Figure 4. A combination of stratigraphic relationships, radiometric age determinations, and paleomagnetic dating is used to delineate the volcanic history of the Springerville volcanic field, AZ (see Figure 1). Here, a geologic map of a small part of the volcanic field illustrates how stratigraphic relationships are used to constrain the age of each eruptive unit. The age range chart illustrates the uncertainty in each age estimate. Stippled pattern shows near-vent facies, lined pattern shows radiometrically dated lavas, arrows indicate lava flow directions, o and y indicate older and younger units where relative ages of adjacent units can be determined.