Report on geology of the San Pedro

Geology and Geomorphology of the San Pedro River

Geology and Geomorphology of the San Pedro River

A new Special Paper by the Arizona Geological Survey details the geology and geomorphology of the San Pedro River. The report’s 15 illustrations include annotated photographs, geologic maps and cross sections, and comparative photographs that evince changes in river channel morphology over the past years and decades.

The perennial San Pedro flows over one-hundred miles north-northwest from the US-Mexico frontier to its confluence with the Gila River near Winkelman, Arizona. Babocomari River and Aravaipa Creek are its two major tributaries. The San Pedro drains an area of about 4,720 sq. miles – nearly the size of Connecticut. During the late 1800’s and early 1900’s the San Pedro River downcut dramatically, leaving the former floodplain 5 to 30 feet above the modern channel.