This study presents the interpretation of Edo-Western and Sparker seismic geophysical data acquired on the northern KwaZulu-Natal upper continental margin by various organisations since 1981. Five seismic sequences are recognised and these are traceable across the entire length of the study area. The oldest is interpreted as a late Cretaceous marine sequence (Sequence A), probably the offshore equivalent of the St. Lucia Formation exposed onshore. This sequence is overlain by a progradational, probable late Tertiary shelf sequence (Sequence B) onlapping in places against the underlying marine sequence. The outer portion of this sequence on the upper continental slope is characterised by complicated reflection termination patterns indicating the possible presence of discreet sequences within this shelf and slope unit. These shelf and slope sediments are overlain by a thin (less than 20m) reworked and eroded Pleistocene shelf unit (Sequence C), itself overlain by linear Pleistocene aeolianites (Sequence D) in places. The youngest sequence observed is the Holocene unconsolidated sediment wedge (Sequence E) on the inner shelf, attaining thicknesses of greater than 20m in places. The various sequences were mapped out and sediment isopach maps were produced (wherever possible) as well as an overall geological subcrop map of the study area. 150 kilometres of shallow penetration Edo Western seismic records acquired off the Sodwana Bay continental shelf were interpreted. Two sediment types are recognised, namely consolidated beach rock/aeolianite and unconsolidated Quaternary shelf sand/bioclastic reef derived sediment. In places, accumulations of bioclastic sediment in subaqueous dune troughs which have been subsequently buried by migrating bedforms manifest themselves on seismic records as dark semi-continuous reflectors beneath the migrating bedform. Close inshore, seismic records show prominent reflectors interpreted as consolidated sediment beneath varying thicknesses of unconsolidated sediment. Close to the shelf break (occurring at approximately -60m), seismic interpretation indicates that thin beach rock developments perch directly upon unconsolidated shelf sand, with the beach rock having been eroded through in places to expose unconsolidated sediment beneath. A sediment thickness map for this area was compiled from the seismic data. The limited penetration of the Pinger system necessitated "greater-than" values being used in many areas. Greatest sediment thicknesses occur in subaqueous dune fields where unconsolidated sediment thickness is at least 11 m. In inshore areas absent of subaqueous dune fields, sediment thicknesses are typically low, varying between 1 and 3m. A prominent submerged dune ridge close inshore limits substantial unconsolidated sediment build-up to landward of this feature. On the seaward side substantial build-up is limited by the action of the Agulhas Current which is actively transporting sediment into the head of submarine canyons which incise the continental shelf at Sodwana Bay. This study shows that on the northern KwaZulu-Natal continental shelf where there is a dearth of unconsolidated Quaternary sediment, the Edo Western seismic system is a useful tool for discerning thin veneers of unconsolidated sediment less than 4m thick. When considering the overall low volumes of unconsolidated sediment present on the shelf, this hitherto unconsidered volume of sediment constitutes an important part of the shelf sediment budget. Submarine landslide features observed on sparker seismic records are described and discussed. Submarine landslides are present which affect a) Sequences A and B, b) Sequence B only and c) Sequence A only, ages of these sediment failures can thus be inferred as being either post- Late Cretaceous or post- Late Tertiary. Offshore Kosi Bay, submarine landslide features affecting Sequence A are buried by unaffected Sequence B sediments, indicating a post- Late Cretaceous to pre- Late Tertiary age of occurrence. Style of failure tends towards mass flow in those submarine landslides in which Sequence B only sediments are affected, while those in which Sequence A is affected exhibit some slide features indicating a greater degree of internal coherency of these sediments compared to Sequence B. Slope stability analysis of a submarine landslide feature offshore St. Lucia Estuary Mouth indicates the failed sediment mass would have been stable under static conditions and that external dynamic forces such as storm waves or seismic activity would have been necessary to induce failure. It is demonstrated that the Zululand earthquake of 1932 would have exceeded the intensity necessary to induce sediment failure and this event should therefore be considered as a possible cause. Seismic evidence of fluvial incision/subaerial exposure at the boundaries between Sequences A and B and C and E are further evidence of lowered sea-levels probably during the Oligocene and Late Pleistocene. The position of the incision into Sequence C relative the present course of the Mkuze River indicates the possibility that this incision could represent the palaeo-outlet of this river. Seismic expression of 3 submarine canyons in the study area indicate that they are currently undergoing active headward erosion, independent of any direct modern fluvial influence. In the case of Ntabende Canyon, a nearby continental shelf incision postulated to be the palaeo-Mkuze outlet indicates that provision of terrigenous material to this portion of the continental shelf could well have accelerated mass wasting processes within the canyon itself. This submarine canyon could therefore have progressed more rapidly to a relatively mature phase of development. Subsurface structure indicates the lack of any post- Late Tertiary fault features beneath the canyons, thus excluding faults active in post- Late Tertiary times as a developmental factor. It is shown that the overall, external morphology of the KwaZulu-Natal upper continental margin is strongly influenced by seismic stratigraphic relationships, with the main influencing factors being outcrop position of the various sequences and depositional angle of sediments of which a sequence is comprised. External morphology has also been greatly modified in places by mass-wasting processes. It is demonstrated also that relating the observed seismic stratigraphy to onshore geological cross sections is problematic due to the distances involved and lack of confident offshore dates for the seismic sequences observed. Seismic relationships observed contribute to an understanding of relative sea-level movements since the Late Cretaceous and the overall geological evolution of the northern KwaZulu-Natal upper continental margin, details of which are discussed. / Thesis (M.Sc.)-University of Natal, Durban, 1998.

A quasi-two dimensional model for the southern Vancouver Island shelf was developed with the Regional Ocean Modelling System (ROMS) to study coupling of the carbon, oxygen, and nitrogen cycles in a summer wind-driven upwelling region. The physical model is coupled to an ecosystem module that includes a simple representation of a sediment layer and considers non-fixed C:N ratios for detritus and dissolved organic matter (i.e., explicitly modelled pools of carbon and nitrogen for those variables). The model accounts for denitrification within the sediments as well as within the water column when oxygen concentrations are low (below 5 mmol-O2 m-3). The objective is to identify the dominant processes controlling the cycles, their coupling, and their sensitivity to changes in environmental forcing. Results demonstrate how low oxygen and low pH events are tightly coupled in the coastal study region, especially through local ecosystem processes. In particular, exchange with the sediments plays a dominant role in consuming oxygen from and releasing inorganic carbon to the bottom waters on the shelf. Two key features distinguish the southern Vancouver Island shelf from other coastal regions in the California Current System and protect inner shelf waters from severe hypoxia and corrosive (i.e., undersaturated in aragonite) conditions. First, the greater width of the shelf reduces the penetration of subsurface offshore high-carbon and low-oxygen waters into shallower waters; and second, the relatively fresh Vancouver Island Coastal Current (VICC) brings oxygen-rich and carbon-poor waters to the bottom layer over the inner shelf. Sensitivity experiments show that carbon and oxygen cycles on the southern Vancouver Island shelf may be significantly affected by an altered upwelling season, a shallower offshore Oxygen Minimum Zone, a warmer ocean, and a carbon-enriched environment. Combinations of these scenarios suggest a potential increasing risk for the development of coastal hypoxia and corrosive conditions in the future. Further sensitivity simulations indicate that sedimentary denitrification provides an additional coupling between the carbon, oxygen, and nitrogen cycles. Total alkalinity generated by sediment denitrification has the potential to buffer anthropogenic ocean acidification. However, this alkalinity effect over the Vancouver Island shelf in late spring and summer simulations is small compared with studies for other locations at annual scales. Longer time scales need to be examined in this region to confirm whether the role of alkalinity generation in the sediments is significant. In conclusion, this dissertation not only demonstrates the coupled nature of biogeochemical cycles in the coastal ocean, but also the importance of this coupling as we try to estimate how coastal ecosystems will respond to human modifications of shelf waters and the climate.

Temporal changes of seismic velocity and anisotropy in the shallow crust are quantified using local earthquakes recorded at a 200-m-deep borehole station CHY in Taiwan. This station is located directly above the hypocenter of the 10/22/1999, M6.4 Chia-Yi earthquake. Three-component seismograms recorded at this station show clear direct (up-going) and surface-reflected (down-going) P- and S-waves, and S-wave splitting signals. The two-way travel times in the top 200 m is obtained by measuring the time delays between the up-going and down-going waves in the auto-correlation function. The S-wave travel times measured in two horizontal components increase by ~1-2% at the time of Chia-Yi main shock, and followed by a logarithmic recovery, while the temporal changes of S-wave splitting and P-wave are less than 1% and are not statistically significant. We obtain similar results by grouping earthquakes into clusters according to their locations and waveform similarities. This suggests that the observed temporal changes are not very sensitive to the seismic ray path below CHY, but are mostly controlled by the variation of material property in the top 200 m of the crust. We propose that strong ground motions of the Chia-Yi main shock cause transient openings of fluid-filled microcracks and increases the porosity in the near-surface layers, followed by a relatively long healing process. Because we observe no clear changes in the shear wave anisotropy, we infer that the co-seismic damages do not have a preferred orientation. Our results also show a gradual increase of time delays for both the fast and slow S-waves in the previous 7 years before the Chia-Yi main shock. Such changes might be caused by variations of water table, sediment packing or other surficial processes.

Marine nitrogen (N) is an essential nutrient for all oceanic organisms. The cycling of N between biologically available and unavailable forms occurs through numerous reactions. Because of the vast number of reactions and chemical species involved, the N cycle is still not well understood. This dissertation focuses on understanding some of the reactions involved in the cycling of marine N, as well as improving techniques used to measure dissolved N2 gas. The largest loss term for global marine N is a reaction called denitrification. In this work, denitrification was measured in the sandy sediments of the Georgia continental shelf, an area where this reaction was thought to be unlikely because of the physical properties of the sediments. Nitrogen fixation, which is a reaction that produces biologically available N, was detected in Georgia estuarine sediments. N fixation was measured concurrently with denitrification in these sediments, resulting in a much smaller net loss of marine N than previously thought. Lastly, membrane inlet mass spectrometry (MIMS) is a technique that measures dissolved N2, the end product of denitrification and a reactant in N fixation reactions. This study suggests that N2 measurements by MIMS are influenced by O2 concentrations due to pressure differences inside of the ion source of the mass spectrometer. These findings seek to improve denitrification measurements using MIMS on samples with varying O2 concentrations. In conclusion, this dissertation suggests that the marine N cycle is more dynamic than has been suggested, due to the recognition of input and loss reactions in a wider range of marine and estuarine environments. However, improvements in the understanding of MIMS will help with direct measurements with reactions involved in the global marine N cycle.

Tide-topography coupling is important for understanding surface-tide energy loss, the intermittency of internal tides, and the cascade of internal-tide energy from large to small scales. Although tide-topography coupling has been observed and modeled for 50 years, the identification of surface and internal tides over arbitrary topography has not been standardized. Here, we begin by examining five surface/internal-tide decompositions and find that only one is (i) consistent with the normal-mode description of tides over a flat bottom, (ii) produces a physically meaningful depth-structure of internal-tide energy flux, and (iii) results in an established expression for internal-tide generation. Next, we examine the expression for internal-tide generation and identify how it is influenced by remotely-generated shoaling internal tides. We show that internal-tide generation is subject to both resonance and intermittency, and can not always be predicted from isolated regional models. Lastly, we quantify internal-tide generation and scattering on the Oregon Continental slope. First, we derive a previously unpublished expression for inter-modal energy conversion. Then we evaluate it using observations and numerical simulations. We find that the surface tide generates internal tides, which propagate offshore; while at the same time, low-mode internal tides shoal on the slope, scatter, and drive turbulent mixing. These results suggest that internal tides are unlikely to survive reflection from continental slopes, and that continental margins play an important role in deep-ocean tidal-energy dissipation. / Graduation date: 2011

Meiner nichtreduktionistischen Lesart Gadamers, derzufolge eine wechselseitige konstitutive Relation zwischen „Sprache“ und „Erfahrung“ besteht, ist es gestattet, den Vorwurf, die Sprachphilosophie Gadamers führe in den Relativismus, den man häufig gegenüber sprachphilosophischen Positionen erhebt, abzuweisen. Manchen Denkern zufolge haben die Philosophen der Postmoderne, zu denen auch Gadamer gezählt wurde, eine einfache Umkehrung der beiden Pole des modernen Verhältnisses „Sprache“ – „Erfahrung“ vollzogen: Während die Sprache in der Moderne in ihrer Bedingtheit zur Erfahrung und als bloßes Ausdrucksmittel verstanden wurde, wurde dieses Verhältnis in der neueren Philosophie nur umgekehrt, insofern die Philosophie in der Sprache das Fundament für die Erfahrung sehe, wonach die Erfahrung als ein Ausdruck der Sprache erscheine. Die vorliegende Arbeit setzt sich mit diesem Relativismusvorwurf auseinander und beabsichtigt, eine wechselseitige Abhängigkeit zwischen Sprache und Erfahrung ausgehend von Hans-Georg Gadamers Werk zu entwickeln. Um das zu erreichen, wurden zunächst eine doppelte negative-positive Erfahrungsstruktur und dann einige phänomenologische und transzendentale Merkmale der Erfahrung auf dem historischen Hintergrund für Gadamers Erfahrungsbegriff herausgearbeitet. Somit machte sich die konstitutive Sprachlichkeit der Erfahrung erkennbar. In einer Auseinandersetzung mit dem Sprachbegriff auf der anderen Seite wurde sein dialogischer und welterschließender Charakter veranschaulicht, so dass auch seine Angewiesenheit auf die Welterfahrung offenkundig wurde. / This work deals with a particular relativistic objection on Gadamer’s hermeneutic philosophy of language, according to which the position of language has such a prior status so that human experience is solely dependent on the language people speak. That is a reductionist approach to Gadamer’s hermeneutic, which ascribes language an exclusively explanatory and foundational status. I am taking this objection to a close examination and develop a double argumentation line: On the one side I show how the concept of world experience is language determined, and on the other side how the language itself is determined by our experience of the world. In order to argue for this interdependence, I first examined the positive and negative structure of experience, some phenomenological and transcendental features and offered a short historical background of ties to selected philosophical heritage. In the second part of the work I developed a concept of language that argues for its dialogical and not absolutely transsubjective character, also for its world-disclosing alongside its communicative and representational dimension. Gadamer’s hermeneutic philosophy of language, belonging to the continental philosophy or HHH Theories represents an antireductionist approach to language after the linguistic turn, which is often criticized for a linguistic reductionism and relativism.

The ‘giant’ Tambogrande volcanogenic massive sulphide (VMS) deposits within the Cretaceous Lancones basin of northwestern Perú are some of the largest Cu-Zn-Au-Ag-bearing massive sulphide deposits known. Limited research has been done on these deposits, hence the ore forming setting in which they developed and the key criteria that permitted such anomalous accumulation of base-metal sulphides are not understood. Based on field relationships in the host volcanic rocks and U-Pb geochronology, the deposits formed during the early stages of arc development in the latest Early Cretaceous and were related to an extensional and arc-rift phase (~105-100 Ma, phase 1). During this time, bimodal, primitive basalt-dominant volcanic rocks were erupted in a relatively deep marginal basin. Phase 1 rhyolite is tholeiitic, M-type, and considered to have formed from relatively high temperature, small batch magmas. The high heat flow and extensional setting extant during the initial stages of arc development were essential components for forming a VMS hydrothermal system. The subsequent phase 2 (~99-91 Ma) volcanic sequence comprises more evolved mafic rocks and similar, but more depleted, felsic rocks erupted in a relatively shallow marine setting. Phase 2 is interpreted to represent late-stage arc volcanism during a waning extensional regime and marked the transition to contractional tectonism. The Tambogrande deposits are particularly unusual amongst the ‘giant’ class of VMS deposits in that deposition largely occurred as seafloor mound-type and not by replacement of existing strata. Paleomorphology of the local depositional setting was defined by seafloor depressions controlled by syn-volcanic faults and rhyolitic volcanism. The depressions were the main controls on distribution and geometry of the deposits and, due to inherently confined hydrothermal venting, enhanced the efficiency of sulphide deposition. Geochemical and radiogenic isotope data indicate that the rhyolites in the VMS deposits were high temperature partial melts of the juvenile arc crust that had inherited the isotopic signatures of continental crust. Moreover, Pb isotope data suggest the metal budget was sourced almost wholly from mafic volcanic strata. Therefore, unlike the implications of many conventional models, the felsic volcanic rocks at Tambogrande are interpreted to have only played a passive role in VMS formation.

In the Pilgangoora Belt of the Pilbara Craton, Australia, the 3517 Ma Coonterunah Group and 3484-3468 Ma Carlindi granitoids underlie the 3458 Ma Warrawoona Group beneath an erosional unconformity, thus providing evidence for ancient emergent continental crust. The basalts either side of the unconformity are remarkably similar, with N-MORB-normalised enrichment factors for LILE, Th, U and LREE greater than those for Ta, Nb, P, Zr, Ti, Y and M-HREE, and initial e(Nd, Hf) compositions which systematically vary with Sm/Nd, Nb/U and Nb/La ratios. Geological and geochemical evidence shows that the Warrawoona Group was erupted onto continental basement, and that these basalts assimilated small amounts of Carlindi granitoid. As the Coonterunah basalts have similar compositions, they probably formed likewise, although they were deposited >60 myr before. Indeed, such a model may be applicable to most other early Pilbara greenstone successions, and so an older continental basement was probably critical for early Pilbara evolution. The geochemical, geological and geophysical characteristics of the Pilbara greenstone successions can be best explained as flood basalt successions deposited onto thin, submerged continental basement. This magmatism was induced by thermal upwelling in the mantle, although the basalts themselves do not have compositions which reflect derivation from an anomalously hot mantle. The Carlindi granitoids probably formed by fusion of young garnet-hornblende-rich sialic crust induced by basaltic volcanism. Early Archaean rocks have Nd-Hf isotope compositions which indicate that the young mantle had differentiated into distinct isotopic domains before 4.0 Ga. Such ancient depletion was associated with an increase of mantle Nb/U ratios to modern values, and hence this event probably reflects the extraction of an amount of continental crust equivalent to its modern mass from the primitive mantle before 3.5 Ga. Thus, a steady-state model of crustal growth is favoured whereby post ~4.0 Ga continental additions have been balanced by recycling back into the mantle, with no net global flux of continental crust at modern subduction zones. It is also proposed that the decoupling of initial e(Nd) and e(Hf) from its typical covariant behaviour was related to the formation of continental crust, perhaps by widespread formation of TTG magmas.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from first page of PDF file (viewed June 23, 2008). Includes bibliographical references (p. 51-59).

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from first page of PDF file (viewed June 23, 2008). Includes bibliographical references.