The Olympic Mountains in northwestern Washington, USA are defined by the arcuate shape of the basaltic Crescent Formation (Fm.) that wraps a faulted and folded meta-sedimentary core. This area was developed through accretion and exhumation by subduction-related processes, but how this relates to the deformational history of the area is not fully understood. The region has been mapped geologically, however little focus has been placed on interpreting meso-scale structures. This study investigates structures along a transect where the Hamma Hamma River crosses the Hurricane Ridge Fault, which juxtaposes the meta-sedimentary core (west) and the basaltic Crescent Fm. (east). In the study area, the meta-sedimentary unit is characterized by outcrop scale folding with a calculated fold axis of 69-->342 and a penetrative foliation with a representative orientation of (178, 75). The folds and foliation are crosscut by two fracture populations with representative orientations of (115, 61) and (303, 76). The pillow basalts of the Crescent Fm. are near vertical, N-S striking beds that are cut by four fault groups. Fault Groups A and B have representative orientations of (304, 37) and (207, 59), respectively, and are associated with similarly oriented fracture populations. Fault Group C crosscuts Groups A and B and has a representative orientation of (031, 61). Fault Group D runs subparallel to the outcrop, cuts all other faults, and has a representative orientation of (087, 50). From an interpretation of this data, a deformation model is presented that proposes three distinct periods of deformation under three different states of stress. The first period was dominated by E-W or ENE-WSW oriented compression, followed by a period of N-S or NNW-SSE oriented compression, followed by vertical compression.

Southern North Sea Basin is one of the mature hydrocarbon basins in NW Europe and is shaped by a number of phases of tectonic deformations during the Phanerozoic. In addition, mobilization and halokinesis of thick Permian Zechstein Salt has enhanced and contributed to the deformation of the region since Triassic, which further complicated the geology of the region. The Friesland Platform, which is a stable platform area located in northern Netherlands, experienced the main deformation phases that Europe has been endured together with the deformation of Permian Zechstein salt. In this study a computer based 3D modeling has been carried out within the Friesland Platform with the use of 3D seismic and borehole data in order to delineate structural elements and geological development of the area with special emphasis on the salt tectonic deformation. The model was constructed by picking key horizons and major faults from the seismic sections in time domain and then migrated into depth domain. The stratigraphy of the area is correlated with horizons by well-seismic matching. The model includes major structures and seismostratigraphic units of Permian to recent, revealing salt and salt induced structures formed during the periods of active salt movements. Thick Zechstein salt layers deposited in N-S-oriented grabens and half grabens of South Permian Basin acted as the primary control for the location of salt diapirs and are reflected on the overburden without a direct continuation (unlinked) of the basement faults into the overburden. The mapped N-S oriented salt-cored anticline and a convergent conjugate transfer zone between a pair of segmented normal growth faults at the crest of the anticline are controlled by the ascent of the Zechstein salt.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 103-112).

Alkalic porphyry style Au-Cu deposits of the Cadia district are associated with Late-Ordovician monzonite intrusions, which were emplaced during the final phase of Macquarie Arc magmatism at the end of the Benambran Orogeny. N-striking faults, including the curviplanar, northerly striking, moderately west-dipping basement thrust faults of the Cadiangullong system, developed early in the district history. NE-striking faults formed during rifting in the late Silurian. Subsequent E-W directed Siluro- Devonian extension followed by regional E-W shortening during the Devonian Tabberabberan Orogeny dismembered these intrusions, thereby superposing different levels porphyry Au-Cu systems as well as the host stratigraphy. During the late Silurian, the partially exhumed porphyry systems were buried beneath the Waugoola Group sedimentary cover sequence, which is generally preserved in the footwall of the Cadiangullong thrust fault system. The Waugoola Group is a typical rift-sag sequence, deposited initially in local fault-bounded basins which then transitioned to a gradually shallowing marine environment as local topography was overwhelmed. Basin geometry was controlled by pre-existing basement structures, which were subsequently inverted during the Devonian Tabberabberan Orogeny, offsetting the unconformity by up to 300m vertically. In the Waugoola Group cover, this shortening was accommodated via a complex network of minor detachments that strike parallel to major underlying basement faults. For this reason, faults and folds measured at the surface in the sedimentary cover can be used as a predictive tool to infer basement structures at depth.

Study area, the Yeni&ccedil / aga Basin, is located in the western part of the North Anatolian Fault System. It is a 1-5-km-wide and 14-km-long WSWENE- trending depression bounded by a complex array of strike-slip faults. The Yeni&ccedil / aga Basin is interpreted to be a fault &ndash / wedge basin with the North Anatolian Fault&rsquo / s System Master Strand, namely the Gerede Fault, cutting across the basin itself. The basin and its surroundings contain mainly two groups of rock units namely the paleotectonic units and the neotectonic units. Paleotectonic units, which are deposited or formed during different phase(s) of tectonic regimes, comprise several formations. The most important one of these formations is the Upper Miocene &ndash / Lower Pliocene Eskipazar formation which plays an important role in understanding the evolutionary history of the basin. Neotectonic unit deposited under the control of today&rsquo / s tectonic regime is the Plio-Quaternary Betem&uuml / rl&uuml / formation.v Betem&uuml / rl&uuml / formation unconformably overlies the paleotectonic Eskipazar formation throughout the study area and the unconformity separating these two units corresponds to the time interval during which the paleotectonic stress regime changed into the neotectonic stress regime. Thus, onset age of the strike-slip neotectonic regime in the study area is Late Pliocene (~ 2,6 My). Common basin margin-bounding faults of the Yeni&ccedil / aga Basin are, the ASagi Kuldan fault, the Aksu fault, the izmirli fault set, the Saray&ccedil / ali fault, the Degirmen fault set and the Hamzabey fault set. They display well-preserved fault scarps in places. Morphological expressions of these faults and their geometrical relationships with the local stress regime indicate that these faults are mainly strike-slip and oblique-slip faults. Morphotectonic expressions of the faults exposing within the study area indicate that these faults are active. Most of the settlements within the study area are located on water-saturated loose basin fill nearby the active faults. Hence, these are open to future earthquake hazards. Therefore, structures and settlements have to be constructed on strong grounds away from the active faults.

Alkalic porphyry style Au-Cu deposits of the Cadia district are associated with Late-Ordovician monzonite intrusions, which were emplaced during the final phase of Macquarie Arc magmatism at the end of the Benambran Orogeny. N-striking faults, including the curviplanar, northerly striking, moderately west-dipping basement thrust faults of the Cadiangullong system, developed early in the district history. NE-striking faults formed during rifting in the late Silurian. Subsequent E-W directed Siluro- Devonian extension followed by regional E-W shortening during the Devonian Tabberabberan Orogeny dismembered these intrusions, thereby superposing different levels porphyry Au-Cu systems as well as the host stratigraphy. During the late Silurian, the partially exhumed porphyry systems were buried beneath the Waugoola Group sedimentary cover sequence, which is generally preserved in the footwall of the Cadiangullong thrust fault system. The Waugoola Group is a typical rift-sag sequence, deposited initially in local fault-bounded basins which then transitioned to a gradually shallowing marine environment as local topography was overwhelmed. Basin geometry was controlled by pre-existing basement structures, which were subsequently inverted during the Devonian Tabberabberan Orogeny, offsetting the unconformity by up to 300m vertically. In the Waugoola Group cover, this shortening was accommodated via a complex network of minor detachments that strike parallel to major underlying basement faults. For this reason, faults and folds measured at the surface in the sedimentary cover can be used as a predictive tool to infer basement structures at depth.

The Mount Isa and May Downs Faults are part of a network of significant faults that define, control, or partition deformation in the Early to mid-Proterozoic Mount Isa Inlier. The middle Proterozoic deformation history includes at least two extensional basin-forming events (Leichhardt Superbasin: ~1800 Ma to ~1700 Ma and Isa Superbasin: ~1700 Ma to ~ 1600 Ma) and a major protracted contractional orogenic event (Isan Orogeny: ~1585 Ma to ~ 1500 Ma). Uplift between the Mount Isa and May Downs Faults during the Isan Orogeny has exposed mid to upper amphibolite facies rocks of the structurally deeper levels of the early rift systems. Also exposed is the Sybella Granite, a composite batholith of variably deformed gneissic granite, which, at ~1660 Ma, is broadly coeval with inception of the Isan Superbasin basin. Two prevailing kinematic models had been proposed for the fault systems during Isan Superbasin formation. The traditionally accepted model involves episodic E-W or NW-SE extension with the N-S Mount Isa Fault, but Southgate et al (2000b) presented an alternative sinistral strike-slip model in which the May Downs Fault acted as a releasing bend fault associated with motion on the Mt Isa Fault. In the Southgate model, the Sybella Granite was interpreted as syn-tectonically filling the dilational releasing bend. This study provides a detailed structural analysis of the 100 km by 40 km area west of Mount Isa City lying between the Mount Isa and May Downs Faults. The aim was to resolve a number of outstanding issues, including those outlined above. The resultant 1:250 000 structural map of the area is based on: reconnaissance-scale mapping; aerial photography, satellite, magnetic and radiometric image interpretation; field observations at locations throughout the area; and local detailed mapping (1:12000 scale or less). The mapping and associated geometrical analysis of the area has shown that the Sybella Batholith consists of two granite sills and a more globular body of microgranite. The deepest, gneissic, sill is up to 5 km thick and was emplaced at about 15 km below the basal Mount Isa Group unconformity (palaeosurface). The other, less deformed, sill formed higher in the crust, and the microgranite intruded to within 1-2 km of the palaeosurface. The two sills are located between two major fault systems (Mount Isa and May Downs Faults) that developed from inherited basin margin faults. The fault systems dip toward each other and the rocks between them have been folded into a single large antiform and uplifted as a wedge. Previous interpretations of the area have suggested that the batholith consists of a single sill folded by tighter, shorter wavelength folds. A cross-sectional reconstruction of the study area suggests that thin-skinned processes dominated much of the Isan Orogeny, contrary to previous interpretations. A three-dimensional reconstruction of the area, evaluated by comparing the predicted strain and amount of shortening with measured strain and shortening estimates, suggests deformation was driven by a rigid block to the west of the May Downs Fault moving toward the northeast. In the restored pre-Isan geometry, both the margins of the lowermost gneissic granite sill and its immediate country rocks have a strong, horizontal, layer-parallel, shear foliation with top-to-the-east asymmetry. The fabrics are strongly constrictional and 2 Abstract the stretching lineation trends east-west. Field observations and thin sectional analysis of these fabrics provide positive evidence that the Sybella Batholith was syn-tectonically emplaced in a basin-forming environment. A kinematic model is presented to show that these features are consistent with granite emplacement into a dilational jog in a sub-horizontal shear zone with a top-to-the-east shear sense. A component of east-west directed horizontal simple shear across the dilating zone explains the strongly constrictional fabrics in the granite. Under these conditions significant north-south shortening in the deforming zone leads to the initiation of folds parallel to the stretching direction (as observed). The shear zone into which the granite was emplaced developed at about fifteen kilometres depth and was probably at or near the brittle-ductile transition. The consistent shear sense, very high strains and implied 30 km of translation required to accommodate the sill indicates that this was a major crustal structure, rather than a simple detachment at the brittle-ductile transition in a crustal pure shear extension. The results are consistent with the east-west extensional model for basin development and totally inconsistent with the sinistral strike-slip model.

The Mount Isa and May Downs Faults are part of a network of significant faults that define, control, or partition deformation in the Early to mid-Proterozoic Mount Isa Inlier. The middle Proterozoic deformation history includes at least two extensional basin-forming events (Leichhardt Superbasin: ~1800 Ma to ~1700 Ma and Isa Superbasin: ~1700 Ma to ~ 1600 Ma) and a major protracted contractional orogenic event (Isan Orogeny: ~1585 Ma to ~ 1500 Ma). Uplift between the Mount Isa and May Downs Faults during the Isan Orogeny has exposed mid to upper amphibolite facies rocks of the structurally deeper levels of the early rift systems. Also exposed is the Sybella Granite, a composite batholith of variably deformed gneissic granite, which, at ~1660 Ma, is broadly coeval with inception of the Isan Superbasin basin. Two prevailing kinematic models had been proposed for the fault systems during Isan Superbasin formation. The traditionally accepted model involves episodic E-W or NW-SE extension with the N-S Mount Isa Fault, but Southgate et al (2000b) presented an alternative sinistral strike-slip model in which the May Downs Fault acted as a releasing bend fault associated with motion on the Mt Isa Fault. In the Southgate model, the Sybella Granite was interpreted as syn-tectonically filling the dilational releasing bend. This study provides a detailed structural analysis of the 100 km by 40 km area west of Mount Isa City lying between the Mount Isa and May Downs Faults. The aim was to resolve a number of outstanding issues, including those outlined above. The resultant 1:250 000 structural map of the area is based on: reconnaissance-scale mapping; aerial photography, satellite, magnetic and radiometric image interpretation; field observations at locations throughout the area; and local detailed mapping (1:12000 scale or less). The mapping and associated geometrical analysis of the area has shown that the Sybella Batholith consists of two granite sills and a more globular body of microgranite. The deepest, gneissic, sill is up to 5 km thick and was emplaced at about 15 km below the basal Mount Isa Group unconformity (palaeosurface). The other, less deformed, sill formed higher in the crust, and the microgranite intruded to within 1-2 km of the palaeosurface. The two sills are located between two major fault systems (Mount Isa and May Downs Faults) that developed from inherited basin margin faults. The fault systems dip toward each other and the rocks between them have been folded into a single large antiform and uplifted as a wedge. Previous interpretations of the area have suggested that the batholith consists of a single sill folded by tighter, shorter wavelength folds. A cross-sectional reconstruction of the study area suggests that thin-skinned processes dominated much of the Isan Orogeny, contrary to previous interpretations. A three-dimensional reconstruction of the area, evaluated by comparing the predicted strain and amount of shortening with measured strain and shortening estimates, suggests deformation was driven by a rigid block to the west of the May Downs Fault moving toward the northeast. In the restored pre-Isan geometry, both the margins of the lowermost gneissic granite sill and its immediate country rocks have a strong, horizontal, layer-parallel, shear foliation with top-to-the-east asymmetry. The fabrics are strongly constrictional and 2 Abstract the stretching lineation trends east-west. Field observations and thin sectional analysis of these fabrics provide positive evidence that the Sybella Batholith was syn-tectonically emplaced in a basin-forming environment. A kinematic model is presented to show that these features are consistent with granite emplacement into a dilational jog in a sub-horizontal shear zone with a top-to-the-east shear sense. A component of east-west directed horizontal simple shear across the dilating zone explains the strongly constrictional fabrics in the granite. Under these conditions significant north-south shortening in the deforming zone leads to the initiation of folds parallel to the stretching direction (as observed). The shear zone into which the granite was emplaced developed at about fifteen kilometres depth and was probably at or near the brittle-ductile transition. The consistent shear sense, very high strains and implied 30 km of translation required to accommodate the sill indicates that this was a major crustal structure, rather than a simple detachment at the brittle-ductile transition in a crustal pure shear extension. The results are consistent with the east-west extensional model for basin development and totally inconsistent with the sinistral strike-slip model.

Thesis (M.S.)--Miami University, Dept. of Geology, 2005. / Title from first page of PDF document. Document formatted into pages; contains [1], iv, 38 p. : ill. Includes bibliographical references (p. 35-38).

O trabalho foi desenvolvido no litoral norte do estado de São Paulo, onde ocorrem boas exposições de rochas intrusivas da porção meridional do Enxame de Diques da Serra do Mar, de idade eocretácica. O objetivo principal da dissertação é caracterizar os regimes tectônicos associados à colocação e à deformação de diques máficos na área de São Sebastião (SP) e sua distribuição espacial, a partir de interpretações de imagens de sensores remotos, análise de dados estruturais de campo e descrição petrográfica das rochas ígneas. A área apresenta grande complexidade no tocante ao magmatismo, uma vez que ocorrem diques de diabásios toleítico e alcalino, lamprófiro e rochas alcalinas félsicas como fonolitos, traquitos e sienitos, estes sob a forma diques, sills e plugs. Os diabásios toleíticos tem idades em torno 134 Ma, correlatas com o início do rifteamento sul-atlântico, enquanto que as rochas alcalinas datam de 86 Ma e estão relacionadas com um magmatismo intraplaca posterior. Os lineamentos estruturais orientam-se majoritariamente na direção ENE-WSW, paralela às foliações metamórficas e zonas de cisalhamento observadas no campo e descritas na literatura, referentes ao Domínio Costeiro da Faixa Ribeira. Os diques se orientam na direção NE-SW, com azimute semelhante porém ângulos de mergulho discordantes da foliação em grande parte da área, onde as foliações são de baixo ângulo. Um segundo conjunto de lineamentos orientado NW-SE ocorre como um importante conjunto de fraturas que cortam tanto as rochas do embasamento proterozóico quanto as rochas alcalinas neocretácicas. Diques com esta orientação são escassos. Um terceiro conjunto NNE-SSW ocorre na porção oeste da área, associado à presença de diques de diabásio que por vezes mostram indicadores de movimentação sinistral. A análise cinemática dos diques mostra um predomínio de distensão pura durante sua colocação, com um tensor de compressão mínima de orientação NW-SE, ortogonal ao principal trend dos diques. Componentes direcionais, por vezes ambíguas, são comumente observadas, com um discreto predomínio de componente sinistral. O mesmo padrão cinemático é observado para os diques toleíticos e para os alcalinos, sugerindo que o campo de tensões local pouco variou durante o Cretáceo. Embora o embasamento não tenha sido diretamente reativado durante a colocação dos diques, sua anisotropia pode ter controlado de certa forma a orientação do campo de tensões local durante o Cretáceo. Os mapas geofísicos da bacia de Santos existentes na literatura sugerem certo paralelismo entre as estruturas observadas na área de estudo e aquelas interpretadas na bacia. As estruturas NNE-SSW são paralelas ao trend das sub-bacias e ao gráben de Merluza, enquanto que as estruturas NW-SE são paralelas a zonas de transferência descritas na literatura. / The study was developed at the northern coast of São Paulo state, southeastern Brazil, where there are good exposures of intrusive rocks of the southern portion of the Early Cretaceous Serra do Mar Dyke Swarm. The main purpose is to define the tectonic regimes related to the emplacement and deformation of mafic dykes in the area of São Sebastião (SP) and their spatial and relative temporal distribution, based on interpretations of remote sensing images, field analysis of structural data, and petrographic description of igneous rocks. The area is quite complex in terms of Cretaceous magmatim, since there are dolerite dykes (tholeiitic and alkaline), lamprophyric dykes and felsic alkaline rocks (mainly phonolites, trachytes and syenites) which occur as dykes, sills and plugs. The tholeiitic dolerites yield ages around 134 Ma, related to the early South Atlantic rifting, while the alkaline rocks are dated as 86 Ma and are related to a subsequent intraplate magmatism. The structural lineaments are oriented mostly ENE-WSW, parallel to the metamorphic foliation and shear zones observed in the field and described in the literature, as part of the Costeiro Complex of the Ribeira Belt. The dykes are oriented NE-SW, with similar azimuth but different dip angles compared to the foliations, which are gently dipping in many areas. A second set of lineaments oriented NW-SE occurs as a major set of brittle fractures which cut both the Proterozoic rocks and the Late Cretaceous alkaline rocks. Dykes with this orientation are scarce. A third set oriented NNE-SSW occurs in the western area associated with some dolerite dykes which sometimes show evidence of sinistral component during emplacement. The kinematic analysis of the dykes shows a predominance of pure extension during emplacement, with an extension direction oriented NW-SE, orthogonal to the main dyke trend. Directional components, sometimes ambiguous, are commonly observed, with a slight predominance of sinistral components. The same kinematic pattern is observed for both tholeiitic and alkaline dykes, so that the local stress field orientation remained unaltered during the Cretaceous. Although the basement has not been directly reactivated during dyke emplacement, their anisotropies can account for some control on the orientation of the local stress field during the Cretaceous. The available geophysical maps of the Santos Basin suggest certain parallelism among the structures observed in the study area and those interpreted in the basin. The NNE-SSW trending structures are parallel to the trend of sub-basins and to the Merluza graben, while the NW-SE structures are parallel to transfer zones described in the literature.