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.     

Tectono‐sedimentary development of early syn‐rift deposits: the Abura Graben,Suez Rift,Egypt

The thickness and distribution of early syn‐rift deposits record the evolution of structures accommodating the earliest phases of continental extension. However, our understanding of the detailed tectono‐sedimentary evolution of these deposits is poor, because in the subsurface, they are often deeply buried and below seismic resolution and sparsely sampled by borehole data. Furthermore, early syn‐rift deposits are typically poorly exposed in the field, being buried beneath thick, late syn‐rift and post‐rift deposits. To improve our understanding of the tectono‐sedimentary development of early syn‐rift strata during the initial stages of rifting, we examined quasi‐3D exposures in the Abura Graben, Suez Rift, Egypt. During the earliest stage of extension, forced folding above blind normal fault segments, rather than half‐graben formation adjacent to surface‐breaking faults, controlled rift physiography, accommodation development and the stratigraphic architecture of non‐marine, early syn‐rift deposits. Fluvial systems incised into underlying pre‐rift deposits and were structurally focused in the axis of the embryonic depocentre, which, at this time, was characterized by a fold‐bound syncline rather than a fault‐bound half graben. During this earliest phase of extension, sediment was sourced from the rift shoulder some 3 km to the NE of the depocentre, rather than from the crests of the flanking, intra‐basin extensional forced folds. Fault‐driven subsidence, perhaps augmented by a eustatic sea‐level rise, resulted in basin deepening and the deposition of a series of fluvial‐dominated mouth bars, which, like the preceding fluvial systems, were structurally pinned within the axis of the growing depocentre, which was still bound by extensional forced folds rather than faults. The extensional forced folds were eventually locally breached by surface‐breaking faults, resulting in the establishment of a half graben, basin deepening and the deposition of shallow marine sandstone and fan‐delta conglomerates. Because growth folding and faulting were coeval along‐strike, syn‐rift stratal units deposited at this time show a highly variable along‐strike stratigraphic architecture, locally thinning towards the growth fold but, only a few kilometres along‐strike, thickening towards the surface‐breaking fault. Despite displaying the classic early syn‐rift stratigraphic motif recording net upward‐deepening, extensional forced folding rather than surface faulting played a key role in controlling basin physiography, accommodation development, and syn‐rift stratal architecture and facies development during the early stages of extension. This structural and stratigraphic observations required to make this interpretation are relatively subtle and may go unrecognized in low‐resolution subsurface data sets.     

Tectono‐sedimentary evolution of the western Corinth rift (Central Greece)

The Corinth rift (Greece) is one of the world's most active rifts. The early Plio‐Pleistocene rift is preserved in the northern Peloponnese peninsula, south of the active Corinth rift. Although chronostratigraphic resolution is limited, new structural, stratigraphic and sedimentological data for an area >400 km² record early rift evolution in three phases separated by distinct episodes of extension rate acceleration and northward fault migration associated with major erosion. Minimum total N–S extension is estimated at 6.4–7.7 km. The earliest asymmetrical, broad rift accommodated slow extension (0.6–1 mm a^?1) over >3 Myrs and closed to the west. North‐dipping faults with throws of 1000–2200 m defined narrow blocks (4–7 km) with little footwall relief. A N‐NE flowing antecedent river system infilled significant inherited relief (Lower group). In the earliest Pleistocene, significant fluvial incision coincided with a 15 km northward rift margin migration. Extension rates increased to 2–2.5 mm a^?1. The antecedent rivers then built giant Gilbert‐type fan deltas (Middle group) north into a deepening lacustrine/marine basin. N‐dipping, basin margin faults accommodated throws <1500 m. Delta architecture records initiation, growth and death of this fault system over ca. 800 ka. In the Middle Pleistocene, the rift margin again migrated 5 km north. Extension rate increased to 3.4–4.8 mm a^?1. This transition may correspond to an unconformity in offshore lithostratigraphy. Middle group deltas were uplifted and incised as new hangingwall deltas built into the Gulf (Upper group). A final increase to present‐day extension rates (11–16 mm a^?1) probably occurred in the Holocene. Fault and fault block dimensions did not change significantly with time suggesting control by crustal rheological layering. Extension rate acceleration may be due to strain softening or to regional tectonic factors.     

Tectono‐sedimentary evolution of the northern Iranian Plateau: insights from middle–late Miocene foreland‐basin deposits

Sedimentary basins in the interior of orogenic plateaus can provide unique insights into the early history of plateau evolution and related geodynamic processes. The northern sectors of the Iranian Plateau of the Arabia–Eurasia collision zone offer the unique possibility to study middle–late Miocene terrestrial clastic and volcaniclastic sediments that allow assessing the nascent stages of collisional plateau formation. In particular, these sedimentary archives allow investigating several debated and poorly understood issues associated with the long‐term evolution of the Iranian Plateau, including the regional spatio‐temporal characteristics of sedimentation and deformation and the mechanisms of plateau growth. We document that middle–late Miocene crustal shortening and thickening processes led to the growth of a basement‐cored range (Takab Range Complex) in the interior of the plateau. This triggered the development of a foreland‐basin (Great Pari Basin) to the east between 16.5 and 10.7 Ma. By 10.7 Ma, a fast progradation of conglomerates over the foreland strata occurred, most likely during a decrease in flexural subsidence triggered by rock uplift along an intraforeland basement‐cored range (Mahneshan Range Complex). This was in turn followed by the final incorporation of the foreland deposits into the orogenic system and ensuing compartmentalization of the formerly contiguous foreland into several intermontane basins. Overall, our data suggest that shortening and thickening processes led to the outward and vertical growth of the northern sectors of the Iranian Plateau starting from the middle Miocene. This implies that mantle‐flow processes may have had a limited contribution toward building the Iranian Plateau in NW Iran.     

Evolution of the Longmen Shan Foreland Basin (Western Sichuan, China) during the Late Triassic Indosinian Orogeny

The Longmen Shan Foreland Basin developed as a flexural foredeep during the Late Triassic Indosinian orogeny, spanning the time period c. 227–206 Ma. The basin fill can be divided into three tectonostratigraphic units overlying a basal megasequence boundary, and is superimposed on the Palaeozoic–Middle Triassic (Anisian) carbonate‐dominated margin of the South China Block. The remains of the load system responsible for flexure of the South China foreland can be seen in the Songpan‐Ganzi Fold Belt and Longmen Shan Thrust Belt. Early in its history the Longmen Shan Foreland Basin extended well beyond its present northwestern boundary along the trace of the Pengguan Fault, to at least the palinspastically restored position of the Beichuan Fault. The basal boundary of the foreland basin megasequence is a good candidate for a flexural forebulge unconformity, passing from conformity close to the present trace of the Beichuan Fault to a karstified surface towards the southeast. The overlying tectonostratigraphic unit shows establishment and drowning of a distal margin carbonate ramp and sponge build‐up, deepening into offshore marine muds, followed by progradation of marginal marine siliciclastics, collectively reminiscent of the Alpine underfilled trinity of Sinclair (1997) . Tectonostratigraphic unit 2 is marked by the severing of the basin's oceanic connection, a major lake flooding and the gradual establishment of major deltaic‐paralic systems that prograded from the eroding Longmen Shan orogen. The third tectonostratigraphic unit is typified by coarse, proximal conglomerates, commonly truncating underlying rocks, which fine upwards into lacustrine shales. The foreland basin stratigraphy has been further investigated using a simple analytical model based on the deflection by supracrustal loads of a continuous elastic plate overlying a fluid substratum. Load configurations have been partly informed by field geology and constrained by maximum elevations and topographic profiles of present‐day mountain belts. The closest match between model predictions and stratigraphic observations is for a relatively rigid plate with flexural rigidity on the order of 5 × 10²³ to 5 × 10²⁴ N m (equivalent elastic thickness of c. 43–54 km). The orogenic load system initially (c. 227–220 Ma) advanced rapidly (>15 mm yr^?1) towards the South China Block in the Carnian, associated with the rapid closure of the Songpan‐Ganzi ocean, before slowing to < 5 mm yr^?1 during the sedimentation of the upper two tectonostratigraphic units (c. 220–206 Ma).     

The tectono‐sedimentary evolution of a supra‐detachment rift basin at a deep‐water magma‐poor rifted margin: the example of the Samedan Basin preserved in the Err nappe in SE Switzerland

We describe the tectono‐sedimentary evolution of a Middle Jurassic, rift‐related supra‐detachment basin of the ancient Alpine Tethys margin exposed in the Central Alps (SE Switzerland). Based on pre‐Alpine restoration, we demonstrate that the rift basin developed over a detachment system that is traced over more than 40 km from thinned continental crust to exhumed mantle. The detachment faults are overlain by extensional allochthons consisting of upper crustal rocks and pre‐rift sediments up to several kilometres long and several hundreds of metres thick, compartmentalizing the distal margin into sub‐basins. We mapped and restored one of these sub‐basins, the Samedan Basin. It consists of a V‐shape geometry in map view, which is confined by extensional allochthons and floored by a detachment fault. It can be restored over a minimum distance of 11 km along and about 4 km perpendicular to the basin axis. Its sedimentary infill can be subdivided into basal (initial), intermediate (widening) and top (post‐tectonic) facies tracts. These tracts document (1) formation of the basin initially bounded by high‐angle faults and developing into low‐angle detachment faults, (2) widening of the basin and (3) migration of deformation further outboard. The basal facies tract is made of locally derived, poorly sorted gravity flow deposits that show a progressive change from hangingwall to footwall‐derived lithologies. Upsection the sediments develop into turbidity current deposits that show retrogradation (intermediate facies tract) and starvation of the sedimentary system (post‐tectonic facies tract). On the scale of the distal margin, the syn‐tectonic record documents a thinning‐ and fining‐upward sequence related to the back stepping of the tectonically derived sediment source, progressive starvation of the sedimentary system and migration of deformation resulting in exhumation and progressive delamination of the thinned crust during final rifting. This study provides valuable insights into the tectono‐sedimentary evolution and stratigraphic architecture of a supra‐detachment basin formed over hyper‐extended crust.     

Anomalous passive subsidence of deep‐water sedimentary basins: a prearc basin example,southern New Caledonia Trough and Taranaki Basin,New Zealand

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 is 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.     

江西永丰-崇仁盆地晚白垩世沉积体及其演化模式

华东南地区白垩纪地壳伸展作用形成一系列SW-NE向展布的陆相断陷盆地,一般由粒度较粗的红色碎屑岩地层充填。赣杭构造带西段的江西永丰-崇仁盆地晚白垩世龟峰群角度不整合覆盖于早白垩世鹅湖岭组碎斑熔岩之上,自下而上包括河口组、塘边组和莲荷组。根据野外露头剖面沉积组构特征,可以识别出冲积扇、河流和湖泊等三种沉积体系。对各沉积相沉积物组成、沉积构造、垂向相序进行了探查认为,研究区上白垩统具有粗-细-粗的粒度变化旋回特征,反映了自下而上由冲积扇、河流到河流、湖泊再到冲积扇、河流沉积体系的有序变化。结合区域构造演化资料,初步建立的盆地沉积演化模式表明,河口组和塘边组为连续沉积,代表了断陷盆地开始发育和湖盆扩大阶段,反映了控盆构造由强烈活跃期到间歇宁静期的逐渐过渡。莲荷组再次以冲积扇和辫状河相砾岩为主,其中大量来自下伏红层的砾石成分说明莲荷组沉积时期控盆构造运动加剧。江西永丰-崇仁盆地沉积体系时空上明显的变化过程,可能是赣杭构造带晚白垩世陆相断陷盆地演化主要受区域断裂控制的一个典型代表。     

Morphostructure,tectono‐sedimentary evolution and seismic potential of the Horseshoe Fault,SW Iberian Margin

High‐resolution acoustic and seismic data acquired 100 km offshore Cape São Vicente, image with unprecedented detail one of the largest active reverse faults of the SW Iberian Margin, the Horseshoe Fault (HF). The HF region is an area seismogenically active, source of the largest magnitude instrumental and historical earthquake (M_w > 6) occurred in the SW Iberian Margin. The HF corresponds to a N40 trending, 110 km long, and NW‐verging active thrust that affects the whole sedimentary sequence and reaches up to the seafloor, generating a relief of more than 1 km. The along‐strike structural variability as well as fault trend suggests that the HF is composed by three main sub‐segments: North (N25), Central (N50) and South (N45). Swath‐bathymetry, TOBI sidescan sonar backscatter and parametric echosounder TOPAS profiles reveal the surface morphology of the HF block, characterized by several, steep (20°) small scarps located on the hangingwall, and a succession of mass transport deposits (i.e. turbidites) on its footwall, located in the Horseshoe Abyssal Plain. A succession of pre‐stack depth‐migrated multichannel seismic reflection profiles across the HF and neighbouring areas allowed us to constrain their seismo‐stratigraphy, structural geometry, tectono‐sedimentary evolution from Upper Jurassic to present‐day, and to calculate their fault parameters. Finally, on the basis of segment length, surface fault area and seismogenic depth we evaluated the seismic potential of the HF, which in the worst‐case scenario may generate an earthquake of magnitude M_w 7.8 ± 0.1. Thus, considering the tectonic behaviour and near‐shore location, the HF should be recognized in seismic and tsunami hazard assessment models of Western Europe and North Africa.     

1975-2010年石羊河流域绿洲时空演变研究

应用RS和GIS技术,以石羊河流域绿洲为研究对象,对1975 2010年流域绿洲的时空动态变化进行了监测,并结合气候变化、地表径流量和人类活动等资料探讨了绿洲变化的原因.结果表明:近35年来,石羊河流域绿洲整体规模呈波动变化的趋势,1975、1990、2000年和2010年,流域绿洲总面积分别为7 563.06、7 730.62、7 131.56 km2和7 459.43 km2.通过分析绿洲与荒漠面积之间的转化发现绿洲主要经历了“绿洲化-荒漠化-再绿洲化”的过程,绿洲面积缩小了103.63 km2.绿洲内部耕地、城镇居民地和水域面积增加,而林地和草地面积缩小.绿洲的变化受自然因素和人类活动的共同作用,但人口数量的增加、经济的发展以及地表径流的变化对绿洲演变的影响更为显著.     

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.     

Evolution of salt structures in the northern Paradox Basin: controls on evaporite deposition,salt wall growth and supra‐salt stratigraphic architecture

The northern Paradox Basin evolved during the Late Pennsylvanian–Permian as an immobile foreland basin, the result of flexural subsidence in the footwall of the growing Uncompahgre Ancestral Rocky Mountain thick‐skinned uplift. During the Atokan‐Desmoinesian (～313–306 Ma) fluctuating glacio‐eustatic sea levels deposited an ～2500 m thick sequence of evaporites (Paradox Formation) in the foreland basin, interfingering with coarse clastics in the foredeep and carbonates around the basin margins. The cyclic deposition of the evaporites produced a repetitive sequence of primarily halite, with minor clastics, organic shales and anhydrite. Sediment loading of the evaporites subsequently produced a series of salt walls and minibasins, through the process of passive diapirism or downbuilding. Faults at the top Mississippian level localised the development of linear salt walls (up to 4500 m high) along a NW–SE trend. A crosscutting NE–SW structural trend was also important in controlling the evaporite facies and the abrupt termination of the salt walls. Seismic, well and field data define the proximal Cutler Group (Permian) as a basinward prograding sequence derived from the growing Uncompahgre uplift that drove salt basinwards (towards the southwest), triggering the growth of the salt walls. Sequential structural restorations indicate that the most proximal salt walls evolved earlier than the more distal ones. The successive development of salt‐withdrawal minibasins associated with each growing salt wall implies that parts of the Cutler Group in one minibasin may have no chronostratigraphic equivalent in other minibasins. Localised changes in along‐strike salt wall growth and evolution were critical in the development of facies and thickness variations in the late Pennsylvanian to Triassic stratigraphic sequences in the flanking minibasins. Salt was probably at or very close to the surface during the downbuilding process leading to localised thinning, deposition of diapir‐derived detritus and rapid facies changes in sequences adjacent to the salt wall structures.     

Subsurface fluid flow in the deep‐water Kwanza Basin,offshore Angola

Integrated analysis of high‐quality three‐dimensional (3D) seismic, seabed geochemistry, and satellite‐based surface slick data from the deep‐water Kwanza Basin documents the widespread occurrence of past and present fluid flow associated with dewatering processes and hydrocarbon migration. Seismic scale fluid flow phenomena are defined by seep‐related seafloor features including pockmarks, mud or asphalt volcanoes, gas hydrate pingoes, as well as shallow subsurface features such as palaeo‐pockmarks, direct hydrocarbon indicators (DHIs), pipes and bottom‐simulating reflections (BSRs). BSR‐derived shallow geothermal gradients show elevated temperatures attributed to fluid advection along inclined stratigraphic carrier beds around salt structures in addition to elevated shallow thermal anomalies above highly conductive salt bodies. Seabed evidences of migrated thermogenic hydrocarbons and surface slicks are used to differentiate thermogenic hydrocarbon migration from fluid flow processes such as dewatering and biogenic gas migration. The analysis constrains the fluid plumbing system defined by the three‐dimensional distribution of stratigraphic carriers and seal bypass systems through time. Detailed integration and iterative interpretation have confirmed the presence of mature source rock and effective migration pathways with significant implications for petroleum prospectivity in the post‐salt interval. Integration of seismic, seabed geochemistry and satellite data represents a robust method to document and interpret fluid flow phenomena along continental margins, and highlights the importance of integrated fluid flow studies with regard to petroleum exploration, submarine geohazards, marine ecosystems and climate change.     

Evolution of drainage,sediment-flux and fluvio-deltaic sedimentary systems response in hanging wall depocentres in evolving non-marine rift basins: Paleogene of Raoyang Sag,Bohai Bay Basin,China

The dynamics of sediment feeding into rift basins and the geomorphologic nature of source areas are critical elements in understanding the evolution of rifted basins. This study integrates seismic, well and geochronologic data on the western dipslope of the Raoyang Sag, a rift associated sub-basin to the larger Bohai Bay Basin of China to define the history of drainage development for the basin and to assess the sedimentologic response to drainage evolution events. In the Paleogene-age Lixian Slope, as indicated by paleo-drainage configuration, progradational seismic geometries, compositional maturity and zircon-tourmaline-rutile maturity index trends, three drainages; the paleo-Daqing River, paleo-Tang River and paleo-Dasha River drainages were feeding three closely spaced hanging wall deltaic depositional systems; Delta A fed from the northwest, Delta B fed from the west and Delta C fed from the southwest, respectively. From the late Eocene to early Oligocene, a decrease in sediment-flux into the hanging wall is documented and petrographic analysis is used to link these changes to stream-capture in the upstream catchment of the Daqing River. This change is coupled with morphologic changes in the geometries of Deltas A and C, both of which show decreasing deltaic areas, changes in lobe geometry and changes in distributary channel sizes. In addition, the progradational direction of Delta C changes from perpendicular-to-the-rift axis to prograding oblique-to-the-rift axis. It is apparent that the progradation and retrogradational changes in rift margin deltas do not happen in isolation, but such changes can affect growth and progradation direction in adjacent deltas. This work shows that the decrease in sediment-flux, caused by a drainage capture, will result in a decrease in distributary channel size and delta size and may result in upstream deltas taking advantage of such decreasing confinement to prograde more obliquely to the rift axis.     

Fracturing and fluid‐flow during post‐rift subsidence in carbonates of the Jandaíra Formation,Potiguar Basin,NE Brazil

Pervasive fracture networks are common in many reservoir‐scale carbonate bodies even in the absence of large deformation and exert a major impact on their mechanical and flow behaviour. The Upper Cretaceous Jandaíra Formation is a few hundred meters thick succession of shallow water carbonates deposited during the early post‐rift stage of the Potiguar rift (NE Brazil). The Jandaíra Formation in the present onshore domain experienced <1.5 km thermal subsidence and, following Tertiary exhumation, forms outcrops over an area of >1000 km². The carbonates have a gentle, <5?, dip to the NE and are affected by few regional, low displacement faults or folds. Despite their simple tectonic history, carbonates display ubiquitous open fractures, sub‐vertical veins, and sub‐vertical as well as sub‐horizontal stylolites. Combining structural analysis, drone imaging, isotope studies and mathematical modelling, we reconstruct the fracturing history of the Jandaíra Formation during and following subsidence and analyse the impact fractures had on coeval fluid flow. We find that Jandaíra carbonates, fully cemented after early diagenesis, experienced negligible deformation during the first few hundreds of meters of subsidence but were pervasively fractured when they reached depths >400–500 m. Deformation was accommodated by a dense network of sub‐vertical mode I and hybrid fractures associated with sub‐vertical stylolites developed in a stress field characterised by a sub‐horizontal σ₁ and sub‐vertical σ₂. The development of a network of hybrid fractures, rarely reported in the literature, activated the circulation of waters charged in the mountainous region, flowing along the porous Açu sandstone underlying the Jandaíra carbonates and rising to the surface through the fractured carbonates. With persisting subsidence, carbonates reached depths of 800–900 m entering a depth interval characterised by a sub‐vertical σ₁. At this stage, sub‐horizontal stylolites developed liberating calcite which sealed the sub‐vertical open fractures transforming them in veins and preventing further flow. During Tertiary exhumation, several of the pre‐existing veins and stylolites opened and became longer, and new fractures were created typically with the same directions of the older features. The simplicity of our model suggests that most rocks in passive margin settings might have followed a similar evolution and thus display similar structures.     

Tectonic activation,source area stratigraphy and provenance changes in a rift basin: the Early Cretaceous Tucano Basin (NE‐Brazil)

Changes in sandstone and conglomerate maturity in tectonically active basins can be considered either as the product of climatic change or of tectonic restructuring of the feeder drainage system. Besides these regional controls, changes in the configuration of local sources can expressively affect basin fill composition. The Early Cretaceous fluvial successions of the Tucano Basin, a rift basin in northeastern Brazil related to the South Atlantic opening, contain one such case of abrupt change in maturity, marked by the passage from pebbly sandstone and conglomerate rich in quartz and quartzite fragments (Neocomian to Barremian São Sebastião Formation) to more feldspathic pebbly sandstone and conglomerate bearing pebbles of varied composition (Aptian Marizal Formation). Systematic analysis of stratigraphic and spatial variation in palaeocurrents and composition of pebbles and cobbles from both units, integrated with the recognition of fluvial and alluvial fan deposits distribution, revealed an abrupt decrease in maturity during the passage from the São Sebastião Formation to the Marizal Formation. This change is explained by exhumation of basement rocks and erosional removal of originally widespread Silurian to Jurassic sandstone and conglomerate units which were a major source of reworked vein quartz and quartzite pebbles to the São Sebastião Formation. Basin border faults activation during the deposition of the Marizal Formation caused adjacent basement uplift above the local erosional base level at the basin borders, whereas during the São Sebastião Formation deposition, the basin border fault scarps probably exposed mineralogically mature sedimentary units. The proposed model has important implications for interpreting changes in sediment maturity in rift basin successions, as similar results are expected where activation of basin border faults occurs after the erosional removal of older sedimentary or volcanic units that controlled syn‐rift successions composition.     

Tectono‐climatic evolution of a Neogene intramontane basin (Late Miocene Carboneras subbasin,southeast Spain): revelations from basin mapping and biofacies analysis

Exceptional 3‐D exposures of fault blocks forming a 5 km × 10 km clastic sediment‐starved, marine basin (Carboneras subbasin, southeast Spain) allow a test of the response of carbonate sequence stratigraphic architectures to climatic and tectonic forcing. Temperate and tropical climatic periods recorded in biofacies serve as a chronostratigraphic framework to reconstruct the status of the basin within three time‐slices (late Tortonian–early Messinian, late Messinian, Pliocene). Structural maps and isopach maps trace out the distribution of fault blocks, faults, and over time, their relative motions, propagational patterns and life times, which demonstrate a changing layout of the basin because of a rotation of the regional transtensional stress field. Progradation of early Messinian reefal systems was perpendicular to the master faults of the blocks, which were draped by condensed fore‐slope sediments. The hangingwall basins coincided with the toe‐of‐slope of the reef systems. The main phase of block faulting during the late Tortonian and earliest Messinian influenced the palaeogeography until the late Pliocene (cumulative throw < 150–240 m), whereas displacements along block bounding faults, which moved into the hangingwall, died out over time. An associated shift of the depocentres of calciturbidites, slump masses and fault scarp degradation breccias reflects 500–700 m of fault propagation into the hangingwall. The shallow‐water systems of the footwall areas were repeatedly subject to emergence and deep peripheral erosion, which imply slow net relative uplift of the footwall. In the dip‐slope settings, erosional truncations of tilted proximal deposits prevail, which indicate rotational relative uplift. Block movements were on the order of magnitude of third order sea‐level fluctuations during the late Tortonian and earliest Messinian. We suggest that this might be the reason for the common presence of offlapping geometries in early Messinian reef systems of the Betic Cordilleras. During the late Pliocene, uplift rates fell below third order rates of sea‐level variations. However, at this stage, the basin was uplifted too far to be inundated by the sea again. The evolution of the basin may serve as a model for many other extensional basins around the world.     

Evolution of a bank failure along the River Danube at Dunaszekcső, Hungary

The banks of the River Danube are one of the most susceptible areas to mass wasting in Hungary. In 2007, a large slump began to develop along the Danube at Dunaszekcső and jeopardized properties on land and navigation in the river. Several factors such as geological, hydrogeological and morphological conditions, recurrent flooding and erosion by the Danube led to a gradual development of the large rotational slide. Slope failure has been monitored using GPS, precise levelling techniques and tiltmeters since October 2007. The expected location of the maximum lateral displacement and extrusion was indicated by GPS measurements from the middle of November 2007. The main phase of the slope failure evolution, i.e. the rapid movement on 12 February 2008 was indicated by accelerated tilting of the southern moving block prior to slumping. Small rise of the relatively stable part of the slope was measured after the rapid movements, which may be explained either by the elastic rebound along the slip surface, or by the intrusion of some plastic material into the lower section of the slope.Comparison of geodetic datasets and field observations with the timing of rainfall and water level changes of the Danube suggested that hydrological properties (subsurface flow processes, soil physical properties, infiltration, and perched water table) were primarily responsible for initiation of the studied slump. A model of slope failure evolution is proposed here based on the monitoring and field observations.     

Evolution of sedimentary environments of the middle Jiangsu coast, South Yellow Sea since late MIS 3

An evolutionary model of sedimentary environments since late Marine Isotope Stage 3 （late MIS 3, i.e., ca. 39 cal ka BP） along the middle Jiangsu coast is presented based upon a reinterpretation of core 07SR01, new correlations between adjacent published cores, and shallow seismic profiles recovered in the Xiyang tidal channel and adjacent northern sea areas. Geomorphology, sedimentology, radiocarbon dating and seismic and sequence stratigraphy are combined to confirm that environmental changes since late MIS 3 in the study area were controlled primarily by sea-level fluctuations, sediment discharge of paleo-rivers into the South Yellow Sea （SYS）, and minor tectonic subsidence, all of which impacted the progression of regional geomorphic and sedimentary environments （Le., coastal barrier island freshwater lacustrine swamp, river floodplain, coastal marsh, tidal sand ridge, and tidal channel）. This resulted in the formation of a fifth-order sequence stratigraphy, comprised of the parasequence of the late stage of the last interstadial （Para-Sq2）, including the highstand and forced regressive wedge system tracts （HST and FRWST）, and the parasequence of the postglacial period （Para-Sql）, including the transgressive and highstand system tracts （TST and HST）. The tidal sand ridges likely began to develop during the postglacial transgression as sea-level rise covered the middle Jiangsu coast at ca. 9.0 cal ka BP. These initially submerged tidal sand ridges were constantly migrating until the southward migration of the Yellow River mouth to the northern Jiangsu coast during AD 1128 to 1855. The paleo-Xiyang tidal channel that was determined by the paleo-tidal current field and significantly different from the modern one, was in existence during the Holocene transgressive maxima and lasted until AD 1128. Following the capture of the Huaihe River in AD 1128 by the Yellow River, the paleo-Xiyang tidal channel was infilled with a large amount of river-derived sediments from AD 1128 to 1855, causing the emergence of some of the previously submerged tidal sand ridges. From AD 1855 to the present, the infilled paleo-Xiyang tidal channel has undergone scouring, resulting in its modern form. The modern Xiyang tidal channel continues to widen and deepen, due both to strong tidal current scouring and anthropogenic activities.     

民勤盆地地下水地球化学演化模拟

根据稳定同位素分析,民勤盆地地下水在第四系总体补给环境较现代凉。在200m以下的深层地下水为晚更新世补给的古封存水,表现为还原环境。60m—120m左右的浅层水为古地下水与现代降水的混合水,但古地下水占的成分较多,部分水样为氧化环境。民勤盆地地下水地球化学特征主要形成于山区,在沿途运移过程强烈的蒸发浓缩作用占据主导地位,形成了浅层高矿化盐碱水,深层地下水活跃的阳离子交换作用形成高钠浓度水。通过利用PHREEEQC法对民勤盆地地下水化学进行质量平衡模拟,表明民勤盆地地下水水化学沿水流路径以HCO3^-、SO4^2-、Cl^-、Ca^2 、Na^ 升高为主要特征,方解石、白云石的饱和指数随水流路径有减少趋势,而石膏、芒硝和岩盐的饱和指数有增加的趋势：沿水流途径白云石、CO2、石膏、岩盐和芒硝溶解量逐渐增加是常量离子浓度升高的物质来源。