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Lithosphere structure at the contact of the Adriatic microplate and the Pannonian segment based on the gravity modelling

Two-dimensional gravity modelling is applied to the contact of the Dinarides and the Pannonian basin as a contribution to solving structural and tectonic relations in the area characterized by very complex relations. An interpretation procedure, which improves the resolution of gravity modelling by the use of seismic refraction data, has been developed. On the Alp07 profile, which is set up in the framework of the ALP 2002 seismic experiment and stretches in Croatia from Istra over the Dinarides to the Drava River, seismic modelling was performed in order to determine the structure of the lithosphere. A 2-D gravity modelling was also carried out on the profile to obtain calibrated rock densities using interfaces from the seismic model. Calibrated densities were applied to other profiles set up in the study area for the purpose of determining the structural relations. The structural units determined on the Alp07 profile (Pannonian crust, Transition zone and Dinaridic crust) can be easily followed on all other profiles. The Transition zone, which separates the Pannonian and the Dinaridic crusts, is very wide and characterized by lateral and vertical changes in velocities and densities. It corresponds with the ophiolite zones in more recent tectonic maps. The Tisia block can be compared with the Pannonian crust, whereas the Dinaridic crust would relate to the structural unites of the Adriatic. However, the NE boundary of the Transition zone is located much further north than the boundary of the Tisia block in published tectonic maps. Due to a marked 2-D structure, the obtained results enabled the development of a 3-D structural map of the Mohorovičić discontinuity. The main fault in the upper mantle, which was defined on the basis of geometrical relations, indicates a subduction of the Adriatic microplate beneath the Pannonian segment in the NE wing of the Dinarides.

Adriatic microplate; Dinarides; Pannonian basin; subduction; gravity modelling

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