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- Author or Editor: Olga Piros x
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In the area of the Aggtelek-Rudabánya Mts, limestone and dolomite of reefal and lagoonal facies were formed on a platform, which was continuously deepening from the beginning of the Middle Triassic. The bulk of the limestone is represented by lagoonal formations, extremely rich in dasycladaceans. The reefal formations are of patch reef origin. The almost continuous development and the remarkable abundance of fossils permitted the elaboration of an Anisian-Carnian dasycladacean biostratigraphy. On the basis of investigations 4 assemblage zones could be separated in the Anisian, and 6 in the Ladinian-Carnian. In establishing this biostratigraphy dasycladacean investigations of similar facies areas of the Silica Plateau and the Northern Calcareous Alps were also taken into account.
The Middle Triassic Wetterstein Limestone was investigated on the Feuerkogel, in the eastern Höllengebirge area, Austria. Cephalopod-bearing coquina interbeds consisting predominantly of orthocone cephalopods were found within the dasycladacean inner platform lagoon facies. Based on sedimentological studies the coquina beds are interpreted as storm accumulations. Dasycladacean biostratigraphic data permit assigning the studied succession to the Late Anisian-Early Ladinian interval. Ammonites of age-diagnostic value found in the coquina horizon suggest the Avisianum Subzone of the Reitzi Zone that corresponds to the upper part of the Anisian.
Abstract
In the Pilis Range, NW of Budapest, contemporaneous Upper Triassic platform and basin facies occur. The paper presents the extent and basic characteristics of these facies with interpretation of their depositional conditions, and summarizes the available biostratigraphic data. Based on previous and recent studies a general depositional model is displayed and the history of the basin evolution is outlined. Within the Dachstein Platform an extensional intraplatform basin (Feketehegy Basin) came into existence during the middle part of the Norian. An asymmetric basin was formed, bounded by steep and gentle slopes, respectively. The platform progradation that may have resulted in the termination of the basin began at the gentle margin probably in the latest Norian-earliest Rhaetian.
The 1,200-m-deep Budaörs-1 borehole provided important data for our understanding of the stratigraphy and tectonic setting of the southern part of the Buda Hills. Although previous reports contained valid observations and interpretations, a number of open questions remained. The importance of this borehole and the unsolved problems motivated us to revisit the archived core. The new studies confirmed the existing stratigraphic assignment for the upper dolomite unit (Budaörs Dolomite Formation) as the dasycladalean alga flora proved its late Anisian to Ladinian age assignment. An andesite dike was intersected within the Budaörs Dolomite. U–Pb age determination performed on zircon crystals revealed a Carnian age (~233 Ma), and settled the long-lasting dispute on the age of this dike, proving the existence of a Carnian volcanic activity in this area after the deposition of the Budaörs Dolomite. Palynostratigraphic studies provided evidence for a late Carnian to early Norian age of the upper part of the lower unit (Mátyáshegy Formation). This result verified an earlier assumption and reinforced the significance of the tectonic contact between the upper unit (Budaörs Formation) and the lower unit (Mátyáshegy Formation). Based on structural observations and construction of cross sections, two alternative models are presented for the structural style and kinematics of the contact zone between the Budaörs and Mátyáshegy Formations. Model A suggests a Cretaceous age for the juxtaposition, along an E–W striking sinistral transpressional fault. In contrast, model B postulates dextral transpression and an Eocene age for the deformation. The latter one is better supported by the scattered dip data; however, both scenarios are considered in this paper as possible models.
