These data were drawn and vetted for accuracy using the source input rasters and point sample data described in the processing steps and source contributions. Overlapping features and unintentional gaps within the survey area were identified using the topology checker in ArcMap (version 10.2.2) and corrected or removed.
These sediment cover data are defined for areas where source data exists. In general, gaps in the coverage coincide with gaps in the source data. However, some data gaps were interpreted through extrapolation or by using hydrographic survey data only from NOS. Areas with fewer input data sources, lower data quality, and incomplete coverage are noted in a data quality attribute field.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Pendleton, E.A.
Originator: Ackerman, S.D.
Originator: Baldwin, W.E.
Originator: Danforth, W.W.
Originator: Foster, D.S.
Originator: Thieler, E.R.
Publication_Date: 2014
Title:
High-resolution geophysical data collected along the Delmarva Peninsula 2014, U.S. Geological Survey Field Activity 2014-002-FA
Edition: 4.0
Geospatial_Data_Presentation_Form: raster and vector digital data
Series_Information:
Series_Name: data release
Issue_Identification: DOI:10.5066/F7MW2F60
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Online_Linkage: https://doi.org/10.5066/F7MW2F60
Type_of_Source_Media: online
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20140618
Ending_Date: 20140722
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: Pendleton and others, 2014
Source_Contribution:
This report provided the majority of the geophysical and sample data from the northern half (Fenwick Island to the southern end of Assateague Island) of the study area. The side-scan sonar mosaics formed the basis for digitizing polygons based on differences in backscatter intensity.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Sweeney, E.M.
Originator: Pendleton, E.A.
Originator: Ackerman, S.D.
Originator: Andrews, B.D.
Originator: Baldwin, W.E.
Originator: Danforth, W.W.
Publication_Date: 2015
Title:
High-resolution geophysical data collected along the Delmarva Peninsula in 2015, U.S. Geological Survey Field Activity 2015-001-FA
Edition: 3.0
Geospatial_Data_Presentation_Form: raster and vector digital data
Series_Information:
Series_Name: data release
Issue_Identification: DOI:10.5066/F7P55KK3
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Online_Linkage: https://doi.org/10.5066/F7P55KK3
Type_of_Source_Media: online
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20150610
Ending_Date: 20150714
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: Sweeney and others, 2015
Source_Contribution:
This report provided the majority of the geophysical and sample data from the southern half (Chincoteague Island to Fisherman's Island) of the study area. The side-scan sonar mosaics formed the basis for digitizing polygons based on differences in backscatter intensity.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Toscano, M.A.
Originator: Kerhin, R.T.
Originator: York, L.L.
Originator: Cronin, T.M.
Originator: Williams, S.J.
Publication_Date: 1989
Title:
Quaternary Stratigraphy of the inner continental shelf of Maryland
Edition: 1.0
Geospatial_Data_Presentation_Form: document
Series_Information:
Series_Name: Report of Investigations
Issue_Identification: 50
Publication_Information:
Publication_Place: Baltimore, MD
Publisher: Maryland Geological Survey
Online_Linkage: http://www.mgs.md.gov/publications/report_pages/RI_50.html
Type_of_Source_Media: PDF
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 19870101
Ending_Date: 19871231
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: Toscano and others, 1989
Source_Contribution:
This report provided additional sediment samples for the inner-shelf offshore of Assateague and Fenwick Islands. These data were visual textural descriptions in table form and were converted to digital vector data for use in this interpretation.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Berquist, C.R.
Originator: Hobbs, C.H.
Publication_Date: 1986
Title:
Assessment of economic heavy minerals of the Virginia inner continental shelf
Edition: 1.0
Geospatial_Data_Presentation_Form: document
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 86-1
Publication_Information:
Publication_Place: Charlottesville, VA
Publisher: Virginia Division of Geology and Mineral Resources
Online_Linkage: https://www.boem.gov/Non-Energy-Minerals/VA_1986_Berquist.aspx
Type_of_Source_Media: digital vector
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 19850101
Ending_Date: 19851231
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: VAGMR, 1985
Source_Contribution:
This report provided additional sediment samples for the inner-shelf offshore of the Virginia barrier islands. These data were provided in digital vector format (point shapefile) by the Virginia Division of Geology and Mineral Resources, and aided the interpretation qualitatively, since the texture statistics were inconsistent with the 2014 and 2015 samples.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Pendleton, E.A.
Originator: Brothers, L.L.
Originator: Thieler, E.R.
Originator: Danforth, W.W.
Originator: Parker, C.E.
Publication_Date: 2014
Title:
National Oceanic and Atmospheric Administration Hydrographic Survey Data Used in a U.S. Geological Survey Regional Geologic Framework Study Along the Delmarva Peninsula
Edition: 1.0
Geospatial_Data_Presentation_Form: raster digital data
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 2014-1262
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Online_Linkage: https://pubs.usgs.gov/of/2014/1262/
Online_Linkage: https://doi.org/10.3133/ofr20141262
Type_of_Source_Media: digital raster
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20060101
Ending_Date: 20141231
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: NOS survey data report
Source_Contribution:
This report provided high resolution multi-beam bathymetry collected by NOAA and combined and released by USGS to supplement the more widely-spaced interferometric bathymetry lines collected by USGS (FADD 2014-002-FA and FADD 2015-001-FA).
Source_Information:
Source_Citation:
Citation_Information:
Originator: Wells, D. V.
Publication_Date: 2017
Title:
Inventory of Physical and Benthic Habitats and Ocean Resources within the Nearshore Boundary of Assateague Island National Seashore
Edition: 1.0
Geospatial_Data_Presentation_Form: vector digital data
Series_Information:
Series_Name: Natural Resource Technical Report
Issue_Identification: in press
Publication_Information:
Publication_Place: Baltimore, MD
Publisher:
Maryland Geological Survey and Maryland Department of Natural Resources
Online_Linkage: available online following publication
Type_of_Source_Media: digital vector
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20110101
Ending_Date: 20111231
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: MGS and NPS report
Source_Contribution:
This report provided additional sediment samples for the very nearshore along Assateague Island. This currently unpublished report is available by request to the Maryland Geological Survey and contatins digital vector layers with sediment sample statistics. However, the samples lacked carbonate analysis and were only incorporated into the interpretation qualitatively.
Process_Step:
Process_Description:
The texture and spatial distribution of sea-floor sediment were qualitatively-analyzed in ArcGIS using several input data sources (listed in the source contribution), including acoustic backscatter intensity imagery, bathymetry, bottom photographs, and sediment samples. In order to create the interpretation, first a polygon shapefile of the study area was imported to a geodatabase as a feature class (with ArcMap version 10.2.2). Then sediment texture polygons were created using 'cut polygon' and 'auto-complete polygon' in an edit session. In general, polygon editing was done at scales between 1:8,000 and 1:20,000, depending on the size of the traced feature and the resolution of the source data. The following numbered steps outline the workflow of the data interpretation.
1. Backscatter intensity data (available at 1 to 2 meter resolution) were the first input. Changes in backscatter amplitude were digitized to outline possible changes in seafloor texture based on acoustic return. Areas of high backscatter (light colors) have strong acoustic reflections and suggest coarse seafloor sediments like sand with gravel or shell for the Delmarva shelf. Low-backscatter areas (dark colors) have weak acoustic reflections and are generally characterized by finer grained material such as muds and fine sands.
2. The polygons were then refined and edited based on gradient, rugosity (Jenness, 2013), and hillshaded relief images derived from interferometric and multibeam swath bathymetry (available at 0.5 to 25 m resolution). Areas of high rugosity are typically associated with coarser sediments, while smooth, low-rugosity regions tend to be blanketed by fine-grained sediment, and topographic undulations and steep slopes can often be associated with sand ridges and other large bedforms. These bathymetric derivatives helped to refine polygon boundaries where feature changes especially along sand ridge and shoal margins may not have been apparent in backscatter data, but could easily be identified in hillshaded relief and slope changes.
3. After all the seafloor features were traced from the backscatter and bathymetry data, a new field was created called 'Texture'. Bottom photographs and sediment samples were then used to define and populate the sediment texture field for the polygons using a modified Barnhardt and others (1998) sea floor sediment classification. The Barnhardt and others (1998) system is based on four basic, easily recognized sediment units: gravel (G), mud (M), rock (R), and sand (S). The sea floor along the Delmarva Peninsula lacks rock, R, therefore this seafloor interpretation old contains 3 of the 4 Barnhardt primary units. Because the sea floor sediments along Delmarva are often a nonuniform mixture of S,G,and M, the Barnhardt classification is further divided into 12 composite units, which are 2-part combinations of the 3 basic units. The classification is defined such that the primary unit, representing more than 50 percent of an area's texture, is given an upper case letter, and the secondary texture, representing less than 50 percent of an area's texture, is given a lower case letter. If one of the basic sediment units represents more than 92 percent of the texture, only its upper case letter is used. The units defined under the modified Barnhardt and others (1998) classification within this study area include Sg, S, S99, Sm, M, and Ms. Some polygons had more than one sample, and some polygons lacked sample information. For multiple samples within a polygon, the dominant sediment texture was used to classify sediment type (often aided by the 'data join' sediment statistics described in a later processing step). Polygons that lacked sample information were texturally defined through extrapolation from adjacent or proximal polygons of similar acoustic character that did contain sediment samples. Samples with laboratory grain size analysis were preferred over visual descriptions when defining sediment texture throughout the study area.
Typically, features below 5,000 square-meters or less than 50 m wide were not digitized due to positional uncertainty, lack of sample information, and the often ephemeral nature of small-scale sea floor features. Not all digitized sea floor features contained sample information, so often the sea floor texture is characterized by the nearest similar feature that contains a sample. Conversely, sometimes a digitized feature contains multiple samples and not all of the samples within the feature were in agreement (of the same texture). In these cases the dominant sediment texture was chosen to represent the primary texture for the polygon. Sea floor texture can change over small spatial scales, and many small-scale changes will not be detectable or mappable at a scale of 1:25,000. The boundaries of polygons are often inferred based on sediment samples, and even boundaries that are traced based on amplitude changes in geophysical data are subject to migration. Polygon boundaries should be considered an approximation of the location of a change in texture.
Source_Used_Citation_Abbreviation:
Pendleton and others, 2014; Sweeney and others, 2015; NOS survey data report
Process_Date: 2016
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Elizabeth A. Pendleton
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: U.S. Geological Survey
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: 508-548-8700 x2259
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: ependleton@usgs.gov
Process_Step:
Process_Description:
A new field was added called 'Data_quali' as a data interpretation confidence assessment, which describes how confident we are in the interpretation based on the number of input data sources (see the entity and attribute sections for more information on these classes). The following 5 fields contain sediment texture statistics information and were created and populated using a data join function within ArcMap (version 10.2.2). The fields beginning with "Avg_" and the "Count_" field were automatically generated by computing a data join where the 2014 and 2015 USGS sediment sample database with laboratory analysis for clastic and carbonate components (vector points) were joined to the qualitatively-derived polygons. Each polygon was given an average of the numeric attributes of the points (with laboratory grain size analysis) that fell inside it, and the count field shows how many laboratory analyzed points fall inside it. Several fields that were not wanted were deleted after the join. Polygons with a zero count value, meaning there were no sediment samples from USGS surveys in 2014 or 2015 within the polygon, were given a no data value of -999 for the 'Avg_' fields. Sediment samples from the Toscano and others (1989), Virginia Division of Geology and Mineral Resources (1985), and NPS and MGS (2011) report lacked the same laboratory analysis methods and could not be joined with the 2014 an 2015 USGS sample data, or were based on visual textural descriptions. These data were used separately and qualitatively to aid texture interpretation in the absence of USGS samples and were not included in the data join described above.
Three more fields were added. One called 'Biogenic_c' is based on the 'Avg_C_PCF' field and is a description of the amount of carbonate present in the interpreted polygon. Field 'geomorph_f' is a description of the geomorphic region of the interpreted polygon, based on slope measures, and geophysical data properties. The field 'mean_slope' was calculated by zonal statistics, such that the mean slope from the NOAA multibeam bathymetry dataset was included for each interpeted polygon.
Source_Used_Citation_Abbreviation:
Pendleton and others, 2014; Sweeney and others, 2015; Toscano and others (1989); VAGMR (1985); MGS and NPS report (2011)
Process_Date: 2016
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Elizabeth A. Pendleton
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: U.S. Geological Survey
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: 508-548-8700 x2259
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: ependleton@usgs.gov
Process_Step:
Process_Description:
Finally, topology rules were designated within the geodatabase (ArcCatalog version 10.2.2), to make sure that there were no overlapping polygons or accidental gaps between adjacent polygons. The topology error inspector (ArcMap version 10.2.2) was used to find topology errors and fix them. Overlapping polygon and gap errors were fixed. Length and Area fields were generated automatically for all polygons in the geodatabase. The data were then exported to a shapefile and the polygons were reprojected from UTM Zone 18N, WGS84 to GCS WGS84, and the length and area fields were deleted.
Process_Date: 2016
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Elizabeth A. Pendleton
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: (508)-548-8700 x2259
Contact_Facsimile_Telephone: (508)-457-2310
Contact_Electronic_Mail_Address: ependleton@usgs.gov
Process_Step:
Process_Description: An error was fixed in one of the originator names.
Process_Date: 20180129
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: VeeAnn A. Cross
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: 508-548-8700 x2251
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: vatnipp@usgs.gov
Process_Step:
Process_Description:
Added keywords section with USGS persistent identifier as theme keyword.
Process_Date: 20200807
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: VeeAnn A. Cross
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: 508-548-8700 x2251
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: vatnipp@usgs.gov