“Xeno-pumice” describes a pumice-like material, high in silica content and vesiculation, found as a xenolith in a more mafic rock. A xeno-pumice is an indicator of magma-crust interaction; however, the origin, nature, and processes behind this xenolith are still debated. Xeno-pumice has been described in a few places worldwide, including the Canary Islands in Spain, Indonesia, Iceland, the USA, Chile and Mexico. This thesis, for the first time, presents and analyzes the mineralogy, textural features, whole-rock geochemistry (major and trace element), and oxygen isotopes of xeno-pumice samples found in Harrat Rahat, Saudi Arabia. Harrat Rahat is a volcanic field whose last eruption was in 1256A.D. and reached the outskirts of Madinah, one of the main cities in Saudi Arabia. Harrat Rahat is characterized by a wide range of volcanic products: from basalts to trachyte. Previous studies suggested that this chemical variation has its source in the mantle and minor crustal contamination; however, the xeno-pumice samples found indicate magma-crust interaction. Thus, in this thesis, the crust-melt interaction hypothesis is addressed as a process that could modify the composition of the melt and thus the resulting volcanic products and eruptive style of the volcanic field. Indeed, the chemistry and oxygen isotope values of the studied volcanic rocks show a variation in composition, which is suggested to be the consequence of crust-melt interaction. The petrology, chemistry and oxygen isotope values suggest that the melt interacted with either the metamorphosed plutonic portion of the upper Arabian crust or with (meta-) sediments below Harrat Rahat. Finally, this thesis proved that magma-crust interaction occurred at Harrat Rahat, which has important implications for interpreting eruption mechanisms and mantle sources.

No / 'Small beer', 'wort drinks' and 'pottage' may have been regularly consumed by children during the Medieval Period. This culturally mediated behaviour could have affected the oxygen isotope composition of their water intake beyond that which is accommodated in the current conversion equations used in archaeological studies to assess environmental origins. Experimental data shows that brewing may increase the δ18O value of ale by 1.3‰ over that of the initial water ('liquor') used, boiling water to make hot drinks raises the δ18O value of the fluid consumed by ~0.4‰ and slow-cooking using a large stew pot results in an increase in the oxygen isotope composition of the 'pottage' by an average of 10.2‰ after 3 hours of cooking. Thus, if ingested fluids included 20% from ale, 10% from 'teas' and 20% from stews (the latter increased from -7.0‰ to +3.2‰ by three hours of cooking) then the overall effect on the calculated drinking water value from the tooth enamel will be +2.3‰ . / NERC

Die Verhältnisse der stabilen Isotope des Sauerstoffs (16O, 17O, 18O) und des Kohlenstoffs (12C, 13C) im biogenen Apatit des Zahn- und Knochenmaterials von Säugetieren lassen Rückschlüsse auf die Isotopie der entsprechenden Sauerstoff- und Kohlenstoffquellen zu. Die Isotopenverhältnisse dieser Quellen (z.B. Trinkwasser, Luftsauerstoff, Nahrung) sind an bestimmte Umwelt- und Klimabedingungen wie Temperatur, Luftfeuchtigkeit, CO2-Konzentration, Bioproduktivität, Art der Vegetation, Grad der Vegetationsdichte etc. geknüpft. Bestimmt man die Sauerstoff- und Kohlensoffisotopenverhältnisse in diagenetisch unalteriertem fossilem Säugetiermaterial können Aussagen über solche Klima- und Umweltparameter weit in die Erdgeschichte zurück getroffen werden. Darüber hinaus ist es möglich Informationen über Lebensweise und Verhalten der untersuchten Taxa, wie z.B. Wanderverhalten, Geburtensaisonalität, Trinkverhalten, Nahrungspräferenzen, Ressourcenteilung und Habitatnutzung zu erlangen. Seit dem Beginn der Forschungen auf diesem Gebiet in der 70er und 80er Jahren des 20. Jahrhunderts ist eine große Zahl von Studien erschienen, welche sich der Untersuchung der Sauerstoff- und Kohlenstoffisotopie (18O/16O, 13C/12C) des Zahn- und Knochenmaterials rezenter und fossiler (vorwiegend großer) Säugetiere zu diesen Zwecken widmen. Noch keine zwei Jahrzehnte ist es her, dass erkannt wurde, das troposphärischer Sauerstoff eine anomale 3-O-Isotopenzusammensetzung (17O/16O, 18O/16O) besitzt, die signifikant von fast allen anderen terrestrischen Materialien abweicht. Diese wird in Folge von nicht massenabhängiger Fraktionierung durch photochemische Prozesse in der Stratosphäre hervorgerufen und durch Gasaustausch in die Troposphäre übertragen. Die Magnitude dieser Sauerstoffisotopenanomalie ist eine Funktion der atmosphärischen CO2-Konzentration, sowie der globalen Bioproduktivität. Kann die 3-O-Isotopie des Luftsauerstoffs zu vergangenen Zeitpunkten in der Erdgeschichte rekonstruiert werden, lässt dies somit auch Rückschlüsse auf die entsprechende CO2-Konzentration bzw. die globale Bioproduktivität zu. Geologische Archive die dies ermöglichen sind jedoch kaum vorhanden. Da für Säugetiere der eingeatmete Luftsauerstoff neben Trinkwasser und freiem Wasser in der Nahrung zu den wichtigsten Sauerstoffquellen zählt, ist biogener Apatit rezenter und fossiler Säugetiere eines der wenigen möglichen Materialien die das Potential haben, ein solches Archiv darzustellen. Die vorliegende Arbeit untersucht die Variation der 3-O-Isotopenzusammensetzung im Bioapatit rezenter Säugetiere, sowie deren Bedeutung als neuen Proxy zur paläo-CO2-Rekonstruktion und als Indikator für diagenetisch alteriertes Skelettmaterial. Desweiteren werden zwischenartliche, innerartliche und intraindividuelle Variationen der Sauerstoff- und Kohlenstoffisotopie im Bioapatit rezenter Nagetiere untersucht um eine bessere Interpretationsgrundlage für entsprechende Analysedaten fossiler Vertreter dieser größten Ordnung der Säugetiere herzustellen. Kapitel 2 beschäftigt sich mit der Frage, ob die anomale Isotopensignatur troposphärischen Sauerstoffs als Indikator für diagenetische Alteration des Zahn- und Knochenmaterial von fossilen Säugern genutzt werden kann. Hierzu wurde die 3-O-Isotopie von Zahnschmelz, Dentin und in geringem Umfang auch Knochenmaterial von einzelnen Individuen känozoischer Nagetiere separat analysiert. Während alle Zahnschmelzproben eine deutliche Sauerstoffisotopenanomalie aufweisen, welche in einer Größenordnung liegt die für diagenetisch unalterierten Bioapatit kleiner Säugetiere zu erwarten wäre, zeigen alle Dentinproben eine deutlich niedrigere bis gar keine Anomalie, was auf Isotopenaustausch mit diagenetischen Fluiden hindeutet. In Kapitel 3 werden die Variationen der anomalen Isotopensignatur troposphärischen Sauerstoffs im Skelettmaterial von rezenten Säugetieren evaluiert. Dies geschieht anhand zweier voneinander unabhängiger Ansätze: 1. durch 3-O-Isotopenanalyse von rezentem Bioapatit und 2. durch ein detailliertes Massenbilanzmodell. Da der Anteil des veratmeten Luftsauerstoffs im Verhältnis zu den weiteren Sauerstoffquellen in erster Linie von der spezifischen metabolischen Rate abhängt, die weitgehend mit dem Körpergewicht skalierbar ist, wurden Arten aus einem möglichst großen Körpergewichtsbereich von wenigen g bis zu einigen tausend kg untersucht. Es zeigte sich, dass das anomale Isotopensignal mit sinkender Körpermasse zunimmt. Auf Basis der daraus gewonnenen Erkenntnisse wurde versucht die Magnitude der anomalen Sauerstoffisotopensignatur in der Troposphäre zu verschiedenen Zeitpunkten im Känozoikum durch 3-O-Isotopenanalyse von eozänem, oligozänem und miozänem Zahnschmelzmaterial von Nagetieren zu bestimmen um daraus Erkenntnisse über die entsprechenden CO2-Konzentrationen zu erhalten. Das theoretische Massenbilanzmodell stimmt gut mit den analytisch gewonnenen Daten überein, beide zeigen eine Vergrößerung der 3-O-Isotopenanomalie im Bioapatit mit sinkender Körpermasse. Die rekonstruierten CO2-Konzentrationen stimmen generell mit vorhandenen Daten diverser Proxies überein, jedoch erlaubt der assoziierte Fehler es nicht, CO2-Schwankungen im Bereich von wenigen 100 ppm aufzulösen. An der Grenze von Paläozän zu Eozän fand eine der einschneidendsten Umwelt- und Klimaveränderungen des Känozoikums statt, welche ihren Höhepunkt im sogenannten “Palaeocene Eocene Thermal Maximum” (PETM) hatte. Dieses war verbunden mit einer globalen negativen Kohlenstoffisotopenexkursion (CIE), deren Quelle bis heute kontrovers diskutiert wird. Kapitel 4 beschäftigt sich mit den Temperaturschwankungen und Veränderungen der CO2-Konzentration im Übergangsbereich dieser beiden Zeitalter. Dies geschieht anhand einer diesen Zeitabschnitt umspannenden Probenserie von Zahnschmelz der Säugetiergattung Ectocion aus dem Clarks Fork Basin (Wyoming, USA). Die rekonstruierten Temperaturschwankungen stimmen gut mit bereits vorhandenen Studien des 18O/16O Verhältnisses an biogenem Apatit aus diesem Zeitintervall überein. Die aus der 3-O-Isotopenzusammensetzung rekonstruierten CO2-Konzentration deuten darauf hin, dass auch während des Temperaturmaximums an der Paläozän-Eozän Grenze ein Wert von 1550 ppm nicht überschritten wurde, was auf die Dissoziierung von marinem Methanhydrat als Hauptquelle der CIE hinweist. Kapitel 5 untersucht die zwischenartlichen, innerartlichen und intraindividuellen Variationen der Karbonatsauerstoff-, Phosphatsauerstoff- und Kohlenstoffisotopie sieben verschiedener Nagetierarten anhand von Proben aus Eulengewöllen eines einzelnen Fundortes. Die Ergebnisse werden mit ähnlichen Studien an Großsäugern verglichen, und es werden Schlüsse zum Umgang mit Probenmaterial kleiner Säugetiere bei der Verwendung zur Paläoklimarekonstruktion mittels stabiler Isotope gezogen. Die Variabilität der Sauerstoff- und Kohlenstoffisotopie der untersuchten Zähne und Knochen ist nicht höher als die vieler Großsäuger, was die Relevanz der im Fossilbericht viel häufigeren Nagetiere für derartige Studien unterstützt. Jedoch sollte strikt darauf geachtet werden, dass auf Rezentmaterial basierende Bioapatit-Temperatur-Kalibrationen exakt auf dem gleichen Skelettelement beruhen welches auch als Fossilmaterial untersucht wird, da durch die unterschiedliche Mineralisierungsintervalle verschiedener Zähne und Knochen deutliche Unterschiede in den entsprechenden Isotopenzusammensetzungen, insbesondere in der des Sauerstoffs beobachtet werden konnten.

This thesis investigates the potential of the bivalve Arctica islandica (Linnaeus, 1767) from fjordic sites in NW Scotland for reconstructing past marine environmental /climatic variability. Using dendrochronological and sclerochronological techniques, six master chronologies were created which when compared show little common variability between the sites, indicating no common response to regional scale forcing. The chronologies were compared to local and regional scale SST and land based datasets, with no significant, time stable responses to climate found. It is clear the growth/climate response of A. islandica from these sites is complex, potentially due to the shallow nature of the sample sites, direct local drivers such as food availability and, potentially, anthropogenic activity in the region. Geochemical analyses of the shell material were undertaken to examine the timing and magnitude of the radiocarbon bomb-peak and the stable carbon isotope signature of the oceanic Suess Effect. The timing of the radiocarbon bomb-peak in Loch Etive does not appear to match previously published results from other marine locations and are a potentially serious challenge to the assumption that A. islandica GI are always annual features. Results comparing δ¹³C values and the age of the specimen when these values are incorporated into the shell material strongly indicate an ontogenetic control over δ¹³C, meaning the Suess Effect could not be effectively investigated. To take these ontogenetic influences into account it is suggested that any data from the juvenile period of shell life is not used. Analysis of shell biometrics and morphology indicate significant relationships between shell age and height and age and weight, however the errors for these are large (±78 years and ±80 years respectively). These results indicate that despite large errors shell height, as a predictor of age, has the potential to be used for in situ population studies.

Master of Science / Department of Geology / Matthew E. Brueseke / Low-[delta][superscript]1[superscript]8O silicic magmas are found in many volcanic provinces throughout the world, including the Snake River Plain-Yellowstone volcanic province (SRPY). The origin of SRPY low-[delta][superscript]1[superscript]8O silicic magmas is controversial, and centers on two disputed models: [1] a caldera collapse model that proposes reworking of the hydrothermally altered intra-caldera fill into the underlying silicic magma body, where each successive eruption lowers the [delta][superscript]1[superscript]8O of the magma eventually producing a low-[delta][superscript]1[superscript]8O magma and [2] melting previously hydrothermally altered mid-upper crust to form low-[delta][superscript]1[superscript]8O magmas. The mid-Miocene Santa Rosa-Calico volcanic field (SC) lies in northern Nevada. Brueseke and Hart (2008) described the geology and petrology of the SC, but did not deal with the [superscript]1[superscript]8O compositions of any locally sourced silicic magma. In the existing geological framework of the SC, this project aims to evaluate the two disputed models for low-[delta][superscript]1[superscript]8O silicic magma generation by analyzing the [delta][superscript]1[superscript]8O values of SC silicic eruptive products. Fifteen representative samples of locally erupted silicic units (e.g. ash-flow tuffs and lavas) were chosen for [superscript]1[superscript]8O analyses based on Sr-Nd-Pb isotope compositions, whole rock geochemistry, and field/temporal relationships. Each sample was crushed, sieved, and quartz and feldspar crystals were handpicked, described, and analyzed for their [superscript]1[superscript]8O compositions. Our results show that low-[delta][superscript]1[superscript]8O values exist in the SC and are limited to the youngest erupted silicic unit, the 15.8 to 15.4 Ma Cold Springs tuff, which was also the only unit erupted from a caldera. Cold Springs tuff [delta][superscript]1[superscript]8O feldspar values range from 2.36 to 4.05[per mil]; the unit is not quartz-bearing. Older silicic lavas that are not petrogenetically related to the Cold Springs tuff are characterized by normal [delta][superscript]1[superscript]8O feldspar values that range from 7.19 to 10.04[per mil]. Magma mixing models indicate that the source of the Cold Springs is a mixture of hydrothermally altered Granite Peak-Sawtooth granitoid and local mid-Miocene basalt, with an approximate range of [delta][superscript]1[superscript]8O values of 2-4[per mil], by fluids (with [delta][superscript]1[superscript]8O values ranging from -12[per mil] to + 7[per mil]) from the nearby hydrothermal system at Buckskin Mountain. This result follows the model by Boroughs et al. (2005) of prior alteration and melting, forming low-[delta][superscript]1[superscript]8O silicic magmas.

The peopling of the Americas, including the possibility that maritime peoples followed a coastal route from Northeast Asia into the New World, is a topic of major interest in archaeology. Paleocoastal sites on California`s Northern Channel Islands (NCI), dating between ~13,000 and 8000 years ago, may support this coastal migration theory. Until recently, however, we knew little about Paleocoastal technologies, settlement, and lifeways on the islands. Combining traditional archaeological approaches with experimental and archaeometric techniques, I examine Paleocoastal settlement and resource use on San Miguel and Santa Rosa islands. Recently discovered Paleocoastal sites have produced sophisticated chipped stone technologies, with bifacially-flaked points and crescents of extraordinary craftsmanship. Exploring lithic raw material procurement strategies, I demonstrate a Paleocoastal preference for island cherts from sources centered on western Santarosae. Using experimental and archaeometric techniques, I show that Paleocoastal peoples systematically employed heat-treatment to manufacture finely crafted bifaces from island cherts. Using stable oxygen isotope (δ18O) analyses of marine shells from Paleocoastal sites, I examine paleo-sea surface temperatures, seasonality of shellfish collecting, and human sedentism. Evaluating whether such occupations were seasonal or year-round, I tested different sampling strategies for California mussel shells, showing that a method used by many California archaeologists provides erroneous seasonality interpretations for ~35 percent of sampled shells. Using a more intensive sampling strategy, I demonstrate that some Paleocoastal sites were used seasonally, but three substantial middens dating to 8200, 9000, and 10,000 cal BP produced evidence for shell harvesting during all four seasons. This suggests that the NCI were occupied more or less permanently and year-round by at least 10,000 years ago. My research suggests that Paleocoastal peoples had a strong commitment to maritime and island lifeways starting at least 12,000 years ago. From that time until ~8000 years ago, Paleocoastal peoples relied primarily on island resources despite their close proximity to the mainland. The presence of a relatively large, permanent, and distinctive Paleocoastal population on the NCI may also support the coastal migration theory and an even deeper antiquity of human settlement and sedentism on the NCI. This dissertation includes previously published and unpublished co-authored material.

The first bimonthly resolved, paired δ18O and Sr/Ca time series from the slow-growing, tropical western Atlantic coral, Siderastrea siderea, from the Dry Tortugas, Florida has been generated and used to document that robust proxy climate records can be produced from this heretofore underutilized massive coral. The coral time series contains a 20-year long calibration window (1973-1992) for both δ18O and Sr/Ca and a 73-year long verification window (1900-1972) for Sr/Ca. These time series permits both the quantification of the relationship between coral δ18O-SST and Sr/Ca-SST using an augmented, 1° x 1° gridded SST record and the assessment of the stability of the proxy relationships over time. Both coral geochemical records are highly correlated with the augmented instrumental SST record through the calibration period and Sr/Ca remains highly correlated through the verification period both at the bimonthly (r = -0.97) and annual average level (r = -0.72). Additionally, both coral δ18O and Sr/Ca are highly reproducible within the same core, and Sr/Ca exhibits no extension-related vital effects. Sr/Ca-SST anomalies are also significantly correlated to the augmented SST anomalies, despite the removal of the serial autocorrelation. The skill of this proxy demonstrates its potential as a continuously growing, long-lived recorder of climate variability for the tropical Atlantic and Intra-American Seas. The relatively slow extension rate of the coral (~5 mm yr-1 during the 20th century) also suggests the potential for long records of climate variability (~200 years) of the region to be extracted from even modest-sized colonies (~1 m in height). The results of this study are important because relatively few century-long, sub-annually resolved time series of climate variability from massive Atlantic corals have been published, despite the significance of the tropical Atlantic climate modes of variability.

Sclerochronology was conducted on the pedicle valves of four Sakmarian-age brachiopods (Squamaria moorei) to constrain climate model predictions of temperature seasonality along western equatorial Pangaea (WEP). The brachiopods are from a Lower Permian section within the Robledo Mountains, NM, and they reveal seasonal trends of δ18O and temperature for that interval that suggest global warming and moderation of seasonality. Elemental and SEM analyses verified the specimens were well preserved. δ18O profiles show a relatively rapid and consistent two-year growth rate corresponding to the organism's juvenile stage, followed by a slower, seasonal growth rate corresponding to the organism's sexually mature stage typical of most organismal growth. Their initial two-year cycles show consistent, high-amplitude profiles that captured virtually complete records of annual δ18O values, and these profiles were used for seasonality interpretations. The specimen from the stratigraphically lowest layer shows δ18O values varying from -4.26 to -2.17 minimum winter temperatures (MWT) and maximum summer temperatures (MST) of 25.2C and 35.7C, respectively; and a seasonal temperature variation ΔTs of 10.0C. The overlying horizon yielded two specimens showing δ18O values ranging from a minimum of -4.54 to a maximum of -2.79; MWT ranging from 28.2 to 29.6C; MST ranging from 34.9 to 37.2C; and ΔTs ranging from 6.7 to 7.6C. The uppermost layer yielded a specimen that shows δ18O values ranging from -4.49 to -3.03; MWT of 31.3C; MST of 37.0C; and ΔTs of 5.7C. The specimens show overall high seasonality for an equatorial regime, but the general trend shows increasing winter temperatures and a moderation of seasonality. The data supports climate-model predictions for the Permian of more equable temperatures, higher winter temperatures, and decreased seasonality. Three numerical climate models of Permian temperatures were evaluated against the brachiopod data, and their model predictions for ΔTs along WEP range from as high as 10C to as low as C. The models were supported somewhat by the independently derived temperature proxy data measured in this study.

Monthly δ18O and Sr/Ca records generated from modern and fossil corals from Southwestern Pacific Ocean sites in the Republic of Vanuatu are used to assess the differences in mean climate state, seasonality, and interannual variability between a glacial and interglacial period. The modern coral contains a well-defined annual signal in δ18O and Sr/Ca. The top 40 cm of the coral used in this study has a mean δ18O value of -4.99+/-0.13%VPDB (2σ) and a mean Sr/Ca value of 8.691+/-0.015mmol/mol (2σ). El Nino-Southern Oscillation (ENSO) events are characterized by positive δ18O and Sr/Ca anomalies, consistent with cooler temperatures and reduced rainfall that typifies ENSO at Vanuatu. The ~12cm long fossil coral is dated to 346 ka + 25, - 9, based on uranium-series analysis and stratigraphic forward modeling, indicating that the fossil coral grew during MIS10 - a glacial period. X-ray diffraction, petrographic inspection, SEM analysis, and geochemical considerations indicate excellent preservation. The mean δ18O value is enriched by 0.74%, and the mean Sr/Ca value is equivalent, compared to the modern coral. Mathematical modeling of Pleistocene mean SST and SSS results in temperature estimates up to ~2˚C warmer and salinity up to ~2 psu saltier than present-day conditions, if seawater Sr/Ca were 1-2% higher in MIS10. Our fossil coral data and modeling results preclude colder SST and lower SSS at Vanuatu during MIS10. Accurate estimates of past values of seawater Sr/Ca remain the largest obstacle to accurately reconstructing past tropical SST using pristine fossil corals. The fossil coral Sr/Ca annual range is similar to the modern range, indicating that seasonal SST ranges were similar, whereas the δ18O annual range is about half that of the modern coral, indicating weaker past seasonal salinity variations. The reduced seasonal SSS variations and increased SSTs near Vanuatu are interpreted as evidence that the SPCZ was displaced from its present location while the fossil coral lived. The geochemical response to El Niño events in the modern coral is observed twice in the fossil coral record, indicating that ENSO-like processes are not unique to interglacial time periods, but characterize the tropical Pacific at least back to MIS 10.

We test the fidelity of shallow-water gastropod skeletons as multi-proxy archives of seasonal paleo-environmental change by performing isotopic and trace-metal analyses on specimens of Conus ermineus from the Gulf of Mexico. Four adult specimens were collected from Stetson Bank in the Flower Garden Banks National Marine Sanctuary during the summer of 2002. Shell samples were milled along axes of growth to produce time-series profiles spanning up to eight years. We corrected the profiles for growth rate effects and compared the tuned results with in situ temperature and salinity records at the reef surface and temperature profiles from nearby surface buoys. Examination of sample densities in δ18O cycles shows that shell growth is faster during summers and slower during winters. Tuning the profiles versus time yields δ18O values that co-vary closely with seasonal temperatures to a high degree of coherency (R2 = 0.84). The δ13C profiles show cyclic variation modified by ontogenetic decreases in δ13C. These ontogenetic trends are attributable to decreasing metabolic efficiency, while seasonal cycles reflect hydrographic changes in the gastropods’ habitat. Salinity and δ13C of dissolved inorganic carbon show a strong correlation at Stetson Bank (R2 = 0.80), and early summer shell δ13C minima coincide with local salinity minima during times of peak river discharge. The terminations of these δ13C minima occur during annual upcoast reversals of shelf currents in this area. These effects are augmented by summer stratification and productivity minima that further decrease seawater δ13C. Sr/Ca ratios increase through ontogeny, most likely due to decreasing metabolic efficiency. However, seasonal variations in Sr/Ca profiles show strong similarity with δ18O profiles, confirming the temperature dependence of Sr/Ca and minimal influence of salinity on shell δ18O at Stetson Bank. The results of this study show that tuned δ18O and Sr/Ca profiles can be used to reconstruct seasonal paleotemperatures. Carbon isotope profiles and environmental data also demonstrate the utility of Conus δ13C as a proxy for freshwater flux and shelf circulation.