Surficial geology and analysis of post impoundment sediment of Lake Mohave; interpretation of sidescan sonar and seismic-reflection data
No abstract available.
Arizona, Nevada↗
Geology topics
Kenneth F. Parolski
Publications and source records attributed to Kenneth F. Parolski.
Surficial geology and distribution of post-impoundment sediment in Las Vegas Bay, Lake Mead
Sidescan sonar imagery and seismic-reflection profiles were collected in the northwestern part of Las Vegas Bay to map the distribution and volume of sediment that has accumulated in this part of Lake Mead since impoundment. The mapping suggests that three ephemeral streams are the primary source of this sediment, and of these, Las Vegas Wash is the largest. Two deltas off the mouth of Las Vegas Wash formed at different lake elevations and account for 41% of the total volume of post-impoundment sediment within the study area. Deltas off the other two washes (Gypsum and Government) account for only 6% of the total volume. The sediment beyond the front of the deltas is primarily mud, and it only occurs in valley floors, where it forms a flat-lying blanket that is mostly less than 1.5 m thick. Although a thin layer, the fine-grained sediment accounts for approximately 53% of the total post-impoundment sediment volume of 5.7 x 106 m3 that has accumulated in the study area. This sediment appears to have been transported several kilometers from the river sources by density flows.
Nevada↗
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
Sidescan sonar imagery and high-resolution seismic-reflection profiles were collected in Las Vegas Bay and Boulder Basin of Lake Mead to determine the surficial geology as well as the distribution and thickness of sediment that has accumulated in these areas of the lake since the completion of Hoover Dam in 1935 (Gould, 1951). Results indicate that the accumulation of post-impoundment sediment is restricted to the original Colorado River bed which runs down the axis of Boulder Basin from Boulder Canyon to Hoover Dam, and the old Las Vegas Creek bed that bisects Las Vegas Bay. The sediment cover along the original Colorado River bed is continuous and is typically greater than 10-m thick throughout much of its length with the thickness in some areas exceeding 35 meters. The flat-lying nature of the deposits suggests that they are the result of turbidity currents that flow the length of the lake. The sediment cover in Las Vegas Bay is much thinner (rarely exceeding 2 m in thickness) and more discontinuous. The source for these sediments presumably is Las Vegas Wash and a series of other ephemeral washes that empty into this part of the lake. The presence of sediments along the entire length of the Las Vegas Creek bed suggests that turbidity currents probably are active here as well, and that sediment has been transported from these streams at least 10 km down the axis of this valley to where it enters Boulder Basin. Alluvial deposits and rock outcrops are still exposed on large parts of the lake floor.
Open-File Report↗
High-resolution seismic-reflection profiles from the Duxbury, Massachusetts, area
In August 1980, The U.S. Geological Survey conducted a seismic study (fig. 1) of the harbor and nearshore waters of Duxbury, Massachusetts, aboard the 38' research vessel R/V NEECHO. In all, 18.5 kilometers of high-resolution seismic profiles and sidescan-sonar data were obtained. The systems used included an 80-J minisparker and an EPC-32001 recorder and an EDO Western sidescan system. The navigation was by Northstar LORAN-C and by buoy-to-buoy dead reckoning within Duxbury Harbor. The original records may be viewed at the U.S. Geological Survey, Woods Hole, Massachusetts. Microfilm copies of the seismic profiles can be purchased only from the National Geophysical and Solar-Terrestrial Data Center, U.S. National Oceanic and Atmospheric Administration, NOAA/EDIS/NGSDC, 325 Broadway, Code D621, Boulder, Colorado 80303.
Massachusetts↗