School of Earth Sciences - Theses

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    The stratigraphy and palaeontology of Cape Vani, Milos, Greece
    Coffey, Jessica ( 2005)
    Milos, dominated by Pliocene-Recent explosive calc-alkaline volcanics, is in the active Aegean Arc. This project investigated the microfauna and depositional environment of a sequence associated with the only terrestrial white smoker field in the world. White smokers occur in a volcaniclastic-hosted Mn-Fe-Ba deposit in a 1 km2 rift basin associated with dacite intrusives. Although the sediments are extensively hydrothermally altered, they have sedimentary structures and yield a variety of micro- and macrofossils. The typical microfaunal assemblage comprises Miliolinids (e.g. Quinqueloculina spp.; Triloculina spp.) and Elphidiids (Elphidium spp.). In the absence of any planktonic foraminifera, this assemblage is typical of inner shelf palaeodepths from around 10-50m. The occurrence of this fauna with echinoderm spines indicates an open marine setting with normal salinity levels. The associated coarse-grained burrowed facies with symmetrical ripples and hummocky cross stratification and a macrofauna of molluscs (e.g. pectinids, Mytilus, fish teeth) further indicates a shallow marine setting. Terrestrial artiodactyl megafauna occur at three levels in tuff and trough cross-laminated fluvial deposits suggesting close proximity to a regressive shoreline. Macrofauna were probably killed by tephra, rapidly disarticulated and removed into a shallow marine environment. The sequence is unconformably overlain by coarse-grained alluvial fan to braided river deposits deposited when Milos became emergent. Barite-silica white smokers derive from the ingress of and leaching by seawater into basement and overlying volcanics. Palaeontological-boiling data shows the fluid was at 165-140°C and the extremophile echinoderm spicule microfauna dominated because forams were unable to live in warm silica-laden turgid fluids with a high heavy metal content.