Life cycle of the East Carpathian orogen: Erosion history of a doubly vergent critical wedge assessed by fission track thermochronology

Apatite fission track (FT) thermochronology applied to the East Carpathian fold-and-thrust belt in Romania constrains the interaction between the eros ion history and the tectonic evolution of the orogen. The long-lived consta nt asymmetric topography of the orogen and the erosion pattern as inferred from apatite FT data are in agreement with the style of evolution predicted by doubly vergent critical Coulomb wedge models. During the Miocene, up to 4 km of erosion took place over the actively deforming orogen, and the ero sion patterns forms a mirrored image of the subsurface deforming wedge. The erosion products are deposited in flanking molasse basins which subsided c ontemporaneously due to the growing topographic weight of the wedge. Deform ation of the wedge was presumably active from the early to late Miocene, bu t apatite FT ages between 14 and 9 Ma and track length modeling predict an acceleration of erosion rates (0.5-0.3 mm/yr) initially in the middle to la te Miocene (approximate to 13+/-2 Ma). The onset of erosion coincides with the last phase of convergence and a climax in the deformation history. Thes e features are interpreted to have been caused by underplating of the Europ ean continental margin. Convergence ceased before the Pliocene according to the activity of thrust faults. During the Pliocene and Quaternary, up to 2 km of overburden was removed by erosion, leading to isostatic rock:uplift of the entire region. The use of apatite fission track "minimum ages" suppo rts the general idea that the orogen has a diachronous evolution from north to south. The orogen in the southern Bend Zone has a more juvenile tectoni c character, and the main erosion phase took place during the Pliocene and Quaternary (approximate to 5-0 Ma). The integrated approach of large scale morphology and fission track analysis confirms the applicability of the the oretical Coulomb wedge mechanics to a natural compressive fold-and-thrust b elt. The study complements the geometric features of the orogenic wedge wit h quantified erosion histories and illustrates the effects of orogen evolut ion on vertical movements in the entire convergent setting.