Nahant_CCB_surfgeol: Interpretation of Seafloor geologic units on the Massachusetts inner continental shelf between Nahant and Northern Cape Cod Bay (polygon shapefile; Geographic WGS 84)

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Frequently anticipated questions:

What does this data set describe?

Title:
Nahant_CCB_surfgeol: Interpretation of Seafloor geologic units on the Massachusetts inner continental shelf between Nahant and Northern Cape Cod Bay (polygon shapefile; Geographic WGS 84)
Abstract:
These data are qualitatively derived interpretive polygon shapefiles and selected source raster data defining surficial geology, sediment type and distribution, and physiographic zones of the sea floor from Nahant to Northern Cape Cod Bay. Much of the geophysical data used to create the interpretive layers were collected under a cooperative agreement among the Massachusetts Office of Coastal Zone Management (CZM), the U.S. Geological Survey (USGS), Coastal and Marine Geology Program, the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Army Corps of Engineers (USACE). Initiated in 2003, the primary objective of this program is to develop regional geologic framework information for the management of coastal and marine resources. Accurate data and maps of seafloor geology are important first steps toward protecting fish habitat, delineating marine resources, and assessing environmental changes because of natural or human effects. The project is focused on the inshore waters of coastal Massachusetts. Data collected during the mapping cooperative involving the USGS have been released in a series of USGS Open-File Reports (<http://woodshole.er.usgs.gov/project-pages/coastal_mass/html/current_map.html>). The interpretations released in this study are for an area extending from the southern tip of Nahant to Northern Cape Cod Bay, Massachusetts. A combination of geophysical and sample data including high resolution bathymetry and lidar, acoustic-backscatter intensity, seismic-reflection profiles, bottom photographs, and sediment samples are used to create the data interpretations. Most of the nearshore geophysical and sample data (including the bottom photographs) were collected during several cruises between 2000 and 2008. More information about the cruises and the data collected can be found at the Geologic Mapping of the Seafloor Offshore of Massachusetts Web page: <http://woodshole.er.usgs.gov/project-pages/coastal_mass/>.
  1. How should this data set be cited?

    Baldwin, Wayne, 2013, Nahant_CCB_surfgeol: Interpretation of Seafloor geologic units on the Massachusetts inner continental shelf between Nahant and Northern Cape Cod Bay (polygon shapefile; Geographic WGS 84): Open-File Report 2012-1157, 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.

    Pendleton, E.A., Baldwin, W.E., Barnhardt., W.A., Ackerman, S.D., Foster, D.S., Andrews, B.D., and Schwab, W.C., 2013, Shallow Geology, Seafloor Texture, and Physiographic Zones of the Inner Continental Shelf from Nahant to Northern Cape Cod Bay, Massachusetts: Open-File Report 2012-1157, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -70.830053
    East_Bounding_Coordinate: -70.154738
    North_Bounding_Coordinate: 42.341199
    South_Bounding_Coordinate: 41.932552

  3. What does it look like?

    <http://pubs.usgs.gov/of/2012/1157/GIS_catalog/SurficialGeology/surfgeo_browse.png> (png)
    Interpretation ofsurficial geologic units on the Massachusetts inner shelf between Nahant and northern Cape Cod Bay

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

    Beginning_Date: 04-Aug-2006
    Ending_Date: 07-May-2008
    Currentness_Reference: ground condition

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

    Geospatial_Data_Presentation_Form: vector 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):

      • G-polygon (333)

    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 Decimal degrees.

      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.

      Vertical_Coordinate_System_Definition:

  7. How does the data set describe geographic features?

    Nahant_CCB_surfgeol
    Surficial geologic unit (Source: seismic interpretation)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Formal codeset
    Codeset Name:Polygon
    Codeset Source:ESRI

    Coordinates defining the features.

    surf_unit
    Surficial geologic unit (Source: seismic interpretation)

    Formal codeset
    Codeset Name:Pz/Tcp/Qt - Undifferentiated Paleozoic bedrock, Late-Cretaceous or Tertiary coastal plain deposits, or Pleistocene glacial till or coarse drift deposits
    Codeset Source:seismic interpretation

    Formal codeset
    Codeset Name:Qd - Undifferentiated Pleistocene stratified glacial drift deposits. Commonly consists of vertically laminated, roughly horizontal to broadly undulating seismic reflectors or zone of near acoustic transparency.
    Codeset Source:seismic interpretation

    Formal codeset
    Codeset Name:Qfe - Holocene fluvial and estuarine deposits. The lowermost Holocene sedimentary deposit that fills the fluvial valleys incised into the surface of Qd. The surface is generally defined by the Holocene transgressive unconformity.
    Codeset Source:seismic interpretation

    Formal codeset
    Codeset Name:Qmn - Holocene nearshore marine deposits. Post-transgressive Holocene sediment deposits that are predominantly sand with varying proportions of gravel and mud and mostly restricted to the inner shelf area.
    Codeset Source:seismic interpretation

    Formal codeset
    Codeset Name:Qmd - Holocene deepwater marine deposits. Post-transgressive Holocene sediment deposits that are predominantly muddy with varying proportions of sand and are generally confined to portions of Cape Cod Bay that are deeper than 45 m.
    Codeset Source:seismic interpretation

    Area_SqKm
    Geologic unit outcrop area in square kilometers (Source: seismic interpretation)

    Range of values
    Minimum:0.002
    Maximum:237.146
    Units:Square Kilometers

    Entity_and_Attribute_Overview:
    Five primary seismic stratigraphic units and three major erosional unconformities were interpreted and mapped within the seismic survey area. 1.) Pleistocene till/old drift (Qt), Tertiary coastal plain deposits (Tcp), and Paleozoic bedrock (Pz) - Undifferentiated pre-Wisconsinan (?) till and Pre-Quaternary units that represent the acoustic basement of seimic survey. 2.) Fluvial Unconformity (Ul) - overlies Pz/Tcp/Qt and marks the base of Qd. 3.) Pleistocene glacial drift (Qd) - Undifferentiated, stratified, glacial deposits (up to 100 m thick (3)) composed of poorly sorted material ranging from muds to boulders. Limited and variable seismic penetrartion produces vetically laminated, roughly horizontal to broadly undulating reflectors and zones of acoustic transparency. 4.) Regressive Unconformity (Ur) - Overlies Qd and marks the base of Qfe. 5.) Holocene fluvial and estuarine (Qfe) - Fluvial sands and gravels, and estuarine sands and muds (locally > 19 m thick) that fill incised fluvial valleys. Produces vertically laminated, horizontal to concave-up reflectors and zones of acoustic transparency; local indications of cut-and-fill. 6.) Transgressive Unconformity (Ur) - Marks the base of Qmd and Qmn. 7.) Holocene deepwater marine (Qmd) - Mostly muddy deposits (locally > 16 m thick) that blaket basinal Cape Cod Bay (water depths > 45 m). Generally acoustically transparent with faint, flat-lying reflectors locally. 8.) Holocene nearshore marine - Mostly sandy deposits (typically < 2 m but up to 13 m thick) that form ridges and bars along the nearshore margins (water depths < 30 m) of the survey area. Generally acoustically transparent with faint, flat-lying reflectors locally.
    Entity_and_Attribute_Detail_Citation:
    The seismic stratigraphic units used here as attributes for surficial geology were first described by Oldale and O'Hara (1990) and Oldale and Bick (1987). The interpretation of the surficial extent of these units have been refined in this study using the dense, high resolution, seismic surveys of Andrews and others (2010) and Barnhardt and others (2010).

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?

    Wayne Baldwin
    U.S. Geological Survey
    Geologist
    U.S. Geological Survey
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

Why was the data set created?

This data set describes Seafloor geology on the Massachusetts inner shelf between Nahant and Northern Cape Cod Bay. Polygons are used to indicate the areal distribution of Seafloor outcrop for sub-surface stratigraphic units interpreted in high-resolution seismic reflection data. These data are useful for assessing relations between geologic framework, sea-bed morphology, and sediment textural trends.

How was the data set created?

  1. From what previous works were the data drawn?

    Barnhardt and others, 2010 (source 1 of 2)
    Barnhardt, Walter A., Ackerman, Seth D., Andrews, Brian D., and Baldwin, Wayne E., 2010, Geophysical and Sampling Data from the Inner Continental Shelf: Duxbury to Hull, Massachusetts.: Open-File Report 2009-1072, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Shallow geologic framework and surficial geology were interpreted from approximately 1920 trackline kilometers of CHIRP seismic-reflection profiles that were collected during two separate U.S. Geological Survey field activities (2006-012-FA and 2007-001-FA) . Final, post-processed profiles were used to make the interpretations. Thorough descriptions of acquisition and processing parameters for each survey are provided by Barnhardt and others (2010) in the methods section and seismic-reflection metadata.

    Andrews and others, 2010 (source 2 of 2)
    Andrews, Brian D., Ackerman, Seth D., Baldwin, Wayne E., and Barnhardt, Walter A., 2010, Geophysical and Sampling Data from the Inner Continental Shelf: Northern Cape Cod Bay, Massachusetts: Open-File Report 2010-1006, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Shallow geologic framework and surficial geology were interpreted from approximately 3270 trackline kilometers of CHIRP seismic-reflection profiles that were collected during two separate U.S. Geological Survey field activities (2007-002-FA and 2008-002-FA). Final, post-processed profiles were used to make the interpretations. Thorough descriptions of acquisition and processing parameters for each survey are provided by Andrews and others (2010) in methods sections and seismic-reflection metadata.

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

    Date: 2012 (process 1 of 4)
    CHIRP seismic reflection data were interpreted using Landmark SeisWorks 2D (R5000) seismic interpretation software. Interpretation consisted of identifying and digitizing erosional unconformities defining the boundaries between Holocene, Pleistocene, and pre-Quaternary seismic units, and digitizing the extent over which each of the defined sub-surface seismic units crops out on the seafloor. The digitized Seafloor outcrop extents for each seismic unit were sampled at a 30-meter along track interval and exported from SeisWorks as ASCII text. The resultant text file was imported into ArcMap (9.3.1) as point features (easting, northing, seismic unit) using the 'Add XY data' function, then saved as a point shapefile (UTM, Zone 19N, WGS84).

    Person who carried out this activity:

    Wayne E. Baldwin
    U.S. Geological Survey
    Geologist
    U.S. Geological Survey
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

    Date: 2012 (process 2 of 4)
    A polygon shapefile of the seismic-reflection survey area was created by digitizing around a polyline shapefile of the profile tracklines (file > new > shapefile in ArcCatalog 9.3.1, then editor >'create new feature' in ArcMap 9.3.1). A new attribute field named 'surf_unit' was added to the shapefile attribute table. The point shapefile containing the along track extents of seismic unit outcrop was then used to guide division of the larger survey area polygon into smaller polygons representative of individual seismic unit outcrop areas (using editor processes 'cut polygon feature', 'intersect', 'merge', and 'clip' in ArcMap 9.3.1). As each new polygon area was created, the 'surf_unit' attribute field was populated with the appropriate geologic unit label. Polygon editing was done at scales between 1:8,000 and 1:20,000, depending on the size of the outcrop area.

    Person who carried out this activity:

    Wayne E. Baldwin
    U.S. Geological Survey
    Geologist
    U.S. Geological Survey
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

    Date: 2012 (process 3 of 4)
    After final editing of the surficial geologic unit polygons they were exported to a geodatabase feature class and new topological rules were established (ArcCatalog 9.3.1). Topological errors, primarily overlaps and gaps, were identified and remedied using the topology toolbar in ArcMap (9.3.1).

    Person who carried out this activity:

    Wayne E. Baldwin
    U.S. Geological Survey
    Geologist
    U.S. Geological Survey
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

    Date: 2012 (process 4 of 4)
    The surficial geology polygon feature class was exported back to a shapefile and the 'Shape_Area' and 'Shape_Length' fields were deleted from its attribute table (ArcCatalog and ArcMap 9.3.1). XTools Pro (7.1.0) was then used to add and populate a new attribute field containing polygon area in square kilometers. Finally, the shapefile was reprojected from UTM zone 19 N, WGS 84 to GCS WGS84 using ArcToolbox.

    Person who carried out this activity:

    Wayne E. Baldwin
    U.S. Geological Survey
    Geologist
    U.S. Geological Survey
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

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

    Oldale, Robert N., and Bick, Jennifer, 1987, Maps and seismic profiles showing geology of the inner continental shelf, Massachusetts Bay, Massachusetts: U.S. Geological Survey Miscellaneous Field Studies Map MF-1923, U.S. Geological Survey, Woods Hole, MA.

    Other_Citation_Details: 4 sheets
    Oldale, Robert N., and O'Hara, Charles J., 1990, Maps showing the geology of the inner continental shelf, Cape Cod Bay, Massachusetts: U.S. Geological Survey Miscellaneous Field Studies Map MF-2118, U.S. Geological Survey, Woods Hole, MA.

    Online Links:

    Other_Citation_Details: 4 sheets

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?

    Navigational accuracy of the seismic-reflection data used for this interpretation was assumed to be ± 10 to 20 meters. Refer to seismic trackline metadata in Barnhardt and others (2010) and Andrews and others (2010) for specific seismic data aqcuisition parameters and accuracy reports. Additional navigational uncertainty in this interpretation arises from subjective digitizing of the seismic reflectors, sampling of the interpreted horizons at 30-m along track intervals prior to export from the seismic interpretation package, and heads up digitizing of the polygons defining individual areas of geologic unit outcrop. Considering these limitations, the boundaries between geologic outcrop units are consided considered to be accurate to within approximately ± 50 meters.

  3. How accurate are the heights or depths?

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

    All CHIRP seismic reflection data collected during USGS Woods Hole Coastal and Marine Science Center field activities 2006-012-FA, 2007-001-FA, 2007-002-FA, and 2008-002-FA were used to interpret the surficial geologic units.

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

    CHIRP seismic-reflection data used to interpret the surficial geology were collected during USGS Woods Hole Coastal and Marine Science Center field activities 2006-012-FA, 2007-001-FA, 2007-002-FA, and 2008-002-FA. The geologic framework interpretations in this report were correlated with previous interpretations by Oldale and Bick (1987) and Oldale and O'Hara (1990) for Massachusetts and Cape Cod bays, respectively.

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:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information. Additionally, there are limitations associated with qualitative geologic mapping interpretations. Because of the scale (polygon editing was done at scales between 1:8,000 and 1:20,000, depending on the size of the outcrop area) and line spacing of the source seismic profiles, not all changes in seafloor geology are captured. The boundaries of polygons are inferred between seismic lines, and polygon boundaries should be considered an approximation of the location of a change in geology. Further, a constant seismic velocity of 1,500 m/s was assumed for all profiles in all sediment types, which may result in inaccurate depths of stratigraphic units.

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

    Wayne E. Baldwin
    U.S. Geological Survey
    Geologist
    U.S. Geological Survey
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

  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 U.S. Geological Survey 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?

    These data are available in Environmental Systems Research Institute (Esri) Shapefile format. The user must have software capable of importing and processing this data type.

Who wrote the metadata?

Dates:
Last modified: 02-Jul-2013
Metadata author:
Wayne E. Baldwin
U.S. Geological Survey
Geologist
U.S. Geological Survey
Woods Hole, MA 02543-1598
USA

508-548-8700 x2226 (voice)
508-457-2310 (FAX)
wbaldwin@usgs.gov

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

Generated by mp version 2.9.21 on Tue Jul 02 13:41:12 2013