International Geologiical Congress - Oslo 2008

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EUR-04 Tectonic evolution of the lithosphere from European Precambrian Craton to Alpine system on the base of the deep geophysic

 

Structure of the crust in the area of Dinarides and Pannonian Basin based on gravity modelling

 

Franjo Šumanovac, University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering (Croatia)
 

 

The Dinarides and southwestern part of the Pannonian Basin are placed at the contact of the Adriatic microplate and the Eurasian plate. Although some authors emphasize the subduction of the Adriatic microplate under the Dinarides, the location of subduction is still subject of discussion.
Two-dimensional gravity modelling was carried out to highlight the contact of the Dinadires and Pannonian Basin and to define better structure of the crust. The area of exploration covers the areas of the Croatia and the Bosnia and Herzegovina. Four profiles were set up perpendicularly to the spread of the geological structures, i.e. the Dinarides and the contact zone. Among the profiles the ALP07 profile was also used, which was defined in framework of the seismic experiment ALP 2002. The profile stretches in Croatia in the WSW-NNE direction from Istra to the Drava river. On this profile the both modelling was performed, the seismic and the gravity modelling. Considering that seismic data have a much higher resolution, boundaries of individual layers and lateral boundaries on the profile ALP07 were taken from the seismic model to calibrate density distribution in the gravity model. On this way resolution of the gravity modelling at the other profiles is increased, which enabled more precise definition of crustal and upper mantle relationships in the investigated area.
According to the gravity models of the profiles three types of the crust can be considered: Dinaridic crust, Pannonian crust, and Transition zone. Dinaridic crust is two-layered with low densities in the upper crust and high densities in the lower crust. Pannonian crust can be thought as a unique layer, which is characterized by low densities. In the Transition zone lateral variation of the densities can be seen, caused by the wide ophiolites zones at the contact of the Dinarides and the Pannonian Basin. Anomalies of high densities that can be followed at all profiles are probably caused by the oceanic crust rocks. Crust of the Transition zone is more similar to the Dinaridic crust. Possible subduction of the Adriatic microplate could be placed at the edge parts of the Pannonian Basin. On the basis of all gravity models a general structural map of the area was established, which can be very helpful in planning of further seismic experiments in the area.

 

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