Doktorska disertacija Paleomagnetic and geochronologic constraints on the Miocene evolution of semi-isolated basins in southeastern Europe
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Utrecht University, Netherlands
This thesis addresses the Miocene evolution of the Central Paratethys and neighboring Dinaride Mountains. The Central Paratethys was a vast epicontinental sea covering most of central and southeastern Europe during the Oligo-Miocene. The Dinarides were situated along the southwestern border of the former Central Paratethys, separating it from the Mediterranean. An extensive long-lived lake system thrived in the orogen’s intra-montane basins during the Late Oligocene and Miocene. The intrinsic isolation of the Dinaride Lakes and the progressive isolation of the Paratethys led to severe faunal endemism, which hampers straightforward biostratigraphic correlation of their deposits to radio-isotopically or cyclostratigraphically dated sedimentary records elsewhere. High resolution age constraints are thus generally lacking, which obstructs global or even regional correlation of events apparent in the geological record and thus limits our insight in the geodynamic and paleogeographic history of southeastern Europe. This is, in our opinion, one of the most fundamental geological problems to be solved in this area. The main objective of this thesis is therefore to provide new age constraints for the Dinaride Lake System and Central Paratethys applying radio-isotopic, cyclostratigraphic and magnetostratigraphic dating methods. We first turn to the Dinaride Lake System and construct chronologies for lacustrine deposition in the Sinj, Livno Tomislavgrad, Gacko, Banovići, and South Pannonian Basins. We synthesize the acquired results and supplement these with tectonic rotations of the area, using new paleomagnetic data and a compilation of existing data for the Dinarides and Adria. A first phase of intra-montane basin formation occurred in the late Oligocene when strike-slip faulting penetrated into the orogen. A second phase of basin formation took place between 18 and 13 Ma, concurrent with profound extension in the neighbouring Pannonian Basin. The Dinarides did not experience any significant tectonic rotation since the late Oligocene. These results significantly improve our insight in the post-orogenic evolution of the Dinarides and resolve the apparent controversy between structural geological and paleomagnetic rotation estimates for the Dinarides as well as Adria. The Middle Miocene evolution of the Central Paratethys is characterized by multiple isolation events. We present a new chronology for the catastrophic Badenian Salinity Crisis which triggered evaporite deposition in large parts of the sea and exterminated a great number of its species. Evaporite deposition began at 13.81±0.08 Ma, shortly after glacial event Mi-3b. The global sea level fall that occurred in conjunction with the Mi-3b event most likely restricted the open marine connection with the Mediterranean trapping salt in the deep Paratethys basins. The entire event is estimated to have lasted 200 to 600 kyr. Normal marine conditions were restored in the Central Paratethys after the salinity crisis. A new chronostratigraphy for the Middle Miocene infill of the Transylvanian Basin indicates that renewed isolation at the transition from the Badenian to the Sarmatian stage, reflected again in a distinctive faunal turnover, occurred at 12.80±0.05 Ma. The final isolation and transition from marine to fresh water occurred at 11.3 Ma concurrent with enhanced uplift in the Carpathians and a 20° clockwise rotation of the Transylvanian Basin. Chronostratigraphy, Paratethys, Dinaride Lake System, Transylvanian Basin, Badenian Salinity Crisis Increased insight in the timing of formation and disappearance of marine and lacustrine basins in southeastern Europe during the Miocene, and improved constraints on the incipience of major environmental changes in these basins, leads to a better understanding of the geodynamic and climatic forcing factors at play in the hodgepodge of the Africa-Europe collision zone. The timing of the origin, evolution and disappearance of semi-isolated marine and lacustrine basins in southeastern Europe during the Miocene, and the paleo-environmental changes affecting their evolution.
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