Raw continuous resistivity profiling data collected in the Indian River Bay, Delaware, on April 12, 2010, on U.S. Geological Survey Field Activity 2010-006-FA

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Frequently-anticipated questions:

What does this data set describe?

Raw continuous resistivity profiling data collected in the Indian River Bay, Delaware, on April 12, 2010, on U.S. Geological Survey Field Activity 2010-006-FA
A geophysical survey to delineate the fresh-saline groundwater interface and associated sub-bottom sedimentary structures beneath Indian River Bay, Delaware, was carried out in April 2010. This included surveying at higher spatial resolution in the vicinity of a study site at Holts Landing, where intensive onshore and offshore studies were subsequently completed. The total length of continuous resistivity profiling (CRP) survey lines was 145 kilometers (km), with 36 km of chirp seismic lines surveyed around the perimeter of the bay. Medium-resolution CRP surveying was performed using a 50-meter streamer in a bay-wide grid. Results of the surveying and data inversion showed the presence of many buried paleochannels beneath Indian River Bay that generally extended perpendicular from the shoreline in areas of modern tributaries, tidal creeks, and marshes. An especially wide and deep paleochannel system was imaged in the southeastern part of the bay near White Creek. Many paleochannels also had high-resistivity anomalies corresponding to low-salinity groundwater plumes associated with them, likely due to the presence of fine-grained estuarine mud and peats in the channel fills that act as submarine confining units. Where present, these units allow plumes of low-salinity groundwater that was recharged onshore to move beyond the shoreline, creating a complex fresh-saline groundwater interface in the subsurface. The properties of this interface are important considerations in construction of accurate coastal groundwater flow models. These models are required to help predict how nutrient-rich groundwater, recharged in agricultural watersheds such as this one, makes its way into coastal bays and impacts surface water quality and estuarine ecosystems. For more information on the survey conducted for this project, see <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2010-006-FA>.
  1. How should this data set be cited?

    Bratton, John F. , and Cross, VeeAnn A. , 2014, Raw continuous resistivity profiling data collected in the Indian River Bay, Delaware, on April 12, 2010, on U.S. Geological Survey Field Activity 2010-006-FA: Open-File Report 2011-1039, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Cross, V.A., Bratton, J.F., Michael, H.A., Kroeger, K.D., Green, A., and Bergeron, E., 2014, Continuous Resistivity Profiling and Seismic-Reflection Data Collected in April 2010 from Indian River Bay, Delaware: Open-File Report 2011-1039, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -75.078533
    East_Bounding_Coordinate: -75.075067
    North_Bounding_Coordinate: 38.612000
    South_Bounding_Coordinate: 38.607950

  3. What does it look like?

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

    Calendar_Date: 12-Apr-2010
    Currentness_Reference: ground condition

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

  6. How does the data set represent geographic features?

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

    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 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Degrees and decimal minutes.

      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.

      Depth_Datum_Name: Local surface
      Depth_Resolution: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Implicit coordinate

  7. How does the data set describe geographic features?

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?

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

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)

Why was the data set created?

The purpose of this dataset is to provide the raw continuous resistivity profile data collected on April 12, 2010 in the Indian River Bay by the AGI SuperSting system. The small amount of data collected on this day were test files, and included as an archive of the data.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    The continuous resistivity profile (CRP) system used on this cruise was an AGI SuperSting marine system described at the website: www.agiusa.com/marinesystem.shtml. The particular system used for this acquisition was a 50-m streamer with an 11 electrode array with electrodes spaced 5 meters apart. The source electrodes are graphite, while the receiver electrodes are stainless steel. A dipole-dipole configuration was used for the data collection in which two fixed current electrodes are assigned with the measurement of voltage potential between electrode pairs in the remaining electrodes. The maximum depth below the water surface the streamer can reach is approximately 1/4 the streamer length. So for the 50-m streamer, maximum depth is about 12.5 meters. Each line of data acquisition records several files. The two files necessary for processing are the *.stg and the *.gps file. The STG file contains the resistivity data, while the GPS file contains the navigation information. The navigation system used in concert with the CRP system is a Lowrance LMS-480M with an LGC-2000 GPS antenna and a 200 kHz fathometer transducer. The antenna and fathometer transducer were mounted on the starboard side of the boat. The streamer tow point was on the port side aft. The layback offset between the navigation antenna and the first electrode was 17.6 meters on April 13 and 14. On April 15 the antenna and transducer were moved 1.6 m aft changing the layback offset to 16 m. This layback offset is accounted for by the acquisition system. The approximately 2 m lateral offset is not accounted for. The Lowrance transducer also contains a temperature sensor. Lowrance indicates the speed of sound used by the system is 4800 feet/second. Both the temperature and depth information are recorded in the logged GPS file. There are instances where no depth or temperature information is recorded due to an equipment problem. The CRP system images the subsurface electrical properties of an estuarine, riverine or lacustrine environment. Resistivity differences can be attributed to subsurface geology (conductive vs less conductive layers) and hydrogeologic conditions with fresh water exhibiting high resistivity and saline conditions showing low resistivity.

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

    Date: 12-Apr-2010 (process 1 of 1)
    The acquisition controlling command file (*.cmd) was set up indicating an electrode spacing of 1 meter. At the time of data acquisition, a scaling factor of 5 was used to reflect the actual 5 meter electrode spacing of the streamer. The data were transferred from the logging computer using AGISSAdmin software version These files were then emailed from the field to the USGS office in Woods Hole in a single zip file. The data files included in this release are the *.crs, *.cmd, *.gps, and *.stg. The two files essential for processing are the GPS and STG files. The GPS file contains the navigation, and in the case of the Lowrance system also includes water depth and water temperature. The STG file contains the resistivity measurements from each of the electrodes. The CRS file contains the contact resistance readings. The CMD file contains the parameters for data collection. These last two files aren't necessary for data processing, but can be useful in terms of troubleshooting. The field collection and data transfer were done by Emile Bergeron of the USGS

    Person who carried out this activity:

    Emile M. Bergeron
    U.S. Geological Survey
    Electronics Technician
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2337 (voice)
    (508) 457-2313 (FAX)

    Data sources produced in this process:
    • JD102_ZIP.zip

  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?

  2. How accurate are the geographic locations?

    The navigation system used was a Lowrance 480M with an LGC-2000 Global Positioning System (GPS) antenna. The antenna was located directly above the fathometer transducer mount point, but offset to the starboard by 2 meters from the resistivity streamer tow point. GPS data are assumed to be accurate wtihin 10 meters on this survey.

  3. How accurate are the heights or depths?

    All bathymetry values were acquired by the 200 kHz Lowrance fathometer. The fathometer was mounted on the starboard side of the R/V Knob, directly below the GPS antenna. The Lowrance manufacturer indicates the speed of sound used by the system to calculate depth is 4800 feet/second. The depth values are not corrected for the approximately 0.2 m transducer draft. All depth values are assumed to be accurate to within 1 meter.

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

    A single test line was collected on this day therefore this represents all the resistivity data collected on this particular day.

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

    Each file was looked at individually, but the files as a collection were handled in the same manner.

How can someone get a copy of the data set?

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

Access_Constraints: None.
The public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.

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

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)

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

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Neither the U.S. government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. 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. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  4. How can I download or order the data?

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

    The data are provided in a zip compressed file. The user must have software capable of uncompressing the archive. In addition, the raw data are available in a format compatible with AGI Geosciences Marine Log Manager software. The user must have software capable of reading the AGI format in order to process these data.

Who wrote the metadata?

Last modified: 30-Jun-2014
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
Woods Hole Coastal and Marine Science Center
Woods Hole, MA 02543-1598

(508) 548-8700 x2251 (voice)
(508) 457-2310 (FAX)

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

Generated by mp version 2.9.6 on Mon Jun 30 16:20:43 2014