Alluvial-fan deposits in the Basin and Range province in Arizona, California, Nevada, and Utah may be correlated by relative-age criteria. Diagnostic criteria include (1) drainage pattern, (2) incision depth, (3) surface morphology, (4) desert pavement and varnish development, (5) soil-profile development, and (6) morphostratigraphic relations. These criteria allow us to group alluvial-fan deposits into three age classes: young, intermediate, and old. Young fans have a distributary drainage pattern (bar and channel topography), stream incision typically less than 1 m, and an undeveloped to weak soil profile. In contrast, intermediate-age fans have a dendritic to parallel drainage pattern, major channel incision of about 1 to 10 m with undissected interfluves, and weak to strong soil profiles. Old fans retain little of their original surface morphology, have stream incision greater than about 10 m, and typically are cut off from their original source areas by modern drainages. Soils are strongly developed on remnant drainage divides but elsewhere are generally removed by erosion.

Similar sequences of alluvial fans throughout the Basin and Range suggest a regional control over deposition probably related to Quaternary climatic changes. Local variations in sequences may result from other factors which influence deposition, such as lithology and tectonic or other base-level controls. However, fans attributable to these factors are generally not of significance in regional correlation. Relative soil-profile development, morphostratigraphic relations, and absolute dates from numerous Basin and Range localities indicate that most young fans are less than 15,000 years old; intermediate-age fans range from 10,000 to 700,000 years old; and old fans generally exceed 500,000 years in age.