Burial Ages Imply Miocene Uplift of Lu Mountain in East China due to Crustal Shortening

Zhiyong Han,Xusheng Li,Rouxian Pan,Yujia Liu,Xianyan Wang,Yufang Li

doi:10.3389/feart.2021.634105

Abstract

Confined by the eastern and western boundary faults, Lu Mountain has long been considered a block mountain uplifted due to Mesozoic and Cenozoic crustal deformation in East China. However, the formation and evolution of this block mountain are still debated. In this study, the eastern boundary fault is investigated to confirm the tectonic style of the block mountain. In addition, the burial ages of sediments on the fans of the eastern piedmont are measured by 26Al/10Be dating to evaluate the denudation rate. Field evidence indicates the presence of a reverse fault (Xingzi reverse fault) acting as the eastern boundary fault, which demonstrates that the block mountain is not a horst as once thought but an extrusion structure. Corrected 26Al/10Be burial ages show that the sediments on the high-level fans were deposited at approximately 1.1–1.2 Ma, which indicates denudation rates ranging from 0.033 to 0.082 m/kyr. The vertical displacement along the Xingzi reverse fault is estimated to be at least 1,100 m. The hanging wall could have been eroded to its present position within 13–33 Myr at the above denudation rates. Combining our results with regional geological and geomorphological evidence, we suggest that Lu Mountain was mainly uplifted in the Miocene due to crustal compression deformation, which may have been a response to the movement of the Pacific plate.

Highlights

Determining the time and amplitude of the tectonic uplift of mountains is an important research topic in tectonics and geomorphology (e.g., Tapponnier et al, 2001; Wang et al, 2008; Fang et al, 2020)
The field investigation confirms that the eastern boundary fault does exist, but it is a reverse fault characterized by sinistral motion rather than a normal fault
The corrected burial ages from 26Al/10Be dating indicate that the sediments on the high-level fans on the eastern piedmont of Lu Mountain were deposited at 1.1–1.2 Minimum burial age (Ma), implying that the denudation rate of the piedmont is between 0.033 and 0.082 m/ kyr

Summary

Introduction

Determining the time and amplitude of the tectonic uplift of mountains is an important research topic in tectonics and geomorphology (e.g., Tapponnier et al, 2001; Wang et al, 2008; Fang et al, 2020). Tectonic uplift has been explored through low-temperature thermochronology (Clark et al, 2010), cosmogenic nuclide-derived ages and erosion rates (Palumbo et al, 2011) and fault scarp heights (Zheng et al, 2013) Among these approaches, denudation rates are receiving increasing attention since they can imply tectonic movement and climate change (Reiners and Brandon, 2006) and can be used to determine the time of tectonic uplift together with independent geomorphic markers (Palumbo et al, 2009; Yuan et al, 2011). In the early Yanshanian orogeny, the westward subduction of the Pacific plate led to a great transition of tectonic orientations in East China, resulting in the development of NE-SWtrending structures (Li et al, 2011). The NE-SW-trending Lu anticline might have formed against this background

Results

Discussion

Conclusion