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High-elevation plateaus that are positioned in between topographic barriers are common orogenic features in the South American continent, formed under a range of evolving environmental conditions. For example, in the central Andes (Bolivia-Argentina), the Puna-Altiplano is arid and endorheic with a poorly developed fluvial system, while in the northern Andes (Colombia) the Chiquinquira and Tunja highlands are characterized by a humid equatorial exorheic fluvial system. In addition to a plateau-like low-relief surface at 2500 m, the landscape of the northern Eastern Cordillera and Santander Massif (northern Colombia) displays a lower elevation (~1500 m) low-relief landscape (Mesas) comprising river captures, windgaps, and a disconnected alluvial fan that collectively record a transient state. This configuration has been achieved through a combination of compressive deformation and sub-crustal processes. The compressive shortening started to occur in the Paleogene and is still active, whereas regional surface uplift related to slab flattening and mantle wedge hydration started in the Late Miocene/Pliocene. To disentangle the crustal vs sub-crustal forcing and to investigate the relative timing of drainage network evolution we combine the analysis of topography, hydrography (river longitudinal profiles, morphometric parameters, drainage divide stability), knickpoint migration (celerity model), paleo-longitudinal profile modeling, satellite images, and field observations. In particular, we show that during the development of the low-relief Mesas landscape the older Chiquinquira highland was a closed drainage and that the lower portion of the Suarez River flowed northward into the Bucaramanga depression forced by the Los Cobardes Anticline topographic barrier. The Suarez River collected waters from the southern Santander Massif and the upper reach of the Chicamocha River, which was draining the Tunja highland. An abandoned windgap deposit on the eastern edge of the Mesa de Barichara suggests that the lower portion of the Chicamocha River was not yet formed. Subsequent to the Chiquinquira highland drainage opening, two main tributaries of the Magdalena River, the Lebrija and Sogamoso, captured the Suarez River in a short temporal sequence. A knickpoint celerity model allows us to date the Lebrija capture of the Bucaramanga depression at ~260–270 ka and the subsequent Sogamoso capture at 190–220 ka. Only during this final stage, the lowermost Chicamocha River section formed and the drainage network developed to its present configuration. Finally, we suggest that the early Cenozoic rift inversion has controlled the drainage network pattern and the late Miocene sub-crustal-induced surface uplift has driven the main fluvial network reorganization.

Continental areas affected by mantle plume dynamics are characterised by extensive high-elevated regions drained by large radial river networks. Despite successive isostatic adjustments and rifting events, several studies demonstrated that the persistence of these drainage systems for tens of millions of years is possible. In these geodynamic contexts rivers are precious sources of knowledge because, propagating the signals of tectonic and climatic changes across landscape, they shape the topography and allow to recognise the first-order imprint imposed by mantle plume. The Horn of Africa, characterised by the coexistence of a continental rift system, a large igneous province (continental flood basalts), and a wide uplifted plateau, is an ideal test site to investigate the interrelations between surface and deep processes. Studies demonstrated the long-term persistence of some river networks draining the region and the strong influence of dome-like uplift on their evolution. However a regional-scale quantitative river network analysis is missing, as well as, a complete evolutionary scenario of the Horn of Africa drainage system. In this study we quantitatively investigated the topographic configuration of the Horn of Africa and analysed the four principal drainage systems (Blue Nile, Tekeze, Omo, Wabe Shebele basins), extracting the river longitudinal profiles and the main topographic and hydrologic parameters. In order to reconstruct the evolution of the region, we elaborated the pre−/syn- and post-flood basalts topographies and calculated the elevation gain and loss with respect to the present configuration. Finally, we delineated a possible future drainage system evolution by analysing the present drainage divides stability. The results allowed to reconstruct the evolutionary scenario of the Horn of Africa river network since Oligocene and to investigate the mutual influence between surface and deep processes in shaping the landscape, providing new constraints to understand the formation and evolution of a drainage system in a context of a topography supported by a mantle plume.

We present a geologic map of the Tekeze River basin that covers an area of ∼69,000 km2 of northern Ethiopia. The map synthesizes new data collected in two campaigns between March, 2012 and January, 2013 and compiled at a scale of 1:500,000 with published geologic surveys. The map focuses on the main geologic and tectonic features relevant to a modern interpretation of the geologic evolution of northern Ethiopia and as such, it represents an important synthesis for environmental and natural resource management.

The Apennines chain is an active Neogene fold-and-thrust belt resulting from the westward subduction of the Adriatic microplate. Starting from the end of the Early Pleistocene, the chain was affected by an increase in regional uplift. Recent GPS data resolved uplift rates of 1–2 mm/yr for the whole Apennines, whereas, in the Adriatic flank, several studies estimated rates between 0.3 and 0.5 mm/yr over the last 1 Myr. A number of works investigated the evolution of the drainage systems along the Periadriatic margin of the Apennines providing long-term incision rates. Studies from the northern part of this sector reported uplift rates varying from 0.2 to 1.1 mm/yr, whereas only few studies concentrated on the central sector of the Adriatic flank of the Apennines, focusing mainly on the evolution of the lower reach of major rivers. This work aims to quantify the long-term rock uplift and incision rates of the eastern portion of the central Apennines through the analysis of the Tronto River basin. Because of its geologic and geomorphological configurations, this basin is an ideal test site to investigate the influence of tectonics and climate on the recent topographic evolution of the central Apennines. The basin extends, with a roughly WSW-ENE direction, from the inner sector of the chain to the Adriatic coast, crossing several tectonic structures such as the Amatrice extensional basin and the Acquasanta and Montagna dei Fiori anticlines. In particular, in the Acquasanta Terme area, the right flank of the Tronto River valley is characterized by fluvial and travertine deposits organized and exposed in several levels. In this work, we investigated the hydrography (river longitudinal profiles) and topography (swath profile, slope, and local relief) of the Tronto River basin coupling these data with field observations and geochronological analysis on the continental sediments (fluvial deposits and travertines) outcropping in the Acquasanta Terme area. To better characterize the nature of travertines, we performed geochemical characterization of three travertine-forming thermal springs obtaining their physico-chemical parameters, the percentage of dissolved gases, and the isotopes content. Finally, we applied a knickpoint celerity model to chronologically constrain the geomorphological evolution of the whole drainage system. The results show the occurrence of a continuous tectonic uplift (~0.5 mm/yr) across the study area since Middle Pleistocene. The uplift, together with climate fluctuations, drove the incision (~0.6 mm/yr) of the landscape and the delineation of the present drainage network. These data are consistent with previous estimates of uplift and incision rates in adjacent areas and provide new constraints on the Quaternary evolution of the central Apennines. This study highlights how the coupling of field surveys with morphometric and topographic analyses of a drainage system is crucial to understand and quantify the influence of tectonic and climate changes in shaping the landscape.

We investigate the along‐axis variations in architecture, segmentation, and evolution of the Main Ethiopian Rift (MER), East Africa, and relate these characteristics to the regional geology, lithospheric structure, and surface processes. We first illustrate significant along‐axis variations in basin architecture through analysis of simplified geological cross sections in different rift sectors. We then integrate this information with a new analysis of Ethiopian topography and hydrography to illustrate how rift architecture (basin symmetry/asymmetry) is reflected in the margin topography and has been likely amplified by a positive feedback between tectonics (flexural uplift) and surface processes (fluvial erosion and unloading). This analysis shows that ~70% of the 500 km long MER is asymmetric, with most of the asymmetric rift sectors being characterized by a master fault system on the eastern margin. We finally relate rift architecture and segmentation to the regional geology and geophysical constraints on the lithosphere. We provide strong evidence that rift architecture is controlled by the contrasting nature of the lithosphere beneath the homogeneous, strong Somalian Plateau and the weaker, more heterogeneous Ethiopian Plateau, differences originating from the presence of pre‐rift zones of weakness on the Ethiopian Plateau and likely amplified by surface processes. The data provided by this integrated analysis suggest that asymmetric rifts may directly progress to focused axial tectonic‐magmatic activity, without transitioning into a symmetric rifting stage. These observations have important implications for the asymmetry of continental rifts and conjugate passive margins worldwide.

Density anomalies beneath the lithosphere are expected to generate dynamic topography at the Earth's surface due to the induced mantle flow stresses which scale linearly with density anomalies, while the viscosity of the upper mantle is expected to control uplift rates. However, limited attention has been given to the role of the lithosphere. Here we present results from analogue modeling of the interactions between a density anomaly rising in the mantle and the lithosphere in a Newtonian system. We find that, for instabilities with wavelengths of the same order of magnitude as lithosphere thickness, the uplift rate and the geometry of the surface bulge are inversely correlated to the lithosphere thickness. We also show that a layered lithosphere may modulate the topographic signal. With respect to previous approaches our models represent a novel attempt to unravel the way normal stresses generated by mantle flow are transmitted through a rheologically stratified lithosphere and the resulting topographic signal. © 2017. American Geophysical Union. All Rights Reserved., T.W.B. was partially supported through NASA OSP 201601412-001.

Ethiopia offers an excellent opportunity to study the effects and linkage between mantle dynamics and surface processes on landscape evolution. The Ethiopian Highlands (NW Ethiopia), characterized by a huge basaltic plateau, is part of the African Superswell, a wide region of dynamically-supported anomalously high topography related to the rising of the Afar plume. The initiation and steadiness of dynamic support beneath Ethiopia has been explored in several studies. However the presence, role, and timing of dynamic support beneath Ethiopia and its relationship with continental flood basalts volcanism and surface processes are poorly defined. Here, we present a geomorphological analysis of the Ethiopian Highlands supplying new constraints on the evolution of river network. We investigated the general topographic features (filtered topography, swath profiles, local relief) and the river network (river longitudinal profiles) of the study area. We also apply a knickpoint celerity model in order to provide a chronological framework to the evolution of the river network. The results trace the long-term progressive capture of the Ethiopian Highlands drainage system and confirm the long-term dynamic support of the area, documenting its impact on the contrasting development of the Blue Nile and Tekeze basins.

Ethiopia is a key site to investigate the interactions between mantle dynamics and surface processes because of the presence of the Main Ethiopian Rift (MER), Cenozoic continental flood basalt volcanism, and plateau uplift. The role of mantle plumes in causing Ethiopia's flood basalts and tectonics has been commonly accepted. However, the location and number of plumes and their impact on surface uplift are still uncertain. Here we present new constraints on the geological and topographic evolution of the Ethiopian Plateau (NW Ethiopia) prior to and after the emplacement of the large flood basalts (40–20 Ma). Using geological information and topographic reconstructions, we show that the large topographic dome that we see today is a long-term feature, already present prior to the emplacement of the flood basalts. We also infer that large-scale doming operated even after the emplacement of the flood basalts. Using a comparison with the present-day topographic setting, we show that an important component of the topography has been and is presently represented by a residual, nonisostatic, dynamic contribution. We conclude that the growth of the Ethiopian Plateau is a long-term, probably still active, dynamically supported process. Our arguments provide constraints on the processes leading to the formation of one of the largest igneous plateaus on Earth.

Recent modeling shows that surface processes, such as erosion and deposition, may drive the deformation of the Earth's surface, interfering with deeper crustal and mantle signals. To investigate the coupling between the surface and deep process, we designed a three-dimensional laboratory apparatus, to analyze the role of erosion and sedimentation, triggered by deep mantle instability. The setup is constituted and scaled down to natural gravity field using a thin viscous sheet model, with mantle and lithosphere simulated by Newtonian viscous glucose syrup and silicon putty, respectively. The surface process is simulated assuming a simple erosion law producing the downhill flow of a thin viscous material away from high topography. The deep mantle upwelling is triggered by the rise of a buoyant sphere. The results of these models along with the parametric analysis show how surface processes influence uplift velocity and topography signals.