TY - JOUR A1 - Zhang, Di A1 - Cao, Kai A1 - Yuan, Xiaoping A1 - Wang, Guocan A1 - van der Beek, Peter T1 - Late Oligocene-early Miocene origin of the First Bend of the Yangtze River explained by thrusting-induced river reorganization JF - Geomorphology N2 - The origin of the First Bend of the Yangtze River is key to understanding the birth of the modern Yangtze River. Despite considerable efforts, the timing and mechanism of formation of the First Bend remain highly debated. Inverse river-profile modeling of three tributaries (Chongjiang, Lima, and Gudu) of the Jinsha River, integrated with regional tectonic and geomorphic interpretations, allows the onset of incision at the First Bend to be constrained to 28-20 Ma. The spatio-temporal coincidence of initial river incision and activity of Yulong Thrust Belt in southeastern Tibet highlights thrusting to be fundamental in reshaping the pre-existing stream network at the First Bend. These results enable us to reinterpret a change in sedimentary environment from a braided river to a swamp-like lake in the Jianchuan Basin south of the First Bend, recording the destruction of the hypothesized southwards-flowing paleo-Jinsha and Shuiluo Rivers at ~36-35 Ma by magmatism. During the late Oligoceneearly Miocene, the paleo-Shuiluo River was diverted to the north by focused rock uplift due to thrusting along the Yulong Thrust Belt, which also led to exhumation of the Jianchuan Basin. Diversion of the paleo-Shuiluo River can be explained by capture from a downstream river in the footwall of the Yulong Thrust Belt. Subsequent rapid headward erosion, that was caused by thrusting-induced drop of local base level, is recorded by upstream younging ages for the onset of incision and led to the formation of the First Bend. The combination of new ages for the onset of incision at 28-20 Ma at the First Bend and younger ages upstream indicates northwards expansion of the Jinsha River at a rate of 62 +/- 18 mm/yr. Our results suggest that the origin of the First Bend was likely triggered by thrusting at 28-20 Ma, after which the Yangtze River formed. KW - Tibetan Plateau KW - Yangtze River KW - river incision KW - inverse modeling Y1 - 2022 U6 - https://doi.org/10.1016/j.geomorph.2022.108303 SN - 0169-555X SN - 1872-695X VL - 411 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Neuharth, Derek A1 - Brune, Sascha A1 - Wrona, Thilo A1 - Glerum, Anne A1 - Braun, Jean A1 - Yuan, Xiaoping T1 - Evolution of rift systems and their fault networks in response to surface processes JF - Tectonics N2 - Continental rifting is responsible for the generation of major sedimentary basins, both during rift inception and during the formation of rifted continental margins. Geophysical and field studies revealed that rifts feature complex networks of normal faults but the factors controlling fault network properties and their evolution are still matter of debate. Here, we employ high-resolution 2D geodynamic models (ASPECT) including two-way coupling to a surface processes (SP) code (FastScape) to conduct 12 models of major rift types that are exposed to various degrees of erosion and sedimentation. We further present a novel quantitative fault analysis toolbox (Fatbox), which allows us to isolate fault growth patterns, the number of faults, and their length and displacement throughout rift history. Our analysis reveals that rift fault networks may evolve through five major phases: (a) distributed deformation and coalescence, (b) fault system growth, (c) fault system decline and basinward localization, (d) rift migration, and (e) breakup. These phases can be correlated to distinct rifted margin domains. Models of asymmetric rifting suggest rift migration is facilitated through both ductile and brittle deformation within a weak exhumation channel that rotates subhorizontally and remains active at low angles. In sedimentation-starved settings, this channel satisfies the conditions for serpentinization. We find that SP are not only able to enhance strain localization and to increase fault longevity but that they also reduce the total length of the fault system, prolong rift phases and delay continental breakup. KW - rifts KW - fault network KW - surface processes KW - geodynamics Y1 - 2022 U6 - https://doi.org/10.1029/2021TC007166 SN - 0278-7407 SN - 1944-9194 VL - 41 IS - 3 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Wolf, Sebastian G. A1 - Huismans, Ritske S. A1 - Braun, Jean A1 - Yuan, Xiaoping T1 - Topography of mountain belts controlled by rheology and surface processes JF - Nature : the international weekly journal of science N2 - It is widely recognized that collisional mountain belt topography is generated by crustal thickening and lowered by river bedrock erosion, linking climate and tectonics(1-4). However, whether surface processes or lithospheric strength control mountain belt height, shape and longevity remains uncertain. Additionally, how to reconcile high erosion rates in some active orogens with long-term survival of mountain belts for hundreds of millions of years remains enigmatic. Here we investigate mountain belt growth and decay using a new coupled surface process(5,6) and mantle-scale tectonic model(7). End-member models and the new non-dimensional Beaumont number, Bm, quantify how surface processes and tectonics control the topographic evolution of mountain belts, and enable the definition of three end-member types of growing orogens: type 1, non-steady state, strength controlled (Bm > 0.5); type 2, flux steady state(8), strength controlled (Bm approximate to 0.4-0.5); and type 3, flux steady state, erosion controlled (Bm < 0.4). Our results indicate that tectonics dominate in Himalaya-Tibet and the Central Andes (both type 1), efficient surface processes balance high convergence rates in Taiwan (probably type 2) and surface processes dominate in the Southern Alps of New Zealand (type 3). Orogenic decay is determined by erosional efficiency and can be subdivided into two phases with variable isostatic rebound characteristics and associated timescales. The results presented here provide a unified framework explaining how surface processes and lithospheric strength control the height, shape, and longevity of mountain belts. Y1 - 2022 U6 - https://doi.org/10.1038/s41586-022-04700-6 SN - 0028-0836 SN - 1476-4687 VL - 606 IS - 7914 SP - 516 EP - 521 PB - Nature portfolio CY - Berlin ER - TY - JOUR A1 - Neuharth, Derek A1 - Brune, Sascha A1 - Glerum, Anne A1 - Morley, Chris K. A1 - Yuan, Xiaoping A1 - Braun, Jean T1 - Flexural strike-slip basins JF - Geology : a venture in earth science reporting / the Geological Society of America N2 - Strike-slip faults are classically associated with pull-apart basins where continental crust is thinned between two laterally offset fault segments. We propose a subsidence mechanism to explain the formation of a new type of basin where no substantial segment offset or synstrike-slip thinning is observed. Such "flexural strike-slip basins" form due to a sediment load creating accommodation space by bending the lithosphere. We use a two-way coupling between the geodynamic code ASPECT and surface-processes code FastScape to show that flexural strike-slip basins emerge if sediment is deposited on thin lithosphere close to a strike slip fault. These conditions were met at the Andaman Basin Central fault (Andaman Sea, Indian Ocean), where seismic reflection data provide evidence of a laterally extensive flexural basin with a depocenter located parallel to the strike-slip fault trace. Y1 - 2021 U6 - https://doi.org/10.1130/G49351.1 SN - 0091-7613 SN - 1943-2682 VL - 50 IS - 3 SP - 361 EP - 365 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Yuan, Xiaoping A1 - Braun, Jean A1 - Guerit, Laure A1 - Simon, Brendan A1 - Bovy, Benoît A1 - Rouby, Delphine A1 - Robin, Cécile A1 - Jiao, R. T1 - Linking continental erosion to marine sediment transport and deposition: A new implicit and O(N) method for inverse analysis JF - Earth & planetary science letters N2 - The marine sedimentary record contains unique information about the history of erosion, uplift and climate of the adjacent continent. Inverting this record has been the purpose of many numerical studies. However, limited attention has been given to linking continental erosion to marine sediment transport and deposition in large-scale surface process evolution models. Here we present a new numerical method for marine sediment transport and deposition that is directly coupled to a landscape evolution algorithm solving for the continental fluvial and hillslope erosion equations using implicit and O(N) algorithms. The new method takes into account the sorting of grain sizes (e.g., silt and sand) in the marine domain using a non-linear multiple grain-size diffusion equation and assumes that the sediment flux exported from the continental domain is proportional to the bathymetric slope. Specific transport coefficients and compaction factors are assumed for the two different grain sizes to simulate the stratigraphic architecture. The resulting set of equations is solved using an efficient (O(N) and implicit) algorithm. It can thus be used to invert stratigraphic geometries using a Bayesian approach that requires a large number of simulations. This new method is used to invert the sedimentary geometry of a natural example, the Ogooue Delta (Gabon), over the last similar to 5 Myr. The objective is to unravel the set of erosional histories of the adjacent continental domain compatible with the observed geometry of the offshore delta. For this, we use a Bayesian inversion scheme in which the misfit function is constructed by comparing four geometrical parameters between the natural and the simulated delta: the volume of sediments stored in the delta, the surface slope, the initial and the final shelf lengths. We find that the best-fit values of the transport coefficients for silt in the marine domain are in the range of 300 - 500 m(2)/yr, in agreement with previous studies on offshore diffusion. We also show that, in order to fit the sedimentary geometry, erosion rate on the continental domain must have increased by a factor of 6 to 8 since 5.3 Ma. (C) 2019 Elsevier B.V. All rights reserved. KW - river erosion KW - sediment-transport model KW - efficient method KW - inverse analysis KW - the Ogooue Delta Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2019.115728 SN - 0012-821X SN - 1385-013X VL - 524 PB - Elsevier CY - Amsterdam ER -