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In this review, we attempted to summarize and interpret the Phanerozoic geology and mineralization following the article (vol. 71 in Resource Geology) which reviewed the Precambrian geology and mineralization of North Korea. The basement of the Korean peninsula was built during the Precambrian and gradually became more evolved and complex during the Phanerozoic. The northern part of the peninsula was in the active and passive continental margins of the Korea–China platform during the Phanerozoic. In the tectonic environments of the Phanerozoic, the tectonic provinces of North Korea comprise several Paleozoic–Mesozoic intracontinental and rift basins as well as Cenozoic ocean border and rift basins. During the Paleozoic, the sedimentary strata were formed within the marine‐to‐nonmarine intracontinental basins, such as the largest Pyeongnam and Hyesan–Iwon basin, Imjingang rift basin, and several small structural basins, and the sedimentary type of limestone, dolomite, and coal deposits were formed. Mesozoic orogenic events in the peninsula were the most overwhelming geologic event causing block movements through collision and subduction of the paleo‐Pacific plate. Songrim orogeny (late Permian to early Triassic) might be caused by continental collision associated with strong deformation, metamorphism, and granite intrusion. Daebo orogeny (Jurassic) resumed the crustal deformation under a contractional setting during the subduction and caused dextral ductile shearing, magmatism, and metamorphism in the entire peninsula. Amnokgang orogeny, corresponding to Bulguksa orogeny in South Korea, during the Cretaceous formed several pull‐apart or transtensional basins probably because of oblique subduction of the Izanagi plate, and nonmarine sedimentary and pyroclastic sequences were deposited in the basin. The mineralization related to the Mesozoic plutonism was the most dominant in the peninsula. The considerable mineral deposits are ultramafic related magmatic Ni deposits owing to rift magmatism and granite related hydrothermal Au–Ag, Cu, Pb–Zn, Fe, W, and Mo deposits caused by the subduction of paleo‐Pacific plate. During the Tertiary, several structural basins under the extensional regime were overprinted on the Mesozoic basins in the northern part of the peninsula. They contain marine and nonmarine sedimentary rocks and felsic–mafic extrusives. Some sedimentary deposits, such as coal, kaolin, bentonite, diatomite, and zeolite, were formed. The Tertiary Pohang basin in South Korea shows basin geology, magmatism, and mineralization similar to those of North Korea. The Phanerozoic geotectonics of the peninsula are characterized by the evolution of the structural basins and violent magmatism. The peninsula is located on the Amur plate, bounded by the Philippine plate, Pacific plate, and Eurasian plate. Since Phanerozoic, the peninsula's geographic position created an important tectonic link between northeastern China and the Japanese Islands throughout geotectonic evolution. [ABSTRACT FROM AUTHOR]

The article offers information on the German Geological Society (DGG) was founded in Berlin 172 years ago, in December of the revolution of 1848. Topic include during the middle of the 19th century, Berlin was, next to Freiberg, the geoscientific centre of the German confederation, and furthermore, of continental Europe.

Published in the special issue "Advances in hydrogeologic understanding of Australia's Great Artesian Basin" The special issue starts with a comprehensive review of the GAB by B Habermehl b that includes the history of the GAB discovery and its exploration, scientific investigations (hydrogeology, hydrochemistry, isotope hydrology, groundwater modelling) and governance, and that summarizes the most recent knowledge of the GAB as a complex groundwater socio-ecological system. The GAB springs appear to be discharging water predominantly from the main GAB aquifer in the region - the J Aquifer. How much water currently recharges GAB aquifers and how much is lost in surface and shallow subsurface processes, have been long-standing questions that need to be considered when modelling and managing GAB groundwater resources. [Extracted from the article]

The investigated area comprises the 300-500 km-wide passive margin offshore Mid Norway as well as the 70-40 km-wide margin northwest of the Lofoten-Vesterålen archipelago. Following the Caledonian Orogeny, Greenland was close to Mid Norway and central-northern Norway. The orogeny climaxed with the Early Devonian continent collision with subduction of the Baltic craton beneath Laurentia, and a mountain range several kilometres high evolved. The mountain range remained a positive topographic element throughout the Late Palaeozoic and Early Mesozoic. Non-marine Carboniferous sediments were deposited onshore East Greenland, but there is no evidence of sedimentation during this period offshore Mid Norway. Three significant rift episodes, i.e., Late Permian-Early Triassic, Middle-Late Jurassic and Campanian-Paleocene are evident, with intervening (c. 70 Ma) periods of overall tectonic quiescence. Permo-Triassic sediments, 4000-6000 m in thickness, were deposited in an eastern basin area juxtaposed against basement across large normal faults close to the Norwegian mainland. The topography created by the Late Permian-Early Triassic rift episode became levelled during the Middle Triassic, and younger sediments were deposited over a relatively flat area represented by the present Trøndelag Platform and the Halten and Dønna terraces. Due to Jurassic extension there was a change to a setting where the Halten and Dønna terraces became separate structural entities, down-faulted and with a complex basin-floor topography. Until the climax stage of the Jurassic rift episode, the Caledonian mountain range might have occupied the area between the Halten Terrace and Liverpool Land, at the east coast of Greenland. The subaerially exposed land mass was eroded and acted as an important sediment source. Middle and Lower Jurassic, but also Triassic sediments entering into the basin from the west contain conglomerates and pebbly sandstones deposited under fluvial, deltaic and marginal marine conditions, and clinoforms are recorded along the basin margin on the western Halten Terrace. The largescale paleogeography was a central basement high, which separated the basin onshore East Greenland and the basin area offshore Mid Norway. Due to erosion and accelerated Late Jurassic rifting the basement high ceased to exist as a source area, leaving the narrow Sklinna Ridge as an easternmost remnant in the footwall of the Klakk Fault Complex. This stage of development is regarded as the first indication of a large and continuous marine basin between Mid Norway and Greenland after the Caledonian Orogeny. [ABSTRACT FROM AUTHOR]

Abstract The NNW-SSE trending Mariánské Lázně Fault (MLF) zone is situated in the western part of the Bohemian Massif (Czech Republic, central Europe) and controls the eastern limit of Cenozoic Cheb Basin. The Cheb Basin is well-known for present-day earthquake swarms, with maximum magnitude not exceeding Mw 4.0, and abundant occurrences of mantle-derived carbon-dioxide emanations. The MLF borders the Cheb Basin towards the Krušné hory Mts. controlling their morphologically pronounced mountain front. However, no large earthquakes required for forming the tectonic morphology (Mw > 6) have been recorded historically. To examine if potential pre-historic earthquakes contributed to mountain front formation along the MLF and to Late Quaternary seismic hazard in the region, we excavated a trench at the Kopanina site where the fault was identified by geomorphological and geophysical surveys. The trench revealed repeated movements along several fault strands within the MLF of various ages, which displaced basin sediments deposited since the Oligocene. The youngest faults cut and deformed Holocene layers at least twice, with a total cumulative vertical displacement on the main fault 0.5 m. The deformations that we documented here suggest transpression within the MLF during Holocene. Based on empirical relationships between magnitude and displacement/rupture length, the MLF has produced earthquakes with a minimum magnitude of Mw = 6.5. The youngest event is dated approximately to the period 792–1020 CE. To match the youngest event with a historical earthquake, several candidates could be considered and further investigated, but the most probable one seems to be the earthquake reported in catalogs for 998 CE. Hence our study revealed the youngest proven surface faulting in central Europe and the largest Holocene event reported so far for the Bohemian Massif, which is of great importance for seismic hazard re-assessment for the broader, slowly moving region. Highlights • Shallow geophysics traced the Mariánské Lázně fault (MLF) on surface and at depth. • Geomorphic mapping and stream-length index revealed morphological expression of MLF. • Two Holocene earthquakes of Mw = 6.3–6.5 were identified in geological record. • The latest surface-breaking event on MLF was dated by 14C method to interval from 792 to 1020 CE. • We discovered the largest historical events reported to date for the Bohemian Massif. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The ∼2.0 Ga Kongling mafic dikes are the oldest mafic intrusions in South China. • These dikes were formed in a back-arc basin during the assembly of Columbia supercontinent. • The linkage between South China and Northwest Laurentia, Northwest Australia and Siberia needs to be re-examined. Abstract Paleoproterozoic mafic dikes from the Kongling Complex in South China provide an ideal opportunity to examine mantle properties and tectonic evolution of the Yangtze Block and thus to understand the paleo-position of South China in the Columbia supercontinent. The 2.0 Ga dikes are the oldest mafic intrusions identified in the Yangtze Block by far. Samples from the dikes consist of fine to medium-grained dolerite and have variable SiO 2 (43.48–52.61 wt%) and MgO contents (3.17–7.35 wt%). They are enriched in LREE and show slightly negative to positive Eu anomalies (Eu/Eu∗ = 0.85–1.06). Their primitive mantle-normalized trace element patterns are characterized by enrichment of large-ion lithophile elements (Rb, Ba, Pb) and depletion of high-field-strength elements (U, Nb, Ta, Ti). Rocks from the dikes have variable initial 87Sr/86Sr ratios (0.698874–0.710753), εNd values (−3.0 to +4.1) and zircon εHf values (−2.7 to +3.4). These geochemical features indicate that their parental magmas were formed by <10% partial melting of a spinel-bearing lherzolite mantle in a back-arc basin setting. Paleoproterozoic mafic rocks from South China, Northwest Laurentia, Northwest Australia and Siberia had different trace element ratios and crystallization ages, their mantles had different thermal states. Thus, we argue against the previous model that the four continents were assembled together in the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Triassic detritus in the northwestern Ordos were mostly sourced from the Alxa Massif. • Post-collision related basin formed in the northwestern Ordos at Middle-Late Triassic. • The Alxa Massif was the western extension of the North China Craton during Triassic. Abstract The Helanshan Tectonic Belt is situated among the Qilian Orogenic Belt to the southwest, the Alxa Massif to the west and the Ordos Block to the east. The Helanshan Tectonic Belt has received increasing attention since it was argued as the plate boundary separating the Alxa Massif from the Ordos Block, and hence Alxa Massif was isolated from the North China Craton during Triassic. The Middle to Upper Triassic strata in the northwestern Ordos and the Helanshan Tectonic Belt witnessed the tectonic evolutionary processes between the Alxa Massif and the Ordos Basin, hence are pivotal to understand the relationship between the Alxa Massif and the North China Craton. In this work, integrated paleocurrent orientation, gravel component, sandstone modal composition and detrital zircon U–Pb isotopic analyses were applied to trace the source area and reconstruct the source-to-sink relations between the Alxa Massif and Ordos Basin. The southeast orientated paleocurrent directions suggest detritus in the northwestern Ordos were mostly sourced from the northwest. Clastic compositions reveal a mixed orogeny provenance, including magmatic arc and continental block sources. Detrital zircons from four sandstones in the Helanshan Tectonic Belt yields four major LA-ICPMS U-Pb age groups of 2600–2200 Ma, 2000–1700 Ma, 480–400 Ma and 350–200 Ma, suggesting multiple-sourced provenance. Comparing to the magmatic records in the Alxa Massif and the Qilian Orogenic Belt, the Triassic detritus in the Helanshan Tectonic Belt were mainly from the Alxa Massif with additional supplements from the Qilian Orogenic Belt, which finally debouched to the lacustrine in the interior Ordos Basin to the southeast. Triassic basin evolution of the northwestern Ordos was further associated with post-collision in the Alxa Massif after the closure of the Paleo-Asian Ocean. [ABSTRACT FROM AUTHOR]

Abstract An important exploration breakthrough has been achieved in the western subsag of the Bozhong subbasin, but the hydrocarbon accumulation mechanism was not clear. The hydrocarbon migration and accumulation mechanism of the western subsag of the Bozhong subbasin is discussed based on the modeling of hydrocarbon migration pathways and the study of late-stage reactivation of neotectonic faults. Three processes for lateral petroleum migration and accumulation can be recognized in the studied area: 1) migration and accumulation along the T8 unconformity; 2) migration and accumulation within the Guantao Formaiton (N 1 g); and 3) interaction of migration and accumulation along the T8 unconformity and Guantao Formation (N 1 g). The reactivation of faults in the studied area began 5.1 Ma. Following hydrocarbon lateral migration, late-stage reactivated neotectonic faults serve as effective vertical conduits for hydrocarbon migration and accumulation into the shallow Minghuazhen Formation (N 1 m) reservoirs. The modeling results of preferential petroleum migration pathways (PPMPs) and favorable accumulation areas are consistent with the actual exploration results. Two kinds of potential exploration targets can be predicted in the northwestern Bozhong subbasin: the first kind is hydrocarbon accumulation areas near or within generative kitchens (e.g. Target 1); the other kind is hydrocarbon accumulation areas removed from the generative kitchens, but with hydrocarbon sourcing from multiple generative kitchen and numerous PPMPs (e.g. Target 2). Studying preferential petroleum migration pathways will help reduce exploration risk. Highlights • The T8 unconformity and Guantao Formation (N 1 g) carrier beds are favorable hydrocarbon lateral migration conduits. • Late-stage reactivated faults during neotectonism serve as favorable conduits for vertical hydrocarbon migration. • Proven oil fields usually have multiple generative kitchens and numerous preferential petroleum migration pathways. • Potential exploration targets can be predicted based on preferential petroleum migration pathways. [ABSTRACT FROM AUTHOR]

Abstract The plate tectonics theory established ~ 50 years ago has formed a solid framework for understanding how the earth works on all scales. In this theory, movement of the tectonic plates relative to the subjacent asthenosphere is one of the fundamental tenets. However, the nature of the boundary between the lithosphere and asthenosphere (LAB) beneath ocean basins remains under debate. The current consensus is that the oceanic lithosphere thickens with age by accreting asthenosphere material from below, and reaches its full thickness (L) of ~ 90 km at the age (t) of ~ 70 Ma. This lithospheric thickening fits the relation L ∝ t 1/2, consistent with conductive cooling to the seafloor. A puzzling observation is that although conductive cooling continues, the oceanic lithosphere ceases to grow any thicker than ~ 90 km when t > 70 Ma. Small scale convection close beneath the LAB has been generally invoked to explain this puzzle, but why such convection does not occur until L ~ 90 km at t > 70 Ma has been a matter of conjecture. In this paper, we summarize the results of many years of experimental petrology and petrological studies of oceanic basalts, which indicate consistently that the LAB is a petrological phase boundary marking the intersection of the geotherm with the solidus of amphibole (pargasite)-bearing peridotite. That is, petrologically, the LAB is an isotherm of ~ 1100 °C with L ∝ t 1/2 for t < 70 Ma and an isobar of ~ 3 GPa (~ 90 km) for t > 70 Ma. This unifying concept explains why the LAB depth increases with age for t < 70 Ma and maintains constant (~ 90 km) for t > 70 Ma. The LAB, that is intrinsically determined by petrological phase equilibria, does not require small-scale convection. However, because the mantle above the LAB is the conductive lithosphere (pargasite-bearing peridotite) and below the LAB is the viscosity-reduced convective asthenosphere (peridotite + incipient melt), the small-scale convection in the asthenosphere close beneath the LAB (~90 km) under older (t > 70 Ma) seafloors becomes possible, whose convective heat supply balances the conductive heat loss, maintaining the constant heat flow, seafloor depth and lithosphere thickness. Highlights • The lithosphere-asthenosphere boundary (LAB) beneath ocean basins is the dehydration solidus of pargasite (amphibole), whose stability defines the lithosphere with T ≤ ~ 1100°C, P ≤ ~ 3 GPa (~ 90 km) and H 2 O < 0.02 wt%; • The LAB is an isotherm with T ≈ 1100°C, whose depth L increases with age t , i.e., L α t 0.5 for t < ~ 70 Ma because of conductive cooling to the seafloor; • The LAB is an isobar at P ≈ 3 GPa (~ 90 km) for t > ~ 70 Ma, above which is the conductive lithosphere and below which is the convective asthenosphere, explaining why the lithosphere cannot grow any thicker when t > ~ 70 Ma and making sub-LAB convection possible. [ABSTRACT FROM AUTHOR]

Highlights • Explore characteristics of strain fields of Weihe basin region and surrounding areas. • Detect variations of differential motions within the region. • Illustrate variations of crustal strain fields through establishing sound kinematic models. • Discuss correlation between the maximum shear strain fields and the seismicity. • Reveal recent geodynamics processes of the region. Abstract The Weihe Basin in central China is characterized by its complex geological background and intense tectonic activity. This study examined the characteristics of the crustal deformation and strain field of the Weihe Basin and its surroundings based on campaign Global Positioning System (GPS) data acquired during 2001–2011. We first analyzed the variations of crustal movement and we calculated the crustal strain rates by establishing sound strain models. Both the characteristics of the strain field and the correlation between the maximum shear strain field and the distribution of seismicity were investigated. Our results indicated that the overall crustal movement of the Weihe Basin region was temporally continuous during 2001–2011, despite short-term fluctuation during 2007–2008. We found that western and eastern parts of the Weihe Basin region presented considerably different tectonic characteristics with predominantly compressional strain in the west and extensional strain in the east. However, the magnitude and direction of the overall crustal movement, and the relative differential motions of the Weihe Basin region, changed obviously during 2007–2008 with substantially increased compressional strain in western areas. We conclude that regions with higher shear strain are also those with frequent earthquakes, the distribution of which might have been affected by the M8.0 Wenchuan earthquake in May 2008. According to variations of the crustal deformation and the strain field, we further infer that western parts of the Weihe Basin region during 2007–2008 might have been affected by a northeastward extrusion caused by the Wenchuan earthquake. However, this dynamic effect might have gradually permeated to eastern parts of the Weihe Basin region during 2008–2011. The results obtained in this paper not only portray the current tectonic activity deformations but also the recent geodynamic processes of the Weihe Basin and its surrounding area. [ABSTRACT FROM AUTHOR]

Paleopiezometry provides an access to the past stress magnitude, key to better understand the behaviour of the earth's crust over long period of time. This contribution presents a review of some paleopiezometric techniques that can be used in the diagenetic domain, in fold-and-thrust belts and sedimentary basins. Calcite twinning and stylolite roughness techniques have been selected and are presented through a critical description of their methodologies, along with approaches to further reconstruct the complete effective stress tensor. Major geological lessons learned over the past decades from published studies are summarized and discussed along with a way forward to potential breakthroughs. [ABSTRACT FROM AUTHOR]

Offshore Ireland, the North Atlantic opening is generally interpreted as successive, 10-to-15-Myr-long, rifting events during the Mesozoic. However, their interaction is poorly documented in terms of structural inheritance and fault reactivation. From extensive seismic and well data in the northern Porcupine Basin, we show that extension actually evolved over an abnormal period of ca. 220 Myrs with overlapping tectonic stages that, all together, reflect the Irish Atlantic Margin construction from the Palaeozoic. During the Carboniferous, extension initiated throughout the Variscan and Caledonian thickened crusts and controlled the deposition of generally slightly-tilted, continental clastics. Two subsequent rifting events, during the Triassic-Lower Jurassic and Upper-Jurassic-Lower Cretaceous, controlled shallow-to-deep marine sedimentation in separated sub-basins that progressively widen and connect once extension localised along bounding faults. We propose that extensional tectonics, first controlled by a general orogenic collapse reflecting an early stage of stretching, is then followed by several rifting periods that ultimately evolved toward the hyper-thinning of the margin and shaped an aborted rift propagator. This evolution is due to pre-existing orogenic-related structures and boundary conditions variations. Such a continuum of deformation, although pulsed, implies varying structural interactions of crustal scale that are often recorded in syn-tectonic sediments. [ABSTRACT FROM AUTHOR]

During the structural modelling of inverted basins influenced by magmatism is very important understand the geometric and kinematic relationships between inverted structures and intrusive bodies. The northern Chile is a natural laboratory to analyze this situation, since its Cenozoic tectonic evolution was marked by the tectonic inversion of Mesozoic extensional basins, which occurred simultaneously with the emplacement of km-scale intrusions. In order to provide insights on the interplay between basin inversion and magma emplacement, we completed a comparative analysis based of field data from four inverted Mesozoic basins of northern Chile and a series of previous and new analogue models reproducing the tectonic inversion of half-grabens and magma emplacement. The experiments showed that the magma migration and emplacement is controlled by the initial distribution of normal faults and occur preferentially along the inverted normal faults. High magma injection rate can cause a major reactivation of the normal faults, favoring a comparatively increase in bulk shortening. The most favorable condition for which the magma reaches the surface is under simultaneous high magma injection and shortening rates. The latter allow the magma to be emplaced along the core of inversion related anticlines such as it is recognized in northern Chile. [ABSTRACT FROM AUTHOR]

This study focused on well-preserved fluvial terrace sequences that span the past 100 ka in the Guide, Jianzha, and Xunhua basins along the Yellow River that drained the northeastern Tibetan Plateau. New geomorphic, stratigraphic, sedimentologic and chronologic data from twelve depositional sequences within terraces yielded better constraints on rates of incision, degradational and aggradational phases for the Yellow River. Age control was established by sixteen OSL ages on quartz grains from fluvial sediments. Three fluvial aggradational phases were identified between 100 and 80 ka, 53 and 40 ka and 21 and 12 ka associated with terrace levels respectively at 120 to 95, 61 to 45 and 25 to 15 m above river level. These aggradational phases reflect multiple processes including enhanced fluvial discharge, sediment availability with glaciation, deglaciation and increased monsoonal precipitation. The initiation of fluvial degradation was linked to mega-floods released from landslide-dammed lakes at ca. 76, 38, and 16 ka, though these changes may also reflect variations in sediment-load discharge relations with climate change. The apparent net incision rate is 1.13 ± 0.11 mm/yr for the past 100 ka and is consistent with late Cenozoic tectonic uplift rates >0.5–2 mm/yr and recent GPS-based rates. The fluvial dynamics of the upper reach of the Yellow River was variably controlled by climate-induced changes in discharge sediment-load relations on stadial to interstadial timescales, episodic mega-floods from the breach of landslide dams, and with net incision in the past 100 ka in response to tectonic uplift of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The SW Barents Sea is an epicontinental platform consisting of N- to NNE-oriented basins separated by basement highs. The basins were formed during four distinct rift-phases in the Carboniferous, Late Permian, Late Jurassic-Early Cretaceous, and Paleocene-Eocene. Progressive rifting culminated in continental breakup and seafloor spreading along the North Atlantic axis approximately at 55 Ma. We present tectonic and thermal models of basin evolution along two seismic profiles crossing the SW Barents Sea. The thermal and isostatic history of basins is constrained through time-forward basin modelling based on an automated inverse basin reconstruction approach. We estimate the effects of continental breakup and near-margin processes (magmatic underplating and sill intrusions) on the thermal history and kerogen maturity below the Vestbakken Volcanic Province. Basin models are calibrated against well data. The results imply that both breakup and underplating alter the thermal and isostatic history of sediments along the margin. The hydrocarbon potential of source rocks modelled along the margin suggests breakup has a permanent thermal effect on the present-day sediments promoted by lateral heat flow, while heat conduction by underplating is more diffuse, inhibited to some degree by deeply-buried, low-conductivity shales and limestones. [ABSTRACT FROM AUTHOR]

We examine three-dimensional seismic data from the Santos Basin, offshore Brazil, to determine how, where, and when radial faults grow near a salt diapir. We show roof stretching alone cannot account for the large heights and lengths of the kilometer-scale radial faults, suggesting stock widening ('stem push'), a mechanism implied in numerical models but not yet recognized in natural examples, played a pivotal role in fault formation. We suggest that, when a diapir is covered by a roof, radial faults form due to roof stretching, extending no further than the limit of the drape folding. The roof may then be shouldered aside and the faults buried along the stock flanks, exposing these strata to stem push-related stresses that may then re-activate preexisting, or form new, radial faults. We suggest the causal mechanism for radial fault formation will likely change as roof thickness varies during diapirism, with this reflecting the ratio between sedimentation rate and salt volumetric flux. [ABSTRACT FROM AUTHOR]

The south-central portion of the Columbia Basin in Washington State (USA), although not the primary eruptive center for the Columbia River Basalt (CRB), contains the thickest package of CRB lavas, at over 4 km. Prior to CRB deposition the region was a sediment-filled rift basin dating back to the early Eocene. Previous studies interpret a lower-crust, high-velocity body below the thick basalt deposits as a syn-extensional magmatic underplate. CRB layers thicken toward the center of the basin, revealing a pulse of subsidence during deposition that ceased coincident with cessation of CRB eruptions. We propose a subsidence mechanism based on metamorphic transition of the underplate from basalt to eclogite facies, driven by the increased pressure of CRB loading. We demonstrate the plausibility of our interpretation using numerical models of the mechanical and chemical components of the system. Further, we constrain the effective elastic thickness of the Miocene Columbia Basin lithosphere, finding it to be much thinner (5-10 km) than previous estimates. [ABSTRACT FROM AUTHOR]

Initiation of subduction is rarely encountered in modern tectonic environments due to its ephemeral and destructive nature. We report the geological and geophysical evidence indicating a transitional phase from buckling to embryonic subduction along the eastern Korean margin. The transition appears to be caused by compressional reactivation of the strike-slip boundary between the continental (Korean Peninsula) and oceanic (Ulleung Basin) crusts since the Early Pliocene. Evidence for compressional reactivation includes (1) a west-dipping major thrust and coincident crustal buckling of the Ulleung Basin; (2) an east-west structural asymmetry inferred from the gravity anomaly and P-wave tomography; and (3) ongoing crustal uplift and high-angle faults along the eastern Korean margin. The juxtaposition of underthrusting and buckling of the crust in the Ulleung Basin, and its associated ubiquitous reverse faulting on the eastern Korean margin, imply the potential development of a new subduction system along the western margin of the East Sea (Japan Sea). We propose that the East Sea comprises two incipient subduction margins (i.e., the Korean and Japanese sides), which are now competing to reach a self-sustaining subduction stage. [ABSTRACT FROM AUTHOR]

Abstract: The discrepancy between the size of the Apenninic chain and the depth of the Adriatic foredeep is investigated using 2D flexural backstripping on well‐constrained depth‐converted cross‐sections in the Pescara basin (Central Italy). The procedure consisted of removal, uplift, unfolding and unfaulting of the Pliocene–Pleistocene foreland deposits to produce a palaeogeographic map of the basin at the end of the Messinian and to constrain sedimentary rates since the Miocene. Results are found to support the contribution of an external load to the foreland evolution together with the Apenninic chain load. The interplay of the two types of loads resulted in spatial and temporal variations of the foredeep evolution that are quantified by palaeogeographic maps and sedimentation rates obtained through backstripping. Results are interpreted as representing the effects of a southward‐migrating wave linked to slab detachment beneath the Adriatic foredeep. This procedure can be useful to investigate similar problems on other chains worldwide. [ABSTRACT FROM AUTHOR]

The 492 km-diameter Apollo impact basin post-dates, and is located at the inner edge of, the ∼2240 km-diameter South Pole–Aitken (SPA) basin, providing an opportunity to assess the SPA substructure and lateral heterogeneity. Gravity Recovery and Interior Laboratory gravity data suggest an average crustal thickness on the floor of SPA of ∼20 km and within the Apollo basin of ∼5 km, yet remote sensing data reveal no conclusive evidence for the presence of exposed mantle material. We use the iSALE shock physics code to model the formation of the Apollo basin and find that the observational data are best fit by the impact of a 40 km diameter body traveling at 15 km/s into 20–40 km thick crustal material. These results strongly suggest that the Apollo impact occurred on ejecta deposits and collapsed crustal material of the SPA basin and could help place constraints on the location, size and geometry of the SPA transient cavity. The peak ring in the interior of Apollo basin is plausibly interpreted to be composed of inwardly collapsed lower crustal material that experienced peak shock pressures in excess of 35 GPa, consistent with remote sensing observations that suggest shocked plagioclase. Proposed robotic and/or human missions to SPA and Apollo would present an excellent opportunity to test the predictions of this work and address many scientific questions about SPA basin evolution and structure. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Pamir bears essential information for understanding intracontinental tectonic processes within the context of India-Asia convergence. However, it is unclear whether the arcuate shape of the Pamir is entirely the result of the India-Asia collision, or may have been in part an inherited, pre-Cenozoic feature. In this study, we address the evolution of the NE Chinese Pamir during the Paleogene by reviewing the stratigraphy of twelve sections in the western Tarim Basin and the establishment of sedimentary facies. The results indicate three episodes of deposition of alluvial coarse sediments in the foreland regions of NE Chinese Pamir during the (1) early Paleocene, (2) late Paleocene to early Eocene and (3) middle Eocene to Oligocene, respectively. These are correspondingly attributed to (1) retroarc deformation in an Andean-type margin of the southern Asia during subduction of the Neo-Tethys Ocean, (2) the immediate response in the Pamir to the India-Asia collision, and (3) continued India-Asia convergence. The alluvial conglomerates with grain-size up to 5–10 cm, imply a transport distance <60 km from the fan apex. This result, together with the 20–50 km northward thrust displacements, suggests that the orogen/basin boundary between the Pamir and the Tarim-Alai Basin was located less than ca. 80–110 km to the south from the present location of the Main Pamir Thrust during the Paleogene, indicating the arcuate shape of the Pamir was already largely established by the Paleogene, rather than entirely a result of the India-Asia continental collision. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the transition zone from the Pacific Ocean to the Atlantic Ocean is closely linked with the destruction of the American-Antarctic continental bridge in the Scotia Sea. The western segment of the bridge combines the Terror, Pirie, and Bruce banks, as well as the Protector and Dove basins between them. Modeling—primarily based on original geological and geophysical materials—of linear magnetic anomalies and calculation of the floor kinematics in these basins have made it possible for the first time to reveal that the collapse of the western segment of the American-Antarctic continental bridge occurred 18-25 Ma ago via a two-stage separation of the Pirie Rise from the Bruce Rise with the formation of the Dove Basin and a two stage separation of the Terror Rise from the Pirie Rise with the formation of the Protector Basin. [ABSTRACT FROM AUTHOR]

Some potentially attractive reservoirs, containing anomalously thick (10s to a few 100 m), cross-stratified sandstone, have been locally encountered within both the classic regressive (lower Brent) and the transgressive (upper Brent) segments of the Brent Delta. Three documented cases of these sandstone bodies are re-examined. They are internally dominated by simple or compound dunes, and typified by two types of deepening-upward succession, recording a retrogradational or transgressive shoreline history. Type I is expressed as a single estuarine succession changing upwards from erosive, coarse-grained channelized deposits into outer estuary tidal bar deposits. The estuary is underlain and overlain by deltaic deposits. Type II lacks significant basal river deposits but is composed by stacked mixed-energy and tide-dominated estuarine deposits. It is underlain by deltaic deposits and overlain by open marine sediments. Considering the structural evolution in the northern North Sea basin, we suggest (as did some earlier researchers) that these sandstone bodies were local, but sometimes broad transgressive estuaries, formed at any time during large-scale Brent Delta growth and decay. The estuary generation was likely triggered by fluvial incision coupled with active faulting, producing variable accommodation embayments, where tidal currents became focused and deposition became transgressive. The spatial variations of the interpreted estuary deposits were linked with variable, fault-generated accommodation. The relatively simple, lower Brent estuarine units were created by short-lived, fault activity in places, whereas the complex, stacked upper-Brent estuarine units were likely a result of more long-lived, punctuated fault-induced subsidence leading into the northern North Sea main rifting stage. The thick cross-stratified units potentially accumulated in the hangingwall of large bounding faults. [ABSTRACT FROM AUTHOR]

The basement structure of the Cenozoic Enping Sag, within the Pearl River Mouth Basin on the northern margin of South China Sea, is revealed by borehole-constrained high-quality 3D seismic reflection data. Such data suggest that the Enping Sag is bounded in the north by a low-angle normal fault. We interpret this low-angle normal fault to have developed as the result of the reactivation of a pre-existing thrust fault part of a pre-Cenozoic thrust system. This is demonstrated by the selective reactivation of the pre-existing thrust and by diffuse contractional deformation recognized from the accurate analysis of basement reflections. Another significant result of this study is the finding of some residual rift basins within the basement of the Enping Sag. Both the thrust system and the residual basins are interpreted to have developed after the emplacement of continental margin arc-related granitoids (J 3 –K 1 ) that define the basement within the study area. Furthermore, seismic sections show that the pre-existing residual rift basins are offset by the main thrust fault and they are both truncated by the Tg unconformity. These structural relationships, interpreted in the frame of previous studies, help us to reconstruct a six-event structural evolution model for the Enping Sag from the late Mesozoic to the early Cenozoic. In particular, we interpret the residual rift basins to have formed as the result of back-arc extension due to the slab roll-back of the Paleo-Pacific Plate subduction in the early K 2. The thrust system has recorded a compressional event in the late K 2 that followed the back-arc extension in the SCS area. The mechanism of this compressional event is still to be clarified, and might be related to continuous subduction of the Paleo-Pacific Plate or to the continent-continent collision between a micro-continental block and the South China margin. [ABSTRACT FROM AUTHOR]

Loess deposits and deserts are regarded as coupled geological systems and loess deposits on the periphery of deserts can often be used to reconstruct desert evolution. Previous studies of desert evolution in Asia are mainly concentrated in northwest China and the China Loess Plateau, and little is known about long-term desert evolution in east China. In this study, we selected the Sishijiazi loess section in the Chifeng area in northeast China to study the long-term evolution of the desert in east China. A high-resolution magnetostratigraphy combined with optically stimulated luminescence dating indicated that the age of the section base is approximately 1.02 Ma. The Brunhes-Matuyama boundary is at the depth of 39.8 m in loess unit L8, and the upper boundary of the Jaramillo Subchron is at the depth of 60.8 m in paleosol S10. The results of grain-size analysis indicate a coarsening grain-size trend in the past 1.0 Ma. In addition, based on grain-size variations, the desert evolution in east China since ∼1.0 Ma can be divided into three stages: stability from 1.0 to 0.8 Ma, desert recession from 0.8 to 0.5 Ma, and gradual expansion since 0.5 Ma. Our results further indicate that the evolution of desert in east China was mainly controlled by changes in global ice volume, and that the uplift of the Tibetan Plateau may have had an additional effect. [ABSTRACT FROM AUTHOR]

In Europe, the most complete loess-paleosol sequences over the past million years are preserved in the Serbian part of the Danube River drainage basin. The similarity in stratigraphy and climatic cycles between the Serbian and the Chinese loess sequences suggests that the loess deposits in these two regions could play an important role in the study of intercontinental climatic correlations and linkage. However, previous magnetostratigraphic studies of the Serbian loess, mainly conducted using the alternating field (AF) demagnetization approach, show significant differences with the Chinese loess, especially the stratigraphic positioning of the Matuyama-Brunhes boundary (MBB). Here, we conduct a detailed magnetostratigraphic investigation of a composite Titel-Stari Slankamen loess section in the Vojvodina (northern Serbia), using thermal and hybrid demagnetization methods, aiming to establish new chronological constraints for the Danube Basin loess. Based on the analyses of the mineral magnetic properties, anisotropy of magnetic susceptibility, progressive thermal and hybrid demagnetization, the MBB was determined within S8, broadly consistent with the MBB position seen in the Chinese loess. Present evidence supports the hypothesis that the overall normal polarity in the upper part of L9, with a thickness of 2.1 m, was possibly caused by a combination of the remagnetization of remanence-carrying coarse-grained magnetite during the Brunhes normal chron and bioturbation during the forming of the overlying paleosol S8. Thus, our magnetostratigraphic results provide solid chronological evidence for the coherence of pedostratigraphy and climatostratigraphy for the loess deposits in the Danube Basin and China. The synchronous occurrence of the strongest developed paleosol S5 (corresponding to MISs 15–13) and the least weathered thick loess unit L9 (corresponding to MISs 24–22) in the two regions confirms that extreme climatic events during these two intervals are possibly common features of the climate in the Northern Hemisphere at those times. [ABSTRACT FROM AUTHOR]

A combined study of magnetic fabrics, zircon U-Pb geochronology and structural deformation was carried out for Late Paleozoic sedimentary and Mesozoic magmatic rocks in the southwestern Fujian rift basin, South China, aiming at deciphering the tectonic evolution during Late Mesozoic. Field observations showed that the Late Mesozoic structure deformations in southwestern Fujian were categorized into four phases: NW-SE compression, ENE-WSW extension, NNE-SSW compression and NNW-SSE extension, sequentially. Zircons picked out from Juzhou granite and WNW-trending diabase dykes showed complete crystal shapes and clear oscillatory zonings on their edges, and the U-Pb dating yielded ages of 132 and 141 Ma, respectively. The susceptibility ellipsoid magnitude parameters of the Juzhou granite are characterized by flaser type strain ellipsoid, with pole density center of K3 falling into the first and the third quadrants, these features revealed that the Juzhou granite formed in ENE-WSW compressional stress field, indicating the early stage of Early Cretaceous extrusion in southwestern Fujian. The late stage of Early Cretaceous NNE-SSW extension was limited by the widespread WNW-trending diabase dykes, which were usually regarded as important indications for a regional extensional setting. On the basic of the previous researches, structural deformation studies, and the deductions above, it can be concluded that southwestern Fujian experienced five main tectonic stages during Late Mesozoic: Early Jurassic extension, Middle-Late Jurassic thrusting, early stage of Early Cretaceous extension, late stage of Early Cretaceous compression and Late Cretaceous extension. [ABSTRACT FROM AUTHOR]

The Xujiaweizi (XJWZ) fault depression is a primary area for deep-seated gas exploration in Daqing. Through seismic profile interpretation, the main sag-controlling fault and structural characteristics in the XJWZ fault depression were analyzed based on folds and faults analysis. A three-dimensional geological model of the XJWZ fault depression was also set up to enable further discussion by means of structural physical modeling. According to our research, the basic structural framework of the XJWZ fault depression was the result of regional extension. Its formation and evolution were mainly controlled by the Xuxi fault. The structural framework of S-N blocking was due to changes in the fracture attitude. The Xuzhong uplift and the depressions on both sides belong to a normal-fault-related fold and were formed by controlling of the ramp/flat normal fault in the same tectonic movement period. [ABSTRACT FROM AUTHOR]

Early Cenozoic plate collision of India and Eurasia was a significant geological event, which resulted in Tibetan Plateau (TP) uplift and altered regional and global atmospheric circulations. However, the timing of initial collision is debated. It also remains unclear whether the TP was deformed either progressively northward, or synchronously as a whole. As the largest basin in the hinterland of the TP, evolution of the Hoh Xil Basin (HXB) and its structural relationship with development of the Tanggula Thrust System (TTS) have important implications for unraveling the formation mechanism and deformation history of the TP. In this study, we present results from a long sedimentary sequence from the HXB that dates the Fenghuoshan Group to ∼72–51 Ma based on magnetostratigraphy and radiometric ages of a volcanic tuff layer within the group. Three depositional phases reflect different stages of tectonic movement on the TTS, which was initialized at 71.9 Ma prior to the India–Eurasia collision. An abrupt sediment accumulation rate increase from 53.9 Ma is a likely response to tectonic deformation in the plateau hinterland, and indicates that initial India–Eurasia collision occurred at no later than that time. This remote HXB tectonosedimentary response implies that compressional deformation caused by India–Eurasia collision likely propagated to the central TP shortly after the collision, which supports the synchronous deformation model for TP. [ABSTRACT FROM AUTHOR]

The Hoh Xil Basin in the central Tibetan Plateau was the locus of thick accumulation of terrestrial sediments from the Late Cretaceous to Neogene, providing an archive of regional tectonic activity both before and after initiation of the early Paleogene India-Asia collision. This work focuses on the stratigraphy and provenance of the poorly studied western part of the Hoh Xil Basin. Lithostratigraphy, carbonate oxygen isotopic composition, and deformation features suggest that the braided river and alluvial-fan that dominated the Kangtuo Formation in the southern West Hoh Xil subbasin can be correlated with the Late Cretaceous-early Eocene Fenghuoshan Group deposits of the East Hoh Xil subbasin, whereas deltaic, shallow lacustrine, and evaporite strata of the Suonahu Formation in the centralnorthern West Hoh Xil subbasin can be correlated to the middle Eocene-early Oligocene Yaxicuo Formation of the East Hoh Xil subbasin. These observations suggest that the eastern and western parts of Hoh Xil Basin evolved as a unified basin during Late Cretaceous-Oligocene time. Detrital zircon U-Pb ages indicate that the Kangtuo Formation and Fenghuoshan Group mainly received detritus from the Qiangtang terrane to the south, whereas the age probability distributions of the Suonahu Formation and Yaxicuo Formation sandstones are more similar to zircon ages reported for the northern Qiangtang terrane and within the Hoh Xil terrane. We favor a tectonic model with Late Cretaceous-early Eocene contractional deformation and topographic growth of the south-central Qiangtang terrane that caused flexural subsidence of the south-central Hoh Xil region within a retroarc foreland basin, relative to the Tanggula thrusts in central Qiangtang. Following the onset of India-Asia collision, the locus of contractional deformation moved northward, marked by activity of the Fenghuoshan and Hoh Xil thrust systems within the Hoh Xil region, and resulting in transformation of the Hoh Xil foreland basin to a hinterland basin. We suggest that both middle Eocene to late Oligocene uppercrustal shortening and associated thickening of the lower crust and mantle lithosphere as well as late Oligocene to Miocene loss of dense mantle lithosphere contributed to the topographic growth of the Hoh Xil Basin. [ABSTRACT FROM AUTHOR]

The study and radiocarbon dating of the low alluvial terraces of the Chon-Aksuu River, in the Northern Issyk-Kul region, which were broken by the Kebin (Kemin) earthquake of 1911 (Ms = 8.2, Io = 10 to 11), are carried out. The obtained radiocarbon dated ages refer to the second half of the Holocene. Since that time, at least eight strong earthquakes took place along this (Chon-Aksuu) segment of the Aksuu border fault. Three seismic events, including the earthquake of 1911 occurred in the second millennium A.D. This outburst of seismic energy was preceded by two millennia of seismic quiescence, which set in after another pulse of seismic activation. The latter lasted for 1.5 millennia and included five strong earthquakes. The recurrence period of seismic events during the activations is 300-600 years. Hence, the seismic regime along the Chon-Aksuu segment of the Aksuu border fault in the second half of the Holocene was a succession of two seismic activations, each with a duration of 1.0-1.5 ka, which were separated by a 2-ka interval of seismic quiescence. Therefore, the absolute datings of the river terraces of different ages which have been broken by a seismogenic rupture can serve as a reliable source of information about the age of the strong earthquakes that occurred along the seismogenic fault. [ABSTRACT FROM AUTHOR]

Thermal maturity of late Pliensbachian-early Toarcian organic-rich sediments in the Grands Causses (Suèges section), Quercy (Caylus section) and Pyrenean (Pont de Suert section) basins was determined through multiple parameters, including Spore Coloration Index (SCI), hydroid random reflectance (HR r ) and spectral fluorescence of Tasmanites algae ( λ max ). The main objective of this study is to test the effectiveness and make comparisons of organic matter thermal maturity in these three sections by different techniques and particularly hydroid reflectance. For the Suèges section SCI presented a value of 3.5–4.0. HR r ranges between 0.36% and 0.47%, which corresponds to 0.45%–0.52% VR eq , and shows a good correlation with SCI values. Spectral fluorescence analysis presents a λ max of 560 nm for most samples. The fluorescence spectral maximum seems to be redshifted in comparison to other thermal maturity parameters. The Caylus section exhibited SCI of 3.5–4.0. HR r ranges between 0.32% and 0.50% corresponding to 0.42%–0.54% VR eq . Spectral fluorescence analysis points out a λ max of 560 nm, displaying a good correlation with SCI. When R eq values determined through SCI are compared with equivalent vitrinite reflectance values determined through λ max , a redshift of the fluorescence spectrum maximum is detected. For the Pont de Suert section SCI ranges between 8.0-8.5 and 8.5–9.0. HR r varies between 0.85% and 1.18% which corresponds to 0.76%–0.98% VR eq . Even though there are lower values than those obtained by SCI, VR eq is reliable and acceptable to determine the thermal evolution stage. Furthermore, HR r values also present a good correlation with SCI. These data indicate that the majority of the samples from the Suèges and Caylus sections are in the immature to early mature evolution stages and Pont de Suert section samples are in late mature to early overmature evolution stages for liquid hydrocarbons generation, supporting a very similar thermal evolution for the Grands Causses and Quercy basins and an entirely different thermal history for the Pyrenean Basin. This is in accordance with the similar tectonic and sedimentary context of the Quercy and Grands Causses basins. The Pont de Suert section, located near the collision front of the Pyrenees mountains, records a more complex sedimentary and tectonic history. In addition, this study presents the first reflectance data for Jurassic hydroids, which show a good correlation with other rank parameters. [ABSTRACT FROM AUTHOR]

The Lower Silurian Longmaxi shale is the most important marine shale gas play in South China. Several hundred wells have been drilled to date, of which more than 150 wells have obtained high initial production (IP). Outside of the Sichuan Basin, however, wells drilled in the Lower Silurian Longmaxi shale do not reach flow rates that are commercial. Developing an understanding of the key factors controlling the IPs of Longmaxi shale is important in screening shale-resource plays. In this study, the TOC, thermal maturity, porosity, and gas saturation data obtained from Longmaxi shale of southeastern Chongqing area outside Sichuan Basin have been compared with that of Sichuan Basin. The results of this study show that the shales encountered display similar properties including TOC (>2%), thermal maturity (2.5–3.5% EqRo), and total porosity (3–6%). A good correlation between IPs and pressure coefficient suggest that the free gas content of gas shale controls on IPs. Porosity and gas saturation of gas shale are the main factors to control its free gas volume. The gas saturations in Longmaxi shale from high initial production wells in Sichuan Basin mainly range between 50 and 90%, however, that of shale in the southeastern Chongqing area are decreased to 10–30%. This is the directly reason for low IPs of wells. The contrasting gas saturation of Longmaxi shale between Sichuan Basin and the adjacent fold-thrust belts are interpreted to reflect, in part, differences in sealed condition of fluid system. Intensive tectonic movements caused the exhumation, faulting and fracturing, that reduced or destroyed the sealed ability of shale fluid system, which are the major factors for enhancing water saturation, decreasing fluid pressure and IPs. Finally, the study proposes several most favorable zones for Longmaxi shale gas exploration and development. [ABSTRACT FROM AUTHOR]

The Wadi El Natrun area in Egypt is located west of the Nile Delta on both sides of the Cairo–Alexandria desert road, between 30°00′ and 30°40′N latitude, and 29°40′ and 30°40′E longitude. The name refers to the NW-SE trending depression located in the area and containing lakes that produce natron salt. In spite of the area is promising for oil and gas exploration as well as agricultural projects, Geophysical studies carried out in the area is limited to the regional seismic surveys accomplished by oil companies. This study presents the interpretation of the airborne magnetic data to map the structure architecture and depth to the basement of the study area. This interpretation was facilitated by applying different data enhancement and processing techniques. These techniques included filters (regional-residual separation), derivatives and depth estimation using spectral analysis and Euler deconvolution. The results were refined using 2-D forward modeling along three profiles. Based on the depth estimation techniques, the estimated depth to the basement surface, ranges from 2.25 km to 5.43 km while results of the two-dimensional forward modeling show that the depth of the basement surface ranges from 2.2 km to 4.8 km. The dominant tectonic trends in the study area at deep levels are NW (Suez Trend), NNW, NE, and ENE (Syrian Arc System trend). The older ENE trend, which dominates the northwestern desert is overprinted in the study area by relatively recent NW and NE trends, whereas the tectonic trends at shallow levels are NW, ENE, NNE (Aqaba Trend), and NE. The predominant structure trend for both deep and shallow structures is the NW trend. The results of this study can be used to better understand deep-seated basement structures and to support decisions with regard to the development of agriculture, industrial areas, as well as oil and gas exploration in northern Egypt. [ABSTRACT FROM AUTHOR]

The nature of the interaction between Adriatic and Euroasian lithospheric plates in the Dinarides is important for understanding the complex tectonic history of the central Mediterranean. Using the data from permanent and temporary seismic stations in the wider Dinaric region, we imaged the lithospheric and upper mantle structure under this area. Specifically, we focused on mapping the lithosphere asthenosphere boundary (LAB) using the S receiver functions in order to establish boundaries between different tectonic domains present in this region. The lithospheric thickness in the investigated area varies between ∼50 and ∼160 km with high degree of variability between adjacent tectonic realms. Below northwestern Dinarides the LAB depth varies between 100 and 120 km thinning towards Adriatic sea and Pannonian basin, to 90 and 70 km respectively. In the central Dinaric region (Lika region) we find anomalously thin lithosphere with thickness varying between 50 and 70 km and weak velocity gradient defining the LAB. Further south the signal from the LAB is more pronounced with lithosphere getting thicker again with average depths around 90 km. The intriguing observation of thinned lithosphere under central part of the Dinarides coincides with the zone of lower seismicity and with the tomographic images showing the slab gap in this area. [ABSTRACT FROM AUTHOR]

Abstract: The Xichang Basin in southeastern Tibet provides crucial information about formation and tectonic processes affecting the eastern Tibetan Plateau. To determine when and how the uplift developed, we conducted detailed studies of structures and obtained thermochronology data from the Xichang Basin and its periphery. The Xichang Basin is characterized by gentle deformation of the strata, segmented by an E‐vergent boundary thrust fault. Two stages of deformation, strike‐slip followed by an E‐W oriented shortening resulted in oblique shortening between the southeastern Tibetan Plateau and the Sichuan Basin. New apatite fission‐track data interpreted together with (U‐Th)/He data confirm a simple burial/heating and exhumation/cooling history across the Xichang Basin and its periphery. Subsidence and burial of the Xichang Basin peaked between 80–30 Ma, followed by mountain building with a protracted cooling starting at around 40–20 Ma, with rates of ca. 2.0–8.0 °C Myr−1 (i.e. 0.1–0.3 mm year−1). Our data indicate that the Xichang Basin has experienced ca. 2.5–5 km of exhumation, much more intensive than the ca. 1–2 km of exhumation inferred for the southwestern Sichuan Basin. Restored balanced cross‐sections of post‐Late‐Triassic strata along a ca. 250 km traverse indicate ca. 10–20% east‐west shortening strain (i.e. ca. 20–30 km) at the southeastern Tibetan Plateau during Cenozoic time. Study of crustal thickening and erosion supports a tectonic shortening mechanism to account for the uplift of the Xichang Basin on the southeastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The Meso-Cenozoic lithospheric thermal-rheological structure and lithospheric strength evolution of the Jiyang sub-basin were modeled using thermal history, crustal structure, and rheological parameter data. Results indicate that the thermal-rheological structure of the Jiyang sub-basin has exhibited obvious rheological stratification and changes over time. During the Early Mesozoic, the uppermost portion of the upper crust, middle crust, and the top part of the upper mantle had a thick brittle layer. During the early Early Cretaceous, the top of the middle crust's brittle layer thinned because of lithosphere thinning and temperature increase, and the uppermost portion of the upper mantle was almost occupied by a ductile layer. During the late Early Cretaceous, the brittle layer of the middle crust and the upper mantle changed to a ductile one. Then, the uppermost portion of the middle crust changed to a thin brittle layer in the late Cretaceous. During the early Paleogene, the thin brittle layer of the middle crust became even thinner and shallower under the condition of crustal extension. Currently, with the decrease in lithospheric temperature, the top of the upper crust, middle crust, and the uppermost portion of the upper mantle are of a brittle layer. The total lithospheric strength and the effective elastic thickness ( T ) in Meso-Cenozoic indicate that the Jiyang sub-basin experienced two weakened stages: during the late Early Cretaceous and the early Paleogene. The total lithospheric strength (approximately 4-5 × 10 N m) and T (approximately 50-60 km) during the Early Mesozoic was larger than that after the Late Jurassic (2-7 × 10 N m and 19-39 km, respectively). The results also reflect the subduction, and rollback of Pacific plate is the geodynamic mechanism of the destruction of the eastern North China Craton. [ABSTRACT FROM AUTHOR]

Meta or hybrid attributes extracted from seismic data through artificial neural networks enhance structural details in subsurface strata. Cretaceous units within the Penobscot prospect are devoid of such interpretations. Although these units are plausible zones for hydrocarbon generation and accumulation, the role of geologic structures responsible for such entrapment is poorly understood. The present study enlightens these latter geological structures through a case study that uses 3D time-migrated seismic data from the Penobscot prospect in the Scotian Basin. A modern data conditioning approach, used together with multi-attribute analyses and a supervised neural network, have brought out the minute details of subsurface geologic structures through a hybrid attribute, called the fault probability cube (FPC). The present fault displacement analysis reveals that the major fault of the prospect has evolved by the coalescence of different fault segments grown over space and time, and has demonstrated a predominant NNW-SSE structural trend. Such a geometry has structurally modulated the Cretaceous units (the Logan Canyon, the Dawson Canyon and the Wyandot Formations) giving rise to different horst-graben structures and fracture networks, as shown by the FPC attribute. This generates complicated structural deformation and accommodation space, thereby enabling different trapping zones for hydrocarbon accumulation within these units. Such a detailed structural understanding will provide significant input to the future exploration and development programme in the Penobscot prospect. [ABSTRACT FROM AUTHOR]

Detailed structural investigations have been carried out in the Pevek district to specify tectonic evolution of the Chukotka mesozoids. The earliest south-verging folds F1 formed in Triassic rocks at the first deformation stage DI. These structures are overlapped by the northern-verging folds F and overthrusts pertain to the second deformation stage DII. Folding structures F and F were deformed by shear folds F, completing stage DII. The DI and DII structures are complicated by roughly NS-trending normal faults marking deformation stage DIII. It has been established that DI is related to the onset of opening of the Amerasian Basin in the Early Jurassic, or, alternatively, to the later accretion of the Kulpolnei ensimatic arc toward the Chukotka microcontinent. DII marks the collision of Siberia and the Chukotka microcontinent in the Late Neocomian. Normal faulting under the roughly E-W-trending extension during DIII is likely related to rift opening of the Podvodnikov and Makarov-Toll basins in the deep Amerasian Basin. Formation of the Okhotsk-Chukotka volcanoplutonic belt completed the structural evolution of the studied region. [ABSTRACT FROM AUTHOR]

The aim of the present work is to determine the morphological characteristics of the lower Aptian (lower Cretaceous) ammonite species Cheloniceras cornuelianum (d’Orbigny, 1841) (Douvilleiceratinae, Douvilleiceratidae) on the basis of 32 specimens from the Paris Basin (France), including the lectotype of the species and 23 topotype specimens. It is generally admitted that this species occurs in the Deshayesites forbesi - Dufrenoyia furcata zones interval (lower Aptian). Our study has lead to several unexpected results. First, the study sample of C . cornuelianum is very probably younger and has more primitive traits than expected: it is probably dated around the limit between the Deshayesites forbesi and Deshayesites deshayesi zones and is morphologically close to the earlier genus Procheloniceras Spath, 1923. Secondly, the lectotype is an extreme specimen with much derived traits compared to its original population. It constitutes an example of type-specimen not morphologically representative of its original population, responsible of a risk of misinterpretation of the species. Finally, the intraspecific variability and the proportion of asymmetric specimens of the study sample of C . cornuelianum are very important but there is no evidence of sexual dimorphism. [ABSTRACT FROM AUTHOR]

The Apan-Acoculco area is located in the eastern portion of the Mexico basin and the Trans-Mexican Volcanic Belt. The area is transected by right-stepping variably dipping NE-SW normal faults. The Apan-Tlaloc Fault System is a major discontinuity that divides the region into two contrasting areas with different structural and volcanic styles. a) The western area is characterized by a horst-graben geometry with widespread Quaternary monogenetic volcanism and scattered outcrops of Miocene and Pliocene rocks. b) The eastern area is dominated by tilted horsts with a domino-like geometry with widespread Miocene and Pliocene rocks, scattered Quaternary monogenetic volcanoes and the Acoculco Caldera. Gravity data suggest that this structural geometry continues into the Mesozoic limestones. Normal faulting was active since the Pliocene with three stages of extension. One of them, an intense dilatational event began during late Pliocene and continues nowadays, contemporaneously with the emplacement of the Apan-Tezontepec Volcanic Field and the Acoculco caldera. Statistical analysis of cone elongation, cone instability, and the kinematic analysis of faults attest for a NW50°SE ± 7° extensional regime in the Apan-Acoculco area. The activity in some portions of the Apan-Tlaloc Fault System continues today as indicated by earthquake swarms recorded in 1992 and 1996, that disrupted late Holocene paleosols, and Holocene volcanism. [ABSTRACT FROM AUTHOR]

Post-orogenic extension is the last stage of a tectonic process towards the end of each Wilson cycle in both ancient and modern continental collisional zones, but their dynamics, controlling factors, and roles for the post-orogenic extension processes remain debatable. We present the first two-dimensional thermo-mechanical numerical model of double sutures inspired by the Western Dabie Orogen to investigate the dynamics of post-orogenic extension. Our results indicate that the pro-continent re-subduction can delay or stop regional extensional deformation and subsequent voluminous magmatic activity caused by slab breakoff in the collision zone. After the end of the collision stage, the re-subduction slab under the residual lithosphere in the model with lower convergence, as a strong unit, can maintain the gravitational balance of the whole post-orogen system, whether crust eclogitization is considered or not. If the oceanic crust and micro-continental crust eclogitization are applied to the model with medium convergence, the lower crust and the residual lithospheric mantle in the collision zone will be completely removed by the gravitational instability and upwelling of asthenospheric mantle. The lithospheric architecture of this model with the medium convergence and crust eclogitization is very similar to the present-day tomography. However, in the model with higher convergence, lithosphere delamination can occur only by upwelling of asthenosphere, whether crustal eclogitization is considered or not. On the basis of a comparison of numerical results with field data from the Western Dabie Orogen, we suggest that the dynamics of post-orogenic extension in the Western Dabie Orogen is controlled by re-subduction of the North China Block and crustal eclogitization after high pressure/ultrahigh pressure collision. Thus, the observed regional extensional deformation and voluminous magmatic activity in the Western Dabie Orogen can be self-consistently explained by interactions between the two sutures and crustal eclogitization. [ABSTRACT FROM AUTHOR]

The study present the use of Geographic Information System (GIS) to assess the geotectonic regimen of the Sabinas Basin. Initially, the GIS database was designed using geological and geophysical information (total magnetic field reduced to the pole). Subsequently, 2D models of the basin were obtained along 4 profiles running on a north-south direction. The implementation of GIS enables a geological-geophysical interpretation generating various thematic maps that overlap the magnetic map during interpretation. The analysis of overlapping maps enables the identification of areas with different geotectonic regimes in the Sabinas Basin, as well as the relationship between these environments and mineralization. The qualitative and quantitative interpretation of the aeromagnetic data obtained for the total magnetic field reduced to the pole delineate uplifted basement areas as well as shallower blocks within them. This paper presents the location of both the basin's deepest zones and its probable faults, which can be linked to the block boundaries. The faults zones and block boundaries correspond to the main mineral deposits found in the basin. Finally, the geotectonic regime of some sectors of the basin is detailed in order to reaffirm the results obtained by the interpretation of aeromagnetic data. [ABSTRACT FROM AUTHOR]

Buried tunnel valleys, developed by glacial meltwater below former continental ice-sheets, are often hardly recognisable during deep land seismic surveys and may act as obstructions in the investigation of deeper geological strata both onshore and offshore. Unique, detailed high-resolution onshore seismic investigations in western Lithuania revealed strong or marked anomalies of seismic velocities within the infilling of a tunnel valley. Such an anomaly produces a pull-up effect of seismic reflections from deeper geological interfaces, which in turn may produce inaccuracies in seismic data interpretation giving false pull-up structures, false faults and even false oil traps. In this paper, a method for improving depth mapping of horizons subject to high-velocity pull-ups in time-domain images is discussed. Using seismic and well-log data, improved geological sections were obtained by properly accounting for seismic velocities of valley-infill (lenses) obtained via well-logs. [ABSTRACT FROM AUTHOR]

We coupled analysis of regional reflection seismic data with core data from International Ocean Discovery Program (IODP) Expedition 349 and found differences in both depositional features and calculated subsidence between the East and Southwest Subbasins. We calculated the original (decompacted) thicknesses of sediment for different time slices. The depositional features of the basin show that the sedimentation is controlled by both climate and tectonics. Decoupling of sedimentation rates and fluxes is often observed between the continental margin and deep basin. An abrupt increase in sedimentation rates since the Pliocene suggests that glacial–interglacial climate variability impacted erosion rates. The sedimentation rate peaked during the Pliocene in the Southwest Subbasin, but peaked during the Quaternary in the East Subbasin, showing strong influence of surrounding tectonic events, such as the buildup of Taiwan Orogen, on erosion rates. We examine thermal subsidence of the two subbasins by fitting the isostatically balanced basement depths from the seismic profiles with the half space cooling model. The estimated thermal diffusivity of the lithosphere in the Southwest Subbasin is much higher than in the East Subbasin. These contrasting observations suggest that lithospheric rock compositions may contribute to different tectonic subsidence curves between the East and the Southwest Subbasins. [ABSTRACT FROM AUTHOR]

The South China Sea is the largest marginal basin in the world, and is located in the confluence of three major tectonic plates (Pacific-Philippine Sea, Indo-Australia, Eurasia). Its tectonic history and evolution throughout the Cenozoic has been the subject of much discussion with regards to its mechanism, timing, and relationship to neighboring geological features. We conducted the first Re-Os isotope study of the South China Sea cores recovered from ocean drilling (ODP-Ocean Drilling Program and IODP-International Ocean Discovery Program) and from Philippine oil exploration wells in order to investigate whether or not the basin's tectonic evolution will be reflected in the seawater Os isotope record. These cores represent the northern and southern conjugate margins of the South China Sea, and should have complementary records of the tectonic events in the basin. We found three important negative anomalies in the South China Sea's seawater Os isotope record at 35–33 Ma, 26–23 Ma, and ~ 13–6 Ma, which are temporally related to tectono-magmatic events. At the northern margin, the record starts with the lowest ( 187 Os/ 188 Os) i values of 0.37 and 0.32 for the oldest samples, which then progresses to more radiogenic values for younger sediments. The trend is consistent with the start of seafloor spreading at ~ 33 Ma that saw the peak in the flux of mantle-derived material, which later slowed down until the second peak between 26 and 23 Ma. However, these unradiogenic values also mark the Eocene-Oligocene Transition and more likely implies South China Sea connectivity to global ocean circulation since pre-Oligocene. In both margins, slight to marked decrease in ( 187 Os/ 188 Os) i values deviate from the global trend and coincides with the ridge jump at ~ 23 Ma. In the southern conjugate margin, ( 187 Os/ 188 Os) i show a general decreasing tendency opposite that of the northern margin and the global trend starting from Mid- to Late Miocene (~ 13–6 Ma). Mass balance modeling suggests that the two younger negative excursions may be accounted for by mantle and hydrothermal Os inputs of ~ 372 mol/my at ~ 23 Ma and post ~ 13 Ma. We suggest that the post ~ 13 Ma protracted decrease in ( 187 Os/ 188 Os) i values for the southern margin reflects localized input of mantle-derived lithogenic Os from the Luzon Arc combined with post-spreading magmatic intrusions, and possibly gradual changes in paleoceanographic condition at the southern East Sub-basin. [ABSTRACT FROM AUTHOR]

The East Beni Sueif Basin is the only tested hydrocarbon-bearing basin on the eastern side of the Nile in Egypt. The basin is located around 150 km to the south of Cairo. This work introduces the first attempt of seismic interpretation and structural patterns of this basin, for which subsurface published works are lacking. Structural imaging of the area is achieved through interpretation of pre-stack time migration (PSTM) seismic cube and data sets of seven wells. The penetrated sedimentary section is represented by Albian-Middle Eocene sediments. The East Beni Sueif Basin is a type of the whole graben-system and is bounded by two NW-SE bounding faults. These faults had continued activity in an extensional regime associated with fault-propagating folds. The basin is traversed by a N75°E-trending fault system at basement level. This fault system separates the basin into two structural provinces. The Northwestern Province is deeper and shows more subsidence with a predominance of NW-trending longitudinal faults and N60·W oblique faults to the basin trend. The Southeastern Province is shallow and crossed by N14·W-trending faults which are slightly oblique to the basin axis. Albian time had witnessed the main extensional tectonic phase and resulted in major subsidence along basin-bounding faults associated with growth thickening of basal deposits. During Senonian time, the basin experienced a mild phase of transtensional tectonics, which formed negative-flower structures entrapping different folds along the N75°E and N60·W faults. The timing and style of these structures are similar to the Syrian-Arc structures in several Western Desert oil fields. The basin emerged during the Paleocene with scoured and eroded top Cretaceous sediments. Subsidence was resumed during the Early Eocene and resulted in 1500 m-thick carbonate sediments. Lastly, a mild extensional activity possibly occurred during the Oligocene-Miocene time. Despite the possible restricted potentiality of the source rock, the main hydrocarbon accumulation risk is attributed to retention in traps of long-span tectonic history. Reaching of main faults to surface through brittle carbonate cap rocks and limited thickness of the shale in the reservoir section risk hydrocarbon sealing. Buried structures of passive setting during the Tertiary show a minor trapping risk. [ABSTRACT FROM AUTHOR]

The Santa María-Hualfín Basin was proposed as a regional synchronous lithostratigraphic depocenter in the geological province of Northwestern Pampean Ranges, Northwestern Argentina. However, new 40 Ar– 39 Ar dating indicates that deposits toward the east, in Santa María Valley (Santa María Department), are younger than the western depocenter in San Fernando (Belén Department). Therefore, it would be more appropriate to study these valleys as separate basins, each one with its own tecto-sedimentary features. The east basin, named in this paper Villavil-Quillay, constitutes an elongated independent basin that developed along the front of the eastern Puna bordering with Papachacra and Durazno Ranges. This basin is composed of more than 3000 m of mudstone, sandstone, conglomerates, volcaniclastic and pyroclastic deposits. Villavil-Quillay basin develops onto a peneplain of Precambrian and lower Cambrian rocks, most of which are metamorphic and granites rocks. The sedimentary fill consists of Cretaceous? and Cenozoic continental deposits. The Cenozoic record is composed of a) the Santa María Group (Miocene-Pliocene), formed by Las Arcas, Chiquimil, Andalhuala and Corral Quemado Formations, and b) the Punaschotter unit (Puna's Gravels in German, Pleistocene). This study involves the Andalhuala, Corral Quemado and Punaschotter deposits cropping out in San Fernando area. The set of identified facies assemblage corresponding to the Andalhuala Formation shows a vertical variation of fluvial sub-environments, varying from permanent sandy braided rivers to gravel rivers and aeolian dunes culminating in an alluvial dry cycle. While facies assemblages of the Corral Quemado Formation allow inferring the development of ephemeral water bodies from secondary channels on the floodplain, the Punaschotter conglomerates indicate the development of gravel channels and bars. Three samples of tuffs interbedded in the sedimentary levels of Andalhuala Formation were dated indicating that the Miocene-Pliocene boundary is represented in this area. The lower tuff beds, outcropping at the southwest of San Fernando Sur, provided an age of 5.59 ± 0.04 Ma (late Miocene, Messinian). The others tuffs beds, both outcropping at the west-northwest of San Fernando Norte and overlaying the first one, gave an age of 4.79 ± 0.15 Ma and 4.72 ± 0.08 Ma (early Pliocene, Zanclean), respectively. These absolutes ages, together with the results of a sedimentological analysis, indicate that westward from San Fernando River, much of the areas mapped as Corral Quemado Formation correspond to the Andalhuala Formation; while part of the area considered as Punaschotter unit must be assigned to Corral Quemado Formation. Also, a thick tuff bed, recognized at the contact of Corral Quemado and Punaschotter , was considered as the previous one dated in 3.66 Ma, in Puerta de Corral Quemado locality. [ABSTRACT FROM AUTHOR]

At the northwestern portion of the Tandilia System, a detailed structural analysis on the Precambrian sedimentary units exposed in the quarries of the Olavarría-Sierras Bayas area was carried out. These units exhibit deformational structures of several scales, from centimeters to hundreds of meters. The hundreds of meters scale involves E-W- and NW-SE-trending normal faults and NW-SE- and NE-SW-trending contractional folds. The centimeters to meters scale involves veins, joints, normal faults, shear fractures and stylolites, with a prevailing ∼ E-W to NW-SE trend. All these structures were formed by two major tectonic events. The first was the folding event at ∼580 Ma, with NNE-SSW to NE-SW and NW-SE direction of contraction. The second was the extensional faulting event, given by the widespread NNE-SSW-directed extension event during the Atlantic Ocean opening (Jurassic-Cretaceous). Both major events would have been controlled by the reactivation of basement anisotropies. These major tectonic events controlled the deformation of the Precambrian sedimentary cover of the Tandilia system, leading to an economically important aspect in the mining development of the Olavarría-Sierras Bayas area. [ABSTRACT FROM AUTHOR]