Acta Geologica 32. (1989)

1-2. szám - G. Császár: Transgressive Urgonian sequence with black "pebbles" from the Villány Mountains, Hungary

Acta Geologica Hungarica, Vol. 32/1--2, pp. 3—29 (1989) TRANSGRESSIVE URGON1AN SEQUENCE WITH BLACK "PEBBLES" F RUM THE VILLÁNY MDUNTAINS, HUNGARY G. CSÁSZÁR Hungarian Geological Survey, Budapest The Urgonian Lower Cretaceous sequence explored in the Nagy­­harsányhegy quarry in a thickness of 200 m is reviewed. Based on the thin section investigations carried out in the lower 70 m sec­tion of the four units of member rank 9 facies types are discussed. Based on the poorish fauna and of the macroscopic characteristics the changes of salinity oscillating between the freshwater and marine conditions are determined. The interpretation of formation of the frequent black limestone breccia considered as an element of the Lofer-cycle is dealt with in detail. Starting from macroscopic characteristics (texture, structure, fauna) the paleo­­geographic reconstruction of the area is carried out. In this re­spect the existence of an external and of an internal lagoon were determined. It is emphasized that the investigations in progress have stressed the remarkable difference between this occurrence and the base strata of the neighbouring outcrops (Hauterivian and Albian, respectively). Keywords: Villány Mountains, carbonate sedimentology, Urgonian facies, Lofer-cycle, Valanginian-Albian microfossil Geological setting The Nagyharsány Limestone Formation developed in the structural zone of the Villány Mountains has a special position among the varied Urgonian formations of different age of Hungary (Fig. 1). The formation that can be traced by boreholes beneath the Tertiary formations as far as the Ki­rályerdő in Transylvania with some breaks (Patrulius, D., 1976; Fülöp, J., 1966) overlies the youngermost incomplete Jurassic sequence, i.e. the super­­thick Kimmerdgian to Lower Tithonian shallow marine limestone by erosional unconformity (Fülöp, J., 1966) and the similar Lower Cretaceous limestone in the Danube-Tisza Interfluve (Bérczi-Makk, A., 1987). Between the underlying strata and the Urgonian limestone bauxite is found both in the Villány Address: Géza Császár: H-1143 Budapest, Népstadion út 14, Hungary Received: 7/12/88 Akadémiai Kiadó, Budapest

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