Differential Erosion and Sedimentation Process at the Longmenshan Foreland Basin, Eastern Margin of the Tibetan Plateau: Evidence From Analog Experiments

Abstract

We use analog experiments to investigate the influence of rapid filling of a foreland basin system during the development of a fold-and-thrust belt, in particular, the change of erosion–sedimentation along the strike in the Longmenshan foreland basin. A negative relationship between wedge geometries and the magnitude of erosion can be found; increased erosion results in out-of-sequence thrusting and fault reactivation in the wedge hinterland, to limit the forelandward propagation of the wedge. In contrast, increased sedimentation facilitates the forelandward propagation of the wedge. We focus on a natural example of the Longmenshan foreland basin, where a change in erosion–sedimentation along the strike during the Late Cretaceous to Cenozoic is well documented. The comparison between our model and seismic sections indicates that such along-strike variation results in a rejuvenated foreland basin restricted to the southwestern part of the western Sichuan Basin in the Cenozoic.

Influence of Regional Erosion and Sedimentary Loading on Fault Activities in Active Fold-Thrust Belts: Insights From Discrete Element Simulation and the Southern and Central Longmen Shan Fold-Thrust Belt

“…In recent years, many important achievements have also been published in this study of erosion rates along-strike or cross-strike in major faults (Xu and Kamp, 2000;Tan et al, 2015;Gao et al, 2016;Tan et al, 2017;Tan et al, 2019;Luo et al, 2021;Wang et al, 2021), as well as the syntectonic sedimentation deposited in the LMS active fold-thrust belt (Yan et al, 2013;Li et al, 2014;Li et al, 2016;Li C. et al, 2018;Luo et al, 2021). According to previous research on the regional erosion system, at least 4-5 km of strata have been eroded in the southern and central LMS at an erosion rate of 0 mm/yr to 1.0 mm/yr from the range front to the hinterland of the LMS foldthrust belt since the late Miocene (Tan et al, 2017;Shen et al, 2019;Ye, 2021;Wang et al, 2021).…”

“…During the Late Triassic to Early Jurassic, the Songpan Ganzi fold belt was thrust upon the western margin of the Yangtze Plate (Yan et al, 2011). The LMS fold-thrust belt uplifted rapidly and was accompanied by approximately 1-2 km of wedge-shaped molasse deposited in the Chengdu plain, an alluvial plain in the western Sichuan basin (Figure 1B) (Luo et al, 2021). Moreover, the Cenozoic sedimentary strata, including the Eocene-Oligocene Minshan and Lushan formations, the upper Pliocene Dayi Formation, the middle Pleistocene Ya'an Formation, the upper Pleistocene Chengdu Clay Formation, and uppermost Holocene deposits, crop out mainly on the Chengdu plain and can also be found locally in the foothills of the LMS (Li et al, 2016).…”

“…In active fold-thrust belts around the world, such as the Aconcagua fold-thrust belt in Argentina (Hilley et al, 2004), the central Andes fold-thrust belt in Bolivia (Horton, 1999;McQuarrie et al, 2008), the central Apennines fold-thrust belt in Italy (Scisciani and Montefalcone, 2006;Wu and McClay, 2011), and the Taiwan fold-thrust belt in China (Dahlen and Suppe 1988;Dadson et al, 2003;Wu and McClay, 2011), the roles of different synkinematic erosion and/or sedimentary loading, probably caused by long-term along-strike climatic variations (McQuarrie et al, 2008), on the generation and evolution of thrust faults in these fold-thrust belts (thrust wedges) have been interpreted and discussed by the Coulomb wedge model theory (e.g., Davis et al, 1983;Dahlen et al, 1984;Dahlen and Suppe 1988) and experimental simulations (e.g., Storti and Mcclay, 1995;Persson and Sokoutis, 2002;Simpson, 2006;Graveleau and Dominguez, 2008;Cruz et al, 2010;Cruz et al, 2011;Wu and McClay, 2011;Malavieille, 2011;Steer et al, 2014;Sun et al, 2016;Sun et al, 2021;Luo et al, 2021;Mao et al, 2021). Theoretical analysis and modeling results have all shown that syntectonic erosion reduced the number of major forwardvergent thrusts, and increased exhumation and thrust activities at the rear of the thrust wedge, resulted in out-of-sequence thrusting and fault reactivation in the wedge hinterland, and inhibited the forward propagation of the deformation front into the foreland.…”

“…The Longmen Shan (LMS) Mountains, located in the eastern margin of the Qinghai-Tibetan Plateau with an NE trend, was a suture zone between the Yangtze block and the Songpan-Ganzi block and was reactivated due to the far-field compression of the India-Asia collision (Burchfiel et al, 1995;Roger et al, 2003, ;Zhou et al, 2006;Roger et., 2010;Yan et al, 2011) (Figure 1A). It has experienced a long history of deformation since the Mesozoic, which resulted in the development of a series of fold-thrust belts along the western boundary of the Sichuan Basin (Burchfiel et al, 1995;Yan et al, 2008), and the deposition of a suite of late Triassic to Cretaceous-Quaternary sediments in the Sichuan Basin (Chen et al, 1994;Li Z. et al, 2018;Luo et al, 2021) (Figures 1B,C). The 2008 M W 7.9 Wenchuan earthquake occurred deep in the interior of the LMS fold-thrust belt, 200 km northwest of the toe of the fold-thrust belt in the Sichuan basin (Hubbard et al, 2010), accompanied by the formation of coseismic reverse-and oblique-slip surface faulting by two large thrust faults (Lin et al, 2009;Liu-Zeng et al, 2009;Xu et al, 2009;Li et al, 2010).…”

“…Moreover, in the LMS foldthrust belt, Li et al (2016), Li C. et al (2018) identified growth strata and revealed early to late Pleistocene activity on the Range Front blind thrust. Recently, by using sandbox analog experiments, Luo et al (2021) investigated the influences of differential rates of synkinematic erosion and sedimentation on wedge geometries and fault activities during the development of thrust wedges, and further discussed the influences from the change of erosion-sedimentation along the strike on the structural evolution of the LMS fold-thrust belt; Mao et al (2021) have shown that surface erosion and sedimentation affected the position, morphology, lateral propagation, and connection of new structures in fold-thrust belts. Overall, sufficient studies have shown the important relationship between surface processes (denudation and/or deposition) and tectonic processes (fault activity) in fold-thrust belts, although there are still some different viewpoints on the main controlling factors.…”