Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 14. 1989. (Budapest, 1989)

FRAGMENTA MINERALOGICA ET PALAEONTOLOGICA 14. BUDAPEST, 1989 P- 63-72 Middle Eocene transgression and basin evolution in the Transdanubian Central Range, Hungary: sedimentological contributions By A. VÖRÖS (Received December 7, 1988) Abstract: The southwestern part of the Transdanubian Central Range was overflown by the sea in the earliest Lutetian; the predominant rock is foraminiferal limestone. In the northeastern part the transgression began only in the latest Lutetian; coal measures and terrigenous detrital sediments prevail, limestones are subordinate. The subsidence was slow and gradual in the southwest while relatively rapid in the northeast. Deep pull-apart basins probably did not develop before the Late Eocene. INTRODUCTION The bulk of the Eocene formations of the Transdanubian Central Range belongs to the Middle Eocene. By its extensive outcrops, rich fossil content and industrial importance, this group of formations have called the attention of geologists since the last century. The paleogeographical analysis of the Middle Eocene, Lutetian transgression was a favoured subject of several authors, but a sound evaluation was possible after the development of biostratigraohical correlation schemes (e.g. KOPEK, DUDICH and KECSKEMÉTI 1971, HORVÁTH-KOLLÁNYI 1983, KECSKEMÉTI 1982, BÁLDI-BEKE 19 84) only. Nevertheless, the large- scale paleogeographical syntheses published in the last years (e. g. DUDICH and KOPEK 1980, BALLA 1981, BÁLDI and BÁLDI-BEKE 1985) gave strikingly different views and conclusions on the same subject. An important reason of this could be that detailed sedimentological studies did not keep pace with the general progress. Without firm sedimentological and paleoecological basis the paleogeographical synthesis could not be reliable. During the last fifteen years, in cooperation with T. KECSKEMÉTI, I have studied several Middle Eocene sections in the Transdanubian Central Range. My sedimentological investigations have been focused on carbonate rocks, but some aspects of detrital sediments have also been taken into account. Although we have a comprehensive knowledge about the Transdanubian Eocene, our detailed studies have been restricted to two distinct areas: (1) the SWBakony, between Sümeg (Darvas-tó) - Halimba - Kislód - Magyarpolány - Somlóvásárhely, where we have studied surface outcrops and boreholes, and (2) the Oroszlány - Pusztavám lignite district, where we have worked only on borehole sequences (core samples) (Fig. 1).