Structural evolution of the external zones derived from the Flysch trough and the South Iberian and Maghrebian paleomargins around the Gibraltar arc: a comparative study

2006 ◽  
Vol 177 (5) ◽  
pp. 267-282 ◽  
Author(s):  
Ana Crespo-Blanc ◽  
Dominique Frizon de Lamotte
Keyword(s):  
Large Scale ◽  
Structural Evolution ◽  
Accretionary Prism ◽  
Point Of View ◽  
Low Grade ◽  
The South ◽  
Sedimentary Sequences ◽  
Structural Style ◽  
Thrust Belts ◽  
Orogenic Wedge

Abstract The Betics and Rif cordillera constitute the northern and southern segments of the Gibraltar arc. Two different fold-and-thrust belts, deriving from the South Iberian and Maghrebian paleomargins respectively, developed in front of this orogenic system. By contrast, the Flysch Trough units and the overlying Alboran crustal domain (internal zones), which are situated in the uppermost part of the orogenic wedge, are common to both branches of the arc. The Flyschs Trough units constitute an inactive accretionary prism, derived from a deep elongated trough. From three large-scale profiles and some lithostratigraphic features of the involved sedimentary sequences, the Betic and Rif external domains are compared, mainly from a structural point of view. Although they are generally considered to show major similarities, the Betic and Rif external domains are in fact strikingly different, mainly concerning the structural style, deformation timing and metamorphism: a) the thick-skinned structure in the External Rif domain vs thin-skinned in the Subbetic domain; b) the pre-Oligocene and Miocene stacking in the External Rif domain vs the exclusively Miocene one in the Subbetic domain, and c) the metamorphism present only in part of the External Rif domain (low-grade greenschists facies). By contrast, it was not possible to establish any difference in structural style and deformation timing between the Flysch units outcropping in both branches of the Gibraltar arc.

Late Carboniferous Schlingen in the Gotthard nappe (Central Alps) and their relation to the Variscan evolution

2021 ◽  
Author(s):  
Mario Buehler ◽  
Roger Zurbriggen ◽  
Alfons Berger ◽  
Marco Herwegh ◽  
Daniela Rubatto
Keyword(s):  
Shear Zone ◽  
Country Rock ◽  
Structural Evolution ◽  
Point Of View ◽  
Swiss Alps ◽  
Low Grade ◽  
Central Alps ◽  
Structural Investigations ◽  
Alpine Belt ◽  
Main Cluster

<p>Many pre‐Mesozoic basements of the Alpine belt contain kilometre‐scaled folds with steeply inclined axial planes and fold axes. Those structures are referred to as Schlingen folds. They deform polymetamorphic gneisses, often Late‐Ordovician metagranitoids and are cross‐cut themselves by Permian intrusions. However, the structural evolution of such Schlingen is still not completely understood and their geodynamic significance for the Variscan evolution is not clear. To close this gap, this study investigates in detail a well-preserved Schlingen structure in the Gotthard nappe (Central Swiss Alps). This Schlingen fold evolved by a combination of shearing and folding under amphibolite facies conditions. Detailed digital field mapping coupled with petrological and structural investigations reveal local synkinematic migmatisation in the fold hinges parallel to axial planes. U‐Pb dating of zircons separated from associated leucosomes reveal cores that record a detrital country rock age of 450 ± 3 Ma, and rims with a range of dates from 270 to 330 Ma. The main cluster defines an age of 316 ± 4 Ma. We ascribe this Late‐Carboniferous age to peak metamorphic conditions of the late‐Variscan Schlingen phase.</p><p>The pre-Schlingen structures are subdivided into three older deformation events, which are connected to the Cenerian and post-Cenerian deformations. In addition, until now unknown, post Schlingen-, but pre-Alpine transpressional deformation have been detected and described. This superimposed deformation produced locally a low-grade foliation and minor undulation of the Schlingen structures.</p><p>The detail data of the investigated fold structures are linked with already described Schlingen folds in the wider Alpine realm, which all are concentrated in the most southern parts of the Variscides. From a geodynamic point of view and based on the new tectono-metamorphic constraints, we propose Schlingen formation preceded and concurred the crustal-scale transpressional tectonics of the East Variscan Shear Zone. This scenario separates, at least in a structural sense, the Southern Variscides from more northern parts (also Gondwana derived) inside Pangea, where Schlingen folds are absent.</p>

Structural style of the White Pointer and Hammerhead Delta—deepwater fold-thrust belts, Bight Basin, Australia

2010 ◽  
Vol 50 (1) ◽  
pp. 487 ◽  
Author(s):  
Justin MacDonald ◽  
Rosalind King ◽  
Richard Hillis ◽  
Guillaume Backé
Keyword(s):  
Supercritical Co2 ◽  
Large Scale ◽  
Qualitative Evaluation ◽  
Seal Failure ◽  
Structural Style ◽  
Thrust Belts ◽  
Strong Positive Relationship ◽  
Basin Scale ◽  
Gas Chimneys ◽  
Gippsland Basin

GeoScience Victoria and partners have undertaken the first detailed basin-wide study of the regional top seal in the Gippsland Basin. The Gippsland Basin is an attractive site for geological carbon storage (GCS) because of the close proximity to emission sources and the potential for large-scale storage projects. This top seal assessment involved the analysis of seal attributes (geometry, capacity and mineralogy) and empirical evidence for seal failure (soil gas geochemical anomalies, gas chimneys, hydrocarbon seepage and oil slicks). These datasets have been integrated to produce a qualitative evaluation of the containment potential for GCS, and also hydrocarbons, across the basin. Mineralogical analysis of the top seal has revealed that the Lakes Entrance Formation is principally a smectite-rich claystone. The geometry of the top seal is consistent with deposition in an early post-rift setting where marine sediments filled palaeo-topographic lows. The seal thickness and depth to seal base are greatest in the Central Deep and decrease toward the margins. There is a strong positive relationship between seal capacity column heights, seal thickness, depth to seal base and smectite content. At greater burial depths (below 700 m) and where smectite content is greater than 70%, seal capacity is increased (supportable column heights above 150 m). Natural hydrocarbon leakage and seepage onshore and offshore is correlated with fault distribution and areas of poor seal capacity. This study provides a framework for qualitatively evaluating seal potential at a basin scale. It has shown that the potential of the regional top seal over the Central Deep, Southern Terrace, central eastern Lake Wellington Depression and the southern to central near shore areas in the Seaspray Depression are most suitable for the containment of supercritical CO2. Further toward the margin of the regional seal in both onshore and offshore areas, containment of supercritical CO2 is less likely.

scholarly journals The western termination of the South Pyrenean Triangle Zone; a structural and geophysical characterization.

2021 ◽  
Author(s):  
Pablo Santolaria ◽  
Concepción Ayala ◽  
Emilio L. Pueyo ◽  
Félix M. Rubio ◽  
Ruth Soto ◽  
...  
Keyword(s):  
Upper Eocene ◽  
The South ◽  
The North ◽  
Triangle Zone ◽  
Structural Style ◽  
Lower Oligocene ◽  
Thrust Belts ◽  
Stratigraphic Model ◽  
Structural Architecture ◽  
Surface Geology

<p>The presence of multiple evaporite levels strongly influence the structural style and kinematics of fold-and-thrust belts. Particularly (but not exclusively) in their fronts, it is common for these décollements to favor the formation of triangle zones. In the central portion of the Pyrenees, the South Pyrenean Triangle Zone represents the frontal part of this chain, that involves the Oligocene-Miocene Ebro Basin foreland deposits. We have focused on its western termination, characterized by a salt-cored anticline that laterally passes to a backthrust which dies out to the west. These structures are detached on the Upper Eocene-Lower Oligocene syntectonic evaporite Barbastro Formation (and lateral equivalents) that acted as a multidetachment unit. To the north, the south-directed Pyrenean thrust unit detached on Middle-Upper Triassic evaporites to finally glide along the Upper Eocene-Lower Oligocene décollement horizons.</p><p>In this contribution, we present a detailed structural and stratigraphic model of this triangle zone termination, constructed accordingly to two major approaches (1) constraining the geometry and structural architecture based on surface geology, interpretation of seismic lines (>900 km) and wells and, (2) obtaining the 3D density distribution of the detachment level (Barbastro Fm. and lateral equivalents as well as deeper, Triassic evaporites) using gravity stochastic inversion by means of more than 7000 gravity stations and 1500 actual density data from surface rocks. All in all, this multidisciplinary approach allows us to characterize the western termination of the South Pyrenean Triangle zone as the transition from a ramp-dominated and multiple triangle zone to a detachment-dominated one whose geometry, kinematics, and location were controlled by the distribution and heterogeneity of the Upper Eocene-Lower Oligocene syntectonic décollements and the southern pinch-out of the basal detachment of this unit.</p>

scholarly journals Structural evolution of the Ikerasak area, Umanak district, central West Greenland

1981 ◽  
Vol 105 ◽  
pp. 33-35
Author(s):  
J Grocott
Keyword(s):  
Structural Evolution ◽  
The South ◽  
West Greenland ◽  
Structural Style

The 1980 season was the last of the three seasons allocated for the mapping of the 1:100000 sheet 70 V. 2 Nord-Agpat (for background and references see Pulvertaft, 1979). The most important area that remained to be mapped in 1980 consisted of the islands Ikerasak and Talerua, which were known from the 1965 reconnaissance by T. C. R. Pulvertaft to have a structural style somewhat different from that of the northern part of the sheet area where low dips are prevalent. The author was invited to join the team of geologists from Copenhagen University responsibie for the Agpat sheet to map these islands and the mainland peninsula of Akuliaruserssuaq to the south-east (fig. 11).

scholarly journals Deciphering the metamorphic evolution of the Pulo do Lobo metasedimentary domain (SW Iberian Variscides)

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 469-488 ◽  
Author(s):  
Irene Pérez-Cáceres ◽  
David Jesús Martínez Poyatos ◽  
Olivier Vidal ◽  
Olivier Beyssac ◽  
Fernando Nieto ◽  
...  
Keyword(s):  
B Cell ◽  
Microstructural Analysis ◽  
Carbonaceous Material ◽  
Accretionary Prism ◽  
Low Pressure ◽  
White Mica ◽  
Cell Dimension ◽  
Low Grade ◽  
The South ◽  
Metamorphic Evolution

Abstract. The Pulo do Lobo domain is one of the units exposed within the orogenic suture zone between the Ossa-Morena and the South Portuguese zones in the SW Iberian Variscides. This metasedimentary unit has been classically interpreted as a Rheic subduction-related accretionary prism formed during pre-Carboniferous convergence and eventual collision between the South Portuguese Zone (part of Avalonia) and the Ossa-Morena Zone (peri-Gondwanan terrane). Discrete mafic intrusions also occur within the dominant Pulo do Lobo metapelites, related to an intra-orogenic Mississippian transtensional and magmatic event that had a significant thermal input. Three different approaches have been applied to the Devonian–Carboniferous phyllites and slates of the Pulo do Lobo domain in order to study their poorly known low-grade metamorphic evolution. X-ray diffraction (XRD) was used to identify the mineralogy and measure crystallographic parameters (illite “crystallinity” and K-white mica b-cell dimension). Compositional maps of selected samples were obtained from electron probe microanalysis, which allowed for processing with XMapTools software, and chlorite semiempirical and thermodynamic geothermometry was performed. Thermometry based on Raman spectroscopy of carbonaceous material (RSCM) was used to obtain peak temperatures. The microstructural study shows the existence of two phyllosilicate growth events in the chlorite zone, the main one (M1) related to the development of a Devonian foliation S1 and a minor one (M2) associated with a crenulation cleavage (S2) developed in middle–upper Carboniferous times. M1 entered well into epizone (greenschist facies) conditions. M2 conditions were at lower temperature, reaching the anchizone–epizone boundary. These data accord well with the angular unconformity that separates the Devonian and Carboniferous formations of the Pulo do Lobo domain. The varied results obtained by the different approaches followed, combined with microstructural analysis, provide different snapshots of the metamorphic history. Thus, RSCM temperatures are higher in comparison with the other methods applied, which is interpreted to reflect a faster re-equilibration during the short-lived thermal Mississippian event. Regarding the metamorphic pressure, the data are very homogeneous: very low celadonite content (0 %–10 %) in muscovite (and low values of K-white mica b-cell dimension; 8.995 Å mean value), indicating a low pressure–temperature gradient, which is unexpected in a subduction-related accretionary prism. Highlights A multidisciplinary approach has been applied to study the metamorphism of the Pulo do Lobo metapelites. Devonian metamorphism entered epizone conditions. Carboniferous metamorphism reached the anchizone–epizone boundary. The inferred low-pressure gradient is incompatible with a subduction-related accretionary prism.

Rift evolution and structural style in the Orphan Basin: results from regional structural restorations and crustal area balancing 

2021 ◽  
Author(s):  
Adam J. Cawood ◽  
David A. Ferrill ◽  
Alan P. Morris ◽  
David Norris ◽  
David McCallum ◽  
...  
Keyword(s):  
Cross Sections ◽  
Seismic Data ◽  
Large Scale ◽  
Structural Evolution ◽  
Strike Slip ◽  
Detachment Faults ◽  
The North ◽  
Structural Style ◽  
Complex Structural ◽  
Structural Configurations

<p>The Orphan Basin on the eastern edge of the Newfoundland continental margin formed as a Mesozoic rift basin prior to continental breakup associated with the opening of the North Atlantic. Few exploration wells exist in the basin, and until recently regional interpretations have been based on sparse seismic data coverage - because of this the structural evolution of the Orphan Basin has historically not been well understood. Key uncertainties include the timing and amount of rift-related extension, dominant extension directions, and the structural styles that accommodated progressive rift development in the basin.     </p><p>Interpretation of newly acquired modern broadband seismic data and structural restoration of three regional, WNW-ESE oriented cross-sections across the Orphan Basin and Flemish Cap provide new insights into rift evolution and structural style in the area. Our results show that major extension in the basin occurred between 167 Ma and 135 Ma, with most extension occurring prior to 151 Ma. We show that extension after 135 Ma largely occurred east of Flemish Cap due to a shift in the locus of rifting from the Orphan Basin to east of Flemish Cap. We find no evidence for discrete rifting events in the Orphan Basin, as has been suggested by other authors.  Kinematic restoration and associated heave measurements for the Orphan Basin show that extension was both widespread and relatively evenly distributed across the basin from Middle-Late Jurassic to Early Cretaceous.</p><p>We provide evidence for more widespread deposition of Jurassic strata throughout the Orphan Basin than previously interpreted, and show that Jurassic deposition was controlled by the occurrence and displacement of crustal-scale extensional detachment faults.  Structure in the three regional cross sections is dominated by large-scale, shallowly dipping extensional detachment faults. These faults mainly dip to the northwest and control the geometry and position of extensional basins – grabens and half-grabens – which occur at a range of scales. Stacked detachment surfaces, hyperextension, and attenuation of the crust are observed in central and eastern parts of the Orphan Basin. Zones of extreme crustal attenuation (to ca. 3.7 km) are interpreted to be coincident with large-displacement (up to 60 km) low-angle detachments. Results from crustal area balancing suggest that up to 41% of extension is not recognized through structural seismic interpretation, which we attribute to subseismic-scale ductile and brittle deformation, and uncertainties in the identification of detachment surfaces or complex structural configurations (e.g., overprinting of early extensional deformation).</p><p>Rifting style in the central, northern, and eastern parts of the Orphan Basin is dominated by low-angle detachment faulting with maximum extension perpendicular to the incipient rift axis. In contrast, structural geometries in the southwestern part of the basin are suggestive of transtensional deformation, and interplay of normal and strike-slip faulting.  Results from map-based interpretation show that strike-slip faults within this transtensional zone are associated with displacement transfer between half-grabens of opposing polarity, rather than regional strike-slip displacement.  These structures are interpreted as contemporaneous and kinematically linked to displacement along low-angle detachment surfaces elsewhere, and are not attributed to distinct episodes of oblique extension.       </p>

A discussion on the validation of structural interpretations based on the mechanics of sedimentary basins in the northwestern Mediterranean fold-and-thrust belts

2016 ◽  
Vol 187 (2) ◽  
pp. 83-104 ◽  
Author(s):  
Josselin Berthelon ◽  
William Sassi
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Numerical Models ◽  
Structural Evolution ◽  
Sedimentary Basins ◽  
Structural Style ◽  
Thrust Belts ◽  
Fold And Thrust Belts ◽  
Thin Skin ◽  
Northwestern Mediterranean

Abstract Using the geologist’s interpretation of 6 published balanced cross-sections in the fold and thrust belts of the northwestern Mediterranean, a comparative analysis of the interpreted subsurface structural architecture is used to address the links between the structural style and the mechanics of fold and thrust emplacement. For each cross-section example, the geo-dataset and the methods used by the interpreters are different in quantity and quality. Here we have examined how useful is the content of information of each cross-section to constrain the structural evolution scenario. Each interpretation is examined according to considerations of the mechanics of sedimentary basin deformation and how uncertain is the extrapolation of fault trajectory at depth. It is shown that each case reveals a particular type of structural style: thin-skin or thick skin tectonics, fault-related folding, pre-existing fault pattern. The present structural analysis is used to determine for each cross-section the nature of the mechanical problem to address that will reduce uncertainty on the geologic scenario reconstruction. The proposed mechanical boundary conditions could serve to develop analog or numerical models that aim at testing the mechanical validity of the structural scenario of fold and thrust emplacement.

The role of inherited structures and basin geometry during the 3D inversion of a passive continental margin: the case of the Doldenhorn-Aar Massif system (Central Swiss Alps)

2021 ◽  
Author(s):  
Ferdinando Musso Piantelli ◽  
David Mair ◽  
Marco Herwegh ◽  
Alfons Berger ◽  
Eva Kurmann ◽  
...  
Keyword(s):  
Continental Margin ◽  
Large Scale ◽  
Passive Continental Margin ◽  
Swiss Alps ◽  
Cylindrical Shape ◽  
Structural Position ◽  
Structural Style ◽  
Thrust Belts ◽  
Fold And Thrust Belts ◽  
Aar Massif

<p>Inversion of passive margins and their transportation into fold-and-thrust belts is a critical stage of mountain building processes and their structural interpretation is fundamental for understanding collisional orogens. Due to the multitude of parameters that influence their formation (e.g. the interaction between sedimentary cover and basement, the mechanical stratigraphy or the rheology of different rock types) as well as along-strike internal variations, a single cross-sectional view is insufficient in exploring the 3D evolution of a fold-and-thrust belt. Hence, a 3D geological characterization is required to better comprehend such complex systems. Based on a detailed digital map, a 3D structural model of the current tectonic situation and sequential retrodeformation, we elaborate the 3D evolution of a part of the former European passive continental margin. In this setting, we focus on the Doldenhorn Nappe (DN) and the underlying western Aar massif (external Central Alps, Switzerland). The DN is part of the Helvetic nappe system and consists of a large-scale recumbent fold with a thin inverted limb of intensively deformed sediments (Herwegh and Pfiffner 2005). The sedimentary rocks of the DN were deposited in Mesozoic-Cenozoic times in a small-sized basin, which has been inverted during the compression of the Alpine orogeny (Burkhard 1988). Along NNW-SSE striking geological cross-sections, restoration techniques reveal the original asymmetric triangular shape of the DN basin and how the basin has been exhumed from ~ -12 km (Berger et al. 2020) to its present position at 4km elevation above sea level throughout several Alpine deformation stages. Moreover, the model allows to visualize the current structural position of the DN and the massif as well as the geometric and overprinting relationships of the articulated deformation sequence that shaped the investigated area throughout the Alpine evolution. Here we document that: (i) the DN is a strongly non-cylindrical recumbent fold that progressively pinches out toward the NE; (ii) significant along-strike (W-E) stratigraphy thickness variations are reflected in structural variations from a single basal thrust deformation (W) to an in-sequence thrust deformation (E); and (iii) the progressive exhumation of the basement units towards the E and thrusting towards the N. In this context, special emphasis is given to illustrate how three-dimensional geometry of inherited pre-orogenic structures (e.g., Variscan-Permian and rifting related basement cover structures) play a key role in the structural style of fold-and-thrust belts. In summary, today’s structural position of the DN is the result of the inversion of a small basin in an early stage of thrusting, which was followed by sub-vertical buoyancy driven exhumation of the Aar massif and subsequent thrust related shortening. All three stages are deeply coupled with an original non-cylindrical shape of the former European passive continental margin.</p>

scholarly journals Structural evolution of the Turňa Unit constrained by fold and cleavage analyses and its consequences for the regional tectonic models of the Western Carpathians

2016 ◽  
Vol 67 (2) ◽  
pp. 179-195 ◽  
Author(s):  
Alexander Lačný ◽  
Dušan Plašienka ◽  
Rastislav Vojtko
Keyword(s):  
Large Scale ◽  
Structural Evolution ◽  
Lower Triassic ◽  
Geological Structure ◽  
Western Carpathians ◽  
Low Grade ◽  
Accretionary Wedge ◽  
Deformation Stage ◽  
Bedding Planes ◽  
Regional Tectonic

AbstractThe Turňa Unit (Turnaicum, Tornaicum) is one of the three nappe systems involved in the geological structure of the inner zones of the Western Carpathians. The unit is formed by a system of partial nappes and duplexes, which overlie the Meliata Unit s.l. and are overridden by the Silica Nappe. The Slovenská skala partial nappe in the investigated area includes clastic sediments of the mid-Carboniferous, Permian and Early Triassic age, followed by mostly deep-water Middle-Upper Triassic succession predominantly composed of carbonates. Structural analysis of cleavage planes and folds was carried out predominantly in the Lower Triassic Werfen Formation. The measured deformational structures are polygenetic and were principally formed in three successive deformation stages. The first deformation stage is represented by bedding-parallel, very low-grade metamorphic foliation that was related to nappe stacking and formation of the Mesozoic accretionary wedge during the latest Jurassic and earliest Cretaceous. The second deformation stage is represented by systems of open to closed, partly asymmetric folds with SW-NE oriented, steeply NW- or SE-dipping axial-plane cleavage. Regionally, the folded bedding planes are usually moderately SE-ward dipping, the NW-ward and subvertical dips are less common. The mesoscopic fold structures predominantly occur in the SW-NE trending anticlinal and synclinal hinge zones of large-scale folds. These structures evolved in a compressional tectonic regime with the NW-SE to N-S orientation of the maximum compressional axis. The third observed deformation stage was activated during ENE-WSW oriented shortening. This stage is chiefly represented by open, kink-type folds. Some inferences for regional structures and tectonic evolution of the area are discussed as well.

Gravitational sliding or tectonic thrusting?: Examples and field recognition in the Miura-Boso subduction zone prism

2021 ◽  
Author(s):  
Yujiro Ogawa ◽  
Shin’ichi Mori
Keyword(s):  
Large Scale ◽  
Accretionary Prism ◽  
Small Scale ◽  
Tectonic Deformation ◽  
Detachment Faults ◽  
Thrust Belts ◽  
Fold And Thrust Belt ◽  
Fold Belts ◽  
Geologic Record ◽  
Accretionary Prisms

ABSTRACT Discrimination between gravity slides and tectonic fold-and-thrust belts in the geologic record has long been a challenge, as both have similar layer shortening structures resulting from single bed duplication by thrust faults of outcrop to map scales. Outcrops on uplifted benches within the Miocene to Pliocene Misaki accretionary unit of Miura-Boso accretionary prism, Miura Peninsula, central Japan, preserve good examples of various types of bedding duplication and duplex structures with multiple styles of folds. These provide a foundation for discussion of the processes, mechanisms, and tectonic implications of structure formation in shallow parts of accretionary prisms. Careful observation of 2-D or 3-D and time dimensions of attitudes allows discrimination between formative processes. The structures of gravitational slide origin develop under semi-lithified conditions existing before the sediments are incorporated into the prism at the shallow surfaces of the outward, or on the inward slopes of the trench. They are constrained within the intraformational horizons above bedding-parallel detachment faults and are unconformably covered with the superjacent beds, or are intruded by diapiric, sedimentary sill or dike intrusions associated with liquefaction or fluidization under ductile conditions. The directions of vergence are variable. On the other hand, layer shortening structure formed by tectonic deformation within the accretionary prism are characterized by more constant styles and attitudes, and by strong shear features with cataclastic textures. In these structures, the fault surfaces are oblique to the bedding, and the beds are systematically duplicated (i.e., lacking random styles of slump folds), and they are commonly associated with fault-propagation folds. Gravitational slide bodies may be further deformed at deeper levels in the prism by tectonism. Such deformed rocks with both processes constitute the whole accretionary prism at depth, and later may be deformed, exhumed to shallow levels, and exposed at the surface of the trench slope, where they may experience further deformation. These observations are not only applicable in time and space to large-scale thrust-and-fold belts of accretionary prism orogens, but to small-scale examples. If we know the total 3-D geometry of geologic bodies, including the time and scale of deformational stages, we can discriminate between gravitational slide and tectonic formation of each fold-and-thrust belt at the various scales of occurrence.

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