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Subject: search.filters.subject.Cretaceous/Tertiary boundary

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    Gold and palladium as indicators of an extraterrestrial component in the Cetaceous/Tertiary boundary layer at Woodside Creek and Chancet Quarry, Marlborough, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Earth Sciences at Massey University
    (Massey University, 1998) Cook, Andrew William
    It is widely believed that a large meteorite approximately 10 km in diameter impacted Earth at the termination of the Cretaceous Period with cosmic velocity, vaporising itself, along with a greater mass of the terrestrial target rocks into a cloud of hot rock vapour. The vapour cloud condensed into particles of sand to clay size at high altitude before returning to Earth to form a worldwide layer marking the Cretaceous/Tertiary boundary. Chemical evidence from this boundary layer suggests that the impactor was a chondritic meteorite, enriched in the platinum group elements compared to the Earth's crust. An enrichment of these elements above their background crustal abundances to approximately 0.1 of the chondritic abundance has been observed in a number of Cretaceous/Tertiary boundary layers worldwide. Iridium is the platinum group element traditionally used as an indicator of the extraterrestrial component (ETC) in likely impact layers due to its rarity in the Earth's crust and low detection limits possible using neutron activation analysis methods. Neutron activation analysis is however expensive and requires specialist facilities, this thesis proposes that the elements gold and palladium can also be used to indicate the ETC in the Cretaceous/Tertiary boundary layer. Samples from two Cretaceous/Tertiary boundary sites, Woodside Creek and Chancet Quarry, were analysed for gold and palladium using graphite furnace atomic absorption spectrometry. A strong correlation was found between iridium, gold, and palladium abundances at these sites, with all showing enrichment at precisely the Cretaceous/Tertiary boundary in proportion to iridium, indicating a common origin for all three elements. Gold showed almost precisely the expected 0.1 of its chondritic abundance in the clay size fraction at both Woodside Creek and Chancet Quarry (15 ng/g). Palladium showed exactly 0.1 of its chondritic abundance at the Chancet Quarry boundary with 53 ng/g. Gold abundances on the boundary at Woodside Creek (55 ng/g) and Chancet Quarry (44 ng/g) showed excellent agreement with published values as did the palladium result for Woodside Creek (22 ng/g).
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    The analytical geochemistry of platinum group metals in cretaceous/tertiary boundary clays : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in chemistry at Massey University
    (Massey University, 1991) Wilson, Shane Malcolm
    The Cretaceous tertiary boundary controversy is discussed. The importance of the platinum group metals (PGM) as markers of extraterrestrial material in sediments is explained. The use of inductively coupled plasma source mass spectroscopy (ICP-MS), and graphite furnace atomic absorption spectroscopy (GF-AAS), to determine PGM in geological materials, was investigated. Both techniques require the analyte to be substantially separated from the geological matrix before instrumental analysis is performed. Separation schemes involving fire-assay, ion exchange chromatography, solvent extraction, and coprecipitation, were investigated. A standard ore (PTC- 1) was successfully analysed for Rh and Pd using a separation scheme involving Te coprecipitation followed by dissolution and determination by ICP- MS . The same ore was successfully analysed for Pd using GF-AAS after a separation procedure involving solvent extraction of a Pd-ammonium pyrrolidine dithiocarbamate complex. Sedimentary rock samples were collected from a newly discovered K/T boundary site (Flaxbourne River) in New Zealand. Determinations of Pd in Flaxbourne River sediments were made using GF-AAS after matrix separation using solvent extraction. Elevated levels of Pd at the K/T boundary were found contiguous with elevated levels of Ir. Besides these PGM, a further twenty elements were determined in Flaxbourne River K/T boundary sediments. The results of this geochemical survey are discussed with respect to the impact and volcanism theories (theories which seek to explain the palaeontological, geochemical, and geological changes occurring at the K/T boundary).