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The configuration and kinematics of fold‐thrust belts are essential for clarifying the plate boundary conditions through which ancient orogenic belts evolved. Temporal and spatial variations in extension versus contraction within convergent plate margins are related to changes in plate kinematics and subduction geometry. The Yanshan Mountains, located along the northeastern margin of the North China Craton and bounded by the Central Asian Orogenic Belt to the north and the Pacific subduction zone to the east, underwent multiple phases of intra‐continental deformation during the Mesozoic. The issue of whether early Mesozoic deformation was extensional or contractional has remained controversial. New regional structural mapping and detailed sedimentological investigations, coupled with age constraints provided by zircon U‐Pb geochronology, provide sufficient temporal and spatial resolution to show that shortening and thrust‐top basin systems dominated during the early Mesozoic. Our results show that the Dengzhangzi Basin within the Lingyuan fold‐thrust belt developed during the construction of a major Late Triassic Chapeng antiformal‐stack duplex system, with episodic, east‐vergent forward‐breaking thrusts and subsequent 'beheading' by out‐of‐sequence, top‐to‐east thrusting in the latest Triassic or earliest Jurassic. The neighbouring Guojiadian Basin in the east was generated during top‐to‐SSE sinistral transpression along the Niuyingzi thrust system in the Middle to earliest Late Jurassic. These results support a new model of early craton decratonization involving (a) thrusting along the northern margin of the North China Craton and (b) transpressional deformation in the east driven by the Central Asian Ocean collision and flat‐slab subduction of the Palaeo‐Pacific Plate beneath the East Asian continental margin. Our findings suggest that large‐scale shortening and crustal/lithospheric thickening, triggered by flat‐slab subduction in the North China Craton, were fundamental components of craton decratonization. Subsequent slab roll‐back during the Cretaceous led to lithospheric thinning and crustal extension in the North China Craton. [ABSTRACT FROM AUTHOR]

In the northwestern sector of the Zagros foreland basin, axial fluvial systems initially delivered fine‐grained sediments from northwestern source regions into a contiguous basin, and later transverse fluvial systems delivered coarse‐grained sediments from northeastern sources into a structurally partitioned basin by fold‐thrust deformation. Here we integrate sedimentologic, stratigraphic, palaeomagnetic and geochronologic data from the northwestern Zagros foreland basin to define the Neogene history of deposition and sediment routing in response to progressive advance of the Zagros fold‐thrust belt. This study constrains the depositional environments, timing of deposition and provenance of nonmarine clastic deposits of the Injana (Upper Fars), Mukdadiya (Lower Bakhtiari) and Bai‐Hasan (Upper Bakhtiari) Formations in the Kurdistan region of Iraq. Sediments of the Injana Formation (~12.4–7.75 Ma) were transported axially (orogen‐parallel) from northwest to southeast by meandering and low‐sinuosity channel belt system. In contrast, during deposition of the Mukdadiya Formation (~7.75–5 Ma), sediments were delivered transversely (orogen‐perpendicular) from northeast to southwest by braided and low‐sinuosity channel belt system in distributive fluvial megafans. By ~5 Ma, the northwestern Zagros foreland basin became partitioned by growth of the Mountain Front Flexure and considerable gravel was introduced in localized alluvial fans derived from growing topographic highs. Foredeep accumulation rates during deposition of the Injana, Mukdadiya and Bai‐Hasan Formations averaged 350, 400 and 600 m/Myr respectively, suggesting accelerated accommodation generation in a rapidly subsiding basin governed by flexural subsidence. Detrital zircon U‐Pb age spectra show that in addition to sources of Mesozoic‐Cenozoic cover strata, the Injana Formation was derived chiefly from Palaeozoic‐Precambrian (including Carboniferous and latest Neoproterozoic) strata in an axial position to the northwest, likely from the Bitlis‐Puturge Massif and broader Eastern Anatolia. In contrast, the Mukdadiya and Bai‐Hasan Formations yield distinctive Palaeogene U‐Pb age peaks, particularly in the southeastern sector of the study region, consistent with transverse delivery from the arc‐related terranes of the Walash and Naopurdan volcano‐sedimentary groups (Gaveh‐Rud domain?) and Urumieh‐Dokhtar magmatic arc to the northeast. These temporal and spatial variations in stratigraphic framework, depositional environments, sediment routing and compositional provenance reveal a major drainage reorganization during Neogene shortening in the Zagros fold‐thrust belt. Whereas axial fluvial systems initially dominated the foreland basin during early orogenesis in the Kurdistan region of Iraq, transverse fluvial systems were subsequently established and delivered major sediment volumes to the foreland as a consequence of the abrupt deformation advance and associated topographic growth in the Zagros. [ABSTRACT FROM AUTHOR]

This study analyzes detrital zircon U–Pb age populations from Andean rivers to assess whether active synorogenic sedimentation accurately records proportional contributions from varied bedrock source units across different drainage areas. Samples of modern river sand were collected from west-central Argentina (28–33°S), where the Andes are characterized by active uplift and deposition in diverse contractional provinces, including (1) hinterland, (2) wedge-top, (3) proximal foreland, and (4) distal broken foreland basin settings. Potential controls on sediment provenance were evaluated by comparing river U–Pb age distributions with predicted age spectra generated by a sediment mixing model weighted by relative catchment exposure (outcrop) areas for different source units. Several statistical measures (similarity, likeness, and cross-correlation) are employed to compare how well the area-weighted model predicts modern river age populations. (1) Hinterland basin provenance is influenced by local relief generated along thrust-bounded ranges and high zircon fertility of exposed crystalline basement. (2) Wedge-top (piggyback) basin provenance is controlled by variable lithologic durability among thrust-belt bedrock sources and recycled basin sediments. (3) Proximal foreland (foredeep) basin provenance of rivers and fluvial megafans accurately reflect regional bedrock distributions, with limited effects of zircon fertility and lithologic durability in large (>20,000 km 2 ) second-order drainage systems. (4) In distal broken segments of the foreland basin, regional provenance signatures from thrust-belt and hinterland areas are diluted by local contributions from foreland basement-cored uplifts. [ABSTRACT FROM AUTHOR]

A >15-20 km-thick succession in southern Bolivia forms the most-complete stratigraphic record in western Gondwana. Upper Neoproterozoic–Carboniferous clastic rocks record ∼300 Myr of marine, nonmarine, and glacially influenced sedimentation in diverse basin systems generated by variable tectonic regimes along the western edge of Gondwana during active and passive-margin conditions. New provenance results help resolve key uncertainties regarding source regions and sediment dispersal patterns. The findings are integrated with spatial variations in stratigraphic thicknesses to evaluate regional patterns of basin subsidence, magmatism, and deformation during long-term evolution of the western Gondwanan margin in the central Andes. Detrital zircon U–Pb geochronological data for 17 sandstone samples reveal sedimentary input from Precambrian cratonic basement provinces and pre-Andean basement, magmatic arc, and fold-thrust belt source regions. The basement age signatures indicate derivation from the flanking Brasiliano (900-560 Ma) and Pampean (650-500 Ma) provinces to the south and east, and the distal Rio de la Plata craton (2400-2000 Ma) along the eastern South American margin ∼1000–1500 km to the southeast. Although the greater Amazonian craton was not a major contributor, subordinate Amazonian signatures from the Sunsás (1300-950 Ma) province to the east and northeast selectively fed the northern basin regions of the central Andes. Despite the lack of Paleozoic igneous rocks in Bolivia, detrital zircons of Ordovician age attest to the pre-Andean influence of the subduction-related Famatinian magmatic arc. Limited Devonian-Carboniferous igneous material was contributed locally from western pre-Andean highlands or regionally by axial northward transport from selected igneous sources in Argentina and Chile. Episodic recycling of Neoproterozoic–Paleozoic basin fill, including a sharp reappearance of Famatinian-age detritus, can be linked to periods of Paleozoic crustal shortening and foreland sedimentation ascribed to Famatinian, Ocloyic, Chañic, or Gondwanide phases of deformation. The spatial distribution of sediment sources along with temporal shifts in sediment routing highlight several stages in the paleogeographic evolution of the western Gondwanan margin preserved in the central Andes. Initial regional subsidence spanned a multiphase Neoproterozoic to early Paleozoic history of Rodinia breakup, Brasiliano-Pampean orogenesis, and post-orogenic back-arc extension prior to final late Paleozoic amalgamation of Gondwana. The early Paleozoic onset of subduction and Famatinian arc magmatism led to high-magnitude subsidence (>10–15 km) likely driven by Ordovician slab rollback in an extensional back-arc basin. Thereafter, intermittent Paleozoic contraction in a poorly understood pre-Andean system (best expressed in the Eastern Cordillera of Bolivia and neighboring segments of northern Argentina and southern Peru) generated transient topographic loads that produced superimposed flexural foreland and successor basin systems. • Southern Bolivia contains the most-complete stratigraphic record of western Gondwana. • Detrital zircon U-Pb ages reveal Neoproterozoic-Paleozoic shifts in sediment sources. • Proximal and distal (>1000 km) cratonic sources fed pre-Andean sedimentary basins. • Slab rollback in a back-arc basin likely caused >10 km of Ordovician subsidence. • Cratonic and Famatinian arc/orogenic sources fed Paleozoic foreland/successor basins. [ABSTRACT FROM AUTHOR]

The Zagros fold-thrust belt in the Kurdistan region of Iraq encroached southward toward a rapidly subsiding Neogene foreland basin and was later partitioned by out-of-sequence shortening focused along the Mountain Front Flexure (MFF), as defined by new low-temperature thermochronologic, stratigraphic, and provenance results. Apatite (U-Th)/He ages document rapid deformation advance from the Main Zagros Fault to southern frontal structures (Kirkuk, Shakal, and Qamar thrusts) at ~ 10–8 Ma, followed by potential basement-involved out-of-sequence development of the MFF (Qaradagh anticline) by ~ 5 Ma. Distinct shifts in detrital zircon U-Pb provenance signatures for Neogene foreland basin fill provide evidence for drainage reorganization during fold-thrust belt advance. U-Pb age spectra and petrologic data from the Injana (Upper Fars) Formation indicate derivation from a variety of Eurasian, Pan-African, ophiolitic and Mesozoic-Cenozoic volcanic terranes, whereas the Mukdadiya (Lower Bakhtiari) and Bai-Hasan (Upper Bakhtiari) Formations show nearly exclusive derivation from the Paleogene Walash-Naopurdan volcanic complex near the Iraq-Iran border. Such a sharp cutoff in Eurasian, Pan-African, and ophiolitic sources is likely associated with drainage reorganization and tectonic development of the geomorphic barrier formed by the MFF. As a result of Zagros crustal shortening, thickening and loading, the Neogene foreland basin developed and accommodated an abrupt influx of fluvial clastic sediment that contains growth stratal evidence of synkinematic accumulation. The apparent out-of-sequence pattern of upper crustal shortening in the hinterland to foreland zone of Iraqi Kurdistan suggests that structural inheritance and the effects of synorogenic erosion and accumulation are important factors influencing the irregular and episodic nature of orogenic growth in the Zagros. [ABSTRACT FROM AUTHOR]

Broken foreland basins are caused by crustal-scale contractional basement structures that compartmentalize (or break) a contiguous retroarc or collisional foreland basin into smaller disconnected basins. Broken foreland basins differ from their unbroken counterparts in their deformational, depositional, and geodynamic framework. Whereas contiguous (unbroken) foreland basins are generated mainly by regional flexural loading due to shortening of supracrustal cover strata and uppermost basement in organized ramp-flat thrust systems, broken foreland basins are governed principally by isolated topographic loads and structural tilting associated with widely spaced crustal-scale reverse faults that accommodate intraplate basement shortening. These structural contrasts foster either décollement-style fold-thrust belts (orogenic wedges) with large integrated erosional drainage systems (watersheds) spanning diverse sediment source regions (including thin-skinned fold-thrust belts, elevated hinterland zones, accreted terranes, and magmatic arcs) or independent foreland block uplifts with local drainage systems dominated by basement sources. Although the genesis of broken foreland basins has been uniquely attributed to flat slab subduction, these basins are also sensitive to inherited structural, stratigraphic, thermal, and rheological configurations, as well as synorogenic mass redistribution in relationship to climate, erosion, sediment transport efficiency, and sediment accumulation. Despite the many modern and ancient examples, questions persist over the underlying geodynamic processes that promote development of a broken or compartmentalized foreland basin instead of a single regionally unified flexural foreland basin. Additional uncertainties and misconceptions surround the criteria used to define broken foreland basins and their linkages to subduction dynamics (chiefly slab geometry), strain magnitude, and structural reactivation. Here we review the tectonic framework of broken foreland basins—with emphasis on South and North America (Pampean and Laramide provinces)—and propose that their genesis can be ascribed to a combination of: (i) underlying conditions in the form of tectonic inheritance, including precursor structural, stratigraphic, thermal, and rheological heterogeneities and anisotropies; and (ii) mechanical triggers, such as increased stress, enhanced horizontal stress transmission, and/or selective crustal strengthening or weakening. [ABSTRACT FROM AUTHOR]

Andean Cenozoic shortening within the Malargüe fold–thrust belt of west-central Argentina has been dominated by basement faults largely influenced by pre-existing Mesozoic rift structures of the Neuquén basin system. The basement contractional structures, however, diverge from many classic inversion geometries in that they formed large hanging-wall anticlines with steeply dipping frontal forelimbs and structural relief in the order of several kilometres. During Cenozoic E–W shortening, the reactivated basement faults propagated into cover strata, feeding slip to shallow thrust systems that were later carried in piggyback fashion above newly formed basement structures, yielding complex thick- and thin-skinned structural relationships. In the adjacent foreland, Cenozoic clastic strata recorded the broad kinematic evolution of the fold–thrust belt. We present a set of structural cross-sections supported by regional surface maps and industry seismic and well data, along with new stratigraphic information for associated Neogene synorogenic foreland basin fill. Collectively, these results provide important constraints on the temporal and geometric linkages between the deeper basement faults (including both reactivated and newly formed structures) and shallow thin-skinned thrust systems, which, in turn, offer insights for the understanding of hydrocarbon systems in the actively explored Neuquén region of the Andean orogenic belt. [ABSTRACT FROM PUBLISHER]

Compartmentalized or broken foreland basins are fundamental components of many convergent margins. Partitioning of collisional and retroarc foreland basins by basement-involved uplift has been linked commonly to flat-slab subduction, with an emerging appreciation for the important influence of: (1) regional and local inheritance of stratigraphic, structural, and crustal rheological heterogeneities; and (2) variations in climate, erosion, and sediment accumulation budgets. Shortening and basement uplift in broken foreland provinces greatly disrupts sediment routing patterns and preconditions vast regions for later phases of intracontinental deformation. Despite the wide range of settings in which broken foreland basins are recognized, there is limited understanding of the processes and controls on the common temporal transition from a single regionally integrated flexural foreland basin to a broken or compartmentalized foreland basin. We explore the stratigraphic, structural, sediment routing, and geodynamic evolution of several broken foreland systems to identify the key elements involved in the development of ancient and modern examples and to better assess the competing influences of flat-slab subduction, crustal inheritance, climate, erosion, and sedimentation. Broken foreland basin systems in ocean-continent convergent systems include the modern Central Andes of South America and the Late Cretaceous-Paleogene Laramide province of North America. In continent-continent collisional systems, broken foreland basins have been reported for both the downgoing and overriding plates (pro- and retro-wedge basins), including the Cenozoic Duero basin associated with the Spanish Pyrenean orogenic system and Mesozoic-Cenozoic basins of the Tibetan plateau within the India-Asia collision zone. A review of proposed broken foreland basins identifies some common stratigraphic and structural elements as well as some potential pitfalls, including the misinterpretation of ancient broken forelands in cases where foreland shortening was insufficient to generate positive topographic features capable of disrupting a contiguous (unbroken) foreland basin. [ABSTRACT FROM AUTHOR]

Reliable crustal shortening estimates for the central Andes (South America) are a critical component in validating models of Cordilleran processes. In southern Bolivia, insight into crustal shortening and the kinematic development of the Andean thrust belt are limited by the lack of a unified structural evaluation across the entire width of the retroarc region. To address these shortcomings, we (1) estimate crustal shortening by integrating new geologic mapping with published geophysical data to construct a balanced cross section across the Subandean zone (SAZ), Interandean zone (IAZ), and Eastern Cordillera (EC) at 21°S; (2) develop a kinematic model for the retroarc thrust belt; and (3) estimate crustal budgets and average crustal thicknesses over the region. We estimate 337 ± 69 km (36% ± 7%) of total shortening (SAZ, 82 km; IAZ, 70 km; EC, 120 km; Altiplano, 65 km). The thrust belt developed from late Eocene time to the present by tectonic wedging and eastward emplacement of two ~10-12-km-thick basement thrust sheets that distribute slip into overlying sedimentary rocks. Our range of crustal shortening values can account for 90%-118% of the current retroarc crustal area. Assuming an initial crustal thickness of 35 km, the EC and Altiplano did not achieve modern crustal thicknesses (~65 km) until the present. However, assuming a 40-km-thick initial crust, the EC and Altiplano attained the critical thickness for either eclogitic phase changes or lower crustal flow (>45-50 km) by ca. 27-25 Ma, modern thicknesses by ca. 10 Ma, and currently exceed geophysically observed thicknesses by ~2.5-14.5 km; this suggests crustal losses significant enough to have affected hinterland surface elevation. [ABSTRACT FROM AUTHOR]

Late Oligocene-early Miocene aridification in the retroarc foreland basin adjacent to the southern central Andes was recorded by widespread eolian conditions that coincided with accelerated subsidence driven by the main phase of Andean tectonic loading. An extensive eolian dune system, which is rare in most foreland basins, indicates specific conditions in terms of climate (aridity), atmospheric circulation, orography, sediment sources, dispersal patterns, and accommodation space. Detrital zircon U-Pb geochronological results for eolian sandstones spanning 20 foreland localities in northwestern to west-central Argentina, from 22°S to 36°S, reveal relatively localized Andean sources rather than regional cratonic provenance. Clastic detritus was largely derived from Phanerozoic igneous and sedimentary rocks of the Andean magmatic arc and retroarc fold-thrust belt during initial shortening-induced uplift of hinterland regions such as the Western Cordillera, Principal Cordillera, and Frontal Cordillera. This provenance record provides the earliest evidence for major westerly winds, transporting Andean detritus broadly eastward to the foreland basin (with common axial northward deflections) during a climate shift marked by the latest Oligocene-earliest Miocene inception of arid conditions. In addition to the climatic implications, independent stratigraphic data provide the basis for a compilation of sediment accumulation histories showing that eolian deposition was synchronous with accelerated subsidence attributable to enhanced Andean shortening. We propose that accelerated Andean uplift in the latest Oligocene-early Miocene generated rain-shadow conditions contemporaneous with increased sediment accommodation in the foreland basin, underscoring the important influence of tectonic processes on regional climate. • Latest Oligocene-early Miocene aridification in the Andean foreland basin (22-36°S) recorded by widespread eolian conditions. • Eolian sand deposition coincided with accelerated subsidence during inception of major Andean shortening and tectonic loading. • Foreland aridification and westerly winds represent the growth of an orographic rain shadow induced by Andean uplift. • Zircon U-Pb provenance data show local Andean sources and east-directed eolian transport with northward (axial) deflections. • Orographically modulated climate and tectonically driven accommodation space helped govern Andean foreland basin evolution. [ABSTRACT FROM AUTHOR]