Late Cenozoic exhumation history of the Luoji Shan in the southeastern Tibetan Plateau: insights from apatite fission-track thermochronology

Abstract

Denudational history inferred from bedrock low-temperature thermochronological data provides significant constraint to tectonic models for explaining the growth of the Tibetan Plateau. Here, we present new apatite fission-track ages from the Luoji Shan, bounded by the Anninghe and Zemuhe faults in the southeastern Tibetan Plateau. Cooling ages vary from c. 5 to c. 13 Ma from the bottom to the top of a vertical profile. The age–elevation relationship can be interpreted as either (1) a phase of river incision at a rate of c. 0.16 km Ma −1 from c. 13 to c. 5 Ma or (2) a phase of denudation of c. 0.40 km Ma −1 between c. 13 and c. 10 Ma, followed by a phase of extremely slow denudation ( c. 0.03 km Ma −1 ). The results suggest that initiation of river incision started before c. 13 Ma in the study area. Combined with previously published data from adjacent sites, our results indicate that denudation in this region displayed substantial spatial variation. This finding does not support the existing lower crustal flow model for Tibetan Plateau growth, which predicts uniform denudation. We further speculate that the vertical component of slip along the southern extension of the Anninghe fault might have significantly declined since late Miocene time, explaining the decreased rate of erosion c. 10 Ma.

Multistage Exhumation in the Catchment of the Anninghe River in the SE Tibetan Plateau: Insights From Both Detrital Thermochronology and Topographic Analysis

“…Here, we target the catchment of the Anninghe River, a tributary of the Yalong River, which was considered to be captured by the Dadu River in the early Pleistocene (Yang et al, 2019). Since both the Oligocene and late-Miocene exhumation were reported in the area (H. Wang et al, 2017Wang et al, , 2020, we analyzed the grain-age distribution of modern sediments from the Anninghe River, with the aim to test if the age peaks can record the onset timing for rapid erosion. Together with topographic analysis, we try to discuss the regional exhumation pattern and a Cenozoic erosion history in the SE TP.…”

Thermochronological Constraints on the Late Cenozoic Morphotectonic Evolution of the Min Shan, the Eastern Margin of the Tibetan Plateau

“…Different initiation times of the high‐elevation and high‐relief landscape in the southeastern and eastern Tibetan Plateau have been determined using paleoaltimetry, thermochronology, and cosmogenic approaches. First, many studies used exhumation history determined from thermochronology data as an index for surface uplift and suggested that growth of the high‐relief topography initiated at the late Miocene (5–12 Ma) in the eastern Tibetan Plateau (Clark, Bush, et al, ; Jolivet et al, ; Kirby et al, ; Ouimet et al, ; Tan et al, ), mid‐Miocene (15–22 Ma) in southeastern Tibetan Plateau (Tian, Kohn, Hu, et al, ), or at variable times in different sectors (Shen et al, ; Tian, Kohn, Hu, et al, ; Yang et al, ; Wang et al, ). It is worth noting that the multimethod thermochronology data from vertical profiles in the central Longen Shan (Wang et al, ), Jiulong Shan (Zhang et al, ), the First Bend of the Yangtze River (Shen et al, ), and Three River region (Liu‐Zeng et al, ) suggested an Oligocene‐early Miocene (~35–15 Ma) phase of exhumation, prior to the late Miocene phase.…”

“…In this second model, upper crustal shortening occurs above a gently dipping middle crustal detachment that links with steep reverse faults at plateau margins, forming a large‐scale listric fault extending from plateau margin to plateau interior (Tian et al, , ). However, another group of studies highlighted that the exhumation in the southeastern Tibetan Plateau is strongly nonuniform in both time and space, indicating differential rock uplift and faulting among crustal blocks (e.g., Shen et al, ; Tian, Kohn, Hu, et al, ; Wang et al, ; Yang et al, ).…”

Role of the Early Miocene Jinhe-Qinghe Thrust Belt in the building of the Southeastern Tibetan Plateau topography

“…The recent GPS velocity field (Zhang et al, 2004) confirmed that the plateau material migrates from the interior of Tibetan Plateau to the eastern and southeastern margin. Several studies targeted at the boundary strike-slip faults between different blocks (e.g., Leloup et al, 1995Leloup et al, , 2001Replumaz et al, 2001;Xu and Kamp, 2000;Zhang et al, 2017;Wang et al, 2017). Many other studies have been published on the Longmenshan (LMS) thrust belt.…”