Marine geology of the continental margin off southern Oregon

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Title: Marine geology of the continental margin off southern Oregon
Abstract:
"The continental margin off southern Oregon, which includes the shelf and slope from Cape Blanco to the Oregon-California border, exhibits a distinctive marginal-plateau structural pattern which divides the margin into the continental shelf, the upper continental slope and its associated benches, and the lower continental slope. Lutum transport and deposition have dominated the sedimentary processes on the margin since the start of Holocene time. The structure of the southern Oregon margin is characterized by north-south trending compressional folds, and near-vertical faults which have been down-dropped to the west. Large-scale folds on the upper slope have ponded sediments behind them resulting in the formation of the Klamath Plateau, Cape Blanco Bench, and other bench-like features. Development of the structural pattern is most likely a results of the compressive underthrusting of the oceanic lithospheric plate beneath the southernmost Oregon-northern California margin and the crustal extension which exists throughout the nearby continental and ocean basin. Useful stratigraphic horizons within the late Pleistocene and Holocene margin deposits include Mazama Ash (6600 B.P.) and several recognizable shifts in the abundance of radiolaria and planktonic foraminifera, particularly one dating from 5000-4000 years B.P. Holocene sedimentation rates vary from an average of 10 cm/1000 years on the upper slope to an average of 50 cm/1000 years on the lower slope, indicating that the lower slope is out-building and up-building more rapidly than the upper slope. The paleo-depth range of Pliocene fauna in sedimentary rocks from the margin suggests that subsequent to their deposition both uplift and subsidence occurred on the southern Oregon margin. Sediments from the southern Oregon margin consist primarily of olive gray lutite, gray lutite, and sand-silt layers. Olive gray lutite is Holocene in age and is ubiquitous on the margin, with the thickest accumulation (10m average) found on the lower slope, while the distribution of Holocene lutite on the upper slope is thin and patchy (3-4 m or less). The gray lutite appears to be a late Pleistocene deposit, and the sand-silt layers reflect both ages. The surface sediment distribution pattern on the shelf consists of modern inner shelf sand, modern central shelf mud, and mixed deposits of both types Relict deposits are present at the shelf edge. The lower slope consists entirely of modern mud, but the surface sediment on the upper slope and benches consists of both modern and relict deposits, and mixtures of the two. The mineralogy of the unconsolidated and consolidated sediments from the margin indicates that the Klamath Mountains have been the dominant source for these deposits since early Tertiary time. This is reflected in the abundance of blue-green hornblende and other heavy minerals indicative of the Mesozoic rocks of the Klamath Mountains; the same source is suggested for the abundant chlorite found in the clay fraction of margin sediments and rocks. There are indications in the mineralogy of lower slope sediments which suggest that the Tertiary strata of the southern Oregon Coast Ranges may be a secondary source for the deposits in this environment. When compared to the upper slope sediments, those from the lower slope have a higher feldspar content, a higher pyroxene-to-amphibole ratio, and an apparently higher illite content. As a result of the Holocene rise in sea level, the deposition of coarse clastics on the southern Oregon margin has been restricted to the inner shelf. Consequently, only the fine-grained lutum discharged from rivers is deposited on the outer margin environment. Submarine topography, oceanographic conditions, and gravity are important factors which affect transport and deposition of lutum on the margin. A model of modern lutum transport by bottom turbid layers and fine-particle suspensate is proposed for the southern Oregon margin. Long0period swell is believed to be responsible for much of the formation of bottom turbid layers on the shelf. Once formed, these turbid layers move north and west over the shelf under the influence of shelf currents, alternating tidal action, and gravity; upon reaching the slope they are funneled into submarine valleys and deposited on the lower slope and adjacent deep sea. Lutum deposited on the upper slope is eventually re-suspended and transported by southerly bottom currents into down-slope valleys; very little lutum remains behind on the upper slope. Deposition of fine-particle suspensate as well as slumping and other gravitational processes contribute to the lower slope sediments. The end result of modern lutum transport is the continual up-building and out-building of the lower slope."
Supplemental_Information:
U.S.Geological Survey research grants 14-08-0001-10766 - 11941 and -1287. Initial support for research and shiptime provided by the Office of Naval Research contract Nonr 1286 (10). Data digitized in 2005 by the USGS for inclusion into usSEABED (<http://walrus.wr.usgs.gov/usseabed>)
  1. How should this data set be cited?

    Spigai, Joseph John , 1971, Marine geology of the continental margin off southern Oregon: Oregon State University, Corvallis, OR.

    Other_Citation_Details: PhD. thesis

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -125.115
    East_Bounding_Coordinate: -124.555
    North_Bounding_Coordinate: 42.063
    South_Bounding_Coordinate: 42.823

  3. What does it look like?

    Spigai_PhD_1971 (JPG)
    Screen grab of sample distribution, coastline, and bathymetry

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 1967
    Ending_Date: 1968
    Currentness_Reference: Publication date

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: Paper

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • Point (34)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.00017. Longitudes are given to the nearest 0.00017. Latitude and longitude values are specified in Decimal degrees.

  7. How does the data set describe geographic features?

    Point
    SDTS point (Source: Source report)

    Sample number
    Sample number (Source: Oregon State University)

    Alpha numeric code based on year, month, sample number, and subcore information.

    Subsample depth
    Subsample depth (Source: Source report)

    Range of values
    Minimum:0
    Maximum:12.27
    Units:Meter
    Resolution:0.01

    Sand
    Amount of sand in sample (Source: Wentworth 1938)

    Range of values
    Minimum:0.1
    Maximum:100
    Units:Percent
    Resolution:0.1

    Silt
    Amount of silt in sample (Source: Wentworth 1938)

    Range of values
    Minimum:0
    Maximum:98.0
    Units:Percent
    Resolution:0.1

    Clay
    Amount of clay in sample (Source: source report)

    Range of values
    Minimum:0
    Maximum:87.2
    Units:Percent
    Resolution:0.0001

    Mean
    Mean grainsize (Source: Inman, 1952)

    Range of values
    Minimum:2.12
    Maximum:12.35
    Units:Phi
    Resolution:0.01

    Standard deviation
    Standard deviation of grain size distribution (Source: Inman, 1952)

    Range of values
    Minimum:0.2
    Maximum:7.35
    Units:Unitless
    Resolution:0.01

    Skewness
    Skewness of grain size distribution (Source: Inman, 1952)

    Range of values
    Minimum:-1.0
    Maximum:1.0
    Units:Unitless
    Resolution:0.01

    Carbonate
    CaCO3 (Source: Spigai PhD 1971)

    Range of values
    Minimum:0.41
    Maximum:5.32
    Units:Percent
    Resolution:0.01

    Organic carbon
    Organic carbon (Source: Spigai PhD 1971)

    Range of values
    Minimum:0.44
    Maximum:2.00
    Units:Percent
    Resolution:0.01

    Total carbon
    Total carbon (Source: Spigai PhD 1971)

    Range of values
    Minimum:0.69
    Maximum:2.30
    Units:Percent
    Resolution:0.01

    Radiocarbon age
    Age of sample using Carbon-14 dating technique including error limits (Source: Unknown)

    Range of values
    Minimum:5860
    Maximum:34300
    Units:Years
    Resolution:0.01

    Description
    Description of subsample (Source: Spigai PhD 1971)

    Description of subsample including sediment type, color, and age

    Composition of sediment samples (coarse fraction)
    Composition of sediment samples (coarse fraction) (Source: Spigai_PhD_1971)

    Percents of detrital grains, mica, volcanic glass, plant fibers, radiolaria, diatoms, planktonic foraminifera, benthic foramifera, fecal pellets, and glauconite

    Light mineral composition of sand fraction
    Light mineral composition of sand fraction (Source: Spigai_PhD_1971)

    Percents of quartz, k-feldspar, plagioclase, rock fragments, volcanic ash, mica, and other minerals.

    Heavy mineral composition of very fine sand fraction
    Heavy mineral composition of very fine sand fraction (Source: Spigai PhD 1971)

    Percents of amphibole (actinolite + tremolite, glaucophane, hornblende), epidote (clinozoisite, epidote, zoisite), garnet, olivine, pyroxene (orthopyroxene, clinopyroxene), aplite, chlorite, corundum, kyanite, mica, monazite, rutile, serpentine, sillimanite, sphene, spinel, staurolite, topaz, tourmaline, volcanic glass, zircon, opaque minerals (hematite and limonite; other minerals), rock fragments, weathered grains, others and unknown minerals.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    Joseph John Spigai at Oregon State University for the collection and analysis of the data. For inclusion into usSEABED: Digitization: Adam Jackson (USGS); Formatting corrections: Jane Reid (USGS) and Chris Jenkins (University of Colorado)

  3. To whom should users address questions about the data?

    College of Oceanic and Atmospheric Sciences, Oregon State University
    104 COAS Admin Bldg
    Corvallis, OR 97331-5503

    541-737-3504 (voice)

Why was the data set created?

Not stated.

How was the data set created?

  1. From what previous works were the data drawn?

  2. How were the data generated, processed, and modified?

    Date: Unknown (process 1 of 1)
    Need to get

    Person who carried out this activity:

    College of Oceanic and Atmospheric Sciences, Oregon State University
    104 COAS Admin Bldg
    Corvallis, OR 97331-5503

    541-737-3504 (voice)

    Data sources produced in this process:
    • Spigai_PhD_971

  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    Data were digitized by hand (typed in), visually compared to source and corrected. Where appropriate, data were tested for completeness using MS Excel. Locations checked using GIS.

  2. How accurate are the geographic locations?

    No navigational techniques given in report. Positions given to decimal minutes.

  3. How accurate are the heights or depths?

    Depth determination technique not given in report. Water depths recorded to nearest meter; subsample depths given to nearest centimeter.

  4. Where are the gaps in the data? What is missing?

    Location, textural, and statistical data digitized from Appendices 1 through 8. Additional information from table 5 also digitized.

  5. How consistent are the relationships among the observations, including topology?

    Data fall within normal ranges for the given parameters.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints:
Cite J.J. Spigai and Oregon State University as originators of the data.

  1. Who distributes the data set? (Distributor 1 of 2)

    College of Oceanic and Atmospheric Sciences, Oregon State University
    104 COAS Admin Bldg
    Corvallis, OR 97331-5503

    541-737-3504 (voice)

  2. What's the catalog number I need to order this data set?

    Spigai PhD 1971

  3. What legal disclaimers am I supposed to read?

    None

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    None

  1. Who distributes the data set? (Distributor 2 of 2)

    U.S. Geological Survey
    345 Middlefield Road
    Menlo Park, CA 94025

    650-329-5026 (voice)

  2. What's the catalog number I need to order this data set?

    536 (285) C356h (USGS library only)

  3. What legal disclaimers am I supposed to read?

    Although this dataset has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data. Users of the data should be aware of limitations of the data due to possible imprecision due to navigational inaccuracies and limitations of the statistical data.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    None

Who wrote the metadata?

Dates:
Last modified: 2005
Metadata author:
U.S. Geological Survey
c/o Jane A. Reid
Geologist
400 Natural Bridges Drive
Santa Cruz, CA 95060

831-427-4727 (voice)
Jareid@usgs.gov

Contact_Instructions: Email preferred
Metadata standard:
CSDGM Version 2 (FGDC-STD-001-1998)

Generated by mp version 2.8.17 on Sat May 20 20:57:47 2006