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Crustal structure and Mohorovicic discontinuity at the contact of the Adriatic microplate and Pannonian segment

Structure of the crust and surface of the Mohorovicic discontinuity at the contact of the Pannonian basin and Dinarides were determined on the basis of the data acquired in last decade in framework of new research projects (ALP2002, ALPASS-DIPS). Results based on three data sets were combined to solving structural and tectonic relations at this contact as a relation between the Adriatic microplate and the Pannonian segment. The basic exploration was carried out on the profile Alp07, which was a part of the active seismic experiment ALP2002. This profile stretched in Croatia from Istra to the Drava River in a WSW–ENE direction. Gravity modelling on the Alp07 profile enabled a definition of calibrated rock densities that were applied on other profiles set up in the study area, covering the area of Croatia and Bosnia-Herzegovina, for the purpose of determining the structural relations. This significantly improved the resolution of the gravity modelling. Passive seismic data, acquired in ALPASS-DIPS project using temporary seismic stations, provided for additional contribution in solving the crustal structure. The basic model was defined on the Alp07 profile by means of seismic and gravity modelling. The Moho is the deepest in the area of the Dinarides (40 km), and is shallowest in the Pannonian basin area (20 km). The structural units determined on the Alp07 profile (Dinaridic and Pannonian crusts and Transition zone) can be easily followed on all other gravity profiles in the survey area. Wide transition zone 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 units of the Dinarides. The obtained results enabled the development of a 3-D structural map of the Mohorovicic discontinuity. Types of the receiver functions of the passive seismic data approved that different types of crust exist. Modelling of characteristic Pannonian receiver functions affirmed the thesis of the seismic and gravity modelling that the Pannonian crust can be considered as one-layered. On the basis of all data sets a geological model was constructed, which contributes in solving the most interesting tasks in the area. The subduction area, namely the contact of the microplates at the level of the upper mantle, is located on the NE flank of the Dinarides. The NE boundary of the Transition zone is located much further north than the boundary of the Tisia block in published tectonic maps.

Adriatic microplate; gravity modelling; passive seismic data

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