A minor eruption of Mount Saint Helens in Washington State U. S. A. in 1984, triggered the formation of a debris flow in the headwaters of the North Fork Toutle River. As the debris flow progressed downstream it transformed through the incorporation of water and the loss of sediment and within 34 kilometres became a muddy flood. The deposits produced by the transforming flow and associated recessional flows that followed in its wake, exhibited a coarse grained depositional continuum from debris flow to stream flow, including deposits with intermediate sedimentological characteristics termed "hyperconcentrated flow deposits".The systematic and detailed sedimentological analysis of these deposits, combined with information concerning the characteristics of the flow, has allowed the delineation of hyperconcentrated flow deposits within the debris flow/stream flow depositional continuum and hence the establishment of criteria for the recognition of coarse grained hyperconcentrated flow deposits in the volcaniclastic environment of Mount Saint Helens. Hyperconcentrated flow deposits are generally homogeneous, matrix-supported, unstratified (except where defined by sub units), have sorting characteristics intermediate between debris flow and stream flow and can exhibit a bimodal, generally non imbricate, clast fabric as a function of clast size. Coarse-tail inverse grading may occur but it is weak, or restricted to sub units. Use of these criteria enabled the recognition of hyperconcentrated flow deposits within depositional sequences produced earlier in the eruptive history of Mount Saint Helens.The analysis of Permo-Triassic alluvial fan deposits on the Isle of Lewis Scotland, revealed that elements of the debris flow/stream flow depositional continuum could be recognised by the application of the criteria established in the volcaniclastic environment of Mount Saint Helens.

No description available.

The Eocene Nummulitique (Lutetian to Priabonian) has been studied in the external chains of the French Alps in Haute Savoie and Haute Provence. The Nummulitique unconformably overlies the Mesozoic passive margin succession and represents the onset of sedimentation in the Alpine Foreland Basin which formed due to lithospheric flexure caused by the advance of the Alpine orogeny. The base of the formation is marked by a regional erosional unconformity that developed during subaerial exposure of the Alpine foreland. The Nummulitique may be divided into two informal members: the lower Infranummulitique, a succession of terrigenous carbonates, and the overlying Nummulitic Limestone, a shallow marine carbonate ramp succession. The Infranummulitique is composed of terrigenous carbonates thought to have been derived from the uplifted and eroding foreland which were redeposited in local depocentres due to the topography on the erosion surface. The Infranummulitique can be divided into four facies associations: i) a lenticular conglomerate/nodular marl deposited from ephemeral streams, ii) a sheet conglomerate deposited in a marginal marine fan delta, iii) a Cerithium marl deposited in a brackish water coastal plain/lagoon and iv) a Microcodium wackestone deposited from coastal marine channels. The Nummulitic Limestone is marked by the appearance of the first fully marine foraminifera and a change from terrigenous to autochthonous carbonate sedimentation on a low-energy ramp dominated by larger benthonic foraminifera. The inner-ramp is represented by the deposition of bioclast shoals (packstones and grainstones) dominated by either calcareous red algae, Nummulites or peloids. The middle-ramp is dominated by mud-rich wackestones with a fauna of flat foraminifera, with local winnowed accumulations attributable to storm reworking. The outer ramp and basin are represented by mudstones and marls with a sparse benthos. The Nummulitique shows a marked cyclicity within an overall deepening upwards succession which is interpreted to be the combined effects of tectonic basin subsidence and high-frequency (4th order) eustatic sea-level variations. As the basin developed, the eustatic signature producing the small-scale cyclicity was successively overprinted by accelerating basin subsidence which controlled the stratigraphy of the underfilled foreland basin. Initially, the carbonate productivity is able to keep pace with the relative sea-level changes and the ramp prograded into the basin. The combination of accelerating subsidence rates and nutrient and detrital influx from the approaching orogenic wedge reduced the carbonate productivity and the ramp drowned, leading to pelagic marl deposition. The drowning surface and small-scale cyclicity have been used to correlate between measured sections within each field area, but problems occur in correlating between areas due to the migration of the foreland basin producing a diachronous sedimentary succession, which shows a similar development around the Alps, regardless of the age of the sediments. This diachroneity is evident in the two study areas with similar sediments, cycles and key surfaces developed at different stages of the basin development. The similarity in the successions demonstrates that the early sedimentation in the French Alpine Foreland Basin was controlled primarily by flexural subsidence.

The Australian-Pacific plate boundary is an uncomplicated structure along most of its length in the South Island, New Zealand. In South Westland, south of the Arawata River, however, several terranes converge onto the Alpine fault. Inherent anisotropies arising from the position of pre-existing fault structures, lithological contacts and rheological heterogeneities within these give rise to an atypically diffuse and complex zone, the overall geometry of which resembles a regional scale transpressive flower structure. The flower structure is a broad deformation zone 60 km in length extending approximately 7 km from the Alpine fault to its eastern limit, the Dun Mountain Ophiolite Belt. Integral parts of the structure are the Hollyford Fault System and the Livingstone Fault System. The area is characterised by an array of left-stepping, subparallel faults with an average 060� strike linked by 020� striking structures. All fault traces offset Quaternary features. Fractions of the total interplate slip are partitioned across the reactivated structures. Additionally, kinematic indicators reveal partitioning of strike-slip and oblique/dip-slip deformation across the related secondary fault zones. The behaviour of the plate boundary zone in South Westland is fundamentally controlled by reactivation of the Hollyford Fault System and the Livingstone Fault System which partition slip away from the Alpine fault. As a consequence, the eastward transferral of slip onto the curved geometry of the converging fault systems has ultimately created a left-stepping contractional regime, the equivalent of a restraining bend in the plate boundary zone. The competent Dun Mountain Ophiolite Belt controls the geometry and evolution of the reactivated structures. It also acts as an indenter and imposes additional boundary conditions adding to the shortening component in the region and the onset of complex transpressional strain patterns. The geometry and kinematics of the flower structure in the upper crust is mimicked in the ductile mid to lower crust. Upper greenschist facies mylonites reveal a complex fold pattern developed in response to contemporaneous non-coaxial and coaxial deformation. The folding formed during a continuation of deformation associated with mylonitisation at depths within the fault system. The fact that strain localisation and transpressive strain patterns in the brittle crust continue into the ductile zones suggests there is a feedback relationship between the two regimes. The reactivation of pre-existing structures and the influence of rheological factors are considered as first order factors controlling strain partitioning in the plate boundary zone. Recognition of local strain partitioning is important for assessing slip rates and earthquake recurrence. Similarly, the faults extend down below the seismogenic zone so that interaction of the different structures with each other may produce changes in fault behaviour which affects earthquake nucleation. Although the Alpine fault is a major structure in the South Island of New Zealand with over 400 km of dextral movement, the reactivated structures still exert a degree of control locally on the structure and kinematics of the plate boundary zone. Reactivation of inherent fault structures has important implications for the initiation of plate boundary faults and the alteration of the plate boundary geometry with evolving deformation.

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.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 121-130) Also available in print.

Thesis (M.S.)--University of North Carolina at Wilmington, 2004. / Includes bibliographical references (leaves : 70-72).

Thesis (Ph. D.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 254-293).

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 119-131). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 250-263). Available also in a digital version from Dissertation Abstracts.