Papers by Sebastien Castelltort
River drainage patterns sculpt terrestrial landscapes. Whether these patterns contain fingerprint... more River drainage patterns sculpt terrestrial landscapes. Whether these patterns contain fingerprints of past tectonic events is debated. On the one hand, elaborate dendritic river networks always retain an invariant structure, implying that rivers will simply reorganize in response to tectonic perturbations, without long-term trace of the tectonic event. On the other hand, many rivers in active mountain belts seem to be passive features and may record long-term crustal deformation. Here we use numerical simulations, constrained by drainage patterns observed in the Southern Alps of New Zealand, to analyse the response of river basins to distributed plate tectonic strain. We find that both dynamically reorganized and passively deformed rivers coexist in the Southern Alps. Rivers on the western side of the mountain range reorganize and rapidly evolve in response to tectonic deformation. In contrast, rivers on the eastern side resist reorganization and record large-scale plate tectonic influence over timescales of tens of millions of years. We conclude that both types of river drainage pattern in the Southern Alps are primarily controlled by plate tectonic strain, implying that landscape topography can be used to reconstruct the distribution of tectonic strain within zones of continental deformation around the world.
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This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright a b s t r a c t The Western foreland basin in Taiwan originated through the oblique collision between the Luzon volcanic arc and the Asian passive margin. Crustal flexure adjacent to the growing orogenic load created a subsiding foreland basin. The sedimentary record reveals progressively changing sedimentary environments influenced by the orogen approaching from the East. Based on sedimentary facies distribution at five key stratigraphic horizons, paleogeographic maps were constructed. The maps highlight the complicated basin-wide dynamics of sediment dispersal within an evolving foreland basin. The basin physiography changed very little from the middle Miocene ($12.5 Ma) to the late Pliocene ($3 Ma). The transition from a passive margin to foreland basin setting in the late Pliocene ($3 Ma), during deposition of the mud-dominated Chinshui Shale, is dominantly marked by a deepening and widening of the main depositional basin. These finer grained Taiwan derived sediments clearly indicate increased subsidence, though water depths remain relatively shallow, and sedimentation associated with the approach of the growing orogen to the East. In the late Pleistocene as the shallow marine wedge ahead of the growing orogen propagated southward , the proximal parts of the basin evolved into a wedge-top setting introducing deformation and sed-imentation in the distal basin. Despite high Pleistocene to modern erosion/sedimentation rates, shallow marine facies persist, as the basin remains open to the South and longitudinal transport is sufficient to prevent it from becoming overfilled or even fully terrestrial. Our paleoenvironmental and paleogeographical reconstructions constrain southward propagation rates in the range of 5–20 km/Myr from 2 Ma to 0.5 Ma, and 106–120 km/Myr between late Pleistocene and present (0.5–0 Ma). The initial rates are not synchronous with the migration of the sediment depocenters highlighting the complexity of sediment distribution and accumulation in evolving foreland basins.
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Rivers are a major component of sediment routing systems that control the transfer of terrig-
eno... more Rivers are a major component of sediment routing systems that control the transfer of terrig-
enous sediments from source to sink. Although it is widely accepted that rivers are perturbed by millennial-scale climatic variability, the extent to which these signals are buffered or trans- ferred down river systems to be recorded in sediments at or beyond the river mouth remains debated. Here, we employ a physically based numerical model to address this outstanding issue. Our model shows that river transport strongly amplifies high-frequency sediment flux variations arising from changing water discharge, due to positive feedback between discharge and the channel gradient. This behavior is distinctly different from short-period sediment flux signals (with constant water discharge) where the output sediment flux is strongly dampened within the river, due to negative feedback between the channel gradient and sediment concen- tration. We conclude that marine sedimentary basins may record sediment flux cycles result- ing from discharge (and ultimately climate) variability, whereas they may be relatively insen- sitive to pure sediment flux perturbations (such as for example those induced by tectonics).
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We investigate the influence of initial conditions of slope and surface roughness on the shape (l... more We investigate the influence of initial conditions of slope and surface roughness on the shape (length to width aspect ratio) of incipient drainage basins in numerical experiments of simple tilted surfaces using the CASCADE code of landscape evolution. Comparison with data on the shape of river basins in nature shows that simple rules of the steepest-descent routing of water are sufficient to account for a natural range of incipient drainage basin shape, independently of the erosion processes at work. To produce numerical basins that respect the main aspect ratio of natural drainage basins, one must use very low initial regional surface slopes of less than 1° at the scale of the entire drainage basins, and a local roughness slope of less than 3° at the scale of local surface irregularities. Numerical studies addressing real study cases may take advantage of the relation between local roughness and regional slope in order to produce catchment aspect ratios similar to the natural studied cases.
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Partitioning of horizontal deformation between localized and distributed modes in regions of obli... more Partitioning of horizontal deformation between localized and distributed modes in regions of oblique tectonic convergence is, in many cases, hard to quantify. Here we use the geometry of river basins and numerical modeling to evaluate modes and rates of horizontal deformation associated with the Arabia-Sinai relative plate motion in Lebanon. We focus on river basins that drain Mount Lebanon to the west and are bounded by the Yammouneh fault, a segment of the Dead Sea fault system that transfers left-lateral deformation across the Lebanese restraining bend. We quantify a systematic counterclockwise rotation of these basins and evaluate drainage area disequilibrium using the c metric. The analysis indicates a systematic spatial pattern whereby tributaries of the rotated basins appear to experience drainage area loss or gain with respect to channel length. A kinematic model reveals that since the late Mio-cene, 23%–31% of the relative plate motion parallel to the plate boundary has been distributed along a wide band of deformation to the west of the Yammouneh fault. Taken together with previous, shorter-term estimates, the model indicates little variation of slip rate along the Yammouneh fault since the late Miocene. Kinematic model results are compatible with late Miocene paleomagnetic rotations in western Mount Lebanon. A numerical landscape evolution experiment demonstrates the emergence of a similar pattern of drainage area disequilib-rium in response to progressive distributed shear deformation of river basins with relatively minor drainage network reorganization.
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This special issue collects a number of papers mainly reflecting discussions during the 'tectonic... more This special issue collects a number of papers mainly reflecting discussions during the 'tectonics, sedimentation and surface processes' sessions (TSSP) organized at recent EGU conferences (2012, 2013, 2014), as well as related studies that have appeared in Earth Surface Processes and Landforms over the last two years. The sedimentary record has long been used to invert for deformation at all scales and in all tectonics settings. Growth strata, sediment provenance, sequence stratigraphy and changing de-positional environments have all provided first-order constraints on quantifying deformation at a range of spatial and temporal scales. At the same time, these studies have motivated much work on the influence of tectonics on both sedimentation patterns and basin fill successions. However, relatively few studies have considered the whole integrated system of catchment erosion, fluvial transport and sediment deposition together, often concentrating on either the basin or the catchment separately. Recently however, methodolog-ical progress in quantifying rates of surface processes in the upstream erosion and transfer zones, as well as revived interest in the couplings between surface processes, tectonics and climate, have made it possible to renew our understanding of the interactions between sedimentation and tectonics within the framework of the whole integrated sediment routing system. Although the studies within this special issue are only a fraction of the work presented over the last five years of the TSSP sessions, the manuscripts presented here reflect a selection of the broad content and diversity of studies that integrate both sedimentation and surface processes to understand deformation in the context of sedimentary systems. They highlight and are organized into three active challenges of the field: (1) tectonics and climate into landscapes; (2) signal propagation within sediment routing systems; and (3) modeling of tectonic and surface processes.
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Glacial-interglacial cycles affect the processes through which water and rocks
are redistributed ... more Glacial-interglacial cycles affect the processes through which water and rocks
are redistributed across the Earth's surface, thereby linking the solid Earth and climate dynamics. Regional and global scale studies suggest that continental lithospheric unloading due to ice melting during the transition to interglacials leads to increased continental magmatic, volcanic and degassing activity. Such a climatic forcing on the melting of the Earth’s interior, however, has always been evaluated regardless of continental unloading by glacial erosion, albeit the density of rock exceeds that of ice by approximately three times. Here, we present and discuss numerical results involving synthetic but realistic topographies, ice caps and glacial erosion rates suggesting that erosion may be as important as deglaciation in affecting continental unloading. Our study represents an additional step towards a more general understanding of the links between a changing climate, glacial processes and the melting of the solid Earth.
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Earth-surface processes operate across erosionally dominated landscapes and deliver sediment to d... more Earth-surface processes operate across erosionally dominated landscapes and deliver sediment to depositional systems that can be preserved over a range of timescales. The geomorphic and stratigraphic products of this source-to-sink sediment transfer record signals of external environmental forcings, as well as internal, or autogenic, dynamics of the sedimentary system. Here, we evaluate environmental signal propagation across sediment-routing systems with emphasis on sediment supply, Qs, as the carrier of up-system forcings. We review experimental, numerical, and natural examples of source-to-sink sediment routing and signal propagation during three timescales: (1) historic, which includes measurement and monitoring of events and processes of landscape change and deposition during decades to centuries; (2) centuries to several millions of years, referred to as intermediate timescale; and (3) deep time. We discuss issues related to autogenic dynamics of sediment transport, transient storage, and release that can introduce noise, lags, and/or completely mask signals of external environmental forcings. We provide a set of conceptual and practical tools for evaluating sediment supply within a source-to-sink context, which can inform interpretations of signals from the sedimentary record. These tools include stratigraphic and sediment-routing system characterization, sediment budgets, geochronology, detrital mineral analysis (e.g., thermochronology), comparative analog approaches, and modeling techniques to measure , calculate, or estimate the magnitude and frequency of external forcings compared to the characteristic response time of the sediment-routing systems.
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High-resolution 32–20 Ma-old stratigraphic records from the Molasse foreland basin situated north... more High-resolution 32–20 Ma-old stratigraphic records from the Molasse foreland basin situated north of the Alps, and Gonfolite Lombarda conglomerates deposited on the southern Alpine margin, document two consecutive sedimentary responses-an immediate and delayed response-to slab breakoff beneath the central Alps c. 32–30 Ma ago. The first signal, which occurred due to rebound and surface uplift in the Alps, was a regional and simultaneous switch from basin underfill to overfill at 30 Ma paired with shifts to coarse-grained depositional environments in the foreland basin. The second signal, however, arrived several million years after slab breakoff and was marked by larger contributions of crystalline clasts in the conglomerates, larger clast sizes, larger sediment fluxes and shifts to more proximal facies. We propose that this secondary pulse reflects a delayed whiplash-type erosional response to surface uplift, where erosion and sediment flux became amplified through positive feedbacks once larger erosional thresholds of crystalline bedrock were exceeded. Progradation of coarse-grained material in foreland basins has been related to tectonic uplift, which accentuates erosion through the generation of steeper slopes 1 , or to shifts towards stormier climates, which enable the transport of larger clasts by more powerful floods 2,3. Most of these interpretations assume instantaneous process-responses, but recent physical models suggest that sediment supply signals linked with external perturbations can be buffered or even amplified 1,4,5 , with a possible time lag 6. Despite this progress, interpretations of depocenter progradation have remained non-unique mainly due to a lack of independent chronologies for the driving force in the hinterland where the sediment sources are, and the stratigraphic response in the adjacent sedimentary basin. Here, we approach this problem taking advantage of well dated 7–9 32–20 Ma-old sedimentary archives encountered at three sections within the Molasse foreland basin (Fig. 1a), and geochronological constraints from the adjacent European Alps 10–14. The Central European Alps (Fig. 1a) comprise a doubly-vergent nappe stack with a crystalline core of European origin exposed in the Lepontine dome (L on Fig. 1a) that straddles the subducting European plate 14. The present-day architecture of the orogen is the consequence of a subduction-collision history, which started with the subduction of the European oceanic lithosphere beneath the Adriatic continental plate and the closure of the Tethys Ocean during the Late Cretaceous 14. At c. 35 Ma, the European continental lithosphere entered the subduction channel, where the contrasts in flexural rigidities between the subducted oceanic lithosphere and the continental European plate induced extensional stresses within the slab, with the result that the oceanic lithosphere slab broke off 30–32 Ma ago 10–14 (Fig. 1b). Slab delamination was associated with the ascent of magmas to shallow crustal levels (e.g., Bergell intrusion labeled as B in Fig. 1a) 10–14 , rapid rock uplift and orogen-parallel extension in the rear of the Alps. Uplift and extension was accomplished through backthrusting along the Insubric Line (IL on Fig. 1b) and orogen-parallel slip along low-angle detachment faults 15–17. Backthrusting and related rock uplift resulted in the rise of the Alpine topography 18 , which in turn caused an increase in sediment flux 19 to the adjacent sedimentary basins. The rise of the Alpine topography continued until c. 25–20 Ma, when the mountain belt reached a cross-sectional width of c. 150 km and a total relief (i.e., elevation difference between the foreland basin and the major fluvial drainage divides in the Alps) of c. 1500–2500 m 18 that has been maintained until today 18 .
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Asf Association Des Sedimentologistes Francais, 2001
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Http Www Theses Fr, 2003
... 1 pour obtenir Le grade de: DOCTEUR DE L'UNIVERSITÉ DE RENNES 1 Mention Sciences de ... more ... 1 pour obtenir Le grade de: DOCTEUR DE L'UNIVERSITÉ DE RENNES 1 Mention Sciences de la Terre PAR Sébastien Castelltort Équipe ... que la ligne de rivage ou la transition sable-graviers dans les dépôts marins ou continentaux respectivement (Marr et al., 2000; Paola et al ...
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Agu Fall Meeting Abstracts, Dec 1, 2010
The Zagros Mountains are a spectacular example of a mountain belt that consists of crustal-scale ... more The Zagros Mountains are a spectacular example of a mountain belt that consists of crustal-scale folds with a regular spacing of ~15 km. Despite excellent geological constraints, the formation of these structures remains enigmatic. Here, we therefore use visco-elasto-plastic numerical models to understand the dynamics of the Zagros on geological time scales. Models with a brittle crust and a single basal salt layer produce fault-related deformation structures that are inconsistent with the data. If, on the other hand, we take into account the observation that there might be up to 3 intermediate weak layers within the brittle crust, our models produce crustal-scale folds with the correct wavelength. Physically, this is caused by a folding instability whose wavelength mainly depends on the friction angle of the crust and the viscosity of the detachment layers. By combining a new semi-analytical technique with independent constraints on the effective viscosity of salt, we show that the friction angle of the crust in Zagros should be smaller than ~10° to reproduce observations. Our results have implications for the deformation of the crust as they highlight the importance of thin detachment layers. Moreover, our results show how geological observations put constraints on the long-term rheology and dynamics of the crust.
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High-frequency stratigraphic cycles (10 s to 100 s ka) often show, at a specific location, an alt... more High-frequency stratigraphic cycles (10 s to 100 s ka) often show, at a specific location, an alternation of 'dynamic' (proximal- energetic), and 'non-dynamic' (distal-pelagic) processes with time. When sedimentation is syn-deformation, these processes tend respectively to fill-up tectonically-induced topography or to drape it. As a consequence, growth strata are alternatively thickened and isopach across the growth structure. High-resolution kinematic studies
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Fluvial networks determine to a large extent the structure and geometry of erosive landscapes in ... more Fluvial networks determine to a large extent the structure and geometry of erosive landscapes in mountain ranges. As a consequence it is fundamental to understand how they develop in order to reconstruct and predict landscape evolution in orogens. A particularly important problem with relevance for our future ability of "inverting" landscapes is the degree to which fluvial networks and basin
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Recent results from geomorphology show that frequent climate changes can induce high-frequency se... more Recent results from geomorphology show that frequent climate changes can induce high-frequency sediment flux variations at the outlet of the erosion zone. It is crucial to know how these are transmitted by rivers to the sedimentation zone in order to constrain the capacity of sedimentary accummulations to provide informations about past climate changes. The study of large river systems in
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Revue de Micropaléontologie, 2001
The sedimentological study of Arguis anticline in the Jaca basin (south-central Pyrenees, Spain),... more The sedimentological study of Arguis anticline in the Jaca basin (south-central Pyrenees, Spain), has shown the overall progradation of a deltaic system, which progressively overlap the structure since Bartonian. The Arguis Marl and Belsué-Atarés Formation which correspond to these sediments contain 206 species of benthic foraminifera. They represent outer and inner shelf depositional environments. Planktonic foraminifera define Morozovella lehneri (with
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Fluvial networks determine to a large extent the structure and geometry of erosive landscapes in ... more Fluvial networks determine to a large extent the structure and geometry of erosive landscapes in mountain ranges. As a consequence it is fundamental to understand how they develop and evolve in order to reconstruct and predict landscape evolution in orogens. A particularly important problem is the degree to which fluvial networks and basin boundaries evolve and change through their existence.
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The last two decades have been marked by a large amount of studies on the relative influences of ... more The last two decades have been marked by a large amount of studies on the relative influences of climate and tectonics on landscape evolution. Coevally, considerable advances have been achieved in numerical modelling of landscape evolution. These have been particularly useful in testing hypotheses and scenarios of the potential controls and feedbacks between climate, tectonics and landscape evolution. However, our
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Papers by Sebastien Castelltort
enous sediments from source to sink. Although it is widely accepted that rivers are perturbed by millennial-scale climatic variability, the extent to which these signals are buffered or trans- ferred down river systems to be recorded in sediments at or beyond the river mouth remains debated. Here, we employ a physically based numerical model to address this outstanding issue. Our model shows that river transport strongly amplifies high-frequency sediment flux variations arising from changing water discharge, due to positive feedback between discharge and the channel gradient. This behavior is distinctly different from short-period sediment flux signals (with constant water discharge) where the output sediment flux is strongly dampened within the river, due to negative feedback between the channel gradient and sediment concen- tration. We conclude that marine sedimentary basins may record sediment flux cycles result- ing from discharge (and ultimately climate) variability, whereas they may be relatively insen- sitive to pure sediment flux perturbations (such as for example those induced by tectonics).
are redistributed across the Earth's surface, thereby linking the solid Earth and climate dynamics. Regional and global scale studies suggest that continental lithospheric unloading due to ice melting during the transition to interglacials leads to increased continental magmatic, volcanic and degassing activity. Such a climatic forcing on the melting of the Earth’s interior, however, has always been evaluated regardless of continental unloading by glacial erosion, albeit the density of rock exceeds that of ice by approximately three times. Here, we present and discuss numerical results involving synthetic but realistic topographies, ice caps and glacial erosion rates suggesting that erosion may be as important as deglaciation in affecting continental unloading. Our study represents an additional step towards a more general understanding of the links between a changing climate, glacial processes and the melting of the solid Earth.
enous sediments from source to sink. Although it is widely accepted that rivers are perturbed by millennial-scale climatic variability, the extent to which these signals are buffered or trans- ferred down river systems to be recorded in sediments at or beyond the river mouth remains debated. Here, we employ a physically based numerical model to address this outstanding issue. Our model shows that river transport strongly amplifies high-frequency sediment flux variations arising from changing water discharge, due to positive feedback between discharge and the channel gradient. This behavior is distinctly different from short-period sediment flux signals (with constant water discharge) where the output sediment flux is strongly dampened within the river, due to negative feedback between the channel gradient and sediment concen- tration. We conclude that marine sedimentary basins may record sediment flux cycles result- ing from discharge (and ultimately climate) variability, whereas they may be relatively insen- sitive to pure sediment flux perturbations (such as for example those induced by tectonics).
are redistributed across the Earth's surface, thereby linking the solid Earth and climate dynamics. Regional and global scale studies suggest that continental lithospheric unloading due to ice melting during the transition to interglacials leads to increased continental magmatic, volcanic and degassing activity. Such a climatic forcing on the melting of the Earth’s interior, however, has always been evaluated regardless of continental unloading by glacial erosion, albeit the density of rock exceeds that of ice by approximately three times. Here, we present and discuss numerical results involving synthetic but realistic topographies, ice caps and glacial erosion rates suggesting that erosion may be as important as deglaciation in affecting continental unloading. Our study represents an additional step towards a more general understanding of the links between a changing climate, glacial processes and the melting of the solid Earth.