Reconstruction of the topographic evolution of the coastal mountain system in southeastern China

Abstract

The coastal mountain system (CMS) of southeastern China has been a natural place to study paleotopographic changes primarily due to its marked topographical contrast since the Late Cretaceous. For a quantitative reconstruction of the paleotopographic evolution of the CMS, this paper provides key information from along the Ningde–Jianyang and Huilai–Longchuan cross-sections using apatite (U-Th)/He (AHe) and zircon (U-Th)/He (ZHe) data combined with thermal history and paleotopographic modeling. For the Ningde–Jianyang section, the AHe dates are in the range of 44.3–70.8 Ma, and the ZHe dates are between 58.5 and 102.9 Ma. For the Huilai–Longchuan section, the resulting AHe dates are in the range of 37.9–73.8 Ma, and ZHe dates are between 65.5 and 119.7 Ma. The modeling results suggest that: 1) the CMS had an asymmetric topography during the Late Cretaceous with the SE segment being significantly higher (peak elevation = 3.8 km) than the NW segment (peak elevation = ~2 km). The marked decreases in elevation and relief of the CMS occurred during 80–40 Ma, followed by relatively minor topographic changes since ~40–30 Ma; 2) The SE segment of the southern CMS experienced significantly faster exhumation (~0.44 km/Myr) than northern CMS (0.16 km/Myr) during 70–60 Ma, which was probably related to thinning of the crust and orogenic collapse linked to the initial-rifting of the South China Sea; 3) The SE segment of southern CMS experienced slower exhumation than northern CMS during 60–40 Ma, likely resulting from the lower elevations in the southern CMS than in the northern CMS during 60–40 Ma.