Dr. Nagy I. Zoltán szerk.: Fragmenta Mineralogica Et Palaentologica 5. 1974. (Budapest, 1974)

GEOLOGICAL SETTING OF THE AREAS STUDIED The oldest rock in the studied areas is the 420 m thick Middle Eocene marl and claymarl series with limestone and sandstone intercalations, cut in Borehole Cinkota-6. The fauna is poor, with Nummulites variolarius LAMARCK in the lower part (determination by KECSKEMÉTI T.). The upper part can be correlated with the Upper Lutetian of Budakeszi, on the basis of the occurrence of a globular Elphidium species (MAJZON 1966). The Upper Eocene is represented by marls and calcareous marl beds with limestone intercalations in some places. Its lower part belongs the Globigerinatheca semiinvoluta Zone and agrees stratigraphically with the Nummulites-, Discocyclina-, Lithothamnium-bearing Limestone of the Buda Mounts. The rock represented by Core No. 19. is the deep-water equivalent of the Bryozoan Marl of Buda. It is overlain by the beds of the Buda Marl. (Catapsydrax gortanii gortanii Zone). Becouseofthe rare core sampling the Uppermost Priabonian and the basal Lower Oligocène is unknown. In Borehole Rózsadomb-8/3 the beds of the Eocene/Oligocene boundary could be studied. The characteristic banded structure of the Tard Beds occur as deep as 67,2 m (KRrvÁN P., oral communication) in the Upper Eocene Turboratalia increbescens Zone. (According to the opinion of the Oligocène Committee of the Hungarian Stratigraphical Comission the formation-definition of the Tard Clay differs from the original designation of MAJZON (1940). By this definition the Tard Beds refers to laminated, finely stratified clays and claymarls with common tuffitic and sandstone intercalations. This formations mainly suggests euxinic facies; however planktonic fossils, leaf imprints and fish remains are quite common. On the basis of this new definition based exclusively on pétrographie features I had to modified my earlier opinion: the entire Buda Marl member ranges into the Upper Eocene. The portion named as "Horizon of small Globigerinae" (SZTRÁKOS,1972) is equivalent to the lower part of the Tard Clay. (Earlier the boundary of the Buda Marl and the Tard Clay was laid out on the basis of the disappearance of the foraminifers.) The upper part of Borehole Rózsadomb-8/3, between 18, 2 and 38, 2 m yielded redeposited foraminifers from the Buda Marl and the Bryozoan Marl of Buda (Nummulites ssp., Discocyclina ssp.

, Turborotalia increbescens

, Globigerina ampliapertura

, etc.). The transportation of these fossils can be due to the infra-Oligocène denudation. The Kiscell Clay is generally represented in the studied area. It is a mightly (400 to 1000 m) formation, with the increasing thicknesses towards Budapest. In the area between Budapest and the southern foreland of the Bükk Mts. the shallow water facies tends to thicken out in southern direction, i.e. towards the so-called "Paleogene Line", (the lower part of the Kiscell Clay contains more sanstone intercalations here, and the benthonic foraminifers suggest sublittoral - deep-sublittoral facies), while in the northern areas bathyal facies occur with rich planktonic foraminiferal fauna. In Late Rupeliantimes the shore-line shifted to the south, thus the deep-sublittoralfacies sediments were substitued by bathyal ones. There are some facts suggesting contemporaneous uplift in Fig. 1. Sketch map of the studied localities and boreholes. - 1. ábra. A terület ésafúrások vázlatos térképe.