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

High-resolution ammonite, belemnite and stable isotope record from the most complete Upper Jurassic section of the Bakony Mts (Transdanubian Range, Hungary)

Pages: 413 - 433

Authors: ISTVAN FOZY, NICO M.M. JANSSEN, GREGORY D. PRICE

Abstract: This research focuses on the cephalopod fauna and biostratigraphy of the latest Jurassic succession of the Lókut Hill (Bakony Mts, Transdanubia, Hungary). Fossils were collected bed-by-bed from Ammonitico Rosso facies and from the subsequent Biancone type rock. The poorly preserved cephalopods from the lowermost part of the profile, immediately above the radiolarite, may represent a part of the Oxfordian stage. The rich Kimmeridgian ammonite fauna is published for the first time while the formerly illustrated Tithonian fauna is revised. All the successive Kimmeridgian and Early Tithonian Mediterranean ammonite zones can be traced. The highest documented ammonite zone is the late Tithonian Microcanthum Zone. The beds above yielded no cephalopods. Particular attention was paid to the belemnite fauna of over 120 specimens collected under strict ammonite control. Among the belemnite faunas an Early Tithonian, an early middle Tithonian, a late middle Tithonian, and a latest Tithonian assemblage can be distinguished. Thereby, an association is distinguished in the middle Late Kimmeridgian and one that characterizes the Oxfordian-Kimmeridgian boundary beds. The main difference from previously published belemnite data appears to be that the Hungarian assemblages are impoverished with respect to contemporary faunas from Italy and Spain (Mediterranean Province). An isotopic analysis of the belemnites show that the carbon-isotope data are consistent with carbon-isotope stratigraphies of the Western Tethys and show a decrease in values towards the Jurassic-Cretaceous Boundary.

Keywords: Late Jurassic, Hungary, Bakony Mts, biostratigraphy, Ammonitico Rosso, ammonites, belemnites, stable isotopes

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