Depth to Quaternary regional unconformities offshore of the Delmarva Peninsula, including Maryland and Virginia state waters (2023)

Horizontal_Positional_Accuracy_Report:

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 downsampled, 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.

Vertical_Positional_Accuracy_Report:

Due to their frequency content, the nominal vertical resolution (precision) of the chirp and boomer/sparker seismic-reflection systems is 0.5 and 1 meter, respectively. Accuracy uncertainty was introduced by converting depths measured in two-way travel time to meters using a constant speed of sound that were used in the Kingdom Suite dynamic depth conversion model as described in the process steps. The vertical accuracy also depends on the accuracy of the composite bathymetric grid used to calculate the offsets that were applied to reference the structure map grids to the Mean Lower Low Water (MLLW) tidal datum. USGS bathymetric grids assumed a 50-cm or better overall accuracy. Refer to bathymetric metadata in Sweeney and others (2004), and Pendleton and others (2016) in the source information metadata for specific vertical accuracy reports. Coastal Planning & Engineering (2014) used a GPS system with a specified vertical accuracy of 5-10 cm. 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.

Source_Citation:

Type_of_Source_Media: Disk
Source_Time_Period_of_Content:

Source_Citation_Abbreviation: Coastal Planning & Engineering, 2014
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 each system 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.

Source_Citation:

Type_of_Source_Media: online
Source_Time_Period_of_Content:

Source_Citation_Abbreviation: Sweeney and others, 2015
Source_Contribution:

This report (version 3.0, May 2016) provided source seismic reflection profiles for the study area of the Delmarva Peninsula, including Maryland and 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 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.

Source_Citation:

Type_of_Source_Media: online
Source_Time_Period_of_Content:

Source_Citation_Abbreviation: Pendleton and others, 2016
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 survey 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.

Source_Citation:

Type_of_Source_Media: online
Source_Time_Period_of_Content:

Source_Citation_Abbreviation: Pendleton and others, 2015
Source_Contribution:

This report contributed data used to create a composite bathymetry grid for the study area of the Delmarva Peninsula, including Maryland and Virginia state waters. 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.

Source_Citation:

Type_of_Source_Media: Digital and/or Hardcopy
Source_Time_Period_of_Content:

Source_Citation_Abbreviation:

Scanned Uniboom seismic-reflection records from field activity 1974-004-FA

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).

Source_Citation:

Type_of_Source_Media: Digital and/or Hardcopy
Source_Time_Period_of_Content:

Source_Citation_Abbreviation:

Scanned Uniboom seismic-reflection records from field activity 1975-003-FA

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).

Process_Description:

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" ) ) thenecho "tif2segy -- convert a TIFF image file to a SEGY file"echo "By Andrew MacRae, and the authors of NetPBM and Seismic Unix"echoecho "Usage: tif2segy filename.tif"echoecho "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."echoecho "The program assumes that the "netpbm" image tools and "Seismic Unix""echo "are already in the command path."exit(1)elseecho "tif2segy -- convert a TIFF image file to a SEGY file"echo "By Andrew MacRae, and the authors of NetPBM and Seismic Unix"echoendif
if( `which tifftopnm | cut -f 1 -d ' '` == 'no' ) thenecho "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' ) thenecho "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 millisecondsset 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 headerssegyhdrs < $tiffile:r.su
# default header is not neededrm header
# write out a 40-line, 80 character/line header to be converted to EBCDIC
# get the name of the file, without a .tif endingset 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: " $linename " Field Activity 1975-003-FA Uniboom " | cut -c1-79 >> tif2segy_headerecho "C " >> tif2segy_headerecho "C This SEGY file was created by David Foster " >> tif2segy_headerecho "C " >> tif2segy_headerecho "C " >> tif2segy_headerecho "C File was converted using tif2segy, netpbm, and Seismic Unix " >> tif2segy_headerecho "C Author of tif2segy script is Andrew MacRae (andrew.macrae at smu.ca) " >> tif2segy_header
set i = 0while ($i < 32 )echo "C " >> tif2segy_headerset 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 filesecho "Cleaning up temporary files: tif2segy_header, binary, and" $tiffile:r.su
rm tif2segy_headerrm binary#rm $tiffile:r.su
exit(0)
The contact person for this and all subsequent processing steps below is David S. Foster.

Source_Used_Citation_Abbreviation: Sweeny and others (2015)
Source_Used_Citation_Abbreviation: Coastal Planning & Engineering (2014)
Source_Used_Citation_Abbreviation: Pendleton and others (2016)
Source_Used_Citation_Abbreviation: USGS Field Activity 1974-004-FA
Source_Used_Citation_Abbreviation: USGS Field Activity 1975-003-FA
Process_Date: 2020
Process_Contact:

Process_Description:

A reference bathymetric grid was created to correct horizons in Kingdom Suite to MLLW by combining sources from Coastal Planning & Engineering (2014), Pendleton and others (2015), Sweeney and others (2015) and Pendleton and others (2016). Gridded data (5-m cell size) were loaded to Global Mapper 18.0 from the source GeoTIFF files. In Global Mapper, grids were combined using Analysis-Combine/Compare Terrain Layers. Preference was given where data existed from Pendleton and others (2015) over where data existed for Coastal Planning & Engineering (2014), Sweeney and others (2015) and Pendleton and others (2016). The combined bathymetric grid was exported in Z-Map grid format with a 5-m grid cell size.

Process_Date: 2018

Process_Description:

The combined bathymetric reference grid from step two was imported to Kingdom Suite 2017, converted to two-way travel time (TWT) assuming a velocity of 1500 m/s using Extended Math Calculator, and create a horizon using Grid to Horizon. A sea floor horizon was picked manually, or where possible, by automatically using 2D Hunt for all the seismic profiles. Extended Math Calculator was used to calculate a difference between the picked sea floor and the MLLW sea floor horizon

Process_Date: 2018

Process_Description:

In Kingdom Suite 2017, regional unconformities were interpreted, picked, and merged to generate composite horizons as follows:
1) The top of Tertiary (U4 and younger unconformities) was picked. Horizons U1, U2, and U3 within the Tertiary (Brothers and others, 2020) were not mapped.
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 U10-10.5) 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 (includes tidal inlet and back barrier 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.

Process_Date: 2020

Process_Description:

In Kingdom Suite 2017, Kingdom Dynamic Depth Conversion was used to build a time to depth conversion models using the bathymetric, picked structure horizons, and computed composite structure horizons described in the previous steps. Clipping polygons were created to prevent extrapolation outside of the areal extent of each horizon where no interpretations were made. This was done using Kingdom Suite 2017 Create Polygon. In all models, a difference offset between the picked sea floor and the MLLW bathymetry was applied. The model was built with time horizons as follows:
Difference between picked sea floor and MLLW bathymetry (velocity above 1500 m/s)Picked sea floor (velocity above 1500 m/s)U10-U10.5 Composite Horizon (velocity above 1600 m/s)U9 Horizon (velocity above 1600 m/s)U8 Horizon (velocity above 1650 m/s)U6 Horizon (velocity above 1650 m/s)U4 Horizon (velocity above 1650 m/s)Uqt Composite Horizon (velocity above 1650 m/s)
Dynamic Depth Model creates a depth grid for each horizon. Grid parameters were a 100-m cell size, fit to data min tension/minimum curvature 0.5, and smoothness 6.
Lastly, in Dynamic Depth Conversion, Extract Depth Horizon for all horizon/unconformities was completed.

Process_Date: 2020

Process_Description:

Gridding
Gridding of the depth horizons generated in the previous step was done in Kingdom Suite 2017. Tertiary unconformities (U1, U2, and U3) were not mapped and therefore not gridded. U5 and U7, although not mapped and gridded, they were digitized and merged to partially define Uqt, and U5 the base of Qbd.
1) Two depth-to-Uqt 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. 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 created in the previous step. The legacy single-channel data were not included.
2) Three depth-to-U4 grids were created due to significant differences in line spacing. For the Maryland Wind Energy Area (Coastal Planning & Engineering, 2014), 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. For the USGS multichannel survey areas (Sweeney and others, 2015 and Pendleton and others, 2016), two grids were created, one for the base of the Persimmons Point Paleochannel and the other for the Ocean City Paleochannel. Gridding parameters were: Flex Gridding, 500-m cell size, and clip to polygon created in step one. The legacy single-channel data were not included.
3) Two depth-to-U6 grids were created, one for the base of the Exmore paleochannel and one for the Belle Haven paleochannel, using Flex Gridding with a 500-m cell size. USGS multichannel survey areas (Sweeney and others, 2015 and Pendleton and others, 2016) and legacy single-channel data were included. The clip to polygons created in step five was used to prevent extrapolation outside of the polygon and a 3000 m extrapolation limit was also applied to limit extrapolation of the legacy data.
4) Two depth-to-U8 grids were created, one for the base of the Eastville paleochannel and tributary paleochannels. Flex Gridding with a 500-m cell size was used for the USGS multichannel and chirp survey areas (Sweeney and others, 2015 and Pendleton and others, 2016) The legacy single-channel data were included. The clip to polygons created in step five was used to prevent extrapolation outside of the polygon and a 3000 m extrapolation limit was also applied to limit extrapolation of the legacy data.The multichannel data from Coastal Planning & Engineering (2014)was created using Inverse Distance to a Power (no mask), 100-m cell size, distance weight power 2, search distance 500 m, and smoothness value of 6.
5) One depth-to-U9 grid for all the chirp data from Sweeney and others (2015) and Pendleton and others (2016) and all the multichannel data from Coastal Planning & Engineering (2014) was created using Inverse Distance to a Power (no mask), 100-m cell size, distance weight power 2, search distance 500 m, and smoothness value of 6.
6) One depth-to-U10-U10.5 grid for all the chirp data from Sweeney and others (2015) and Pendleton and others (2016) all the chirp multichannel data from Coastal Planning & Engineering (2014), and the legacy single-channel data was created using Inverse Distance to a Power (no mask), 100-m cell size, distance weight power 2, search distance 500 m, and smoothness value of 6.
Grid Export was used to export all the grids to Z-map format.

Process_Date: 2020

Process_Description:

Z-map grids from previous step were opened in Global Mapper 20. If more than one grid was generated in Kingdom Suite with different gridding parameters, grids combined using Analysis-Combine/Compare Terrain Layers. The resulting composite grid used the smaller of the grid-cell size of the input grids. The depth-to-U6 was exported with a 100-m grid spacing to be consistant with all other depth grids. The positive depth grids were converted to negative values using Global Mapper Raster Calculator and exported to a new GeoTIFF file that is distributed with this data release.

Process_Date: 2021