Secondary Heating of Vitrinite: Some Geological Implications
Published:January 01, 1988
Vitrinite reflectance data in Hungary are mainly used for hydrocarbon exploration in the Neogene basins. However, enough data are available from secondary reworked vitrinite populations to help determine the source areas and maturation history of older reworked sediments within the Neogene basins. This reworked material is derived mainly from Paleogene to early Paleozoic deposits that were uplifted and eroded during Tertiary time. A simple model describing the maturation of reworked vitrinite gives results in good agreement with observations. This model explains how a discontinuity in vitrinite reflectance can occur across an erosional unconformity, and why this discontinuity may disappear with heating of the sediment pile over a sufficiently long time period. Vitrinite data are also sensitive to local heating caused by magmatic intrusions. This makes it possible to distinguish between intrusive and extrusive igneous rocks using vitrinite data, and to predict the existence and location of intrusive igneous rocks that have not been penetrated by drilling.
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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.