From nappe stacking to exhumation: Cretaceous tectonics in the Apuseni Mountains (Romania)

Abstract

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.

Magmatic and tectonic history of Jurassic ophiolites and associated granitoids from the South Apuseni Mountains (Romania)

“…Others (e.g. Csontos and Vörös 2004;Reiser et al 2016) regard the Tisza and Dacia Mega-Units as a single continental entity at the time of obduction. In a later, "intra-Turonian" phase (Săndulescu 1984(Săndulescu , 1994 that formed the present-day nappe stack in the Apuseni Mountains, the Dacia Mega-Unit and overlying ophiolitic unit were thrust over the Tisza MegaUnit.…”

The Late Cretaceous Klepa basalts in Macedonia (FYROM)—Constraints on the final stage of Tethys closure in the Balkans

“…Regional subsidence resulted in peneplanisation during the late Jurassic and formation of lateritic crust and bauxites, suggesting that the whole region was potentially a continental environment at that time. Both sides of the Sava Zone, that is, the Lower Pelagonian unit (Kilias et al., ) and the Dacia unit (Reiser, Schuster, Spikings, Tropper, & Fügenschuh, ), have been overprinted by Early Cretaceous regional metamorphism, which is not easy to understand if the two areas were separated by an open ocean at that time. Furthermore, the absence of Early/Late Cretaceous ophiolites in the Balkans together with Late Jurassic ages of metamorphic soles all over the Balkan Peninsula (Borojević Šoštarić et al., and references therein) seem to indicate that convergence and ocean closure took place during the Late Jurassic.…”

Pervasive early diagenetic dolomitization, subsequent hydrothermal alteration, and late stage hydrocarbon accumulation in a Middle Triassic carbonate sequence (Szeged Basin, SE Hungary)

“…3a). These processes resulted in widespread presence of subhorizontal, north-northwest-directed thrusts throughout the basement of the Pannonian Basin (e.g., Tari et al, 1999;Csontos and Vörös, 2004;Matenco and Radivojević, 2012;Molnár et al, 2015;Reiser et al, 2016). The locally occurring Late Cretaceous (95-82 Ma) tectonometamorphism was presumably related to these overthrust zones where the Lower to Middle Triassic sediments could be affected by low-grade metamorphism (Árkai et al, 2000; Árkai, 2001).…”