EUROCORES_TopoEurope_1.Call_Inherited structures: the Apuseni Mountains (SourceSink)

"The role of the memory inherited by the system from the Cretaceous-Tertiary evolution of convergent margins into the build-up of the Source area" represents an individual project (IP) submitted in the framework of the Source-Sink CRP (EUROCORES project 2199). It addresses the circular shaped Apuseni Mountains (Romania) which are bordered by two basins of rather distinct character and evolution: the Miocene Pannonian basin in the west and north with a rather flat topography and the hilly Transsylvanian basin with its two-stage evolution. The northern part of the Apuseni Mountains belongs to the Tisza-unit, a microplate with mixed European and Adriatic affinity, which extends from NE Croatia into Romania and is mostly covered by the Neogene infill of the Pannonian basin. The Tisza unit presently forms a top to the NW-directed Turonian-age nappe stack which comprises from bottom to top the Mescek (only outcropping in southern Hungary), the Bihor (northern Croatia and Apuseni mountains) and the Codru (Apuseni Mountains) nappe systems. Most authors also attribute the tectonically highest Biharia nappe system to the Tisza microplate. The Biharia nappe system itself is tectonically overlain by the South Apuseni ophiolites defining the "Main Tethyan suture" between Tisza and Dacia which formed during mid-Cretaceous orogeny. However, when combining surface information in the Apuseni Mountains with subsurface information from the eastward located Transylvanian basin it becomes evident that the Biharia nappe is without interruption connected with the easterly located Bucovinian (or Getic/Supragetic) nappes of the Dacia unit. They form one and the same tectonic unit with takes the structurally highest position in the East Carpathian nappe stack. Although already partly formed during the late Jurassic, final east-directed emplacement of the Transylvanides occurred during the mid-Cretaceous. According to this correlation Turonian NW-directed thrusting led to a substantial offset of the former suture and thrusted Dacia-derived units (Biharia) against the Codru nappe system of Tisza with the western prolongation of the former suture buried underneath the Apuseni mountains. While the southern continuation of the south Apuseni Mountains into the Eastern Vardar ophiolites is well accepted there is no clear answer in the north. Either the Eastern Vardar-South Apuseni ophiolites represent the remnants of a northerly ending branch of Neotethys (failed arm) or it has to be sutured between the continuously documented Biharia-Bucovinian nappes and the underlying Codru nappe system. We expect to answer the following questions and contribute to the Source-Sink (CRP of EUROCORES project 2199) topic: Characterization of kinematics and activity of main tectonic contacts should allow for correlation with tectonic contacts in the wider Alpine Carpathian Dinarides context Characterization of the cooling and exhumation history of the Apuseni mountains, from when on did the area serve as a source region Was the exhumation of the Apuseni Mountains continuous or discontinuous both in space and in time? Were any pre-existing faults reactivated to allow for its exhumation? Is the exhumation of the Apuseni Mountains linked to the shortening in the Transylvanian basin? Are the Apuseni Mountains at least partly responsible for the distinct Tertiary tectonic evolution of the Pannonian and Transylvanian basin respectively? In order to address the posed questions we intend to apply: Field-based structural geology from ductile to brittle features Microstructural and textural analysis High to low-temperature thermochronology Petrology

Although the Apuseni Mountains are a rather small mountain range, they are of great importance for the general understanding of the Alpine-Carpathian-Dinaridic region. Situated between the Pannonian and Transylvanian basins, the Apuseni Mountains provide a window through Neogene sediments into the basement. New results on the structural and temporal evolution of this mountain range during the Cretaceous allow for a better understanding of the interaction between the Tisza and Dacia Mega-Units, which build up this mountain range.In detail, this study provides new data on the tectonic evolution of the Tisza and Dacia Mega-Units during the Cretaceous. New structural data allow deriving the directions and intensity of tectonic phases which overprinted the Apuseni Mountains. In combination with age data, it was possible to develop a new model for the evolution of the Apuseni Mountains during the Cretaceous. Furthermore, the combination of the new datasets provided new constraints for the evolution of the Alps, Carpathians and Dinarides. The Apuseni Mountains were both source and sink of eroded material throughout the Cretaceous. The tectonic model allows identifying phases of tectonic activity and increased sediment supply. A close spatial and temporal relationship of the source and sink indicate a direct link and interaction between them. The tectonometamorphic evolution of the Apuseni Mountains indicates a strong tectonic influence on the supply of erosional material from the source area. Although the climatic influence on the Apuseni Mountains during the Cretaceous is difficult to constrain, it is apparent from this study that the sedimentary supply from the source is governed by tectonic processes, at least during Cretaceous times.