Records of latest Triassic, mid-Cretaceous and Cenozoic uplift/exhumation phases in the Istanbul zone revealed by apatite fission-track and (U-Th)/He thermochronology

Abstract

ABSTRACT Apatite fission-track and (U-Th)/He ages from Carboniferous to Eocene siliciclastic rocks of the Istanbul Zone (NW Turkey) range from 220 to 46 Ma, and from 46 to 18 Ma, respectively. Apatite grains from the upper Cretaceous and Eocene volcaniclastic and siliciclastic formations yielded unreset fission-track ages (85 to 65 Ma), whereas the Lower Cretaceous siliciclastic rocks yielded both reset and unreset apatite fission-track ages. This suggests the absence of substantial burial after the Early Cretaceous. The thermochronological dataset presented here in conjunction with published data defines three major deformation and uplift/exhumation phases: (i) 220–179 Ma (Late Triassic-Early Jurassic), (ii) 101–107 Ma (mid-Cretaceous), and (iii) 66–16 Ma (Palaeocene-early Miocene). The Late Triassic-Early Jurassic uplift/exhumation phase can be attributed to the Cimmeride orogeny and the uplift of the Pontides. The mid-Cretaceous uplift/deformation is also reflected in the stratigraphic record as a major unconformity, which was probably caused by the accretion of an oceanic plateau or a seamount. The Palaeocene-early Eocene uplift/deformations resulted from the closure of the Izmir-Ankara-Erzincan oceanic domain. The late Oligocene-early Miocene uplift/deformation is probably caused by extension in the Aegean region due to the suction along the Hellenic trench.