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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.

The southern and central Appalachian foreland fold-thrust belt comprises a series of orogen -scale curves that extend from Alabama to New York. One of these is the Tennessee salient, a foreland-convex curve that extends from Cartersville, Georgia, to Roanoke, Virginia. Development of a kinematic model for deformation in the salient has been hindered by a paucity of penetrative deformation in this generally low temperature, low volume-loss portion of the orogen. Industry seismic reflection lines provide greater resolution of subsurface geometry of both the basement surface and the overlying fold-thrust belt, confirming some previous interpretations and changing others. A series of cross sections based on the seismic reflection data incorporates the improved understanding of basement geometry, as well as new interpretations of fold-thrust belt structures such as a sub-thrust detachment fold along the western margin of the Valley and Ridge, a smaller detachment fold along the Cumberland Escarpment, and a duplex below the Knoxville sheet in southeastern Tennessee. The cross sections, combined with recently published analyses of calcite twin strain and paleomagnetic data around the salient, provide sufficient data to develop a new palinspastic reconstruction method and to propose a kinematic model for development of the salient. The basis of the reconstruction method is, in areas where the front of the indenter is oriented oblique to transport, the maximum shortening direction and particle displacement paths are also oblique to the bulk transport direction. Cross sections, kinematic indicators, and palinspastic reconstructions suggest that the Tennessee salient is a primary arc formed by a combination of uniform displacement in a single direction and transport-parallel simple shear (plane strain), that most major faults formed initially curved in front of the irregularly shaped Blue Ridge-Inner Piedmont indenter, and that transport in the fold-thrust belt may have occurred by plan view movement on networks of minor faults, which permitted forelandward propagation of the curved faults without significant rotation. Although the technique does not provide a unique solution, the resulting palinspastic restoration is kinematically admissible and geometrically reasonable. So, it may improve palinspastic restorations of facies in basins with no vertical axis rotations and minimal penetrative strain. Attachments are in PDF format and may be opened with Adobe Reader™.

The work presented in this thesis utilizes several geological methods to investigate the origin and evolution of the supracrustal rocks in the Palaeoproterozoic Hamrånge Group (HG) in the south-central Swedish Svecofennian. The first paper is based on whole-rock geochemistry to show the plate tectonic setting of volcanic rocks within the HG. This indicates that the environment was probably an oceanic volcanic arc. Geochronology, used in paper two, shows that the volcanism was active at 1888±6 Ma and that the sediments forming the stratigraphically overlying quartzite were deposited after 1855±10 Ma, with provenance ages overlapping both the volcanic rocks and the 1.86-1.84 Ga continental margin Ljusdal granitoids. In the third paper, thermobarometry was applied to samples from the HG, the migmatitic Ockelbo sub-domain to the south, and the 1.81 Ga Hagsta Gneiss Zone (HGZ) that separate these two units. The results show distinct differences in the metamorphic conditions that have affected the HG and the Ockelbo sub-domain, supporting previous interpretations that the HGZ is an important crustal structure, possibly a terrane or domain boundary. Paper four deals with the structural geology of the Hamrånge area. The study shows that the volcanic rocks and the underlying mica schist have been subjected to three deformation episodes (D1-D3), while the uppermost quartzite was most likely only affected by D2 and D3. While structures related to D1 are rarely seen, D2 resulted in a penetrative foliation, strong lineations and NW-vergent folding and thrusting. D3 is a result of a N-S compression that formed regional E-W folds and steep, ca. NW-SE shear zones, e.g. the HGZ. The results presented in this thesis, integrated with previously published data, outline a model for the geological evolution of the Hamrånge area: At 1.89 Ga a volcanic arc formed that subsequently collided with a continental margin resulting in the first deformation episode, D1, and probably a metamorphic event. This was possibly followed by an extensional period, after 1855±10 Ma, forming a basin that accumulated sediments later to form the quartzite stratigraphically on top of the volcanic rocks. The second deformation episode, D2, formed a fold-thrust belt when the supracrustal HG was thrusted to the NW, on top of the 1.86-1-84 Ga Ljusdal Domain. Flattening and a second metamorphic period followed this thickening of the crust. The last ductile deformation, D3, caused by regional tectonic forces, resulted in F3-folds that matured into ca. 1.8 Ga large-scale, steep shear zones transecting the Fennoscandian Shield.

The Early Permian strata of the Hongliuhe Group, NW China, experienced a thin-skinned fold-and-thrust belt style of deformation that recorded the final stages of amalgamation of the Beishan orogenic collage, a part of the Central Asian Orogenic Belt. The Hongliuhe Group was syn-orogenically deposited on an undetermined foreland, with the Mazongshan arc terrane acting as the hinterland. In this study results from detailed mapping combined with a regional analysis elucidate involvement of a northward-dipping subduction system with the collision. Well-preserved fold-and-thrust belt style deformation mapped in the upper stratigraphy of the Hongliuhe Group exhibits dominantly south-southeast verging structure, including shear folding, low-angle thrust ramping, imbrication and duplexing. Restoration of a portion of a mapped outcrop-scale cross-section estimates the accommodation of a minimum of 24% shortening. Lower stratigraphy shows discrete, steeper, north-over-south dip-slip ductile shear zones that bound packages of less deformed Hongliuhe Group strata. Fault displacement is considered to have been prolonged enough to juxtapose basal formations in northerly hangingwalls against upper formations in southerly footwalls. Faulting is closely associated with the creation of large-scale brittle-ductile eye-fold structures that are postulated to be sheath folds. The most examined and mapped structure, 16km wide, is a synclinal structure with axes plunging steeply towards its center. The ellipticity of the exposed bedding traces increases towards the center of the eye-fold, implying a structural relationship with metamorphic shear zones. Except for large-scale folding, the bulk of its strata remain relatively undeformed and have preserved primary soft-sediment deformation structures indicating younging towards the center on both limbs of the synclinal structure. Stratigraphic reconstruction of the Hongliuhe Group that considers the significant faulting shows that the Group's basal conglomerates unconformably overlie a Late-Carboniferous volcanic assemblage. The clast lithotypes of the conglomeratic successions change from polymictic metamorphic rocks at the base to monomictic granitoid clasts mid-section, showing the gradual unroofing sequence of the provenance. The stratigraphic reconstruction shows a general fining upward sequence, transitioning from terrestrial to nearshore marine depositional environments that, and in conjunction with the conglomeratic successions, suggests that the tectonic setting for deposition of the Hongliuhe Group is a foreland basin. Considering the deformation styles reported in this study, the Hongliuhe Group is interpreted to be a foreland fold-and-thrust belt. Stratigraphic reconstruction of the Hongliuhe Group that considers the significant faulting shows that the Group’s basal conglomerates unconformably overlie a Late Carboniferous volcanic assemblage. The clast lithotypes of the conglomeratic successions change from polymictic metamorphic rocks at the base to monomictic granitoid mid-section, showing the gradual unroofing sequence of the provenance. The stratigraphic reconstruction shows a general fining upward sequence through nearshore depositional environments that, and in conjunction with the conglomeratic successions, give interpretation that the tectonic setting for deposition of the Hongliuhe Group is a foreland basin. Considering the deformation styles reported in this study the Hongliuhe Group is interpreted to be a foreland fold-and-thrust belt.

The Early Permian strata of the Hongliuhe Group, NW China, experienced a thin-skinned fold-and-thrust belt style of deformation that recorded the final stages of amalgamation of the Beishan orogenic collage, a part of the Central Asian Orogenic Belt. The Hongliuhe Group was syn-orogenically deposited on an undetermined foreland, with the Mazongshan arc terrane acting as the hinterland. In this study results from detailed mapping combined with a regional analysis elucidate involvement of a northward-dipping subduction system with the collision. Well-preserved fold-and-thrust belt style deformation mapped in the upper stratigraphy of the Hongliuhe Group exhibits dominantly south-southeast verging structure, including shear folding, low-angle thrust ramping, imbrication and duplexing. Restoration of a portion of a mapped outcrop-scale cross-section estimates the accommodation of a minimum of 24% shortening. Lower stratigraphy shows discrete, steeper, north-over-south dip-slip ductile shear zones that bound packages of less deformed Hongliuhe Group strata. Fault displacement is considered to have been prolonged enough to juxtapose basal formations in northerly hangingwalls against upper formations in southerly footwalls. Faulting is closely associated with the creation of large-scale brittle-ductile eye-fold structures that are postulated to be sheath folds. The most examined and mapped structure, 16km wide, is a synclinal structure with axes plunging steeply towards its center. The ellipticity of the exposed bedding traces increases towards the center of the eye-fold, implying a structural relationship with metamorphic shear zones. Except for large-scale folding, the bulk of its strata remain relatively undeformed and have preserved primary soft-sediment deformation structures indicating younging towards the center on both limbs of the synclinal structure. Stratigraphic reconstruction of the Hongliuhe Group that considers the significant faulting shows that the Group's basal conglomerates unconformably overlie a Late-Carboniferous volcanic assemblage. The clast lithotypes of the conglomeratic successions change from polymictic metamorphic rocks at the base to monomictic granitoid clasts mid-section, showing the gradual unroofing sequence of the provenance. The stratigraphic reconstruction shows a general fining upward sequence, transitioning from terrestrial to nearshore marine depositional environments that, and in conjunction with the conglomeratic successions, suggests that the tectonic setting for deposition of the Hongliuhe Group is a foreland basin. Considering the deformation styles reported in this study, the Hongliuhe Group is interpreted to be a foreland fold-and-thrust belt. Stratigraphic reconstruction of the Hongliuhe Group that considers the significant faulting shows that the Group’s basal conglomerates unconformably overlie a Late Carboniferous volcanic assemblage. The clast lithotypes of the conglomeratic successions change from polymictic metamorphic rocks at the base to monomictic granitoid mid-section, showing the gradual unroofing sequence of the provenance. The stratigraphic reconstruction shows a general fining upward sequence through nearshore depositional environments that, and in conjunction with the conglomeratic successions, give interpretation that the tectonic setting for deposition of the Hongliuhe Group is a foreland basin. Considering the deformation styles reported in this study the Hongliuhe Group is interpreted to be a foreland fold-and-thrust belt.

<p>This thesis uses geodetic satellite data to measure present-day crustal deformation in the Zagros fold-thrust belt (SW Iran). Geodetic-type measurements are also used in down-scaled models that simulate the surface deformations seen in convergent settings like the Zagros fold-thrust belt.</p><p>Global Positioning System (GPS) measurements of three surveys between 1998 and 2001 indicate 9 ± 3 mm/yr and 5 ± 3 mm/yr shortening across the SE and NW Zagros respectively. GPS results show that in addition to the different rates and directions of shortening on either side of the NS trending Kazerun fault, local along-belt extension occurs to the east. </p><p>Differential SAR interferograms of ERS1 & 2 images between 1992 and 1999 detect 8 ± 4 mm/yr uplift rate across a newly recognized fault in SW Qeshm Island. This can be attributed to a steep imbricate thrust that may still represent the local Zagros deformation front.</p><p>The salt diapirs in the Zagros rise from a source layer that acts as a low-frictional decollement that decouples the deformation of the cover sediments from their basement in the eastern Zagros whereas the cover to the west deforms above a high-friction decollement. Physical models were prepared to simulate cover deformation in the Zagros by shortening a sand pack above adjacent high- and low-frictional decollements (represented by a ductile layer). The strain distributions differed above the two types of decollements; it was more heterogeneous above the salt where local extension in the shortening direction was dominant. A separate work also investigated systematically the role of basal friction on cover deformation in convergent settings. Accurate height measurements of the model surface by laser-scanner indicated a deformation front more distal than usual, particularly in the low-basal frictional models. The volume reduction in our shortened sand models correlated directly with their basal friction.</p>

This thesis uses geodetic satellite data to measure present-day crustal deformation in the Zagros fold-thrust belt (SW Iran). Geodetic-type measurements are also used in down-scaled models that simulate the surface deformations seen in convergent settings like the Zagros fold-thrust belt. Global Positioning System (GPS) measurements of three surveys between 1998 and 2001 indicate 9 ± 3 mm/yr and 5 ± 3 mm/yr shortening across the SE and NW Zagros respectively. GPS results show that in addition to the different rates and directions of shortening on either side of the NS trending Kazerun fault, local along-belt extension occurs to the east. Differential SAR interferograms of ERS1 &amp; 2 images between 1992 and 1999 detect 8 ± 4 mm/yr uplift rate across a newly recognized fault in SW Qeshm Island. This can be attributed to a steep imbricate thrust that may still represent the local Zagros deformation front. The salt diapirs in the Zagros rise from a source layer that acts as a low-frictional decollement that decouples the deformation of the cover sediments from their basement in the eastern Zagros whereas the cover to the west deforms above a high-friction decollement. Physical models were prepared to simulate cover deformation in the Zagros by shortening a sand pack above adjacent high- and low-frictional decollements (represented by a ductile layer). The strain distributions differed above the two types of decollements; it was more heterogeneous above the salt where local extension in the shortening direction was dominant. A separate work also investigated systematically the role of basal friction on cover deformation in convergent settings. Accurate height measurements of the model surface by laser-scanner indicated a deformation front more distal than usual, particularly in the low-basal frictional models. The volume reduction in our shortened sand models correlated directly with their basal friction.

Structural analysis of surface and subsurface data from the Middle Magdalena Valley basin and Eastern Cordillera fold-thrust belt to construct a kinematic model for its Cenozoic structural and stratigraphic evolution. The La Salina west-vergent thrust system marks the boundary between the Paleogene foreland basin of the Middle Magdalena basin and the Eastern Cordillera fold-thrust belt. New low-temperature thermochonological and sandstone petrographic analyses provide constraints on ages of thrust deformation and sediment dispersal. Apatite fission track (AFT) and U-Th/He thermochronological results show the timing of three structural events along the La Salina fault system: (1) late Eocene-early Oligocene (~43–35 Ma) initial hanging wall exhumation; (2) continued middle Miocene (~15 Ma) exhumation; and (3) continued but more rapid late Miocene (~12–3 Ma) hanging wall exhumation. Vitrinite reflectance results provide estimates of maximum burial depths for the hanging wall of the La Salina fault ranging from 4 to 6 km., this depth of burial estimates constrain the basin geometry during its late Eocene to late Miocene evolution. The eastern hanging wall of the La Salina fault displays a broad anticline-syncline pair affecting Cretaceous to Eocene strata with no significant faulting, whereas the western footwall contains a complex series of tight, thrust-related folds in Eocene-Quaternary strata. For foreland basin province, a proposed triangle zone accommodates a small amount of east-west shortening (< 1000 m) along the frontal thrust system by east-vergent backthrusting within a broader passive-roof duplex. East-west shortening in the Cenozoic stratigraphic section was also accommodated by detachment folding, which produced localized areas of steep dips. In the proposed kinematic restoration, the most recent phase of deformation represents out-of-sequence reactivation of the La Salina fault that is consistent with irregular crosscutting relationships of some footwall structures. Earliest exhumation by ~45–30 Ma in the Eastern Cordillera fold-thrust belt province matches (1) an increased proportion of sedimentary lithic fragments; and (2) a high degree of compositional maturity (Q88F4Lf8). Exhumation since ~15 Ma in the foreland province coincides with (1) the highest accumulation rates observed for the upper Miocene Real Group; and (2) a decrease in compositional maturity (Q55F8Lf36). / text

Debate persists on the timing, magnitude and style of crustal shortening, uplift and basin evolution in the Andes. Many studies suggest that the central Andes, including the Altiplano plateau, were gradually uplifted as a result of protracted Cenozoic retroarc shortening. However, recent isotopic studies conclude that the Andes instead rose in pulses, with the most significant event occurring at 10-6 Ma. Many researchers attribute these rapid pulses of uplift to lower lithosphere delamination events. A better understanding of the history of Cenozoic crustal shortening is essential for determination of the mechanism(s) of Andean uplift. The well-exposed Cenozoic San Jerónimo Group was studied in the Ayaviri basin of the northern Altiplano in southern Peru. The 3-5 km-thick succession is situated at 3900-4800 m elevation, between the Western Cordillera magmatic arc and the Eastern Cordillera fold-thrust-belt. New detrital zircon U-Pb geochronological results from four sandstones and one reworked tuff in the San Jerónimo succession show large age populations indicative of syndepositional volcanism between approximately 38 and 27 Ma. A 1600-m-thick magnetostratigraphic section further constrains the depositional timing and accumulation rate of the upper portion of the succession. Sedimentological observations show a rapid transition from cross-stratified braided-fluvial sandstones to proximal channel-fill and alluvial-fan conglomerates at ~30 Ma. Paleocurrent measurements show important temporal and spatial variations in sediment dispersal patterns while conglomerate clast counts show an upsection transition from almost exclusively volcanic input to increasing contributions of clastic, quartzite, and limestone detritus. The corresponding shifts in depositional environment and sediment provenance are attributed to the activation of new thrust structures in close proximity to the basin, namely the Pucapuca-Sorapata fault system, indicating the presence of an eastward advancing fold-thrust belt dating to at least 38 Ma and reaching the Ayaviri basin within the northern Altiplano plateau at ~30 Ma. / text