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Underwood, Michael B; Hoke, Kimberly D (2000): Grain counts and XRD mineralogy of turbidite sand and hemipelagic mud from ODP Leg 168 sites [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.788844, Supplement to: Underwood, MB; Hoke, KD (2000): Composition and provenance of turbidite sand and hemipelagic mud in northwestern Cascadia Basin. In: Fisher, A; Davis, EE; Escutia, C (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 168, 1-15, https://doi.org/10.2973/odp.proc.sr.168.012.2000

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Abstract:
Sequences of late Pliocene to Holocene sediment lap onto juvenile igneous crust within 20 km of the Juan de Fuca Ridge in northwestern Cascadia Basin, Pacific Ocean. The detrital modes of turbidite sands do not vary significantly within or among sites drilled during Leg 168 of the Ocean Drilling Program. Average values of total quartz, total feldspar, and unstable lithic fragments are Q = 35, F = 35, and L = 30. Average values of monocrystalline quartz, plagioclase, and K-feldspar are Qm = 46, P = 49, and K = 5, and the average detrital modes of polycrystalline quartz, volcanic-rock fragments, and sedimentary-rock plus metamorphic-rock fragments are Qp = 16, Lv = 43, and Lsm = 41. Likely source areas include the Olympic Peninsula and Vancouver Island; sediment transport was focused primarily through the Strait of Juan de Fuca, Juan de Fuca Channel, Vancouver Valley, and Nitinat Valley. Relative abundance of clay minerals (<2-µm-size fraction) fluctuate erratically with depth, stratigraphic age, and sediment type (mud vs. turbidite matrix). Mineral abundance in mud samples are 0%-35% smectite (mean = 8%), 18%-59% illite (mean = 40%), and 29%-78% chlorite + kaolinite (mean = 52%). We attribute the relatively low content of smectite to rapid mechanical weathering of polymictic source terrains, with little or no input of volcanic detritus from the Columbia River. The scatter in clay mineralogy probably was caused by converging of surface currents, turbidity currents, and near-bottom nepheloid clouds from several directions, as well as subtle changes in glacial vs. interglacial weathering products.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: 47.838918 * Median Longitude: -128.278924 * South-bound Latitude: 47.756900 * West-bound Longitude: -128.792000 * North-bound Latitude: 47.917300 * East-bound Longitude: -127.730000
Date/Time Start: 1996-06-23T09:15:00 * Date/Time End: 1996-08-10T14:15:00
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
4 datasets

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Datasets listed in this publication series

  1. Underwood, MB; Hoke, KD (2000): (Table T6) Relative abundances of clay minerals from ODP Leg 168 sites. https://doi.org/10.1594/PANGAEA.788843
  2. Underwood, MB; Hoke, KD (2000): (Table T4) Detrital models for turbidite sand deposits from ODP Leg 168 sites. https://doi.org/10.1594/PANGAEA.788841
  3. Underwood, MB; Hoke, KD (2000): (Table T3) Petrographic point-counts of turbidite sand deposits from ODP Leg 168 sites. https://doi.org/10.1594/PANGAEA.788840
  4. Underwood, MB; Hoke, KD (2000): (Table T5) XRD mineralogy of hemipelagic mud and turbidite matrix from ODP Leg 168 sites. https://doi.org/10.1594/PANGAEA.788842