The Upper Aptian to Lower Albian Tata Limestone Formation consisting of brown-grey bioclastic crinoidal limestone presumably represents the first unconformable formation, which recorded early deformation events of the Alpine cycle. The base of the Tata Limestone is affected by erosional features accompanied by significant breccia bodies. Reconstruction of the paleomorphology of the basin bottom supported by paleoecological (e.g. water depth) data shows (in the recent orientation) at least five northwest–southeast trending zones with significant erosional features and accompanied by coarse-grained graded breccia in a more clayey matrix (e.g. Cseh-1 borehole). These elevations were uplifted above deeper basins filled with crinoidal limestone. The geometry of the uplifted units is asymmetrical, anticline-like and the deeper depressions have a syncline-like structure. According to previous works to the anticline-like morphology of the uplifted zones and to the transport direction of the coarse breccia clasts, these uplifted units were possibly formed by thrusting, in a compressional regime. The differences in the thickness of the crinoidal limestone and the breccia interbeds show synsedimentary character of these movements. In the borehole Cseh-1, large limestone fragments appear already in the Sümeg Marl Formation and they are present throughout all the Tata Limestone sequence. This fact indicates that the tectonic movements started in the Barremian and continued during the whole Aptian.