Neogene Deformation Research Articles

Geophysical evidence for the North Pie de Palo Lineament in the Precordillera

The Precordillera fold-thrust belt, situated within the Pampean flat-subduction segment (27°–33°S), is characterised by enigmatic transversal structures which extend and influence deformation patterns, the full extent of which is yet to be fully elucidated. The Northern Pie de Palo Lineament represents a key example, and has been proposed to play a pivotal role in the development and structural control of the Precordillera. In any case, this lineament has not been subjected to a comprehensive study, which has led to ongoing debate regarding its structural control, persistence, and morphology. This study was therefore focused on this structure, employing multiple geophysical methodologies, including aeromagnetic and gravimetric techniques. This approach enabled the first visualization of the full extension and fault zone of the North Pie de Palo Lineament, which crosses the entire Precordillera fold-thrust belt in a transverse direction. Consequently, it can be posited that this structure would have exerted a conditioning influence on the thermo-mechanical state of the Andean lithosphere, enabled the uplift of mafic bodies and thus influenced the Neogene deformation of the Precordillera fold and thrust belt. The confirmation and characterization of this major structure open new perspectives on the interaction of deep-seated transversal structures with fold belts during the evolution of the southern central Andes.

New constraints on the Late Miocene-Pliocene deformational and depositional evolution of the Eastern Cordillera and Sub-Andean Zone in Southern Peru

The deformation history of the Eastern Cordillera (EC) and Sub-Andean Zone (SAZ) of southern Peru is critical for understanding the roles that tectonics and climate played in the erosional exhumation of bedrock and the associated sediment flux delivered to the Amazon drainage basin. In this study, we report new field and subsurface data, apatite fission track (AFT) and (U–Th)/He thermochronological ages, U–Pb ages on detrital zircon grains, Sr–Nd isotopic compositions of fine sediments, which combined with previously published data, provide new constraints on the Neogene deformation and deposition history across the southern Peruvian EC and SAZ between 12° and 14°S. Late Miocene-Pliocene deformation is recorded by AFT and AHe ages in both the EC and SAZ and by growth strata geometry in the SAZ. This period is characterized by the development of piggy-back synclines and duplexes in the SAZ, overthrusting of the EC, and input of recycled sedimentary rocks of the SAZ and first cycle sediments from Triassic Plutonic rocks from the EC to the late Miocene-Pleistocene piggy-back syncline sediments. We report a transition from low-energy sand-dominated to high-energy conglomerate-dominated deposits in the Plio-Pleistocene marking an increase in sedimentation rates, indicating that the thrust wedge has continued to propagate. Our data agrees with that of previously published studies and indicate that the Late Miocene-Pliocene was a period of tectonic uplift and deformation in both the EC and SAZ.

Two stages of Late Cretaceous to Neogene deformation of the Huayingshan tectonic belt, eastern Sichuan Basin, SW China

Two stages of Late Cretaceous to Neogene deformation of the Huayingshan tectonic belt, eastern Sichuan Basin, SW China

Evolution of Miocene normal and dextral faulting in the lower Colorado River region near Blythe, California, USA

Abstract The evolution of strain in nascent continental plate boundaries commonly involves distributed deformation and transitions between different styles of deformation as the plate boundary matures. Distributed NW-striking faults, many with km-scale right-lateral separation, are prevalent near Blythe, California, and have been variably interpreted to have accommodated either Middle Miocene NE-SW extension as normal faults or Late Miocene to Pliocene dextral shear as strike-slip faults. However, with poor timing and kinematic constraints, it is unclear how these faults relate to known domains of Neogene deformation and the evolution of the Pacific–NorthAmerica plate boundary. We present kinematic data (n = 642 fault planes, n = 512 slickenlines) that demonstrate that these faults dominantly dip steeply northeast; ~96% of measured faults record normal, dextral, or oblique dextral-normal kinematics that likely reflect a gradational transition between normal and dextral oblique kinematic regimes. We constrain fault timing with 11.7 Ma and 7.0 Ma 40Ar/39Ar dates of rocks cut by faults, and laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of calcite mineralized during oblique dextral faulting that demonstrates fault slip at ca. 10–7 Ma and perhaps as late as ca. 4 Ma. This Late Miocene dextral oblique faulting is best compatible with a documented regional transition from Early to Middle Miocene NE-directed extension during detachment fault slip to subsequent NW-directed dextral shear. We estimate 11–38 km of cumulative dextral slip occurred across a 50-km-wide zone from the Palen to Riverside mountains, including up to 20 km of newly documented dextral shear that may partly alleviate the regional discrepancy of cumulative dextral shear along this part of the Late Miocene Pacific–North America plate boundary.

Extensional deformation of a shale‐dominated delta: Tarakan Basin, offshore Indonesia

AbstractDeformation on shale‐rich continental margins is commonly associated with thin‐skinned extension above mobile shales. Normal faulting and shale mobilization are widespread on such margins, being associated with and controlled by progradation and gravitational failure of deltaic sedimentary wedges. However, due to uncertainties in seismically imaging mobile shales, our understanding of problems like how base mobile‐shale controls deformation, and the shape, size, and distribution of shale structures remains poorly understood. Here, we use 3D seismic reflection data from the platform region of the Tarakan Basin, offshore eastern Indonesia to investigate the temporal and spatial evolution of thin‐skinned deformation of the Neogene sedimentary section. Our detailed seismic interpretation reveals up to 74 km long, concave‐ and convex‐into‐the‐basin normal faults, dipping both basinward (eastwards) and locally landward (westwards), which detach downwards on a basal mobile shale (Early‐Middle Miocene). The base of the mobile‐shale unit dips gently (<17°) seaward, although older (Eocene‐Early Miocene), rift‐related normal faults originate local structural highs deforming the base of mobile shales. Our isochore (thickness map) analysis shows that supra‐shale normal faulting commenced in the Middle Miocene and was accompanied by the formation of hanging‐wall rollover folds and associated crestal grabens, with the subsequent along‐ and across strike migration of the deformation related to the nucleation, lateral linkage and reactivation of individual fault systems. Updip growth normal faulting was also accompanied by the downslope flow of mobile shale, accompanied by parallel and perpendicular variations of the differential loading in the delta system, and local contraction and mobile‐shale upbuilding, resulting in the growth of large, margin‐parallel shale anticlines further downdip. The growth faults and anticlines are locally overlain by up to 5 km tall mud pipes and volcanoes. We suggest that variations in the rate of sedimentary loading, mobile‐shale flow, fault growth and gravitational failure of the delta system above a seaward‐dipping, but locally rugose base mobile‐shale surface, controlled Neogene deformation in the Tarakan Basin. We also demonstrate how variations in the trend and dip of the base mobile‐shale surface influence the position, timing of formation and evolution of supra‐shale normal faults and their associated depocentres along shale‐rich, deltaic margins.

Mesozoic–Cenozoic multistage tectonic evolution of the Pamir: Detrital fission‐track constraints from the Tajik Basin

AbstractKnowledge of the tectonic history of the Pamir contributes to our understanding of both the evolution of collisional orogenic belts as well as factors controlling Central Asian aridification. It is, however, not easy to decipher the Mesozoic–Cenozoic tectonics of the Pamir due to extensive Neogene deformation in an orogen that remains largely understudied. This study reports detrital apatite and zircon fission‐track (FT) ages from both the eastern Tajik Basin sedimentary rocks and Pamir modern river sands. These FT data, supported by vitrinite reflectance and zircon and apatite U–Pb double dating, suggest that the majority of the FT ages are unreset and record exhumation stages of the Pamir, which has served as the source terrane of the Tajik Basin since the Cretaceous. Furthermore, we combine the new data with a compilation of published detrital apatite and zircon FT data from both the Tajik Basin sedimentary rocks and Pamir modern river sands, to explore the Mesozoic–Cenozoic tectonic history of Pamir. Deconvolved FT Peak Ages document two major Mesozoic exhumation events associated with the Late Triassic–Early Jurassic Cimmerian orogeny that reflects accretion of the Pamir terranes, as well as the Early–early Late Cretaceous deformation associated with the northward subduction of the Neo‐Tethys Ocean beneath Pamir. The compiled data also show significant Late Eocene–Neogene exhumation associated with the ongoing formation of the Pamir, which peaks at ca. 36, 25, 14 and 7 Ma.

Palaeogeographic evolution of Zealandia: mid-Cretaceous to present

ABSTRACT We present a suite of 15 palaeogeographic maps illustrating the geological evolution of the entirety of Zealandia, from mid-Cretaceous to present, highlighting major tectonic phases, from initial Gondwana rifting through to development of the Neogene plate boundary. They illustrate palaeobathymetric and palaeofacies interpretations along with supporting geological datasets and a synthesis of regional tectonics. The maps are underpinned by a geologically-constrained and structurally-based rigid retro-deformation block model. This model, tied to the global plate circuit, is relatively simple for the main regions of Northern and Southern Zealandia, but breaks central Zealandia into numerous fault-bounded blocks, reflecting complex Neogene deformation associated with the modern plate boundary. Production of maps using GPlates and GIS allows for simple alteration or refinement of the block model and reconstruction of any geological dataset at any time. Reconstructions are within a palaeomagnetic reference frame, allowing assessment of palaeo-latitude, critical for palaeo-climatic and palaeo-biogeographic studies.

The significant meaning of biodegradation to the petroleum system of the Seram Basin, eastern Indonesia: evaluation on the basis of physio-chemical composition variation of Seram oils

It has been widely accepted since the 1980s that Seram crude oils belong to one family that originated from the Triassic carbonate source rock. Even though these oils share similar nature and origin, they exhibit wide physio-chemical composition variations in Seram Basin. Moreover, this variation is also noted within a similar oil field. Hydrocarbon alteration, especially biodegradation, a process of hydrocarbon destruction by microbial activities, has been attributed to this variation. However, the degree and extension of biodegradation in the Seram Basin are still poorly understood. Therefore, crude oils accumulated in main reservoirs, the Pre-Tertiary Manusela Carbonate and the Pliocene Fufa Clastic reservoirs, retrieved from Lofin, Oseil, Nief, and Bula Fields, are comprehensively studied. In addition, several oil seep samples were also utilized for this study together with crude oil geochemistry data compiled from previous publications. The occurrence of biodegradation is also validated with the geological conditions that include resevoir temperatures and salinities. Based on the geochemical signatures, there is a wide range of biodegradation degrees within the Seram Basin with the biodegradation degree tends to increase and more destructive to Bula Field which is situated in the northern part of the basin. The biodegradation pattern is linked to hydrocarbon generation and migration history. The Neogene deformation in eastern Indonesia is interpreted to be responsible for the different biodegradation process within Seram Basin. This process should be well understood and not be neglected during petroleum exploration, especially in eastern Indonesia. This study shows that such simple process has a deep meaning on the petroleum system history, especially the hydrocarbon preservation in the reservoir.

Neogene Kinematics of the Potwar Plateau and the Salt Range, NW Himalayan Front: A Paleostress Inversion and AMS study

ABSTRACT We provide new kinematic data from the Potwar Plateau (Pakistan) to evaluate the tectonic evolution of the region during the Neogene. The plateau is bound by two major strike-slip faults in the west and the east, accommodating its southwards translation. We have recognized two Neogene deformation phases in the plateau, based on paleostress inversion and Anisotropy of Magnetic Susceptibility (AMS) tensors. The first phase lasted until the early Pliocene and was characterized by vertical minor stress and N-S compression, implying thrust tectonics. The second deformation phase is characterized by a near-vertical intermediate principal stress and near-horizontal major and minor stresses, interpreted to be associated with strike-slip tectonics since the late Pliocene. Kint vectors from 21 sites are relatively compatible with the major principal stress orientations (σ1) and indicate two distinct domains. This is possibly because Kmin orientations are related to compaction, whereas Kint orientations were always parallel to tectonic shortening and hence compression direction during both strike-slip (post-late Pliocene) and thrusting (pre-late Pliocene) phases. These phases are characterized by swapping of (σ2) and (σ3) orientations while (σ1) maintained its orientation. The most prominent change occurs at the western part of the Potwar Plateau, where major principal stress directions (σ1) and Kint axes fan out south-westwards. The eastern domain is dominated by NE-SW trending folds and thrust faults, which are absent in the western domain. These structural features are interpreted to be the result of the distribution of deposits of the Neoproterozoic Salt Range Formation as a substratum below the Potwar Plateau. The Salt Range Formation is very thick and widespread in the west area and almost absent in the east. This factor led to unconstrained southwards gliding of the Potwar Plateau over the salt deposits in the west as opposed to frictional sliding and substantial internal deformation in the east.

Spatio-temporal variation of the strain field in the southern Central Andes broken-foreland (27°30′S) during the Late Cenozoic

We present an integrated structural and Anisotropy of Magnetic Susceptibility (AMS) study focused on the characterization of the spatio-temporal variation of the strain field during the main Neogene deformation, of the Argentine Precordillera and the northern Sierras Pampeanas, immediately to the south of the Puna plateau (27°30′S). The AMS from 43 sites and fault-slip data analysis from mesoscale faults (n = 540) were carried out in Lower Miocene to Middle Pliocene sedimentary and volcaniclastic rocks. The AMS results show moderate values of anisotropy degree near to deformation zones, and low and high values of bulk susceptibility. The most predominant magnetic fabric is sedimentary type I and II, with a weak magnetic lineation. In areas where the rocks are deformed, the incipient magnetic lineation are subparallel to the regional structural trend and present a main N–S orientation in the Precordillera and Fiambalá basin, while in the Sierras Pampeanas they are mostly NE-oriented. Combining these results with kinematic analysis from fault-slip data, we identify, in the Precordillera and Fiambalá basin areas, a contractional event with E-W main direction, from ~23 Ma to 5 Ma, mostly active from the onset of deposition of Neogene sequences. During this period, in the NW Sierras Pampeanas, the contraction directions follow a NW orientation. The onset of N–S to NNW contraction, mostly recognized in rocks younger than 5 Ma, exposed in the northern areas of Precordillera and Sierra Pampeanas, documents a change of the strain field during the Early-to-Middle Pliocene, associated with a shift in the contractional direction from E-W to N–S. We relate the change to the rapid uplift of the southern Puna, generating a juxtaposition of an area under N–S extension, affecting the topographically-higher Puna, with the other area under N–S contraction in the adjacent Precordillera and Sierras Pampeanas. We associate these two events as part of the evolution of this segment of the Andes, where the broken foreland setting is active during this time. By combining the AMS and kinematic analysis results, we obtain a timing for the spatio-temporal change of contraction directions, which allows us to compare both the broken-foreland and foreland basins to understand spatio-temporal strain variations.

K-Ar fault gouge dating of Neogene thrusting: The case of the siliciclastic deposits of the Trasimeno Tectonic Wedge (Northern Apennines, Italy)

The Northern Apennines (NA) are a characteristic example of foreland fold-and-thrust belt progressively migrating towards its foreland. Their tectonic evolution has been quite tightly constrained in time by microfossil biostratigraphy applied to syn-orogenic deposits within foreland basins. This makes the NA well suited to test the reliability of K-Ar illite dating of Neogene deformation affecting siliciclastic sequences. We sampled two top-to-the-ENE thrusts, whose well defined cores are defined by scaly gouge formed at the expense of the pelitic component of the host rock. X-ray diffraction (XRD) and K-Ar isotopic analysis of multiple grain-size fractions of the gouge, allowed us to discriminate between syn-kinematic and inherited illite crystals in the fault rocks. Illite age analysis (IAA) constrains fault slip along the thrusts to 15.2 ± 7.6 Ma and 15.4 ± 16.6 Ma. The results, in spite of their analytical uncertainty, are fully consistent with the local evolution of the NA as constrained by the independent biostratigraphic studies and confirm the general suitability of this geochronological approach to Neogene deformation.

Andean Mountain Building and Foreland Basin Evolution During Thin‐ and Thick‐Skinned Neogene Deformation (32–33°S)

AbstractThe southern Central Andes recorded retroarc shortening, basin evolution, and magmatic arc migration during Neogene changes in subduction. At 31–33°S, above the modern flat‐slab segment, spatial and temporal linkages between thin‐ and thick‐skinned foreland shortening, basement‐involved exhumation of the main Cordillera, and lower‐crustal hinterland thickening remain poorly resolved. We integrate new geochronological and thermochronological data for thrust sheets and Neogene foreland basin fill with structural, sedimentological, and passive seismic results to reconstruct the exhumation history and evaluate potential geometric linkages across structural domains. 40Ar/39Ar ages for volcanic horizons and zircon U‐Pb ages for synorogenic clastic deposits in the Manantiales Basin constrain the minimum duration of synorogenic sedimentation to ~22–14 Ma. Detrital zircon age distributions record sequential unroofing of hinterland thrust sheets until ~15 Ma, followed by eastward (cratonward) advance of the deformation front, shutoff of western sediment sources, and a shift from fluvial to alluvial fan deposition at ~14 Ma. Apatite (U‐Th)/He cooling ages confirm rapid exhumation of basement‐involved structural blocks and basin partitioning by ~14–5 Ma, consistent with the timing of the Manantiales facies and provenance shifts and a coeval (~12–9 Ma) pulse of thin‐skinned shortening and exhumation previously identified in the eastern foreland. Late Miocene–Pliocene (~8–2 Ma) cooling ages along the Chile‐Argentina border point to hinterland uplift during the latest stage of Andean orogenesis. Finally, geophysical constraints on crustal architecture and low‐temperature thermochronometry results are compatible with a hybrid thin‐ and thick‐skinned décollement spanning retroarc domains.

LATE NEOGENE DEFORMATION OF ROCK SUCCESSIONS AT RENAH GAJAH MATI I REGION, SELUMA REGENCY IN BENGKULU

Lack of work focusing on deformation mechanism has been undertaken in the Late Tertiary sequence during Late Neogene time at the Renah Gajah Mati I region in Bengkulu basin. The present study was aimed at reconstructing tectonic deformation occurring within the basin during the Late Neogene, employing balancing and restoring techniques, kinematic and dynamic analyses. The Late Neogene deformation was mainly controlled by compression, which has resulted in folding and thrusting. Hence, the rock sections underwent shortening that varied from 1.42-1.83 km or 0.75%-0.78% with the estimated rate of deformation 0.12-0.15 mm/year. Two types of tectonic structures developed within the region, fault propagation folds and trishear faults. The brittle deformation extended sequentially in the direction of tectonic transport, resulting in a series of faults. The generated faults constitute imbricate fans with a relatively closely-spaced thrust system. The array of thrusts is apparently associated with folds that strike NW-SE, implying the geometry of fault-linked folding. The hanging wall anticlines are generally asymmetric overturned folds, indicating a shallow ramping fault with a high shear pattern. In regional context, the general strike of structures within the study area appears relatively parallel to the NW-SE trending Barisan orogen. This feature suggests that tectonic transport responsible for structuring was likely at the NE- SW direction.

Late neogen deformation of rock successions at Renah Gajah Mati I Region Seluma Regency in Bengkulu

Studies on tectonic deformation of the Late Tertiary sequence during Late Neogene time has been carried out at the Renah Gajah Mati I region using balancing and restoring techniques, kinematic and dynamic analyses. The Late Neogene deformation was mainly controlled by compression, which has resulted in folding and thrusting. Hence, the rock sections underwent shortening that varied from 1.42-1.83 km or 0.75%-0.78% with the estimated rate of deformation 0.12-0.15 mm/year. Two types of tectonic structures developed within the region, fault propagation folds and trishear faults. The brittle deformation extended sequentially in the direction of tectonic transport, resulting in a series of faults. The generated faults constitute imbricate fans with a relatively closely-spaced thrust system. The array of thrusts is apparently associated with folds that strike NW-SE, implying the geometry of fault-linked folding. The hanging wall anticlines are generally asymmetric overturned folds, indicating a shallow ramping fault with a high shear pattern. In regional context, the general strike of structures within the study area appears relatively parallel to the NW-SE trending Barisan orogen. This feature suggests that tectonic transport was likely at the NE-SW direction.

Comparative Evaluation of 1D, 2.5D and 3D Inversions for Resolving Tectonic Elements in Floodplains and Near-Surface Inverted Sedimentary Basins

This study reports the results of a comparative evaluation of 1D, 2.5D and 3D AEM inversions for resolving hydrostratigraphy and structural elements in two contrasting settings: unconsolidated Quaternary floodplain sediments affected by Neogene deformation; and a tectonically inverted Palaeozoic sedimentary basin.Previous studies have demonstrated the importance of airborne electromagnetic (AEM) data optimization to ensure that key elements of the hydrogeological system, including geological faults, are appropriately represented in inversion models. In the inverted sedimentary basin study, 1D inversions of AEM data indicated greater structural complexity than previously known. Initially, a suite of equivalent 1D inversion models produced very similar inversion model results. However, 2.5D inversions produced a disparity in solutions in key locations. To resolve these differences, 3D AEM inversion methods have been trialled. In the second study (floodplain setting), 3D inversions have helped resolve the geometry of hydrostratigraphic units and tectonic elements (folds and faults). In both study areas, independent validation of inversion results has involved an inter-disciplinary approach incorporating a range of borehole and ground geophysics techniques (e.g. passive seismic and Ground Magnetic Resonance (GMR)), tectonic mapping and analysis, hydrochemistry and drilling.In summary, comparative evaluation of 1D, 2.5D, and 3D AEM inversions in two contrasting settings demonstrates the importance of optimizing inversion procedures, taking into consideration all available geological, hydrogeological and tectonic data. The benefits of using 2.5D and/or 3D inversion procedures are particularly evident in areas of structural complexity. Confidence in 3D inversions is maximised when all elements of the system response are modelled appropriately.

Structure and evolution of the Ban Pong Basin, Chiang Mai Province, Thailand

The Ban Pong Basin (BPB) is a small intermontane basin of Neogene age on the western margin of the Chiang Mai Basin in northern Thailand. The BPB was discovered in 2012 because of new quarrying activity. The basin complex formed in the hanging wall of a major Cenozoic low-angle normal fault (LANF) called the Inthanon Detachment, and provides a unique record of the Neogene deformation related to the detachment. The BPB’s preservation is probably due to its location in a synform within the rising Western Ranges metamorphic complex, which forms the Suthep-Inthanon mountain range. Initially, extensional faults in the BPB were oriented ∼N-S but then rotated to NNW-SSE, NW-SE, and ENE-WSW to NE-SW directions, which we interpret as arising due to local stress rotation related to the adjacent rising metamorphic complex. Folds, thrusts, and inverted normal faults both within Neogene sediments of the Mae Rim Formation and adjacent Palaeozoic metasedimentary rocks indicate a phase of compression that affected the basin late in its history (probably latest Miocene-Pliocene based on the regional timing of inversion). Complete Bouguer anomaly interpretations of 235 reduced gravity stations reveal two en echelon sub-basins, bounded by gravity highs related to shallow-lying Palaeozoic rocks and underlying high-grade metamorphic basement rocks. Two gravity-density cross-section models indicate the basin fill comprises up to 250 m of weakly lithified syn-rift sediments. The absence of a classic half graben morphology is probably related to inversion and erosion that significantly modified the extensional basin geometry and original thickness.

Evolution of the Karebas Fault System and adjacent folds, central Zagros fold-and-thrust belt, Iran: Role of pre-existing halokinesis (salt structures and minibasins) and detachment levels

In the central part of the Zagros fold-and-thrust belt of Iran, several diapirs of the Latest Precambrian–Early Cambrian Hormuz Salt locally decorate the surface exposures of a series of N–S to NNW–SSE trending right-lateral tear fault systems. The Karebas Fault System (KBFS), as one of these fault systems, is associated with five salt diapirs. There are also several NW–SE trending anticlines, which are either cross-cut by the fault system or terminated against it and the adjacent salt diapirs. The Neogene Zagros folds are clearly affected by the surface expression of the Karebas Fault System, suggesting that the fault system is coeval with or post-dates the Neogene deformation. On the contrary, halokinesis as old as at least Late Jurassic is documented by near-diapir stratigraphic exposures, indicating pre-orogenic existence of the diapirs. Although the lack of older rock outcrops precludes tracking the pre-Jurassic records of diapirism, the geometry of strata, which flank these diapirs, indicates long-term pre-folding salt rise driven by downbuilding of lateral minibasins and progressive draping of sedimentary layers over the flanks of the rising diapirs. Therefore, presence of old salt structures along the young (Neogene) tear fault system suggests an important role played by the presence of early-formed salt structures in inducing later strike-slip deformation along zones of preferential weakness, which was prepared by the pre-folding salt structures and thinner sedimentary pile overlying them. Salt diapirs and related changes in stratigraphic thicknesses (i.e. minibasins) also effectively grappled with the process of folding. Detachment folding is typically the main structural style across the area, and was mainly developed above the Hormuz Salt as the basal décollement and partly by involvement of the intermediate detachment levels. However, preferential weakness and squeezing of the diapirs on one hand and greater strength of the minibasins on the other hand gave rise to further complexities of deformation during shortening. Such first-order controls could led to perturbations, at the scale of diapirs and minibasins, in the stress pattern as the southwestward-advancing front of the Zagros deformation migrated across the stratigraphic section and the salt structures. It occurred because strain is localized at the diapirs and squeezes them whereas tends to avoid folding the thick, and hence stronger, minibasins into anticlines. In such a context, the localization and the longitudinal propagation of the folds in the cover sequence could be remarkably influenced and irregular. The consequence was variable fold geometries (location and dimension) and fold-axes rotations with respect to the diapirs and minibasins.

Understanding the geologic evolution of Northern Tibetan Plateau with multiple thermochronometers

The early onset of deformation following the India-Asia collision, Neogene expanse of uplift, and complex systems that comprise strike-slip faults, thrust faults, and intermontane basins characterize the Cenozoic tectonism of Northern Tibetan Plateau and raise two prominent questions in orogenic geodynamics: 1) What mechanism(s) control(s) the transfer of stress related to the India-Asia collision across the distance of >2000km; and 2) Why the development of high topography was delayed in the Northern Tibetan Plateau and what does it reveal about how the internal forces and external boundary conditions evolved. To address these two questions, we reconstruct a holistic spatial-temporal deformation history of the Northern Tibetan Plateau by using a range of thermochronometers, with closure temperature spanning from 350°C to ~60–70°C. This multi-thermochronometer study reveals three stages of faulting related cooling, in the early Cretaceous, in Paleocene-Eocene and in middle-late Miocene. We observe that Paleocene-Eocene deformation was spatially restricted and mostly occurred on reactivated Cretaceous structures, indicating a control of pre-existing weakness on early Cenozoic deformation. Extensive Neogene deformation contrasts with restricted Paleocene-Eocene deformation and relatively quiescent shortening during the Oligocene-early Miocene, which implies a change in the regional tectonics regime. Global plate reconstructions show that this tectonic reorganization is coeval with an increase in Pacific-Asia plate convergence rates. We argue that this change in regional tectonics is a result of increasing constrictive environment of the eastern plate boundary, which changed the behavior of the Altyn Tagh fault—the boundary fault of Northern Tibetan Plateau, causing it to change from feeding slip into structures out of the plateau to feeding slip into structures at plateau margins.

Cretaceous to present-day tectonic reconstructions of Zealandia

Reconstructions of the past relative positions of northern and southern Zealandia provide important constraints on the orientation and amount of strain accumulated between rigid plates within the Australia–Pacific plate tectonic circuit. This configuration of plates ultimately determines how, where and when sedimentary basins formed during and since continental breakup along the eastern margin of Gondwana. Although the first-order geometry of Zealandia is well established, uncertainty remains regarding plate motions through the latest Cretaceous to Eocene. Recent reconstructions are, in some cases, inconsistent with geological observations at key time intervals, highlighting uncertainties inherent in plate reconstructions for the south-west Pacific. Building on previous tectonic reconstructions and incorporating published seafloor magnetic interpretations, paleomagnetic observations and geological constraints (e.g. terrane geometry and distribution), we developed a tectonic framework to reconstruct Zealandia back through to the latest Cretaceous. Using GPlates, we use a simple double-hinge slat concept to describe Neogene deformation within the New Zealand plate boundary zone, while the geometry of northern and southern Zealandia during the Eocene is modified from recently published models based on geologic considerations. This study ultimately highlights the need for integrated studies of the Zealandia plate circuit.

Miocene tectonic history of the Central Tauride intramontane basins, and the paleogeographic evolution of the Central Anatolian Plateau

Marine Lower-Upper Miocene deposits uplifted to >2km elevation in the Tauride mountains of southern Turkey are taken as evidence for the rise of a nascent plateau. The dynamic causes of this uplift are debated, but generally thought to be a regional dynamic topographic effect of slab motions or slab break-off. Immediately adjacent to the high Tauride mountains lie the Central Tauride Intramontane Basins, which consist of Miocene and younger fluvio-lacustrine basins, at much lower elevations than the highly uplifted marine Miocene rocks. These basins include the previously analyzed Altınapa and Yalvaç basins, as well as the until now undescribed Ilgın Basin.In this paper, we aim to constrain the paleogeography of the Central Tauride Intramontane Basins and determine the role of the tectonics driving the formation of the high Miocene topography in southern Turkey. Therefore, we provide new data on the stratigraphy, sedimentology and structure of the continental Ilgın Basin. We provide an 40Ar/39Ar age of 11.61±0.05Ma for pumice deposits in the stratigraphy. We provide paleostress inversion analysis based on growth faults showing that the basin formed during multi-directional extension, with NE-SW to E-W dominating over subordinate NS extension. We conclude that major, still-active normal faults like the Akşehir Fault also controlled Miocene Ilgın basin formation, with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocenter. The Ilgın Basin was a local depocenter, but it may have connected with the adjacent Altınapa Basin during high lake levels in late Serravallian time. The Ilgın Basin and the other continental basins provide key constraints on the paleogeography and tectonic history of the region. These continental basins were likely close to the paleo-coastline during the Late Miocene after which there must have been major differential uplift of the Taurides. We suggest that the extension we documented in the Central Tauride intramontane basins are in part responsible for the major topography that characterizes the Central Taurides today. The causes of extension remain engmatic, but we suggest that the tomographically imaged Antalya Slab may have caused the contemporaneous formation of NE-SW trending syn-contractional basins in the west and NW-SE trending Central Tauride intramontane basins in the east by slab retreat. Our study highlights that the Neogene deformation history, and perhabs even active tectonics, may be strongly affected by complex slab geometry in SW Turkey, and that crustal deformation plays an important role in generating the Miocene Tauride topography. The role of this crustal deformation needs to be taken into account in attempts to explain the ride of the Taurides and the evolution of the Anatolian Plateau.