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Paleogene Basins in Croatia as a Connection between Tisza and Dinarides – A Missing Link.

There are many scientific and technical papers describing relationship between Tysia and Dinarides that are based on possible interpretations of the subsurface geology since the contact between them is not visible at the surface (LUŽAR et al, 2012, PAMIĆ, 2002, and other..). ˝Sava suture zone˝ passes through the Sava basin and it is considered to be a border between Tysia and Dinarides unit. The only key to understanding the subsurface is deep exploration drilling. INA has been exploring the Sava basin for the past 50 years. Therefore, there is a vast archive of various analytics performed on cores and drilling cuttings and biostratigraphic, petrographic, geochemical and fluid analyses that need to be viewed in the light of recent regional geological findings. Dinarides structural unit is clearly visible in the outcrops from Karlovac in the west, Banja Luka in the central part, all through Tuzla and furthermore to the east. Paleogene- Neogene sediments lie due north regarding the ˝Sava suture zone˝ and extend all the way to Sava river. Northern of Sava river there are only Quarternary sediments lying over Neogene sediments that are positioned on the older formations of Tysia. Direct contact of Dinarides unit with Tysia remains unknown. Although Paleogene basins were well developed in the area of northern Bosnia, their development and extent in the Croatian part of Pannonian basin remains a mystery. Certain wells in the southernmost part of the Pannonian basin, in the area of Karlovac sub-basin, encountered Paleogene sediments. The official lithostratigraphic nomenclature of INA never included Paleogene lithostratigraphic unit as it was considered to be a part of Prečec formation that has remained undivided for decades and as such received a status of a complex. As a result of such division, geological events that took place between 65 and 20 Ma years ago were insufficiently explored and never fully understood. Furthermore, the majority of metasediments, potentially of Paleogene age, were marked with EL marker Tg (Basement) which places them in older geological formations. The latest researches and analyses completed in the past 5 years resulted in undeniable proof of existence of Paleogene sediments in the southern parts of the Pannonian basin, in the northern Posavina zone. 2D and 3D seismic show geological units that can be correlated and calibrated with Paleogene sediments. 2D and 3D seismic, as well as many other analytical methods, have their limitations and interpretation of such methods can be different from author to author resulting in different theses. 3D seismic in the western part of Sava basin, along with laboratory analyses, can shed light upon the distribution, extent and development of Paleogene sediments in the northern Posavina area. Paleogene basins represent a missing link between Dinarides and Tysia units but they are also an element that is necessary in interpretation of geological events that took place between 65 and 20 Ma years ago.

Paleogene basins, Tysia, Dinarides, Sava suture zone, Pannonian basin

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