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Thomas Library

Honors Thesis Archive

Author Lindsay N. McCullough
Title Habit, Formation and Implications of Elongate, Calcite Concretions, Victoria, Australia
Department Geology
Advisors John B. Ritter, Michael J. Zaleha, Robert Morris, and Horton H. Hobbs III
Year 2003
Honors University Honors
Full Text View Thesis (1423 KB) Note: This is a very large file; it may be easier to download the file to your computer and open it from there.
Abstract Elongate calcite concretions are exposed in cliffs composed of semi-consolidated Pleistocene beach and eolian dune sands on the western side of Cape Liptrap in Victoria, Australia. Concretions are rod-shaped and range from isolated individuals to coalescing masses of individuals. Concretions taper toward the shoreline and often have enlarged or bulbous landward ends, indicative of down-gradient growth. Thin sections show sand dominated by quartz and calcareous biogenic grains. No growth structures, such as banding, are visible. Two models of concretion formation are considered in this study: (1) an event-based model with increased flow velocities and gradients due to a tectonic event and (2) a continuous flow model under normal groundwater flow conditions. Both models are based on concretion formation in the phreatic zone parallel to groundwater flow gradients. Consequently, the current exposure of the concretions above the present day water table has important implications for late Quaternary landscape evolution in the study area relative to paleo-groundwater flow, tectonics, sea-level change, climatic oscillations, and shoreline erosion.

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