In Alabama, the Paleozoic Appalachian thrust belt plunges southwest beneath the Mesozoic-Cenozoic Gulf Coastal Plain. In Arkansas, the Paleozoic Ouachita thrust belt plunges southeast beneath the Coastal Plain. The strikes of the exposed thrust belts suggest an intersection beneath the Coastal Plain. Well data and seismic reflection profiles confirm the strike and intersection of the thrust belts, and provide information to determine the structure and general stratigraphy of each thrust belt. In east-central Mississippi, the Appalachian thrust belt curves from the regional northeast trace to westward at the intersection with the southeastern terminus of the Ouachita thrust belt, to northwest where Ouachita thrust sheets are in the Appalachian footwall, and farther west, to a west-southwest orientation. At the intersection, the frontal Appalachian fault truncates the Appalachian thrust sheets. The Appalachian thrust sheets are detached in Lower Cambrian strata and contain a distinctive Cambrian-Ordovician passive-margin carbonate succession. The Ouachita thrust sheets are detached above the carbonate succession and contain a thick Carboniferous clastic succession. The Appalachian thrust sheets east of the intersection rest on an autochthonous footwall with a thin Lower Cambrian sedimentary cover above Precambrian crystalline basement. To the west, the Appalachian thrust sheets rest on an allochthonous footwall of thick Ouachita thrust sheets. The top of Precambrian crystalline basement rocks dips southwestward beneath the Ouachita thrust belt; large-magnitude down-to-southwest basement faults enhance the deepening. Appalachian thrust sheets on the northeast are detached above relatively shallow basement, but to the west, are detached above thick Ouachita thrust sheets, which overlie deeper basement. The structure of the basement reflects the Iapetan rifted margin, where the northwest-striking Alabama-Oklahoma transform bounds the southwest side of the Alabama promontory. The trends of basement structures and subsidence toward the Ouachita thrust belt parallel the Alabama-Oklahoma transform. Shallower basement and synrift basement grabens underlie the northeast-striking Appalachian thrust belt. The curves in strike and along-strike change in footwall structure of the Appalachian thrust belt reflect controls by basement structure and by the structure of the Ouachita thrust belt.

No description available.

No description available.

La chaîne actuelle du Tian Shan (Asie centrale) est considérée comme une conséquence directe de la réactivation d'une ceinture orogénique du Paléozoïque due à la collision Inde-Asie, au Cénozoïque. Un travail détaillé a été réalisé le long du piémont nord de la chaîne en intégrant les observations géologiques de terrain, analyses structurales, profils sismiques, nouvelles mesures des anomalies gravimétriques et des données de forages. Tout d'abord cette étude apporte de nouvelles preuves directes, à différentes échelles, sur l'existence d'un paléo-relief majeur le long du front nord du Tian Shan au cours du Mésozoïque, et plus particulièrement pendant le Jurassique. Deuxièmement, la quantité de raccourcissement calculée à travers cette ceinture de plis et chevauchements nord du Tian Shan est relativement faible et les structures reconnues le long du front de la chaîne présentent une hétérogénéité latérale forte. Ainsi, alors qu’un chevauchement du socle paléozoïque sur les séries sédimentaires mésozoïques et cénozoïques du bassin est remarquablement exposé le long de certaines vallées, d'autres sections montrent que les séries sédimentaires du Trias au Jurassique peuvent être suivies de manière continue, depuis le bassin jusque sur le toit du socle Paléozoïque où ils reposent en discordance relativement haut dans la chaîne. Quatre coupes géologiques ont été construites par l'intégration des données pluridisciplinaires acquises. La restauration de ces coupes montre que les taux de raccourcissement sont inférieurs à 20% et peuvent descendre à un minimum de 6%. Ces observations suggèrent que le piémont nord du Tian Shan est plutôt «jeune» et que la chaîne d’avant pays est encore à un stade primaire de son évolution tectonique. En d'autres termes, le piémont nord du Tian Shan peut être considéré comme un exemple type de front de chaîne immature. / The modern Tian Shan (Central Asia) is considered as a direct consequence of the reactivation of a Paleozoic orogenic belt due to the India – Asia collision, during Cenozoic times. A detailed work has been investigated along the northern piedmont of Tian Shan, integrating the field work, structural analysis, seismic profile data, gravity anomaly measurements and drilled wells. Firstly, this study brings new and direct evidences, at different scales, for the existence of a major paleo-relief along the northern Tian Shan range during Mesozoic, and particularly during Jurassic times. Secondly, the calculated shortening amount in the northern piedmont of Tian Shan is rather small and the structural pattern of its front is heterogeneous along-strike. While, thrusting of the Paleozoic basement on the Mesozoic or Cenozoic sedimentary series of the basin is remarkably exposed along several river valleys, other sections display continuous Triassic to Jurassic sedimentary series from the basin to the range where they unconformably overlie on the Carboniferous basement. Four cross-sections are made by integrating multi-method data, showing that shortening amounts are less than 20% and could be even until to 6%. This suggests that the Tian Shan intracontinental range is rather “young” and still at a primary stage of its tectonic evolution. In other words, its front may be considered as a typical example of an immature range front.

The thin-skinned structures of the late Paleozoic Ouachita thrust belt intersect the basement structures of the Southern Oklahoma aulacogen beneath the Mesozoic strata of the Gulf Coastal Plain in southeastern Oklahoma. The Ouachita thrust belt forms a large northwest-directed salient which extends primarily in the subsurface from central Mississippi northwestward to Arkansas and eastern Oklahoma, and from there, southwestward toward central Texas. Kinematics are complicated in the center of the Ouachita salient, where the average southwesterly strike of thrust faults is nearly perpendicular to average trend of compressional basement structures in the Southern Oklahoma aulacogen (Arbuckle uplift) and Muenster arch. Furthermore, the frontal fault of the Ouachita thrust belt curves sharply eastward around the southeastern end of the Arbuckle uplift, and bends sharply to the west between the Arbuckle uplift and the Muenster arch farther south in Texas. Nine new interpreted structural cross sections show the structural complexity of the area where the Ouachita thrust belt intersects the Arbuckle uplift and Muenster arch. Detailed study of the structural geology of the Ouachita Mountains and Arkoma basin indicates that along-strike changes in structural style evidently are related to along-strike changes in mechanical stratigraphy (relative thicknesses of weak units, in contrast to stiff units). The middle part of the Stanley Group (Formation) evidently serves as a wavelength transition and/or volume compensation zone. Along-strike change in stratigraphic level of detachments and abrupt eastward thickening of the Atoka Formation along the Ouachita thrust front strongly affected the structural style of the Ouachita thrust belt. Regional stratigraphy, palinspastic restorations of the footwall cutoff of the Ti Valley fault, and an abrupt change in character of seismic reflectors indicate an abrupt facies transition in the Middle Ordovician-Mississippian succession along the southeastern flank of the Arbuckle uplift and southwestward toward the deep southeastern part of the Ardmore basin. Out-of-syncline structures in the Bryan smallscale salient, distinct sub-thrust angular unconformities imaged on seismic profiles, and sediment dispersal patterns in the early Atokan-Desmoinesian strata of the northern Fort Worth basin (south of the Muenster arch) all indicate that the Tishomingo-Belton and Muenster structures were pre-thrust structural highs.

The American Cordillera, a major mountain belt spanning>15000 km along the western margins of North and South America, formed as a result of crustal shortening and magmatism during ocean-continent convergence. These mountains were the loci of addition and redistribution of continental crust. The contributions presented here address the style, timing, and kinematics of underthrusting of continental crust in the retroarc of the central Andes as well as the rapid burial and metamorphism of forearc rocks that contributed to magmatism in the Canadian Cordillera. This work involved geological mapping and structural analysis coupled with geo- and thermochronological analysis. In the central Andes, results confirm a southward transition in structural style and magnitude of Cenozoic shortening that coincides with the disappearance of a thick Paleozoic basin that accommodated major Cenozoic shortening. U-Pb and (U-Th)/He results also demonstrate that thrust belt kinematics in northwestern Argentina were greatly influenced by pre-orogenic heterogeneities in Cretaceous rift architecture. Results from western Canada reveal that rapid underthrusting of forearc rocks occurred during Late Cretaceous time, likely associated with an episode of shallow subduction. This event did not result in basement-involved foreland uplifts thought to be a signature of shallow subduction in the western United States and central Argentina. Taken together, this work has the major implication that variations in the pre-orogenic upper crustal architecture strongly influence the behavior of the continental lithosphere during orogenesis, a result that challenges geodynamic models that largely neglect upper plate heterogeneities.

This investigation focuses on the Jurassic-Eocene sedimentary record of northwestern Montana and the geometry and kinematics of the thrust belt, in order to develop a unifying geodynamic-stratigraphic model to explain the evolution of the Cordilleran retroarc of this region. Provenance and subsidence analyses suggest the onset of a foreland basin system by Middle Jurassic time. U-Pb ages of detrital zircons and detrital modes of sandstones indicate provenance from accreted terranes and deformed miogeoclinal rocks. Subsidence commenced at ∼170 Ma and followed a sigmoidal pattern characteristic of foreland basin systems. Jurassic deposits of the Ellis Group and Morrison Formation accumulated in a back-bulge depozone. A regional unconformity/paleosol zone separates the Morrison from Cretaceous deposits. This unconformity was possible result of forebulge migration, decreased dynamic subsidence, and eustatic sea level fall. The late Barremian(?)-early Albian Kootenai Formation is the first unit in the foreland that consistently thickens westward. The subsidence curve at this time begins to show a convex-upward pattern characteristic of foredeeps. The location of thrust belt structures during the Late Jurassic and Early Cretaceous is uncertain, but provenance information indicates exhumation of the Intermontane and Omineca belts, and deformation of miogeocline strata, possibly on the western part of the Purcell anticlinorium. By Albian time, the thrust belt had propagated to the east and incorporated Proterozoic rocks of the Belt Supergroup as indicated by provenance data in the Blackleaf Formation, and by cross-cutting relationships in thrust sheets involving Belt rocks. From Late Cretaceous to early Eocene time the retroarc developed a series of thrust systems including the Moyie, Snowshoe, Libby, Pinkham, Lewis-Eldorado-Steinbach-Hoadley, the Sawtooth Range and the foothills structures. The final stage in the evolution of the compressive retroarc system is recorded by the Paleocene-early Eocene Fort Union and Wasatch Formations, which are preserved in the distal foreland. A new ∼145 Km balanced cross-section indicates ∼130 km of shortening. Cross-cutting relationships, thermochronology and geochronology suggest that most shortening along the frontal part of the thrust belt occurred between the mid-Campanian to Ypresian (∼75-52 Ma), indicating a shortening rate of ∼5.6 mm/y. Extensional orogenic collapse began during the middle Eocene.

Se estudia una porción de la Faja Plegada y Corrida de Malargüe en el sur de los Andes Centrales (Cordillera Principal), Mendoza, Argentina, entre los 34 40 - 35 de latitud sur y 69 - 70 de longitud Oeste. Este área se encuentra regionalmente vinculada en su génesis y evolución al margen continental activo de América del Sur. Se caracteriza por un basamento volcaniclástico-plutónico de edad Permotriásica al que sobreyace una secuencia sedimentaria Triásica a Terciaria diferenciada en los Grupos Cuyo, Lotena, Mendoza, Rayoso, Neuquén, Malargüe y unidades cenozoicas que en conjunto suman un espesor mayor a los 6200 metros. La construcción de este sector del orógeno, asociada a la tectónica andina, involucra al basamento definiéndose a la faja plegada y corrida de Malargüe como epidérmica gruesa. La deformación del basamento y su vinculación con la cubierta sedimentaria permite explicar algunos rasgos notables para las estructuras ándicas de este sector de la Cordillera Principal, como la variación en el rumbo, cambios en la longitud de onda de los pliegues, presencia de múltiples despegues dentro de la cubierta sedimentaria o grandes variaciones de acortamiento entre regiones próximas. El objetivo de esta tesis es desarrollar un modelo cinemático para este sector de la Cordillera Principal argentina, sustentado en un detallado trabajo de superficie y apoyado por los datos disponibles de perforaciones y sísmica. Se interpretan y reconstruyen tres secciones estructurales de 60 km de longitud orientadas en dirección Oeste-Este, subperpendiculares a la dirección relevada para las estructuras tectónicas asociadas a la orogenia andina. Los afloramientos del Grupo Cuyo ocupan la porción occidental de estas secciones, mientras que el Mesozoico medio y alto queda restringido al centro localizándose las unidades terciarias en el borde oriental. Se interpretan dos altos de basamento cuyo rasgo superficial corresponde a importantes sinclinorios, denominados alto del arroyo El Freno y alto del arroyo Blanco, siendo el corrimiento asociado a este último el responsable de la exhumación del Grupo Cuyo desplazándose como falla fuera de secuencia en el último estadio de la evolución del área. La deformación del basamento por fallamiento retrovergente asociado a corrimientos regionales provergentes se revela como una posibilidad altamente confiable para la resolución de problemas tectónicos tanto en este como en otros sectores de la Cordillera Principal. Existe un notable desarrollo espacial de zonaciones estructurales asociadas a la geometría que presenta el basamento para esta porción de la Faja Plegada y Corrida de Malargüe en respuesta al crecimiento y avance del zócalo deformado como resultado de la compresión andina. Se observa una secuencialidad de eventos que permite definir un modelo progresivo en el tiempo, en donde la zonación estructural producida en respuesta a la deformación del zócalo es posteriormente afectada por el desarrollo de una nueva estructura de basamento. Los acortamientos medidos sustentan la imposibilidad de la inversión tectónica como mecanismo de construcción y avance del frente montañoso para esta porción de la Faja Plegada y Corrida de Malargüe, debiendo considerarse aplicar esta posibilidad con mucha cautela en otros sectores de la Cordillera Principal. / This thesis involves the study of the Malargüe Fold and Thrust belt, part of the Central Andes at the southern Cordillera Principal, Mendoza province, Argentina (34 40 35 S and 69 - 70W). The tectonic setting and evolution of the area is controlled by the continental active margin of the South America plate. The Malargüe Fold and Thrust belt is characterized by a volcaniclastic-plutonic Permian-Triassic basement which overlies a sedimentary sequence represented by Cuyo, Lotena, Mendoza, Rayoso, Neuquén and Malargüe Groups and cenozoic units, with more than 6200 meters of thickness. Construction of the mountain front is related to Andean tectonics and involves basement thrust sheets, defining a thick-skinned fold and thrust belt in this particular site of the Central Andes. Relationship between basement and fault and fold sedimentary cover allow us to explain some particular features for Andean structures at the Atuel river valley, such as strike variations, fold wave-length changes, multiple detachments horizons located into the sedimentary cover or different shortening between near localities. The aim of this thesis is to develop a kinematic model for this zone of Cordillera Principal province, supported in a detail field work and well and seismic available data. Three West-East structural sections with 60 km of length are interpreted and reconstructed, subperpendicular to tectonic orientation mapped for Andean structures. Cuyo Group outcrops are located at the western side of the sections, while middle and upper Mesozoic remains restricted to the centre and tertiary deposits are located at the eastern side. According to this, two structural basement highs where interpreted named as arroyo El Freno high and arroyo Blanco high. Regional major thrust involved to the elevation of the arroyo Blanco high is interpreted as responsible of Cuyo Group exhumation, related to an out-of sequence displacement that affects folded Mesozoic sequence in the latest stadium of tectonic evolution of the area. Basement deformation associated to regional master foreland thrusts and the developed of backthrusting appears to be a high confident possibility of resolution of tectonics problems in this area as well in another places of Cordillera Principal Province. There is notable structural zonation related to the basement geometry at this site of Malargüe Fold and Thrust belt in response to the growing and forward movement of deformed crystalline basement as a result of Andean compression. A temporal sequence of events can be observed allowing us to define a progressive model, where the previous structural zonation is affected for a new local basement structure. Shortening measures support impossibility of tectonic inversion of rifting Triassic normal fault system as a viable mechanism of construction y evolvement of mountain front for this part of Malargüe Fold and Thrust belt; a carefully consideration to this option in the study of others sides of Cordillera Principal is suggested.

Transverse zones are important syn-kinematic components of thrust belt development. Various scales of data were utilized to develop three-dimensional geometric and kinematic models for the Bessemer transverse zone (BTZ) of the Alabama Alleghanian thrust belt. Regional analysis of the BTZ began with the examination of geologic maps (1:250,000, 1:48,000, and 1:24,000 scales), seismic reflection profiles, well data, and previous stratigraphic research. All Paleozoic-age stratigraphic contacts, major thrust faults and associated folds, and various unnamed minor structures were compiled to create two strike-perpendicular, and five-strike parallel, cross sections transecting the extent of the BTZ at a scale of 1:100,000. The balanced and viable cross sections were used to create palinspastic maps of the BTZ. The deformed cross sections and geologic maps, and the restored cross sections and palinspastic maps, model the post- and prekinematic geometry of the transverse zone, respectively. Additional geological fieldwork in the northwestern part of the BTZ permitted the construction of geologic maps (1:24,000 scale) documenting cross-strike links (the fundamental unit of transverse zones) exposed at the present erosional surface (Concord and McCalla 7.5 quadrangles). Balanced and viable geologic cross sections (1:24,000 scale) were constructed from these data and placed parallel and perpendicular to strike of cross-strike links. The cross sections were restored and used to create 1:24,000-scale palinspastic maps of the cross-strike links in this part of the BTZ. The cross sections and maps model the three-dimensional geometry of the cross-strike links comprising the BTZ. Sub-allochthon basement structures are present beneath the thrust transport vectors of cross-strike links in the BTZ, indicating genetic relationships between transverse zone structures and underlying basment structures. Basement-graben related changes in the stratigraphic thickness of the decollement-host horizon are interpreted as having localized and facilitated growth of the Bessemer mushwad, a ductile duplex in the allochthon. The muswad localized the structural position of two thrust sheets and several cross-strike links in the BTZ. Geologic map patterns of the transverse zone indicate a break-back deformation sequence for the BTZ, interpreted as a response to decollement propagation through an allochthon-spanning weak decollement-host horizon, which had large stratigraphic thickness variations in basement grabens.

Cette thèse présente les résultats et conclusions issues d’une série de modèles analogiques de systèmes de compressif à différentes échelles : Les expériences réalisées à l’échelle crustale montrent que la symétrie de structures compressives, de type plis et chevauchements avec 3 niveaux de décollement, est fortement dépendante de la vitesse de sédimentation. Les résultats ont été appliqués au Subandin Bolivien. Les expériences réalisées à l’échelle lithosphérique simulent la subduction et l’extension arrière-arc dans un système subissant une compression parallèle à la marge continent-océan (COB). Ces modèles démontrent que la différence de densité entre les plaques continentales et océaniques est le paramètre clé pour expliquer l'extension arrière-arc: plus petite est la différence de densité, plus faible est l'extension produite. Les résultats ont été appliqués al ‘Anatolie. Enfin, ces modèles ont été utilisés pour tester la reproductibilité et les limites de la modélisation analogique. / This thesis presents the results and conclusions from a series of analogue modelling of deformation in compressive and subduction zones (crustal scale and lithospheric scale) : The experiments carried out at the crustal scale show that the symmetry of compressive structures, folds and trust belts with 3 levels of décollement is strongly dependent on the rate of sedimentation. The results were applied to the Subandin Bolivian. The experiments carried out at the lithospheric scale simulate subduction and back-arc extension in a system under compression parallel to the continent - ocean margin (COB). These models show that the density ratio between the continental and oceanic plates is the key factor to explain the back-arc extension: as smaller the difference in density is, less extension occurred. The results were applied to Anatolia. Finally, these models were used to test the reproducibility and limits for analog modeling.