The Arizona Geological Survey (AZGS) is releasing five new geologic map sheets showing the extent and age relationships of Holocene channel and floodplain deposits along 178 miles of the Verde River of north-central Arizona. A 51-page report accompanies the maps.
AZGS’s mapping team, headed by Joe Cook, constructed geologic strip maps of a two-mile wide swath centered on the river’s active channel and running the length of the river. Geologic mapping was overlain on USGS 7.5 minute, 1:24,000-scale topographic maps. The team used earlier mapping, aerial photography, and extensive field work – establishing GPS stations on approximately one-mile centers along the course of the river – to map modern and recently active channel and floodplain deposits, river terraces and adjacent tributary deposits, eroded older basin deposits, and bedrock.
The geologic maps provide foundational geologic data for deciphering the recent history of the Verde River system. Young Verde River sediments – those deposited over the past 10,000-years -- are subdivided by age and broadly grouped into two classes: channel deposits that comprise mostly sand and gravel; and, overbank floodplain and terrace deposits that consist of sand, silt, and clay with minor gravel.