The thermal and diagenetic evolution of Carboniferous sandstones in the central Appalachian basin has been resolved using various techniques. Paleothermometers including vitrinite reflectance and fluid inclusions indicate that burial of Lower and Upper Pennsylvanian strata of the Appalachian Plateau in West Virginia exceeded 4.4 km during the late Permian and occurred at a rate of ~100 m/m.y. Exhumation rates of ~10-30 m/m.y. from maximum burial to present depth were constrained using published apatite fission track and radiogenic helium ages. Quartz, lithic and feldspar-rich sandstones from different stratigraphic intervals and locations were sampled from core (95 %) and outcrop (5%) to qualitatively and quantitatively evaluate sandstone diagenesis. A compositional multivariate data set compiled from point counts served as the basis for quantitative analysis of controls on sandstone diagenesis such as framework grain composition, paleoclimate and depositional environment. A priori groups (independent variables) corresponding to the controls were compared using digenetic products (dependent variables). Major conclusions of the analysis are, first, minerals that formed early appear to have been influenced by stratigraphic position. The distribution of siderite and iron-oxide/oxyhydroxide may reflect the second order paleoclimatic signature recognized throughout the Carboniferous, where siderite formed during everwet periods and iron-oxide/oxyhydroxide during semi-arid conditions, reflecting differences in redox. Second, framework grain composition controlled the distribution of diagenetic alterations and quartz cementation in the burial environment. Lithic arenites are deficient in authigenic quartz, yet have undergone various degrees of illitization. The quartz deficiency is attributed to compaction-related loss of primary porosity relatively early, which inhibited flow of silica-bearing fluids. Finally, no correlation can be demonstrated between depositional environment and diagenesis. Anomalously high fluid inclusion homogenization temperatures (> 215 °C) from Upper Pennsylvanian sandstones adjacent to the Alleghany Thrust Front indicate that tectonic setting played an important role in quartz authigenesis. The discrepancy between the fluid inclusion and vitrinite reflectance data imply that warm silica-bearing fluids, likely sourced from low-grade metamorphic reactions, were injected into Pennsylvanian sandstone aquifers during thrust loading associated with the Alleghanian orogeny. / Ph. D.

The Early Permian Unayzah A member in the Ghawar area of east-central Saudi Arabia is a prolific gas producer but is characterized by significant reservoir heterogeneity related to complex interbedding, on the scale of 5 meters or less, of eolian dune, sand sheet, interdune and ephemeral (playa) lake facies. Diagenetic products in Unayzah A developed during a continuum of eogenetic and mesogenetic reactions. Early or eogenetic cements are dominated by clay rims that formed at temperatures below 70oC. Oil migration along stylolites probably from Silurian source rocks occurred during the early mesogenetic stage followed by barite, quartz and carbonate cementation. Oil degradation at temperatures between 150o and 225oC produced acidic pore fluids that caused dissolution of earlier formed carbonates to generate secondary intragranular, moldic and micro pores. Thin, early clay and hydrocarbon rims as well as possible early microquartz cements inhibited cementation of primary intergranular pores that are only partially filled with quartz outgrowth crystals. Total porosity, including primary open pores, secondary pores, and bitumen-coated and filled pores ranges up to 27 percent. Reservoir quality and heterogeneity are a function of depositional environment and diagenesis in which eolian dune and sand sheet facies contain the highest total porosities and hence the best reservoir properties. Some previously recognized Stoke's surfaces are characterized by higher concentrations of quartz cement further compromising reservoir interconnectivity. / Master of Science

No description available.

Yes / Sam Lucy (1994: 26) has stated that a `recognised feature of pre-Christian early medieval cemeteries in eastern England is the smaller number of younger burials recovered¿. Although taphonomic factors such as the increased rate of decay of the remains of children and shallow depth of burial have been suggested as possible explanations for this phenomenon, these have been disregarded in favour of cultural influences, with younger children thought to have been disposed of in a different way from adult remains (Lucy, 1994; Härke, 1997; Crawford, 1999). This paper will review the evidence concerning the treatment of the remains of children during the Anglo-Saxon period. It will then review the factors affecting bone preservation, with special reference to the bones of children, and attempt to assess to what extent the under-representation of children in Anglo-Saxon cemeteries can be attributed to bone preservation and soil type. It will show that hypotheses should not be formulated without full consideration of the taphonomy that may affect the completeness of the archaeological record.

Initial published work suggested that Fe isotope fractionations recorded in sediments were a product of biological activity. Experiments and measurements of natural samples now indicate that Fe isotope fractionation can be the product of both biological and inorganic processes. Sedimentary iron sulphides provide unique information about the evolution of early life which developed under anoxic conditions. It is in these sedimentary Fe-S species and in particular in Archean and Proterozoic pyrites that the largest Fe isotope variations (up to a range of ~5‰ for δ56/54Fe) have been measured. Most research has focussed on potential processes responsible for the formation of a 56Fe depleted Fe(II) pool from which iron sulphides would precipitate without additional fractionation, recording the light Fe isotope composition of the pool. Much less attention has been given to the possibility that the iron sulphide forming mechanisms themselves could produce significant fractionations. The Fe-S system constitutes a diverse group of stable and metastable phases, the ultimate Fe sequestrating phase being pyrite. The aim of this study was to examine experimentally where Fe isotope fractionations occur during the abiotic formation of iron sulphides in order to assess whether or not the measured Fe isotope signatures in natural pyrite could be explained by chemical mechanisms only. Both analytical and experimental protocols were developed in order to determine the partition of Fe isotopes for each step towards diagenetic pyrite formation. 56/54Fe and 57/54Fe ratios were measured on an IsoProbe-P Micromass MC-ICP-MS, and all experiments were performed under oxygen-free N2 atmosphere. Supporting previously published data, the results indicate that the precipitation of the nanoparticulate iron(II) monosulphide mackinawite (FeSm) kinetically fractionates lighter isotopes with initial fractionations of Δ56FeFe(II)aq-FeS = 1.17 ± 0.16 ‰ at 25°C and Δ56FeFe(II)aq-FeS = 0.98 ± 0.16 ‰ at 2°C. The rate of isotopic exchange between Fe(II)aq and FeSm decreases as FeSm nanoparticles grow. Fe isotope exchange kinetics are consistent with i) FeSm nanoparticles that have a core–shell structure, in which case Fe isotope mobility is restricted to exchange between the surface shell and the solution and ii) a nanoparticle growth via an aggregation– growth mechanism. Because of the structure of FeSm nanoparticles, the approach to isotopic equilibrium is kinetically restricted at low temperatures. The equilibrium Fe isotope fractionation between Fe2+ aq and FeSm was determined using the three isotope method and is Δ56FeFe(II)-FeS = -0.33 ± 0.12 ‰ at 25°C and Δ56FeFe(II)-FeS = -0.52 ± 0.16 ‰ at 2°C. This suggests that at equilibrium, FeSm incorporates heavier isotopes with respect to Fe2+ aq, and the isotopic composition of most naturally occurring FeSm does not represent equilibrium. During pyrite formation, pyrite incorporates kinetically lighter isotopes with a fractionation Δ56FeFeS-pyrite ~ 2.2 ‰. Because pyrite is sparingly soluble in sedimentary environments, isotope exchange is prevented and pyrite does not equilibrate with its Fe(II) source. Combined fractionation factors between Fe2+ aq, mackinawite (FeSm) and pyrite permit the generation of pyrite with Fe isotope signatures that encapsulate the full range of sedimentary δ56Fepyrite recorded in both Archean and modern sediments. Archean Fe isotope excursions reflect various degrees of pyritisation, extent of Fe(II)aq utilisation, and variations in source composition rather than microbial dissimilatory Fe(III) reduction only. Our results show that sedimentary pyrite is not a passive recorder of the Fe isotope composition of the reactive Fe(II) reservoir forming pyrite. It is the formation process itself that influences pyrite Fe isotope signatures with consequent implications for the interpretation of sedimentary pyrite Fe isotope compositions throughout geological time.

To gain an understanding of the transfer of nutrients and trace elements from sediment pore waters to surface waters of eutrophic Lake Rotorua and the early diagenetic processes controlling the transfer, pore water chemistry in the sediments of Lake Rotorua was investigated over a one year period in 2006 by collection of sediment cores on three occasions and deployment of pore water equilibrators on two occasions. Pore water concentrations of Fe2+, Mn2+, S, PO4, NH4, As, Cd, and Pb were analysed. Phosphate and ammonium fluxes to the water column from the sediments were calculated from measured concentration gradients by Fick's law of diffusion. Gas present in the sediments was analysed for composition, and source, and its ebullition rate measured. Anaerobic oxidation of organic matter is indicated by negative Eh values. Sulfate reduction was indicated near the sediment-water interface and releases of Fe2+, Mn2+, PO4 and NH4 into the pore water from particulate material were associated with the reducing conditions. Peaks in concentration of nutrients and elements occurred at the sediment surface over summer and deeper in the pore water profile over the cooler months of May and September. Sampling with peepers at fine scales immediately above the sediment-water interface indicated the presence of a nepheloid layer where elements are actively being recycled. Sulfate reduction appears to occur in the layer above the sediment-water interface, indicating that dissolved oxygen has already been reduced. Phosphorus is possibly being removed by iron and manganese oxide/hydroxide precipitation 5 to 15 cm above the sediment-water interface. Pore water saturation calculations indicate that sulfides may be controlling concentrations of iron and possibly other metals in the pore water by formation of pyrite in the zone of sulfate reduction. Below the zone of sulfate reduction, siderite and vivianite may be precipitating and acting as an additional sink for iron and phosphorus. ii Nutrient release rates based on Fick's law of diffusion indicated 430 tonnes of dissolved phosphorus and 1150 tonnes of ammonium were released to Lake Rotorua's water column in 2006, suggesting nutrient release from the sediments is the dominant flux of nutrients to the water column of Lake Rotorua. Methanogenesis, from acetate fermentation, occurs below the zone of sulfate reduction, where it becomes the dominant process in organic matter degradation. Ebullition of gas was measured at 126 ml m-2 d-1 and this gas was comprised dominantly of methane. Possible remediation techniques that could reduce the internal load of nutrients released from the lake sediments include sediment removal by dredging or capping the sediments with an adsorbent or sealing layer. Capping the sediments could be compromised by ebullition of gas that would disrupt the capped layer, opening up pathways that allow more readily for exchange between pore water nutrients and the water column. Dredging is likely to stimulate the ebullition of most of the trapped gas and result in a rapid efflux of much of the nutrient rich pore water into the lake, however dredging the top 10 to 20 cm of the sediments may partially reduce phosphorus in the pore waters but would not substantially reduce ammonium and fluxes would remain similar to current levels. Improving redox conditions in the sediments could reduce pyrite formation improving phosphorus binding with iron.

Human activities such as urban settlement, farming, forestry and recreation, have caused deterioration of water quality in many freshwater lakes worldwide. Apart from anthropogenic impacts, it is also recognized that climate has a direct influence on lake water temperature, nutrient loads, phytoplankton abundance and chemistry. However, little is known about the potential effects of future climate change on lake water quality. Understanding the dynamics, abundance and availability of nutrient pools in lake bottom sediments is fundamentally important for predicting how, and over what time-scales, lake ecosystems will respond to future scenarios such as climate change, in-lake restoration or altered external nutrient loading. Through a sediment field study on 14 different lakes, and applications of complex lake ecosystem models to three New Zealand lakes, this study examined the spatial and temporal dynamics of sediment nutrient concentrations, and made considerations of the effects of restoration measures and future climate change on lake water quality. To gain insight into processes influencing the dynamics of horizontal and vertical gradients of sediment nutrient concentrations, intact sediment cores were collected from twelve lakes within the Bay of Plenty province, North Island of New Zealand. In addition, intact sediment cores were collected from shallow Lake Te Waihora (Ellesmere) in the Canterbury province, South Island of New Zealand and shallow Lake Taihu in the Jaingsu province, China. The observed vertical concentration profiles of total phosphorus (TP) in the sediments revealed that the shape of these profiles can be similar across gradients of widely differing trophic status. Empirical and mechanistic steady state profile models were derived to describe the vertical distribution of total carbon (TC), total nitrogen (TN) and TP concentrations in the sediments. These models revealed that density-driven burial and biodiffusive mixing, which in the models also includes effects of redox-driven gradients, are strongly correlated with vertical gradients of sediment TC, TN and TP content, whereas lake trophic status was not. Despite enhancing knowledge of the processes influencing vertical gradients of sediment nutrient concentrations, little is known about the rates at which sediment nutrient concentrations may change as a response to changes in external loading or climate. Studies into the composition of bottom sediments have been undertaken intermittently over the past three decades for the 12 lakes in the Bay of Plenty. These studies, together with the data collected in this study, were used to quantify temporal changes in sediment chemistry across the lakes. Comparison of the data collected in this study with results from a survey in 1995 showed that surficial sediment (0-2 cm) TP concentrations have increased in three of the 12 lakes, at rates ranging from 27.5 to 114.4 mg P kg-1 dry wt yr-1. TN concentrations in surficial sediments have increased in nine of the 12 lakes at rates ranging from 51.8 to 869.2 mg N kg-1 dry wt yr-1. A correlation analysis revealed that temporal changes in sediment TP and TN concentrations were not significantly linearly related (pgt0.05) to catchment area or temporal changes of different water column indices considered to reflect lake trophic state, including annual mean water column concentrations of TP, TN or chlorophyll a (Chl a). While vertical profiles of sediment nutrient concentrations can be used to provide information about historical changes of trophic status in lakes, little is known about horizontal variability of sediment nutrient concentrations, including possibly relationships with horizontal variations in water column variables. In the large, shallow and eutrophic Lake Taihu, China, there are distinct horizontal water column concentration gradients of nutrients and Chl a. Concentrations are generally high in the north, where some of the major polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. To test whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient concentrations within the bottom sediments of Lake Taihu, I examined correlations between concentrations of TP and TN in surficial sediments (0-2 cm) and TP, TN and Chl a concentrations in water column samples determined for 32 sites in 2005. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related significantly, though weakly, to annual mean water column concentrations of TP and TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (p gt 0.05). To better understand the effects of future climate change on lakes of different trophic status, I applied the one-dimensional lake ecosystem model, DYRESM-CAEDYM, to oligo-mesotrophic Lake Okareka, eutrophic Lake Rotoehu and highly eutrophic Lake Te Waihora. All three models were calibrated based on a three-year period (July 2002 - June 2005) and validated on a separate two-year period (July 2005 - June 2007). The model simulations generally showed good agreement with observed data for temperature, dissolved oxygen (DO), and total nutrient and Chl a concentrations. To represent a possible future climate of 2100, temperature predictions were derived from the regional climate model, DARLAM, based on the Intergovernmental Panel on Climate Change (IPCC) A2 scenario, which suggests that air temperatures by the year 2100 will increase by an average of 2.5 'C and 2.7 'C for the Bay of Plenty and the Canterbury province, respectively, relative to the base scenario (years 2002-2007). Model simulations of the future climate scenarios indicate that climatic changes generally will lead to a degradation of lake water quality in all three lakes, especially during summer months, and further suggest that the effects on annual mean surface concentrations of TP, TN and Chl a will be equivalent to an increase in external TN and TP loading by 25-50%. Simulations for Lake Rotoehu, where diatoms and cyanophytes were represented in the conceptual model, further suggest that cyanophytes will be more abundant in the future, increasing by gt15% in annual mean biomass. Although the effects of climate change may be delayed or slightly mediated by the chemical resilience of the sediment nutrient pools, the effects of climate change on lake water quality in the New Zealand lakes will be of a magnitude that should be considered as management strategies are planned and implemented, thus increasing the probability of successful preservation or improvement in water quality in future decades.

The Upper Devonian Grosmont shelf complex is the worlds largest heavy oil deposit hosted in carbonates, with an estimated >50 billion cubic meters (318 to probably 406 bbls) of initial volume in place. At present the Grosmont is not yet under production. This study involves log interpretation, core examination; facies description; strontium, sulphur, carbon, and oxygen isotope analysis. The Grosmont is subdivided into four shallowing-upward cycles. Most Hondo evaporites are part of the Upper Grosmont 3 and Lower Grosmont and were deposited in a series of small, shallow subaqueous brine ponds or in an extensive lagoon. In the eastern part of the area, the Hondo appears to be dissolved resulting in solution-collapse breccias. Other diagenetic processes that were important in shaping the present reservoir characteristics were pervasive dolomitization and dolomite recrystallization, fracturing, and karstification.

Bottom water hypoxia and its influence on the environment have been topics of increasing concern for many coastal regions. This research addresses both spatial and temporal variability in sediment biogeochemistry at the southeastern region of Corpus Christi Bay, TX, where seasonal (summer) hypoxia occurs. Traditional techniques for determination of a variety of dissolved and solid components, benthic oxygen demand, and sulfate reduction rates were augmented by measurements using solid state microelectrodes to simultaneously determine concentrations of dissolved O2, Mn2+, Fe2+, and [sigma]H2S in multiple small - interval (1 mm) depth profiles of sediment microcosms. Oxygen concentrations in the overlying water were manipulated in the sediment microcosms and electrode depth profile measurements were made over ~ 500 hours of experimentation. Laboratory and field microelectrode results were in good agreement for both norm - oxic and anoxic time periods. Results indicated that iron (Fe2+) and sulfide ([sigma]H2S) were the redox reactive species in these sediments. During hypoxic conditions an upward migration of dissolved Fe2+and [sigma]H2S through the sediment column and, at times, into the overlying water was observed as the dissolved oxygen concentrations decreased. A corresponding decline in the vertical extent of these redox species occurred when the overlying water was re-oxidized. When both dissolved iron and sulfide coexisted, FeS minerals were formed in the sediment, preventing sulfide diffusion into the overlying water. However, after a long duration of hypoxia (> 200 hours) this buffering capacity was exceeded and both iron and sulfide penetrated into the overlying waters. Results indicated that iron may have a greater influence on hypoxia than sulfide because its concentration in the overlying waters during induced hypoxia was an order of magnitude greater than those of sulfide. Moreover, in the southeastern region of the Bay, where mixing was minimal and the water column was shallow, the sediments alone may have caused the onset of the hypoxic event in a relatively short time period (< 5.5 days). These results demonstrated that in shallow marine environments where seasonal hypoxia occurs, such as Corpus Christi Bay, the associated major changes that take place in the sediment biogeochemistry must be included in benthic - pelagic models for overlying water hypoxia.

Bottom water hypoxia and its influence on the environment have been topics of increasing concern for many coastal regions. This research addresses both spatial and temporal variability in sediment biogeochemistry at the southeastern region of Corpus Christi Bay, TX, where seasonal (summer) hypoxia occurs. Traditional techniques for determination of a variety of dissolved and solid components, benthic oxygen demand, and sulfate reduction rates were augmented by measurements using solid state microelectrodes to simultaneously determine concentrations of dissolved O2, Mn2+, Fe2+, and [sigma]H2S in multiple small - interval (1 mm) depth profiles of sediment microcosms. Oxygen concentrations in the overlying water were manipulated in the sediment microcosms and electrode depth profile measurements were made over ~ 500 hours of experimentation. Laboratory and field microelectrode results were in good agreement for both norm - oxic and anoxic time periods. Results indicated that iron (Fe2+) and sulfide ([sigma]H2S) were the redox reactive species in these sediments. During hypoxic conditions an upward migration of dissolved Fe2+and [sigma]H2S through the sediment column and, at times, into the overlying water was observed as the dissolved oxygen concentrations decreased. A corresponding decline in the vertical extent of these redox species occurred when the overlying water was re-oxidized. When both dissolved iron and sulfide coexisted, FeS minerals were formed in the sediment, preventing sulfide diffusion into the overlying water. However, after a long duration of hypoxia (> 200 hours) this buffering capacity was exceeded and both iron and sulfide penetrated into the overlying waters. Results indicated that iron may have a greater influence on hypoxia than sulfide because its concentration in the overlying waters during induced hypoxia was an order of magnitude greater than those of sulfide. Moreover, in the southeastern region of the Bay, where mixing was minimal and the water column was shallow, the sediments alone may have caused the onset of the hypoxic event in a relatively short time period (< 5.5 days). These results demonstrated that in shallow marine environments where seasonal hypoxia occurs, such as Corpus Christi Bay, the associated major changes that take place in the sediment biogeochemistry must be included in benthic - pelagic models for overlying water hypoxia.