scholarly journals Unconformity development in retroarc foreland basins: Implications for the geodynamics of Andean-type margins

2021 ◽  
pp. jgs2020-263
Author(s):  
B. Horton
Keyword(s):  
Sediment Accumulation ◽  
Sediment Supply ◽  
Thrust Belt ◽  
Foreland Basins ◽  
Content Type ◽  
Thrust Belts ◽  
Oblique Convergence ◽  
Slab Breakoff ◽  
Fold And Thrust Belts ◽  
Andean Type

Unconformities in foreland basins may be generated by tectonic processes that operate in the basin, adjacent fold-thrust belt, and broader convergent margin. Foreland basin unconformities represent shifts from high accommodation to nondepositional or erosional conditions in which the interruption of subsidence precludes net sediment accumulation. This study explores the genesis of long duration (>1–20 Myr) unconformities and condensed stratigraphic sections by considering modern and ancient examples from the Andes. These cases highlight potential geodynamic mechanisms of accommodation reduction and hiatus development in Andean-type retroarc foreland settings, including: (a) shortening-induced uplift in the frontal thrust belt and proximal foreland; (b) growth and advance of a broad, low-relief flexural forebulge; (c) uplift of intraforeland basement blocks; (d) tectonic quiescence with regional isostatic rebound; (e) cessation of thrust loading and flexural subsidence during oblique convergence; (f) diminished accommodation or sediment supply due to changes in sea level, climate, erosion, or transport; (g) basinwide uplift during flat-slab subduction; and (h) dynamic uplift associated with slab window formation, slab breakoff, elevated intraplate (in-plane) stress, or related mantle process. These contrasting mechanisms can be distinguished on the basis of the spatial distribution, structural context, stratigraphic position, paleoenvironmental conditions, and duration of unconformities and condensed sections.Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

Accommodation of India–Asia convergence via strike-slip faulting and block rotation in the Qilian Shan fold–thrust belt, northern margin of the Tibetan Plateau

2021 ◽  
pp. jgs2020-207
Author(s):  
Feng Cheng ◽  
Andrew V. Zuza ◽  
Peter J. Haproff ◽  
Chen Wu ◽  
Christina Neudorf ◽  
...  
Keyword(s):  
Strike Slip ◽  
Luminescence Dating ◽  
Thrust Belt ◽  
Block Rotation ◽  
Content Type ◽  
Link Type ◽  
Northeastern Tibet ◽  
Thrust Belts ◽  
Fold And Thrust Belts ◽  
Supplementary Material

Existing models of intracontinental deformation have focused on plate-like rigid body motion v. viscous-flow-like distributed deformation. To elucidate how plate convergence is accommodated by intracontinental strike-slip faulting and block rotation within a fold–thrust belt, we examine the Cenozoic structural framework of the central Qilian Shan of northeastern Tibet, where the NW-striking, right-slip Elashan and Riyueshan faults terminate at the WNW-striking, left-slip Haiyuan and Kunlun faults. Field- and satellite-based observations of discrete right-slip fault segments, releasing bends, horsetail termination splays and off-fault normal faulting suggest that the right-slip faults accommodate block rotation and distributed west–east crustal stretching between the Haiyuan and Kunlun faults. Luminescence dating of offset terrace risers along the Riyueshan fault yields a Quaternary slip rate of c. 1.1 mm a−1, which is similar to previous estimates. By integrating our results with regional deformation constraints, we propose that the pattern of Cenozoic deformation in northeastern Tibet is compatible with west–east crustal stretching/lateral displacement, non-rigid off-fault deformation and broad clockwise rotation and bookshelf faulting, which together accommodate NE–SW India–Asia convergence. In this model, the faults represent strain localization that approximates continuum deformation during regional clockwise lithospheric flow against the rigid Eurasian continent.Supplementary material: Luminescence dating procedures and protocols is available at https://doi.org/10.17605/OSF.IO/CR9MNThematic collection: This article is part of the Fold-and-thrust belts and associated basins collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

Late Miocene sediment delivery from the axial drainage system of the East Carpathian foreland basin to the Black Sea

Geology ◽  
2020 ◽  
Vol 48 (8) ◽  
pp. 761-765 ◽  
Author(s):  
Arjan de Leeuw ◽  
Stephen J. Vincent ◽  
Anton Matoshko ◽  
Andrei Matoshko ◽  
Marius Stoica ◽  
...  
Keyword(s):  
Black Sea ◽  
Late Miocene ◽  
Drainage System ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Danube River ◽  
The Black Sea ◽  
Foreland Basins ◽  
Continental Scale ◽  
Slab Breakoff

Abstract We describe a late Miocene to early Pliocene axial drainage system in the East Carpathian foreland, which was an important sediment supplier to the Black Sea and the Dacian Basin. Its existence explains the striking progradation of the northwest Black Sea shelf prior to the onset of sediment supply from the continental-scale Danube River in the late Pliocene to Pleistocene. This axial drainage system evolved due to the diachronous along-strike evolution of the Carpathians and their foreland; continental collision, overfilling, slab breakoff, and subsequent exhumation of the foreland occurred earlier in the West Carpathians than in the East Carpathians. After overfilling of the western foreland, excess sediment was transferred along the basin axis, giving rise to a 300-km-wide by 800-km-long, southeast-prograding river-shelf-slope system with a sediment flux of ∼12 × 103 km3/m.y. Such late-stage axial sediment systems often develop in foreland basins, in particular, where orogenesis is diachronous along strike. Substantial lateral sediment transport thus needs to be taken into account, even though evidence of these axial systems is often eroded following slab breakoff and inversion of their foreland basins.

scholarly journals Control of 3D tectonic inheritance on fold-and-thrust belts: insights from 3D numerical models and application to the Helvetic nappe system

2019 ◽  
Author(s):  
Richard Spitz ◽  
Arthur Bauville ◽  
Jean-Luc Epard ◽  
Boris J. P. Kaus ◽  
Anton A. Popov ◽  
...  
Keyword(s):  
3D Model ◽  
Swiss Alps ◽  
Thrust Belt ◽  
First Order ◽  
Tectonic Inheritance ◽  
Thrust Belts ◽  
Fold And Thrust Belt ◽  
Model Configuration ◽  
Fold And Thrust Belts ◽  
Half Graben

Abstract. Fold-and-thrust belts and associated tectonic nappes are common in orogenic regions. They exhibit a wide variety of geometries and often a considerable along-strike variation. However, the mechanics of fold-and-thrust belt formation and the control of the initial geological configuration on this formation are still incompletely understood. Here, we apply three-dimensional (3D) thermo-mechanical numerical simulations of the shortening of the upper crustal region of a passive margin to investigate the control of 3D laterally variable inherited structures on the fold-and-thrust belt evolution and associated nappe formation. We consider tectonic inheritance by applying an initial model configuration with horst and graben structures having laterally variable geometry and with sedimentary layers having different mechanical strength. We use a visco-plastic rheology with temperature dependent flow laws and a Drucker-Prager yield criterion. The models show the folding, detachment and horizontal displacement of sedimentary units, which resemble structures of fold and thrust nappes. The models further show the stacking of nappes. The detachment of nappe-like structures is controlled by the initial basement and sedimentary layer geometry. Significant horizontal transport is facilitated by weak sedimentary units below these nappes. The initial half-graben geometry has a strong impact on the basement and sediment deformation. Generally, deeper half-grabens generate thicker nappes and stronger deformation of the neighboring horst while shallower half-grabens generate thinner nappes and less deformation in the horst. Horizontally continuous strong sediment layers, which are not restricted to inital graben structures, cause detachment folding and not overthrusting. The amplitude of the detachment folds is controlled by the underlying graben geometry. A mechanically weaker basement favors the formation of fold nappes while stronger basement favors thrust sheets. The applied model configuration is motivated by the application of the 3D model to the Helvetic nappe system of the French-Swiss Alps. Our model is able to reproduce several first-order structural features of this nappe system, namely (i) closure of a half-graben and associated formation of the Morcles and Doldenhorn nappes, (ii) the overthrusting of a nappe resembling the Wildhorn and Glarus nappes and (iii) the formation of a nappe pile resembling the Helvetic nappes resting above the Infrahelvetic complex. Furthermore, the finite strain pattern, temperature distribution and timing of the 3D model is in broad agreement with data from the Helvetic nappe system. Our model, hence, provides a first-order 3D reconstruction of the tectonic evolution of the Helvetic nappe system based on thermo-mechanical deformation processes.

From Fold-and-Thrust Belts on Salt to Salt Deposition and Tectonics in a Fold-and-Thrust Belt, Sivas, Turkey

2015 ◽  
Author(s):  
Jean-Claude Ringenbach* ◽  
Etienne Legeay ◽  
Charlie Kergaravat ◽  
Jean-Paul Callot
Keyword(s):  
Thrust Belt ◽  
Salt Deposition ◽  
Thrust Belts ◽  
Fold And Thrust Belt ◽  
Fold And Thrust Belts

The Role of Isostasy in the Evolution of Thin-Skinned Fold and Thrust Belt

2021 ◽  
Author(s):  
Youseph Ibrahim ◽  
Patrice Rey
Keyword(s):  
Numerical Experiments ◽  
Basal Layer ◽  
Structural Evolution ◽  
Geological Model ◽  
Thrust Belt ◽  
Isostatic Adjustment ◽  
Flexural Response ◽  
Thrust Belts ◽  
Fold And Thrust Belt ◽  
Fold And Thrust Belts

<p>The stacking of thrust sheets and mass transfer of sediment during fold and thrust belt accretion imposes a load on the basement and underlying mantle. This load induces an isostatic adjustment through a flexural response, which may also contribute to the overall architecture of the fold and thrust belt. Whereas plate kinematics imposes its tempo to evolving fold and thrust belts, the rheology of the mantle controls the tempo of the isostatic flexure. Using two-dimensional high-resolution numerical experiments, we explore how the interplay between the tectonic compressional rate and the isostatic flexural rate influences the structural evolution and final architecture of fold and thrust belts. </p><p>We run a suite of numerical experiments using the well-tested code Underworld. Our geological model is mapped over a 42 km by 16 km numerical grid, with a cell resolution of 80 m. The geological model consists from top to bottom of  ‘sticky air’, 4 km of sediment that alternates in competence at 500 m intervals, a 3 km thick basement, and a basal layer which - in combination with a basal kinematic boundary condition - controls the amount of isostatic flexure. Materials have a mechanical behavior that results from elasto-visco-plastic rheology. The pressure at the base of the model is held constant, and the vertical velocity is updated at each timestep. The amount of material entering or exiting the model at each point along the base scales with the density of the basal layer, which is used to control the isostatic rate. Sedimentation and erosion are self-consistent through mechanical erosion and a hillslope diffusion law. Our models show that as the ratio between tectonic and flexural rates decreases (i.e. flexure gets faster), fold and thrust belts become narrower, lower in elevation, and structurally more complex. We compare these results with natural analogs including the Cordilleran and Jura fold and thrust belts.</p>

Age and origin of accreted ocean plate stratigraphy in the North Qilian belt, NE Tibet Plateau: Evidences from microfossils and geochemistry of cherts and siltstones

2021 ◽  
pp. jgs2020-231
Author(s):  
Zhen Yan ◽  
Wenjiao Xiao ◽  
Jonathan C. Aitchison ◽  
Chao Yuan ◽  
Chuanzhou Liu ◽  
...  
Keyword(s):  
Tibet Plateau ◽  
Geochemical Analysis ◽  
Accretionary Complex ◽  
Content Type ◽  
Middle Ordovician ◽  
The North ◽  
Ophiolitic Mélange ◽  
Thrust Belts ◽  
Fold And Thrust Belts ◽  
North Qilian

The accretionary complex (AC) in the North Qilian belt comprises coherent and chaotic units consisting of bedded cherts, pelagic mudstone, shale, turbidites, basalt, limestone, blueschist, eclogite lenses, and ophiolitic mélange. Cherts from the Donggoukou and Biandukou outcrops in the north of blueschist belt contain abundant Middle Ordovician radiolarians together with rare conodonts. Well-preserved radiolarians also occur in cherts associated with high-pressure/low-temperature rocks in the Baijingsi AC outcrop. Conodonts of Floian-Dapingian age and Middle Ordovician radiolarians also occur in the Shihuigou AC. Geochemical analysis of 23 cherts reveals variable SiO2 contents (74.56-97.16 wt%) and high mean Al/(Al + Fe + Mn) ratios ranging from 0.35 to 0.85, indicating a non-hydrothermal origin. Ce/Ce* and LaN/YbN ratios of 0.70-1.22 and 0.67-1.59 are high and variable, similar to those of associated muddy siltstone (0.59-0.96 and 1.14-1.55, respectively), suggesting near trench deposition with associated terrigenous input. Together with the metamorphic ages of blueschists and eclogites, the North Qilian belt AC formed by accretion of ocean plate stratigraphic successions in response to subduction of the Proto-Tethyan Ocean prior to 450 Ma.Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

Post-orogenic sediment drape and flux of mountain range-foreland basin systems: An example from the Northern Pyrenees

2020 ◽  
Author(s):  
Thomas Bernard ◽  
Hugh Sinclair ◽  
Mark Naylor ◽  
Elliot Weir ◽  
Frédéric Christophoul ◽  
...  
Keyword(s):  
Sediment Accumulation ◽  
Foreland Basin ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Crustal Thickening ◽  
Mountain Range ◽  
Foreland Basins ◽  
Isostatic Rebound ◽  
Basin Subsidence ◽  
Mountain Front

<p>The transition from syn- to post-orogenesis is generally identified in foreland basins by a switch from active subsidence and deposition to isostatic rebound and erosion. However, the nature of the interplay between isostatic rebound and sediment supply, and their impact on the topographic evolution of a range and foreland basin during this transition has not been fully explored.</p><p>Here, we use a box model to explore the syn- to post-orogenic evolution of foreland basin/thrust wedge systems. Using a set of parameter values that approximate the northern Pyrenees and the neighbouring Aquitaine foreland basin, we evaluate the controls on: 1) the sediment drape over the frontal parts of the retro-wedge and 2) the sediment accumulation into surrounding continental margins following cessation of crustal thickening. Conglomerate and sandstone sediments preserved at approximately 600 m elevation, which is ~300 m above the present mountain front in the northern Pyrenees record an age of ca. 12 Ma, approximately 8 Myrs younger than the last evidence of crustal thickening in the wedge. These sediments formed a regional drape that reached up to approximately 800 m elevation, but are now preserved in low gradient patches, and are associated with more regional surfaces across the northern Pyrenees. Using the model, this post-orogenic sediment drape can be explained by the combination of a sustained, high sediment influx from the range into the basin relative to the efflux out of the basin, combined with cessation of basin subsidence. The model also predicts higher sediment flux out of the system during the post-orogenic phase involving an increase of sediment accumulation as observed in the Bay of Biscay during this interval.</p><p>Post-orogenic sediment drape and increased sediment flux out the mountain range-foreland basin system are proposed as generic processes of these systems.</p>

scholarly journals Basin evolution in response to flat subduction in the Altiplano

2021 ◽  
pp. jgs2021-003
Author(s):  
Brook Runyon ◽  
Joel E. Saylor ◽  
Brian K. Horton ◽  
James H. Reynolds ◽  
Brian Hampton
Keyword(s):  
Foreland Basin ◽  
Flat Slab ◽  
Content Type ◽  
Link Type ◽  
Early Oligocene ◽  
Provenance Data ◽  
Thrust Belts ◽  
Fold And Thrust Belts ◽  
Basin Formation ◽  
Supplementary Material

This contribution assesses models for basin formation in the Altiplano. New magnetostratigraphy, palynology, and 40Ar/39Ar and U-Pb geochronology from the central Corque Syncline demonstrate that the 7.4 km-thick section was deposited between 36.7 and 18.7 Ma. The base of the section post-dates exhumation in both the Western and Eastern cordilleras, precluding deposition in a classic retroarc foreland basin setting. Rotated paleomagnetic vectors indicate counterclockwise rotation of 0.8°/Myr since the early Oligocene. Detrital zircon provenance data confirm previous interpretations of Eocene–early Oligocene derivation from the Western Cordillera and a subsequent switch to an Eastern Cordilleran source. Flexural modeling indicates that loads consistent with paleoelevation estimates cannot account for all subsidence. Rather, the timing and magnitude of subsidence is consistent with Eocene emplacement and Oligocene–early Miocene resteepening of a flat slab. Integration of the magmatic, basin, and deformation history provides a coherent model of the effects of flat subduction on the overriding plate. In this model flat subduction controlled basin formation in the upper plate, with subsidence enhanced in front of the zone of flat subduction but reduced over the crest of the flat slab. We conclude that the Altiplano was conditioned for plateau formation by Eocene–Oligocene flat subduction.Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-beltsSupplementary material:https://doi.org/10.6084/m9.figshare.c.5664345

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