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Cretaceous continental extension was accommodated by the development of the Paparoa Metamorphic Core Complex, resulting in the separation of New Zealand from Gondwana. High grade (Lower Plate) and low grade (Upper Plate) rocks are separated by the Ohika and Pike Detachment Faults. The two detachment faults have distinctly different histories, with greater exhumation along the Pike Detachment Fault. The onset of crustal extension is proposed to have commenced along the Pike Detachment Fault at 116.2 ± 5.9 Ma (Rb/Sr dating). Both geochemical and geochronological approaches are adopted for this thesis, through the in situ analysis of oxygen and hafnium isotope ratios, trace metals and U-Pb content. Chemical changes are tracked during the petrogenesis of the Buckland Granite, with mafic replenishment observed in the later stages of crystallisation. Crystallisation temperatures of the Buckland Granite are calculated using zircon saturation thermometry, with an average Ti-in-zircon temperature of 697℃ (upper-amphibolite facies). Inherited zircons in Lower Plate rocks show distinct age peaks at c. 1000, 600 and 300 Ma, illustrating the incorporation of heterogeneous local crust (Greenland Group and Karamea Batholith). Model ages (TDM) are calculated for inherited zircons of the Lower Plate rocks, which record the time at which magma bodies (zircon host rocks) were extracted from the mantle. Maximum and minimum model ages for the Buckland Granite average at 3410 Ma and 2969 Ma, with the maximum TDM value of 3410 Ma coinciding with the proposed major crustal formation event of the Gondwana supercontinent at c. 3.4-3.5 Ga. Two distinct U-Pb zircon age peaks are observed in the Buckland Granite at 102.4 ± 0.7 and 110.3 ± 0.9 Ma. The 110.3 ± 0.9 Ma age is interpreted as the crystallisation age of the pluton, while the 102.4 ± 0.7 is proposed to represent a younger thermal (magmatic?) event associated with the 101-102 Ma Stitts Tuff.

No description available.

The analysis and modelling of magnetic anomalies at the conjugate rifted continental margins of the southern Iberia Abyssal Plain (TAP) and Newfoundland Basin have revealed that the sources of magnetic anomalies are distinctly different across both each margin and between the two margins. Analyses of synthetic anomalies and gridded sea surface magnetic anomaly charts west of Iberia and east of Newfoundland were accomplished by the methods of Euler deconvolution, forward and inverse modelling of the power spectrum, reduction-to-the-pole, and forward and inverse indirect methods. In addition, three near-bottom magnetometer profiles were analysed by the same methods in addition to the application of componental magnetometry. The results have revealed that oceanic crust, transitional basement and thinned continental crust are defined by magnetic sources with different characteristics. Over oceanic crust, magnetic sources are present as lava-flow-like bodies whose depths coincide with the top of acoustic basement seen on MCS profiles. Top-basement source depths are consistent with those determined in two other regions of oceanic crust. In the southern IAP, oceanic crust, ~4 km thick with magnetizations up to +1.5 A/m, generated by organized seafloor spreading was first accreted -126 Ma at the position of a N-S oriented segmented basement peridotite ridge. To the west, seafloor spreading anomalies can be modelled at spreading rates of 10 mm/yr or more. Immediately to the east, in a zone -10-20 km in width, I identify seafloor spreading anomahes which can only be modelled assuming variable spreading rates. In the OCT, sources of magnetic anomalies are present at the top of basement and up to -6 km beneath. I interpret the uppermost source as serpentinized peridotite, and the lowermost source as intruded gabbroic bodies which were impeded, whilst rising upwards, by the lower density serpentinized peridotites. Intrusion was accompanied by tectonism and a gradual change in conditions from rifting to seafloor spreading as the North Atlantic rift propagated northwards in Early Cretaceous times. Within thinned continental crust, sources are poorly lineated, and distributed in depth. Scaling relationships of susceptibility are consistent with the sources of magnetic anomalies within continental crust. OCT-type intrusions may be present in the mantle beneath continental crust. At the conjugate Newfoundland margin, seafloor spreading anomalies can be modelled at rates of 8 and 10 mm/yr suggesting an onset age consistent with that of the IAP. In the OCT there, I propose that magnetic anomalies are sourced in near top-basement serpentinized peridotites. An absence of magmatic material and the differences in basement character (with the IAP) suggest that conjugate margin evolution may have been asymmetric.

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This study consists of five chapters. Chapter 1 is a study of the motives and intent of Congress in creating a navy. Chapters 2 and 3 examine the operations conducted by the Marine Committee, Chapter 2 being devoted to its early operations and Chapter 3 to its later operations. Chapters 4 and 5 examine, in turn, the work of the Board of Admiralty and the Agency of Marine.

El reconocimiento de este tipo de borde de plataforma forma parte de los objetivos que se planteó el grupo multidisciplinario para realizar el estudio del Play Neógeno (Mioceno-Plio-Pleistoceno). El área de estudio comprende el sector sur-oriental costa afuera de la cuenca de Burgos hasta la batimetría de 500 m. Debido a que en el área Lamprea la sedimentación está afectada por deformación estructural causada por fallas lístricas de crecimiento, los bloques colgantes tienden a rotar formando depocentros locales hasta subcuencas intratalud. En este marco geológico regional ubicamos estos bordes de plataforma retrógrados en el play Plataforma de la secuencias Plioceno Inferior y Mioceno Superior. Genéticamente estos bordes retrógrados se forman debido a que las tasas de sedimentación y subsidencia en el Golfo de México son superadas por catastróficos colapsos instantáneos del margen de la plataforma asociadas a fallas lístricas regionales que reubica este borde hacia el continente detrás de la cicatriz de un deslizamiento. Oportunidades de entrampamiento son generadas por estos procesos, así se generan bloques de colapso que se ubican en la parte baja, luego el posterior relleno retrocedente en un dominio de talud superior y finalmente la progradación de clinoformas de facies marino someras de origen fluvio-deltaico. La posible fuente de sedimentos que podrían haber sido capturados por estos bordes retrógrados lo constituye un episodio volcánico formado a lo largo del eje Sierra de Tamaulipas – Alto de San Carlos. / -- The recognition of this type of Shelf Margin is part of the goals for the multidisciplinary group LAMPREA in the Regional study “Gulf of Mexico Neogene Play Evaluation” (Miocene-Plio-Pleistocen). The study area comprises the seismic volumes Lamprea-Chairel and Escolleras 1 respectively, which cover south-east block off shore Burgos basin until 500m. bathymetry. In Lamprea Area, sedimentation is affected by structural deformation caused by growing lístric faults, in which the hanging blocks exhibit rotation of sediments forming local sub-basins. In this geological framework, Retrograde Shelf Margin is developed, mainly in lower Pliocene and Upper Miocene stratigraphic sequence. Genetically Retrograde Shelf Margins occur due to the sedimentation and subsidence rate are overcome by instantaneous catastrophic collapse of shelf margins, associated with regional lístric fault. Later shelf margin is relocated landward behind collapse scour. Traps in this Play are generated by this process in which coarse sediments fill lower part and later shale and silts seal these sands, finally fluvio-deltaic shallow water clinoforms complete the sequence. Volcanic Arch located close to Sierra de Tamaulipas – San Carlos High could be source for sand prone deposits captured during Retrogradation of the shelf margin.

IT2018

Thesis advisor: John E. Ebel / The seismicity of the mid Atlantic Ridge (MAR) was compared in space and time with the seismicity along the Atlantic continental margins of Europe, Africa, North America, the Carribean and South America in a bid to appraise the level of influence of the ridge push force at the MAR on the Atlantic coastal seismicity. By analyzing the spatial and temporal patterns of many earthquakes (along with the patterns in their stress directions) in diverse places with similar tectonic settings, it is hoped that patterns that might be found indicate some of the average properties of the forces that are causing the earthquakes. The spatial analysis of the dataset set used shows that areas with higher seismic moment release along the north MAR spatially correlate with areas with relatively lower seismic moment release along the north Atlantic continental margins (ACM) and vice versa. This inverse spatial correlation observed between MAR seismicity and ACM seismicity might be due to the time (likely a long time) it takes stress changes from segments of the MAR currently experiencing high seismic activity to propagate to the associated passive margin areas presently experiencing relatively low seismic activity. Furthermore, the number of Atlantic basin and Atlantic coast earthquakes occurring away from the MAR is observed to be independent of the proximity of earthquake’s epicenters from the MAR axis. The effect of local stress as noted by Wysession et al. (1995) might have contributed to the independence of Atlantic basin and Atlantic coast earthquake proximity from the MAR. The Latchman (2011) observation of strong earthquakes on a specific section of the MAR being followed by earthquakes on Trinidad and Tobago was tested on other areas of the MAR and ACM. It was found that that the temporal delay observed by Latchman does not exist for the seismicity along other areas along the MAR and ACM. Within the time window used for this study, it appears that seismicity is occurring randomly in space away from the MAR. The weak anticorrelations between ACM and MAR seismicity show that the ridge push force probably has some level of influence on the ACM seismicity. However, as revealed from previous research on the study area, the forces resulting from lateral density contrasts related to topographic features and lateral density variations between oceanic and continental crust also appear to significantly influence the seismicity of the Atlantic coastal margins. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Describes a theory of gaming inspired primarily by Jean Baudrillard’s claim that gaming is characterized by a “passion for rules.” Key elements of the theory include that games are an attempt to create a new reality, that games create a space for individuality even in an otherwise homogenized world, and that pain and happiness are not diametrically opposed concepts to the gamer. The theory also emphasizes the importance of the player’s meeting with the “superplayer,” the player’s own constructed ideal that he tries to imitate within the game world. This theory of gaming is then applied to the 14th century British poem, Sir Gawain and the Green Knight both as a demonstration of the theory and to offer a new perspective on the poem. Gawain’s character in the poem is argued as being the archetype of the modern gamer, escaping from an oppressive hegemony by daring to follow the superplayer’s seduction into the passionate world of gaming.