Trees are excellent archives of paleoclimatic information. They can preserve records of past temperature, precipitation, drought, and extreme weather events. The focus of this dissertation is to use tree ring width, carbon isotopes, oxygen isotopes from multiple trees to characterize climate variability and the tree-ring tropical cyclone record. Living longleaf pine trees (Pinus palustris Mill.) were sampled from the Turkey Creek and Big Sandy Creek Units at Big Thicket National Preserve, Texas. Annual tree rings were measured and assigned yearly calendar dates. The latewood portion of each annual ring was shaved with a scalpel, and alpha-cellulose was extracted for carbon and oxygen isotopic analyses. Oxygen isotope records from both sites indicated that individual trees growing in the same stands could vary significantly from each other. The heterogeneity of tree-ring oxygen isotopes was driven by variability in the oxygen isotope composition of soil moisture used for tree growth. Average oxygen isotope chronologies from both sites yielded significant correlations with regional fall (August–October) precipitation (Turkey Creek r = –0.71, p < 0.001; Big Sandy Creek r = –0.62, p < 0.001) and z-index (Turkey Creek r = –0.69, p < 0.001; Big Sandy Creek r = –0.63, p < 0.001). An average carbon isotope chronology from Big Sandy Creek was also significantly correlated with fall precipitation (r = – 0.59, p < 0.001) and z-index (r = –0.57, p < 0.001). Individual trees at both sites did not always record similar tropical cyclone events. A composite tropical cyclone chronology from Turkey Creek identified 58% (7 of 12) of the storms known to have produced rainfall at the site. The Big Sandy Creek composite chronology identified 65% (8 of 12) known storms. Wetter than average years that followed dry years were found to mimic the oxygen isotopic signal associated with tropical cyclone events. Additionally, dry years masked the tropical cyclone signal so that it could not be recorded in tree rings.

The flurry of activity involved in the scientific study of Mars has resulted in multiple new data sets from several missions (Mars Global Surveyor (MGS), Mars Odyssey (MO), Mars Exploration Rovers (MER), Mars Reconnaissance Orbiter (MRO), and Mars Express) that provide information for unlocking the planet’s geologic and climatic history. This three part study utilized both orbital data and laboratory experiments to examine Mars for morphologic and mineralogic evidence of aqueous activity and magmatic evolution. The first study examined Gusev Crater, landing site for the Spirit MER rover. This work began during final landing site selection and was published just prior to Spirit’s January 2004 landing. In this work, I examined the paradigm that Gusev once held a paleolake and that it contains detrital sediment from the northern highlands. Analyses involved using the most current data then available. I produced thermophysical, morphological, and surface unit maps showing the spatial distribution and stratigraphic relationships of materials on the floor of Gusev. Orbital analyses found no unambiguous evidence of paleolake deposits. This study offered alternative hypotheses explaining floor units, one of which, volcanic deposition, has since been verified by Spirit on the ground. The second and third studies address our ability to accurately derive plagioclase compositions on Mars and to use thermal emission spectroscopy to map vii the distribution of plagioclase compositions on Mars. Plagioclase is the most abundant mineral in the martian crust and may provide information about the igneous evolution and subsequent alteration of the Martian surface. The second study focuses on mixtures more complex in nature than the two-component (composition) plagioclase sand mixtures used in previous work. Linear deconvolutions of laboratory spectra from mixtures involving additional components and phases were used to calculate average plagioclase compositions whose accuracies were found to be comparable to previous studies. The final project carried results from previous laboratory studies one step further to map the global distribution of plagioclase compositions on Mars. Maps reveal a world dominated by labradorite and bytownite, with lesser amounts of other plagioclase. Localized variations are difficult to discern at the scale of individual MGS Thermal Emission Spectrometer (TES) observations.

The Dawn mission, which launched in September 2007, will orbit and analyze two of the largest asteroids, 4 Vesta and 1 Ceres. These small, proto-planetary bodies retain a record of the conditions and processes that occurred in the early history of the Solar System, and, as such, provide us with a tool to understand its formation and evolution. Additional information can also be gleaned from the meteorite samples derived from such objects. This dissertation aims to increase understanding of the formation of the basaltic crust of the asteroid Vesta, and the lithologic variety that exists within it, by studying the eucrite meteorites, believed to originate from it. In order for us to be able to identify different units on the surface of Vesta, we must first understand the relationship that exists between the petrology of the samples and their spectral characteristics, which will be measured by the VIR (Visible Infrared) instrument aboard Dawn. The first part of this dissertation details an in-depth study into the petrology of the unbrecciated eucrites, focusing on those characteristics that impact the spectra, e.g. mineral chemistries and modal abundances. Select well-characterized unbrecciated eucrites from the petrologic study were then chosen for spectral work. Visible near-infrared (0.3 – 2.5 μm) spectra were collected and the amount of petrologic information that could be extracted from the spectra alone was assessed. We were able to distinguish the spectra of basaltic versus cumulate eucrites, as well as those samples that underwent slow- versus fast cooling and early- versus late-crystallization. This indicates that we may be able to map petrologic units using Dawn and determine the processes that occurred to form them. Dawn is scheduled to reach Vesta in 2011; however, the Vestoids, a group of asteroids believed to be from Vesta, offer us the opportunity to utilize the combined petrologic-spectral data set now. The spectra of 15 Vestoids were examined and compared to spectra for the howardite, eucrite, and diogenite meteorites, of which Vesta is believed to be the parent body. The Vestoids indicate that both large-scale (>7 km) homogeneous and small-scale (<1 km) heterogeneous units exist on the surface of Vesta.

The ordinary chondrites, the most abundant group of meteorites, are divided into three chemical groups (H, L, and LL), which are distinguished based on variations in bulk composition and iron content. Although ordinary chondrites are relatively abundant, our understanding of their formation has been hampered by an inability to accurately measure the abundances of minerals that they contain. Here I use power x-ray diffraction (XRD) to quantify the modal abundances of 48 unbrecciated ordinary chondrite falls, which represent the complete petrologic range of equilibrated ordinary chondrites (types 4-6). Although the degree of metamorphism varies within each ordinary chondrite group, many details regarding the geochemical and thermal changes that take place during this process are not well understood. Using XRD-measured modal mineral abundances and chemical analyses, we evaluate the redox state and peak metamorphic temperatures in ordinary chondrite parent bodies in order to develop quantitative thermal evolution models of ordinary chondrite parent asteroids. Modal abundances and mineral compositions measured in this study indicate that progressive oxidation of the ordinary chondrites likely occurred during metamorphism. Results also suggest that plagioclase crystallizes early in the metamorphic sequence, indicating that peak temperatures derived using the two-pyroxene geothermometer are more accurate than those calculated using the plagioclase geothermometer. I also utilize ordinary chondrite modal abundances to develop new calibrations for deriving mineralogy from meteorite and asteroid spectra. Most previous studies examining the mineralogical characteristics of VISNIR asteroid spectra have focused on olivine and pyroxene proportions in single-pyroxene mixtures; therefore, current calibrations for deriving composition mineral abundances may be poorly suited for asteroids containing more than one pyroxene. It is important that calibrations are correct, because mineral abundances derived from visible/near-infrared (VISNIR) spectra are used to classify asteroids, identify meteorite parent bodies, and understand the structure of the asteroid belt. Mineral abundances derived using my calibrations correlate well with measured data for all ordinary chondrites groups, and also appear to be valid for other meteorites and asteroids with mineral abundances and chemistries similar to those of the ordinary chondrites.

A recent increase in hurricane activity has put coastal populations at risk. To better understand hurricane activity, it is necessary to look beyond the modern instrumental record, using proxy records to establish modes of past variability. The utility of a newly developed tree-ring oxygen isotope proxy is further assessed. I present oxygen isotope time series from three sites: Francis Marion and Sandy Island, South Carolina and Eglin Air Force Base, Florida. Proxy results are verified against the instrumental record of hurricane occurrence. The sites record similar percentages (45% for Francis Marion and Sandy Island, 63% for Eglin Air Force Base) of hurricanes that tracked within 200 km of the sites. Potential reasons for missing storms include initial storm water composition, lack of precipitation, or drought. In Florida, a longer record was developed (1710–1950). For the period 1850– 1950, the proxy captured 24% of hurricane events. This decrease is similar to the Valdosta, Georgia study and is attributed to changes in the Pacific Decadal Oscillation. At both sites, during cool phase PDO, the number of storms recorded by the proxy increases, but the percentage of activity recorded decreases. The identification of periods (1710– 1720, 1760–1780, 1810–1830, and 1840–1850) of multiple negative anomalies inferred to be hurricane events at both sites provide evidence for short increases in hurricane activity that match to periods of increased activity in the Caribbean and the Lesser Antilles. The data show that hurricane activity fluctuates over time and do not support an increasing trend in hurricane frequency. Spectral and wavelet analysis of the oxygen isotope time series from these sites reveal frequencies similar to the Quasi-biennial Oscillation, the El-Niño Southern Oscillation, and the North Atlantic Oscillation. Major shifts in the oxygen isotope data in the 1960s in both Florida and South Carolina are concurrent with climate shifts observed globally that are linked to the Atlantic Multi-decadal Oscillation and/or the Pacific Decadal Oscillation. Spectral analysis of the Florida time series also reveals 11 and 22– year cycles that are coincident with sunspot and Hale solar cycles.

Impact cratering is ubiquitous, energetic and fundamental geologic process acting on the solid planetary bodies. As a consequence, craters provide planetary scientists with useful information regarding the surface and subsurface properties of planetary bodies. Specific mineral and lithologic compositions can be ascertained via craters in two ways: 1) by the remote sensing of crater-exposed subsurface materials, or 2) by studying the differentiated meteorites (e.g., lunar, Martian, etc.) ejected from their surfaces by highenergy impacts under specific conditions. As a proof of concept for subsurface-crater mapping, remote sensing techniques were applied to a terrestrial impact structure. Visible-near infrared (VNIR), short-wavelength infrared (SWIR), and thermal infrared (TIR) data were used to map the subsurface geology of a portion of Devon Island (High Canadian Arctic) via the impact-exposed subsurface lithologies of the 23-kilometer diameter Haughton impact structure. The results from the “blind” remote sensing of Haughton suggest that the spectral and lithologic mapping techniques used in this study can also be used to understand subsurface geology of Mars. TIR images from Thermal Emission Imaging System (THEMIS) onboard Mars Odyssey were used in a similar fashion to spectrally map craters within the Isidis basin on Mars. Complementary hyperspectral information from the Thermal Emission Spectrometer (TES) allowed mineral and litho-type compositional determinations, albeit at a much lower spatial resolution. An olivine-rich basaltic unit mapped at the surface and was linked with a subsurface occurrence via exposure from impact craters occurring within the basin. These two studies (Chapters 2 and 3) demonstrate that, in conjunction with surface mapping, impact craters provide a natural “window” for understanding the stratigraphy and petrogenesis of planetary crusts. In another project presented here (Chapter 4), rayed crater systems on Mars, which are preferentially found on the younger lava plains, has led to the hypothesis that rayed craters may have been the launch sites for the Martian meteorites recovered on Earth. This hypothesis is supported by morphologic and thermophysical evidence, as well as the most current modeling of Martian meteorite ejection.

Detailed geologic mapping, SHRIMP U-Pb zircon geochronology, geochemistry, petrology, and structural and kinematic analyses were applied to decipher the structure, tectonic heredity, and Paleozoic accretionary history of suspect terranes of the southern Appalachian Blue Ridge (BR) and Inner Piedmont (IP). Detailed geologic mapping in the Waynesville and Sam Knob 7.5-minute quadrangles recognized the Great Balsam Mountains window cored by sillimanite I and II zone Dahlonega gold belt rocks, overthrust by migmatitic biotite gneiss of the Cartoogechaye terrane to the northwest, and migmatitic Tallulah Falls Formation of the Tugaloo terrane to the southeast. Suspect terranes of the BR and IP consist of peri-Laurentian and mixed Laurentian and peri- Gondwanan heredities and were accreted to the Laurentian margin during the Taconian, 465–450 Ma, and Neoacadian, 365–340 Ma, orogenies. Detrital zircon populations of 1.3–0.9 Ga, 1.5–1.3 Ga, and 750–700 Ma from the Cartoogechaye, Cowrock, Dahlonega gold belt, and Tugaloo terranes indicate a dominantly Laurentian provenance. Minor Paleoproterozoic populations in these terranes suggest input from distal terranes of the Laurentian mid-continent or the Amazonian craton. Detrital Paleozoic zircons, 460–430 Ma, occur only in samples from the Cat Square terrane and Smith River allochthon. Ordovician and 600–500 Ma detrital zircons from the Cat Square terrane document the first occurrence of peri-Gondwanan material deposited in a convergent setting between Laurentia and the approaching Carolina superterrane during the Late Silurian to Early Devonian. Palinspastic reconstruction of the Cat Square basin suggests a paleogeographic location in the Pennsylvania embayment and links deformation in the crystalline core with progradation of the Devonian clastic wedge. Metamorphic zircons from central BR terranes yield U-Pb ages of 465–450 Ma, and delimit accretion to the Laurentian margin and metamorphism to amphibolite and granulite facies during the Taconian orogeny. U-Pb ages of metamorphic zircons from the IP yield ages of 392–344 Ma corresponding to upper amphibolite facies metamorphism associated with the Devonian–Mississippian collision of the Carolina superterrane during the Neoacadian orogeny. The IP and parts of the eastern BR flowed west and southwest out from beneath the overthrust Carolina superterrane as an orogenic channel.

Purpose and Scope of the Investigation: Several workers, as indicated in the following section, have commented upon the geology of the Flag Pond Quadrangle, but none have mapped or studied the area in detail--nor indeed, much of the adjacent region. Consequently, the purpose of this investigation is to obtain a comprehensive picture of the geology of the quadrangle. The geology of the quadrangle is divisible into two natural units or parts, each with problems unique unto itself. The first of these units is the crystalline complex, the second is the sedimentary sequence which rests upon the crystalline rocks. The purpose of this study with regard to the crystalline group is first to determine the character of these rocks and to delineate mappable units within them. Secondly, an attempt is made to establish the chronological and structural relationships of the mappable units. Finally tentative conclusions as to the origin and history of the crystalline complex are presented. The study of the crystalline rocks of the area is based exclusively on field examination and thin-section analysis. Laboratory investigations of the crystalline rocks are beyond the scope of this investigation. The sedimentary rocks have been studied, subdivided and described by various workers at several localities outside the Flag Pond area. This study is concerned with the stratigraphy of the Flag Pond area, the character and distribution of the formations, their relationship to other rock units, and, finally, their geologic history. A few representative thin sections of each formation were studied. (Large 24 MB file because of 4 color map plates at the end.)

EETA79001 is a unique shergottite composed of two mafic lithologies (termed LithA and LithB) that are separated by an igneous contact. Both lithologies have basaltic compositions; however, LithA contains megacrysts of olivine, orthopyroxenes, and chromite whereas LithB does not; also, LithA is finer-grained than LithB. Currently, the literature is in disagreement regarding the formation of this unique meteorite, especially regarding LithA. Different formational theories (e.g. fractional crystallization, magma mixing, assimilation, and impact melting) have their own constraints (chemical, thermal, or petrographic). This study uses petrographic observations combined with major- and trace- element compositions within minerals to investigate the petrogenesis of LithA. Previous formational theories are addressed and a new model is proposed. The groundmass composition of LithA is important in explaining the relationship between megacrysts and the groundmass. Previous estimates do not consider weighted compositional averages or overgrowths on olivine megacrysts. In this study, a new estimate of the LithA groundmass composition is obtained using weighted averages of zoned minerals (major-element), and includes the overgrowth rims on megacrysts. Here, I introduce a new LithA formational model that involves the mixing of cold megacrysts with magma. This hybrid model suggests that the interaction of the megacrysts and magma altered the heat balance and changed the crystallization sequence, as evidenced by the major-element trend in pyroxenes and the finer grain size of the LithA groundmass. The megacryst overgrowths and groundmass then crystallized, and was later followed by the removal of the late-stage fractionated melt (liquid ~Mg# 20). This new model would explain the formation of the overgrowths and avoids the heat constraints associated with magma mixing and assimilation. However, a short-coming of this theory lies in the necessity for the late-stage removal of the last ~10% of the melt, necessary to modify the original magma composition to that of the observed LithA groundmass composition.

New field and analytical data collected in the eastern Blue Ridge (EBR) of southwestern North Carolina reveal a complex, polyphase thermotectonic history, and delimit the timing of previously unrecognized orogenic pulses in a portion of the southern Appalachian orogenic core. Detailed geologic mapping of the Glenville and Big Ridge 7.5’ quadrangles delineated the location of the Chattahoochee fault, a tectonic boundary separating the western Tugaloo terrane from distinct central Blue Ridge terranes. Zircon geochronologic data for two EBR granitoids in the map area indicate emplacement occurred at ~335 Ma, making these plutons among the youngest recognized in the EBR. Bulk-rock geochemical analyses of the Walnut Creek pluton reveal similarities with the Whiteside Granite, and strongly suggest similar source regions for Ordovician and Mississippian trondhjemitic magmas. Field relationships and Al-in-hornblende barometry suggest intrusion into mid-crustal levels (~7 kbar) pre- to synkinematic with regional D3 deformation. Host rock porphyroblast textures and microstructures indicate distinct tectonometamorphic histories for Cartoogechaye and Tugaloo terrane samples, providing support for distinct P–T–t–D paths. Cartoogechaye terrane samples reached significantly higher temperatures and pressures during Taconian orogenesis. Mineral assemblages and textures suggest pressures >9 kbar(?), and peak sillimanite II zone temperatures (≥750 ºC). Tugaloo terrane samples in the southern Big Ridge quadrangle preserve pristine Taconian M2 mineral assemblages. Multi-equilibrium calculations using balanced, linearly independent reactions performed on a metapelite yielded near-peak metamorphic conditions of 703 ± 30 ºC and 9.0 ± 1.2 kbar (2 sigma). These conditions accompanied intrusion of the Ordovician Whiteside Granite. A distinct thermal overprint is evident from metapelite samples collected ≤1 km from the Mississippian Rabun and Walnut Creek plutons. Evidence consists of psuedomorphs of muscovite ± sillimanite after staurolite at distances <0.5 km from the intrusions, and post-kinematic staurolite + kyanite porphyroblasts that cross cut all fabric at distances of ≤1 km. Plagioclase deformation mechanisms interpreted to have accommodated strain during shearing along the Chattahoochee fault include climb-accommodated dislocation glide and grain-boundary migration recrystallization. These microstructures are consistent with deformation temperatures >600 ºC. Geochemical signatures, xenocrystic zircons, and high–T shearing together strongly suggest Ordovician juxtaposition of the Tugaloo and central Blue Ridge terranes.