Figure 30. Geologic Map of southeastern Arizona.
The map highlights the shape of the mountain ranges and a few different kinds of rocks, while ignoring many others (shaded gray). The rocks depicted are Precambrian granites, Paleozoic strata, Cretaceous seabed deposits (Bisbee-Mancos seaway), Laramide and Cenozoic granites and volcanics, and the position of graben blocks within the valleys. I indicate the extent of the basal 'chaos' blowout layer for the Tucson Mountain volcano. Also shown are the actual sizes of the original Tucson Mountain and Chiricahua volcano mountains (my guesses). And also the few places when prehistoric but recent earthquakes have broken the land surface, a few in Tucson Valley.
Note the complex array of rocks in the region, frequently with adjacent mountain ranges bearing little resemblance to its neighbors in shape or content. This is an indication of the frequent disturbances, collisions, ripping and tearing actions, and volcanic outpourings that alter the land. Earth is a very active planet when viewed from a longer perspective.
It is curious how the shape of some mountain ranges have a 'wiggle' pattern to them such as the Baboquivaris - Kitt Peak range, seen also on Figure 25, the topographic map. Think of the shatter pattern of a pane of glass dropped onto a concrete floor. This pattern is expressed in different parts of Basin and Range.
There are many things that can be observed on such maps, better on the more complete published versions. For example, along a line starting with the Baboquivaris and extending through Tucson and NE to the Gila Mts beyond Safford, the mountain ranges alternate between mostly granites and volcanics. Why? The issue has been discussed but without resolve. What large-scale item of Earth action are we missing here, what kind of waveform pattern?
- Mts west of Baboquivaris - volcanic
- Baboquivaris - mostly granite
- Sierritas and Tucson Mts - mostly volcanic
- Catalina-Rincons - granite (core complex)
- Galiuros - volcanic
- Pinalenos - granite (core complex)
- Gila Mts - volcanic, for a long ways to the NE
You are not allowed to ask me how this happened. I am a relatively ignorant geologist, poorly educated, not well-traveled, and lacking many perceptive skills.