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<p>Erosion, in its many forms, is thought to have a measurable impact on the development and evolution of mountain belts. In this work, we examine the response of physical scaled (analog) Coulomb wedges to different erosional styles. Data is collected in the form of velocimetry data within images of these models, using particle image velocimetry (PIV) and particle tracking velocimetry (PTV), with each dataset rendering whole wedge slip magnitude fields and material pathways, respectively. Results for channelized glacial erosion models demonstrate a significant focusing of faulting below the glacial channel itself, as well as a shift of the locus of greatest exhumation to within the channel. This shift in the locus of exhumation also allows for deep material to make it to the model surface, with models featuring a strong basal décollement having higher amounts of exhumation than those with weaker basal décollements. This same pattern is seen with regards to fault slip and shortening, with stronger décollement allowing for greater slip and more shortening. Increases in erosion magnitude are also seen as increasing total fault slip as well. With regards to thermal conditions and surface heat flow, we highlight that increasing erosion increases heat flow and temperatures within the wedge. Using Pressure-Temperature-time (P-T-t) pathways, we also see that the inclusion of weak material stratigraphy allows for duplexing and subsequent exhumation of deep-seated material, leading to complex thermal histories. Overall, we see erosion localization and magnitude being proportional to the magnitude of fault activity, and that this increased fault activity allows for deep-seated material to be exhumed from the system.  </p> <p>  </p>

<p>This thesis addresses the spatial distribution of structures and deformation geometry in the southern Sudbury Basin, Ontario, a synclinal fold basin. Major components are low-temperature fabric development in the Sudbury Igneous Complex (SIC), the relation between fabrics and fold structures in Huronian rocks, and kinematic modeling of deformation of the southern Sudbury Basin. These topics lead to a synthetic model of the structural history of the SIC and its host rocks. Analysis of structures in the Norite layer of the SIC shows that this unit deformed under a single deformation regime and variable rheological conditions. This is evident by foliation planes, folded granitoid dikes, brittle shear faults and ductile high-strain zones. Brittle deformation preceded the formation of foliation planes and caused hydrolytic weakening of the Norite. Bulk thinning led to steepening of lithological contacts and igneous layering in the SIC. Structures in Huronian rocks and Sudbury Breccia display components of post-impact deformation that cannot be accounted for by thrusting along a high-strain zone, the so-called South Range Shear Zone, and by large-scale folding of the SIC. Shape change of the SIC from a convex outward to concave inward geometry led to basin-concentric shortening, the formation of a buckle fold of the SIC and axial-planar fabrics in Huronian rocks. Mutually perpendicular fabric orientations compatible with overall NW-SE shortening indicate that discordant foliations can form as a consequence of local strain perturbations near lithological contacts. Kinematic modelling of deformation based on field-based structural data tests the validity of trishear fault propagation folding as a possible deformation mechanism for the southern Sudbury Basin. Trishear deformation of the central South Range accounts for angular discordances between the upper and basal contacts of the SIC, local overturning of southern SIC, steepening of foliation planes, strain gradients in the Sudbury Basin, and thickness variations of SIC layers. Implications are shallowly dipping SIC layers both at greater depths and above the current erosion level, translation of Huronian rocks, and thinning in a section of the trishear zone manifested at surface by the South Range Shear Zone.</p> / Doctor of Philosophy (PhD)

Active seismicity and volcanism north of Washington state’s Mount St. Helens provide key ingredients for hydrothermal circulation at depth. This broad zone of seismicity defines the St. Helens Seismic Zone, which extends well north of the volcanic edifice below where several faults and associated fractures in outcrop record repeated slip, dilation, and alteration indicative of localized fluid flow. Candidate reservoir rocks for a geothermal system include marine metasediments overlain by extrusive volcanics. The colocation of elements comprising a geothermal system at this location is tested here by analysis of the structures potentially hosting a reservoir, their relationship to the modern stress state, and temperature logs to a depth of 250 m. Outcrop mapping and borehole image log analysis down to 244 m document highly fractured volcaniclastic deposits and basalt flows. Intervening ash layers truncate the vertical extent of most structures. However, large strike slip faults with well-developed fault cores and associated high fracture density cross ash layers; vein filling and alternation of the adjacent host rock in these faults suggest they act as vertically extensive flow paths. These faults and associated fractures record repeated slip, dilation, and healing by various dolomite, quartz, and hematite, as well as clay alteration, indicative of long-lived, localized fluid flow. In addition, where these rocks are altered by igneous intrusion, they host high fracture density that facilitated heat transfer evidenced by associated hydrothermal alteration. Breakouts in image logs indicate the azimuth of SHmax in the shear zone is broadly consistent with both the GPS plate convergence velocity field as well as seismically active strike slip faults and strike-slip faults mapped in outcrop and borehole image logs. However, the local orientation of SHmax varies by position relative to the edifice and in some cases with depth along the borehole making a simple regional average SHmax azimuth misleading. Boreholes within the seismic zone display a wider variety of fracture attitudes than those outside the shear zone, potentially promoting permeability. Temperature profiles in these wells all indicate isothermal conditions at average groundwater temperatures, consistent with rapidly flowing water localized within fractures. Together, these results indicate that the area north of Mount Saint Helens generates and maintains porosity and permeability suggesting that conditions necessary for a geothermal system are present, although as yet no modern heat source or hydrothermal circulation was detected at shallow depth. / Geology

Intraplate tectonics is generally not well documented and understood, despite its significance for seismic hazards in areas such as southeastern Canada. Neotectonics is even less well understood in these regions. This study focuses on providing an in-depth analysis of potential neotectonic pop-up structures in southern Ontario, Canada, leading to a comprehensive definition of what pop-up structures are, to constrain the processes involved in neotectonism, and to determine the extent to which neotectonism impacts the region. Previous literature has hypothesized that neotectonic structures have a likely potential to be linked to reactivated structures within the Precambrian Basement rocks of the Canadian Shield. In addition to documenting new potential neotectonic structures, this work provides a brief overview of tectonics in southern Ontario, and how previously measured lineaments in the Precambrian Basement may align with observable, potentially neotectonic surface structures. Three locations in southern Ontario were documented using a combination of ground and drone-based structural analysis: 1) Fletcher Creek Ecological Preserve, 2) Wainfleet Wetlands Conservation Area, and 3) multiple sites on Manitoulin Island. These sites were chosen where previous studies had documented neotectonic activity, and/or where initial geomorphic analyses indicated the possibility of a pop-up structure. All sites are located within the Silurian to Devonian cover rocks of the Niagara Escarpment. Fracture patterns at each site were analyzed using ground-based measurements using FieldClino and/or drone-based photogrammetry (DJI Phantom 4 V2 and Phantom 4 Pro acquisition followed by analysis in Pix4D and Drone2Map), where applicable. Where access permitted, ground-based measurements iv were obtained on structures, in addition to RTK-DGPS (Real Time Kinematic Differential Global Positioning System) profiles over potential pop-up structures. Analysis revealed that pop-up structures exhibit a distinct geomorphic expression, manifesting as a near-linear elevated ridge, where stress relief features have variable geomorphic expressions, such as domes. In southern Ontario, the presence of these pop-ups and stress relief features demonstrates that the region is tectonically active, despite often being characterized as a stable continental interior. This study adds to a growing body of work documenting neotectonics in southern Ontario, with several stress-related structures documented for the first time in this study, showing their prevalence over a wide area. The results of this study were used to create an updated tectonic hazard map of Ontario. / Thesis / Master of Science (MSc)

Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The Central Zone (CZ) of the Damara belt in central Namibia is underlain by voluminous Pan-African granites and is host to numerous pegmatite occurrences, some of which have economic importance and have been mined extensively. This study discusses the occurrence, geometry, relative timing and emplacement mechanisms for the Usakos pegmatite field, located between the towns of Karibib and Usakos and within the core of the regional-scale Kranzberg syncline. Lithological mapping of the Kuiseb Formation in the core of the Kranzberg syncline identified four litho-units that form an up to 800 m thick succession of metaturbidites describing an overall coarsening upward trend. This coarsening upwards trend suggests sedimentation of the formation’s upper parts may have occurred during crustal convergence and basin closure between the Kalahari and Congo Cratons, rather than during continued spreading as previously thought. The Kranzberg syncline is a regional-scale NW verging, NE-SW trending, strongly non-cylindrical structure that consists of a moderately SE dipping, normal NW limb and a steep- to overturned SE limb. First- and lower-order folds show relatively consistent E - SE plunges at moderate angles and stretching lineations and boudinage of competent layers point to a fold-parallel stretch during folding. Folding is associated with a moderate- to steep SE dipping transecting foliation that shows a consistent anticlockwise rotation with respect to the axial plane of the fold. The transecting cleavage and a component of non-coaxial shear along the overturned limb suggest that folding was accomopanied by a dextral component of shear thought to be related to the SW-directed extrusion of the adjacent Usakos dome during regional NW-SE directed shortening. It is further suggested that the Kranzberg syncline evolved within the overall regional pattern of regional dome and syncline structures in the sCZ, and not as a forced fold in response to the formation of neighbouring dome structures. Based on cross-cutting relationships and deformation, four main generations of bedding-concordant sills and bedding-discordant pegmatite dykes were identified. Along the normal limb, shallowly-dipping sills dominate, highlighting the significance of bedding anisotropies for sheet propagation. Along the overturned limb, interconnected dyke and sill geometries co-exist. Here, pegmatite emplacement appears to have been influenced by (1) the regional strain, (2) differing wall rock rheologies; (3) the orientation of pre-existing anisotropies; and (4) driving melt pressures. Dykes within the Usakos pegmatite field formed within dilational sites, at high angles to the regional stretch, whereas sills formed at high angles to the regional shortening strain and in contractional sites. Where driving pressures for melt ascent were high enough, an interconnectivity of dykes and sills and subsequent melt transfer from contractional into dilational sites is developed. Where melt pressures dropped below a critical value pegmatites were arrested, thus preserving the ascent pathways of the melts. These complex intersecting melt pathways are developed throughout the Kranzberg syncline. This suggests the existence of fairly stable melt networks in the continental crust. This geometrical complexity also accounts for the stockwork-like structures observed in pegmatite fields. / AFRIKAANSE OPSOMMING: Die Sentrale Sone (CZ) van die Damara gordel in sentrale Namibië is onder lê deur volumineuse Pan-Afrikaanse graniete en speel gasheer vir talle pegmatiet voorkomste, waarvan party van ekonomiese belang is en is ekstensief ontgin. Hierdie studie bespreek die voorkoms, geometrie, relatiewe tydsberekening en inplasing meganismes vir die Usakos pegmatiet gebied, wat tussen die stede van Karibib en Usakos en wat binne die kern van die regionale-skaal Kranzberg sinklien geleë is. Litologiese kartering van die Kuiseb Formasie in die kern van die Kranzberg sinklien het vier lito-eenhede geidentifiseer. Hierdie eenhede, wat saam tot 'n 800 m dik opeenvolging van metaturbidiete vorm, beskryf ‘n algemene opwaartse vergrowwing neiging. Hierdie tendens dui aan dat sedimentasie van die Formasie se boonste dele tydens die aardkorst konvergensie en kom sluiting tussen die Kalahari en die Kongo kratons voorgekom het, eerder as in 'n oseaanvloerverbreiding omgewing soos voorheen gedink was. Die Kranzberg sinklien is 'n regionale-skaal struktuur met ‘n NW vergensie, ‘n NOSW koersing, wat sterk nie-silindries is en wat uit 'n matige SO helling, normale NW flank en 'n steil-tot omgeslaande SO flank bestaan. Eerste-en laer-orde plooie vertoon relatief konsekwent matige O - SO duikings en strek lineasies en boudinage van kompetent lae dui 'n plooi parallel strek tydens plooiing aan. Plooiing is geassosieer met 'n ongeveer aksiale planêre, matig- tot steil SO helling foliasie wat omstandig waargeneem word om 'n konsekwente antikloksgewyse rotasie met betrekking tot die aksiale vlak van die plooi te hê. Hierdie antikloksgewyse rotasie is ‘n bewyse vir 'n komponent van nie-koaksiale regse skuifskeur deur die omgekeerde flank en dui dit ook aan dat 'n regse komponent van skeer gedurend of na plooiing plaasgevind het. Daar is gedink dat die regse komponent van skeur in verband met die laterale, SW-gerig extrusie van die aangrensende Usakos koepel gedurende plaaslike NW-SO verkorting ontwikkel het. Dit is verder voorgestel dat die Kranzberg sinklien binne die totale patroon van plaaslike koepel en sinklien strukture in die sCZ geontwikkel het, en nie as 'n gedwonge plooi in reaksie op die formasie van die naburige koepel strukture (bv. Usakos koepel). Gebaseer op kruis-sny verhoudings en deformasie, was vier generasies van gelaagdheid-konkordant plate en gelaagdheid-diskordant pegmatiet dyke geïdentifiseer. In die normale flank, vlak-helling plate oorheers, wat die belangerikheid van die laagvlak-anisotropiese op plaat voortplanting beklemtoon. In die steil, omgekeerde flank, bestaan onderlinge verbinde dyk en plaat geometrië gelyktydig. Hier is pegmatiet inplasing blykbaar beïnvloed deur (1) die regionale span; (2) verskillende wandgesteentes reologië; (3) die oriëntasies van anisotropie (ie. gelaagdheid ); en (4) smeltsel druk. Dyke in die Usakos pegmatiet gebied het binne dilatasionele liggings, teen hoë hoeke aan die regionale strek gevorm, terwyl plate teen hoë hoeke aan die plaaslike verkorting span en in kontraksionele liggings gevorm het. Waar smeltsel druk hoog genoeg was, is 'n onderlinge verbinding van dyke en plate, en die daaropvolgende smeltsel oordrag van kontraksionele liggings na dilatasionele liggings behou. In teenstelling, waar smeltsel druk onder 'n kritieke waarde geval het, word die pegmatiete geblokeer, en dus kan die behoude smeltsel styging paaie waargeneem word. Hierdie snyende smeltsel geometrië, in beide kontraksionele en dilatasionele liggings dui aan dat redelik stabiele smeltsel netwerke in die kontinentale kors kan bestaan en verder kan en verklaar die algemene stokwerk-agtige strukture wat in pegmatiet velde van ander mid-korstige omgewings waargeneem word.

The Giant and Con deposits, Yellowknife, Northwest Territories, represent a classic Archean lode-gold deposit now offset by a major Proterozoic fault (West Bay Fault). The link between the Giant and Con deposits is supported by their similarities. However, there are distinct differences between the two deposits in terms of the offset of stratigraphy, response to D2 deformation, geometry, gold mineralization styles, and depth of gold mineralization. Gold mineralization in the Giant-Con system formed over a protracted history of deformation and hydrothermal activity. Early D1 extension resulted in offset and excision of stratigraphy and the formation of refractory gold mineralization within strongly deformed schistose zones and quartz-carbonate veins. The main D2 deformation in the district resulted in the strong overprint of D1 refractory gold mineralization and was associated with the northwest-southeast flattening of the Giant deposit and progressive reverse-dextral shear of the Con deposit. Free-milling gold mineralization is associated with the D2 event, forming deeper in the Giant-Con system, creating a vertical zonation of free-milling quartz-carbonate veins overprinting earlier refractory gold mineralization that formed higher in the system. Ore plunge in the Giant deposit is controlled by the interaction of the original geometry of D1 deformation zones with the effects of D2 flattening. Ore plunge in the Con deposit is controlled by the orientation of F2 fold and B2 boudin axes in auriferous quartz-carbonate veins. D3 reactivation of the deformation zones (probably related to the end of the D2 compressive event) caused local reactivation of structures and is not associated with gold mineralization. D4 Proterozoic faulting offset and segmented the two deposits, including the major offset by the West Bay Fault. A new reconstruction of the West Bay Fault shows that the Con deformation zone is the down dip extension of the Giant deposit and not the Campbell deformation zone as previously thought.

The facies evolution of the Cretaceous/Tertiary sequence of NW Santander is considered in relation to the Cretaceous rifting and drifting, and Tertiary partial closure of the Bay of Biscay. Overlying the Palaeozoic basement are the fluvial Lower Triassic Buntersandstone and Upper Triassic Keuper evaporitic mudstone, deposited in a failed rift, extensional basin. Overlying Lower Jurassic carbonates are the syn-rift, continental elastics of the Vealden deposited in halfgrabens cut by transfer faults. The Vealden consists of two formations:- the lower, arenaceous-rich Barcena Mayor Fm. (braided stream environment) and the upper, argillaceous-rich Vega de Pas Fm. (meandering river). Overlying it is the Aptian Umbrera Fm. (calcarenite sheet), the Patrocinio Fm. (shoaling-up ward sandstone/marl alternation), the San Esteban Fm. (requienid/foraminiferal biomicrite of the internal platform) and the marls of the Rodezas Fm. The Upper Aptian Reocin Fm. is a requienid/foraminiferal biomicrite with thinned calcarenites deposited over active, diapiric palaeohighs. After initial marine and then equant calcite (meteoric phreatic) cementation, invasion of meteoric-derived groundwater over palaeohighs generated lenses of sucrosic dolomite in the Reocin Fm. Local mixing of further groundwater and Keuper-derived, sulphate-rich waters in karstic caverns precipitated sparry, baroque dolomite and Pb/Zn sulphides (by bacterial sulphate reduction). The clastic Lower Albian is a transgressive fluvial/estuarine/inner shelf sequence with tidal estuarine channels and sandwaves. The Middle/Upper Albian (syn-drift) has basal calcarenitic tidal sandwaves and is followed by storm/wave-reworked carbonates deposited on a homoclinal ramp. The clastic Lower Cenomanian is an estuarine/inner shelf deposit with tidal sandwaves and sandbars. The Middle/Upper Cenomanian is a storm/tide-dominated calcarenite. Outer shelf marls occur in the Turonian to Middle Campanian and the Upper Campanian to Middle Eocene is a sandy, foraminiferal inner shelf limestone. The Upper Eocene/Oligocene (syn-compression) is a carbonate slope-apron-reefal flysch deposit. It includes hemipelagic marl, neritic-derived calcarenitic turbidites and rudaceous mass flow deposits with highly polymict conglomerates. These were deposited coevally with Keuper piercement and thrust reactivation and date the Pyrenean compressional deformation here.

Thesis advisor: Yvette D. Kuiper / The Hudson Valley fold-thrust belt (HVB) is a narrow belt of deformed Upper Ordovician to Middle Devonian clastic and carbonate strata exposed in the western Hudson Valley of New York State. Geologic mapping at a scale of 1:10,000 was carried out near the town of Catskill. The southern portion of the map area includes a large doubly-plunging structure which features a fault-dominated southern portion plunging towards 017° and a northern fold-dominated, 206° trending, southerly plunging segment. A relay structure between two major faults or fault systems is interpreted as existing between the two domains. Farther north, the HVB narrows and folds plunge shallowly towards 212°, and then widens with folds plunging shallowly towards 017°. The changes can be explained by a localized increase in slip on the Austin Glen Detachment in the center of the map area, and subsequent loss of slip towards the north. / Thesis (BA) — Boston College, 2010. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: College Honors Program. / Discipline: Geology and Geophysics.