Stable isotope measurements (O, C, Sr), microthermometry and salinity measurements of fluid inclusions from different fracture populations in several anticlines of the Sevier-Laramide Bighorn basin (Wyoming, USA) were used to unravel the paleohydrological evolution. New data on the microstructural setting were used to complement previous studies and refine the fracture sequence at basin scale. The latter provides the framework and timing of fluid migration events across the basin during the Sevier and Laramide orogenic phases. Since the Sevier tectonic loading of the foreland basin until its later involvement into the Laramide thick-skinned orogeny, three main fracture sets (out of seven) were found to have efficiently enhanced the hydraulic permeability of the sedimentary cover rocks. These pulses of fluid are attested by calcite crystals precipitated in veins from hydrothermal (T>120°) radiogenic fluids derived from Cretaceous meteoric fluids that interacted with the Precambrian basement rocks. Between these events, vein calcite precipitated from formational fluids at chemical and thermal equilibrium with surrounding environment. At basin-scale, the earliest hydrothermal pulse is documented in the western part of the basin during forebulge flexuring and the second one is documented in basement-cored folds during folding. In addition to this East/West diachronic opening of the cover rocks to hydrothermal pulses likely controlled by the tectonic style, a decrease in ^87/86Sr values from West to East suggests a crustal-scale partially squeegee-type eastward fluid migration in both basement and cover rocks since the early phase of the Sevier contraction. The interpretation of paleofluid system at basin-scale also implies that joints developed under an extensional stress regime are better vertical drains than joints developed under strike-slip regime and enabled migration of basement-derived hydrothermal fluids.

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This paper reports a stratigraphic and structural analysis of the Neogene-Quaternary Valdelsa Basin (Central Italy), filled with up to 1000 m of uppermost Miocene to lower Pleistocene strata. The succession is subdivided into seven unconformity-bounded stratigraphic units (synthems, or large-scale depositional sequences) that include fluvio-deltaic and shallow-marine deposits. Structures related to basin shoulders and internal boundaries controlled the Neogene location and geometry of different depocentres. During the Tortonian-Messinian, a buried NE-trending high related to regional, basin-transverse lineaments separated two adjacent sub-basins. During the lower Pliocene, compressional displacement along NW-trending, thrust-related highs controlled the distribution of depocentres and dispersal of sediment. Extensional tectonics, although previously considered the dominant deformation style affecting the rear of the Northern Apennines since the late Miocene, is no longer considered a dominant control on tectono-sedimentary development of the Valdelsa basin. Instead, the Valdelsa Basin shares features with continental hinterland basins of orogenic belts where compression, extension, and transcurrent stress fields determine a complex spatial and temporal record of accommodation and sediment supply. In the Valdelsa Basin tectonics and eustatic sea-level fluctuations were dominant in forcing the deposition of sedimentary cycles at several scales. Zanclean and Gelasian large-scale depositional sequences were mainly controlled by crustal shortening, whereas a eustatic signal was preferentially recorded during the Piacenzian. Smaller scale depositional sequences, common to most synthems, were controlled by orbitally forced glacio-eustatic cycles.

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Stratigraphic data from petroleum wells and seismic reflection analysis reveal two distinct episodes of subsidence in the southern New Caledonia Trough and deep-water Taranaki Basin. Tectonic subsidence of ~2.5 km was related to Cretaceous rift faulting and post-rift thermal subsidence, and ~1.5 km of anomalous passive tectonic subsidence occurred during Cenozoic time. Pure-shear stretching by factors of up to 2 are estimated for the first phase of subsidence from the exponential decay of post-rift subsidence. The second subsidence event occured ~40 Ma after rifting ceased, and was not associated with faulting in the upper crust. Eocene subsidence patterns indicate northward tilting of the basin, followed by rapid regional subsidence during the Oligocene and Early Miocene. The resulting basin is 300- 500 km wide and over 2000 km long, includes part of Taranaki Basin, and is not easily explained by any classic model of lithosphere deformation or cooling. The spatial scale of the basin, paucity of Cenozoic crustal faulting, and magnitudes of subsidence suggest a regional process that acted from below, probably originating within the upper mantle. This process was likely associated with inception of nearby Australia-Pacific plate convergence, which ultimately formed the Tonga-Kermadec subduction zone. Our study demonstrates that shallow-water environments persisted for longer and their associated sedimentary sequences are hence thicker than would be predicted by any rift basin model that produces such large values of subsidence and an equivalent water depth. We suggest that convective processes within the upper mantle can influence the sedimentary facies distribution and thermal architecture of deep-water basins, and that not all deep-water basins are simply the evolved products of the same processes that produce shallow-water sedimentary basins. This may be particularly true during the inception of subduction zones, and we suggest the term ‘prearc’ basin to describe this tectonic setting.

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The structure and tectonic evolution of an evaporite basin are investigated in this case study which combines the interpretation of magnetic data with the more commonly applied seismic reflection and gravity methods. The Maritimes Basin contains up to 18 km of Upper Paleozoic sedimentary rocks resting on the basement of the Acadian orogeny. Carboniferous rocks are intensely deformed to the southeast of the Magdalen Islands as a result of deformation of evaporites of the Viséan Windsor Group. Short-wavelength (< 5 km) magnetic lineations define NNE- and ENE-trending linear belts, coincident with the mapped pattern of salt structures. Magnetic models show that these lineations can be explained by the infill of subsidence troughs by high-susceptibility sediment and/or the presence of basaltic rocks, similar to those uplifted and exposed on the Magdalen Islands. Additional shallow, magnetic sources are interpreted to result from alteration mineralisation in salt-impregnated, iron-rich sedimentary rocks, brecciated during salt mobilization. Magnetic susceptibility measurements of samples from the Pugwash mine confirm the presence of higher susceptibility carnallite-rich veins within salt units. Salt tectonism and basin development were influenced by the structure of the base group, the deepest regionally continuous seismic reflections (~ 5-11 km), associated with an unconformity at the base of the Windsor Group, sampled at the Cap Rouge well. Salt structural evolution, formation of the magnetic lineations, and geometry of the base group are associated with regional dextral transpression during basin development (late Carboniferous) and/or Alleghanian Orogeny (late Carboniferous to Permian). In this and similar studies, the effective use of magnetics is dependant upon the presence of rocks of high magnetic susceptibility in contrast with the low-susceptibility salt bodies. In the absence of high-susceptibility rocks, magnetic lows over the salt structures may be modelled, similar to commonly applied gravity techniques, to derive the internal structure and geometry.

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The recent paper by Gołędowski et al. (2012) is a contribution to the ongoing debate regarding the possible processes involved in the geological evolution of the North Sea basin and adjacent hinterlands during the Cenozoic.

Their major conclusions state

1. That the prominent seismic feature called the “mid-Miocene unconformity” (MMU) is a diachroneous surface in the North Sea basin and forms a regional hiatus.
2. That sediment flux from western Scandinavia was primarily controlled by climate and vegetation cover from the Late Eocene and onwards.

We believe, however, that regarding to the eastern North Sea basin, which was the depocenter for sediments sourced from southwestern Scandinavia, these conclusions are not supported by the geological record;

• The so-called “mid-Miocene unconformity” is not a regional hiatus in the Danish and Norwegian sectors of the North Sea basin but represents a distinct shift from prograding delta/slope systems to deposition of deeper marine hemipelagic mud and thus provides a distinct seismic marker horizon. However, detailed studies show that there is a continuous sedimentation dominated by glacony-rich mud where a c. 3 m thick mudlayer spans several millions years and thus are below seismic resolution. Consequently, seismic stratigraphy is not applicable for this condensed section.
• Warm climate and dense vegetation cover in southern Scandinavia during the mid-Miocene Climatic Optimum was not able to hinder the progradation of a major siliciclastic wedge from Scandinavia into the North Sea basin.
• The distinct temperature decrease in the Serravallian does not correlate with the afore-mentioned progradation, but on the contrary, correlate to the culmination of a major flooding event and deposition of a condensed succession of marine glaucony-rich clay.

© 2013 The Authors. Basin Research © 2013 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists

The Upper Muschelkalk sedimentary record constitutes a major transgressive pulse of northeastern Iberia during the Ladinian. This record is arranged in two transgressive-regressive (T-R) sequences formed by two stepped microbial-dominated carbonate ramp systems where accommodation was mainly controlled by extensional faults. This study seeks to gain new insights into how the evolution of syn-rift subsidence controls the creation of accommodation space, the depositional styles and, especially, the palaeogeographical domains where specific microbialites developed (thrombolites and stromatolites). Thrombolite bodies (ca. 40m thick) display two types of architecture, biostromal and mud-mounded, whereas stromatolite bodies (at least 7m thick) show stratiform and domed, head-shaped morphologies. Domed and mounded forms are usually developed during stages of increasing accommodation rates, whereas stratiform and biostromal morphologies tend to grow in association with periods of low accommodation rates. A sea-level fall of at least 50 metres occurred at the end of the Early Ladinian leaving the platform subaerially exposed. As a result, a prominent karst with significant erosional incisions and profuse collapse breccia fillings was formed in the inner and middle ramp settings. The resultant subaerial unconformity bounds T-R sequences 1 and 2. Subsidence curves display two stages of rapid/decelerated total subsidence, constituting two discrete rift/post-rift pulses in the large Triassic rifting period: i) Buntsandstein - Middle Muschelkalk, and ii) Late Muschelkalk- Imon Formation (Rhaetian). The second pulse is characterized by a rapid syn-rift subsidence during the Late Muschelkalk, and a decelerated post-rift subsidence throughout the deposition of Keuper facies and Imon Formation. The Late Muschelkalk rapid syn-rift pulse of total subsidence produces gains in accommodation, which controls the development of the stromatolites and thrombolites (biostromes and mud-mounds).

© 2013 The Authors. Basin Research © 2013 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists

Depositional models of ancient lakes in thin-skinned retroarc foreland basins rarely benefit from appropriate Quaternary analogs. To address this, we present new stratigraphic, sedimentological, and geochemical analyses of four radiocarbon-dated sediment cores from the Pozuelos Basin (PB; northwest Argentina) that capture the evolution of this low-accommodation Puna basin over the past ˜43 cal kyr. Strata from the PB are interpreted as accumulations of a highly variable, underfilled lake system represented by lake margin/littoral, profundal, palustrine, saline lake, and playa facies associations. The vertical stacking of facies is asymmetric, with transgressive and thin organic-rich highstand deposits underlying thicker, organic-poor regressive deposits. The major controls on depositional architecture and basin paleogeography are tectonics and climate. Accommodation space was derived from piggyback basin forming flexural subsidence and Miocene-Quaternary normal faulting associated with incorporation of the basin into the Andean hinterland. Sediment and water supply was modulated by variability in the South American Summer Monsoon, and perennial lake deposits correlate in time with several well-known late Pleistocene wet periods on the Altiplano/Puna plateau. Our results shed new light on lake expansion-contraction dynamics in the PB in particular and provide a deeper understanding of Puna basin lakes in general.

© 2013 The Authors. Basin Research © 2013 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists

Despite abundant data on the early evolution of the Central Alps, the latest stage exhumation history, potentially related to relief formation, is still poorly constrained. We aim for a better understanding of the relation between glaciation, erosion and sediment deposition. Addressing both topics, we analysed late Pliocene to recent deposits from the Upper Rhine Graben and two modern river sands by apatite fission-track and (U-Th-Sm)/He thermochronology. From the observed age patterns we extracted the sediment provenance and paleo-erosion history of the Alpine-derived detritus. Due to their pollen and fossil record, the Rhine Graben deposits also provide information on climatic evolution, so that the erosion history can be related to glacial evolution during the Plio-Pleistocene. Our data show that Rhine Graben deposits were derived from Variscan basement, Hegau volcanics, Swiss Molasse Basin, and the Central Alps. The relations between glaciation, Alpine erosion, and thermochronological age signals in sedimentary rocks are more complex than assumed. The first Alpine glaciation during the early Pleistocene did not disturb the long-term exhumational equilibrium of the Alps. Recent findings indicate that main Alpine glaciation occurred at ~1 Ma. If true, then main Alpine glaciation was coeval with an apparent decrease of hinterland erosion rates, contrary to the expected trend. We suggest that glaciers effectively sealed the landscape, thus reducing the surface exposed to erosion and shifting the area of main erosion north toward the Molasse basin, causing sediment recycling. At around 0.4 Ma, erosion rates increased again, which seems to be a delayed response to main glaciation. The present-day erosion regime seems to be dominated by mass-wasting processes. Generally, glacial erosion rates did not exceed the pre-glacial long-term erosion rates of the Central Alps.

© 2013 The Authors. Basin Research © 2013 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists

Salt rim synclines contain important hydrocarbon and coal resources in central Europe. The Schöningen salt rim syncline is filled with >300 m of Early to Middle Eocene unconsolidated clastics with interbedded lignitic coal seams that are mined at the surface. In this study, 357 lithologic logs are integrated with measured outcrop sections and paleo-botanical data to interpret the depositional environments and sequence stratigraphic framework of the rim syncline fill. As salt withdrew, it generated an elongate mini-basin that mimicked an incised valley. The sustained accommodation and slow broadening of the syncline affected the stratigraphic architecture and contributed to the preservation of coal units. The clastic units in the syncline filled in seven depositional stages: 1) tidally influenced fluvial estuarine channels; 2) mixed tide- and wave- dominated estuaries; 3) prograding wave dominate deltas; 4) transgressive shoreline deposits; 5) braided fluvial channels; 6) estuaries; and 7) prograding tide-dominated channels. The succession defines four 3^rd order sequences and several higher order sequences that are possibly related to Milankovitch cycles. The higher order sequences are dominantly characterized by stacked transgressive cycles of thick, lowstand coals overlain by estuarine sands. The nearly continuous warm and wet Eocene climate was conducive to continuous peat production with a climatic overprint recorded in the mire type: ombrotrophic mires developed in wetter times and rheotrophic mires developed in relatively drier conditions pointing to the presence of orbitally controlled seasonality. Both mire types were impacted by the interplay of subsidence and base-level. The continuous dropping of the mires below base-level via subsidence protected the mires against erosion and may account for the absence of coals outside of the rim synclines in the region.

© 2013 The Authors. Basin Research © 2013 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists

The formation processes of the late Neogene sedimentary basins in Northern Hokkaido have been investigated on the basis of rock magnetism, structural geology and numerical modeling. Untilted site-mean directions of remanent magnetization of the Wakkanai Formation, obtained from oriented core samples in Horonobe, suggest remarkable counterclockwise block rotation (~70°) since the late Neogene. Uniform microscopic fabric of the siliceous sediments was inferred from the alignment of the principal axes of the anisotropy of magnetic susceptibility (AMS). After correction for tectonic rotation, the maximum axis of AMS, which reflects the sedimentary fabric of the dominant paramagnetic minerals, is in an E-W direction, which is concordant with the influx direction of diatomaceous particles into the N-S elongate sedimentary basins. The difference in the bulk initial magnetic susceptibility of the siliceous sediments of the Wakkanai Formation between the depocenter of the basin and its peripheral part implies that terrigenous non-magnetic fraction has been sorted out during transportation of the detrital grains as gravity flows. As for the development mechanism of the N-S elongate late Neogene basins in Northern Hokkaido, their depocenter arrangement and subsidence pattern indicates dextral motions upon a longitudinal fault zone along the Eurasian convergent margin. Dislocation modeling was adopted in order to explain vertical displacement and rotational motion around the study area, and successfully restored the deformation pattern based on the assumption of dextral slip at a left-stepping part of a strand of the transcurrent fault.

© 2013 The Authors. Basin Research © 2013 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists

Two end-member models have been proposed for the Paleogene Andean foreland: a simple W-E migrating foreland model and a broken-foreland model. We present new stratigraphic, sedimentological and structural data from the Paleogene Quebrada de los Colorados (QLC) Formation, in the Eastern Cordillera, with which to test these two different models. Basin-wide unconformities, growthstrata and changes in provenance indicate deposition of the QLC Formation in a tectonically active basin. Both west- and east-vergent structures, rooted in the basement, controlled the deposition and distribution of the QLC Formation from the Middle Eocene to the Early Miocene. The provenance analysis indicates that the main source areas were basement blocks, like the Paleozoic Oire Eruptive Complex, uplifted during Paleogene shortening, and that delimits the eastern boundary of the present-day intraorogenic Puna plateau. A comparison of the QLC sedimentary basin-fill pattern with those of adjacent Paleogene basins in the Puna plateau and in the Santa Bárbara System highlights the presence of discrete depozones. These reflect the early compartmentalization of the foreland, rather than a stepwise advance of the deformation front of a thrust belt. The early Tertiary foreland of the southern central Andes is represented by a ca. 250-km-wide area comprising several deformation zones (Arizaro, Macón, Copalayo and Calchaquí) in which doubly vergent or asymmetric structures, rooted in the basement, were generated. Hence, classical foreland model is difficult to apply in this Paleogene basin; and our data and interpretation agree with a broken-foreland model.

In the mid-Cretaceous Lasarte sub-basin (LSB) [northeastern Basque-Cantabrian Basin (BCB)] contemporaneous and syn-depositional thin- and thick-skinned extensional tectonics occur due to the presence of a ductile detachment layer that decoupled the extension. Despite the interest in extension modes of rift basins bearing intra-stratal detachment layers, complex cases remain poorly understood. In the LSB, field results based on mapping, stratigraphic, sedimentological and structural data show the relationship between growth strata and tectonic structures. Syn-depositional extensional listric faults and associated folds and faults have been identified in the supra-detachment thin-skinned system. But stratigraphic data also indicate the activation of sub-detachment thick-skinned extensional faults coeval with the development of the thin-skinned system. The tectono-sedimentary evolution of the LSB, since the Late Aptian until the earliest Late Albian, has been interpreted based on thin- and thick-skinned extensional growth structures, which are fossilized by post-extensional strata. The development of the thin-skinned system is attributed to the presence of a ductile detachment layer (Upper Triassic Keuper facies) which decoupled the extension from deeper sub-detachment basement-involved faulting under a regional extensional/transtensional regime.

Ultra-large rift basins, which may represent palaeo-propagating rift tips ahead of continental rupture, provide an opportunity to study the processes that cause continental lithosphere thinning and rupture at an intermediate stage. One such rift basin is the Faroe-Shetland Basin (FSB) on the north-east Atlantic margin. To determine the mode and timing of thinning of the FSB, we have quantified apparent upper crustal β-factors (stretching factors) from fault heaves and apparent whole-lithosphere β-factors by flexural backstripping and decompaction. These observations are compared with models of rift basin formation to determine the mode and timing of thinning of the FSB. We find that the Late Jurassic to Late Palaeocene (pre-Atlantic) history of the FSB can be explained by a Jurassic to Cretaceous depth-uniform lithosphere thinning event with a β-factor of ~1.3 followed by a Late Palaeocene transient regional uplift of 450–550 m. However, post-Palaeocene subsidence in the FSB of more than 1.9 km indicates that a Palaeocene rift with a β-factor of more than 1.4 occurred, but there is only minor Palaeocene or post-Palaeocene faulting (upper crustal β-factors of less than 1.1). The subsidence is too localized within the FSB to be caused by a regional mantle anomaly. To resolve the β-factor discrepancy, we propose that the lithospheric mantle and lower crust experienced a greater degree of thinning than the upper crust. Syn-breakup volcanism within the FSB suggests that depth-dependent thinning was synchronous with continental breakup at the adjacent Faroes and Møre margins. We suggest that depth-dependent continental lithospheric thinning can result from small-scale convection that thins the lithosphere along multiple offset axes prior to continental rupture, leaving a failed breakup basin once seafloor spreading begins. This study provides insight into the structure and formation of a generic global class of ultra-large rift basins formed by failed continental breakup.

The composition, volume and stratigraphic organisation of submarine fan systems deposited along continental margins are expected to reflect the landscape from which the sediment was derived. During the Late Cretaceous, the Møre-Trøndelag margin, Norwegian North Sea was dominated by the deposition of deep-marine fines; the emplacement of 11 sand-rich submarine fan systems occurred only during a c. 3 Myr period in the Turonian-Coniacian. The systems were fed by sediment that was routed through submarine canyons incised into the basin margin; the canyons are underlain by angular unconformities and are interpreted to have resulted from tectonically induced changes in slope physiography and erosion by gravity flows. The areal extent of the onshore drainage catchments that supplied sediment to the fans has been estimated based on scaling relationships derived from modern source-to-sink systems. The results of our study suggest that the Turonian fans were sourced by drainage catchments that were up to ca.3600 km², extending more than ca.100 km inland from the palaeo-shoreline. The estimated inboard catchment extent correlates with the innermost structures of a large, long-lived, basement-involved, normal fault complex. On the basis of our analysis, we conclude that increased sediment supply to the Turonian fan systems reflects tectonic rejuvenation of the landscape, rather than eustatic sea-level or climate fluctuations. The duration of fan deposition is thus interpreted to reflect the ‘relaxation time’ of the landscape following tectonic perturbation, and fan system retrogradation and abandonment is interpreted to reflect the eventual depletion of the onshore sediment source. We demonstrate that a better understanding of the stratigraphic variability in deepwater depositional systems can be gained by taking a complete source-to-sink view of ancient sediment dispersal systems.

In this study, we use seismic reflection, well and core data to investigate the role that basin physiography and sediment routing systems played on the distribution, geometry and stratigraphic architecture of Upper Cretaceous submarine fans (SF) offshore Norway. The Late Cretaceous Møre-Trøndelag margin of western Norway was characterised by steep submarine slopes (gradient of ~0.3°–3°). Mudstones dominate the Upper Cretaceous slope succession, although a few regionally extensive, sandstone-dominated units are developed. We focus on the most regionally extensive sandstone unit, which is of Late Turonian-to-Early Coniacian age. Mapping and visualisation of 2D and 3D seismic reflection data and analysis of well data indicates that the sandstone unit comprises a total of 11 SF, which were fed by sand-rich sediment gravity flows routed through multiple upper slope canyons. Based on the internal organisation of seismic facies, four fan types have been identified: (i) Type Ia fans, which are characterised by <10 erosional channel complexes at their bases and aggradational to landward-stepping lobes in their upper parts; (ii) Type Ib fans, which are characterised by >10 erosional channel complexes at their bases and aggradational to landward-stepping lobe and mass-transport deposits near the fan apex in their upper parts; (iii) Type II fans, which are dominated by aggradational lobe deposits; and (iv) Type III fans, which are dominated by a single channel complex that passes downdip into a small terminal lobe. The different fan types are interpreted to reflect variable stratigraphic responses to source proximity and basin physiography, which is principally related to the degree of local fault reactivation and differential compaction. This variability highlights the diversity of fan types that may occur over short distances along continental margins, and demonstrates the importance of local controls in understanding the internal stratigraphic variability that may be present in deep-marine successions.

Although the structure of the central Peruvian Subandean zone is well defined, the timing of thrust-related exhumation and Cenozoic sedimentation remain poorly constrained. In this study, we report new apatite (U–Th)/He (AHe) and fission track (AFT) ages from thrust-belt and foreland strata along three published balanced cross sections. AHe data from the northern, thick-skinned domain (i.e. Shira Mountain, Otishi Cordillera and Ucayali Basin) show young AHe ages (ranging from 2.6 ± 0.2 to 13.1 ± 0.8 Ma) compared with AFT ages (ranging from 101 ± 5 to 133 ± 11 Ma). In the southern Camisea Basin, where deformation is mainly thin-skinned, AHe and AFT ages have been both reset and show young cooling ages (3.7 ± 0.8 Ma and 8 ± 2 Ma respectively). Using low-temperature thermochronology data and the latest fission track annealing and He diffusion codes, the thermal history of the study area has been reconstructed using inverse modelling. This history includes two steps of erosion: Early Cretaceous and late Neogene, but only Neogene sedimentation and exhumation varies in the different sectors of the study area. From a methodological point of view, large AHe data dispersion point to the need for refinement of AHe damage and annealing models. The influence of grain chemistry on damage annealing, multiple age components and the possibility of fission tracks as traps for He need further consideration. For the central Peruvian Subandes, AHe and AFT ages combined with balanced cross sections emphasize the dominant control of Paleozoic inheritance rather than climate on Cenozoic infilling and exhumation histories. Finally, our data provide the first field example of how thick-skinned thrust-related deformation and exhumation in the Subandes can be directly dated through AHe thermochronology.

Graben systems in extensional settings tend to be segmented with evidence of segment interaction. To gain a better understanding of the evolution of structures formed during graben growth and interaction, we here study the Grabens area of Canyonlands National Park, Utah, where a wide range of such structures is well exposed. With the aid of 3D numerical models, we attempt to reproduce structures observed in that region and to understand controls on the structural style of graben interaction by varying the spacing between pre-existing structures. The sensitivity of the system to the thickness of the salt layer is also tested. Four distinct types of structures are observed when the spacing between inherited weak zones is varied: (1) grabens connecting in a relay zone divided by a narrow central horst; (2) graben segments interacting via a secondary stepover graben; (3) grabens propagating alongside each other with limited segment interaction; and (4) an abandoned graben segment in a system of multiple competing grabens. The presence of a basal salt layer (Paradox Member) promotes efficient graben propagation. A comparison between the observed structures and the numerical model results indicates that the detachment salt layer is relatively thin in the study area.

The Santa Rosa basin of northeastern Baja California is one of several transtensional basins that formed during Neogene oblique opening of the Gulf of California. The basin comprises Late Miocene to Pleistocene sedimentary and volcanic strata that define an asymmetric half-graben above the Santa Rosa detachment, a low-angle normal fault with ca. 4–5 km of SE-directed displacement. Stratigraphic analysis reveals systematic basin-scale facies variations both parallel and across the basin. The basin-fill exhibits an overall fining-upward cycle, from conglomerate and breccia at the base to alternating sandstone-mudstone in the depocentre, which interfingers with the fault-scarp facies of the detachment. Sediment dispersal was transverse-dominated and occurred through coalescing alluvial fans from the immediate hanging wall and/or footwall of the detachment. Different stratigraphic sections reveal important lateral facies variations that correlate with major corrugations of the detachment fault. The latter represent extension-parallel folds that formed largely in response to the ca. N-S constrictional strain regime of the transtensional plate boundary. The upward vertical deflection associated with antiformal folding dampened subsidence in the northeastern Santa Rosa basin, and resulted in steep topographic gradients with a high influx of coarse conglomerate here. By contrast, the downward motion in the synform hinge resulted in increased subsidence, and led to a southwestward migration of the depocentre with time. Thus, the Santa Rosa basin represents a new type of transtensional rift basin in which oblique extension is partitioned between diffuse constriction and discrete normal faulting. ⁴⁰Ar/³⁹Ar geochronology of intercalated volcanic rocks suggests that transtensional deformation began during the Late Miocene, between 9.36 ± 0.14 Ma and 6.78 ± 0.12 Ma, and confirms previous results from low-temperature thermochronology (Seiler et al., 2011). Two other volcanic units that appear to be part of a conformable syn-rift sequence are, in fact, duplicates of pre-rift volcanics and represent allochthonous, gravity-driven slide blocks that originated from the hanging wall.

Foreland basin strata provide an opportunity to review the depositional response of alluvial systems to unsteady tectonic load variations at convergent plate margins. The lower Breathitt Group of the Pocahontas Basin, a sub-basin of the Central Appalachian Basin, in Virginia preserves an Early Pennsylvanian record of sedimentation during initial foreland basin subsidence of the Alleghanian orogeny. Utilizing fluvial facies distributions and long-term stacking patterns within the context of an ancient, marginal-marine foreland basin provides stratigraphic evidence to disentangle a recurring, low-frequency residual tectonic signature from high-frequency glacioeustatic events. Results from basin-wide facies analysis, corroborated with petrography and detrital zircon geochronology, support a two end-member depositional system of coexisting transverse and longitudinal alluvial systems infilling the foredeep during eustatic lowstands. Provenance data suggest that sediment was derived from low-grade metamorphic Grenvillian-Avalonian terranes and recycling of older Palaeozoic sedimentary rocks uplifted as part of the Alleghanian orogen and Archean-Superior-Province. Immature sediments, including lithic sandstone bodies, were deposited within a SE-NW oriented transverse drainage system. Quartzarenites were deposited within a strike-parallel NE-SW oriented axial drainage, forming elongate belts along the western basin margin. These mature quartzarenites were deposited within a braided fluvial system that originated from a northerly cratonic source area. Integrating subsurface and sandstone provenance data indicates significant, repeated palaeogeographical shifts in alluvial facies distribution. Distinct wedges comprising composite sequences are bounded by successive shifts in alluvial facies and define three low-frequency tectonic accommodation cycles. The proposed tectonic accommodation cycles provide an explanation for the recognized low-frequency composite sequences, defining short-term episodes of unsteady westward migration of the flexural Appalachian Basin and constrain the relative timing of deformation events during cratonward progression of the Alleghanian orogenic wedge.

The intermontane Quebrada de Humahuaca Basin (Humahuaca Basin) in the Eastern Cordillera of the southern Central Andes of NW Argentina (23°–24°S) records the evolution of a formerly contiguous foreland-basin setting to an intermontane depositional environment during the late stages of Cenozoic Andean mountain building. This basin has been and continues to be subject to shortening and surface uplift, which has resulted in the establishment of an orographic barrier for easterly sourced moisture-bearing winds along its eastern margin, followed by leeward aridification. We present new U–Pb zircon ages and palaeocurrent reconstructions suggesting that from at least 6 Ma until 4.2 Ma, the Humahuaca Basin was an integral part of a largely contiguous depositional system that became progressively decoupled from the foreland as deformation migrated eastward. The Humahuaca Basin experienced multiple cycles of severed hydrological conditions and subsequent re-captured drainage, fluvial connectivity with the foreland and sediment evacuation. Depositional and structural relationships among faults, regional unconformities and deformed landforms reveal a general pattern of intrabasin deformation that appears to be associated with different cycles of alluviation and basin excavation in which deformation is focused on basin-internal structures during or subsequent to phases of large-scale sediment removal.

A comprehensive interpretation of single and multichannel seismic reflection profiles integrated with biostratigraphical data and log information from nearby DSDP and ODP wells has been used to constrain the late Messinian to Quaternary basin evolution of the central part of the Alboran Sea Basin. We found that deformation is heterogeneously distributed in space and time and that three major shortening phases have affected the basin as a result of convergence between the Eurasian and African plates. During the Messinian salinity crisis, significant erosion and local subsidence resulted in the formation of small, isolated, basins with shallow marine and lacustrine sedimentation. The first shortening event occurred during the Early Pliocene (ca. 5.33–4.57 Ma) along the Alboran Ridge. This was followed by a major transgression that widened the basin and was accompanied by increased sediment accumulation rates. The second, and main, phase of shortening on the Alboran Ridge took place during the Late Pliocene (ca. 3.28–2.59 Ma) as a result of thrusting and folding which was accompanied by a change in the Eurasian/African plate convergence vector from NW-SE to WNW-ESE. This phase also caused uplift of the southern basins and right-lateral transtension along the WNW-ENE Yusuf fault zone. Deformation along the Yusuf and Alboran ridges continued during the early Pleistocene (ca. 1.81–1.19 Ma) and appears to continue at the present day together with the active NNE-SSW trending Al-Idrisi strike-slip fault. The Alboran Sea Basin is a region of complex interplay between sediment supply from the surrounding Betic and Rif mountains and tectonics in a zone of transpression between the converging African and European plates. The partitioning of the deformation since the Pliocene, and the resulting subsidence and uplift in the basin was partially controlled by the inherited pre-Messinian basin geometry.

The Matakaoa Debris Flow (MDF) is a 200-km-long mass-transport deposit resulting from the failure of the Matakaoa continental margin, northeast New Zealand, ca. 38–100 ky ago. In this study, high-quality bathymetric and seismic reflection data are used to identify the morpho-structural characters that reflect the kinematics of the MDF, as well as its interactions with basin sediments. We demonstrate how the transport energy, together with the local topography led to the present geometry and complex structure of the MDF deposits. The remarkable transport energy of the MDF is demonstrated by its dynamic impact on adjacent sedimentary series, including erosion of the substratum, shearing and compressional deformation. In the proximal zone of transport, momentous substratum erosion, demonstrated by giant tool marks and truncated sediments at the base of the debrite, triggered the excavation of a large volume (>200 km³) of basin sediments. The size of transported blocks (up to 3-km long) is used to estimate the matrix yield strength in an early stage of transport. In the distal zone of transport, 100 km north of the source, seismic profiles show the propagation of thrust structures from the MDF into adjacent basin sediments. This study highlights that the remarkable volume of 2000 km³ of deposits partly resulted from the propagation of compressive structures within the basin sedimentary series to the front of the debrite.

Decaying mountain ranges often show a surprisingly dynamic pattern of landscape evolution. Although one might expect a simple, monotonic decline in relief over time, evidence from several inactive mountain ranges shows alternating sequences of deposition and erosion in the associated basins, suggesting variations in relief and exhumation rate in the ranges themselves. Examples include the Southern Rocky Mountains, the Pyrenees, the European Alps and the Atlas Mountains. In this paper, we explore the possible origins of post-orogenic landscape dynamics using a simple mathematical model of a mountain range and an adjacent foreland basin. The analysis highlights the importance of mass balance. In particular, a switch from basin exhumation to renewed sedimentation requires either an increase in sediment influx from the range or a decrease in sediment outflux beyond the basin margin. Although it is widely understood that post-orogenic changes in erosion and sediment flux can have multiple causes (including climate change, regional tectonic uplift or tilting, or exhumation of variable lithologies), an important implication of our analysis is that the impact of such changes must differ in sign or magnitude between the range and the basin to be recorded. This requirement places an important constraint on viable explanations for alternating sequences of deposition and erosion in a decaying mountain-basin pair.

The Northern Apennines provide an example of long-term deep-water sedimentation in an underfilled pro-foreland basin first linked to an advancing orogenic wedge and then to a retreating subduction zone during slab rollback. New palaeobathymetric and geohistory analyses of turbidite systems that accumulated in the foredeep during the Oligocene-Miocene are used to unravel the basin subsidence history during this geodynamic change, and to investigate how it interplayed with sediment supply and basin tectonics in controlling foredeep filling. The results show an estimated ca. 2 km decrease in palaeowater depth at ca. 17 Ma. Moreover, a change in basin subsidence is documented during Langhian time, with an average decompacted subsidence rate, during individual depocentre life, that increased from <0.3 to 0.4–0.6 mm y⁻¹, together with the appearance of a syndepositional backstripped subsidence bracketed between 0.1 and 0.2 mm y⁻¹. This change prevented the basin from complete filling during late Miocene and is interpreted as the foredeep response to initial rollback of the downgoing Adriatic slab. Thus, the Northern Apennine system provides an example of a pro-foreland basin that experienced both a slow- and high-subsidence regime as a consequence of the advancing then retreating evolution of the collisional system.

The stratigraphic development of an Upper Jurassic syn-rift succession exposed at outcrop in the Inner Moray Firth Basin has been investigated using high-resolution biostratigraphy and sedimentology. A continuous 970 m thick section, exposed in the hangingwall of the Helmsdale Fault was logged in detail. The succession spans 8 Ma and contains eight lithofacies types, which indicate deposition in a deep marine setting. Boulder beds contain large, angular clasts, with bed thicknesses typically >2 m and poor sorting suggesting deposition by debris flows. An inverse clast stratigraphy is observed; the oldest boulder beds contain sandstone clasts of Upper Old Red Sandstone (ORS) with younger debris flows containing clasts of Middle ORS calcareous siltstone. A marked change from siliciclastic to carbonate dominated sedimentation occurred during the Early Tithonian, interpreted primarily as a result of change in lithologies in the footwall catchment from sandstone to calcareous siltstone, which reduced supply of siliciclastic sediment. Secondary factors are identified as increased aridity in the Early Tithonian, which reduced sand supply from the hinterland and a third-order Early Tithonian eustatic sea-level rise, which trapped coarser clastic sediment within the hinterland. Biostratigraphy allows calculation of variations in sedimentation rates with recognition of: (1) an early rift phase characterised by sandy turbidite deposition, when sedimentation rates averaged 0.08 m/ky, (2) a rift climax phase from the Early Kimmeridgian where sedimentation rates increased steadily to a maximum of 0.64 m/ky in the Early Tithonian, with strata dominated by boulder scale clast-supported debris flows and (3) a late stage of rifting from the mid Tithonian, where sedimentation rates decreased to 0.07 m/ky. Overall sedimentation rates are comparable to those of other deep marine rift basins. Unroofing a resistant lithology on the footwall of a rift has important implications for siliciclastic sediment supply in rift basins.

The Southern Tail-End Graben, Danish Central Graben, is characterized by a lateral variation in the thickness and mobility of pre-rift Zechstein Supergroup evaporites, allowing investigation of how supra-basement evaporite variability influences rift structural style and tectono-stratigraphy. The study area is divided into two structural domains based on interpretations of the depositional thickness and mobility of the Zechstein Supergroup. Within each domain, we examine the overall basin morphology and the structural styles in the pre-Zechstein and supra-Zechstein (cover) units. Furthermore, integration of two-way travel-time (TWT)-structure and -thickness maps allows fault activity and evaporite migration maps to be generated for pre- and syn-rift stratal units within the two domains, permitting constraints to be placed on: (i) the timing of activity on pre-Zechstein and cover faults and (ii) the onset, duration and migration direction of mobile evaporites. The northern domain is interpreted to be free from evaporite-influence, and has developed in a manner typical of brittle-only, basement-involved rifts. Syn-rift basins display classical half-graben geometries bounded by thick-skinned faults. In contrast, the southern domain is interpreted to be evaporite-influenced, and cover structure reflects a southward increase in the thickness and mobility of the Zechstein Supergroup evaporites. Fault-related and evaporite-related folding is prominent in the southern domain, together with variable degrees of decoupling of sub-Zechstein and cover fault and fold systems. The addition of mobile evaporites to the rift results in: (i) complex and spatially variable modes of tectono-stratigraphic evolution; (ii) syn-rift stratal geometries which are condensed above evaporite swells and over-thickened in areas of withdrawal; (iii) compartmentalized syn-rift depocentres; and (iv) masking of rift-related megasequence boundaries. Through demonstrating these deviations from the characteristics of rifts free from evaporite influence, we highlight the first order control evaporites may exert upon rift structural style and the distribution and thicknesses of syn-rift units.

Locating and quantifying overpressures are essential to understand basin evolution and hydrocarbon migration in deep basins and thickly sedimented continental margins. Overpressures influence sediment cohesion and hence fault slip in seismically active areas or failure on steep slopes, and may drive catastrophic fluid expulsion. They also represent a significant drilling hazard. Here, we present a method to calculate the pore pressure due to disequilibrium compaction. Our method provides an estimate of the compaction factor, surface porosity and sedimentation rate of each layer in a sediment column using a decompaction model and the constraints imposed by seismic data and geological observations. For a range of surface porosities, an ad hoc iterative equation determines the compaction factor that gives a calculated layer thickness that matches the observed thickness within a tolerance. The surface porosity and compaction factor are then used to obtain a density profile and a corresponding estimate of P-wave velocity (V_p). The selected parameters are those that give a good match with both the observed and calculated layer thicknesses and V_p profiles. We apply our method to the centre of the Eastern Black Sea Basin (EBSB), where overpressures have been linked to a low-velocity zone (LVZ) at ca. 5500–8500 m depth. These overpressures were generated by the relatively high sedimentation rate of ca. 0.28 m ka⁻¹ of the low permeability organic-rich Maikop formation at 33.9–20.5 Ma and an even higher sedimentation rate of ca. 0.85 m ka⁻¹ at 13–11 Ma. We estimate a maximum pore pressure of ca. 138 MPa at ca. 8285 m depth, associated with a ratio of overpressure to vertical effective stress in hydrostatic conditions () of ca. 0.7. These values are lower than those presented in a previous study for the same area.

The syn-rift/post-rift transition of the late Ediacaran-mid Cambrian Atlas rift is characterized by the interplay of several processes, such as a widespread episode of fracturing and tilting, associated with encasement of fault-controlled vein metallic ore deposits of economic importance, and carbonate production and phosphogenesis (Taguedit Bed, Tabia Member) bordering rift-flank uplifts. A correlatable unconformity marks the end of these processes and the beginning of a thermal subsidence-dominated regime with development of a more stable, carbonate, peritidal-dominated platform (Tifnout Member). Late Ediacaran microbial carbonate production and phosphogenesis extended in discontinuous belts around the periphery of uplifted rift shoulders and flanks. Karst development is interpreted to have formed along synsedimentary faults and fractures during abrupt tectonic uplift associated with emplacement of polymetallic hydrothermal dikes (rich in Cu, Fe and subsidiary Pb, Zn). Isotopic analysis indicates that speleothem precipitation in karstic palaeocaves displays significantly lighter δ¹³C and δ¹⁸O values as compared to the host dolomite, implying calcite precipitation by terrestrial fluids rich in decomposing organic matter and/or microbial activity in the cave system.