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

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.

米德湖（Lake Mead）是一座大型跨州水库，坐落于美国内华达州东南部与亚利桑那州西北部的莫哈韦沙漠（Mojave Desert）。该水库于1935年因胡佛水坝（Hoover Dam）的修建完成蓄水，是科罗拉多河上一系列多功能水库中的一员。湖体从大峡谷河口延伸至胡佛水坝所在的黑峡谷，全长183千米，可为美国西南部各州社区的住宅、商业、工业、娱乐及其他非农业用水群体提供水源。水库覆盖区域在水坝修建前已完成前期测绘，但此前鲜有针对蓄水后湖床区域变化情况的研究。为解答这一科研问题，美国地质调查局（U.S. Geological Survey, USGS）联合内华达大学拉斯维加斯分校（University of Nevada Las Vegas, UNLV）的研究人员，在米德湖全域采集了侧扫声呐图像与高分辨率反射地震剖面数据。这些数据可用于精细绘制湖床表层地质图，以及胡佛水坝竣工后在湖中沉积的沉积物的分布与厚度。研究结果表明，蓄水后的沉积物堆积主要局限于原河道与溪床区域，而冲积沉积物与岩层出露区仍分布在远离原河道的湖床之上。