A Large-scale Tertiary Salt Nappe Complex in the Leading Edge of the Kuqa Foreland Fold-Thrust Belt, the Tarim Basin, Northwest China

The tectono-stratigraphic sequences of the Kuqa foreland fold-thrust belt in the northern Tarim basin, northwest China, can be divided into the Mesozoic sub-salt sequence, the Paleocene-Eocene salt sequence and the Oligocene-Quaternary supra-salt sequence. The salt sequence is composed mainly of light grey halite, gypsum, marl and brown elastics. A variety of salt-related structures have developed in the Kuqa foreland fold belt, in which the most fascinating structures are salt nappe complex. Based on field observation, seismic interpretation and drilling data, a large-scale salt nappe complex has been identified. It trends approximately east-west for over 200 km and occurs along the west Qiulitag Mountains. Its thrusting displacement is over 30 km. The salt nappe complex appears as an arcuate zone projecting southwestwards along the leading edge of the Kuqa foreland fold belt. The major thrust fault is developed along the Paleocene-Eocene salt beds. The allochthonous nappes comprise large north-dipping faulting monoclines which are made up of Paleocene-Pliocene sediments. Geological analysis and cross-section restoration revealed that the salt nappes were mainly formed at the late Himalayan stage (c.a. 1.64 Ma BP) and have been active until the present day. Because of inhomogeneous thrusting, a great difference may exist in thrust displacement, thrust occurrence, superimposition of allochthonous and autochthonous sequences and the development of the salt-related structures, which indicates the segmentation along the salt nappes. Regional compression, gravitational gliding and spreading controlled the formation and evolution of the salt nappe complex in the Kuqa foreland fold belt.

An alternative interpretation for the map expression of "abrupt" changes in lateral stratigraphic level near transverse zones in fold-thrust belts

The map expression of ＂abrupt＂ changes in lateral stratigraphic level of a thrust fault has been traditionally interpreted to be a result of the presence of （1） a lateral （or oblique） thrust-ramp, or （2） a frontal ramp with displacement gradient, and/or （3） a combination of these geometries. These geometries have been used to interpret the structures near transverse zones in fold-thrust belts （FTB）. This contribution outlines an alternative explanation that can result in the same map pattern by lateral variations in stratigraphy along the strike of a low angle thrust fault. We describe the natural example of the Leamington transverse zone, which marks the southern margin of the Pennsylvanian-Permian Oquirrh basin with genetically related lateral stratigraphic variations in the North American Sevier FTB. Thus, the observed map pattern at this zone is closely related to lateral stratigraphic variations along the strike of a horizontal fault. Even though the present-day erosional level shows the map pattern that could be interpreted as a lateral ramp, the observed structures along the Leamington zone most likely share the effects of the presence of a lateral （or oblique） ramp, lateral stratigraphic variations along the fault trace, and the displacement gradient.

Numerical simulation of temporal and spatial evolution of fold-thrust belts in the northern and northeastern margins of the Qinghai-Tibetan Plateau

Fold-thrust belts are common structural styles under the background of long-term regional tectonic shortening.The northern and northeastern margins of the Qinghai-Tibetan Plateau are located on the edge of the growth and expansion of the Qinghai-Tibetan Plateau.Since nearly 10 Ma,some significant and typical fold thrust belt have been formed.The spatial-temporal evolution of these fold-thrust belts and the characteristics of surface deformations are significant issues in geodynamics.In this paper,we use the elastoplastic finite element model with considering the contact nonlinearity to study the spatialtemporal evolution of the fold-thrust belts in the northern and northeastern margins of the Qinghai-Tibetan Plateau,with particular attention to the details of the relationship between the depth and the shallow,the spatialtemporal order,and the characteristics of the surface deformation,etc.,in order to make a relatively complete mechanical interpretation of the spatial-temporal evolution of the foldthrust belts in the northern and northeastern margins of the Qinghai-Tibetan Plateau from the perspective of geodynamics.

Geological structures and potential petroleum exploration areas in the southwestern Sichuan fold-thrust belt, SW China

Based on the latest geological,seismic,drilling and outcrop data,we studied the geological structure,tectonic evolution history and deformation process of the southwestern Sichuan fold-thrust belt to find out the potential hydrocarbon exploration areas in deep layers.During key tectonic periods,the southwestern Sichuan fold-thrust belt developed some characteristic strata and structural deformation features,including the Pre-Sinian multi-row N-S strike rifts,step-shaped platform-margin structures of Sinian Dengying Formation,the western paleo-uplift in the early stage of Late Paleozoic,the Late Paleozoic–Middle Triassic carbonate platform,foreland slope and forebulge during Late Triassic to Cretaceous,and Cenozoic multi-strike rejuvenated fold-thrusting structures.The fold-thrust belt vertically shows a double-layer structural deformation controlled by the salt layer in the Middle Triassic Leikoupo Formation and the base detachment layer at present.The upper deformation layer develops the NE-SW strike thrusts propagating toward basin in long distance,while the deeper deformation layer had near north-south strike basement-involved folds,which deformed the detachment and thrusting structures formed earlier in the upper layer,with the deformation strength high in south part and weak in north part.The southern part of the fold-thrust belt is characterized by basement-involved fold-thrusts formed late,while the central-northern part is dominated by thin-skin thrusts in the shallow layer.The Wuzhongshan anticlinal belt near piedmont is characterized by over-thrust structure above the salt detachment,where the upper over-thrusting nappe consists of a complicated fold core and front limb of a fault-bend fold,while the deep layer has stable subtle in-situ structures.Favorable exploration strata and areas have been identified both in the upper and deeper deformation layers separated by regional salt detachment,wherein multiple anticlinal structures are targets for exploration.Other potential exploration strata and areas in southwestern Sichuan fold-thrust belt include the deep Sinian and Permian in the Wuzhongshan structure,pre-Sinian rifting sequences and related structures,platform-margin belt of Sinian Dengying Formation,and Indosinian paleo-uplift in the east of the Longquanshan structure.

Structural geology and favorable exploration prospect belts in northwestern Sichuan Basin, SW China

The northwestern Sichuan region has experienced multi-stage tectonic evolution including marine cratonic basin from the Sinian to the Middle Triassic and intra-continental basin from the Late Triassic to the Cenozoic. Several regional tectonic activities caused complicated stratigraphic distribution and structural deformations in the deep-buried layers. During the key tectonic periods, some characteristic sedimentary and deformation structures were formed, including the step-shaped marginal carbonate platform of Dengying Formation, the western paleo-high at the end of Silurian, and the passive continental margin of the Late Paleozoic–Middle Triassic. The Meso-Cenozoic intra-continental compressional tectonic processes since the Late Triassic controlled the formation of complex thrusting structures surrounding and inside the northwestern basin. The northern Longmenshan fold-thrust belt has a footwall in-situ thrust structure,which is controlled by two sets of detachments in the Lower Triassic and Lower Cambrian and presents as a multi-level deformation structure with the shallow folds, the middle thin-skin thrusts and the deeper basement-involved folds. The thrust belt in front of the Micangshan Mountain shows a double-layer deformation controlled by the Lower Triassic salt detachment, which is composed by the upper monocline and deep-buried imbricate thrust structures. The interior of the basin is characterized by several rows of large-scale basement-involved folds with NEE strike direction. From the perspective of structural geology, the favorable exploration reservoirs and belts in northwestern Sichuan have obvious zoning characteristics. The favorable exploration layers of Dengying Formation of Upper Sinian are mainly distributed in the eastern and northern areas of the northwestern Sichuan Basin, in which the Jiulongshan structural belt, Zitong syncline and Yanting slope are the most favorable. The Lower Paleozoic was transformed by Caledonian paleo-uplift and late Cenozoic folding, and the midwest area such as the Zitong syncline is a potential area for hydrocarbon exploration. The favorable part of the Upper Paleozoic is mainly distributed in the northern Longmenshan belt and its frontal area, where the deep-buried thin-skin thrust structures in the footwall are the key exploration targets.

Geochemical signatures of potassium metasomatism in anthracite from the Himalayan fold‑thrust belts of Sikkim,India

The present study focuses on the inorganic geochemical features of the bituminous coal samples from the Raniganj and the Jharia Basins,as well as the anthracite samples from the Himalayan fold-thrust belts of Sikkim,India.The SiO_(2)content(48.05 wt%to 65.09 wt%and 35.92 wt%to 50.11 wt%in the bituminous and anthracite samples,respectively)and the ratio of Al_(2)O_(3)/TiO_(2)(6.97 to 17.03 in the bituminous coal samples and 10.34 to 20.07 in the anthracite samples)reveal the intermediate igneous source rock composition of the minerals.The ratio of the K_(2)O/Al_(2)O_(3)in the ash yield of the bituminous coal samples(0.03 to 0.09)may suggest the presence of kaolinite mixed with montmorillonite,while its range in the ash yield of the anthracite samples(0.16 to 0.27)may imply the presence of illite mixed with kaolinite.The chemical index of alteration values may suggest the moderate to strong chemical weathering of the source rock under sub-humid to humid climatic conditions.The plot of the bituminous coal samples in the A–CN–K diagram depicts the traditional weathering trend of parent rocks,but the anthracite samples plot near the illite feld and are a bit ofset from the weathering trend.This may imply the plausible infuences of the potassium-metasomatism at post coalifcation stages,which is further supported by high K_(2)O/Na_(2)O ratio(29.88–80.13).The Fourier transform infrared spectra further reveal the hydroxyl stretching intensity of illite in the anthracite samples substantiating the efect of the epigenetic potassium-metasomatism.The decrease in total kaolinite intensity/compound intensity of quartz and feldspar may provide additional evidence towards this epigenetic event.

Wadi Fatima Thin-Skinned Foreland FAT Belt: A Post Amalgamation Marine Basin in the Arabian Shield

Wadi Fatima fold-thrust (FAT) belt is a distinctive foreland FAT belt in the Arabian-Nubian Shield (ANS) involving unmetamorphosed to slightly metamorphosed sedimentary sequence of Fatima Group, deposited over a metamorphic/igneous basement, comprising ortho-amphibolites, orthoand para-schists (with chaotic unmappable blocks of marbles, pyroxenites and metagabbros), older granite (773 ± 16 Ma) and younger granite. The basement exhibits structural fabrics, such as attenuated tight isoclinal folds, sheared-out hinges, NE-SW penetrative foliation and subhorizontal stretched and mineral lineations, related to an oldest prominent dextral shearing phase affected the main Wadi Fatima during the Neoproterozoic. In Wadi Fatima FAT belt, the style of deformation encompasses flexural-slip folding forming mesoscopicand map-scales NE to ENE plunging overturned antiforms and synforms, and a thrust duplex system bounded by floor thrust and sole thrust (basal detachment) dipping gently towards the hinterland (SE to SSE direction) and rises stratigraphically upwards towards the foreland. Such style is affiliated to thin-skinned deformation. Several lines of evidence, such as geometry of interacting outcropand map-scale folds and thrusts, patterns of thrust displacement variations and indications for hinge migration during fold growth, strongly suggest that folding and thrusting in Wadi Fatima FAT belt are geometrically and kinematically linked and that thrusting initiated as a consequence of folding (fold-first kinematics). Thrusts frequently show flat-ramp-flat geometry, and every so often give an impression that they are formed during two main sub-stages;an older sub-stage during which bedding sub-parallel thrusts were formed, and a younger sub-stage which generated younger ramps oblique to bedding. Thrust ramps with SE to SSE dipping regularly show sequential decrease in dip or inclination (due to piggy-back imbrication) into their transport direction which is proposed to be towards NW to NNW. Evidence indicating this transport direction of Wadi Fatima FAT belt embrace NW to NNW oriented stretching lineations recorded along thrust planes, NW to NNW folding vergence, and diminishing of the intensity of deformation and thrust stacking and imbrication from SE to NW;i.e. from hinterland to foreland. The tectonic transport vector is congruent with the mean orientation of slickenline striae formed by layer-parallel slipping along folded bedding planes. The mean orientation of slickenline lineations, after their host beds were rotated to horizontal about their strikes, is found to be N25°W - S25°E. Two tectonic models are proposed to unravel the structural history of the study area and to illustrate the tectonic evolution of Wadi Fatima FAT belt which represents one of interesting foreland FAT belts recorded worldwide. In the first model, the area was evolved from dextral shearing during the early convergence and amalgamation between East and West Gondwana, to emplacement of the older granite during a period of crustal cessation and relaxation, NNW SSE extension and extrusion of dyke swarms, emplacement of younger granite, deposition of Fatima Group over an ancient peneplain, layer parallel shortening, folding and fold tightening and overturning, thrusting, NE-SW (to NNE-SSW) shortening, and eventually NE tilting accompanied with Red Sea rifting (?). The second model suggests the presence of basement ramps (pre-existing normal faults), with NW to NNW dipping, have a strong effect on overlying Fatima Group which was evolved throughout gravitational, soft-sediment slumping and deformation.

塔里木盆地南部玛东早古生代褶皱-冲断带

玛东褶皱-冲断带位于塔里木盆地南部,走向NE-SW,由NW向SE方向冲断。褶皱冲断带发育于寒武-奥陶系,以中寒武统膏-盐层为主滑脱面。中志留统及其以上地层不整合于褶皱冲断带之上。它是世界上保存最好的早古生代褶皱冲断带之一。根据卷入变形最新地层、不整合于褶皱-冲断带之上的最老地层和上奥陶统上部的生长地层,玛东褶皱-冲断带的变形时间为晚奥陶世-早志留世。玛东褶皱-冲断带与其东南侧的塘南褶皱-冲断带同为塔里木盆地南缘早古生代前陆褶皱-冲断带的组成部分,塘南褶皱-冲断带是该早古生代前陆褶皱-冲断带主体的残余,其向NW的主冲断方向代表该前陆褶皱-冲断带的主冲断方向;玛东褶皱-冲断带是该早古生代前陆褶皱-冲断带的前锋,其向SE的冲断具有反冲性质。它们是昆仑早古生代造山作用的重要记录,也是昆仑早古生代碰撞造山带的组成部分,现今保存最好的部分。

塔里木盆地塘古孜巴斯坳陷西部中加里东期断裂特征及形成机制

根据其剖面特征可将塘古孜巴斯拗陷西部弧形断裂带划分为玛东盖层滑脱冲断体系和塘南基底卷入冲断体系2种类型。玛东盖层滑脱冲断体系都在中寒武统膏盐层内发生滑脱,塘南基底卷入冲断体系平面延伸距离较小,基本上都切穿寒武系地层延伸至基底。玛东和塘南的断裂的形成,是对中加里东期塔里木板块与阿尔金地块拼接的响应。中奥陶世开始时阿尔金地块上近东西向、由南向北逆冲的阿尔金断裂强烈活动,晚奥陶世应力传递至玛4井-叶城一带时,受刚性基底阻挡,反作用力首先在软弱基底的玛东一带形成反冲断层;奥陶纪末,随着来自南部应力的增加,塘南山前逆冲断裂带形成。而玛东冲断带南部断层在印支期的活化,属于古特提斯洋向中昆仑地体俯冲的产物。与造山带之间的距离、寒武系膏岩层的厚度及基底类型的不同导致玛东与塘南发育不同类型的构造类型。

Evolution and Structural Style of Tianshan and Adjacent Basins， Northwestern China

The Tianshan orogenic belt has a W-shape, composed of the V-shape Southern Tianshan and Northern Tianshan with different orogenic models .The Southern Tianshan broke off from the Sinian, forming a passive continental margin and ocean, and closed during Silurian and Devoaian. It belongs to the Wilson cycle orogenic model. The net duration is about 400 My.The Northern Tianshan began back-arc spreading during Devonian, forming the Devonian-Carboniferous marginal sea, and dosed during Late Carboaiferous. It belongs to the non-Wilson cycle orogeulc model or back-arc orogenic model. The duration is about 100 My .Deformation of the foreland fold-thrust belt occurred in two stages: in the early stage, folds and thrusts were formed by wedge-thrusting and lateral compression, while in the later stage, folds, gravitational normal faults and reveal faults were formed by the uplift of the Tianshan range and by gravity-gliding.

Structural features and petroleum geology of the fold-thrust belt in the southern Tarim basin, China

The west Kunlun fold-thrust belt (WKFTB) and the Altun fold-thrust belt (AFTB) are respectively located in the southern margin of the Tarim basin, NW China. The analyses of typical structures and regional dynamics of the fold-thrust belts reveal their different structural and pe-troleum features and mechanisms. WKFTB differs from AFTB by abundant fault-related folds and triangles zones, and was formed by northward extrusion of the west Kunlun orogen. AFTB was affected synchronously by northward extrusion of the Altun orogen and the sinistral strike-slipping of the Altun Fault, so it is characterized by the minor scale and the monotonous structural styles. The Aqike anticline and the Aqike fault, of which the strikes are orthogonal to the strike of the fold-thrust belts, are regarded as the adjustive structures between both of the fold-thrust belts. The oil-gas pools of WKFTB develop mainly in the faulted-related anticline traps, but the oil-gas pools of AFTB develop mainly in the low fault-block and anticlines traps related with the pa-leo-uplifts. There are different exploration countermeasures for both of the fold-thrust belts.

Influence of Mechanical Stratigraphy on the Deformation Evolution of Fold-Thrust Belts: Insights from the Analogue Modeling of Eastern Sichuan-Western Hunan and Hubei, South China

The eastern Sichuan-western Hunan and Hubei belt(ESWHHB) is an important fold-thrust belt in the Middle–Upper Yangtze region of China, and it is also an important area for petroleum and gas prospect in China. The influence of mechanical stratigraphy on the deformation evolution of the ESWHHB is a hot problem that has received widespread attention. However, due to the complexity of geological conditions, this issue has not been sufficiently addressed. Previews geological exploration studies show that the deformation evolution of the belt is closely related to the mechanical stratigraphy. Physical simulation has proven to be effective for studying the deformation evolution of fold-and-thrust belt. Based on the geological conditions of the ESWHHB, six groups of physical models were designed to analyze the influences of the ductile layer and overlap configuration on the structural deformation of the ESWHHB. The results show that the mechanical stratigraphy has significant control on the deformation evolution of the fold-thrust belt. The ESWHHB evolution is related to the lower viscosity of the ductile layer and the larger thickness of the ductile layer, while only gradual propagated fold-and-thrust belt can be resulted from the higher viscosity of the ductile layer and the smaller thickness of the ductile layer. Additionally, the overlap between the stratigraphy at various structural belts leads to significant differences in their mechanical properties, and it critically influences the structural patterns of the ESWHHB.

Tectonothermal Evolution of the Eastern Tibetan Plateau Foreland: Fission-Track Thermochronology of the Southern Dabashan Fold-Thrust Belt

Apatite fission-track dating and thermal-history modeling were carried out on samples from the Dabashan （大巴山）, a fold-thrust belt, northeast of the Sichuan （四川） Basin and east of the Tibetan Plateau. A first cooling event in the Late Cretaceous is followed by a prolonged period of ther- mal stability with exhumation rates of 〈0.025 mm/a, as determined from age vs. elevation relationships. The preservation of age vs. elevations relationships and the lack of distinct age changes across tectonic structures indicate that the Dabashan fold-thrust belt formed prior to the Late Cretaceous, consistent with the current view of Triassic-Early Cretaceous shortening. Relatively short mean track lengths （-12 μm） indicate that the samples remained in the partial annealing zone for a prolonged time. The knick points in the best-fitting temperature-time models suggest that the onset of late-stage accelerated cooling commenced at 〈11 Ma. Related exhumation rates are 0.3-0.2 mm/a assuming geothermal gra- dients of 20 and 30 ℃/km. We speculate that this late-stage event results from eastward growth of the Tibetan Plateau and overstepping of the Sichuan Basin, it is likely responsible for the youthful mor- phology of the Dabashan.

Sentinel-1 In SAR observations and time-series analysis of co-and postseismic deformation mechanisms of the 2021 Mw 5.8 Bandar Ganaveh Earthquake,Southern Iran

In the past two decades,because of the significant increase in the availability of differential interferometry from synthetic aperture radar and GPS data,spaceborne geodesy has been widely employed to determine the co-seismic displacement field of earthquakes.On April 18,2021,a moderate earthquake(Mw 5.8)occurred east of Bandar Ganaveh,southern Iran,followed by intensive seismic activity and aftershocks of various magnitudes.We use two-pass D-InSAR and Small Baseline Inversion techniques via the LiCSBAS suite to study the coseismic displacement and monitor the four-month post-seismic deformation of the Bandar Ganaveh earthquake,as well as constrain the fault geometry of the co-seismic faulting mechanism during the seismic sequence.Analyses show that the co-and postseismic deformation are distributed in relatively shallow depths along with an NW-SE striking and NE dipping complex reverse/thrust fault branches of the Zagros Mountain Front Fault,complying with the main trend of the Zagros structures.The average cumulative displacements were obtained from-137.5 to+113.3 mm/yr in the SW and NE blocks of the Mountain Front Fault,respectively.The received maximum uplift amount is approximately consistent with the overall orogen-normal shortening component of the Arabian-Eurasian convergence in the Zagros region.No surface ruptures were associated with the seismic source;therefore,we propose a shallow blind thrust/reverse fault(depth~10 km)connected to the deeper basal decollement fault within a complex tectonic zone,emphasizing the thin-skinned tectonics.

Palynological constraints on the age of the Mississippi Valley-type Changdong Pb-Zn deposit,Sanjiang belt,West China

Mississippi Valley-type(MVT)Pb-Zn deposits serve as the world’s major supply of Pb-Zn resources.However,the age constraint of MVT Pb-Zn deposits has long been a big challenge,due to the lack of minerals that are unequivocally related to ore deposition and that can be used for radioisotopic dating.Here we show sporopollens can provide useful chronological information on the Changdong MVT Pb-Zn deposit in the Simao basin,Sanjiang belt,West China.The Pb-Zn ores in the Changdong deposit are hosted by internal sediments in paleo-karst caves of meteoric origin.Sphalerite and galena occur as replacements of carbonate minerals and void infillings in the internal sediments.The relations suggest that the Pb-Zn mineralization occurred after the deposition of the internal sediments.A palynological assemblage mainly composed of angiosperm pollen dominated by Castanea,Quercus,and Carya and fern spores dominated by Polypodiaceae,Pteris,and Athyriaceae was identified.These pollen and spores place the ore-hosting internal sediments and the Changdong paleo-karst at early to middle Oligocene.Consequently,the Changdong Pb-Zn deposit must have formed after the early Oligocene(~34 Ma).These age constraints,together with the geological characteristics,indicate that the Changdong Pb-Zn deposit is a paleo-karst-controlled MVT deposit related to fold-thrust systems in the Sanjiang belt.The Changdong deposit is similar to other MVT Pb-Zn deposits in the northern part of the Sanjiang belt,making it possible to extend this Pb-Zn belt 500 km further to the South.Results presented here highlights the potential of sporopollens in dating the age of MVT deposits related to paleo-karst formation in young orogenic belts.

The transition from backarc extension to Andean growth:Insights from geochronologic,sedimentologic,and structural studies of Mesozoic and Cenozoic sedimentary and volcanic rocks in south-central Chile(36°S)

Many studies propose a significant shift in the tectonic and paleogeographic evolution of the Andes in south-central Chile and Argentina during the Late Cretaceous.It has been proposed that the preceding Jurassic-Early Cretaceous extensional regime that resulted in a low-relief volcanic arc and the backarc Neuquén basin came to an end,giving way to shortening and Andean growth from the Late Cretaceous onward.Nevertheless,there are disagreements regarding the timing and nature of this transition to Andean orogenesis.To address these issues,we conducted geochronologic(U-Pb and^(40)Ar/&(39)Ar),sedimentologic,and structural studies on Mesozoic-Cenozoic sedimentary and volcanic rocks in the Río Maule area(Principal Cordillera,Chile,36°S).From our findings and prior analyses,we propose the following tectono-stratigraphic evolution of the region.(1)Marine deposition of the Tithonian-Hauterivian Baños del Flaco Formation took place in an extensional backarc basin.(2)After a~40 Myr hiatus,fluvial deposits of the Colimapu Formation and volcanic rocks of the Plan de los Yeuques Formation accumulated during the Cenomanian-Danian.Whereas the Colimapu Formation displays evidence of syndepositional shortening,the Plan de los Yeuques Formation exhibits synextensional growth strata.Contrary to other studies,our results suggest that the Chilean part of the Principal Cordillera was largely a zone of active deposition rather than an elevated fold-thrust belt during the Late Cretaceous.We propose that sedimentation occurred within a series of relatively stable intermontane subbasins generated by shortening,followed by extension.(3)After a~20 Myr hiatus,middle Eocene to early Miocene(Lutetian-Aquitanian)accumulation of a thick succession of andesitic lavas and minor clastic sediments of the Abanico Formation occurred in an intraarc extensional basin.(4)Finally,major shortening and uplift of previously deposited Mesozoic-Cenozoic rocks took place throughout the Neogene.This phase constituted the primary contractional deformation in the Andes of south-central Chile and Argentina.In terms of the transition to early Andean deformation,we propose that structural deformation did not generate a major,regional-scale fold-thrust belt during the late Albian-Santonian.Modest extension,tectonic quiescence,or low-magnitude shortening seem to have dominated during the early to middle Cenozoic.

Structural Interpretation and Restoration of Rocky Mountain Brazeau Zone

The Rocky Mountain Foothills lie along the eastern margin of the Rocky Mountain fold-thrust belt. The area has been the focus of extensive research aimed at locating oil and gas fields with the potential to be used as CO2 storage traps. In this study, we use a seismic line from the Ca- nadian Rockies to interpret the geologic structures along a cross-section parallel to the tectonic transport direction. We then compare our results with those of previous studies. The section was restored using the MOVE software （manufactured by Midland Valley Exploration Ltd.）. The pri- mary objectives of this work are： （1） to conduct a stratigraphic and structural interpretation of a 2D seismic profile; and （2） to conduct a cross-sectional restoration of the structures in order to validate the seismic interpretation in terms of CO2 storage candidates. Additional data sources include maps of the surface geology, which show that the age of horizons decrease from west to east, and strati- graphic and structural profiles derived from well logs. The results of our structural restoration indi- cate a detachment fault between the foreland and hinterland. This fault is responsible for the cutting and subsequent upwards and eastwards movement of a stratum located between the basement and the Late Devonian formation. Large thrust faults are responsible for the deformation of strata （through both folding and faulting） in the foreland basin. As a result of continuous eastward tectonic stress, the strata from Jurassic have deformed, forming a duplex system in the middle of the section and resulting in the uplift of the upper part of the section. Following surface erosion, this uplifted area became exposed during the Tertiary Period. The high shortening rate （53%） detected through structural restoration is consistent with the thin-skinned tectonic model.