Middle–Late Triassic conodont evolutionary events as recorded in the Triassic basinal deposits of Hungary

Abstract

This paper focuses on the results of conodont biostratigraphic investigations of Middle–Upper Triassic basinal
deposits of Hungary carried out by the author between 1974 and 2010 are presented in this review. Conodont-bearing
basinal facies occur in different stratigraphic intervals in the different tectonostratigraphic units of Hungary:
1. In eupelagic facies related to the appearance of pelagic deposits in the different units of the Aggtelek–Rudabánya
Mts, from the Pelsonian to Sevatian (the Rhaetian is not proven here biostratigraphically). The eupelagic conditions are
marked by the immediate appearance of gladigondolelloids and and, for example, by the presence of the G. szaboi lineage
in the Illyrian or of the G. auriformis group in the Julian s.s.
2. In open intrashelf basin facies in the Bükk Unit of NE Hungary, represented by grey, cherty limestones (Felsőtárkány
Limestone Group); these occur from the base of the Carnian (Metapolygnathus. diebeli zone) to the Rhaetian.
3. From the Pelsonian to Julian in the Balaton Highland, with the onset of eupelagic conditions from the A visianum
Subzone of the Reitzi Zone, as indicated by the mass occurrence of gladigondolelloids and representatives of the
Gondolella szaboi – Gondolella trammeri lineage.
4. In some local, more or less restricted intrashelf basin environments from the Middle Carnian to the Rhaetian in
other parts of the Transdanubian Range.
5. In the upper part of the Pelsonian (Binodosus Zone) of the Mecsek and Villány Mts of the Tisza Megaunit, here
only the presence of the Gondolella bulgarica group is evident, whereas gladigondolelloids and neospathoids are entirely
missing (although the latter are still present in the Binodosus Zone of Balaton Highland). This is in accordance with the
Peritethyan character of the Triassic of the Mecsek Zone.
Different types of biozones were applied. They are based either on gondolelloid or metapolygnathoid evolutionary
lineages, partly as proposed by earlier authors. Due to the scarcity of metapolygnathoids, a gondolelloid zonation has been
used for the eupelagic Triassic of the Aggtelek–Rudabánya Mts of NE Hungary and for the Ladinian (and possibly to the
earliest Carnian?) The facies control on the FAD and LAD of some “zonal index” forms has become evident. For example,
this can be observed for the FAD of Metapolygnathus hungaricus (Curionii Zone or Gredleri Zone), or the FAD of
Gondolella polygnathiformis(together with the Metapolygnathus diebeli group in the Balaton Highland, or after them in the
Aggtelek–Rudabánya Mts or in the Southern Alps). Facies control on the FAD and LAD of Late Carnian to Early Norian
taxa was minimal, and the biozones elaborated for the Hallstatt facies of the Northern Calcareous Alps and correlated with
ammonoid biozonation by KRYSTYN could easily be applied also in NE Hungary as well. On the other hand, a Gondolella
biofacies prevailed in the Middle to Late Norian, thus hindering the application of metapolygnathoid zones.