Late Cretaceous-Cenozoic exhumation of the southeastern margin of Coastal Mountains, SE China, revealed by fission-track thermochronology: Implications for the topographic evolution

Abstract

Apatite and zircon fission-track (FT) analyses were used to reveal the Late Cretaceous-Cenozoic exhumation of the Southeastern margin of Coastal Mountains (SCM), Southeast (SE) China. Zircon FT ages ranging from 92 ± 5 to 98 ± 6 Ma, and apatite from 54 ± 4 to 68 ± 6 Ma with mean measured track lengths between 12.2 ± 1.6 and 12.9 ± 2.0 μm, were obtained for the granitoids sampled along an east to west transect across the SCM. The three-stage, involving the first rapid stage, following by slow stage, and finally accelerated cooling stage, and inferred exhumation since the Late Cretaceous have been identified in the study region based on the FT data and modeling results. Assuming a steady-state paleogeothermal gradient of 25 °C/km founded on geological setting, the exhumations of 4000 m, 2000 m and 1600 m, and the paleoelevation decreases of 727 m, 364 m and 291 m, were achieved in the SCM, during 94–60 Ma, 60–25 Ma and 25–0 Ma, respectively. This hence reveals that the paleoelevation in the SCM was decreased rapidly from ∼1400 m a.s.l. in the early Late Cretaceous to ∼650 m a.s.l. in the early Paleogene, subsequently slowly to ∼300 m a.s.l. in the Late Oligocene, and finally to ∼0 m a.s.l. in the present at an accelerated rate. Our results indicate that the SCM experienced an episodic exhumation, and successive decreases in paleoelevation, predominantly induced by complex geodynamic processes.