{
    "tag": 21132,
    "title": "Chirp Seismic Survey Tracklines - Lake Mead 2001",
    "pubdate": "2003",
    "sername": null,
    "series_name": null,
    "issue": "02-478",
    "publish": null,
    "publisher_name": null,
    "onlink": "https:\/\/cmgds.marine.usgs.gov\/catalog\/whcmsc\/open_file_report\/ofr2002-478\/seisnav_01.faq.html",
    "format": null,
    "email": null,
    "descript": "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. 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.",
    "lang": null,
    "journal": null,
    "pwid": null,
    "originator": [
        {
            "name": "Twichell, David C.",
            "role": "Author"
        },
        {
            "name": "Cross, VeeAnn A.",
            "role": "Author"
        }
    ],
    "index_term": [
        {
            "thcode": 2,
            "code": "474",
            "name": "geospatial datasets",
            "scope": "Collections of related digital information that are geographically referenced."
        },
        {
            "thcode": 2,
            "code": "707",
            "name": "marine geophysics",
            "scope": "Branch of earth sciences concerned with the physical processes of the oceans and continental margins.  We include here studies of large bodies of brackish and fresh water, such as lakes and rivers."
        },
        {
            "thcode": 2,
            "code": "2078",
            "name": "navigational data",
            "scope": "Geospatial data indicating the locations of instruments, vessels, aircraft, or other vehicles used to collect scientific observations.  These data include horizontal coordinates in sequence, and may include time or vertical position."
        },
        {
            "thcode": 2,
            "code": "1045",
            "name": "seismic reflection methods",
            "scope": "Geophysical technique to study the subsurface of the earth using sound waves induced by explosives, vibrating devices, or percussive equipment.  The reflections of the sound waves from the boundaries of different rocks are measured."
        },
        {
            "thcode": 15,
            "code": "008",
            "name": "geoscientificInformation",
            "scope": "Information pertaining to earth sciences, for example geophysical features and processes, geology, minerals, sciences dealing with the composition, structure and origin of the earth's rocks, risks of earthquakes, volcanic activity, landslides, gravity information, soils, permafrost, hydrogeology, groundwater, erosion"
        },
        {
            "thcode": 15,
            "code": "012",
            "name": "inlandWaters",
            "scope": "Inland water features, drainage systems and characteristics, for example rivers and glaciers, salt lakes, water utilization plans, dams, currents, floods and flood hazards, water quality, hydrographic charts, watersheds, wetlands, hydrography"
        }
    ],
    "place_term": [],
    "image": [],
    "fan": []
}