麻豆传媒

B. Sc. Honours Thesis

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Lacustrine-deltaic deposits in the Sydney Mines Formation contain paleosols. Three soil profiles (1 m, 1.2 m, and 0.9 m long) sampled over an 11.8 m interval of drill core taken ca. 200 m offshore Point Aconi, Cape Breton, show typical and diagnostic mottled colouring, root traces, plant fossils, and carbonate concretions. The three paleosols are relatively immature, with weakly developed horizonation and relict sedimentary layering. Geochemical evidence (immobile element ratios) indicate that parent materials were inhomogenous and not fully mixed during pedogenesis. Grey colour, and the presence of pyrite, siderite, kutnahorite (Mn-calcite), and organic material indicate the hydromorphic and reducing conditions associated with the pedogenic environment. A thin coal caps one profile.

Electron microprobe analysis of concretions reveals alternate layers of siderite, calcite, kutnahorite, and pyrite. Fluctuations in pH and Eh and limited ion availability probably formed the layers.

The Late Paleozoic Sydney Basin shows repeated sea level fluctuations (cyclothems). The incipient paleosols of this study mark the transition from a high stand (peat marsh and lake deposition) to a low stand (alluvial plain).

Keywords: Sydney Mines Formation, paleosols, root traces,
concretions, hydromorphic, cyclothems.
Pages: 73
Supervisor: Martin Gibling

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