Impact of Surface Processes on the Growth of Orogenic Wedges: Insights from Analog Models and Case Studies1 J
ISSN 0016 8521, Geotectonics, 2010, Vol. 44, No. 6, pp. 541–558. © Pleiades Publishing, Inc., 2010.
Impact of Surface Processes on the Growth of Orogenic Wedges: Insights from Analog Models and Case Studies1 J. Malavieillea and E. Konstantinovskayab a Université Montpellier 2, CNRS UMR 5243, Lab. Géosciences Montpellier, 34095 Montpellier cedex 5, France, and International Laboratory, (LIA) “ADEPT”, CNRS NSC, France Taiwan e mail: [email protected] montp2.fr b Institut National de la Recherche Scientifique, Centre Eau, Terre et Environnement (INRS ETE), 490 rue de la Couronne, Quebec City, Quebec, Canada G1K 9A9 e mail: [email protected] Received March 23, 2010
Abstract—Interaction between surface processes and deep tectonic processes plays a key role in the structural evolution, kinematics and exhumation of rocks in orogenic wedges. The deformation patterns observed in analogue models applied to natural cases of present active or ancient mountain belts reflect several first order processes that result of these interactions. Internal strain partitioning due to mechanical behaviour of a thrust wedge has a strong impact on the vertical component of displacement of tectonic units that in return favour erosion in domains of important uplift. Such strain partitioning is first controlled by tectonic processes, but surface processes exert a strong feed back on wedge dynamics. Indeed, material transfer in thrust wedges not only depends on its internal dynamics, it is also influenced by climate controlled surface processes involving erosion and sedimentation. Effects of erosion are multiple: they allow long term localization of deformed domains, they favour important exhumation above areas of deep underplating and combined with sedimen tation in the foreland they contribute to maintain the wedge in a critical state for long time periods. The sim ple models illustrate well how mountain belts structure, kinematics of tectonic units and exhumation are determined by these complex interactions. DOI: 10.1134/S0016852110060075
1 INTRODUCTION ies chosen in various settings characterizing first order tectonic processes (Taiwan, Alps and Variscan belt) are The geologic history of orogenic wedges records then discussed in the light of the experiments. both the main phases of tectonic evolution and the coupled influence of deep geological (rheology and kinematics, metamorphism, magmatism) and surface GROWTH OF OROGENIC WEDGES processes (climate dependent erosion–sedimenta DURING CONTINENTAL SUBDUCTION tion) active along convergent margins. In recent years more attention has been paid on the mechanical and Orogenic wedges develop in subduction settings thermormechanical aspects of mountain building due to plate convergence involving large shortening offering a better understanding of the behaviour and and deformation of the crust (Fig. 1a). Two main sub deformation of the continental lithosphere in subduc duction settings characterize mountain building. The tion settings. Today, the major role of surface processes first one, oceanic subduction, concerns Andean type is highlighted in numerous studies dealing with the mountain belts formed by subduction of an oceanic evolution of orogens at different time and space scales. plate below a deforming continental margin upper For example, the role of erosion and sedimentation on plate. Continental subduction, the second one, con fault growth, exhumation processes and deformation cerns most of other mountain belts. This paper focuses history of accretionary orogens is widely studied on orogenic wedges of the second type, either due to through geological, experimental and numerical subduction of a continental margin under a continen approaches [e.g. 6, 14, 60, 79, 90, 93]. Here, insights tal plate following an Andean type oceanic subduc from simple sandbox models are used to show how the tion, or due to subduction of a continental margin interactions between surface processes and the under an intra oceanic volcanic arc (oceanic lithos mechanical behavior of the orogenic wedge influence phere upper plate) following intra oceanic subduc its structures, kinematics of deformation, exhumation tion [64, 66]. Continental subduction occurs after clo mechanisms, and global evolution. Several case stud sure of an oceanic domain that can be wide or narrow depending on the geodynamic setting. Subduction of 1 The article is published in the original. the lithospheric mantle induces deformation of the
541 542 MALAVIEILLE, KONSTANTINOVSKAYA
(a) orogenic wedge 0 input continental crust 30 S U.P. = Upper Plate U.P. lithospheric mantle km L.P. = Lower Plate t outpu L.P. S velocity discontinuity (b) rigid buttress sedimentation glass sidewall deformable U.P. erosion surface plastic sand cake sheet
S 10 cm décollement layer rigid base L.P. engine 3 m
Fig. 1. (a) Kinematic setting of continental subduction and (b) Schematic setting used for analogue modeling of thrust wedges. Backstop geometries and rheologies can be modified. Dotted line represents the chosen erosion surface. Sedimentation (when integrated) is performed by sprinkling sand. continental crust and controls the structural asymme of the continental crust, they can be activated (simul try of the mountain belt [33, 68]. This is well illustrated taneously or not) during the evolution of the orogen. today by various geophysical data (wide angle seismic Such a layering can be lithologic (e.g., basement cover transects and seismic tomography) from different interface, or weak layers in a sedimentary sequence), mountain chains [5, 10, 98]. They clearly show the rheologic (e.g., thermo mechanical changes during subduction of the lithospheric mantle and suggest that subduction or fluids pressure changes) or inherited it could drag the continental crust or part of it. from the early tectonic history (e.g., the structural her The study of oceanic accretionary wedges has itage of an extended margin prior to continental sub played a great role in the understanding of mountain duction). During mountain building, these weak building processes. What do we learn from oceanic zones have a major impact on the mechanical behavior accretion? Two major tectonic processes act along of the wedge [16, 87] as they constitute potential déc subduction zones: tectonic erosion (when material is ollement zones. How and where these décollements removed from the upper plate margin and dragged develop and how they influence the mechanics and through the subduction channel) and accretion (when structural evolution of the orogenic wedge are major material is removed from the subducting lower plate questions [90]. and accreted to the upper plate) [e.g., 56]. During Since the fundating works by Davis, Dahlen, and continental accretion, the whole or only part of the Suppe in the 1980s [30, 31], mountain belts have been incoming rock sequences is incorporated to the wedge often considered by geologists as crustal scale accre depending on the location of the décollements that tionary wedges [62, 78, 92] which deformation mech allow crustal material to be detached from the sub anisms can be satisfactorily described by a simple ducting plate. The part which is not involved in wedge Coulomb behaviour. The Coulomb theory gives a sim growth is dragged deeper into the mantle. At lithos ple mechanical setting allowing the definition of dif pheric scale, oceanic and continental subduction have ferent tectonic regimes depending on wedge stability: been described by a simple setting [e.g. 62] that was critical, undercritical, overcritical [e.g. 25]. Then, it used as a first order kinematic boundary condition for has been shown that orogens commonly adopt a dis many modeling approaches (Fig. 1). The location of a tinct geometry with a low tapered pro wedge facing velocity discontinuity (the “S point” in numerical the subducting plate, and a high tapered retro wedge models, e.g., [9]) determines the amount of accreted on the internal side [62]. This concept of doubly ver material (input) vs. subducted material (output) and gent accretionary wedge widely explored in the 1990s controls which part of the continental crust is sub [8, 35, 97] is still explored now [e.g., 74, 77, 81]. Ero ducted with the mantle (the whole crust or part of sion has rapidly been added as a major parameter to upper crust). In a thrust wedge, several kinematic sin the theory [26–29] because it exerts a significant con gularities exist mainly due to the mechanical layering trol on wedge mechanics. Removing material from the
GEOTECTONICS Vol. 44 No. 6 2010 IMPACT OF SURFACE PROCESSES ON THE GROWTH OF OROGENIC WEDGES 543 wedge surface induces a continuous deformation of and geophysics that are able to produce a global view the wedge changing the way for the critical state to be at a lithospheric scale, but this image is a “snap shot” maintained. If the tectonic (shortening) and climatic in time. conditions (erosional potential] remain stable, the The classical sandbox devices used (Fig. 1b) are wedge reach a dynamic steady state [6, 27, 44, 47, 95, made by a flat basal plate bound by two lateral glass 96] in which the incoming fluxes (accreted material) walls (see detail in: [14, 50, 51, 62]). A motor pulls a are compensated by the outgoing fluxes (material plastic sheet with a surface on which basal friction can removed by erosion). According to these models, the be chosen. A polished plastic film produces low basal velocity field of the crust and, hence, the exhumation friction and a rough plastic sheet surface simulates a paths of rock particles, depends on erosion at the sur high basal friction at the base of the layered incoming face [e.g. 45, 76]. Consequently, any changes in ero sand. The analogue granular materials deposited on sion rates potentially result in a modification of the the plastic sheet have frictional properties satisfying strain pattern [80] and thus the internal evolution of the Coulomb theory and they correctly mimic non the wedge [63]. linear deformation behaviour of crustal rocks in the The topography of mountain belts depends of the brittle field. The aeolian sand used in the experiments behaviour of continental rock units, depending itself is rounded with a grain size of less than 300 mm and a on fault grow and evolution. Models involving plastic density of 1690 kg/m3. The internal coefficient of fric [20, 97] or viscous [22] behaviour account well for dis tion is 0.57 and the cohesion Co = 20 Pa. The weak placements and produce velocity fields close to what décollement levels are created by introducing in the are observed in mountain belts, but they do not gener model thin (1–2 mm) layers of glass microbeads. They ate clear displacement discontinuities as faults did are a Coulomb material and their density and size are [67]. Thus, although the Coulomb wedge model gives almost the same as those of dry sand, however due to a rigorous mechanical frame to study the dynamics of their close to perfect roundness their coefficient of orogenic wedges, it presents some limits when study internal friction is about 23% smaller (0.44), with ing the internal structure and kinematics of deforma cohesion almost negligible. The successive colored tion which are mainly controlled by the heterogeneous sand layers are generally accreted against a rigid back nature of tectonic units and subsequent fault zones stop developing a Coulomb thrust wedge during con development. The critical wedge theory, is based on vergence. Scaling, and characterization of models and the hypothesis that orogens are everywhere on the analogue materials are discussed in [21, 32, 42, 43, 54, verge of internal failure along potential slip planes [31] 57, 61] and a clear synthesis is given in [41]. The rigid which do not allow strain localization along fault backstop simulates the undeformed part of the upper zones. Thus it does not account for deformation pro plate lithosphere. The basal plate length is 2.8 m cesses at the scale of individual tectonic instabilities allowing large convergence to be tested. It represents [e.g. 74]. Analysis becomes much more complex when the subducting lower plate lithosphere. introducing surface processes which interactions with An equivalent set up is used to study the influence tectonics induce changes in the mechanical state of of erosion and sedimentation on the internal structure the wedge at different time and length scales. and fault kinematics of model thrust wedges while maintaining a constant taper angle [14, 15, 50, 51]. Erosion is performed by hand with a thin metal plate MODELING PRINCIPLES AND TECHNIQUES (the sand being removed using a vacuum cleaner) to A lot of analogue experiments dealing with the maintain the slope of the wedge at a constant angle growth of thrust wedges have been performed since reflecting the mean taper angle imposed by wedge many years at Geosciences Montpellier laboratory mechanics. Erosion of the units was applied in a con giving insights for the general ideas discussed in this stant manner, independently of their compositional article. The analogue modeling approach presents sig nature, as a function only of topography. Thus higher nificant advantages providing quantitative and/or topographies and topographic anomalies were eroded qualitative estimations of experimental models [40]. It leading to erosion that is distributed and linearly accounts for tectonic instabilities, providing comple dependant on elevation. Generally this means that mentary informations on accretion processes and erosion is increasing towards higher topographies. deformation at the scale of discrete tectonic struc This is supported by other analogue models [e.g. 24, tures. Large convergence can be tested, that is neces 46], and also by observations from natural situations sary to take into account the widespread deformations where erosion can be positively correlated with eleva observed in subduction related mountain belts. In tion [91]. Sedimentation (when integrated) is per addition, experiments can integrate erosion and sedi formed in the foreland in the basin and on the deform mentation allowing us to characterize the impact of ing orogenic front (developing piggyback basins) by surface processes on the foreland/hinterland structure sprinkling sand [48, 58, 65] to fill the same average and evolution of mountain wedges. They provide a surface as used for erosion. Thus, results of models are dynamic view of long term processes involved in usefull to discuss the effects of several first order mountain building that is complementary to geology mechanical parameters on the deformation and struc
GEOTECTONICS Vol. 44 No. 6 2010 544 MALAVIEILLE, KONSTANTINOVSKAYA
backthrusting high angle taper accretion of new tectonic units by underthrusting
10 cm (a) HIGH BASAL FRICTION
low angle taper backthrust frontal accretion of new tectonic units
10 cm
(b) LOW BASAL FRICTION “basal décollement” backstop variable taper basal accretion frontal accretion “décollement 2”
10 cm
(c) DECOLLEMENTS “décollement 1”
10 cm mean surface slope
(d) “décollement 1” “décollement 2”
Fig. 2. Models without erosion showing the main mechanisms of wedge growth and corresponding critical taper: (a) high basal friction model, (b) low friction, (c) multiple décollements, (d) picture of a model with décollement. tural evolution of orogenic wedges submitted to ero for wedge growth: frontal accretion (décollement), sion. underthrusting (high basal coupling) and underplating (different decoupling levels acting at different depths within the wedge). High friction wedges are character GENERAL CHARACTERISTICS ized by a high taper angle and by growth occuring OF EXPERIMENTAL WEDGES SUBMITTED through underthrusting of long tectonic units bounded TO EROSION SEDIMENTATION by low angle thrusts. A major backthrust develops A selection of 2 D experiments without erosion is along the backstop whereas only few minor back first used to discuss the main mechanisms that are thrusts develop within the body of the wedge. Low fric involved in wedge growth and a second series involving tion wedges are characterized by a low taper angle and erosion and sedimentation, to highlight the impact of by growth through frontal accretion of new tectonic surface processes on wedge development. units involving forward propagation of a basal décolle ment. As the stress field is more symmetrical in the wedge (the main principal stress axis is close to hori Experiments without Erosion zontal), deformation commonly involves conjugate Figure 2 shows the geometry, structure and kine thrust faults leading to pop up structures formation matics of simple end member model wedges formed [e.g. 89]. Many backthrusts develop within the body of by accretion only. Three main mechanisms account the wedge allowing continuous thickening. In the both
GEOTECTONICS Vol. 44 No. 6 2010 IMPACT OF SURFACE PROCESSES ON THE GROWTH OF OROGENIC WEDGES 545 types of experiments, the birth and activity of thrusts is Two simple models, based on accretion of a homo not continuous during shortening. As new thrusts grow geneous material sequence (Fig. 3), illustrate the to propagate the deformation forward, former thrusts direct effect of erosion on structure and material trans or newly formed thrusts can be activated out of fer. They can be compared to the similar experiments sequence inside the wedge to allow the wedge to main without erosion of Fig. 2. In the eroded thrust wedges, tain an ideal “accretionary” critical) taper. The similar the diversity of exhumation patterns is controlled by wedge geometry was observed in experimental models the mode of fault propagation, itself depending on the with both for high and low basal friction even if the basal friction (high or low). The vertical component of rigid backstop was vertical [50, 51]. exhumation is generally higher for the wedges with high basal friction than for low friction wedges. The Wedges involving more than a basal decoupling uplift of material occurs along a cluster of sub vertical level present a more complex behavior (Fig. 2c). The thrusts in the middle part of the eroded thrust wedge presence of a weak décollement within the incoming with low basal friction. The material is exhumed along material will influence the thickening mechanisms of a series of inclined (20–50°) thrusts in the rear of the the wedge right from the start. Two main growth high friction wedge. The zone of maximum exhuma mechanisms will act simultaneously in different places tion is generally localized in the central portion of the of the wedge: 1—frontal accretion above the décolle thrust wedge and migrates towards the backstop with ment located within the incoming material and, 2— continued shortening. The vertical exhumation rate deep underplating of thrust slices (basal accretion) at increases with time, and the material accreted later is the rear of the wedge due to duplex formation along a rapidly transferred to the main exhumation zone, basal detachment. The resulting geometry and kine compared to the material accreted during the early matics of these two types of tectonic units are very dif stages. ferent. These accretionary processes will exert a strong influence on wedge topography which does not follow To analyze the impact of a décollement layer, a a simple slope (Fig. 2d). Various taper angles charac model wedge is constructed with a high basal friction terize different domains that directly depend of defor detachment and the presence of a low friction décolle mation partitioning in the thrust wedge. The low angle ment level (thin layer of glass microbeads) within the slope at the frontal part of the wedge is a consequence incoming sand layer (Fig. 3d). A 6° slope angle has of the low friction décollement, whereas the high been chosen for the imposed erosion profile to repre angle slope above the domain of underplating reflects sent an overcritical taper for a low basal friction wedge. the high friction behaviour of the lower basal detach The material located at depth below the weak layer is ment. In addition, a cyclical behaviour of the thrusting underplated under the rear part of the wedge, while regime has been recognized, with model wedges above the décollement the thrust wedge front is growth fluctuating between periods of frontal accre deformed mainly by frontal accretion (typical mecha tion and internal deformation by underplating [43]. nism for low friction wedge). After a large amount of shortening, the structure of the wedge is characterized by a particular organization of main thrust units. From Experiments with Erosion the frontal part of the wedge to the backstop respec tively, we have (Fig. 3d): (1) frontal imbricate of thrust Experiments accounting for surface processes sheets, (2) a synformal klippe of thrust units previously behave differently as erosion and sedimentation accreted to the front and progressively deformed, and, involve large material transfer which modify the wedge (3) an antiformal stack of underplated thrust units dynamics. Many parameters or boundary conditions refolding the upper décollement layer. During contin have been tested in order to determine their relative uous shortening, the kinematics of deformation importance [14, 15, 50, 51]. Only several experiments reflects the complex interaction between wedge giving significant insights for the understanding of mechanics and erosion. Underplating of the basal lay actual orogenic wedges will be described there. In ers (below the weak décollement level) is localized these experiments, a model thrust wedge is submitted under the frontal part of the proto wedge inducing the to erosion under flux steady state conditions as defined formation of a dome shaped structure. With contin in [96], i.e.: the volume of eroded material remains ued shortening, uplift and subsequent exhumation of equal to the volume of newly accreted material, main the underthrust units occurs along a series of inclined taining a constant surface slope during shortening. thrusts (20–40°). They progressively become steeper The slope angles, that reflect the basal frictional (up to 60–70°) due to vertical shearing that develops as strength, are maintained during shortening in the a consequence of material uplift at the back of the experiments with erosion and are further considered growing wedge. A high angle backthrust develops at to be “ideal” critical angles for accretionary wedge the rear of the thrust wedge affecting the proto wedge growth. Then, analysis of material transfer kinematics at the final stages of shortening. It controls the further across model thrust wedges allows an identification of upward transfer of the basal layers material within the the different modes of exhumation in response to ero area of maximum exhumation. The upper thrust sion. wedge develops above the décollement leading to fron
GEOTECTONICS Vol. 44 No. 6 2010 546 MALAVIEILLE, KONSTANTINOVSKAYA
(a) LOW BASAL FRICTION backthrust maximum exhumation
décollement frontal accretion 102 cm proto slope (b) HIGH BASAL FRICTION maximum exhumation erosion slope
accretion by underthrusting 96 cm
(c) + SEDIMENTATION
82 cm (shortening) décollement (d) DECOLLEMENTS 1
duplexing frontal accretion 21 cm particle paths 20 cm maximum exhumation antiformal stack 2
basal accretion frontal accretion
68 cm
2 1 2 + 1 synformal klippe décollement 3
underplating frontal accretion 115 cm (shortening)
Fig. 3. Models with erosion (flux steady state) showing particle paths (dotted lines) and domains of maximum exhumation: (a) low friction wedge (asymmetric divergent orogen), (b) high friction wedge (monovergent orogen), (c) syn tectonic sedimentation and erosion, syntectonic sedimentary layers (yellow in color) are involved in the wedge structure, (d) impact of décollements. Model evolution shows the partition of deformation, particle paths (dotted lines) and domains of maximum exhumation: 1— frontal accretion and basal duplex formation, 2—and stacking of basal units (underplating), 3—frontal accretion, growth of the antiformal stack, passive refolding of former imbricate thrusts of the upper wedge and backthrusting. One segment of the scale bar is 1 cm for (a), (b) and (d) and 5 cm for (c).
GEOTECTONICS Vol. 44 No. 6 2010 IMPACT OF SURFACE PROCESSES ON THE GROWTH OF OROGENIC WEDGES 547
upper plate rocks (orogenic lid) 1
L–P
erosio n surface U–P 2 1 1 2 2
antiformal stack frontal imbricate vertical shear brittle 3 1 1 2 2 3 3 underplating
ZOOM
1 4 1 2 2 3 ductile 3 4 4
Fig. 4. Sketch showing four stages of wedge development outlining deformation partitioning and kinematics of thrust units. Sim plified from models with décollements and submitted to erosion. Notice the passive deformation of upper plate (orogenic lid) resting on top of the former refolded décollement . Early folds are suggested to show evolution of U–P geometry. A possible defor mation mechanism responsible for vertical shear inducing stretching and thinning of the underplated units is schematized. Resulting strain is shown by the green ellipsoids. U–P pre structured upper plate passively deformed during underplating (parts of the foreland basin can be included in); L–P—basement rocks lower plate. tal imbrication of thrust sheets. When incorporated to From Submarine to Sub Aerial Wedges, Impact the wedge, the thrust units are deformed and become of Surface Processes on Tectonics progressively steeper, to near vertical due to continued shortening and surface erosion. The former thrust The series of experiments examined here shows units of the upper wedge are compressed, between the that simple thrust wedges can behave in a complex growing antiformal stack and the frontal imbricate, manner, even when simple and homogeneous materi leading to the formation of a synformal “klippe” com als are used. They also outline the impact of material pletely detached from the basal layers of the model transfer (erosion–sedimentation) on wedge structure (Fig. 3d). A detailed analysis of the experiment and a and dynamics. Thus, when applied to nature, models movie showing an experimental run is available in [50, suggest that erosion can strongly modify the structural 51]. The singular kinematics of “décollements type evolution of sub aerial wedges relative to submarine expériments” is illustrated as a sketch in Fig. 4. ones [85, 86].
GEOTECTONICS Vol. 44 No. 6 2010 548 MALAVIEILLE, KONSTANTINOVSKAYA
Impact on Structure, Strain Partitioning, Coulomb wedge theory supports the idea that when Faults Kinematics and Exhumation the mechanical state of a wedge changes from critical to overcritical, gravitational forces may cause local Analog models have shown that simple accretion extension and subsequent normal faulting [e.g. 30]. ary wedges can behave according to tectonically com Indeed, if there is no (or only minor) erosion, normal plex patterns. They present a punctuated thrust activ faults are required in the wedge body for exhumation ity during convergence and they show sustained local to occur, for example in submarine prisms where grav ized deformation. Internal deformation mechanisms ity induced material transfer can occur. Such explana and faults control the shape, topography, taper vari tions have been widely extended to mountain belts ability and structural evolution of the wedge. décolle [e.g. 78]. Nevertheless, it is sometimes difficult to ments play a major role allowing duplex formation and explain why a purely extensional deformation would underplating at different structural levels within the have initiated during convergence in deep parts of wedge whereas frontal accretion characterizes defor mountain belts. If we check the effect of erosion and mation in the piedmont (foreland zone). As strong piedmont sedimentation on wedge dynamics in a sta partitioning of deformation occurs in thrust wedges, bility field diagram [25], it decreases the slope angle this exerts a major influence on topography and as a and as a consequence displaces the stability field, direct consequence on the degree of local erosion. In favoring an evolution from overcritical to stable or return, erosion and sedimentation which influence from stable to undercritical state [e.g. 59]. This trend material transfer from the surface have a direct control does not favor extension. Thus, although extension is on the internal dynamics of the experimental wedge, and so one can obtain a feed back loop. commonly invoked to explain exhumation of meta morphic rocks and synchronous enigmatic normal Exhumation of metamorphic rocks remains a faults observed in orogenic wedges, in many cases, this major question for geologists working in mountain cannot be the dominant mechanism [72]. Experi belts. Many papers dealing with exhumation problems ments suggest an interesting alternative way to develop have been published to date, some focusing on early deep crustal scale normal shear zones and superim exhumation of very high pressure rocks in subduction posed brittle normal faults in the uppermost crust dur channel settings [79], others on exhumation processes ing compressional tectonics associated to continental in the frame of the orogenic wedge itself. We focus here subduction. Normal faulting could be the result of a on material transfer in orogenic wedges submitted to purely kinematic effect of the vertical shear induced by erosion. To analyze the kinematics of material transfer, strain partitioning in the orogenic wedge (Fig. 4). particle paths have been studied in numerical [e.g. 29] Such partitioning being the direct consequence of or experimental wedges [e.g. 50, 51]. They define an deep underplating processes which combined with accretionary flux directed from bottom to top in the surface erosion induces strong uplift within discrete wedge body explaining the vertical advection of mate areas. Differential motion of underplated crustal units rial at the origin of thickening and relief development. relative to surrounding material induces vertical shear Without erosion, these paths do not represent exhu and as a consequence a strong stretching and layer par mation paths; they only reflect uplift of material or allel thinning of the stacked tectonic units. At depth uplift of topography [e.g. 36]. Thus, exhumation in these zones are characterized by the development of orogenic wedges requires erosion (or at least normal shear zones with normal sense shearing evolving to faulting). Indeed, the type of exhumation depends on the brittle normal faults when reaching upper crustal internal dynamics of thrust wedges and conversely, on domains during continuous synconvergence erosion how this dynamics is modified by erosion [e.g. 17, 45]. assisted uplift. Experiments with erosion show that local uplift induced by underplating can generate localized high angle slopes in the wedge. If applied to nature, such CASE STUDIES deformation mechanisms occurring at depth in oro genic wedges would favor strong erosion and high den Three case studies taken from different orogens are udation rates above domains of underplating. In the discussed here, each of them being chosen to outline same manner, that the portion of the wedge located specific processes enlighted by results of analogue between the underplating domain and the domain of models. The Taiwan case illustrates well the strong active frontal accretion does not undergo strong defor partitioning of deformation that develops during rapid mation, its angle of slope remains low, inducing only convergence. The Western Alps case shows the role of minor erosion and consequently minor exhumation. sedimentation in the foreland and the impact of Thus, due to internal strain partitioning [e.g. 49], den Mesozoic extensional structural heritage. The last udation rates will vary along a mountain belt transect Variscan case shows how the interpretations of major because erosion controlled exhumation is very sensi geologic features in a mountain belt may evolve tive to the vertical component of displacements in the through time depending on the processes that are wedge. enlighted.
GEOTECTONICS Vol. 44 No. 6 2010 IMPACT OF SURFACE PROCESSES ON THE GROWTH OF OROGENIC WEDGES 549
(a) Central Range Foothills 2nd zone of exhumation Volcanic arc underplating ~3 cm/yr W ~4 cm/yr ~2 cm/yr E
km 10 ~9 cm/yr U.P. L.P. 20 1st zone of Eurasian Plate underplating 050 km maximum refolded décollement (b) exhumation
p
o
U.P. t
ks
cm c
a
5 b L.P. basement décollement 0 Tectonic frontal synformal underplated units U.P. = Upper Plate units imbricate thrust stack antiformal stack L.P. = Lower Plate
Fig. 5. (a) Interpretive geological section of Taiwan orogenic wedge inspired by (b) experiment with décollement and erosion. Medium term shortening rates on main active faults are indicated.
Taiwan: Partition of Deformation in a Young detailed study of their interaction with active tectonic and Very Active Mountain Belt processes on the Island. In the domain of active continental subduction, Taiwan is recognized as one of the best places in the where the sub aerial orogenic wedge is growing today, world to address major questions concerning mecha estimates of long term shortening rates on active faults nisms of lithospheric deformation in convergent set and wedge deformation show a surprising behavior tings, processes of mountain building (from oceanic (Fig. 5a). Most of the shortening is accounted for by subduction to continental subduction), and subse just a few major faults, on the western side of the wedge quent deformation involving large seismogenic faults. in the foreland and on its backside against the Philip In this area, the obliquity of the plate convergence pine Sea upper plate onland along the Longitudinal involves the progressive subduction of the continental Valley and offshore the Coastal Range, the accreted margin of China inducing the fast growth of the Tai part of the Luzon Volcanic arc. Indeed, recent studies wan mountain belt. Due to the high convergence rate along a transect in Central Taiwan have revealed that (~8 cm/yr) and the complex interaction (doubly verg ~4 cm/yr of the total convergence across the plate ing oceanic and continental subduction) between the boundary have been absorbed on the long term across converging Eurasia and Philippine Sea plates (PSP), the most frontal faults of the sole foreland [83]. On the deformation rates and erosion rates are extreme (hor other side of the wedge, further east, about 3 cm/yr of izontal shortening > 2 cm/yr on major faults, local ver shortening is accounted for by the active faults of the tical motions up to 3 cm/yr). In fact, erosion processes Longitudinal Valley [3, 82] and offshore within the triggered by the subtropical climate can often be cata PSP (~2–3 cm/yr) along the submerged flank of the strophic (landslides induced by Typhoons and earth Coastal Range [66]. This is confirmed by the intense quakes, flooding), thus sculpting the sharp relief of the seismic activity, both onshore and offshore eastern Island. Today, the orogen culminates at about Taiwan reflecting deformation of the backside of the 4000 meters, having risen from sea level in only a few orogenic wedge against the Philippine Sea upper plate million years. The impact of climate and surface pro indenter. Thus most part of the bulk shortening occurs cesses are thus particularly well expressed allowing today on foreland faults and along the backside of the
GEOTECTONICS Vol. 44 No. 6 2010 550 MALAVIEILLE, KONSTANTINOVSKAYA
10 cm
Upper Plate
(a) Duplexing
antiformal stack 10 cm Syn tectonic U.P. Klippe deposits Upper Plate
Lower Plate (b) Underplating
NW Alps present day cross section [18] Helvetic nappes Subalpine Prealpes Molasse SE NW Molasse klippen Penninic nappes Jura basin km Autochthonous European basement Upper Plate –10 mid cru Crystalline Massifs stal deta –20 chment (c) 050100 150 200 km
Fig. 6. (a) Model simulating structural heritage of a continental margin without erosion to be compared to (b) same model with erosion and syntectonic sedimentation applied to the Alps, (c) present day geologic section across the Swiss Alps (from [18]). mountain belt, leaving little (if any) horizontal short analog models and thermo kinematic numerical ening within the body of the wedge. Estimates of the models [84] involving erosion in which underplating at vertical and horizontal components of deformation, depth sustains the growth of the orogenic wedge, compared at different spatial and time scales (ranging account well for the observed geologic structure, from long term to short term evolution), suggest a recent kinematic evolution and exhumation. strong partitioning of deformation. If compared with analog models of erosional wedges, such a kinematic pattern and deformation partitioning matches closely Alps: Subduction of a Pre Structured Continental the behavior of experiments with décollement s (Fig. 5b). Margin and Foreland Basin Evolution This suggests that the main mechanisms of growth can Examination of classical geologic sections across be described by frontal accretion in the foreland Foot the Swiss Alps [37], reveals how the current structural hills and underplating of tectonic units at depth under pattern has been controlled by the structural and sedi the hinterland, involving strong uplift, exhumation mentary features inherited from Mesozoic extensional and backthrusting in the Philippine Sea upper plate. tectonics. It also underscores the importance of sur Intra crustal décollements localized within the sub face processes in the structural evolution of a moun ducting continental margin of Eurasia favor such a tain belt. To better characterize deformation mecha style of deformation partitioning and wedge growth. nisms involved in the subduction of a pre structured Normal faulting that affects the eastern flank of the continental margin, a series of analogue experiments Central Range [23], could be related to the strong dif have been conducted [13–15]. The initial geometry ferential uplift occurring between the growing range and rheologic structure of the basic models (Fig. 3, and the volcanic arc upper plate (as schematized on [14]) have been designed using data from a restored Fig. 4). Together with new constraints on the thermal section across the western Alps proposed by [18]. The evolution [11] and exhumation of the Central Range, aim of our experiments was three fold:
GEOTECTONICS Vol. 44 No. 6 2010 IMPACT OF SURFACE PROCESSES ON THE GROWTH OF OROGENIC WEDGES 551
—to better understand the impact of erosion—sedi at different structural levels in a thrust wedge and can mentation changes on the tectonic structure and the affect simultaneously or successively different parts of evolution of the Alpine wedge, the subducted crust. —to analyse the role played by former structural Décollement induced deformation partitioning heritage in the tectonic evolution, and largely controls particle trajectories and strain pat —to determine the relative influence of these terns. One way to investigate orogen dynamics is to parameters on the main tectonic events recorded in a look at the ages recorded by different thermochro foreland during the evolution of an orogenic belt. Here nometers across it [53, 96]. Exhumation of rocks two analogue models are compared to the geological means the approaching of a rock particle to the Earth’s section, the first is run without erosion and the second surface, which is, e.g. recorded by cooling rates calcu with erosion (Fig. 6). Without surface processes, we lated from thermochronologic data [e.g. 39], whereas obtain a classically shaped high friction wedge. In uplift of rocks means the displacement of rocks with response to shortening, basement imbricates first respect to the geoid, or less accurately with respect to overthrust each other using inherited weaknesses. the mean sea level [36]. The study of material paths Then, the unstructured part of the basement sponta (trajectories) in mountain belts may provide useful neously underthrusts allowing a critical taper to be insight on their kinematic evolution. Surface processes maintained. With erosion and sedimentation, the strongly influence the timing, localization and ampli models grow differently by frontal accretion in the tude of rock displacements in the varying members of foreland basin and by simple underthrusting and sub an orogenic wedge. The comparison of their trajecto sequent underplating in the hinterland. The combined ries in experiments performed with and without ero effect of tectonics and erosion leads to strong focus sion–sedimentation underscores the influence of sur sing of exhumation in the domain of underplating. face processes on material transfer in the model wedge Subsequent uplift isolates the front of the lid forming a [e.g. 24]. The variations in rates of erosion and sedi synformal klippen nappe composed of former imbri mentation modify the extent, the morphology, the cated thrust units. Frontal accretion therefore leads to structures, the timing of development and the material a cyclic syndeformational removal of a substantial vol paths in the different models. Particles located in the ume of foreland sediments. At the end of shortening, converging lower plate or in the upper plate show the different units have been largely eroded and partic complex uplift paths related to deformation partition ularly the foreland basin and the orogenic lid including ing and various tectonic stages. its frontal klippe come to rest upon syntectonic depos Thus, exhumation rates calculated on the basis of its. Underplated duplexes lead to the formation of an simulated thermochronometry without knowledge of antiformal nappe stack where the displacement is the particle trajectories and internal structure may accommodated along thrust ramps, favoring localized result in erroneous estimations. Indeed, at the scale of rapid syn convergence exhumation. Then, the anti a mountain belt each tectonic unit may record an indi formal structure reaches the surface where it appears vidual specific exhumation path. as a tectonic window. Experiments involving sedimentation show the In the experiments, the structural heritage of the effect of erosion on the development of a foreland lower plate (weak levels of glass beads in the basement) basin. They outline that if the erosion/sedimentation defines the size of thrust units and favors the initiation budget is not balanced in the sense that much more of underplating, but the process then continues spon material is removed from the system than is deposited taneously in the homogeneous part of the basement (output > input), an important record of the tectonic due to burial and increasing “lithostatic” stress at history of the orogenic wedge is missing. This is equiv depth (Fig. 6b). Models suggest that for natural oro alent to the natural situation in the Alpine foreland genic wedges, when convergence can no longer be basin, where more than half of the sediments have mechanically accommodated by subduction of lower been carried out of the system by large rivers into the plate basement units at depth, deformation is taken up neighbouring sinks that are the Black Sea, North Sea by underplating. This mechanism allows the tectonic and Mediterranean Sea [52]. In addition, as parts or units detached from the subducting lower plate to be entire units of the foreland basin are incorporated to accreted to the upper plate, contributing to wedge the orogenic prism [e.g. 73], and then vanish during growth. It requires intra crustal décollement zones, mountain growth, section balancing techniques are the location of which is controlled by the kinematics of frequently inappropriate and can lead to a significant subduction, the thermo mechanical conditions in the underestimation of the amount of shortening recorded wedge, the structural heritage and by erosion. Various in a foreland. processes of crustal decoupling exist during continen Specific models suggest that depending on the tal subduction, at great depth [e.g., 19], or in the oro behavior of the backstop upper plate, underplating genic wedge due either to fluid overpressure inducing induced deformation at the back part of the wedge and weak crustal zones of strain concentration along brittle associated material transfer paths will change during or plastic shear zones or weak décollement layers in continuous shortening. During the growth of an anti the sedimentary cover. Thus, underplating can develop formal stack, the tectonic units are first strongly
GEOTECTONICS Vol. 44 No. 6 2010 552 MALAVIEILLE, KONSTANTINOVSKAYA
(a) Albigeois Permian (b) nappes basin U.P. FRANCE NS Stephanian AZ basin Massif central L.P. VFB
SFN 500 km Visean flysch basin section 10 km
normal shear zone (c)
N U.P. S AZ SFN PCB NS VFB
L.P.
Underthrust basement 10 km
Fig. 7. (a) Location of the Montagne Noire in the French Massif Central. (b) Structural map of the area showing the main tec tonostratigraphic units: PCB, Permian and Upper Carboniferous basins; NS, Northern Slope; AZ, Axial Zone; SFN, Southern Fold Nappes; VFB, Visean Foreland Basin. (c) Interpretive cross section of the Montagne Noire showing an alternative hypoth esis for dome formation and enigmatic normal shear zone and faults observed on its northern flank. The southern recumbent fold nappes emplaced on the foreland basin are passively deformed during development of the Axial Zone antiformal stack. stretched and thinned to accomodate the differential and micaschists (lower plate) of Proterozoic to Cam uplift imposed by the combination of stacking mecha brian age, flanked and overlain by low grade Palaeo nisms and surficial erosion. Then, when the upper zoic cover series (upper plate). The area has tradition plate becomes thinner due to the effect of uplift and ally been subdivided into three main tectonostrati continuous erosion, more localized backthrusting graphic units from the internal domains of the belt to deformation may develop, changing the material the foreland respectively: 1—the Northern Slope transfer path. Such an evolution may apply to the final evolution of the Alpine orogenic wedge (Fig. 6c). upper plate with a southward tectonic vergence is composed by low grade lower Paleozoic foldeciand faulted metasedimentary units; 2—the Axial Zone Variscan Montagne Noire: Formation of Gneiss Domes lower plate is a high grade metamorphic antiform of and Enigmatic Normal Faults foliation made of gneisses, migmatites and micaschists of Proterozoic to Ordovician age. The gneissic rocks of The Variscan orogen developed during the Gond the dome are characterized by a complex deformation wana–Laurasia collision with progressive migration of pattern with superimposed shearing deformation and crustal thickening to external parts of the belt from Devonian to Middle Carboniferous times accompa a coaxial strain in the core of the antiformal structure: nied by a Barrovian type metamorphism and progres 3—the kilometer scale recumbent fold nappes of the sive southward thrusting [e.g., 69]. The Montagne Southern Slope (upper plate) are composed of low Noire forms the southernmost part of the French grade Paleozoic sequences. Visean flysch sediments Massif Central resulting from this Variscan history including synorogenic olistolites are involved in the (Fig. 7a). It consists of a core of gneisses, migmatites nappe deformation. These sediments characterize the
GEOTECTONICS Vol. 44 No. 6 2010 IMPACT OF SURFACE PROCESSES ON THE GROWTH OF OROGENIC WEDGES 553
(a) 0 U–P crust 30 L–P km UH P rocks
subduction channel mantle
(b) 0 crust 30 km
underplating mantle
(c) 0 crust 30 km
underplating mantle
(d) backthrusting Klippe 0 U–P Upper Plate crust 30 L–P Lower Plate km underplating mantle UH–P rocks domains of important uplift and strong erosion
Fig. 8. Conceptual model showing the impact of surface processes on deformation partitioning, kinematics and exhumation dur ing orogenic wedge growth: (a) end of oceanic subduction stage (early exhumation of high pressure rocks in the subduction chan nel), (b) subduction of the continental margin involving deep stacking of underplated crust units and strong uplift controlled ero sion of the upper plate, (c) deep underplating continue and a new stage of underplating begins in the foreland involving inverted inherited features of the margin, (d) during the late stage, the foreland basin is involved in frontal accretion whereas major back thrusting develops at the back of the wedge due to strong thinning of the upper plate lid by erosion. foreland basin developed during the final growth of the [1, 2]). The steep north dipping fault zone bounding Variscan orogenic wedge. the Axial Zone–Northern Slope tectonic units is The upper plate nappes units are separated from characterized by polyphase deformation including a high grade lower plate basement units by major fault later outstanding normal sense shearing. Molasse type zones that have recorded a complex pattern (or his sediments of Stephanian B (Upper Carboniferous) tory) of deformation (see detailed tectonic analysis in age are exposed in a narrow strip north of this bound
GEOTECTONICS Vol. 44 No. 6 2010 554 MALAVIEILLE, KONSTANTINOVSKAYA
U.P. foreland basin W erosion level E
2 1 L.P. basement Underplating 50 km
Fig. 9. Interpretive cross section of the variscan belt from NW Spain, modified from [75], suggesting that two different domains of underplating (1 in the hinterland, 2 in the foreland) controls the structure of the wedge and the location of uplift related normal sense shear zones. ary. The deposition of these rocks in intermontane the light of the above suggested alternative explana basin and the development of normal shear zones have tion, which does not require such major changes in the been related to late orogenic extension [34] involving general compressional tectonic regimes. the growth of an extensional metamorphic core com plex, the Axial zone [94]. The Montagne Noire may be a sort of “Metamorphic core complex”, but how was it CONCLUSIONS formed? The large variety of models proposed for this Interaction between surface processes and deep unique structure, do not take into account the proba tectonic deformation processes plays a key role in the bly fundamental role of erosion. Some invoke: a com structural evolution, kinematics and exhumation of pressive anticline (tectonic forces dominant, e.g., [4]), rocks in orogenic wedges. Insights from analog models diapiric uplift or wrenching and diapirism (combined applied to natural cases of present active or ancient tectonic and buoyancy forces, [38]), transtensional mountain belts allow us to emphasize several first Metamorphic Core Complex (tectonic forces domi order processes that result from these interactions. nant and buoyancy forces, e.g., [34, 88]), extensional Internal strain partitioning due to mechanical behav Metamorphic Core Complex (buoyancy forces domi ior of the thrust wedge has a strong impact on the ver nant during late orogenic extension, e.g., [94]), or, tical component of displacement of tectonic units, ductile thickening and gravitational collapse (com which in turn favors erosion in domains of strong bined tectonic and buoyancy forces, e.g., [2]). Obser uplift. During continental subduction, the role of déc vation of experiments with erosion now allows discus ollements can be major as they permit strain partition sion of two end member hypotheses. In the Metamor ing in the orogenic wedge as it is shown in the example phic Core Complex model, exhumation is mainly of the Taiwan orogen. They can result from the struc related to the development of a crustal scale low angle tural heritage of the continental margin (inherited detachment fault during widespread late orogenic structures from the rifting event that preceeds ocean extensional tectonics. The suggested alternative inter opening), and/or from the rheologic layering of the pretation (Fig. 7) favors combined uplift (induced by crust (either due to thermo mechanical behavior of underplating of basement units) and erosion acting the continental crust or weak zones in sedimentary simultaneously during the main events of the conver cover rocks). gent history of the orogen as a dominant process driv Such a strain partitioning is first controlled by tec ing exhumation. This synconvergence mechanism tonic processes, but surface processes exert a strong accounts well for the geometry of tectonic units, fault feed back on wedge dynamics. Indeed, material trans kinematics and metamorphic relationships between fer in thrust wedges not only depends on its internal the high grade core zone and the surrounding low dynamics, it is also influenced by climate controlled grade nappes. This tectonic history does not exclude surface processes including erosion and sedimenta the late orogenic reworking of the area by extensional tion. The effects of erosion are multiple: erosion and/or wrench faulting which characterize late stage allows long term localization of uplifted domains, it Variscan tectonics. favors strong exhumation above areas of deep under Misleading may also concern the interpretation of plating and combined with sedimentation in the fore normal faults or ductile normal sense shear zones land can contribute to maintain the wedge in a critical observed in Alpine type mountain belts. Indeed, many state for long periods of time. Our simple models illus antiformal gneissic domes (Gran Paradiso, Ambin, trate well how mountain belts structure, kinematics of Dora Maira, Tauern window) from the internal Alps tectonic units and exhumation can be determined by are locally bounded by normal sense shear zones and these complex interactions (Fig. 8). In addition, they brittle normal faults, leading to interpretations in offer an explanation for syncontractional development terms of a relatively late and deep seated extensional of normal sense shear zones and faults at the backside faulting due to gravitational collapse (extensional of underplated tectonic units observed in the discussed metamorphic core complexes) could be revisited in examples of the orogenic wedges of Taiwan, Alps and
GEOTECTONICS Vol. 44 No. 6 2010 IMPACT OF SURFACE PROCESSES ON THE GROWTH OF OROGENIC WEDGES 555
Variscan Montagne Noire. Many other mountain belts 11. O. Beyssac, M. Simoes, J. P. Avouac, K. A. Farley, where underplating is suspected, such as the Alps, Y. G. Chen, Y. C. Chan, and B. Goffé, “Late Cenozoic Himalaya [12], Variscan belt of NW Spain ([7]; see Metamorphic Evolution and Exhumation of Taiwan,” Fig. 9, modified from [75]), Oman [70], New Cale Tectonics 26, TC6001, (2007) doi: donia [55], Alpine Corsica [71] and many other places 10.1029/2006TC002064. exposing similar structures such as exhumed antifor 12. L. Bollinger, J. P. Avouac, O. Beyssac, E. J. Catlos, mal metamorphic domes bounded by normal fault T.M. Harrison, M. Grove, B. Goffé, and S. Sapkota, zones need to be revisited in the light of the general “Thermal Structure and Exhumation History of the Lesser Himalaya in Central Nepal,” Tectonics 23, mechanisms here outlined. TC5015 (2004), doi: 10.1029/2003TC001564. 13. C. Bonnet, Interactions between Tectonics and Surface ACKNOWLEDGMENTS Processes in the Alpine Foreland: Insights from Analogue Model and Analysis of Recent Faulting (Geofocus, Uni During the last ten years, the modeling method and versite de Fribourg (Suisse), Fribourg, 2007), vol. 17, the techniques in Montpellier have been considerably No. 1551, p. 196. improved, in particular due to the contribution of 14. C. Bonnet, J. Malavieille, and J. Mosar, “Interactions S. Dominguez with the technical assistance of between Tectonics, Erosion, and Sedimentation during C. Romano. A. Delplanque is acknowledged for the Recent Evolution of the Alpine Orogen: Analogue improvements of the figures. We are grateful to Modeling Insights,” Tectonics 26, TC6016 (2007), doi: Yu.A. Morozov and M.A. Goncharov for constructive 10.1029/2006TC002048. remarks that helped to improve the manuscript. 15. C. Bonnet, J. Malavieille, and J. Mosar, “Surface Pro cesses Versus Kinematics of Thrust Belts: Impact on Rates of Erosion, Sedimentation, and Exhumation— REFERENCES Insights from Analogue Models,” Bull. Soc. Geol. 1. D. G. A. M. Aerden, “Tectonic Evolution of the Mon France 179 (3), 179–192 (2008). tagne Noire and a Possible Orogenic Model for Syn 16. J. P. Brun, “Deformation of the Continental Litho Collisional Exhumation of Deep Rocks, Hercynian sphere: Insights from Brittle Ductile Modes,” Geol. Belt,” France Tectonics 17, 62–79 (1988). Soc. Spec. Publ. 200, 355–370 (2002). 2. D. Aerden and J. Malavieille, “Origin of a Large Scale 17. D. W. Burbank, “Rates of Erosion and Their Implica Fold Nappe in the Montagne Noire, Variscan belt, tions for Exhumation,” Mineral. Mag. 66, 25–52 France,” J. Struct. Geol. 21, 1321–1333 (1999). (2002). 3. J. Angelier, H. T. Chu, J. C. Lee, and J. C. Hu, “Active 18. M. Burkhard and A. Sommaruga, “Evolution of the Faulting and Earthquake Risk: the Chihshang Fault Western Swiss Molasse Basin: Structural Relations with Case,” Taiwan. J. Geodyn. 29, 151–185 (2000). the Alps and the Jura Belt,” Geol. Soc. Spec. Publ. 134, 4. F. Arthaud, “Etude Tectonique et Microtectonique 279–298 (1998). Comparée de Deux Domaines Hercyniens: les Nappes 19. N. Carry, F. Gueydan, J. P. Brun, and D. Marquer, de la Montage Noire (France) et l’Anticlinorium de “Mechanical Decoupling of High Pressure Crustal l’Iglesiente (Sardaigne), Publications de l’Université Units During Continental Subduction,” Earth Planet. des Sciences et Techniques du Languedoc, Montpel Sci. Lett. 278 (1–2), 13–25 (2009), doi: lier, Serie Géologie Structurale , 175 (1970). 1 10.1016/j.epsl.2008.11.019. 5. J. P. Avouac, “Mountain Building, Erosion, and the Seismic Cycle in the Nepal Himalaya,” Advances Geo 20. W. M. Chappie, “Mechanics of Thin Skinned Fold phys. 46, 1–80 (2003). and Thrust Belts,” Geol. Soc. Am. Bull. 89, 1189– 1198 (1978). 6. J. P. Avouac and E. G. Burov, “Erosion as a Driving Mechanism of Intracontinental Growth,” J. Geophys. 21. P. R. Cobbold, S. Durand, and R. Mourgues, “Sandbox Res. 101 (8), 17747–17769 (1996). Modelling of Thrust Wedges with Fluid Assisted Detachments,” Tectonophysics 334, 245–258 (2001). 7. C. J. Banks and J. Warburton, “Mid Crustal Detach ment in the Betic System of Southeast Spain,” Tec 22. D. S. Cowan and R. M. Silling, “A Dynamic, Scaled tonophysics 191, 275–289 (1991). Model of Accretion at Trenches and Its Implications for 8. C. Beaumont, P. Fullsack, and J. Hamilton, “Erosional the Tectonic Evolution of Subduction Complexes,” J. Geophys. Res. (B11), 5389–5396 (1978). Control of Active Compressional Orogens,” in Thrust 83 Tectonics, Ed. by K. R. McClay (Chapman and Hall, 23. J. M. Crespi, Y. C. Chan, and M. S. Swaim, “Synoro London, 1992), pp. 1–18. genic Extension and Exhumation of the Taiwan Hinter 9. C. Beaumont, P. Fullsack, and J. Hamilton, “Styles of land,” Geology 24, 247–250 (1996). Crustal Deformation in Compressional Orogens 24. L. Cruz, C. Teyssier, L. Perg, A. Take, and A. Fayon, Caused by Subduction of the Underlying Lithosphere,” “Deformation, Exhumation, and Topography of Tectonophysics 232, 119–132 (1994). Experimental Doubly Vergent Orogenic Wedges Sub 10. C. Beaumont, J. A. Munoz, J. Hamilton, and P. Full jected to Asymmetric Erosion,” J. Structural Geol. 30, sack, “Factors Controlling the Alpine Evolution of the 98–115 (2008). Central Pyrenees Inferred from a Comparison of 25. F. A. Dahlen, “Non Cohesive Critical Coulomb Observations and Geodynamical Models,” J. Geophys. Wedges: An Exact Solution,” J. Geophys. Res. 89 Res. 105, 8121–8145 (2000). (B12), 10125–10133 (1984).
GEOTECTONICS Vol. 44 No. 6 2010 556 MALAVIEILLE, KONSTANTINOVSKAYA
26. F. A. Dahlen, “Mechanical Energy Budget of a Fold 42. M. Gutscher, N. Kukowski, J. Malavieille, and and Thrust Belt,” Nature 331, 335–337 (1988). S. Lallemand, “Cyclical Behavior of Thrust Wedges: 27. F. A. Dahlen, “Critical Taper Model of Fold and Insights from High Basal Friction Sandbox Experi Thrust Belts and Accretionary Wedges,” Ann. Rev. ments,” Geology 24, 135–138 (1996). Earth Planetary Sci. 18, 55–99 (1990). 43. M. A. Gutscher, N. Kukowski, J. Malavieille, and 28. F. A. Dahlen and T. D. Barr, “Brittle Frictional Moun S. Lallemand, “Episodic Imbricate Thrusting and tain Building, 1: Deformation and Mechanical Energy Underthrusting: Analog Experiments and Mechanical Budget,” J. Geophys. Res. 94, 3906–3922 (1989). Analysis Applied to the Alaskan Accretionary Wedge,” 29. F. A. Dahlen and J. Suppe, “Mechanics, Growth, and J. Geophys. Res. 103, 10161–10176 (1998). Erosion of Mountain Belts,” Geol. Soc. Am., Special 44. G. E. Hilley and M. R. Strecker, “Steady State Erosion Paper 218, 161–178 (1988). of Critical Coulomb Wedges with Applications to Tai 30. F. A. Dahlen, J. Suppe, and D. Davis, “Mechanics of wan and the Himalaya,” J. Geophys. Res. 109, B01411 Fold and Thrust Belts and Accretionary Wedges: (2004), doi: 10.1029/2002JB002284. Cohesive Coulomb Theory,” J. Geophys. Res. 89 45. B. K. Horton, “Erosional Control on the Geometry (B12), 10087–10101 (1984). and Kinematics of Thrust Belt Development in the 31. D. Davis, J. Suppe, and F. A. Dahlen, “Mechanics of Central Andes,” Tectonics 18, 1292–1304 (1999). Fold and Thrust Belts and Accretionary Wedges,” 46. S. Hoth, J. Adam, N. Kukowski, and O. Oncken, J. Geophys. Res. 88 (B12), 1153–1172 (1983). “Influence of Erosion on the Kinematics of Bivergent 32. P. Davy and P. R. Cobbold, “Experiments on Shorten Orogens, Results from Scaled Sandbox Simulations,” ing of a 4 Layer Model of the Continental Lithos Geol. Soc. Am. Sp. Pap. 398, 201–225(2004). phere,” Tectonophysics 188, 1–25 (1991). 47. R. A. Jamieson and C. Beaumont, “Deformation and 33. J. Dewey and J. Bird, “Mountain Belts and the New Metamorphism in Convergent Orogens: a Model for Global Tectonics,” J. Geophys. Res. 75, 2625–2647 Uplift and Exhumation of Metamorphic Terranes,” (1970). Geol. Soc. Spec. Publ. 43, 17–129 (1989). 34. H. Echtler and J. Malavieille, “Extensional Tectonics, 48. M. Jolivet and J. Malavieille, Role de l’héritage sédi Basement Uplift and Stephano Permian Collapse Basin mentaire sur la cinématique des systémes chev in a Late Variscan Metamorphic Core Complex (Mon auchants: Modélisation analogique et application a tagne Noire, Southern Massif Central),” Tectonophys l’avant pays Andin, Scientific report, EP/T/EXP/GDP, ics 177, 125–138 (1990). No. 97 30rs, ELF Aquitaine Exploration Production, 35. S. Ellis and C. Beaumont, “Models of Convergent France, 1997, p. 85. Boundary Tectonics: Implications for the Interpreta 49. R. R. Jonesa, R. E. Holdsworth, J. Kenneth, tion of Lithoprobe Data,” Can. J. Earth Sci. 36, 1711– W. McCaffrey, P. Clegg, and E. Tavarnelli, “Scale 1745 (1999). Dependence, Strain Compatibility and Heterogeneity 36. P. C. England and P. Molnar, “Surface Uplift, Uplift of of Three Dimensional Deformation During Mountain Rocks and Exhumation of Rock,” Geology 18 (12), Building: a Discussion,” J. Struct. Geol. 27, 1190– 1173–1177 (1990). 1204 (2005). 37. A. Escher, J. Hunziker, M. Marthaler, H. Masson, 50. E. Konstantinovskaya and J. Malavieille, “Erosion and M. Sartori, and A. Steck, “Geologic Framework and Exhumation in Accretionary Orogens: Experimental Structural Evolution of the Western Swisss Italian and Geological Approaches,” Geochemistry, Geo Alps,” in Deep Structure of the Swiss Alps—Results of the physics Geosystems 6, Q02006 (2005), doi: National Research Program 20 (NRP 20), Ed. by 10.1029/2004GC000794. O. A. Pfiffher, P. Lehner, P. Heitzmann, S. Mueller, and A. Steck (Birkhauser, Basel, 1997), pp. 205–222. 51. E. A. Konstantinovskaya and J. Malavieille, “Accre tionary Orogens: Erosion and Exhumation,” Geotec 38. M. Faure and N. Cottereau, “Kinematic Data on the tonics 39 (1), 69–86 (2005). Emplacement of the Middle Carboniferous Migmatitic Dome in the Axial Zone of the Montagne Noire, Massif 52. J. Kuhlemann, W. Frisch, B. Székely, and I. Dunkl, Central, France,” Comptes Rendus, Academie des “Post Collisional Sediment Budget History of the Alps: Sciences, Ser. II 307 (16), 1787–1794 (1988). Tectonic Versus Climatic Control,” Int. J. Earth Sci. 91, 818–837 (2002). 39. D. A. Foster and B. E. John, “Quantifying Tectonic Exhumation in an Extensional Orogen with Thermo 53. A. Kühni and O. A. Pfiffner, “Drainage Patterns and chronology: Examples from the Southern Basin and Tectonic Forcing: A Model Study for the Swiss Alps,” Range Province,” Geol. Soc. London Sp. Publ. 154, Basin Res. 13, 169–197 (2001). 343–364 (1999). 54. N. Kukowski, S. Lallemand, J. Malavieille, M. A. Guts 40. M. A. Goncharov, “Applicability of Similarity Condi cher, and T. J. Reston, “Mechanical Decoupling and tions to Analoque Modeling of Tectonic Structures,” Basal Duplex Formation Observed in Sandbox Experi Geodynamics Tectonophys. 1 (2), 148–168 (2010). ments with Application to the Mediterranean Ridge 41. F. Graveleau, Interactions Tectonique, Erosion, Sédi Accretionary Complex,” Marine Geol. 186, 29–42 mentation Dans les Avant pays de Chanes: Modélisa (2002). tion Analogique et Étude des Piémonts de l’est du Tian 55. Y. Lagabrielle and A. Chauvet, “The Role of Exten Shan (Asie centrale), Thesis, UniversitéMontpellier II, sional Tectonics in Shaping Cenozoic New Cale Sciences et Techniques du Languedoc, 2008, p. 487. donia,” Bull. Soc. Geol. France 179, 315–329 (2008).
GEOTECTONICS Vol. 44 No. 6 2010 IMPACT OF SURFACE PROCESSES ON THE GROWTH OF OROGENIC WEDGES 557
56. S. Lallemand and J. Malavieille, “Coulomb Theory 70. A. Michard, B. Goffé, O. Saddiqi, R. Oberhansli, and Applied to Accretionary and Non Accretionary A. S. Wendt, “Late Cretaceous Exhumation of the Wedges,” Eos, Trans., AGU 73 (14), 7–23 (1992). Oman Blueschists and Eclogites: a Two Stage Exten 57. S. E. Lallemand, P. Schnurle, and J. Malavieille, “Cou sional Mechanism,” Terra Nova 6, 404–413 (1994). lomb Theory Applied to Accretionary and Non Accre 71. G. Molli, R. Tribuzio, and D. Marquer, “Deformation tionary Wedges—Possible Causes for Tectonic Erosion and Metamorphism at the Eastern Border of the Tenda and/or Frontal Accretion,” J. Geophys. Res. 99 (B6), Massif (NE Corsica): a Record of Subduction and 12033–12055 (1994). Exhumation of Continental Crust,” J. Struct. Geol. 29, 58. C. Larroque, S. Calassou, J. Malavieille, and F. Chanier, 1748–1766 (2006). “Experimental Modeling of Forearc Basin Develop 72. Yu. A. Morozov, An Inverse Kinematic Effect of ment During Accretionary Wedge Growth,” Basin Res. Thrusting and Its Structural and Tectonic Implica 7, 255–268 (1995). tions," Trans. (Dokl.) Rus. Acad. Sci. 384 (4), 382–385 59. P. Leturmy, J. L. Mugnier, P. Vinour, P. Baby, B. Col (2002). letta, and E. Chabron, “Piggyback Basin Development 73. J. Mosar, “Present Day and Future Tectonic Under Above a Thin Skinned Thrust Belt with Two Detach plating in the Western Swiss Alps: Reconciliation of ment Levels as a Function of Interactions between Tec Basement Wrench Faulting and décollement Folding tonic and Superficial Mass Transfer: the Case of the of the Jura and Molasse Basin in the Alpine Foreland,” Subandean Zone (Bolivia),” Tectonophysics 320, 45– Earth Planet. Sci. Lett. 173, 143–145 (1999). 67 (2000). 74. M. Naylor, H. D. Sinclair, S. Willett, and P. A. Cowie, 60. L. I. Lobkovsky, Geodynamics of Spreading and Subduc “A Discrete Element Model for Orogenesis and Accre tion Zones and Two Level Plate Tectonics (Nauka, Mos tionary Wedge Growth,” J. Geophys. Res. 110, B12403 cow, 1988), p. 253 [in Russian]. (2005), doi: 10.1029/2003JB002940. 61. J. Lohrmann, N. Kukowski, J. Adam, and O. Oncken, 75. A. Pérez Estaün, J. R. Martinez Catalan, and F. Bas “The Impact of Analogue Material Properties on the tida, “Crustal Thickening and Deformation Sequence Geometry, Kinematics, and Dynamics of Convergent in the Footwall to the Suture of the Variscan Belt of Sand Wedges,” J. Struct. Geol. 25 (10), 1691–1711 Northwest Spain,” Tectonophysics 191, 243–253 (2003). (1991). 62. J. Malavieille, “Modélisation Expérimental des Chev 76. K. S. Persson and D. Sokoutis, “Analogue Models of auchements Imbriqués: Application aux Chanes de Orogenic Wedges Controlled by Erosion,” Tectono Montagnes,” Bull. Soc. Geol. France 26, 129–138 physics 356, 323–336 (2002). (1984). 77. O. A. Pfiffner, S. Ellis, and C. Beaumont, “Collision 63. J. Malavieille, “Impact of Erosion, Sedimentation and Tectonics in the Swiss Alps: Insight from Geodynamic Structural Heritage on the Structure and Kinematics of Modeling,” Tectonics 19 (6), 1065–1094 (2000). Orogenic Wedges: Analog Models and Case Studies,” 78. J. P. Platt, “Dynamics of Orogenic Wedges and the Geol. Soc. Am. 20 (1), 4–10 (2010), doi: Uplift of High Pressure Metamorphic Rocks,” Geol. 10.1130/GSATG48A.1. Soc. Am. Bull. 97, 1037–1053 (1986). 64. J. Malavieille, and A. Chemenda, “Impact of Initial 79. D. M. Robinson and O. N. Pearson, “Thrust in Nepal: Geodynamic Settings on the Structure, Ophiolite Implications for Channel Flow Exhumation of Greater Emplacement and Tectonic Evolution of Collisional Himalayan Rock Along the Main Central,” Geol. Soc. Belts,” Ofioliti 22 (1), 3–13 (1997). Spec. Publ. 268, 255–267 (2006). 65. J. Malavieille, S. Calassou, and C. Larroque, “Modeli 80. F. Schlunegger and M. Hinderer, “Crustal Uplift in the sation Experimentale des Relations Tectonique Sedi Alps: Why the Drainage Pattern Matters,” Terra Nova mentation Entre Bassin Avant arc et Prisme D’Accre 13, 425–432 (2001). tion,” C. R., Acad., Sci. Paris 316, 1131–1137 (1993). 81. C. Selzer, S. J. H. Buiter, and O. A. Pfiffner, “Numeri 66. J. Malavieille, S. E. Lallemand, S. Dominguez, A. Des cal Modeling of Frontal and Basal Accretion at Colli champs, C. Y. Lu, C. S. Liu, P. Schnürle, and the ACT sional Margins,” Tectonics 27, TC3001 (2008), doi: Scientific Crew, Arc Continent Collision in Taiwan: 10.1029/2007TC002169. New Marine Observations and Tectonic Evolution," 82. J. B. H. Shyu, K. Sieh, Y. G. Chen, and L.H. Chung, Geol. Soc. Am. Spec. Pap. 358, 187–211 (2002). “Geomorphic Analysis of the Central Range Fault, the 67. J. G. Masek and C. C. Duncan, “Minimum Work Second Major Active Structure of the Longitudinal Val Mountain Building,” J. Geophys. Res. 103 (B1), 907– ley Suture, Eastern Taiwan,” Geol. Soc. Am. Bull. 118 917 (1998). (11/12), 1447–1462 (2006), doi: 10.1130/B25905.1. 68. M. Mattauer, “Intracrustal Subduction, Crust Mantle 83. M. Simoés and J. P. Avouac, “Investigating the Kine décollement and Crustal Stacking Wedge in the Hima matics of Mountain Building in Taiwan from the Spa layas and Other Collision Belts,” Geol. Soc. London, tiotemporal Evolution of the Foreland Basin and West Collision Tectonics 19, 37–50 (1986). ern Foothills,” J. Geophys. Res. 111 (B10) (2006), doi: 69. P. Matte, “Variscan Thrust Nappes, Detachments, and 10.1029/2005JB004209. Strike Slip Faults in the French Massif Central: Inter 84. M. Simoés, J. P. Avouac, O. Beyssac, B. Goffe, K. Far pretation of the Lineations,” in Memoir 200: 4 D ley, and Y. G. Chen, “Mountain Building in Taiwan: A Framework of Continental Crust., 2007, Vol. 200, Thermokinematic Model,” J. Geophys. Res. 112, pp. 391–402. B11405 (2007), doi: 10.1029/20066JB004824.
GEOTECTONICS Vol. 44 No. 6 2010 558 MALAVIEILLE, KONSTANTINOVSKAYA
85. G. D. H. Simpson, “How and to what Extent does the Drainage Basins,” J. Geophys. Res. 99 (B7), 13871– Emergence of Orogens above Sea Level Influence Their 13884 (1994). Tectonic Development?,” Terra Nova 18, 447–451 92. J. Suppe, “Mechanics of Mountain Building and Meta (2006a), doi: 10.1111/j.1365 3121.2006.00711. morphism in Taiwan,” Memoir Geol. Soc. China 4, 86. G. D. H. Simpson, “Influence of Erosion and Deposi 67–89 (1981). tion on Deformation in Fold Belts,” Geol. Soc. Am. 93. G. Toussaint, E. Burov, and J. P. Avouac, “Tectonic Spec. Pap. 398, 267–281 (2006b). Evolution of a Continental Collision Zone: A Thermo 87. A. Sommaruga, “décollement Tectonics in the Jura mechanical Numerical Model,” Tectonics 23, TC6003 Foreland Fold and Thrust Belt,” Mar. Petrol. Geol. 16 (2004), doi: 10.1029/2003TC001604. (2), 111–134 (1999). 94. J. Van den Driessche and J. P. Brun, “Tectonic Evolu 88. J. C. Soula, P. Debat, S. Brusset, G. Bessiére, F. Chris tion of the Montagne Noire (French Massif Central): a tophoul, and J. Déramond, “Thrust Related, Diapiric, Model of Extensional Gneiss Dome,” Geodinamica and Extensional Doming in a Frontal Orogenic Wedge: Acta 5, 85–99 (1992). Example of the Montagne Noire, Southern French 95. S. D. Willett, “Orogeny and Orography: The Effects of Hercynian Belt,” J. Struct. Geol. 23 (11), 1677–1699 Erosion on the Structure of Mountain Belts,” J. Geo (2001). phys. Res. 104 (B12), 28957–28982 (1999). 89. G. S. Stockmal, “Modeling of Large Scale Accretion 96. S. D. Willett and M. T. Brandon, “On Steady States in ary Wedge Deformation,” J. Geophys. Res. 88, 8271– Mountain Belts,” Geology 30, 175–178 (2002). 8287 (1983). 97. S. D. Willett, C. Beaumont, and P. Fullsack, “Mechan 90. G. S. Stockmal, C. Beaumont, M. Nguyen, and B. Lee, ical Model for the Tectonics of Doubly Vergent Com “Mechanics of Thin Skinned Fold and Thrust Belts: pressional Orogens,” Geology 21 (4), 371–374 (1993). Insights from Numerical Models,” Geol. Soc. Am. 98. W. Zhao, K. D. Nelson, and project INDEPTH team, Spec. Pap. 433, 63–98 (2007). “Deep Seismic Reflection Evidence for Continental 91. M. A. Summerfield and N. J. Hulton, “Natural Con Underthrusting Beneath Southern Tibet,” Nature 366, trols of Fluvial Denudation Rates in Major World 557–559 (1993).
GEOTECTONICS Vol. 44 No. 6 2010