Extraordinary denudation in the Sichuan Basin: Insights from low‐temperature thermochronology adjacent to the eastern margin of the Tibetan Plateau

Abstract

[1] The eastern margin of the Tibetan Plateau combines very high relief with almost no Tertiary foreland sedimentation and little evidence of Cenozoic tectonic shortening. While river incision and landscape development at the plateau margin have received significant attention over the last decade, little is known about the Cenozoic development of the adjacent Sichuan Basin. Here we assess the Cenozoic thermal history of this basin using detrital apatite fission track (AFT) and (U-Th)/He techniques and establish the presence of an exhumed AFT paleopartial annealing zone across much of the basin. This observation, combined with stratigraphic and borehole sections and inverse modeling of confined apatite fission tracks, indicates that the strata within the basin have undergone accelerated cooling after $40 Ma, consistent with the widespread erosion of $1 to 4 km of overlying sedimentary material. This regional-scale erosion is most likely a response to changes in the Yangtze River system draining and removing sediment from the basin. The base-level fall associated with this erosion contributed to a relative increase in relief across the Longmen Shan and may have helped drive Miocene-Recent incision and unloading of the plateau margin.

Diverse exhumation of the Mesozoic tectonic belt within the Yangtze Plate, China, determined by apatite fission-track thermochronology

“…Moreover, Table 1 manifests the weak relationship between the AFT ages and the sample elevations, not as would be expected from a region experiencing simple exhumation. Figure 3 exhibits the histograms of the apatite fission track age distribution in the northwestern MTB, in the southeastern MTB and in the Huangling Dome, in comparison with the AFT ages of surface rocks in the study region by Hu et al (2006), Richardson et al (2008), Shen et al (2009), Mei et al (2010, and this study. Evidently, the AFT ages are divisible into three clusters of ~65 Ma in the northwestern MTB, ~75 Ma in the southeastern MTB and ~95 Ma in the Huangling Dome (Fig.…”

“…1. Sketch of the MTB, China (Modified after Ma et al, 2002), and a compilation of AFT ages from Hu et al (2006), Richardson et al (2008), Shen et al (2009, Mei et al (2010, and this study (the unspecified provenance). ment fault by thick-skinned deformation characterized by the Xuefeng and Wuling nappes and numerous klippen.…”

“…It has been successfully applied to study the spatial and temporal pattern of the exhumation since the Mesozoic in Alps, Appalachia, Andes, Qinghai-Tibetan Plateau, Qingling-Dabie-Sulu etc. (e.g., Gleadow and Fitzgerald, 1987;Johnson, 1997;Gallagher et al, 1998;Willet et al, 2003;Hu et al, 2006;Richardson et al, 2008Richardson et al, , 2010Wang et al, 2009). Thus, in this study, we compile new and mostly published AFT data to better constrain the age and rate of the cooling of the Mesozoic tectonic belt (MTB) within the Yangtze Plate, provide firmer constraints on the exhumation history.…”

“…The uplift and denudation of the MTB since the Late Mesozoic (at least the Late Cretaceous) have been generally recognized (Hu et al, 2006;Richardson et al, 2008Richardson et al, , 2010Shen et al, 2009;Mei, 2010;Tian et al, 2011). However, the age and rate of the exhumation, especially the variation in the different sections of the MTB are still poorly constrained.…”

Uprising period and elevation of the Wenyu granitic pluton in the Xiaoqinling District, Central China

“…Given that the distribution of counts were inconsistent with purely Poissonian variation [55,56], the pooled age was adopted, which was simply the sum of the spontaneous counts divided by the sum of the induced counts [57]. ZFT ages are all younger than the formation age of the plutons from which the samples were collected, thus indicating that the samples experienced post-thermal events [58] within the zircon PAZ. The point of inflexion on the zircon age-absolute elevation curve at ~1250 m (Figure 2) marks the base of an exhumed PAZ (Figure 3).…”