Page 170 - Caldera Volcanism Analysis, Modelling and Response

The Sierra Madre Occidental, Mexico 145

Figure 1 Index map of the Sierra Madre Occidental (SMO) volcanic province, the Basin and
Range extensional tectonic province, and of Mid-Teriary ignimbrites in Mexico and the SW
United States. Note the superimposed Italy outline for scale comparison, and the location of the
SouthernTransect Project.The SMO and the Basin and Range provinces overlap in space and
time. Some of the most important graben related to the Basin and Range extension are shown
in the ¢gure: B, Bolan ì os; J, Juchipila; A, Aguascalientes. Cities: H, Hermosillo; C, Chihuahua;
Maz, Mazatla Ł n; D, Durango;T,Tepic; Z, Zacatecas; SLP, San Luis Potos|¤. (Modi¢ed from
Aguirre-D|¤az and Labarthe-Herna Ł ndez (2003), with permission from Geological Society of
America).

that this type of caldera structure was related to the eruption of large-volume
ignimbrites of the SMO, during the Ignimbrite Flare-up.

2. The Sierra Madre Occidental Volcanic Province

Sensu strictu, the SMO is the name given to a physiographic province, a long
range bordering the NW coast of mainland Mexico (Raisz, 1964). The same name