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Stratigraphic analysis of the "Urgonian" complex in the Butkov Quarry, the Manin Unit (Western Carpathians)

Fekete K.

Geology, Geophysics and Environment

2012

Vol. 38, no. 4

469--470

The Manin Unit belongs to units with Central Western Carpathians affinity and was incorporated into the Paleo-Alpine Acretionary Belt. The deposits of Manin, Klape and Drietoma units originated between the PKB Zone and Peripieninie deepwater fault (Mahel 1980). Tectonically, these units were created in the foreland of a transferring block of the Central Western Carpathians (Rakus & Hok 2005). From the lithological point of view the Manin Unit can be divided into two groups of sedimentary sequences: the first one, the Manin - Butkov Group (Rakus 1977), which is built up mostly of hemipelagic Upper Jurassic - Lower Cretaceous marly limestones; and the second one, the Podmanin Group (Kysela et al. 1982), consisting of Albian to Maastrichtian flysch and pelagic rock complexes. The most characteristic massive set of Barremian - Lower Albian Urgonian limestones is developed in Manin and Podhorie formations (Vasicek et al. 1994). The recorded Albian stratigraphic hiatus within the Manin Unit was followed by rapid deepening of this sedimentary area and onset of the pelagic deposition of dark marls of the Butkov Formation. The Manin Formation is developed in complex of mainly gray to light gray massive organogenic limestones with numerous Barremian to Albian fossils of foraminifers (Orbitolina), crinoids, echinoids, molluscs, ostracods, corals and calcareous algae. Organodetritic bituminous limestones with dark grey cherts are typical of the Barremian - Lower Aptian Podhorie Formation. In microfacies, the fragments of foraminifers (Hedbergela), molluscs and crinoid ossicles are the most frequently identified bioclasts (Borza et al. 1987). In the Butkov Quarry, within the Manin Formation three lithological sections were sampled, which were used for the biostratigraphic analysis. The lower parts of the sections consist of grainstones, pelbiointrasparites, with dominance of recrystallized peloids and intraclasts. Fragments of foraminifers, corals and sponges are less common. Microborings of blue green and green algae were observed in bioclasts, which indicate deposition within the photic zone (up to 75 m), (Budd & Perkins 1980). In the upper parts of the sections only biomicrite wackestones occur with dominant increase of bioclasts. Biostratigraphically important foraminifers (Globigerina, Textularia, Miliolida, Orbitolina) are common.They belong sometimes to rock-forming elements, especially in the Lower Cretaceous open shelf and deep-shelf deposits. Fragments of brachiopods, echinoids, bivalves and gastropods were also identified. The limestone sedimentation in the Manin Unit in Manin - Butkov Group ends with typical hardground (Rakus 1977), which terminates the Jurassic - Lower Cretaceous sedimentary cycle. Total thickness is variable and ranges from about 50 m (Butkov Quarry) to 120 m (Manin Strait).