Earth and Planetary Sciences - Student Works

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    Carbonate sedimentology of coral reefs in Sumba Island, Indonesia
    (2022) Ramos, Cedrick; Corlett, Hilary
    The Island of Sumba, Indonesia, comprises several reef terraces formed by changing global sea levels and episodic tectonic activity. Volcanic-derived sediment has been found to have been incorporated into reef fabrics without impacting coral growth. The uninterrupted reef growth shows a conflicting theory that coral reefs do not survive under significant clastic input. Continuous reef growth has been documented in this region known as the Coral Triangle. However, it is unclear whether intervals of increased clastic content affect coral growth strategies or whether the immature nature of the volcaniclastic sediment (larger and angular grain) explains why clastic input does not choke corals. This study employs various thin sections from fossil reefs (late-Pleistocene) to document and characterize the sediment’s size and circularity, which is a measure of sediment maturity. The study involves imaging analysis by taking images of each thin section. The thin sections have all been stained with Alizarin red, a stain that only turns calcite or aragonite grains a shade of red, and all other minerals remain unstained. Then, the images were colour indexed to black and white, with clastic grain appearing as white. The images underwent thresholding to isolate the white grains to measure their circularity and sizes. It was found that the grains of the sediments are sand size and angular, which means that the grains only have some transported involved, but they did not deposit far away from their source. A range of grain sizes in these sections have revealed that some of the grains detected are small enough to enter corallites and pores in the coral skeleton, while others are much larger and would not impact the coral growth.
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    Petrography and Raman spectroscopy of diogenites, Northwest Africa 10268 and 7464
    (2021) Aizon, Jannah; Walton, Erin L.
    The study of meteorites is crucial to understanding the geological evolution of our early solar system. In this study, we observe optical and chemical properties of two diogenite meteorites (Northwest Africa 7464 and 10268) that originated from the second-largest asteroid, 4 Vesta. By studying the mechanical deformation and transformation features of feldspar, olivine and pyroxene grains within the samples, we are able to constrain the shock stage of each meteorite. Northwest Africa 7464 and 10268 were both observed using a scanning electron microscope, an energy dispersive X-ray spectrometer, an electron microprobe, a petrographic microscope and a Raman spectrometer. Northwest Africa 7464 exhibits weak mosaicism and planar fractures in pyroxene, as well as, undulatory extinction and planar fractures in olivine. These features suggest a weakly shocked S3 meteorite consistent with a shock pressure of between 5-15 GPa. Northwest Africa 10268 contains opaque shock veins associated with the diaplectic plagioclase glass, maskelynite. This host rock exhibits strong mosaicism and undulatory extinction in pyroxene, as well as, twinning in crystalline feldspar. These features are consistent with a moderately shocked S4 meteorite, experiencing a shock pressure of between 15-30 GPa. These results give insight on shock pressure and temperature conditions that occur on 4 Vesta.
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    Petrography and Raman spectroscopy of diogenites, Northwest Africa 10268 and 7464
    (2021) Aizon, Jannah; Walton, Erin L.
    The study of meteorites is crucial to understanding the geological evolution of our early solar system. In this study, we observe optical and chemical properties of two diogenite meteorites (Northwest Africa 7464 and 10268) that originated from the second-largest asteroid, 4 Vesta. By studying the mechanical deformation and transformation features of feldspar, olivine and pyroxene grains within the samples, we are able to constrain the shock stage of each meteorite. Northwest Africa 7464 and 10268 were both observed using a scanning electron microscope, an energy dispersive X-ray spectrometer, an electron microprobe, a petrographic microscope and a Raman spectrometer. Northwest Africa 7464 exhibits weak mosaicism and planar fractures in pyroxene, as well as, undulatory extinction and planar fractures in olivine. These features suggest a weakly shocked S3 meteorite consistent with a shock pressure of between 5-15 GPa. Northwest Africa 10268 contains opaque shock veins associated with the diaplectic plagioclase glass, maskelynite. This host rock exhibits strong mosaicism and undulatory extinction in pyroxene, as well as, twinning in crystalline feldspar. These features are consistent with a moderately shocked S4 meteorite, experiencing a shock pressure of between 15-30 GPa. These results give insight on shock pressure and temperature conditions that occur on 4 Vesta.
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    A revised shock history for the youngest unbrecciated lunar basalt - northwest Africa 032
    (2020) Mijajlovic, Tatiana; Xi Xue; Walton, Erin L.
    Northwest Africa (NWA) 032 is the youngest radio metrically dated mare basalt, with concordant Rb-Sr and Sm-Ndages of 2.947 ± 0.016 Ga and 2.931 ± 0.092, respectively [1]. Measurement of the cosmogenic nuclides present in NWA 032 suggest an Earth-Moon transfer age of 0.5Ma, typical of lunar meteorites [2]. NWA 032 is an unbrecciate dolivine-pyroxene-phyric basalt, with olivine, pyroxene and plagioclase as major minerals (Fig.1). A previous description of shock effects in NWA 032 allowed for a shock pressure estimate of ~4060 GPa [2]; however, the shock state of plagioclase feldspar (shock-amorphized vs crystalline) was inconclusive, owing to the fine grain size of this mineral (≤1μm). The purpose of our study is to characterize the shock deformation and transformation effects in NWA 032 using field emission scanning electron microscopy (FESEM) and micro-Raman spectroscopy, focusing on the structural state of feldspar, shock deformation recorded in igneous olivine and pyroxene, as well as characterizing the crystallization products of shock melting. The latter have been demonstrated as useful criteria to evaluate shock conditions [3]. Our results more tightly constrain the shock history experienced by NWA 032.
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    Locating buried ruins in the British Isles
    (2019) Shaigec, Steffen; McKeown, Nancy
    During the summer of 2018, the British Isles experienced one of the hottest summers on record resulting in the appearance of crop markings which may indicate the presence of buried ruins. This study investigates the capabilities of satellite imagery and LiDAR-based digital terrain models for detecting new locations of ancient subsurface ruins without relying on extreme weather events. Several sites will be compared to determine if there are consistent, reliable criteria that indicate the presence of subsurface ruins.