Late Cenozoic Tectonics of the Pannonian Basin System
Published:January 01, 1988
The Miocene evolution of the Carpathian-Pannonian system appears to have been controlled by events within the adjacent Alpine mountain belts. Early Miocene initiation of northward to eastward thrusting in the outer Carpathians is best ascribed to the eastward escape of the Pannonian continental lithospheric fragments) away from the zone of collision in the Eastern Alps. The subsequent “back arc” extension in the Pannonian basin system in middle-late Miocene time was coeval with the late stages of thrusting in the adjacent Carpathian belt. Net east-west extension within the basin system can be related both to the arrangement of continental lithospheric fragment boundaries outside of the Pannonian area, which prohibited continued convergence of the Pannonian fragment with Europe, and to the continued subduction and shortening beneath the East Carpathians at the same time.
Basin extension was heterogeneous and diachro-nous throughout the Pannonian basin system. Variations in basin development were intimately related to contemporaneous thrust belt activity in the Carpathian Mountains. Extension occurred along a conjugate system of strike-slip faults that connected areas of coeval extension to one another and to coeval areas of shortening within the Carpathian thrust belt, thus providing a mechanical link between basin extension and thrusting. The style of extension at depth was controlled by the geometry of the thrust belt at depth and the distance from the thrust front.
The style of sedimentation within each basin was also influenced by the proximity of each basin to the thrust front. Basins located near the thrust belt contain thick synextensional fault-bounded sedimentary rocks overlain by thin postextensional sediments. The normal faults reach nearly to the surface. Basins located far from the thrust belt contain thin sequences of synextensional fault-bounded sedimentary rock sequences overlain by thick sequences of postextensional, unfaulted, flat-lying sedimentary rocks. These differences can be explained by differences in the thermal subsidence rate of the basement after extension and by the proximity of each basin to the sediment sources in the Carpathians.
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The Pannonian Basin: A Study in Basin Evolution
The Pannonian basin system is an integrap part of the Alpine mountain belts of east-central Europe. It is completely encircled by the Carpathian Mountains to the north and east, the Dinaric Alps to the south, and the Southern and Eastern Alps to the west. In 1912, Kober defined the Pannonian basin as one of the type “Zwischengebirge,” a relatively un-deformed region characterized by block faulting and situated between externally vergent thrust belts. More recent studies using subsurface data have shown that the Pannonian area was extensively deformed by Mesozoic thrusting and subsequently disrupted by a complex system of Cenozoic normal and wrench faults. Thus, the Pannonian “massif” has undergone several types of deformation, which are partly hidden by a thick sequence of sedimentary rocks of Neogene-Quaternary age. The Pannonian basin is actually a system of small, deep basins separated by relatively shallow basement blocks. The Neogene-Quaternary sedimentary rocks exceed 7 km in thickness in some areas, and the basin system (including the Transylvanian basin) is about 400 km from north to south and 800 km from east to west. It is currently interpreted by most workers as a Mediterranean back arc extensional basin of the middle Miocene age. The Carpathians, Eastern Alps, and Dinarides, which surround the Pannonian basin, are the result of Mesozoic and Cenozoic continental collision between Europe and several continental fragments to the south, including Africa. Thrusting was direted outward from the present Pannonian basin toward the European platform and the Adriatic region. In all the orogenic belts, the interior parts of the thrust belts were deformed in Mesozoic time, while the outer parts were deformed in Tertiary time. The volume presents 26 papers and eight regional maps resulting from a joint five-day symposium held in Veszprem, Hungary, in 1982 entitled “Evolution of Extensional Basins within Regions of Compression with Emphasis on the Intra-Carpathian Region.” The symposium was sponsored jointly by the Hungarian Oil and Gas Trust, the Hungarian Geological Survey, and the U.S. National Science Foundation.