundance and generally poor preservation of the microfossils at the locality. The general absence of a more diversified acritarch assemblage corresponds to an atypical, restricted marine environment, presumably represented by a lagoonal setting (see Fatka – Konzalová 1995).