Detrital fission track thermochronology of Upper Cretaceous syn-orogenic sediments in the South Carpathians (Romania): inferences on the tectonic evolution of a collisional hinterland
E. Willingshofer, P. Andriessen, S. Cloetingh and F. Neubauer
Journal name: Basin Research
Issue: Vol 13, No 4, December 2001 pp. 379 - 395
Info: Article, PDF ( 1.41Mb )
The tectonic evolution of a collisional hinterland sourcing the Hateg Basin, a Late Cretaceous syn-orogenic sedimentary basin in the South Carpathians (Romania), is revealed through fission track thermochronology of detrital apatite and zircon grains. This basin formed on the upper plate (Getic unit) in response to I,ate Cretaceous collision with the lower plate (Danubian unit), an allochtonous continental block of the Moesian Platform, upon closure of a narrow oceanic basin (Severin Basin). The fission track results suggest that Turonian to lower Maastrichtian sediments of the Hateg Basin have been dominantly derived from pre-Late Cretaceous sources. The age components they contain relate to pre-Cretaceous tectonothermal events such as theVariscan orogenic cycle, Jurassic rifting and Severin Basin formation, and to Early Cretaceous cornpressional tectonics. These results are compatible with the tectonic evolution of the upper plate that is identified as the primary source. From the onset of sedimentation (late Albian) until the early Carnpanian the Hateg Basin resembles a piggy-back basin formed on the upper plate concomitant with underthrusting and internal stackin of the lower plate. In contrast, important tectonic subsidence during the late Campanian and early Maastrichtian reflects a shift to extensional tectonics causing the unroofing of the collision zone and the exhumation of lower plate rocks back to the surface. Our fission track data place important constraints on the timing of lmver plate erosion that must have commenced during the late Maastrichtian, as documented by the completely reset Late Cretaceous age component within upper Maastrichtian sediments (Sinpetru Formation), Late Maastrichtian uplift of the basin and the formation of positive relief at the site of the collision zone is an expression of continuous convergence. The mismatch between the amount of denudation and the amount of sediments trapped in the Haleg Basin underlines the importance of concomitant extensional unroofing.