TY - JOUR A1 - Yuan, Xiaoping P. A1 - Braun, Jean A1 - Guerit, Laure A1 - Rouby, D. A1 - Cordonnier, G. T1 - A New Efficient Method to Solve the Stream Power Law Model Taking Into Account Sediment Deposition JF - Journal of geophysical research : Earth surface N2 - The stream power law model has been widely used to represent erosion by rivers but does not take into account the role played by sediment in modulating erosion and deposition rates. Davy and Lague (2009, ) provide an approach to address this issue, but it is computationally demanding because the local balance between erosion and deposition depends on sediment flux resulting from net upstream erosion. Here, we propose an efficient (i.e., O(N) and implicit) method to solve their equation. This means that, unlike other methods used to study the complete dynamics of fluvial systems (e.g., including the transition from detachment-limited to transport-limited behavior), our method is unconditionally stable even when large time steps are used. We demonstrate its applicability by performing a range of simulations based on a simple setup composed of an uplifting region adjacent to a stable foreland basin. As uplift and erosion progress, the mean elevations of the uplifting relief and the foreland increase, together with the average slope in the foreland. Sediments aggrade in the foreland and prograde to reach the base level where sediments are allowed to leave the system. We show how the topography of the uplifting relief and the stratigraphy of the foreland basin are controlled by the efficiency of river erosion and the efficiency of sediment transport by rivers. We observe the formation of a steady-state geometry in the uplifting region, and a dynamic steady state (i.e., autocyclic aggradation and incision) in the foreland, with aggradation and incision thicknesses up to tens of meters. KW - stream power law model KW - efficient method KW - sediment transport and deposition KW - river erosion KW - dynamic steady state KW - aggradation and incision cycles Y1 - 2019 U6 - https://doi.org/10.1029/2018JF004867 SN - 2169-9003 SN - 2169-9011 VL - 124 IS - 6 SP - 1346 EP - 1365 PB - American Geophysical Union CY - Washington 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 - 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 - Prasicek, Günther A1 - Herman, Frederic A1 - Robl, Jörg A1 - Braun, Jean T1 - Glacial steady state topography controlled by the coupled influence of tectonics and climate JF - Journal of geophysical research : Earth surface N2 - Glaciers and rivers are the main agents of mountain erosion. While in the fluvial realm empirical relationships and their mathematical description, such as the stream power law, improved the understanding of fundamental controls on landscape evolution, simple constraints on glacial topography and governing scaling relations are widely lacking. We present a steady state solution for longitudinal profiles along eroding glaciers in a coupled system that includes tectonics and climate. We combined the shallow ice approximation and a glacial erosion rule to calculate ice surface and bed topography from prescribed glacier mass balance gradient and rock uplift rate. Our approach is inspired by the classic application of the stream power law for describing a fluvial steady state but with the striking difference that, in the glacial realm, glacier mass balance is added as an altitude-dependent variable. From our analyses we find that ice surface slope and glacial relief scale with uplift rate with scaling exponents indicating that glacial relief is less sensitive to uplift rate than relief in most fluvial landscapes. Basic scaling relations controlled by either basal sliding or internal deformation follow a power law with the exponent depending on the exponents for the glacial erosion rule and Glen's flow law. In a mixed scenario of sliding and deformation, complicated scaling relations with variable exponents emerge. Furthermore, a cutoff in glacier mass balance or cold ice in high elevations can lead to substantially larger scaling exponents which may provide an explanation for high relief in high latitudes. KW - glacial equilibrium KW - steady state topography KW - glacial erosion KW - glacial buzzsaw KW - rock uplift-relief scaling KW - scaling relation Y1 - 2018 U6 - https://doi.org/10.1029/2017JF004559 SN - 2169-9003 SN - 2169-9011 VL - 123 IS - 6 SP - 1344 EP - 1362 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Pico, Tamara A1 - Mitrovica, Jerry X. A1 - Perron, J. Taylor A1 - Ferrier, Ken L. A1 - Braun, Jean T1 - Influence of glacial isostatic adjustment on river evolution along the US mid-Atlantic coast JF - Earth & planetary science letters N2 - Long-term river evolution depends partly on crustal deformation, which shapes the topography crossed by rivers. On glacial timescales, ice-sheet growth and decay can produce crustal vertical motion of ∼10 mm/yr resulting from the solid Earth's adjustment to variations in ice and water loads, comparable to tectonically-driven rates in the most rapidly uplifting mountains on Earth. This process of glacial isostatic adjustment (GIA) can influence river courses and drainage basins substantially, particularly near former ice margins. We explore the extent to which GIA influenced the evolution of rivers along the United States east coast during the last glacial cycle. We compute gravitationally self-consistent GIA responses that incorporate recent constraints on the Laurentide Ice Sheet history through the last glacial build-up phase, and we connect the predicted variations in topography to abrupt changes in river dynamics recorded in the Hudson, Delaware, Susquehanna, and Potomac Rivers from 40 ka to present. To the extent that increases in sediment transport capacity imply increases in river incision rate, the GIA-driven changes in slope and drainage area are consistent with episodes of erosion and sedimentation observed in the Hudson, Delaware, and Potomac Rivers, but inconsistent with the observed accelerated river incision in the Susquehanna River at 30-14 ka. These analyses add to a growing body of evidence showing that GIA strongly influences river evolution over millennial timescales. KW - glacial-isostatic adjustment KW - US east coast river geomorphology KW - river dynamics on glacial timescales Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2019.06.026 SN - 0012-821X SN - 1385-013X VL - 522 SP - 176 EP - 185 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pico, T. A1 - Mitrovica, J. X. A1 - Braun, Jean A1 - Ferrier, K. L. T1 - Glacial isostatic adjustment deflects the path of the ancestral Hudson River JF - Geology N2 - Quantifying the pace of ice-sheet growth is critical to understanding ice-age climate and dynamics. Here, we show that the diversion of the Hudson River (northeastern North America) late in the last glaciation phase (ca. 30 ka), which some previous studies have speculated was due to glacial isostatic adjustment (GIA), can be used to infer the timing of the Laurentide Ice Sheet’s growth to its maximum extent. Landscapes in the vicinity of glaciated regions have likely responded to crustal deformation produced by ice-sheet growth and decay through river drainage reorganization, given that rates of uplift and subsidence are on the order of tens of meters per thousand years. We perform global, gravitationally self-consistent simulations of GIA and input the predicted crustal deformation field into a landscape evolution model. Our calculations indicate that the eastward diversion of the Hudson River at 30 ka is consistent with exceptionally rapid growth of the Laurentide Ice Sheet late in the glaciation phase, beginning at 50–35 ka. Y1 - 2018 U6 - https://doi.org/10.1130/G40221.1 SN - 0091-7613 SN - 1943-2682 VL - 46 IS - 7 SP - 591 EP - 594 PB - American Institute of Physics CY - Boulder 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 - 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 - Murray, Kendra E. A1 - Braun, Jean A1 - Reiners, Peter W. T1 - Toward Robust Interpretation of Low-Temperature Thermochronometers in Magmatic Terranes JF - Geochemistry, geophysics, geosystems N2 - Many regions central to our understanding of tectonics and landscape evolution are active or ancient magmatic terranes, and robust interpretation of low-temperature thermochronologic ages in these settings requires careful attention to the drivers of rock heating and cooling, including magmatism. However, we currently lack a quantitative framework for evaluating the potential role of magmatic coolingthat is, post-magmatic thermal relaxationin shaping cooling age patterns in regions with a history of intrusive magmatism. Here we use analytical approximations and numerical models to characterize how low-temperature thermochronometers document cooling inside and around plutons in steadily exhuming environments. Our models predict that the thermal field a pluton intrudes into, specifically the ambient temperatures relative to the closure temperature of a given thermochronometer, is as important as the pluton size and temperature in controlling the pattern and extent of thermochronometer resetting in the country rocks around a pluton. We identify one advective and several conductive timescales that govern the relationship between the crystallization and cooling ages inside a pluton. In synthetic vertical age-elevation relationships (AERs), resetting next to plutons results in changes in AER slope that could be misinterpreted as past changes in exhumation rate if the history of magmatism is not accounted for. Finally, we find that large midcrustal plutons, such as those emplaced at similar to 10-15-km depth, can reset the low-temperature thermochronometers far above them in the upper crusta result with considerable consequences for thermochronology in arcs and regions with a history of magmatic activity that may not have a surface expression. KW - He thermochronology KW - Peclet number KW - age-elevation relationships Y1 - 2018 U6 - https://doi.org/10.1029/2018GC007595 SN - 1525-2027 VL - 19 IS - 10 SP - 3739 EP - 3763 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Margirier, Audrey A1 - Braun, Jean A1 - Gautheron, Cecile A1 - Carcaillet, Julien A1 - Schwartz, Stephane A1 - Jamme, Rosella Pinna A1 - Stanley, Jessica T1 - Climate control on Early Cenozoic denudation of the Namibian margin as deduced from new thermochronological constraints JF - Earth & planetary science letters N2 - The processes that control long term landscape evolution in continental interiors and, in particular, along passive margins such as in southern Africa, are still the subject of much debate (e.g. Braun, 2018). Although today the Namibian margin is characterized by an arid climate, it has experienced climatic fluctuations during the Cenozoic and, yet, to date no study has documented the potential role of climate on its erosion history. In western Namibia, the Brandberg Massif, an erosional remnant or inselberg, provides a good opportunity to document the Cenozoic denudation history of the margin using the relationship between rock cooling or exhumation ages and their elevation. Here we provide new apatite (UThSm)/He dates on the Brandberg Inselberg that range from 151 +/- 12 to 30 +/- 2 Ma. Combined with existing apatite fission track data, they yield new constraints on the denudation history of the margin. These data document two main cooling phases since continental break-up 130 Myr ago, a rapid one (similar to 10 degrees C/Myr) following break-up and a slower one (similar to 12 degrees C/Myr) between 65 and 35 Ma. We interpret them respectively to be related to escarpment erosion following rifting and continental break-up and as a phase of enhanced denudation during the Early Eocene Climatic Optimum. We propose that during the Early Eocene Climatic Optimum chemical weathering was important and contributed significantly to the denudation of the Namibian margin and the formation of a pediplain around the Brandberg and enhanced valley incision within the massif. Additionally, aridification of the region since 35 Ma has resulted in negligible denudation rates since that time. (C) 2019 Elsevier B.V. All rights reserved. KW - climate KW - Early Eocene Climatic Optimum KW - apatite (U-Th-Sm)/He thermochronology KW - denudation KW - weathering KW - Namibian passive margin Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2019.115779 SN - 0012-821X SN - 1385-013X VL - 527 PB - Elsevier CY - Amsterdam ER -