GEOLOGY OF THE COCONINO PLATEAU, NORTHERN ARIZONA

Many people have either driven or taken the public train on the eastern edge of the Coconino Plateau, but very few people venture onto or across this very flattish terrain immediately south of the Grand Canyon.

In 1973, along with another geologist Michael J. Abrams, we spent nearly a year field mapping this plateau. We used a sturdy truck (via the Jet Prolusion Lab) to get around because the roads there are all rough dirt roads that typically could be difficult to navigate. We camped out for two weeks at a time, and then retreated, for a week,  to civilization. Mike drove back to Pasadena, California and I drove to Albuquerque. Via our field work, we created a geologic map of the Coconino Plateau, whose northern boundary is the edge of the Grand Canyon. The southern edge is many miles away. In between is an area home to a few cattle ranches. This plateau has only sparse vegetation (i.e., very few trees!).

We mapped the geology of the area by using standard geologic field procedures (i.e., feet on the ground and a map board in hand). In doing so, we followed the famous geologic dictum, which is “go and see.” We acquired “ground truth” of an area (as big as some states) that had never been geologically mapped in any kind detail. In addition to using the standard “air photos,” we had high-altitude photos taken by means of satellite[ ERTS = Earth Resources Technology Satellite] imagery. It took nine months of field work, and after we completed our traditional-style of mapping, we compared our geologic map with what could be discerned via satellite photography. These latter photos were enhanced by highly skilled computer-program specialists at the Jet Prolusion Laboratory in Pasadena, California. No one had every done such a detailed comparison before. Of course, nothing beats actually “ground truth” collected by field geologists, but some of the computer-enhanced images did reveal better evidence of features that we could not readily detect via standard geologic mapping (for example: poorly exposed faults and some potential ground-water zones).

Reference: 

Goetz, A.F.H. and seven other authors (including R.L. Squires and Mike Abrams). May 15, 1975. 188 pp. Technical Report 32-1597. Application of ERTS Images and image processing to regional geologic problems and geologic mapping in northern Arizona. 

This entire document can be viewed, for free, online at ntrs.nasa.gov

Figure 1. Overview of the Coconino Plateau, northern Arizona. The area at the top of this image is the Grand Canyon.

Figure 2. Ground view of a portion of the Coconino Plateau (1973).

Figure 3. Field vehicle loaned to us by the Jet Prolusion Lab (1973).

Figure 4. Geologic map of Squires and Abrams (published in 1975, see above).

Figure 5. Stratigraphic column of the rock layers exposed in the area mapped by Squires and Abrams (see Fig. 4 above). The colors (e.g., blue, green, orange, red, etc.) on that geologic map in Fig. 4 correspond to their respective stratigraphic unit (e.g., red = basalt flows), shown in the explanation (= the vertical row of the small boxes on the right side of Fig. 5).