|The Late Cretaceous and Cenozoic geological history of the outer continental margin off Nova Scotia, Canada: Insights into margin evolution from a mature passive margin|
Campbell, D. Calvin (2011). The Late Cretaceous and Cenozoic geological history of the outer continental margin off Nova Scotia, Canada: Insights into margin evolution from a mature passive margin. PhD Thesis. Dalhousie University: Halifax. 280 pp.
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In the study area, the seismic stratigraphy reveals abrupt changes in depositional styles and sedimentary processes. Initially, seabed failure and deposition of the large MTD associated with the pre-drift surface represented rapid erosion of the middle to lower slope and sediment transfer into the deeper basin. This period was followed by sediment drift development and construction of a large terrace at the foot of slope. Finally, an apparently sudden transition to gravity flow (turbidity current) input occurred that was contemporaneous with a termination of sediment wave development, suggesting that either bottom current intensity decreased or gravity flow input overwhelmed the bottom current signal.Within the study area, inherited morphology affected subsequent deposition patterns for both along-slope and down-slope deposits. Regionally, the sediment wave field developed within a submarine embayment created by mass-wasting and channel incision. Locally, seafloor irregularities due to mass-wasting and protruding salt diapirs controlled the precise locations of maximum sediment wave growth. With the return to gravity-flow dominated deposition, the highest seismic amplitudes occur at the break in slope formed by the drift terrace. At the break in slope proximal to gravity flow input points, local topographic features at the scale of individual sediment waves controlled the distribution of gravity flows.The studied interval on the western Scotian margin represents alternations from gravity flow dominated to bottom current dominated to gravity flow dominated deposition. The results demonstrate the importance of morphological heritage in controlling subsequent deposition patterns. The morphologies of the bedforms observed in the study area provide insights into the hydrodynamics of bottom currents and sediment wave forming processes. With the onset of gravity flow deposition, the regional terrace formed by the sediment drift effectively trapped gravity flows that may have otherwise been transported to deeper parts of the basin. Locally, sediment wave morphology strongly influenced the locations of gravity flow conduits and depocenters.