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Accretionary complexes that form at subduction zones develop a spectrum of styles of deformation that range between coherent forms in which the processes of thrusting predominate and incoherent forms in which melanges, formed by such processes as mud diapirism, are the dominant constituent. This thesis examines processes that control the development of these accretionary styles by comparing geophysical observations of the modern Barbados Ridge accretionary complex, with ancient subaerially exposed examples in Sabah, N. Borneo and W. Timor.A structural and lineament map of the offshore regions of the Barbados Ridge complex has been constructed using GLORIA. Seabeam and seismic data. It reveals marked changes in the surface structure of the accretionary wedge, particularly where basement ridges associated with oceanic fracture zones underthrust it. It also documents the presence of large numbers, of mud diapirs in its southern regions. The mud diapirs appear to be associated with the accretion of thick sequences of turbidites and their distribution is proposed to relate to the subcretion or underplating of underconsolidated material to the base of the complex. Fieldwork in Sabah and Timor concentrated on describing features associated with currently active mud diapirs, and potential ancient examples. A classification of the various forms of diapiric activity has been erected as part of a general discussion on the importance, genesis and emplacement of mud diapirs. In addition, the general structural development of the accretionary complex in W. Sabah was found to broadly resemble that of the frontal regions of a particularly thin part of the Barbados Ridge complex studied during DSDP Leg 78A and ODP Leg 110.A series of principal controls or boundary factors appear to control the general development of accretionary complexes. During the course of this study the importance of the sedimentary input, critical taper (or balance between boundary stresses and gravitational body forces) and subducting basement topography has been made particularly clear.

In this thesis, an ontology for the geological mapping domain is constructed using the Protégé ontology editor. The Geological Mapping ontology is developed using terms and relationships, and their properties, as they relate to creating a geologic map. This vocabulary is semantically modeled in the ontology using Web Ontology Language (OWL). The purpose of this thesis is to exemplify how an ontology can be designed and developed to represent geological knowledge as it relates to mapping.

<p> Fractures are often leakage pathways for fluids through low-permeability rocks that otherwise act as geologic barriers to flow. Flow of fluids that are in chemical disequilibrium with the host rock can lead to mineral precipitation, which reduces fracture permeability. When fracture surfaces contain a single mineral phase, mineral precipitation leads to fast permeability reduction and fracture sealing. However, the feedback between precipitation and permeability may be disrupted by mineral heterogeneities that localize precipitation reactions and provide paths of low-reactivity for fluids to persist over relatively long time-scales. In this dissertation, I explore the role of mineral heterogeneity on precipitation-induced permeability reduction in fractures. To do this, I use a combined experimental and numerical approach to test three hypotheses: (1) Mineral heterogeneity prolongs fracture sealing by focusing flow into paths with limited reactive surface area, (2) Precipitation-induced transport alterations at the fracture-scale are controlled by three-dimensional growth dynamics at the grain-scale, and (3) The effects of mineral heterogeneity become more pronounced as mineralogy and surface roughness become autocorrelated over similar length-scales. </p><p> Direct measurements of mineral precipitation using transmitted light methods in a transparent analog fracture show that mineral heterogeneity can lead to the progressive focusing of flow into paths with limited reactive surface area, which is in support of (1). In this experiment, flow focusing led to a 72% reduction in the max precipitation rate; measurements of the projected mineralogy show that this was due to focusing of large dissolved ion concentrations into regions that contained 82% less reactive surface area than the fracture-scale average. Results from a newly developed reactive transport model that simulates precipitation-induced fracture surface alterations as a three-dimensional process are in good qualitative agreement with these experimental observations. Comparison of these results with a reactive transport model that represents precipitation as a 1D alteration of the fracture surfaces show that this flow-focusing process is driven by lateral growth of reactive minerals across the fracture-plane, which supports (2). Lastly, results from simulations in fractures that contain varied degrees of heterogeneity show that precipitation leads to a competition between two feedbacks: (i) precipitation-induced reactive surface area enhancement, which increases precipitation rates, and (ii) precipitation-induced permeability reduction, which decreases precipitation rates. When surface roughness and mineral heterogeneity provide persistent paths of limited surface area, the reactive transport becomes very sensitive to local permeability reduction. Simulation results show that this prolongs the fracture-sealing process and can lead to a reduction in fracture-scale precipitation rate, which supports (3). Furthermore, the results presented in this dissertation demonstrate that predictions of fracture sealing by mineral precipitation can be easily misinformed by studies that ignore small-scale mineral heterogeneity and neglect the three-dimensional nature of precipitation-induced fracture surface alterations.</p><p>

A numerical model was developed to evaluate the effect of fuel alcohols present in reformulated gasoline on BTEX natural attenuation and groundwater plume elongation. The model, developed as a module for the RT3D (Reactive Transport in 3-Dimensions) model, includes commonly considered fate and transport processes (advection, dispersion, adsorption, biodegradation and depletion of electron acceptors during biodegradation) and substrate interactions previously not considered (e.g., a decrease in the specific benzene utilization rate due to metabolic flux dilution and/or catabolite repression) as well as microbial populations shifts, cosolvency effects, alcohol toxicity and source zone depletion dynamics that affect groundwater concentrations of gasoline constituents. The model was used to (1) evaluate the relative importance of benzene plume-elongation mechanisms, (2) how the concentration of ethanol in reformulated gasoline affects the length and longevity of benzene plumes, and (3) the effects of five fuel alcohols (methanol, ethanol, 1-propanol, iso-butanol and n-butanol) on the natural attenuation of benzene in fuel contaminated groundwater. Model simulations showed that all fuel alcohols can hinder the natural attenuation of benzene, due mainly to accelerated depletion of dissolved oxygen during their biodegradation (leading to strongly anaerobic methanogenic conditions) and a decrease in the specific degradation rate for benzene (due to catabolite repression and metabolic flux dilution). Thus, releases of alcohol-blended gasoline should result in longer benzene plumes compared to regular gasoline. However, the simulated lifespan of benzene plumes was shorter for blends with higher alcohol contents, due to a lower mass of benzene released, and increased microbial activity associated with fortuitous growth of BTEX degraders on fuel alcohols. Benzene plume elongation and longevity were more pronounced in the presence of alcohols that biodegrade slower (e.g., propanol and n-butanol), forming longer and more persistent alcohol plumes. In general, our model indicates that higher alcohols blends have a lower impact on BTEX natural attenuation, while more recalcitrant alcohols have a higher impact. Thus, E85 (85% Ethanol) had the lowest impact on BTEX plume elongation and B10 (10% n-Butanol) had the highest impact. However, simulations were highly sensitive to site-specific biokinetic coefficients for alcohol degradation, which forewarns against generalizations about the level of impact of specific fuel alcohols on benzene plume dynamics, and calls for further pilot-scale and field research to validate the assumptions and results from this model.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Geological Sciences." Includes bibliographical references.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Geological Sciences." Includes bibliographical references.

Five outcrop sections (Wadi Mi'aidin, Wadi Bani Kharus, Jebel Madar, Jebel Madamar and Jebel Salak), exposing Thamama and Wasia Group sediments were sedimentologically logged and sampled. Thin sections of each of the Thamama Group samples were prepared for micropalaeontological and microfacies analysis. The foraminifera, calcareous algae and calpionellids in each sample were recorded in order to provide a means of biostratigraphic subdivision, and together with microfacies analysis and sedimentological observations made in the field, provide a means of elucidating the depositional environments of the Thamama Group in the study area. Correlation between outcrop sections has been attempted using a biozonation scheme developed in the course of this project, and also by graphic correlation techniques. The taxonomy of 39 genera including 56 species of key foraminifera, calcareous algae and calpionellids is reviewed in detail. A complete revision of Cretaceous Middle Eastern lithostratigraphic nomenclature is required. Some recommendations for such a revision are proposed. Within the Thamama Group, 13 biozones/subzones are recognised using the extinction and inception events for key taxa. Both biozonal correlation and graphic correlation demonstrate that most Thamama Group formations are diachronous and may also be condensed at some localities. Biostratigraphic studies demonstrate that in the Central Oman Mountains region the Thamama Group formations are of the following ages: The Rayda Formation is of Early Berriasian age. It possibly extends into the earliest Valanginian at some localities (eg. Wadi Bani Kharus). The Salil Formation is of Berriasian - Valanginian age, possibly Hauterivian in age in its upper part at some localities. The Habshan Formation is of Hauterivian age everywhere, with possible extension into the Late Valanginian in its IOWCT part The Lekhwair Formation is essentially of Hauterivian - Barremian age (often largely Hauterivian). The Kharaib Formation is of typically Late Barremian - Early Aptian age, whilst the Shuaiba Formation is of Early Aptian age. Thamama Group deposition took place on an initially downwarped carbonate ramp, prograding towards the Tethyan Ocean (towards the north and east). Offshore palaeowinds precluded the development of reefs, but an oolitic shoal was located at the margin of the ramp, at least during Hauterivian times.

A stratigraphic investigation of the marshland adjacent to the five main estuaries in Suffolk and offshore of the Alde estuary has been made. The results are used to establish a Holocene evolution for the Suffolk coast and are compared with coastal sequences elsewhere in East Anglia. The stratigraphy of the Blyth estuary in north Suffolk comprises four lithostratigraphic units; a basal freshwater peat overlain by estuarine Lower Clay, Middle Peat and Upper Clay representing two phases of transgressive overlap sandwiching a phase of regressive overlap. Peat formation began about 6750 yrs BP and continued until 6500 yrs BP when the sequence was inundated and eroded by marine waters during the initial phases of transgressive overlap. Estuarine silt/clay deposition (both low and high intertidal flat) persisted until about 4500 yrs, BP when a transition to further peat growth occurred. The second phase of estuarine sedimentation (predominantly high intertidal flat) began at about 4300 yrs BP. These dates correlate well with dates for similar tendencies of sea-level movement in the Fens, north Norfolk and Broadland. The Blyth sequence contrasts with the Holocene sequence in the Deben, Orwell and Stour estuaries in south Suffolk which comprises a continuous estuarine clastic sequence without an intermediate peat. Estuarine conditions are believed to have begun about 8000 yrs BP and a high subsidence rate combined with low'sediment accumulation rates caused the estuaries to remain flooded throughout the Holocene. The onshore data, plus data offshore from the Alde estuary has been used to evaluate the position of the coast after 8700 yrs BP. The coastal evolution is interpreted to have been controlled by the movement of coastal barrier or spit systems. A significant barrier breaching episode is believed to have occurred post-7000 yrs BP causing erosional contacts and development of higher energy-estuarine environments. After, this time, the, Blyth estuary was significantly affected by further spit or barrier growth. The Alde, Deben, Orwell and Stour estuaries, however, were essentially barrier (spit) free during the Holocene and protected from southerly longshore drift by a land barrier north of the Alde estuary. The land barrier was eventually breached and subsequent formation of Orford Ness and Landguard Spit began. The present-day inland saline penetration up the river Blyth is the maximum achieved at any time during the Holocene. This contrasts with Broadland and Fenland where the maximum penetration occurred about 2000 years earlier. The main reason for the differences appears to be a higher coastal erosion rate in Suffolk compared to Norfolk (Fenland is actively prograding).