Search

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. • The coastal mountain system forms a climatic boundary in southeastern China. • Thermochronological data collected along two horizontal transects. • Transect thermochronology results used for topography modeling. • Rapid exhumation from 70-60 Ma along the south 2-D transect linked to rifting. • Rapid exhumation from 60–40 Ma along the north 2-D transect linked to climate change. [ABSTRACT FROM AUTHOR]

This paper presents an approach to improve the previously proposed 2-D topography modeling (Ding et al., 2019) that is primarily based on inversion of low-temperature thermochronological data. The new approach requires thermochronological data from both horizontal transect and vertical profiles to yield a more comprehensive modeling of topographic evolution. This modeling allows for (1) reconstruction of paleotopography evolution and (2) calculation of spatial distribution of paleo-geothermal gradients over time; therefore, it is possible to deduce more reliable exhumation histories even for non-steady state topographic evolution. The deduced exhumation histories are used to re-evaluate the topography modeling results. This approach when applied to the Dabie orogen in Eastern China suggests an uneven topographic evolution along the Xishui-Lu'an section and comparable exhumation histories for the Meichuan, the Tianzhushan, the Mingtangshan and the Tiantangzhai vertical profiles since the Late Cretaceous. The modeling results suggest that the location of the highest elevation in the NE-SW transect has been almost identical for the last 80 Ma although the elevation of the peak has reduced by ~3.3 km over the same period. The elevation reduction in the NE segment during 70–40 Ma is caused by extensional activity of the Xiaotian-Mozitan fault. The elevation reduction in the SW segment during 50–30 Ma is probably related to climate change, where the Paleogene topography change in the Dabie orogen played an important role introducing humid and warm air from the Pacific Ocean. • The Dabie orogen forms a tectonic and climatic boundary in Eastern China. • Thermochronological data collected along horizontal transects and vertical profiles • Transect/profile thermochronology results used for topography modeling • Rapid exhumation from 70 to 40 Ma along NE 2-D transect segment linked to faulting • Rapid exhumation from 50 to 30 Ma along SE 2-D transect segment linked to climate change [ABSTRACT FROM AUTHOR]