The “lost” uppermost Bajocian (Middle Jurassic) beds of J. NOSZKY Jr. in the Közöskút Ravine, Bakony Mts, Transdanubian Range, Hungary

Abstract

On the basis of his studies in the 1940s, J. NOSZKY Jr. . published stratigraphical data on the Middle Jurassic of the Közöskút Ravine of the Bakony Mountains. In several publications he reported the presence of Bathonian beds, based on the ammonites he found in the area. After a period in which his material was apparently “lost”, several decades later it was rediscovered in a repository of the Hungarian Geological and Geophysical Institute and thus became available for study. It turned out that all of the ammonites which NOSZKY’s found belong to Late Bajocian species, partly to forms which, in his time, were regarded as indicators of the Bathonian. The three most important species from the NOSZKY collection are: (Cadomites [C.] deslongchampsi, Vermisphinctes [S.] stomphus and Dimorphinites [D.] dimorphus) These are described briefly and figured in the present study. Although it is impossible to reconstruct the original position of these ammonites in the bed(s) exposed in NOSZKY’s (due to the lack of the original field notes), the indicated youngest stratigraphic record, i.e. the Parkinsonia parkinsoni Zone, represents an important contribution which is still relevant today. With this datum the heterochroneity of the calcareous/siliceous sedimentation change in the Bakony Mountains can be completed: namely, the former data on ?Late
Toarcian – Early Aalenian (Úrkút), Early Bajocian (Bakonycsernye), and Late Batho ni an (Gyenespuszta) can now is supplemented with this Late Bajocian one. The corrected (Late Bajocian) age determination of the possibly youngest limestone bed(s) in the Közöskút Ravine confirms the former conclusion that the only hitherto known locality of Bathonian ammonite-bearing limestones in the Bakony Mountains is that in Gyenespuszta.