LAKEMEAD_INTERP.SHP: Interpretation of the Surficial Geology of Lake Mead Based on Sidescan-Sonar Imagery, Topography and Sediment Thickness

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Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: David C. Twichell
Publication_Date: 2009
Title:
LAKEMEAD_INTERP.SHP: Interpretation of the Surficial Geology of Lake Mead Based on Sidescan-Sonar Imagery, Topography and Sediment Thickness
Geospatial_Data_Presentation_Form: vector digital data
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 2009-1150
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Gelogical Survey, Coastal and Marine Geology Program
Online_Linkage:
<https://pubs.usgs.gov/of/2009/1150/gis/interpretation/lakemead_interp.zip>
Larger_Work_Citation:
Citation_Information:
Originator: David C. Twichell
Originator: VeeAnn A. Cross
Publication_Date: 2009
Title:
Surficial Geology of the Floor of Lake Mead (Arizona and Nevada) as Defined by Sidescan-Sonar Imagery, Lake-Floor Topography, and Post-Impoundment Sediment Thickness
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 2009-1150
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage: <https://pubs.usgs.gov/of/2009/1150/>
Description:
Abstract:
Lake Mead is a large interstate reservoir located in the Mojave Desert of southeastern Nevada and northwestern Arizona. It was impounded in 1935 by the construction of Hoover Dam and is one of a series of multi-purpose reservoirs on the Colorado River. The lake extends 183 km from the mouth of the Grand Canyon to Black Canyon, the site of Hoover Dam, and provides water for residential, commercial, industrial, recreational, and other non-agricultural users in communities across the southwestern United States. The region covered by the reservoir had been mapped prior to construction of the dam, however there had been little study of how the lake-floor region had changed since impoundment. To address this question, sidescan-sonar imagery and high-resolution seismic-reflection profiles were collected throughout Lake Mead by the U.S. Geological Survey (USGS) in cooperation with researchers from University of Nevada Las Vegas (UNLV). These data allow a detailed mapping of the surficial geology of the lake's floor and the distribution and thickness of sediment that has accumulated in the lake since the completion of Hoover Dam. Results indicate that the accumulation of post-impoundment sediment is primarily restricted to former river and stream beds while alluvial deposits and rock outcrops are still exposed on the lake floor away from the former river beds.
Purpose:
This shapefile presents an interpretation of the surficial geology of the floor of Lake Mead based on sidescan-sonar imagery, bathymetry, seismic-reflection data, and geological maps of the areas surrounding the lake.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 19990514
Ending_Date: 20010426
Currentness_Reference:
Ground condition of the originally collected data. The original data collection was over a span of three years with the following specific dates of collection: May 14, 1999 to May 25, 1999; June 1, 2000 to June 6, 2000; April 1, 2001 to April 26, 2001.
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -114.875584
East_Bounding_Coordinate: -114.025408
North_Bounding_Coordinate: 36.485418
South_Bounding_Coordinate: 36.011239
Keywords:
Theme:
Theme_Keyword_Thesaurus: General
Theme_Keyword: CMGP
Theme_Keyword: Coastal and Marine Geology Program
Theme_Keyword: U.S. Geological Survey
Theme_Keyword: Woods Hole Coastal and Marine Science Center
Theme_Keyword: shapefile
Theme_Keyword: interpretation
Theme_Keyword: lake floor geology
Theme_Keyword: ArcMap
Theme_Keyword: USGS
Theme_Keyword: WHCMSC
Theme_Keyword: Surficial geology
Theme_Keyword: Post-impoundment sediment
Theme_Keyword: Sediment distribution
Theme_Keyword: Sediment thickness
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificInformation
Theme_Keyword: inlandWaters
Place:
Place_Keyword_Thesaurus: General
Place_Keyword: Lake Mead
Place_Keyword: Nevada
Place_Keyword: Arizona
Place_Keyword: Colorado River
Place_Keyword: Hoover Dam
Place_Keyword: Boulder Basin
Place_Keyword: United States
Place_Keyword: North America
Place_Keyword: Mohave Desert
Place_Keyword: Virgin Basin
Place_Keyword: Overton Arm
Place_Keyword: Las Vegas Bay
Place_Keyword: Temple Basin
Place_Keyword: Gregg Basin
Access_Constraints: none
Use_Constraints:
The interpretation was completed at map scales less than 1:10,000, and is not intended for use smaller map scales. 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.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David C. Twichell
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: (508) 548-8700 x2266
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: dtwichell@usgs.gov
Native_Data_Set_Environment:
Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.2.6.1500
Cross_Reference:
Citation_Information:
Originator: David C. Twichell
Originator: VeeAnn A. Cross
Originator: Stephen D. Belew
Publication_Date: 2003
Title:
Mapping the floor of Lake Mead (Nevada and Arizona): Preliminary discussion and GIS data release
Edition: 1.0
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 03-320
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage: <https://pubs.usgs.gov/of/2003/of03-320/>
Cross_Reference:
Citation_Information:
Originator: Twichell, D.C.
Originator: Cross, V.A.
Originator: Rudin, M.J.
Originator: Parolski, K.F.
Publication_Date: 2000
Title:
Surficial geology and distribution of post-impoundment sediment of the western part of Lake Mead based on a sidescan sonar and high-resolution seismic-reflection survey
Edition: 1.0
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 99-581
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey Coastal and Marine Geology Program
Online_Linkage: <https://pubs.usgs.gov/of/1999/of99-581/>
Cross_Reference:
Citation_Information:
Originator: Twichell, D.C.
Originator: Cross, V.A.
Originator: Rudin, M.J.
Originator: Parolski, K.F.
Originator: Rendigs, R.R.
Publication_Date: 2001
Title:
Surficial geology and distribution of post-impoundment sediment in Las Vegas Bay, Lake Mead
Edition: 1.0
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 01-070
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage: <https://pubs.usgs.gov/of/2001/of01-070/>

Data_Quality_Information:
Logical_Consistency_Report:
The interpretation was carried out by a single person and is consistent throughout the study area.
Completeness_Report:
This interpretation reflects the complete coverage of the lake floor by the sidescan-sonar imagery.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
The horizontal accuracy is a function of the originally collected sidescan-sonar imagery. Those data were navigated with a P-Code Global Positioning System. In 1999 and 2001 the sidescan-sonar towfish was deployed at approximately the same depth each day, with little variation during the course of the survey. Therefore range-to-fish values were assumed to be consistent and accurate. In 2000, the navigation antenna was placed at the approximate layback position of the towfish, therefore range-to-fish errors were negligible. In all cases, based on the navigation system and towfish configuration, the data are assumed to be accurate to within 20 meters. The interpretation is based on these data and completed at map scales less than 1:10,000.
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: David C. Twichell
Originator: VeeAnn A. Cross
Originator: Stephen D. Belew
Publication_Date: 2003
Title:
Mapping the floor of Lake Mead (Nevada and Arizona): Preliminary discussion and GIS data release
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 03-320
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage: <https://pubs.usgs.gov/of/2003/of03-320/>
Type_of_Source_Media: DVD-ROM
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 19990514
Ending_Date: 20010426
Source_Currentness_Reference:
Ground condition of the originally collected data. The original data collection was over a span of three years with the following specific dates of collection: May 14, 1999 to May 25, 1999; June 1, 2000 to June 6, 2000; April 1, 2001 to April 26, 2001.
Source_Citation_Abbreviation: OFR-03-320
Source_Contribution:
Sidescan-sonar mosaics and the sediment isopach grid. These were used as the basis for the lake-floor geology interpretation.
Process_Step:
Process_Description:
Polygon shapefiles created with ArcCatalog (version 9.3) with the projection defined as Geographic, WGS 84. The interpretation was done in five sections and a separate shapefile created for each area. These sections were Boulder Basin, Virgin Basin, Overton Arm, Temple Basin, and Gregg Basin.
Process_Date: 20090522
Source_Produced_Citation_Abbreviation: BB_interp_g84.shp
Source_Produced_Citation_Abbreviation: VB_interp_g84.shp
Source_Produced_Citation_Abbreviation: OVTN_interp_g84.shp
Source_Produced_Citation_Abbreviation: TB_interp_g84.shp
Source_Produced_Citation_Abbreviation: GB_interp_g84.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David C. Twichell
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: (508) 548-8700 x2266
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: dtwichell@usgs.gov
Process_Step:
Process_Description:
Polygons digitized manually in ArcMap (v. 9.3) at a scale of 1:10,000 or finer using the sidescan-sonar imagery as the base layer. Three different lake floor types were indentified in this process step: alluvial, rock, and sediment. Each polygon was assigned the appropriate name in the INTERPRETA field of the attribute table.
Source_Used_Citation_Abbreviation: bbasinenh_g.tif
Source_Used_Citation_Abbreviation: lvwash_eng.tif
Source_Used_Citation_Abbreviation: vbasineng_g.tif
Source_Used_Citation_Abbreviation: overtonenh_g.tif
Source_Used_Citation_Abbreviation: tempiceenh_g.tif
Process_Date: 20090523
Source_Produced_Citation_Abbreviation: BB_interp_g84.shp
Source_Produced_Citation_Abbreviation: VB_interp_g84.shp
Source_Produced_Citation_Abbreviation: OVTN_interp_g84.shp
Source_Produced_Citation_Abbreviation: TB_interp_g84.shp
Source_Produced_Citation_Abbreviation: GB_interp_g84.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David C. Twichell
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: (508) 548-8700 x2266
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: dtwichell@usgs.gov
Process_Step:
Process_Description:
The surficial geology shapefiles were next overlain on the post-impoundment sediment thickness grid published by Twichell and others (2003) to differentiate the areas of thick sediment (thick sed) and thin sediment (thin sed). The sediment thickness grid was displayed in ArcMap as two categories: areas where sediment was less than 1-m thick and areas where sediment was greater than 1 m thick. The "sediment" polygons were then cut along the boundaries of these two categories and annotated appropriately.
Source_Used_Citation_Abbreviation: isogrdgeog
Process_Date: 20090523
Source_Produced_Citation_Abbreviation: BB_interp_g84.shp
Source_Produced_Citation_Abbreviation: VB_interp_g84.shp
Source_Produced_Citation_Abbreviation: OVTN_interp_g84.shp
Source_Produced_Citation_Abbreviation: TB_interp_g84.shp
Source_Produced_Citation_Abbreviation: GB_interp_g84.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David C. Twichell
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: (508) 548-8700 x2266
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: dtwichell@usgs.gov
Process_Step:
Process_Description:
During the interpretation process there were often adjacent polygons created with the same value. In order to eliminate these artificial bounds, the original shapefiles were copies to new files with "merge" in the filename indicating the process to take place. Each new shapefile was opened in ArcMap 9.3 Editor. Adjacent polygons with the same INTERPRA value were selected - and the "merge" option under the edit menu was selected.
Source_Used_Citation_Abbreviation: BB_interp_g84.shp
Source_Used_Citation_Abbreviation: VB_interp_g84.shp
Source_Used_Citation_Abbreviation: OVTN_interp_g84.shp
Source_Used_Citation_Abbreviation: TB_interp_g84.shp
Source_Used_Citation_Abbreviation: GB_interp_g84.shp
Process_Date: 2009
Source_Produced_Citation_Abbreviation: BB_merge_g84.shp
Source_Produced_Citation_Abbreviation: VB_merge_g84.shp
Source_Produced_Citation_Abbreviation: OVTN_merge_g84.shp
Source_Produced_Citation_Abbreviation: TB_merge_g84.shp
Source_Produced_Citation_Abbreviation: GB_merge_g84.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: VeeAnn A. Cross
Contact_Organization: U.S. Geological Survey
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
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:
Each of these individual shapefiles was copied to a new file using ArcCatalog 9.2. Once this was done, each of these individual shapefiles needed to be quality checked for sliver polygons and overlaps. To help with the overlap polygons, a tool from the ESRI website (Find overlapping polygons) written by Ken Buja was used within ArcMap 9.2. When overlapping polygons were identified, the shapefile was edited within ArcMap 9.2 to adjust the polygons to remove the overlap. Careful visual inspection identified sliver polygons which were removed during the editing procedure as well. The slivers were usually removed by creating a new polygon using the edit tool Auto Complete Polygon. Then this newly created polygon was merged with the appropriate adjacent polygon.
Source_Used_Citation_Abbreviation: BB_merge_g84.shp
Source_Used_Citation_Abbreviation: VB_merge_g84.shp
Source_Used_Citation_Abbreviation: OVTN_merge_g84.shp
Source_Used_Citation_Abbreviation: TB_merge_g84.shp
Source_Used_Citation_Abbreviation: GB_merge_g84.shp
Process_Date: 2009
Source_Produced_Citation_Abbreviation: BB_merge_g84_vac.shp
Source_Produced_Citation_Abbreviation: VB_merge_g84_vac.shp
Source_Produced_Citation_Abbreviation: OVTN_merge_g84_vac.shp
Source_Produced_Citation_Abbreviation: TB_merge_g84_vac.shp
Source_Produced_Citation_Abbreviation: GB_merge_g84_vac.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: VeeAnn A. Cross
Contact_Organization: U.S. Geological Survey
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
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:
Once the individual shapefiles were cleaned, then all the individual files were merged into a single shapefile. This was done using ArcMap 92. - ArcToolbox - Data Management Tools - General - Merge. The order of the inputs was as follows: BB_merge_g84_vac.shp, VB_merge_g84_vac.shp, OVTN_merge_g84_vac.shp, TB_merge_g84_vac.shp, GB_merge_g84_vac.shp The field mapping was left to the default since all the individual shapefiles had the same attributes.
Source_Used_Citation_Abbreviation: BB_merge_g84_vac.shp
Source_Used_Citation_Abbreviation: VB_merge_g84_vac.shp
Source_Used_Citation_Abbreviation: OVTN_merge_g84_vac.shp
Source_Used_Citation_Abbreviation: TB_merge_g84_vac.shp
Source_Used_Citation_Abbreviation: GB_merge_g84_vac.shp
Process_Date: 2009
Source_Produced_Citation_Abbreviation: lakemead_interp_a.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: VeeAnn A. Cross
Contact_Organization: U.S. Geological Survey
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
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:
To ensure complete coverage of the interpretation, the individual shapefiles did have some overlap. Now with the shapefiles merged into a single shapefile, these overlaps had to be removed. This was done in ArcMap 9.2 editor by a combination of adjusting boundaries and deleting the overlapping polygon sections.
Source_Used_Citation_Abbreviation: lakemead_interp_a.shp
Process_Date: 2009
Source_Produced_Citation_Abbreviation: lakemead_interp_a.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: VeeAnn A. Cross
Contact_Organization: U.S. Geological Survey
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
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:
In order to divide the interpretation into sections based on areas of Lake Mead, the interpretation polygon was edited in ArcMap 9.2. The area covered by the sections were based on the original individual shapefile interpretations. First, using ArcCatalog 9.2, the shapefile was copied to a shapefile with a new name. Then, in ArcMap 9.2 editor, polygons in the area of the intended boundary were selected. Using the editing option to cut existing polygons, a polyline was drawn splitting the necessary polygons.
Source_Used_Citation_Abbreviation: lakemead_interp_a.shp
Process_Date: 2009
Source_Produced_Citation_Abbreviation: lakemead_interp.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: VeeAnn A. Cross
Contact_Organization: U.S. Geological Survey
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
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:
In ArcMap 9.2, the text attribute "lake_sect" was added to the attribute table using the attribute table - options - add field. By selecting the polygons in each of the defined areas, this attribute was then edited to reflect the appropriate value. The five defined areas are: Boulder Basin, Virgin Basin, Overton Arm, Temple Basin, and Gregg Basin.
Source_Used_Citation_Abbreviation: lakemead_interp.shp
Process_Date: 2009
Source_Produced_Citation_Abbreviation: lakemead_interp.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: VeeAnn A. Cross
Contact_Organization: U.S. Geological Survey
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
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:
Using XTools Pro, version 5.2, the area of each polygon was calculated. This procedure was performed twice. Once to calculate the area in meters based on the UTM, Zone 11, WGS84 projection. This information populates the utm11_area attribute. The area was also calculated in kilometers based on the UTM, Zone 11, WGS84 projection. This information populates the utmkm_area attribute.
Source_Used_Citation_Abbreviation: lakemead_interp.shp
Process_Date: 2009
Source_Produced_Citation_Abbreviation: lakemead_interp.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: VeeAnn A. Cross
Contact_Organization: U.S. Geological Survey
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
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

Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: G-polygon
Point_and_Vector_Object_Count: 365

Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 0.000001
Longitude_Resolution: 0.000001
Geographic_Coordinate_Units: Decimal degrees
Geodetic_Model:
Horizontal_Datum_Name: D_WGS_1984
Ellipsoid_Name: WGS_1984
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257224

Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: lakemead_interp
Entity_Type_Definition: Surficial geology of Lake Mead
Entity_Type_Definition_Source: USGS
Attribute:
Attribute_Label: FID
Attribute_Definition: Internal feature number.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: Shape
Attribute_Definition: Feature geometry.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain: Coordinates defining the features.
Attribute:
Attribute_Label: Id
Attribute_Definition:
Automatically generated feature ID number automatically populated with zeros
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0
Range_Domain_Maximum: 0
Attribute:
Attribute_Label: INTERPRETA
Attribute_Definition: Bounds of four geologic units mapped on the lake floor.
Attribute_Definition_Source: David C. Twichell
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: alluvial
Enumerated_Domain_Value_Definition:
Areas where pre-impoundment alluvial fan deposits are exposed on the lake floor. These deposits show on the sidescan imagery as moderate backscatter areas that are interrupted by thin sinuous bands of low backscatter (dark tones) shaped in a distributary pattern.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: rock
Enumerated_Domain_Value_Definition:
Areas where rock is exposed on the lake floor. Rock exposures show as either uniform high backscatter (light tones) or alternating bands of high and moderate backscatter (light and moderate tones) on the sidescan imagery.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: thick sed
Enumerated_Domain_Value_Definition:
Areas of the lake floor covered by post-impoundment sediment that is more than 1 m thick. These areas show on the sidescan imagery as low backscatter (dark tones) throughout the lake with the exception of parts of Gregg Basin and the area at the mouth of Las Vegas Wash which are sandy and have a moderate backscatter surface. The thickness of the sediment being greater than 1 m is determined from the seismic-reflection profiles.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: thin sed
Enumerated_Domain_Value_Definition:
Areas of the lake floor covered by post-impoundment sediment that is less than 1 m thick. These areas show on the sidescan imagery as low backscatter (dark tones). The sediment thickness for much of these areas was below the resolution of the seismic-reflection system used, and in these areas the presence of post-impoundment sediment is based on the low-backscatter signature on the sidescan imagery alone.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute:
Attribute_Label: lake_sect
Attribute_Definition: The area of the lake in which the polygon falls.
Attribute_Definition_Source: Data interpreter.
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: Boulder Basin
Enumerated_Domain_Value_Definition: The area of the lake to the west of Boulder Canyon.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: Virgin Basin
Enumerated_Domain_Value_Definition:
The central basin of Lake Mead. Starts at (includes) Boulder Canyon in the west, and extends to the east until it runs into Temple Basin. The northern boundary is marked by the Overton Arm section of the lake.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: Overton Arm
Enumerated_Domain_Value_Definition:
The northernmost portion of Lake Mead, where the Muddy River and Virgin River enter the lake. The southern boundary is marked by the Virgin Basin.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: Temple Basin
Enumerated_Domain_Value_Definition:
Western boundary is marked by Virgin Basin. This area includes Temple Basin as well as the Virgin Canyon area to the east.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: Gregg Basin
Enumerated_Domain_Value_Definition:
The easternmost portion of Lake Mead. The western boundary is at the entrance to Virgin Canyon, and the eastern boundary extends to the limits of the survey. The Colorado River enters Lake Mead to the east.
Enumerated_Domain_Value_Definition_Source: David C. Twichell
Attribute:
Attribute_Label: utm11_area
Attribute_Definition:
Area of the polygon in meters, UTM Zone 11, WGS84 calculated using XTools Pro version 5.2.
Attribute_Definition_Source: Software calculated.
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.1357529
Range_Domain_Maximum: 24226053.1152
Attribute_Units_of_Measure: meters
Attribute:
Attribute_Label: utmkm_area
Attribute_Definition:
Area of the polygon in kilometers, UTM Zone 11, WGS84 calculated using XTools Pro version 5.2.
Attribute_Definition_Source: Software calculated.
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0
Range_Domain_Maximum: 24.226053
Attribute_Units_of_Measure: kilometers

Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David C. Twichell
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: (508) 548-8700 x2266
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: dtwichell@usgs.gov
Resource_Description: Downloadable Data
Distribution_Liability:
Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: WinZip
Format_Version_Number: 9.0
Format_Information_Content:
The WinZip file contains the shapefile for the lake floor interpretation, as well as FGDC compliant metadata.
Transfer_Size: 0.629 MB
Digital_Transfer_Option:
Offline_Option:
Offline_Media: CD-ROM
Recording_Capacity:
Recording_Density: 650
Recording_Density_Units: Mbytes
Recording_Format: UDF
Fees: None.
Technical_Prerequisites:
The user must be capable of uncompressing WinZip files. Once uncompressed, the user must have software capable of displaying ESRI shapefile format.

Metadata_Reference_Information:
Metadata_Date: 20091104
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: VeeAnn A. Cross
Contact_Organization: U.S. Geological Survey
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: Woods Hole Coastal and Marine Science Center
Address: 384 Woods Hole Rd.
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
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time
Metadata_Extensions:
Online_Linkage: <http://www.esri.com/metadata/esriprof80.html>
Profile_Name: ESRI Metadata Profile

Generated by mp version 2.9.6 on Wed Nov 04 14:23:35 2009