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.

Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (leaves 148-150). Also available via World Wide Web.

The use of planktonic foraminiferal Mg/Ca ratios to reconstruct past sea surface temperatures (SST) is prevalent in the literature. The perceived simplicity of the underlying chemistry and ease of measurements are alluring. Canonically, temperature is thought to be the primary control on the shell Mg/Ca values. Additionally, an appeal of this proxy is that it can be combined with shell ä18O values to reconstruct changes in the local ä18O of seawater, a proxy for salinity. However, we have identified a salinity effect on the Mg/Ca signal recorded in planktonic foraminifera influencing samples from open ocean locations. This effect causes excess Mg incorporation, higher than predicted by theory, in high salinity regions for the planktonic foraminiferal species, Globigerinoides ruber (white). The shell "excess Mg/Ca" resides within the primary calcite lattice of the shell itself and may be related to the observed cyclic banding of high and low Mg/Ca calcite with the foraminiferal shells. We derive new equations which describe the relationship between shell Mg/Ca, ocean sea surface temperature, salinity, and bottom water ÄCO32-. We also define new equations for ocean temperature and salinity using shell Mg/Ca, ä18O, and bottom water ÄCO32-, which take advantage of the dual sensitivity of shell Mg/Ca and ä18O to temperature and salinity. We apply these results downcore at several locations to assess the influence on paleo-reconstructions. These results are widely applicable to paleoceanographic studies and should allow more accurate reconstructions of both temperature and salinity. Below are brief outlines of the dissertation chapters: 1) A poor correlation between Mg/Ca derived and observed (WOA05) SST was found for 64 coretops in the (sub)tropical Atlantic. Shell-derived SST values from the subtropical gyres were overestimated and the residual "excess Mg/Ca" was well correlated with surface salinity. In this chapter, new calibration equations are developed for the Atlantic Ocean using paired Mg/Ca and ä18O measurements, along with the bottom water ÄCO32-, to predict temperature and salinity. These equations are validated using published coretop data and yield accurate estimates for SST and salinity. 2) The ITCZ is clearly identified in the oceans as the region where temperatures are the highest and salinities are the lowest. These oceanographic fingerprints can be used to track ITCZ variability over the ocean through time. Both canonical equations and the new equations from chapter 1 are used here to reconstruct SST and ä18Oseawater/Salinity gradients since the LGM in the equatorial Atlantic. The marine Atlantic ITCZ migrated in excess of 10° latitude away from its modern position, during both the LGM and early Holocene, supporting climate model results as well as coastal and terrestrial paleohydrological records that document the sensitivity of ITCZ position to both high- and low-latitude forcing. 3) The nature of the excess shell Mg/Ca and the mechanism for incorporation is poorly understood. We investigated excess Mg/Ca using SEM, flow through ICP-MS (FT-ICP-MS) and electron microprobe analyses. SEM and FT-ICP-MS results suggest the excess shell Mg resides within the primary structure of the calcite lattice. Electron microprobe maps of shell Mg/Ca confirm that the excess Mg/Ca lies within the shell itself, likely within the high Mg/Ca calcite bands. These findings suggest the incorporation of shell "excess Mg/Ca" first identified in chapter 1 is not related to post-depositional diagenetic alteration. These results will help elucidate the mechanism responsible for enhanced Mg uptake in high salinity settings. 4) Currently there exist no globally applicable calibration equations relating oceanographic parameters to foraminiferal shell Mg/Ca. In this chapter, we develop new, global calibration equations for G. ruber (white) following the methods of chapter 1. We find that the relationship between shell Mg/Ca and salinity is non-linear, with a threshold value near a salinity of 35, below which there is little influence of salinity on shell Mg/Ca. These equations were validated with published data and appear to be robust. By accounting for the additional influence, alkenone and foraminiferal Mg-Ca derived SST records may be reconciled in for some locations, particularly where there were likely to have been large variations of salinity in the past. These results represent a significant advance for the paleoceanographic community.

Thesis (Ph.D.) - University of St Andrews, November 2007.

Thesis (Ph. D.)--University of Adelaide, Dept. of Geology and Geophysics, 1987. / Includes bibliographical references (leaves 275-290).

No description available.

Bibliography: leaves 275-290 / xviiii [i.e. xvix], 352 leaves : ill ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1987

Les structures de combustion constituent un témoin de la fréquentation humaine et leur étude permet d’appréhender un aspect du mode d’occupation d’un lieu donné. Ainsi, pour compléter les approches classiques qui s’intéressent à la typologie des foyers, à la fréquence des feux, à la nature des combustibles, etc., une caractérisation thermique de ces structures a été proposée. Elle s’appuie sur les impacts thermiques enregistrés par les sédiments soumis aux feux et plus précisément sur les modifications des propriétés de thermoluminescence (TL) et de magnétisme avec la chauffe.Le site-laboratoire est celui de la grotte de Fraux (Dordogne), occupée à l’Âge du bronze, dont le statut et le mode d’occupation pose question puisqu’elle présente tant des vestiges domestiques (sols de circulation, foyers, mobiliers) que des vestiges symboliques (manifestations pariétales, dépôts de mobilier). La place importante des foyers parmi ces vestiges a induit une étude spécifique de ces structures. En effet, ce site recèle plus d’une soixantaine de structures de combustion et, aspect important pour notre approche archéométrique, présente un état de conservation exceptionnel puisque la grotte est restée fermée depuis l’occupation de l’Âge du bronze.L’étude de certains foyers de la grotte des Fraux a permis de tester le potentiel de paléothermomètres fondés sur ces deux propriétés indépendantes à savoir la TL des grains de quartz et le magnétisme des oxydes de fer contenus dans les sédiments. Le paléothermomètre TL a été élaboré en comparant les signaux TL d’échantillons provenant de foyers archéologiques à ceux de références thermiques chauffées en laboratoire. Pour le magnétisme deux pistes ont été exploitées : les températures de déblocage de l’aimantation rémanente et l’évolution de la signature magnétique -minéralogie et taille de grain) avec la chauffe. La détermination des paléotempératures atteintes par les sédiments substrats des structures de combustion apporte une première indication sur leur intensité de chauffe. Afin d’étalonner ces informations paléothermométriques en termes d’énergie mise en jeu, des feux expérimentaux ont été réalisés. Ils ont permis de comparer les impacts thermiques entre feux archéologiques et feux expérimentaux, de construire un échantillonnage d’histoire thermique connue, mais aussi d’estimer les températures atteintes, les épaisseurs de sédiments affectés, les quantités de combustibles consommés pendant un temps donné, la quantité d’énergie dégagée par la combustion… Ces expérimentations ont aussi servi de base à une modélisation de la propagation de la chaleur dans les sédiments. Les simulations effectuées dans ce modèle numérique permettent alors d’estimer un temps minimal de fonctionnement des structures de combustion.Nous disposons ainsi d’un nouvel outil pour la caractérisation thermique de foyers archéologiques. / The study of the combustion structures, which are a remaining evidence of the human occupation, can give information about the way of occupation of a site. In this research we decided to complete the classical approaches of combustion structures generally based on typological description of hearths, frequency of fires, nature of fuel, etc. by a a thermal characterisation. This study deals with the thermal impacts recorded by the fired sediment. More precisely, the modifications of both thermoluminescence (TL) and magnetism properties with heating were investigated.The laboratory-site is the cave of Les Fraux (Dordogne, France) which was occupied in the Bronze Age. The archaeologists were wandering about the function and the way of occupation of this cave because of the existence of both domestic vestiges (archaeological occupation grounds, hearths, and ceramics) and symbolic evidences (rock art and votive ceramic deposition). A specific study of the combustion structures had started considering the significant number of hearths, more than sixty, and their importance in the human occupation. In addition, as the cave remained closed since the Bronze Age, the hearths are in an excellent state of conservation and that is an important point for our archaeometric study. The thermal characterisation of some hearths from the cave of Les Fraux firstly consisted in studying the paleothermometer potential of two properties: the thermoluminescence of quartz grains and the magnetism of iron oxides taken from the sediments. The TL paleothermometer was established by comparing TL signals of samples from archaeological hearths and those of thermal references heated in laboratory. Two properties were explored for the magnetic paleothermometer: the unblocking temperatures of the remanent magnetization and the evolution of magnetic signature (mineralogy and grain size) with heating. The paleotemperatures determined for the sediment of the hearths give a first information about the heating intensity of fires.Then experimental fires were carried out to calibrate paleothermometric data in quantity of energy and wood consumption, to check the suitability of laboratory thermal references, and to characterise the process of heat transfer inside the sediment. Finally, a numerical modeling of heat propagation within the sediment was implemented from temperatures recorded during fire experimentations. Numerical simulations performed in this model allowed us to estimate a minimal duration of functioning of the combustion structures.A novel tool for the thermal characterisation of combustion structures is then available.

The potential of Arctica islandica, a long lived marine bivalve with a lifespan of over 300 years, to reconstruct a high resolution (sub-annual) climate record is explored in this thesis. Fluctuations in trace element and isotopic data from live-collected specimens from Irvine Bay, NW Scotland are compared to instrumental (particularly temperature) data. X-ray absorption spectroscopy data demonstrate the coordination state of Sr and Mg within the shell. These are consistent with models in which Sr substitutes ideally for Ca in aragonite, and Mg is bound predominantly to organic molecules. Sr/Ca incorporation may be influenced by changes in the crystal nucleation, propagation and growth rate as well as vital effects. However any effect of seawater temperature on Sr/Ca incorporation was obscured by these other factors. Mg concentration is not a linear function of a single environmental variable or organic content within the shell, indicating that Mg uptake is biologically mediated. Ba variation shows sporadic increases (of >500% above baseline) in both shells, the timing of which is similar between the prismatic layer and umbo region. The maxima are, however, not synchronous between the two shells analysed. The controls on Ba uptake require further research, but low Ba/Ca may reflect Ba/Ca concentrations within the seawater. Aliquots taken from cod otoliths show that micromilling has negligible effect on δ¹⁸O. The range of reconstructed temperature from δ¹⁸O profiles Arctica islandica shows good agreement with the sea surface temperature data from the nearby Millport marine station to within 2.1 °C. However, both the interannual and intra-annual variation appears to be sensitive to changes in temporal resolution resulting from changes in growth rates. Modelling of δ¹⁸O highlights dependence on changes in temporal resolution of the sampling, in addition to temperature and salinity. Results from the radiocarbon pilot study show that Arctica islandica is a suitable archive for changes in radiocarbon associated with anthropogenic ¹⁴C fluxes.