Dr. Nagy I. Zoltán szerk.: Fragmenta Mineralogica Et Palaentologica 7. 1976. (Budapest, 1976)

Remarks on the "Intralutetian denudation" The short but very effective sea-level oscillation recorded within the N. perforatus zone requires a réévaluation of the exact date and continuity of the so-called "intralutetian denudation" in the Bakony Mts. The concept of "intralutetian denudation" first appeared in the work by KOPEK and KECSKEMÉTI (1964). According to the initial - rather wide - interpretation this means a single, considerable hiatus between the Lower and Upper Lutetian beds wide-spread in the Bakony Mts. Subsequently the meaning of the concept has slightly changed. The most recent opinion (KOPEK 1972; figs 33, 34, 35) suggest that this single terrestrial period appears typically only in the NE Bakony while its presence in the W-Bakony is slightly, in the S Bakony not at all demonstrable. In our mind the palaeogeographic evolution of the Bakony-area during the Eocene can be characterized by a gradual transgression over a dissected surface of Mesozoic rocks interrupted by regressive periods. Each of the regressive periods could result in denudation and the sensu stricto "intralutetian denudation" at Dudar (NE Bakony Mts.) is perhaps only the most thoroughly explored one and means the period of emergence subsequent to the zone of N. laevigatus. It is remarkable that on essentially the same area (at Veimpuszta) a later period of denudation can be recorded (subsequent to the zone of Assilina spira

) (KOPEK, DUDICH and KECSKEMÉTI, 1969) which is thought to be synchronous with the regressive period presented in this paper. This is proven by the coeval overlying beds (the upper part of the N. perforatus zone); the only difference is that the erosion penetrated more deeply in the Veimpuszta area. It arises as a reasonable assumption that, on the analogy of the aforementioned, the intralutetian denudation (sensu stricto) of the NE Bakony Mts. (at the end of the N. laevigatus zone) can be demonstrated in the W Bakony Mts. as well. Evidences are expected from drilling explorations or from reexamination of earlier drill-cores. The main features of our palaeogeographic picture is in agreement with the earlier one (KOPEK and KECSKEMÉTI, 1964; KOPEK DUDICH and KECSKEMÉTI, 1972.) insofar as during the Middle Eocene the central mass of the N Bakony maintained against the continually submerged S Bakony - its more elevated position while its eastern and western flanks (but probably the others too) were the places of shoreline displacements. Formerly the majority of these oscillations seemed to be local; in our opinion however they can be synchronized and arranged into regional regressive cycles by means of more precise biostratigraphic analysis. In this respect the results of the present study show that within the Lutetian at least two biostratigraphically well established periods of denudation must be taken into account in the Bakony Mts.