Lingulate brachiopods across the Kačák Event and Eifelian-Givetian boundary in the Barrandian area, Czech Republic

Abstract

ian marine sedimentary succession of the Barran dian area in Central Bohemia is a classic area of the Devonian stratigraphy and palaeontology. It is the famous, rich and unique source of diverse and well-preserved fossils for more than one-and-half century (e.g. Barrande 1847, 1848, 1852, 1879). Palaeontology and history of its investigation research was reviewed many times (Chlupáč 1984, 1996, 2003 and reference herein). The present concept of stratigraphy of the Devonian sediments at Koněprusy is based on series of early studies of Chlupáč (1955, 1956, 1957, 1959) supplemented by contributions devoted to various aspects of this unique area (Chlupáč 1983, 1996, 2003; Hladil 1995). The youngest lithostratigraphic unit preserved as erosional remnant in the Koněprusy area are calcareous sandstones and shales having poor remains of terrestric flora referred to the Roblín Member of the Srbsko Formation (uppermost Eifelian to ?Givetian) (Svoboda & Prantl 1949; Kukal & Jäger 1988; Chlupáč 1998a, 2003). In the recently protected geological site at abandoned Jirásekʼs Quarry (Fig. 1), the small outcrop with unique contact of the Acanthopyge Limestone (Eifelian) with the Srbsko Formation (Givetian) was studied by Hladil et al. (1991, 1992). The youngest marine macrofauna has been observed in the limestone bed 46 above ca. 0.7 m thick interval of dark limestone (UDI: Upper dark interval = bed 45 after Hladil et al. 1991). Tabulatomorphs and stromatoporoids dominated by Caliapora ex gr. battersbyi (Milne-Edwards & Haime, 1851) from the bed 46 indicate the Eifelian–Givetian boundary interval (Hladil 1993). The UDI is correlated with the shallow water to slope equivalent of shales of the Kačák Member, Srbsko Formation. The UDI is single available section in which Eifelian–Givetian boundary is developed in a carbonate succession in the Barrandian. The fauna of UDI is poorly known, only conodonts, dacryoconarids and microvertebrates were determined. The shelly fossils are generally rare and extremely fragmental. Presence of bryozoans, brachiopods, trilobites, ostracods, forami nifers, and crinoids has been stated, but these groups were not studied so far (Hladil et al. 1991, 1992; Budil 1995).