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

Metadata:

• Identification_Information
• Data_Quality_Information
• Spatial_Data_Organization_Information
• Spatial_Reference_Information
• Entity_and_Attribute_Information
• Distribution_Information
• Metadata_Reference_Information

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