Thickness of Quaternary seismic stratigraphic units offshore of the Delmarva Peninsula, including Maryland and Virginia state waters

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
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• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Foster, David S., 20230519, Thickness of Quaternary seismic stratigraphic units offshore of the Delmarva Peninsula, including Maryland and Virginia state waters: data release DOI:10.5066/P9GQY0ZN, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

   Online Links:

   • https://doi.org/10.5066/P9GQY0ZN
   • https://www.sciencebase.gov/catalog/item/64371a78d34ee8d4addccf4e

   This is part of the following larger work.
   Foster, David S., Brothers, Laura L., Baldwin, Wayne E., and Pendleton, Elizabeth A., 2023, Geospatial data layers of shallow geology from the inner continental shelf of the Delmarva Peninsula, including Maryland and Virginia state waters: data release DOI:10.5066/P9GQY0ZN, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.5066/P9GQY0ZN
   • https://www.sciencebase.gov/catalog/item/64370f69d34ee8d4addcc9b8

   Other_Citation_Details:

   Suggested citation: Foster, D.S., Brothers, L.L., Baldwin, W.E., and Pendleton, E.A., 2023, Geospatial data layers of shallow geology from the inner continental shelf of the Delmarva Peninsula, Maryland and Virginia: U.S. Geological Survey data release, https://doi.org/10.5066/P9GQY0ZN.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -75.975599
   East_Bounding_Coordinate: -74.452134
   North_Bounding_Coordinate: 38.656673
   South_Bounding_Coordinate: 36.923413
   

3. What does it look like?

   https://www.sciencebase.gov/catalog/file/get/64371a78d34ee8d4addccf4e/?name=Delmarva_thickness_Q_browse.png&allowOpen=true (PNG)

   Browse image of a grid representing the thickness of Quaternary sediment above the Quaternary-Tertiary (Uqt) unconformity offshore of the Delmarva Peninsula, Maryland and Virginia. Browse graphic images are provided for each thickness grid with the name Delmarva_thickness_Q*_browse.png.

   https://www.sciencebase.gov/catalog/file/get/64371a78d34ee8d4addccf4e/?name=Delmarva_thickness_Qbd_browse.png&allowOpen=true (PNG)

   Browse image of a grid representing the thickness of the Beaverdam Formation (Ubd) offshore of the Delmarva Peninsula, including Maryland and Virginia state waters.

   https://www.sciencebase.gov/catalog/file/get/64371a78d34ee8d4addccf4e/?name=Delmarva_thickness_Q2_browse.png&allowOpen=true (PNG)

   Browse image of a grid representing the thickness of the Q2 unit offshore of the Delmarva Peninsula, including Maryland and Virginia state waters.

   https://www.sciencebase.gov/catalog/file/get/64371a78d34ee8d4addccf4e/?name=Delmarva_thickness_Qcch_browse.png&allowOpen=true (PNG)

   Browse image of a grid representing the thickness of the Qcch unit offshore of the Delmarva Peninsula, including Maryland and Virginia state waters.

   https://www.sciencebase.gov/catalog/file/get/64371a78d34ee8d4addccf4e/?name=Delmarva_thickness_Qmn_browse.png&allowOpen=true (PNG)

   Browse image of a grid representing the thickness of the Qmn unit offshore of the Delmarva Peninsula, including Maryland and Virginia state waters.

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

   Beginning_Date: 15-May-1974

   Ending_Date: 14-Jul-2015

   Currentness_Reference:

   ground condition of the source data used in this interpretation.

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

   Geospatial_Data_Presentation_Form: GeoTIFF
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions, type Grid Cell
   2. What coordinate system is used to represent geographic features?
      

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:

      UTM_Zone_Number: 18
      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -75.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 100.0
      Ordinates (y-coordinates) are specified to the nearest 100.0
      Planar coordinates are specified in meters
      The horizontal datum used is WGS_1984.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.25722356049.
      
7. How does the data set describe geographic features?

   Entity_and_Attribute_Overview:

   There are no attributes associated with these 32-bit GeoTIFFs. Pixel values represent the thickness in meters with no reference to a vertical datum:
   Thickness of Q range from 1.90 m to 42.61 m
   Thickness of Qbd range from 0.09 m to 28.49 m
   Thickness of Q2 range from 0.01 m to 18.95 m
   Thickness of Qcch range from 0.02 m to 32.49 m
   Thickness of Qmn range from 0.04 m to 14.85 m

   Entity_and_Attribute_Detail_Citation: U.S. Geological Survey
   

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • David S. Foster
2. Who also contributed to the data set?
   Please recognize the U.S. Geological Survey (USGS) as the source of this information.
3. To whom should users address questions about the data?
   David S. Foster

   U.S. Geological Survey

   Geologist

   384 Woods Hole Rd.

   Woods Hole, MA
   

   USA

   508-548-8700 x2271 (voice)

   508-457-2310 (FAX)

   dfoster@usgs.gov

Why was the data set created?

How was the data set created?

1. From what previous works were the data drawn?

   Coastal Planning & Engineering, 2014 (source 1 of 6)

   Administration, Maryland Energy, 2014, Maryland Energy Administration High Resolution Geophysical Resource Survey Final Report of Investigations: Maryland Energy Administration: Coastal Planning & Engineering, Inc., a CB&I Company, Boca Raton, Florida.

   Online Links:

   • https://energy.maryland.gov/Reports/MEAGeophysicalSurveyReport2013.pdf

   Other_Citation_Details:

   The SEG-Y and bathymetry data that were used to interpret geologic units with Kingdom Suite Software 2d/3dPAK (ver. 2017 - 64-bit) can be requested from the Bureau of Ocean Energy and Management (BOEM).

   Type_of_Source_Media: Disk
   Source_Contribution:

   This report provided source geophysical data (seismic-reflection profiles) for the Maryland Wind Energy Area. High-resolution chirp seismic-reflection profiles using an EdgeTech Geo-Star full spectrum sub-bottom (FSSB) system and SB-0512i towfish. The multichannel seismic system consisted of a Geo-Source 200 Marine Multi-Tip Sparker source and a 24-channel Geometrics Geoeel streamer. Multibeam bathymetry were acquired using a Reson 7125 system. Processed bathymetry available as X, Y, and Z ascii files contributed to the creation of a composite bathymetry grid for the study area. Descriptions of acquisition and processing parameters for the survey are provided by Coastal Planning & Engineering (2014) in the methods section of the report. Shallow geologic framework and surficial geology were interpreted from post-processed chirp and sparker seismic-reflection profiles.

   Sweeney and others, 2015 (source 2 of 6)

   Sweeney, E.M., Pendleton, E.A., Ackerman, S.D., Andrews, B.A., Baldwin, W.E., Danforth, W.W., Foster, D.S., Thieler, E.R., and Brothers, L.L., 2015, High-resolution geophysical data collected along the Delmarva Peninsula in 2015, U.S. Geological Survey Field Activity 2015-001-FA: U.S. Geological Survey data release DOI:10.5066/F7P55KK3, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://cmgds.marine.usgs.gov/data/field-activity-data/2015-001-FA/
   • https://doi.org/10.5066/F7P55KK3

   Other_Citation_Details:

   SEG-Y seismic-reflection data referenced in this report were used to interpret geologic units with The Kingdom Suite Software 2d/3dPAK (ver. 2017 - 64-bit) can be obtain by contacting the author of this Data Release.

   Type_of_Source_Media: online
   Source_Contribution:

   This report (version 3.0, May 2016) provided source seismic reflection profiles for the study area of the Delmarva Peninsula, including Virginia state waters. The 2015 mapping was conducted on the Scarlett Isabella during U.S. Geological Survey field activity 2015-001-FA. Chirp seismic-reflection data were collected using an EdgeTech Geo-Star FSSB subbottom profiling system and an SB-0512i towfish. Multichannel seismic reflection data were acquired using an Applied Acoustics S-Boom source and a 16-channel Geometrics Geoeel digital streamer. For swath bathymetry, the USGS used a 234 kHz Systems Engineering and Assessment Ltd. (SEA) SWATHplus interferometric sonar (now BathySwath). Thorough descriptions of acquisition and processing parameters for each system are provided by Sweeney and others (2015) in the seismic-reflection metadata. Processed bathymetry are also available as 32-bit GeoTIFF files, which contributed to the creation of a composite bathymetry grid for the study area. Shallow geologic framework was interpreted from post-processed chirp and multichannel seismic-reflection profiles. The data release provides survey tracklines that are useful to see the seismic data distribution and trackline spacing.

   Pendleton and others, 2016 (source 3 of 6)

   Pendleton, E.A., Ackerman, S.D., Baldwin, W.E., Danforth, W.W., Foster, D.S., Thieler, E.R., and Brothers, L.L., 2016, High-resolution geophysical data collected along the Delmarva Peninsula 2014, U.S. Geological Survey Field Activity 2014-002-FA: U.S. Geological Survey data release DOI:10.5066/F7MW2F60, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://cmgds.marine.usgs.gov/data/field-activity-data/2014-002-FA/
   • https://doi.org/10.5066/F7MW2F60

   Other_Citation_Details:

   SEG-Y seismic-reflection data referenced in the report were used to interpret geologic units with The Kingdom Suite Software 2d/3dPAK (ver. 2017 - 64-bit) can be obtain by contacting the author of this Data Release.

   Type_of_Source_Media: online
   Source_Contribution:

   This report (version 4.0, October 2016) provided source seismic reflection profiles for the study area of the Delmarva Peninsula, including Maryland and Virginia state waters. The 2014 mapping was conducted on the Scarlett Isabella during U.S. Geological Survey field activity 2014-002-FA. Chirp seismic-reflection data were collected using an EdgeTech Geo-Star FSSB subbottom profiling system and an SB-0512i towfish. Multichannel seismic reflection data were acquired using an Applied Acoustics S-Boom source and a 16-channel Geometrics Geoeel digital streamer. For swath bathymetry,the USGS used a 234 kHz Systems Engineering and Assessment Ltd. (SEA) SWATHplus interferometric sonar (now BathySwath). Thorough descriptions of acquisition and processing parameters for each system are provided by Pendleton and others (2015) in the seismic-reflection metadata. Processed bathymetry available as 32-bit GeoTIFF files, which contributed to the creation of a composite bathymetry grid for the study area. Shallow geologic framework was interpreted from post-processed chirp and multichannel seismic-reflection profiles. The data release provides survey tracklines that are useful to see the seismic data distribution and trackline spacing.

   Pendleton and others, 2015 (source 4 of 6)

   Pendleton, E.A., Brothers, L.L., Thieler, E.R., Danforth, W.W., and Parker, C.E., 2015, National Oceanic and Atmospheric Administration hydrographic survey data used in a U.S. Geological Survey regional geologic framework study along the Delmarva Peninsula: U.S. Geological Survey Open-File Report 2014-1262, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.3133/ofr20141262
   • https://pubs.usgs.gov/of/2014/1262/

   Type_of_Source_Media: online
   Source_Contribution:

   This report contributed data used to create a composite bathymetry grid for the study area of the Delmarva Peninsula, Maryland and Virginia. Thorough descriptions of the merging and processing parameters are provided by Pendleton and others (2015) in the methods section of the report and the metadata.

   Scanned Uniboom seismic-reflection records from field activity 1974-004-FA (source 5 of 6)

   Data Librarian, U.S. Geological Survey, Woods Hole Coastal and Marine and Science Center, Unpublished material, Scanned images of Uniboom seismic-reflection profiles collected on U.S. Geological Survey cruise 1974-004-FA on the outer continental margin, Baltimore Canyon Trough, offshore New Jersey and Delaware (TIFF format, 300 dpi): USGS, Woods Hole, MA.

   Online Links:

   • https://cmgds.marine.usgs.gov/fan_info.php?fan=1974-004-FA
   • https://cotuit.er.usgs.gov/data/1974-004-FA/SE/Scans/Boomer/

   Other_Citation_Details:

   Supporting documents and navigation data are available at https://cotuit.er.usgs.gov/data/1974-004-FA. Metadata are available at https://cotuit.er.usgs.gov/files/1974-004-FA/SE/Scans/Boomer/FA74004_uniboom_scans_meta.html.

   Type_of_Source_Media: Digital and/or Hardcopy
   Source_Contribution:

   These data were used to extend seismic stratigraphic interpretations beyond the extents of USGS field activities 2014-002-FA and 2015-001-FA and Coastal Planning & Engineering (2014).

   Scanned Uniboom seismic-reflection records from field activity 1975-003-FA (source 6 of 6)

   Data Librarian, U.S. Geological Survey, Woods Hole Coastal and Marine and Science Center, Unpublished material, Scanned images of Uniboom seismic-reflection profiles collected on U.S. Geological Survey cruise 1975-003-FA on the Atlantic outer continental shelf (TIFF format, 300 dpi): USGS, Woods Hole, MA.

   Online Links:

   • https://cmgds.marine.usgs.gov/fan_info.php?fan=1975-003-FA
   • https://cotuit.er.usgs.gov/data/1975-003-FA/SE/Scans/Boomer/

   Other_Citation_Details:

   Supporting documents and navigation data are available at https://cotuit.er.usgs.gov/data/1975-003-FA. Metadata are available at https://cotuit.er.usgs.gov/files/1975-003-FA/SE/Scans/Boomer/FA75003_uniboom_scans_meta.html

   Type_of_Source_Media: Digital and/or Hardcopy
   Source_Contribution:

   These data were used to extend seismic stratigraphic interpretations beyond the extents of USGS field activities 2014-002-FA and 2015-001-FA and Coastal Planning & Engineering (2014).

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

   Date: 2020 (process 1 of 5)

   SEG-Y traces and associated navigation from Sweeney and others (2015), Pendleton and others (2016), and Coastal Planning & Engineering (2014) were loaded into Kingdom Suite 2017. SEG-Y data from USGS field activities 1974-004-FA and 1975-003-FA using navigation obtained from the USGS Coastal and Marine Hazards and Resources Program data server (https://cmgds.marine.usgs.gov/) were also loaded to Kingdom Suite. These SEG-Y files were created from 300-dpi grayscale TIFFs that were cropped and resampled in Adobe Photoshop, so that each pixel width was equal to a trace and each pixel height was equal to a time sample. The time of day in the navigation files were used to calculate trace numbers on the basis of shot-time intervals (0.5 seconds). These TIFFs were converted to SEG-Y files by tif2segy, a script that utilizes Seismic Unix and Netpbm image tools. The script was as follows:
   #!/bin/csh # Converts an 8-bit greyscale TIFF file to a segy file # Assumes that there is one pixel horizontally for each trace # and 1 pixel vertically for each time sample. # Assumes the sample interval in the resulting segy file # is 4ms (i.e. 250 samples or pixels per second) # # Author: Andrew MacRae, (Andrew.MacRae at SMU.CA)
   # usage: # tif2segy filename.tif
   # output will be put in filename.segy
   set tiffile = $1
   if ( !( -e "$tiffile" ) ) then echo "tif2segy -- convert a TIFF image file to a SEGY file" echo "By Andrew MacRae, and the authors of NetPBM and Seismic Unix" echo echo "Usage: tif2segy filename.tif" echo echo "Input file should be a TIFF file with the content of the seismic plot" echo "(i.e. no labels or annotation -- only the data) with 1 pixel per " echo "trace horizontally, and one pixel per sample vertically." echo "The number of traces and number of samples are calculated from the image size." echo "Output is placed in filename.segy." echo echo "The program assumes that the "netpbm" image tools and "Seismic Unix"" echo "are already in the command path." exit(1) else echo "tif2segy -- convert a TIFF image file to a SEGY file" echo "By Andrew MacRae, and the authors of NetPBM and Seismic Unix" echo endif
   if( `which tifftopnm | cut -f 1 -d ' '` == 'no' ) then echo "Could not find the NetPBM tools (e.g., tifftopnm)." echo "You need to install them, or put them into your command path." exit(1) endif
   if( `which suaddhead | cut -f 1 -d ' '` == 'no' ) then echo "Could not find Seismic Unix." echo "You need to install it, or put the programs into your command path." exit(1) endif
   # sample interval -- 4000 = 4 milliseconds set interval = 125
   # get size of image: # horizontal pixels -> number of traces # vertical pixels -> number of samples
   set traces = `tifftopnm < $tiffile | pnmfile | cut -f 3 -d ' ' -s` set samples = `tifftopnm < $tiffile | pnmfile | cut -f 5 -d ' ' -s`
   echo image file $tiffile has $traces horizontal pixels which will become "traces"
   # convert image to byte values and invert values (tifftopnm and pnminvert) # rotate and flip to Seismic Unix standard trace-sample orientation # (pnmflip), chop off PGM image header (tail), reformat data from # 8-bit character values to floating point (recast), and then # add trace headers and insert sample interval (suaddhead and # sushw). Output to Seismic Unix data file (.su file)
   tifftopnm < $tiffile | pnminvert | pnmflip -r90 -tb | tail +4 | recast in=uchar out=float | suaddhead ns=$samples ftn=0 | sushw key=dt a=$interval > $tiffile:r.su
   # create binary and EBCDIC headers segyhdrs < $tiffile:r.su
   # default header is not needed rm header
   # write out a 40-line, 80 character/line header to be converted to EBCDIC
   # get the name of the file, without a .tif ending set linename = $tiffile:r
   echo "C " > tif2segy_header
   # This will output a line with the linename (derived from the filename) # and then truncate the line to 80 characters # Please modify this header to describe your data. echo "C Line from file: " $linename " Field Activity 1975-003-FA Uniboom " | cut -c1-79 >> tif2segy_header echo "C " >> tif2segy_header echo "C This SEGY file was created by David Foster " >> tif2segy_header echo "C " >> tif2segy_header echo "C " >> tif2segy_header echo "C File was converted using tif2segy, netpbm, and Seismic Unix " >> tif2segy_header echo "C Author of tif2segy script is Andrew MacRae (andrew.macrae at smu.ca) " >> tif2segy_header
   set i = 0 while ($i < 32 ) echo "C " >> tif2segy_header set i = ($i + 1) end
   # write a SEGY file using headers and Seismic Unix file. Include 'endian=0' if using a little endian machine. segywrite tape=$tiffile:r.segy bfile=binary hfile=tif2segy_header endian=0 < $tiffile:r.su
   # leave cleanup to the user, in case they want to review the # Seismic Unix files echo "Cleaning up temporary files: tif2segy_header, binary, and" $tiffile:r.su
   rm tif2segy_header rm binary #rm $tiffile:r.su
   exit(0)
   The contact person for this and all subsequent processing steps below is David S. Foster. Person who carried out this activity:
   

   David S Foster

   U.S. Geological Survey, Northeast Region

   Geologist

   384 Woods Hole Road

   Woods Hole, MA
   

   USA

   508-4548-8700 x2271 (voice)

   508-457-2310 (FAX)

   dfoster@usgs.gov

   Data sources used in this process:

   • Sweeny and others (2015)
   • Coastal Planning & Engineering (2014)
   • Pendleton and others (2016)
   • USGS Field Activity 1974-004-FA
   • USGS Field Activity 1975-003-FA

   Date: 2020 (process 2 of 5)

   In Kingdom Suite 2017, regional unconformities were interpreted, picked, and merged to generate composite horizons as follows:
   1) The top of Tertiary was picked.
   2) A base of the Persimmons Point and Ocean City paleochannels (Qpp) horizon (U4) was digitized on the multichannel and legacy single-channel seismic data.
   3) A subaerial unconformity (U5) and base of Qbd (Beaverdam Formation) was digitized on multichannel and legacy single-channel seismic data.
   4) A base of the Exmore and Belle Haven paleochannels (Qx) horizon (U6) was digitized on the multichannel and legacy single-channel seismic data.
   5) A transgressive ravinement unconformity (U7) was digitized on chirp and multichannel data.
   6) A base of the Eastville paleochannel and tributary paleochannels (Qe) horizon (U8) was digitized on the multichannel and legacy single-channel seismic data.
   7) A transgressive ravinement unconformity (U9) was digitized on chirp and multichannel data.
   8) A base of the Cape Charles paleochannel and tributary paleochannels (Qcch) horizon (U10) was digitized on the chirp, multichannel, and legacy single-channel seismic data.
   9) A base of the Cape Charles paleotidal inlet and estuarine (Qbb) tidal ravinement horizon (U10.5) was digitized on the chirp seismic data.
   10) The Holocene Ravinement surface, bottom of Qmn, was digitized.
   11) A composite top of Tertiary (Uqt) horizon was created by merging horizons (Top of Tertiary, U4, U5, U6, U7, U8, U9, and U10-U10.5) interpreted on chirp and multichannel seismic data, giving preference to the deepest interpreted horizon along each seismic line. This was accomplished by running Calculator-Math on Two Maps ("or" function) multiple times. The merged horizon was edited for spikes and deleted in places where the deepest interpreted horizon did not always represent Uqt.
   12) A composite top of Qbd horizon was created by merging horizons (U5, U6, U7, U8, U9, and U10-U10.5) interpreted on chirp and multichannel seismic data, giving preference to the deepest interpreted horizon starting with U5 along each seismic line. This was accomplished by running Calculator-Math on Two Maps ("or" function) multiple times. The merged horizon was edited for spikes and deleted in places where the deepest interpreted horizon did not always represent the top of Qbd. This composite horizon was used to compute the total thickness of Quaternary sediment.
   13) A composite unconformity (U10-U10.5) was generated by merging the U10 and U10.5 horizons interpreted on all seismic data, giving preference to the deeper U10 horizon. This was accomplished by running Calculator-Math on Two Maps ("or" function). The merged horizon was edited for spikes. This composite horizon was used as a lower boundary to compute the thickness of Qcch.
   14) A composite unconformity (U11-Seafloor) was generated by merging the U11 and the picked sea-floor horizon interpreted on all seismic data, giving preference to the deeper U11 horizon. This was accomplished by running Calculator-Math on Two Maps ("or" function). The merged horizon was edited for spikes. The composite horizon was used as an upper boundary to compute the thickness of Qcch that includes tidal inlet and backbarrier deposits (Qbb).
   15) A composite unconformity (U10-U10.5-U11-Seafloor) was generated by merging the U10-U10.5 and U11-Seafloor, giving preference to the deeper U110-U10.5 horizon. This was accomplished by running Calculator-Math on Two Maps ("or" function). The merged horizon was edited for spikes. The composite horizon was used as an upper boundary to compute the thickness of Q2.

   Date: 2020 (process 3 of 5)

   Kingdom Suite 2017 Extended Math Calculator was used to compute seismic unit thickness in two-way travel time by subtracting upper bounding horizons from lower bounding horizons and saving as an isochron horizon. If there were any negative values, they were set to null values using the Basic Math Calculator assignTnull function, less than or equal to 0. Extended Math Calculator was then used to convert two-way travel time (seconds) to thickness in meters. Not all thickness of seismic units from Brothers and others (2020) were calculated, specifically Qpp, Q1, Qx, and Qe. Their thicknesses are included within the thickness of Q. The calculations were done as follows:
   1) Q, the picked sea-floor time horizon was subtracted from the composite Uqt time horizon. Two-way time was converted to meters using a velocity of 1650 m/s.
   2) Qbd, the composite upper boundary of Qbd time horizon was subtracted from the picked U5 horizon. Two-way time was converted to meters using a velocity of 1650 m/s.
   3) Q2, the composite upper boundary of Q2 (U10-10.5-U11-Seafloor) was subtracted from the picked U9 horizon. Two-way time was converted to meters using a velocity of 1600 m/s.
   4) Qcch, the composite upper boundary of Qcch (U11-Seafloor) was subtracted from the composite lower boundary of Qcch (U10-U10.5) horizon. Two-way time was converted to meters using a velocity of 1600 m/s.
   5) Qmn, the picked sea-floor horizon was subtracted from the composite U11-Seafloor horizon, this giving zero values where U11 does not exist. Two-way time was converted to meters using a velocity of 1600 m/s.

   Date: 2020 (process 4 of 5)

   Gridding
   Gridding of the thickness horizons generated in the previous step was done in Kingdom Suite 2017.
   1) Two Q thickness grids were created due to significant differences in line spacing between USGS multichannel seismic surveys and the Maryland Wind Energy Area (Coastal Planning & Engineering, 2014). The gridding parameters were: Inverse Distance to a Power (no mask), 100-m cell size, distance weight power 2, search distance 150 m, and smoothness value of 6 were used for the Maryland Wind Energy Area. For the USGS multichannel survey areas (Sweeney and others, 2015 and Pendleton and others, 2016) gridding parameters were: Flex Gridding, 500-m cell size, and clip to polygon. The legacy single-channel data were not included.
   2) One Qbd thickness grid using all of the available seismic data including the single-channel legacy data was created using Inverse Distance to a Power (no mask), 100-m cell size, distance weight power 2, search distance 300 m (prevented interpolation beyond this value), and smoothness value of 6.
   3) One Q2 thickness grid using all of the available seismic data excluding the single-channel legacy data was created using Inverse Distance to a Power (no mask), 100-m cell size, distance weight power 2, search distance 500 m (prevented interpolation beyond this value), and smoothness value of 6.
   4) One Qcch thickness grid using all of the available seismic data including the single-channel legacy data was created using Inverse Distance to a Power (no mask), 100-m cell size, distance weight power 2, search distance 500 m (prevented interpolation beyond this value), and smoothness value of 6.
   5) One Qmn thickness grid using all of the available seismic data excluding the single-channel legacy data was created using Inverse Distance to a Power (no mask), 100-m cell size, distance weight power 2, search distance 300 m (prevented interpolation beyond this value), and smoothness value of 6.
   Grid Export was used to export all the grids to Z-map format.

   Date: 2023 (process 5 of 5)

   Z-map grids from the previous step were opened in Global Mapper v20.0 and v21.0. The two Q thickness grids generated with different gridding parameters were combined using Analysis-Combine/Compare Terrain Layers. The resulting composite grid used the smaller (100 m) of the grid-cell size of the input grids. The Q2 grid was resampled from 200 m to 100m grid spacing to be consistant with other grids. The Z-Map grids exported to a new GeoTIFF file that is distributed with this data release.

3. What similar or related data should the user be aware of?
   Brothers, Laura L., Foster, David S., Pendleton, Elizabeth A., and Baldwin, Wayne E., 2020, Seismic Stratigraphic Framework of the Continental Shelf Offshore Delmarva, U.S.A.: Implications for Mid-Atlantic Bight Evolution since the Pliocene: Marine Geology Volume 428, October 2020.

   Online Links:

   • https://doi.org/10.1016/j.margeo.2020.106287

   Other_Citation_Details:

   Use this citation to refer to the seismic stratigraphic units and unconformities represented in the structure surfaces and sediment thickness maps presented in this data release.

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 USGS chirp seismic-reflection data was assumed to be 10 meters. Refer to seismic trackline metadata in Sweeney and others (2015), and Pendleton and others (2016) in the source information for specific seismic data acquisition parameters and accuracy reports. Navigational accuracy of the USGS multichannel seismic-reflection data was assumed to be 2 meters; however, inaccuracies likely exceed this value due to uncertainty of source and receiver positions and azimuths calculated in the layback correction. Refer to seismic trackline metadata in Sweeney and others (2015), and Pendleton and others (2016) in the source information for specific seismic data acquisition parameters and accuracy reports. Navigational accuracy for seismic data acquired by Coastal Planning & Engineering (2014) used a DGPS system using STARFIX II network opertated by Fugro Inc. resulted in sub-mater accuracy of the navigation reference point (NRP) located on the ship. Horizontal offsets to geophysical systems were measured referenced to the NRP. The chirp tow vehicle had layback corrections applied from an ultra-short baseline (USBL) system or by a static layback when the USBL failed. Coastal Planning & Engineering (2014) state that positioning for the multichannel seismic data used DGPS and measured offsets and computed layback that were merged with the processed SEG-Y data. The scanned TIFF images of Uniboom seismic-reflection profiles from USGS field activities 1974-004-FA and 1975-003-FA had a resolution of 300 dpi. The TIFF images were down sampled, before converting to SEG-Y format, to reflect a shot rate of 0.5 seconds. This resulted in one-pixel width in the X dimension per SEG-Y trace. Navigation was with Loran-C, which has an accuracy of 0.1 to 0.25 nautical miles(185.2 to 463 m). Navigation fix points were at 10-minute intervals for 1974-004-FA and 5 minute intervals for 1975-003-FA, or at a ship speed of 5 knots, 772 meter and 1543 meter intervals. The datum of WGS 1972 for geographic coordinate pairs were transformed to WGS 84.
3. How accurate are the heights or depths?
   These grids represent thickness, thus do not apply to vertical position. The nominal vertical resolution of the chirp and boomer/sparker seismic-reflection systems is 0.5 and 1 meter, respectively. The scanned TIFF images of Uniboom seismic-reflection profiles from USGS field activities 1974-004-FA and 1975-003-FA had a resolution of 300 dpi. The TIFF images were downsampled, before converting to SEG-Y format, to reflect a vertical sample rate of 0.125 ms or 1600 samples per 200 ms trace length. Vertical datum corrections were not applied to the trace data. Additional uncertainty was introduced by converting thickness measured in two-way travel time to meters using a constant speed of sound as specified in the process steps.
4. Where are the gaps in the data? What is missing?
   All chirp and multichannel seismic-reflection data collected within the study area during USGS Woods Hole Coastal and Marine Science Center field activities 2014-002-FA, 2015-001-FA, chirp and multichannel sparker data from the 2013 Maryland Wind Energy Area survey (Coastal Planning & Engineering, 2014), and legacy single-channel Uniboom data from USGS field activities 1974-004-FA and 1975-003-FA were used to interpret the subsurface geologic units.
5. How consistent are the relationships among the observations, including topology?
   All chirp and multichannel seismic-reflection data collected within the study area during USGS Woods Hole Coastal and Marine Science Center field activities 2014-002-FA, 2015-001-FA, chirp and multichannel sparker data from the 2013 Maryland Wind Energy Area survey (Coastal Planning & Engineering, 2014), and select USGS single-channel Uniboom profiles from USGS field activities 1974-004-FA and 1975-003-FA were used to interpret the subsurface geologic units that are published in this data release. All seismic reflection data used in this data release were interpreted by Laura L. Brothers and David S. Foster. David S. Foster conducted the processing steps. Unless stated otherwise, all interpretations, two-way travel time conversions to depth, and horizon gridding were conducted in Kingdom Suite 2017 software.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey - ScienceBase

   Denver Federal Center, Building 810, Mail Stop 302

   Denver, CO
   

   United States

   1-888-275-8747 (voice)

   sciencebase@usgs.gov
2. What's the catalog number I need to order this data set? Delmarva_thickness_Q.tif is a GeoTIFF representing the thickness of Quaternary sediment (Q) above the Tertiary to Quaternary unconformity (Uqt) offshore of the Delmarva Peninsula, including Maryland and Virginia state waters. The dataset also includes a browse graphic file (Delmarva_thickness_Q_browse.png) and the associated CSDGM metadata in XML format. Delmarva_thickness_Qbd.tif is a GeoTIFF representing the thickness of Qbd offshore of the Delmarva Peninsula, including Maryland and Virginia state waters. The dataset also includes a browse graphic file (Delmarva_thickness_Qbd_browse.png) and the associated CSDGM metadata in XML format. Delmarva_thickness_Q2.tif is a GeoTIFF representing the thickness of Q2 offshore of the Delmarva Peninsula, including Maryland and Virginia state waters. The dataset also includes a browse graphic file (Delmarva_thickness_Q2_browse.png) and the associated CSDGM metadata in XML format. Delmarva_thickness_Qcch.tif is a GeoTIFF representing the thickness of Qcch offshore of the Delmarva Peninsula, including Maryland and Virginia state waters. The dataset also includes a browse graphic file (Delmarva_thickness_Qcch_browse.png) and the associated CSDGM metadata in XML format. Delmarva_thickness_Qmn.tif is a GeoTIFF representing the thickness of Qmn offshore of the Delmarva Peninsula, including Maryland and Virginia state waters. The dataset also includes a browse graphic file (Delmarva_thickness_Qmn_browse.png) and the associated CSDGM metadata in XML format.
3. What legal disclaimers am I supposed to read?
   Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.
4. How can I download or order the data?
   • Availability in digital form:

     Data format:	The dataset consists of five 32-bit GeoTIFF images and the accompanying CSDGM metadata. in format GeoTIFF (version 32-bit GeoTIFF) 32-bit GeoTIFFs with pixel values representing thickness in meters of seismic stratigraphic units. Size: 6
     Network links:	https://www.sciencebase.gov/catalog/file/get/64371a78d34ee8d4addccf4e https://www.sciencebase.gov/catalog/item/64371a78d34ee8d4addccf4e https://doi.org/10.5066/P9GQY0ZN

   • Cost to order the data: None

5. What hardware or software do I need in order to use the data set?
   The imagery files are a 32-bit GeoTIFF image format with a world file. To utilize these data an image processing or GIS software package capable of importing a 32-bit TIFF image is needed. Standard image viewing software cannot translate a 32-bit image.

Who wrote the metadata?

Dates:

Last modified: 19-May-2023

Metadata author:

David S. Foster

U.S. Geological Survey

Geologist

384 Woods Hole Rd.

Woods Hole, MA

USA

508-548-8700 x2271 (voice)

508-457-2310 (FAX)

whsc_data_contact@usgs.gov

Contact_Instructions:

The metadata contact email address is a generic address in the event the person is no longer with the USGS.

Metadata standard:

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