VASEDS, 1981

Metadata also available as - [Outline] - [Parseable text]

Frequently-anticipated questions:

What does this data set describe?
    Title: VASEDS, 1981
    Abstract:
    The distribution of the physical properties; patterns of deposition and rates of accumulation of sediments provide an integrating framework for investigations of the concentration and distribution of toxic substances. Over 2;000 grab samples of surface-sediment (1.4 km grid) reveal that the bottom of the Virginia portion of Chesapeake Bay is significantly sandier than hitherto reported. About 65% of the area is sand. The number of samples in this study is an order of magnitude greater (2;000 versus 200) than previous studies allowing a significantly better delineation of sedimentary characteristics. Distribution of sediment size is; in large part; a function of geomorphology; there being an apparently good correlation between depth and sediment type; the finer grained sediments are usually confined to the deeper channels. The exceptions to the depth:size relationship are the presence of grained sedimentation fines in the shallow; marginal embayments such as Mobjack Bay and the absence of fines in the deep channel in the southeastern section of the Bay. The occurence of sands here is a function of infilling with sands from the area of the Bay mouth and; perhaps; of scour into older (Pliocene) materials. Sediment distribution also reflects the local source with the shallow-water; marginal sands derived from erosion of the banks and relict features. Several large geomorphic features are distinguishable on the maps of sediment characteristics. These features include the deep channels; a large sand-shield near Tangier Island; relict spits; and the zone of influence of the Bay mouth. Nine hundred samples; selected to avoid the coarser sands; were analyzed for total carbon; organic carbon; and sulfur contents. There are strong correlations between these characteristics and sediment type; especially weight-percent clay. Additionally; there is a good relationship between the organic carbon and sulfur contents. Although total carbon content reached 10% in some samples; the average was 1.5%. Average organic carbon and sulfur contents were 1.0 and 0.34%. Comparisons of the bathymetry on charts from the 1850's and 1950's were used to delineate the patterns and volumes of cut and fill in the Virginia portion of the Chesapeake Bay. The comparisons were adjusted for relative sea level change and monthly variations in mean tide level. In addition; propagation of the error was evaluated and the results applied. Coupled with the data concerning the character of the surface sediments and adjusted for water content; the volumes of sediment shown by the bathymetric changes to have been deposited were converted to the masses of sand; silt; and clay deposited in a 100-year period. The patterns of deposition and erosion; particularly when coupled with grain-size information; provide very important insights into the sedimentation processes within the Bay. The main Bay-axial channel from Maryland and the transition to the Virginia basin are the principal deposition sites for clay. Silt-sized materials are somewhat more uniformly distributed throughout the stem; however; about 33% of silt accumulates in the transition region; an area of relatively low tidal-current energy. The Bay mouth may be the principal source of silt. The pattern of deposition of sand suggests that the Bay mouth source is very significant as very fine sands penetrate much further into the Bay than has heretofore been suspected. The patterns are consistent with present understanding of circulation within the Bay. The project includes an attempt at constructing a sediment budget using published values for silt and clay estuarine advection and contributions from shore erosion measured against the bottom residual accumulations. The residual accumulation of silt and clay is an order of magnitude larger than previously estimated. No previous work has considered the sand budget but the general assumption has been that the contribution from shore erosion would be the principal source. This study indicates the residue bottom accumulation of sand is greater than the shore erosion contribution by a factor of 40. It is evident that additional understanding of the flux of sediment through the Bay mouth and the mouths of the flanking tributaries is required. (<http://www.chesapeakebay.net/data/historicaldb/sedimentsmain.htm>)

  1. How should this data set be cited?

    Virginia Institute of Marine Sc, College of William and Mary, 1981, VASEDS, 1981.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -76.490540
    East_Bounding_Coordinate: -75.648560
    North_Bounding_Coordinate: 37.956670
    South_Bounding_Coordinate: 36.885530

  3. What does it look like?

    vaseds.jpg (JPEG)
    Image map showing extent and distribution of this data layer coverage

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

    Beginning_Date: Nov-1978
    Ending_Date: Jun-1979
    Currentness_Reference: ground condition

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

    Geospatial_Data_Presentation_Form: tabular digital data

  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):

      • Entity point (2161)

    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 0.000000. Longitudes are given to the nearest 0.000000. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.400000.
      The flattening of the ellipsoid used is 1/294.978698.

  7. How does the data set describe geographic features?

    vaseds

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    LATITUDE
    Latitude of coordinate description (Source: Source report)

    LONGITUDE
    Longitude of coordinate description (Source: Source report)

    SITENAME
    Survey or laboratory code for site (Source: Data compiler)

    Entity_and_Attribute_Overview:
    Two organic contents were given: TOTAL ORGANIC CARBON CONTENT (WT %.) and TOTAL ORGANIC CARBON (WT %.). Sulfur is TOTAL REDUCED SULFUR CONTENT (WT %.). Water content was put into wet water weight field (ACU; field 9) and water weights of zero ('0') removed as unlikely; all occurrences were at the end of the data set. There were many implausible MM3 (skewness) and MM4 (kurtosis) values >6. These were left as is. Eight analyses suspect as GSSC values don't match the GRZ bins The following fields were entered into the Acoustic Properties, Texture, Sediment Composition and Grain Size themes in dbSEABED: STATION ID CODE SiteName:Latitude [deg] #:Longitude [deg] #:::::Sampling Device::::::Province:Operator / Collector FGRSTD (FOLKS GRAPHIC STANDARD DEVIATION):FGRSKEW (FOLKS GRAPHIC SKEWNESS):SSK (unspecified SKEWNESS):XKK (unspecified KURTOSIS):MM+STD: STANDARD DEVIATION (2ND MOMENT MEASURE) (actually variance) Gravel [%] #:Sand [%] #:Silt [%] #:Clay [%] #::Median Grainsize [phi] #:MOMENT Mean Grainsize [phi] #:MOMENT Standard Deviation [phi] #::::::FOLK Inclusive Graphic Skewness [phi] #:FOLK Graphic (%5;%25;%75;%95) Kurtosis [phi] #:::Mode/s (phiM1 [%] ...) *::::::::::::::::::::::FOLK Inclusive Graphic (%16;%84;%95;%5) Std Dev [phi] #::::::MOMENT Skewness [phi] #:MOMENT Kurtosis [phi] #::FOLK (%16;%84;%50) Graphic Mean [phi] # 'total organic carbon content' (wt%): Organic Carbon (TOC; %) #:::::::::::::::::::::::Sulphur [%] #: Water / Wet Weight [%] # CWP_0200:CWP_0175:CWP_0150:CWP_0125:CWP_0100:CWP_0075:CWP_0050:CWP_0025:CWP0000:CWP0025:CWP0050:CWP0075:CWP0100:CWP0125:CWP0150::CWP0175:CWP0200:CWP0225:CWP0250:CWP0275:CWP0300:CWP0325:CWP0350:CWP0375:CWP0400:CWP0450:CWP0475:CWP0500:CWP0600:CWP0700::CWP0800:CWP0900:CWP1000:CWP1100:

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?

    Please review the cross reference information for the original data set credit to Byrne, et al, 1981.

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

    Duane Wilding
    Environmental Protection Agency, Chesapeake Bay Program
    PROJECT OFFICER (EPA Grant No. R806001010)
    410 Severn Ave, Suite 109
    Annapolis, MD 21403
    USA

    1-800-YOUR-BAY (voice)

Why was the data set created?
To determine sediment distribution, physical properties, sedimentation budgets, and rates in the Virginia Portion of the Chesapeake Bay

How was the data set created?
  1. From what previous works were the data drawn?

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

    (process 1 of 4)
    Significant figures were reduced to 5 for location and to 2 for texture classes, grainsize bins, and statistics.

    Person who carried out this activity:

    Jane Reid
    U.S. Geological Survey
    Geologist
    400 Natural Bridges Drive
    Santa Cruz, CA 95060
    USA

    (831) 427-4727 (voice)
    (831) 427-4748 (FAX)
    jareid@usgs.gov

    (process 2 of 4)
    Values > 998 in statistics and ACU and CMP fields were removed, assuming they were null values.

    Person who carried out this activity:

    Jane Reid
    U.S. Geological Survey
    Geologist
    400 Natural Bridges Drive
    Santa Cruz, CA 95060
    USA

    (831) 427-4727 (voice)
    (831) 427-4748 (FAX)
    jareid@usgs.gov

    (process 3 of 4)
    2nd moment measure was determined to be variance (not standard deviation) by comparing values to Folk Inclusive Graphic Standard Deviation. Variance values were converted to standard deviation (square root).

    Person who carried out this activity:

    Jane Reid
    U.S. Geological Survey
    Geologist
    400 Natural Bridges Drive
    Santa Cruz, CA 95060
    USA

    (831) 427-4727 (voice)
    (831) 427-4748 (FAX)
    jareid@usgs.gov

    (process 4 of 4)
    Digital data were hand formatted into dbSEABED data entry structure, then filtered and data-mined through dbSEABED software (version: db9_MNEs.bas)

    Person who carried out this activity:

    Jane Reid
    U.S. Geological Survey
    Geologist
    400 Natural Bridges Drive
    Santa Cruz, CA 95060
    USA

    (831) 427-4727 (voice)
    (831) 427-4748 (FAX)
    jareid@usgs.gov

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

    Byrne, Robert J. , Carl H. Hobbs, III, and Carron, Michael J. , 1981, Baseline Sediment Studies to Determine Distribution, Physical Properties, Sedimentation Budgets, and Rates in the Virginia Portion of the Chesapeake Bay,: Virginia Institute of Marine Science (VIMS), College of William and Mary, Gloucester Point, VA.

    Online Links:

How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

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

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

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: None

  1. Who distributes the data set?[Distributor contact information not provided.]

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

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Although this data set has been used by the U.S. Geological Survey (USGS), no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Trade, firm, or product names and other references to non-USGS products and services are provided for information only and do not constitute endorsement or warranty, express or implied, by the USGS, USDOI, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy.

  4. How can I download or order the data?

Who wrote the metadata?
Dates:
Last modified: 25-May-2005
Last Reviewed: 04-May-2005

Metadata author:
Jamey Reid
U.S. Geological Survey
IT Specialist (Data Management)
384 Woods Hole Rd.
Woods Hole, MA 02543-1598

(508) 548-8700 x2204 (voice)
(508) 457-2310 (FAX)
jreid@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

Generated by mp version 2.7.33 on Wed May 25 13:27:02 2005