Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)

Lydite rocky-bottom (Upper Cretaceous) at Hostouň near Kladno


Jiří Žítt, Olga Nekvasilová

Geoscience Research Reports 33, 2000 (GRR for 1999), pages 89–91
Map sheets: Kladno (12-23)

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In the southeastern vicinity of the Hostouň village near Kladno (Fig. 1), a new occurrence of phosphalic crusts and cememed epibionts of the Late Cretaceous age has been found. Relics of phosphutic crusts around 1 mm thick occur on abraded surfaces (Fig. 2) of a small body of Proterozoic silicite (lydite), which formed an elevated part of the rocky bottom in the Late Cretaceous sea. Remains of large agglutinated forammifera Bdelloidina cribrosa (Reuss) of unknown relationship to phosphatic crusts (poor preservation) were also found attached to this surface. The rock surface is overlain by marly deposits of the Bílá hora Formation containing rare macrofauna (Siereocidaris sorignett (Desor). S. vesiculosa (Goldfuss), a. o. Hostouň and the other localities of the same phenomena previously reported from this area [Žákova skála. Tuchomérice-Kněžívka, T.-Pazdema, Číčovice-Čcmovičky, Svrkyní, Vrapice, Velká Dobrá, and Středokluky; see ŽÍTT (1993), ŽÍTT and NEKVAS1LOVÁ (1990, 1992, 1997), and ŽÍTT ct al. (1999)] evidence large areal extent of phosphogenic environment and similarities of subséquent sedimentary conditions. Ali the localities beiong to the area of Unhošť-Tursko High, a physiographic elevatory structure which controlled Sedimentation and distribution of faunal communities dorm g the carly Late Cretaceous times west and north of Prague.