{BC3425A3-BFC2-4451-9574-16435BE1C570}2002102815155500FALSE20031006094939002003100609493900Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 4; ESRI ArcCatalog 8.2.0.700enLake 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. Extensive research has been conducted on Lake Mead, but a majority of the studies have involved determining levels of anthropogenic contaminants such as synthetic organic compounds, heavy metals and dissolved ions, furans/dioxins, and nutrient loading in lake water, sediment, and biota (Preissler, et al., 1998; Bevans et al, 1996; Bevans et al., 1998; Covay and Leiker, 1998; LaBounty and Horn, 1997; Paulson, 1981). By contrast, little work has focused on the sediments in the lake and the processes of deposition (Gould, 1951). To address these questions, sidescan-sonar imagery and high-resolution seismic-reflection profiles were collected throughout Lake Mead by the USGS in cooperation with researchers from University of Nevada Las Vegas (UNLV). These data allow a detailed mapping of the surficial geology 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 that are now submerged below the lake while the margins of the lake appear to be devoid of post-impoundment sediment. The sediment cover along the original Colorado River bed is continuous and is typically greater than 10 m thick through much of its length. Sediment thickness in some areas exceeds 35 m while the smaller tributary valleys typically are filled with less than 4 m of sediment. Away from the river beds that are now covered with post-impoundment sediment, pre-impoundment alluvial deposits and rock outcrops are still exposed on the lake floor.This shapefile indicates the extent of postimpoundment sediment in Lake Mead as mapped by seismic-reflection profiles and sidescan-sonar imagery.David C. Twichell2003sedlimitvector digital dataVeeAnn A. CrossDavid C. TwichellVeeAnn A. CrossStephen D. Belew2003Open-File Report03-320U.S. Geological SurveyWoods Hole Field Center, Woods Hole, MA ground condition1999051420010426CompleteNone planned-114.875551-114.02475636.48504936.012384-114.875551-114.02475636.01238436.485049GeneralArcViewboundslakeOFR03-320Open-File reportpolygonreservoirU.S. Geological SurveyUSGSWoods Hole Field CentersedimentGeneralArizonaBlack CanyonBoulder BasinColorado RiverGregg BasinHoover DamIceberg CanyonLake MeadLas VegasLas Vegas BayLas Vegas WashMojave DesertNevadaOverton ArmUnited StatesVirgin BasinNorth AmericaNONEThe U.S. Geological Survey must be referenced as the originator of the dataset in any future products or research derived from these data.ShapefileDavid C. TwichellU.S. Geological SurveyOceanographermailing and physical address

384 Woods Hole Rd.

Woods HoleMA02543-1598(508) 548-8700 x2266(508) 457-2310dtwichell@usgs.govMicrosoft Windows 2000 Version 5.0 (Build 2195) Service Pack 4; ESRI ArcCatalog 8.2.0.700sedlimit-114.875551-114.02475636.48504936.0123841-114.875551-114.02475636.48504936.0123841enFGDC Content Standards for Digital Geospatial MetadataFGDC-STD-001-1998local timeVeeAnn A. CrossU.S. Geological SurveyMarine Geologistmailing and physical address

384 Woods Hole Rd.

Woods HoleMA02543-1598(508) 548-8700 x2251(508) 457-2310vatnipp@usgs.gov20031006http://www.esri.com/metadata/esriprof80.htmlESRI Metadata ProfileISO 19115 Geographic Information - MetadataDIS_ESRI1.0datasetDownloadable data.0.3230.323These data were prepared by an agency of the United States Government. Neither the United States government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Although all data published in this report have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials.David C. TwichellU.S. Geological SurveyOceanographermailing and physical address

384 Woods Hole Rd.

Woods HoleMA02543-1598(508) 548-8700x2266(508) 457-2310dtwichell@usgs.gov002file://\\REDHOOK\LMofr\data\bounds\sedlimit.shpLocal Area Network0.323ShapefileVectorSimplePolygonFALSE4FALSEFALSEG-polygon4GCS_North_American_1983Decimal degrees0.0000000.000000North American Datum of 1983Geodetic Reference System 806378137.000000298.257222GCS_North_American_19834sedlimitFeature Class4FIDFIDOID400Internal feature number.ESRISequential unique whole numbers that are automatically generated.ShapeShapeGeometry000Feature geometry.ESRICoordinates defining the features.IDIDNumber8Internally generated number.software generatedINTERPINTERPString16character datasetIndicates that the polygon surrounds an area with post-impoundment sediment.David C. Twichell20031006