Structural development of Neogene basins in western Greece

Abstract An account is given of the structural setting of the various Neogene sedimentary basins of western Greece. Compressional basins are attributable to foreland loading by the Alpine fold and thrust belt of the Outer Hellenides, and to active subduction in the adjacent western Hellenic arc. Late extensional basins are related to N-S crustal extension in the Aegean marginal basin and, in western Greece, are superimposed on the earlier compressional structures. The local seismicity provides evidence that the main E-W-trending basin-bounding faults of the extensional basins form a linked system that includes NW-SE- and NE-SW-trending transfer zones of transtension. The transfer zones are themselves the sites of small extensional basins.     

Influence of structural framework on mountain slope deformation in the Maiella anticline (Central Apennines, Italy)

Relationships between tectonic framework and gravity-driven phenomena have been investigated in an area of the Central Apennines (Italy) characterised by high relief. The north–south, half-dome shaped Maiella anticline lies in the easternmost part of the Apennine fold-and-thrust belt. Its backlimb is bordered by the Caramanico Fault, a normal fault with a maximum downthrown of about 3.5 km that separates the western slope of the Maiella Massif from the Caramanico Valley. The southwestern Maiella area is affected by deep-seated gravitational slope deformation indicated by major double crest lines, down-hill and up-hill facing scarps, a pattern of crossing trenches, bulging at the base of slopes and the presence of different types of landslide and talus slope deposits.The onset and development of deep-seated gravitational slope deformations and the location of Quaternary, massive rockslope failures have been strongly influenced by the structural framework and tectonic pattern of the anticline. Deep-seated gravitational slope deformation at Mt. Macellaro–Mt. Amaro ridge has developed along the Maiella western, reverse slope in correspondence with the anticline axial culmination; it is bordered at the rear by a NNW–SSE oriented, dextral, strike-slip fault zone and has an E–W direction of rock mass deformation. Closer to the southern plunging area of the anticline, gravity-driven phenomena show instead a N–S and NW–SE direction, influenced by bedding attitude.3D topographic models illustrate the relationship between deep-seated gravitational slope deformation and massive rockslope failures. The Campo di Giove rock avalanche, a huge Quaternary failure event, was the result of an instantaneous collapse on a mountaine slope affected by a long-term gravity-driven deformation.     

Along‐strike structural linkage and interaction in an active thrust fault system: A case study from the western Sichuan foreland basin,China

Along‐strike structural linkage and interaction between faults is common in various compressional settings worldwide. Understanding the kinematic history of fault interaction processes can provide important constraints on the geometry and evolution of the lateral growth of segmented faults in the fold‐and‐thrust belts, which are important to seismic hazard assessment and hydrocarbon trap development. In this study, we study lateral structural geometry (fault displacement and horizon shortening) of thrust fault linkages and interactions along the Qiongxi anticline in the western Sichuan foreland basin, China, using a high‐resolution 3D seismic reflection dataset. Seismic interpretation suggests that the Qiongxi anticline can be related to three west‐dipping, hard‐linked thrust fault segments that sole onto a regional shallow detachment. Results reveal that the lateral linkage of fault segments limited their development, affecting the along‐strike fault displacement distributions. A deficit between shortening and displacement is observed to increase in linkage zones where complex structural processes occur, such as fault surface bifurcation and secondary faulting, demonstrating the effect of fault linkage process on structural deformation within a thrust array. The distribution of the geometrical characteristics shows that thrust fault development in the area can be described by both the isolated fault model and the coherent fault model. Our measurements show that new fault surfaces bifurcate from the main thrust ramp, which influences both strain distribution in the relay zone and along‐strike fault slip distribution. This work fully describes the geometric and kinematic characteristics of lateral thrust fault linkage, and may provide insights into seismic interpretation strategies in other complex fault transfer zones.     

Evolution of the late Cenozoic Chaco foreland basin, Southern Bolivia

Eastward Andean orogenic growth since the late Oligocene led to variable crustal loading, flexural subsidence and foreland basin sedimentation in the Chaco basin. To understand the interaction between Andean tectonics and contemporaneous foreland development, we analyse stratigraphic, sedimentologic and seismic data from the Subandean Belt and the Chaco Basin. The structural features provide a mechanism for transferring zones of deposition, subsidence and uplift. These can be reconstructed based on regional distribution of clastic sequences. Isopach maps, combined with sedimentary architecture analysis, establish systematic thickness variations, facies changes and depositional styles. The foreland basin consists of five stratigraphic successions controlled by Andean orogenic episodes and climate: (1) the foreland basin sequence commences between ～27 and 14 Ma with the regionally unconformable, thin, easterly sourced fluvial Petaca strata. It represents a significant time interval of low sediment accumulation in a forebulge‐backbulge depocentre. (2) The overlying ～14–7 Ma‐old Yecua Formation, deposited in marine, fluvial and lacustrine settings, represents increased subsidence rates from thrust‐belt loading outpacing sedimentation rates. It marks the onset of active deformation and the underfilled stage of the foreland basin in a distal foredeep. (3) The overlying ～7–6 Ma‐old, westerly sourced Tariquia Formation indicates a relatively high accommodation and sediment supply concomitant with the onset of deposition of Andean‐derived sediment in the medial‐foredeep depocentre on a distal fluvial megafan. Progradation of syntectonic, wedge‐shaped, westerly sourced, thickening‐ and coarsening‐upward clastics of the (4) ～6–2.1 Ma‐old Guandacay and (5) ～2.1 Ma‐to‐Recent Emborozú Formations represent the propagation of the deformation front in the present Subandean Zone, thereby indicating selective trapping of coarse sediments in the proximal foredeep and wedge‐top depocentres, respectively. Overall, the late Cenozoic stratigraphic intervals record the easterly propagation of the deformation front and foreland depocentre in response to loading and flexure by the growing Intra‐ and Subandean fold‐and‐thrust belt.     

Cenozoic stratigraphy and subsidence history of the South China Sea margin in the Taiwan region

Seismic reflection profiles and well data are used to determine the Cenozoic stratigraphic and tectonic development of the northern margin of the South China Sea. In the Taiwan region, this margin evolved from a Palaeogene rift to a latest Miocene–Recent foreland basin. This evolution is related to the opening of the South China Sea and its subsequent partial closure by the Taiwan orogeny. Seismic data, together with the subsidence analysis of deep wells, show that during rifting (～58–37 Ma), lithospheric extension occurred simultaneously in discrete rift belts. These belts form a >200 km wide rift zone and are associated with a stretching factor, β, in the range ～1.4–1.6. By ～37 Ma, the focus of rifting shifted to the present‐day continent–ocean boundary off southern Taiwan, which led to continental rupture and initial seafloor spreading of the South China Sea at ～30 Ma. Intense rifting during the rift–drift transition (～37–30 Ma) may have induced a transient, small‐scale mantle convection beneath the rift. The coeval crustal uplift (Oligocene uplift) of the previously rifted margin, which led to erosion and development of the breakup unconformity, was most likely caused by the induced convection. Oligocene uplift was followed by rapid, early post‐breakup subsidence (～30–18 Ma) possibly as the inferred induced convection abated following initial seafloor spreading. Rapid subsidence of the inner margin is interpreted as thermally controlled subsidence, whereas rapid subsidence in the outer shelf of the outer margin was accompanied by fault activity during the interval ～30–21 Ma. This extension in the outer margin (β～1.5) is manifested in the Tainan Basin, which formed on top of the deeply eroded Mesozoic basement. During the interval ～21–12.5 Ma, the entire margin experienced broad thermal subsidence. It was not until ～12.5 Ma that rifting resumed, being especially active in the Tainan Basin (β～1.1). Rifting ceased at ～6.5 Ma due to the orogeny caused by the overthrusting of the Luzon volcanic arc. The Taiwan orogeny created a foreland basin by loading and flexing the underlying rifted margin. The foreland flexure inherited the mechanical and thermal properties of the underlying rifted margin, thereby dividing the basin into north and south segments. The north segment developed on a lithosphere where the major rift/thermal event occurred ～58–30 Ma, and this segment shows minor normal faulting related to lithospheric flexure. In contrast, the south segment developed on a lithosphere, which experienced two more recent rift/thermal events during ～30–21 and ～12.5–6.5 Ma. The basal foreland surface of the south segment is highly faulted, especially along the previous northern rifted flank, thereby creating a deeper foreland flexure that trends obliquely to the strike of the orogen.     

Determining kinematic order and relative age of faulting via flexural‐kinematic restoration: A case study in far western Nepal

Forward modeled, balanced cross sections that account for the flexural response to thrust loading and erosional unloading can verify and refine the kinematic sequence of deformation in fold‐thrust belts as well as help assess the validity of a balanced cross section. Results from flexural‐kinematic reconstructions that indicate either the cross section, the kinematic order or both are invalid include: (a) a predicted final topography that is dramatically different from the actual topography; (b) large normal fault or thrust fault bounded synorogenic basins that are not present in the mapped geology; and/or (c) an exhumation history that is not consistent with provenance records in the basin or measured thermochronometers. Where detailed measured foreland basin sections exist, flexural‐kinematic modeling of fold‐thrust belt deformation, including out‐of‐sequence (OOS) faults can predict a foreland basin evolution that can be compared to measured data. The modeling process creates a “pseudostratigraphy” in the modeled foreland. The pseudostratigraphy and predicted provenance of each modeled stratigraphic increment can be directly compared to measured stratigraphic sections. We present a case study using two cross sections through the Himalaya of far western Nepal (Api and Simikot) to assess the validity of the section geometries and the resulting kinematic histories, displacement rates, flexural wave response and predicted provenance for both sections. Insights from combining the flexural‐kinematic models with existing stratigraphic data include: (a) Changing the order of proposed OOS and normal faults to earlier in the evolution of the fold‐thrust belt was necessary to reproduce the foreland provenance data. We argue that OOS thrust and normal faults in the Api section occurred between 11 and 4 Ma. (b) Published shortening estimates for the Simikot cross section are too high (>50 km), resulting in unrealistic shortening rates up to 80 mm/yr between 25 and 20 Ma. (c) Flexural forward models with and without an additional sediment loading modeling step indicate that while sediment loading does not have a measurable effect on the magnitude and location of erosion within the fold‐thrust belt, it does have a small effect on accumulation rates and thus the predicted age of stratigraphic boundaries when compared to measured stratigraphic thicknesses and age. Thickness difference range from 0.2 to 0.5 km and can result in predicted age differences of ca. 1 Ma. Accounting for both flexural isostacy and erosion can eliminate unviable kinematic sequences and when combined with provenance data from measured stratigraphic sections, can provide insight into the order, age and rate of deformation.     

Evaluating foreland basin partitioning in the northern Andes using Cenozoic fill of the Floresta basin,Eastern Cordillera,Colombia

This paper addresses foreland basin fragmentation through integrated detrital zircon U–Pb geochronology, sandstone petrography, facies analysis and palaeocurrent measurements from a Mesozoic–Cenozoic clastic succession preserved in the northern Andean retroarc fold‐thrust belt. Situated along the axis of the Eastern Cordillera of Colombia, the Floresta basin first received sediment from the eastern craton (Guyana shield) in the Cretaceous–early Palaeocene and then from the western magmatic arc (Central Cordillera) starting in the mid‐Palaeocene. The upper‐crustal magmatic arc was replaced by a metamorphic basement source in the middle Eocene. This, in turn, was replaced by an upper‐crustal fold‐thrust belt source in the late Eocene which persisted until Oligocene truncation of the Cenozoic section by the eastward advancing thrust front. Sedimentary facies analysis indicates minimal changes in depositional environments from shallow marine to low‐gradient fluvial and estuarine deposits. These same environments are recorded in coeval strata across the Eastern Cordillera. Throughout the Palaeogene, palaeocurrent and sediment provenance data point to a uniform western or southwestern sediment source. These data show that the Floresta basin existed as part of a laterally extensive, unbroken foreland basin connected with the proximal western (Magdalena Valley) basin from mid‐Paleocene to late Eocene time when it was isolated by uplift of the western flank of the Eastern Cordillera. The Floresta basin was also connected with the distal eastern (Llanos) basin from the Cretaceous until its late Oligocene truncation by the advancing thrust front.     

Basin evolution of Upper Cretaceous–Lower Cenozoic strata in the Malargüe fold‐and‐thrust belt: northern Neuquén Basin,Argentina

The Andean Orogen is the type‐example of an active Cordilleran style margin with a long‐lived retroarc fold‐and‐thrust belt and foreland basin. Timing of initial shortening and foreland basin development in Argentina is diachronous along‐strike, with ages varying by 20–30 Myr. The Neuquén Basin (32°S to 40°S) contains a thick sedimentary sequence ranging in age from late Triassic to Cenozoic, which preserves a record of rift, back arc and foreland basin environments. As much of the primary evidence for initial uplift has been overprinted or covered by younger shortening and volcanic activity, basin strata provide the most complete record of early mountain building. Detailed sedimentology and new maximum depositional ages obtained from detrital zircon U–Pb analyses from the Malargüe fold‐and‐thrust belt (35°S) record a facies change between the marine evaporites of the Huitrín Formation (ca. 122 Ma) and the fluvial sandstones and conglomerates of the Diamante Formation (ca. 95 Ma). A 25–30 Myr unconformity between the Huitrín and Diamante formations represents the transition from post‐rift thermal subsidence to forebulge erosion during initial flexural loading related to crustal shortening and uplift along the magmatic arc to the west by at least 97 ± 2 Ma. This change in basin style is not marked by any significant difference in provenance and detrital zircon signature. A distinct change in detrital zircons, sandstone composition and palaeocurrent direction from west‐directed to east‐directed occurs instead in the middle Diamante Formation and may reflect the Late Cretaceous transition from forebulge derived sediment in the distal foredeep to proximal foredeep material derived from the thrust belt to the west. This change in palaeoflow represents the migration of the forebulge, and therefore, of the foreland basin system between 80 and 90 Ma in the Malargüe area.     

Miocene extensional basin development in the Betic Cordillera, SE Spain revealed through analysis of the Alhama de Murcia and Crevillente Faults

The Alhama de Murcia and Crevillente faults in the Betic Cordillera of southeast Spain form part of a network of prominent faults, bounding several of the late Tertiary and Quaternary intermontane basins. Current tectonic interpretations of these basins vary from late‐orogenic extensional structures to a pull‐apart origin associated with strike–slip movements along these prominent faults. A strike–slip origin of the basins, however, seems at variance both with recent structural studies of the underlying Betic basement and with the overall basin and fault geometry. We studied the structure and kinematics of the Alhama de Murcia and Crevillente faults as well as the internal structure of the late Miocene basin sediments, to elucidate possible relationships between the prominent faults and the adjacent basins. The structural data lead to the inevitable conclusion that the late Miocene basins developed as genuinely extensional basins, presumably associated with the thinning and exhumation of the underlying basement at that time. During the late Miocene, neither the Crevillente fault nor the Alhama de Murcia fault acted as strike–slip faults controlling basin development. Instead, parts of the Alhama de Murcia fault initiated as extensional normal faults, and reactivated as contraction faults during the latest Miocene–early Pliocene in response to continued African–European plate convergence. Both prominent faults presently act as reverse faults with a movement sense towards the southeast, which is clearly at variance with the commonly inferred dextral or sinistral strike–slip motions on these faults. We argue that the prominent faults form part of a larger scale zone of post‐Messinian shortening made up of SSE‐ and NNW‐directed reverse faults and NE to ENE‐trending folds including thrust‐related fault‐bend folds and fault‐propagation folds, transected and displaced by, respectively, WNW‐ and NNE‐trending, dextral and sinistral strike–slip (tear or transfer) faults.     

Tectono‐sedimentary evolution of the Plio‐Pleistocene Corinth rift,Greece

The onshore central Corinth rift contains a syn‐rift succession >3 km thick deposited in 5–15 km‐wide tilt blocks, all now inactive, uplifted and deeply incised. This part of the rift records upward deepening from fluviatile to lake‐margin conditions and finally to sub‐lacustrine turbidite channel and lobe complexes, and deep‐water lacustrine conditions (Lake Corinth) were established over most of the rift by 3.6 Ma. This succession represents the first of two phases of rift development – Rift 1 from 5.0–3.6 to 2.2–1.8 Ma and Rift 2 from 2.2–1.8 Ma to present. Rift 1 developed as a 30 km‐wide zone of distributed normal faulting. The lake was fed by four major N‐ to NE‐flowing antecedent drainages along the southern rift flank. These sourced an axial fluvial system, Gilbert fan deltas and deep lacustrine turbidite channel and lobe complexes. The onset of Rift 2 and abandonment of Rift 1 involved a 30 km northward shift in the locus of rifting. In the west, giant Gilbert deltas built into a deepening lake depocentre in the hanging wall of the newly developing southern border fault system. Footwall and regional uplift progressively destroyed Lake Corinth in the central and eastern parts of the rift, producing a staircase of deltaic and, following drainage reversal, shallow marine terraces descending from >1000 m to present‐day sea level. The growth, linkage and death of normal faults during the two phases of rifting are interpreted to reflect self‐organization and strain localization along co‐linear border faults. In the west, interaction with the Patras rift occurred along the major Patras dextral strike‐slip fault. This led to enhanced migration of fault activity, uplift and incision of some early Rift 2 fan deltas, and opening of the Rion Straits at ca. 400–600 ka. The landscape and stratigraphic evolution of the rift was strongly influenced by regional palaeotopographic variations and local antecedent drainage, both inherited from the Hellenide fold and thrust belt.     

Stratigraphic signatures of translation of thrust-sheet top basins over low-angle detachment faults

Abstract Low‐angle detachment faults and thrust‐sheet top basins are common features in foreland basins. However, in stratigraphic analysis their influence on sequence architecture is commonly neglected. Usually, only eustatic sea level and changing flexural subsidence are accounted for, and when deformation is considered, the emphasis is on the generation of local thrust‐flank unconformities. This study analyses the effects of detachment angle and repetitive detachment activation on stratigraphic stacking patterns in a large thrust‐sheet top basin by applying a three‐dimensional numerical model. Model experiments show that displacement over low‐angle faults (2–6°) at moderate rates (～5.0 m kyr^?1) results in a vertical uplift component sufficient to counteract the background flexural subsidence rate. Consequently, the basin‐wide accommodation space is reduced, fluvio‐deltaic systems carried by the thrust‐sheet prograde and part of the sediment supply is spilled over towards adjacent basins. The intensity of the forced regression and the interconnectedness of fluvial sheet sandstones increases with the dip angle of the detachment fault or rate of displacement. In addition, the delta plain is susceptible to the formation of incised valleys during eustatic falls because these events are less compensated by regional flexural subsidence, than they would be in the absence of fault displacement.     

Late Cenozoic structural and stratigraphic evolution of the northern Chinese Tian Shan foreland

Three successive zones of fault‐related folds disrupt the proximal part of the northern Tian Shan foreland in NW China. A new magnetostratigraphy of the Taxi He section on the north limb of the Tugulu anticline in the middle deformed zone clarifies the chronology of both tectonic deformation and depositional evolution of this collisional mountain belt. Our ～1200‐m‐thick section encompasses the upper Cenozoic terrigenous sequence within which ～300 sampling horizons yield an age span of ～8–2 Ma. Although the basal age in the Taxi He section of the Xiyu conglomerate (often cited as an indicator of initial deformation) is ～2.1 Ma, much earlier growth of the Tugulu anticline is inferred from growth strata dated at ～6.0 Ma. Folding of Neogene strata and angular unconformities in anticlines in the more proximal and distal deformed zones indicate deformation during Miocene and Early Pleistocene times, respectively. In the Taxi He area, sediment‐accumulation rates significantly accelerate at ～4 Ma, apparently in response to encroaching thrust loads. Together, growth strata, angular unconformities, and sediment‐accumulation rates document the northward migration of tectonic deformation into the northern Tian Shan foreland basin during the late Cenozoic. A progradational alluvial–lacustrine system associated with this northward progression is subdivided into two facies associations at Tugulu: a shallow lacustrine environment before ～5.9 Ma and an alluvial fan environment subsequently. The lithofacies progradation encompasses the time‐transgressive Xiyu conglomerate deposits, which should only be recognized as a lithostratigraphic unit. Along the length of the foreland, the locus of maximum shortening shifts between the medial and proximal zones of folding, whereas the total shortening across the foreland remains quite homogeneous along strike, suggesting spatially steady tectonic forcing since late Miocene times.     

Relay zone evolution: a history of repeated fault propagation and linkage,central Corinth rift,Greece

Established models indicate that, before being breached, relay zones along rift borders can evolve either by lengthening and rotating during progressive overlap of growing fault segments (isolated fault model), or, by simply rotating without lengthening before breaching (coherent fault model). The spatio‐temporal distribution of vertical motions in a relay zone can thus be used to distinguish fault growth mechanisms. Depositional relay zones that develop at sea level and accommodate both deposition on the ramp itself as well as transfer of sediments from the uplifting footwall into the hangingwall depocentres and provide the most complete record of vertical motions. We examine the development of a depositional relay ramp on the border of the active Corinth rift, Greece to reconstruct fault interaction in time and space using both onshore and offshore (2D seismic lines) data. The Akrata relay zone developed over a period of ca. 0.5 Myr since the Middle Pleistocene between the newly forming East Helike Fault (EHF) that propagated towards the older, more established Derveni Fault (DF). The relay zone captured the Krathis River, which deposited prograding Gilbert‐type deltas on the sub‐horizontal ramp. Successive oblique faults record progressive linkage and basinward migration of accommodation along the ramp axis, whereas marine terraces record diachronous uplift in their footwalls. Although early linkage of the relay zone occurs, continuous propagation and linkage of the EHF onto the static DF is recorded before final beaching. Rotation on forced folds above the upward and laterally propagating normal faults at the borders of the relay zone represents the ramp hinges. The Akrata relay zone cannot be compared directly to a simple fault growth model because (1) the relay zone connects two fault segments of different generations; (2) multiple linkages during propagation was facilitated by the presence of pre‐existing crustal structures, inherited from the Hellenide fold and thrust belt. The linkage of the EHF to the DF contributed to the westward and northward propagation of the southern rift border.     

Fluvial deposition during transition from flexural to dynamic subsidence in the Cordilleran foreland basin: Ericson Formation,Western Wyoming,USA

The Ericson Formation was deposited in the distal foredeep of the Cordilleran foreland basin during Campanian time. Isopach data show that it records early dynamic subsidence and the onset of basin partitioning by Laramide uplifts. The Ericson Formation is well exposed around the Rock Springs uplift, a Laramide structural dome in southwestern Wyoming; the formation is thin, regionally extensive, and does not display the wedge‐shaped geometry typical of foredeep deposits. Sedimentation in this area was controlled both by activity in the thrust belt and by intraforeland tectonics. The Ericson Formation is ideally situated both spatially and temporally to study the transition from Sevier to Laramide (thin‐ to thick‐skinned) deformation which corresponded to the shift from flexural to dynamic subsidence and the demise of the Cretaceous foreland basin system. We establish the depositional age of the Ericson Formation as ca. 74 Ma through detrital zircon U–Pb analysis. Palaeocurrent data show a generally southeastward transport direction, but northward indicators near Flaming Gorge Reservoir suggest that the intraforeland Uinta uplift was rising and shedding sediment northward by late Campanian time. Petrographic data and detrital zircon U–Pb ages indicate that Ericson sediment was derived from erosion of Proterozoic quartzites and Palaeozoic and Mesozoic quartzose sandstones in the Sevier thrust belt to the west. The new data place temporal and geographic constraints on attempts to produce geodynamic models linking flat‐slab subduction of the oceanic Farallon plate to the onset of the Laramide orogenic event.     

Timing of Xunhua and Guide basin development and growth of the northeastern Tibetan Plateau,China

The Xunhua, Guide and Tongren intermontane basin system in the NE Tibetan Plateau, situated near the Xining basin to the N and the Linxia basin to the E, is bounded by thrust fault‐controlled ranges. These include to the N, the Riyue Shan, Laji Shan and Jishi Shan ranges, and to the S the northern West Qinling Shan (NWQ). An integrated study of the structural geology, sedimentology and provenance of the Cenozoic Xunhua and Guide basins provides a detailed record of the growth of the NE Tibetan Plateau since the early Eocene. The Xining Group (ca. 52–21 Ma) is interpreted as consisting of unified foreland basin deposits which were controlled by the bounding thrust belt of the NWQ. The Xunhua, Guide and Xining subbasins were interconnected prior to later uplift and damming by the Laji Shan and Jishi Shan ranges. Their sediment source, the NWQ, is constrained by strong unidirectional paleocurrent trends towards the N, a northward fining lithology, distinct and recognizable clast types and detrital zircon ages. Collectively, formation of this mountain–basin system indicates that the Tibetan Plateau expanded into the NWQ at a time roughly coinciding with Eocene to earliest Miocene continental collision between India and Eurasia. The Guide Group (ca. 21–1.8 Ma) is inferred to have been deposited in the separate Xunhua, Guide and Tongren broken foreland basins. Each basin was filled by locally sourced alluvial fans, braided streams and deltaic‐lacustrine systems. Structural, paleogeographic, paleocurrent and provenance data indicate that thrust faulting in the NWQ stepped northward to the Laji Shan from ca. 21 to 16 Ma. This northward shift was accompanied by E–W shortening related to nearly N–S‐striking thrust faulting in Jishi Shan after 11–13 Ma. A lower Pleistocene conglomerate (1.8–1.7 Ma) was deposited by a through‐flowing river system in the overfilled and connected Guide and Xunhua basins following the termination of thrust activity. All of the basin–mountain zones developed along the Tibetan Plateau's NE margin since Indian–Tibetan continental collision may have been driven by collision‐induced basal drag of old slab remnants in the manner of N‐dipping and flat‐slab subduction, and their subsequent sinking into the deep mantle.     

The stratigraphic and structural evolution of the Dzereg Basin, western Mongolia: clastic sedimentation, transpressional faulting and basin destruction in an intraplate, intracontinental setting

The Dzereg Basin is an actively evolving intracontinental basin in the Altai region of western Mongolia. The basin is sandwiched between two transpressional ranges, which occur at the termination zones of two regional‐scale dextral strike‐slip fault systems. The basin contains distinct Upper Mesozoic and Cenozoic stratigraphic sequences that are separated by an angular unconformity, which represents a regionally correlative peneplanation surface. Mesozoic strata are characterized by northwest and south–southeast‐derived thick clast‐supported conglomerates (Jurassic) overlain by fine‐grained lacustrine and alluvial deposits containing few fluvial channels (Cretaceous). Cenozoic deposits consist of dominantly alluvial fan and fluvial sediments shed from adjacent mountain ranges during the Oligocene–Holocene. The basin is still receiving sediment today, but is actively deforming and closing. Outwardly propagating thrust faults bound the ranges, whereas within the basin, active folding and thrusting occurs within two marginal deforming belts. Consequently, active fan deposition has shifted towards the basin centre with time, and previously deposited sediment has been uplifted, eroded and redeposited, leading to complex facies architecture. The geometry of folds and faults within the basin and the distribution of Mesozoic sediments suggest that the basin formed as a series of extensional half‐grabens in the Jurassic–Cretaceous which have been transpressionally reactivated by normal fault inversion in the Tertiary. Other clastic basins in the region may therefore also be inherited Mesozoic depocentres. The Dzereg Basin is a world class laboratory for studying competing processes of uplift, deformation, erosion, sedimentation and depocentre migration in an actively forming intracontinental transpressional basin.     

Formation and fragmentation of a late Miocene supradetachment basin in central Crete: implications for exhumation mechanisms of high‐pressure rocks in the Aegean forearc

We present a new lithostratigraphy and chronology for the Miocene on central Crete, in the Aegean forearc. Continuous sedimentation started at ～10.8 Ma in the E–W trending fluvio‐lacustrine Viannos Basin, formed on the hangingwall of the Cretan detachment, which separates high‐pressure (HP) metamorphic rocks from very low‐grade rocks in its hangingwall. Olistostromes including olistoliths deposited shortly before the Viannos Basin submerged into the marine Skinias Basin between 10.4 and 10.3 Ma testifies to significant nearby uplift. Uplift of the Skinias Basin between 9.7 and 9.6 Ma, followed by fragmentation along N–S and E–W striking normal faults, marks the onset of E–W arc‐parallel stretching superimposed on N–S regional Aegean extension. This process continued between 9.6 and 7.36 Ma, as manifested by tilting and subsidence of fault blocks with subsidence events centred at 9.6, 8.8, and 8.2 Ma. Wholesale subsidence of Crete occurred from 7.36 Ma until ～5 Ma, followed by Pliocene uplift and emergence. Subsidence of the Viannos Basin from 10.8 to 10.4 Ma was governed by motion along the Cretan detachment. Regional uplift at ～10.4 Ma, followed by the first reworking of HP rocks (10.4–10.3 Ma) is related to the opening and subsequent isostatic uplift of extensional windows exposing HP rocks. Activity of the Cretan detachment ceased sometime between formation of extensional windows around 10.4 Ma, and high‐angle normal faulting cross‐cutting the detachment at 9.6 Ma. The bulk of exhumation of the Cretan HP‐LT metamorphic rocks occurred between 24 and 12 Ma, before basin subsidence, and was associated with extreme thinning of the hangingwall (by factor ～10), in line with earlier inferences that the Cretan detachment can only explain a minor part of total exhumation. Previously proposed models of buyoant rise of the Cretan HP rocks along the subducting African slab provide an explanation for extension without basin subsidence.     

Subsidence history from a backstripping analysis of the Permo‐Mesozoic succession of the Central Southern Alps (Northern Italy)

Seven tectonic subsidence curves, based on outcrop data, have been calculated in order to constrain the geodynamic evolution of the Permian–Mesozoic sedimentary succession (up to 10 km thick) of the Central Southern Alps basin (Italy). The analysis of the tectonic subsidence curves, covering a time span of about 200 Ma, allowed us to quantify the subsidence rates, to document the activity of syndepositional fault systems and calculate their slip rates. Different stages, in terms of duration and magnitude of subsidence‐uplift trends, have been identified in the evolution of the basin. The fault activity, reconstructed by comparing subsidence curves from adjacent sectors, resulted as highly variable both temporally and spatially. Strike‐slip tectonics was coeval to Permian sedimentation, as suggested by the strong differences in the subsidence rates in the sections. The evolution and subsidence rates suggest a continental shelf deposition from Early Triassic to Carnian, when subsidence came to a stop. A rapid resumption of subsidence is observed from the Norian, with a subsidence pulse in the Late Norian, followed by the regional uplift, in the Late Rhaetian. The following Early Jurassic subsidence is characterized by tectonic subsidence similar to that of the Norian. The Norian and Early Jurassic pulses were characterized by the highest slip rates along growth faults and are identified as two distinct tectonic events. The Norian–Rhaetian event is tentatively related to transtensional tectonics whereas the Early Jurassic event is related to crustal extension. The Early Jurassic subsidence records a shift in space an time of the beginning of the extensional stage, from Late Hettangian to the east to Late Pliensbachian–Toarcian to the west. From the Toarcian to the Aptian, the curves are compatible with regional thermal subsidence, later followed (Albian–Cenomanian) by uplift pulses in a retrobelt foreland basin (from Cenomanian onward).     

Sediment routing evolution in the North Alpine Foreland Basin,Austria: interplay of transverse and longitudinal sediment dispersal

Integration of detrital zircon geochronology and three‐dimensional (3D) seismic‐reflection data from the Molasse basin of Austria yields new insight into Oligocene‐early Miocene palaeogeography and patterns of sediment routing within the Alpine foreland of central Europe. Three‐dimensional seismic‐reflection data show a network of deep‐water tributaries and a long‐lived (>8 Ma) foredeep‐axial channel belt that transported Alpine detritus greater than 100 km from west to east. We present 793 new detrital zircon ages from 10 sandstone samples collected from subsurface cores located within the seismically mapped network of deep‐water tributaries and the axial channel belt. Grain age populations correspond with major pre‐Alpine orogenic cycles: the Cadomian (750–530 Ma), the Caledonian (490–380 Ma) and the Variscan (350–250 Ma). Additional age populations correspond with Eocene‐Oligocene Periadriatic magmatism (40–30 Ma) and pre‐Alpine, Precambrian sources (>750 Ma). Although many samples share the same age populations, the abundances of these populations vary significantly. Sediment that entered the deep‐water axial channel belt from the west (Freshwater Molasse) and southwest (Inntal fault zone) is characterized by statistically indistinguishable age distributions that include populations of Variscan, Caledonian and Cadomian zircon at modest abundances (15–32% each). Sandstone from a shallow marine unit proximal to the northern basin margin consists of >75% Variscan (350–300 Ma) zircon, which originated from the adjacent Bohemian Massif. Mixing calculations based on the Kolmogorov–Smirnoff statistic suggest that the Alpine fold‐thrust belt south of the foreland was also an important source of detritus to the deep‐water Molasse basin. We interpret evolving detrital zircon age distributions within the axial foredeep to reflect a progressive increase in longitudinal sediment input from the west (Freshwater Molasse) and/or southwest (Inntal fault zone) relative to transverse sediment input from the fold‐thrust belt to the south. We infer that these changes reflect a major reorganization of catchment boundaries and denudation rates in the Alpine Orogen that resulted in the Alpine foreland evolving to dominantly longitudinal sediment dispersal. This change was most notably marked by the development of a submarine canyon during deposition of the Upper Puchkirchen Formation that promoted sediment bypass eastward from Freshwater Molasse depozones to the Molasse basin deep‐water axial channel belt. The integration of 3D seismic‐reflection data with detrital zircon geochronology illustrates sediment dispersal patterns within a continental‐scale orogen, with implications for the relative role of longitudinal vs. transverse sediment delivery in peripheral foreland basins.