The Sundarbans is one of the largest coastal wetland sites in the world that covers an area of approximately one million hectares in the delta of the Ganges and Brahmaputra (G-B) rivers located across Bangladesh and India. This thesis sets out to examine sedimentation taking place in the western, 'abandoned' tidal delta over the course of the mid-to-late-Holocene epoch, c. last 4000 cal yr BP. This will focus on investigating the dominant sources and depositional processes through grain-size distributions, mineralogy, and high-resolution core-scan derived geochemistry of sediments for provenance and depositional process indicators. By approximately 5000 cal yr BP, the Ganges River had largely abandoned the western delta complex underlying the present day Indian Sundarbans and migrated eastward towards its present day course. The western extent of the old G-B delta is now considered to be undergoing net erosion, at least since the middle ofthe 19th century. This thesis seeks to test and challenge these assumptions. The results from this thesis suggest that sedimentary provenance is dominated by a mixed Ganges-Brahmaputra source, composed mainly of silicate weathering products, with the possibility of greater Ganges inputs. The depositional environment is characterised by a sedimentary facies record similar to that of a muddy-tidal flat with a dominant fining-up of the grain size distributions, capping what may potential sub-tidal ridges. Radiocarbon results reveal an overarching trend in stratigraphically anachronous dates that are potentially indicative of fluctuating depositional processes present throughout the Sundarbans. Sedimentation processes in the Sundarbans appear to reflect the ebband flood-tidal conditions which may be overprinted by monsoonal variability. A novel development in the methodological approaches pursued in this research has been through the compositional data analysis (CoDa) framework. The Sundarbans may be considered to be a dynamic sedimentary depositional environment that is under constant flux.

No description available.

No description available.

The Argolis Peninsula of SE Greece lies within the Alpine orogenic belt, which formed as a result of continental collision, following the closure of a Mesozoic-Tertiary Neotethys oceanic basin. The area is located at the southern end of the Pelagonian Zone, a microcontinental block, which rifted from the northern margin of Gondwana in Middle Triassic times. Anisian-Ladinian rifting was marked in the Argolis Peninsula by the formation of deep-water basins floored by volcanics within a carbonate platform. These basins took the form of two, large, asymmetric half-grabens of opposing polarity. Late Triassic-Early Jurassic times were characterised by gentle subsidence of the platform, unbroken sedimentation and the partial transgression of the deep-water basins by neritic caronates along their unfaulted margins. The nature of sedimentation changed abruptly in Toarcian (Early Jurassic) times, with a switch to nodular, hemipelagic, Ammonitico Rosso limestone, interpreted to be a regional collapse of the platform. Continued subsidence depressed the platform below the carbonate compensation depth (CCD), resulting in the accumulation of radiolarian cherts in Middle-Upper Jurassic (Bathonian-Kimmeridgian) times. A hiatus in sedimentation after obduction was succeeded by a diachronous transgression, which began in the Upper Jurassic (Tithonian) and continued into the Upper Cretaceous. No active subsidence of the platform is recorded until Upper Cretaceous (Turonian) times when rapid deepening of the carbonate facies and intra-platform faulting occurred. Pink pelagic limestones deposited during this episode pass up rapidly into terrigenous flysch of Palaeocene-Eocene age. Early Tertiary thrusting towards the northwest in W Argolis and towards the north in E Argolis, with localised backthrusting towards the south is interpreted to be the result of collision of the Pelagonian, Apulian and Serbo-Macedonian microcontinents. Evidence for a S. Greek Neotethys as late as Upper Cretaceous time is provided by the presence of oceanic basalts and pelagic limestone cover, imbricated within a subduction/accretion complex (Ermioni Complex). In addition, the lowermost thrust sheets within the complex preserve a complete continental margin sequence to the Pelargonian continent during the Cretaceous. These rocks record the collapse of the continental margin during the southeast to northwest emplacement of the Ermioni Complex. By the Quaternary, the area has been affected by a phase of north-south extensional faulting and associated volcanism at Methana, related to post-Miocene subduction around the Aegean arc. This has produced a major east-west trending graben in central Argolis which is linked to a larger graben system in the Saronic Gulf to the north. The area is now tectonically inactive due to a shallowing of the Aegean Benioff Zone and a corresponding northerly migration of the volcanic arc, triggered by the arrival at the trench of thinned African continental crust.

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The aims of this study were to determine the temporal relationships, using K-Ar dating, of the complex magmatic events which occurred in Scotland between the early Carboniferous and early Permian. Various aspects of Scottish Carboniferous geology are reviewed. The least altered whole-rock basalt samples have given reliable ages. Green alteration minerals in the basalts are liable to lose argon; they contain much of the sample atmospheric argon. Ten magmatic episodes have been recognised. The Carboniferous basic magmas became increasingly silica-undersaturatad with time and similar short term trends occurred within each episode. It is suggested that the magmatic cycle is the result of the growth, maturity and slow decline of a single mantle thermal event. The tectonic setting of Carboniferous magmatism in Scotland is examined in relation to the Hercynian orogeny; it is argued that it is analogous to the Cenozoic alkaline magmatism in East Asia, developed well to the rear of the Western Pacific island arcs.

No description available.

The Oligo-Miocene Sardinian Rift is an intra-arc basin which formed in response to multiphase extension and transtension on several orientations of normal and strike-slip faults. Rifting occurred during and after the separation and rotation of the Corsica-Sardinia microplate from Eurasia, coeval with northwestward dipping subduction of Neotethyan oceanic crust beneath the islands. The Sardinian rift comprises many semi-independent sub-basins which are filled with complex arrangements of non-marine and marine, siliciclastic, carbonate and marlstone sediments plus subduction-derived extrusive and pyroclastic volcanic rocks. Exposures in the Sardinian Rift provide a rare opportunity to study the evolution of, and processes active within intra-arc and back-arc basins. Field observations from along the Oligo-Miocene Sardinian Rift are presented and placed within a new chronostratigraphic framework. A tectono-stratigraphic synthesis of the Sardinian Rift has implications for the Oligo-Miocene tectonic development of the Western Mediterranean and for extensional settings in general. Geochemical analysis of volcanic-arc rocks provides clues as to what happens at depth when continental arc magmatism and extension are combined. Rifting commenced in the mid-late Oligocene, coeval with the eruption of the first volcanic-arc rocks, whilst the Sardinia-Corsica microplate was attached to Eurasia. The resultant proto-Sardinian rift formed with considerable along-strike variability. It consisted of a N-S segment in northern Sardinia which was cross-cut by NE-SW trending, elongate transtensional sub-basins. In southern Sardinia, the main rift segment was oriented NW-SE with separate E-W trending grabens dissecting the southernmost pre-rift basement. Geometries within continental clastic sediments shed from local topographic highs and basinward lacustrine limestones suggest that the first phase of extension was short-lived (<few Ma) and that tectonic subsidence far exceeded sedimentation rates. Strike-slip faults crossing the eastern Sardinian basement on inherited late Hercynian trends may have moved before and during the first mid-late Oligocene rifting phase. These strike-slip faults are thought to have facilitated the tectonic escape of continental crust from the Northern Apennines compressional zone towards the extending areas of western Sardinia and the southern Eurasian plate.

The movement of cohesive sediment is of great importance in many coastal and estuarine engineering problems. Navigation channels often used to be dredged to maintain navigable depths, allowing for the effect of a harbour or wharf on the local sediment transport regime. Contaminants are readily absorbed by silt and clay particles, causing a range of water quality problems. This thesis describes the development and testing of a finite element program to model cohesive sediment transport. The program solves the coupled Navier-Stokes and scalar-transport equations along with several complex numerical algorithms for settling velocity, flocculation, non-Newtonian flow and turbulence. The program also uses <i>h</i>-adaptivity and unstructured mesh generation to capture important flow features. The program is benchmarked against the thermally driven cavity problem, producing results that compare well with existing solutions without any special scheme for advection dominated flow. This is possible by modelling the transient problem using <i>h</i>-adaptivity. The programme is also applied to realistic cohesive sediment transport problems. It predicts the formation of a hindered settling layer and uses <i>h</i>-adaptivity to capture sharp density interfaces. It also solves settling of dredged material onto a inclined bed and non-Newtonian flow in a race-track flume. The program produces results that compare well with experimental data. The <i>h</i>-adaptive finite element method is found to be a very successful in modelling the transport of cohesive sediment and its associated physical processes.

The Himalayan mountain chain formed between 65-40 Ma due to the closure of the Tethyan ocean and the subsequent collision of the Indian and Eurasian plates. This collision and continued plate convergence resulted in crustal thickening, southerly propagating thrust stacking, and two main periods of Barrovian metamorphism: an early 'Eo-Himalayan' metamorphism and a later Himalayan metamorphism, synchronous with a major period of thrust stacking at ca. 21 Ma. Formation of the orogen loaded the Indian plate and caused downwarping and development of a foreland basin to the south. The sedimentary rocks within the foreland basin are the Subathu Formation of Palaeocene-Mid Eocene age, the Dagshai Formation of Upper Eocene-Oligocene age, and the Kasauli Formation of lowest Miocene age. These sediments form a conformable statigraphic sequence. The Subathu Formation sediments are marine deposits, consisting of dominantly mudstones in the lower part of the succession, with limestone becoming more prominent higher up. Terrigenous material is present in minor amounts. The Dagshai Formation sediments are clastic red beds, with mudstones dominating at the base of the sequence and sandstones increasing in proportion higher up the succession. They are interpreted as being of continental origin, laid down under semi-arid conditions in a distal alluvial fan and meandering fluvial setting. The Kasuali Formation sediments are dominantly grey sandstones. Like the Dagshai Formation, they are of continental origin, but the climate had changed from semi-arid to humid by that time. The Kasauli Formation sediments are interpreted as being the product of deposition in a braided fluvial, alluvial fan environment. After deposition, the sediments were incorporated into a southward propagating imbricate thrust stack. The early foreland basin sediments are now found at three structural levels within the thrust stack; the highest structural level restores furthest to the north while the lowest structural level restores furthest to the south.