The Mid-Hungarian Zone is a WSW-ENE trending composite structural unit in the basement of the Pannonian Basin that is made up of displaced crustal fragments (terranes) of South Alpine and Dinaridic origin. In the early stage of the Alpine evolution these fragments were located in various sectors of the NW Neotethys region, representing different paleogeographic settings from passive margin through continental slope to oceanic basement. Middle to Late Jurassic closure of the Neotethys led to the development of a suture zone made up of subduction-related complexes that can be followed all along the strike of the Dinarides. During the Cretaceous compressional stages, nappe stacks were formed from the accretionary complex and the fragments of the previously disrupted passive margin. Eastward extrusion (escape) of the ALCAPA Mega-unit during the Oligocene to Early Miocene led to large-scale displacement of fragments of this nappe stack, transporting them to their present-day position, and resulted in dispersal of the northwestern segment of the suture zone. The paper summarizes the basic characteristics of the dislocated blocks, evaluates their relationships and determines their original setting.
The Senonian succession of the Szilvágy-33 well in the Northern Zala Basin was investigated in order to re-evaluate its chronostratigraphic subdivision and depositional history. The studied sequence begins with the Ajka Formation of reduced thickness and atypical facies. This is followed by the Jákó Formation with the interfingering layers of the Ugod Limestone, and then the approximately 300 m-thick section of the Ugod Limestone which is covered by the Polány Marl. According to the palynologic and nannoplankton investigations, the entire encountered sequence can be assigned to the Campanian. The layers assignable to the Ajka Formation contain the sporomorph assemblage known from the upper section of the Jákó Formation in the Bakony basins, clearly indicating a considerable temporal shift of the lithofacies during transgression. The late transgression demonstrated in the Szilvágy-33 well suggests an elevated paleotopography. In contrast to the former assumptions, the transgression may not have reached the Bakony region via the Zala Basin; rather, both sub-areas were invaded by the sea from the South Alpine pelagic basins.
Authors:Dražen Balen, János Haas and Sándor Kovács
The present issue is devoted to the memory of Professor Jakob Pamić, who for a long time, until his death, was a very active member of the Advisory Board of the Acta Geologica Hungarica and provided great efforts toward a better understanding of the geology of the Pannonian Basin and the surrounding mountain ranges.