Stratigraphic and sedimentological analysis of the Upper Cretaceous sequence of the Zala Basin on the basis of the investigation of the Szilvágy-33 well

Abstract

The Senonian succession of the Szilvagy-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 Jako 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 Polany 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 Jako Formation in the Bakony basins, clearly indicating a considerable temporal shift of the lithofacies during transgression. The late transgression demonstrated in the Szilvagy-33 well suggests an elevated paleotopography. In contrast to the former assumptions, the transgression may not have reached the...