Geologic Map of the Davis Dam SE 7.5' Quadrangle, Mohave County, Arizona, and Clark County, Nevada

The geology of the Davis Dam SE quadrangle reflects the complex interplay of the Colorado River and piedmont drainages that flow from the Black Mountains to join the river. The history of the Colorado River in this area begins with the influx of water and sediment from the north about 5.5 Ma (House et. al., 2002). The first deposits associated with the river contain only locally-derived sediment from the northern part of Mohave Valley. These deposits are succeeded by the fine-grained Bouse Formation, which was probably deposited in a series of lakes as the developing Colorado River spilled over successive divides (Spencer and Patchette, 1997; House et al, 2002; Spencer and Pearthree, 2001). After the Colorado River was integrated through Mohave Valley, it entered a major phase of aggradation which resulted in the accumulation of about 800 feet of river sand and gravel that interfingers with tributary gravel and sand. By 3.3 Ma, the river had begun to incise into the valley fill and tributary deposits were cut into the uppermost part of the old river deposits. The river downcut to a level close to the modern river level by the early Quaternary, but subsequently there were at least 2 major aggradation events during the middle to late Quaternary. The modern channel is quite narrow and most of the historical floodplain has been developed, either as part of Bullhead City or as agricultural fields in the Fort Mohave Indian Reservation.These GIS data adhere to the standard format supported by the US Geological Survey's National Cooperative Geologic Mapping Program (NCGMP09). NCGMP09 recommends distributing geologic map data using the proprietary ESRI File Geodatabase format. We follow this convention, but also provide open-source geojson and csv data as part of this collection.Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu