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1 2006

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Zeillerid brachiopods from Upper Jurassic olistholiths (South Carpathians, Romania)

Lazar I., Sandy M.

Volumina Jurassica

2006

Vol. 4, no. 1

238-239

The Lower Cretaceous formations that crop out on the eastern slope of the Bucegi Mountains comprise some beds containing the Upper Jurassic limestone blocks, described by Patrulius (1954) as olistholiths. These olistholiths are well represented in outcrops near Sinaia, Moroieni, Cernatu, Purcareni. The Middle and Upper Jurassic deposits are recognized in the southern part of the Purcareni locality. The Middle Jurassic deposits include here sandstones, calcarenites and marls with Posidonia alpina, and the Upper Jurassic - the reef limestones. In the Purcareni-Zizin-Tirlungeni area, the Lower Cretaceous (Barremian-Aptian) deposits are conglomerates, breccias, sandstones and marls of the Piscul cu Brazi Formation. This formation includes several Upper Jurassic reef limestone blocks, each of them of a volume around 100-200 m3. The Piscul cu Brazi Formation belongs to the sedimentary cover of the Ceahlau Nappe of the External Dacides of the Carpathian Orogen. The Outer (External) Dacides represent a group of units, which proceed from a Jurassic - Lower Cretaceous paleo-rift, developed within the European continental margin. The olistholiths, especially those from Purcareni, contain a very rich reef assemblage with corals, pachiodont bivalves, gastropods, brachiopods, galatheids, decapods crustaceans, crinoids and echinoids. Murgeanu et al. (1959) and Graf (1975) summarized the previous researches on the geology and palaeontology of this area. The brachiopods are very abundant (a large number of individuals in different growth stages) within this benthonic assemblage, represented mainly by Zeillerina sp. and other terebratulids, including large specimens (2 cm length) of "Terebratulina". The preservation of Zeillerina shells is very good. Shell endopunctation is well preserved. The internal features of a few specimens have been investigated and are consistent with those of the typical representatives of Zeillerina. These include a pedicle collar and dental lamellae in the ventral valve, a median septum and horizontal hinge plates in the dorsal valve.