International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association


Published: Dec 2002

Pages: 351 - 367


Abstract: This paper presents the Lower Triassic sequence in the Bükk Mountains (NE Hungary). On the basis of the revised macrofossil-collections and previous conodont studies, a biostratigraphic correlation and a chronostratigraphic subdivision of the formations and members is given. Hindeodus parvus (Kozur et Pjatakova), Isarcicella isarcica (Hukriede), Claraia aurita (Hauer), Eumorphotis gr. multiformis (Bittner), Eumorphotis cf. hinnitidea (Bittner), Costatoria subrotunda (Bittner), Eumorphotis kittli (Bittner), Tirolites illyricus Mojsisovics, Tirolites seminudus Mojsisovics, Costatoria costata (Zenker), Rectocornuspira kalhori Brönnimann, Zaninetti et Bozorgnia, Cyclogyra? mahajeri Brönnimann, Zaninetti et Bozorgnia, and Meandrospira pusilla (Ho) are the main index fossils. Two sections, which represent the entire Lower Triassic succession, were studied from a sedimentological point of view. These are the Gerennavar section for the Gerennavar Limestone Formation, and the Lillafüred section for the Ablakoskővölgy Formation, respectively. The sedimentological data and facies interpretations are summarized in facies models. During Early Triassic time the depositional area of the Bükk Mountains were situated in the epeiric shelf of the Western Tethys. The model of the Gerennavar Limestone Formation reflects the high-energy, tide- and wave-dominated shallow shelf, characterized by a protected–stabilized muddy sand flat and a high-energy sand belt. The model of the siliciclastic, lower part of the Ablakoskővölgy Formation indicates a mixed, dominantly siliciclastic shallow shelf with deposition in the coastal, shoreface and transitional zones. The model of the carbonate, upper part of the Ablakoskővölgy Formation refers a storm-controlled shelf with facies representing the whole spectrum from the peritidal–shallow shoals to the low-energy deeper subtidal zone below the storm wave-base. Lithologic and facies comparison of the Lower Triassic succession of the Bükk Mountains to other sequences of the Western Tethyan depositional area reveals many differences, and fewer similarities, which suggests local controls on depositions, that is locally different terrigenous siliciclastic input, different subsidence rate, antecedent topography, and dominance of the local physical regime.

Keywords: Lower Triassic, NE Hungary, Bukk Mountains, stratigraphy, facies interpretation, facies model, fossils

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