New Ar–Ar muscovite and Rb–Sr biotite age data in combination with structural analyses from the Apuseni Mountains provide new constraints on the timing and kinematics of deformation during the Cretaceous. Time–temperature paths from the structurally highest basement nappe of the Apuseni Mountains in combination with sedimentary data indicate exhumation and a position close to the surface after the Late Jurassic emplacement of the South Apuseni Ophiolites. Early Cretaceous Ar–Ar muscovite ages from structurally lower parts in the Biharia Nappe System (Dacia Mega-Unit) show cooling from medium-grade conditions. NE–SW-trending stretching lineation and associated kinematic indicators of this deformation phase (D1) are overprinted by top-NW-directed thrusting during D2. An Albian to Turonian age (110–90 Ma) is proposed for the main deformation (D2) that formed the present-day geometry of the nappe stack and led to a pervasive retrograde greenschist-facies overprint. Thermochronological and structural data from the Bihor Unit (Tisza Mega-Unit) allowed to establish E-directed differential exhumation during Early–Late Cretaceous times (D3.1). Brittle detachment faulting (D3.2) and the deposition of syn-extensional sediments indicate general uplift and partial surface exposure during the Late Cretaceous. Brittle conditions persist during the latest Cretaceous compressional overprint (D4).Electronic supplementary materialThe online version of this article (doi:10.1007/s00531-016-1335-y) contains supplementary material, which is available to authorized users.
The Kuchyňa tuff is found on the Eastern margin of the Vienna Basin and was formed by felsic volcanism. The Ar/Ar single grain sanidine method was applied and resulted in an age of 15.23±0.04 Ma, which can be interpreted as the age of the eruption. The obtained numerical age is in accordance with the subtropical climate inferred by the presence of fossil leaves that originated in an evergreen broadleaved forest. Furthermore, the described volcanism was connected with the syn-rift stage of the back-arc Pannonian Basin system. The sedimentological data from the underlying sandy mudstones indicate alluvial environment what confirms terrestrial conditions during deposition. Moreover, the tuff deposition probably occurred shortly before the Badenian transgression of the Central Paratethys Sea.
The Brenner Base Tunnel will connect Innsbruck (Austria) and Franzensfeste (Italy) by piercing two of the most important fault structures of the Alps: the Periadriatic fault system (PFS) and the Southern limit of Alpine metamorphism (SAM). (U‐Th)/He dating (apatite) and fission‐track analysis (apatite and zircon) on samples taken during excavation reveal a complex pattern of exhumation through time. The results yield temporal constraints for relative vertical block movement and fault activity. Furthermore, they indicate differential uplift of the northern block along the ~E–W striking PFS and allow locating the position of the SAM in the overtilted nappe stack south of the Tauern Window. Our data strongly support, for the first time, an ongoing north‐side‐up movement along this section of the PFS until at least the end of Miocene.
Basement rocks from the Biharia Nappe System in the Apuseni Mountains comprise several dolomite and calcite marble sequences or lenses which experienced deformation and metamorphic overprint during the Alpine orogeny. New Sr, O and C-isotope data in combination with considerations from the lithological sequences indicate Middle to Late Triassic deposition of calcite marbles from the Vulturese-Belioara Series (Biharia Nappe s.str.). Ductile deformation and large-scale folding of the siliciclastic and carbonatic lithologies is attributed to NW-directed nappe stacking during late Early Cretaceous times (D2). The studied marble sequences experienced a metamorphic overprint under lower greenschist-facies conditions (316 -370°C based on calcite -dolomite geothermometry) during this tectonic event.Other marblesequencesfromtheBihariaNappe System(i.e.VidolmandBaiadeArieșnappes) showsimilaritiesin the stratigraphic sequence and their isotope signature, together with a comparable structural position close to nappe contact. However, the dataset is not concise enough to allow for a definitive attribution of a Mesozoic origin to other marble sequences than the Vulturese-Belioara Series.
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