Compositional variability of selected sandy intervals in a muddy continental shelf-to-slope succession, Canterbury Basin, South Island, New Zealand

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Author(s): Marsaglia, K. M.; Bender-Whitaker, C.; Bailey, C. H.; Nolasco, J.
Author Affiliation(s): Primary:
California State University Northridge, Department of Geological Sciences, Northridge, CA, United States
Volume Title: AGU 2012 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2012; American Geophysical Union 2012 fall meeting, San Francisco, CA, Dec. 3-7, 2012. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Integrated Ocean Drilling Program (IODP) Expedition 317 drilled four sites in the Canterbury Basin off South Island, New Zealand. The goal of the expedition was to provide a complete stratigraphic record of the shelf and slope for correlation with interpreted seismic stratigraphy. Recovered lithologies were mostly mud and sandy mud with lesser shell hash, sand, and muddy sand (Fulthorpe et al., 2010). The objective of our study was to determine the compositional variability of Holocene to Pliocene sandy intervals from both shelf (U1351, U1353, U1354) and slope (U1352) sites. Sandy sediment was sampled systematically throughout recovered intervals, which included several potential seismic sequence boundaries. Samples were sieved and sand fractions were made into thin sections. Thin sections were stained for feldspar identification and point counted (400 points) using the Gazzi-Dickinson method to minimize effects of grain size variation. A detailed classification scheme of monomineralic, lithic and bioclastic components was used. The sand samples are fairly uniform in composition: predominantly feldspathic, with lesser quartz and lithic components (average QFL%Q= 39; F= 48; % L= 13). The feldspar includes both plagioclase and potassium varieties, whereas the quartz is predominantly monocrystalline. Lithic components are mainly metamorphic (e.g., quartz-mica tectonite) and sedimentary (mudstone), with rare volcanic fragments. Other common minerals include chlorite and mica, with lesser dense minerals. Bioclastic debris ranges from 0 to 70% of the sand fraction. There are no significant differences in composition among the samples from shelf and slope sites. Sand samples near or at horizons linked to seismic sequence boundaries showed no consistent compositional trends in terrigenous components or percent carbonate (bioclastic debris) as compared to others. This is in contrast to results from other workers focusing on the composition of muddy lithofacies within the same intervals (Jaeger and Villasenor, in prep.) where distinct trends are seen, and emphasizes the benefits of integrating studies of both fine and coarse sediment fractions within any depositional system.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Canterbury Basin; Clastic sediments; Continental margin; Continental shelf; Continental slope; Expedition 317; Integrated Ocean Drilling Program; Marine sediments; Mud; Pacific Ocean; Sediments; South Pacific; Southwest Pacific; West Pacific
Coordinates: S445700 S444600 E1720200 E1714000
Record ID: 2014098053
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