Henry Mountains

One of my most enjoyable projects was a mapping effort and structural analysis of diorite porphyry intrusions that I conducted while studying with Arvid Johnson at University of Cincinnati in the mid-1980s. I made geologic maps of dikes and sills exposed on Mt Holmes and along Sawtooth Ridge. The most significant finding from that work is that the "stock" at the center of Mt. Holmes is really several cross-cutting sheet intrustions. This was missed by Hunt, who mapped the area in the 1930s, because the rock in the different intrustions is essentially identical, so the intrusions can only be distinguished by tracing narrow, cm-wide contact zones. The implication is that the stocks in the larger of the Henry mountains evolved from myriad sheet intrusions. This interpretation differs from the one proposed by Hunt. I should also point out that the maps were made with a rapidograph pen and colored using a tedious process involving cutting and pasting (literally) patches of stickly mylar film. The maps took a long time to make, but I was pleased to see that they are still in pretty good shape after 20 years.

Near summit of Mt Holmes

Henry Mountains looking north

Google Earth would have been a big help during this project in 1984

Map of Mt Holmes

Map of Sawtooth Ridge

Air photo Sawtooth Ridge

Holmes and Elsworth

My friend Mike Marshall on Mt Elsworth (at the top of this picture) during an early recon trip. Mt Holmes is in the background.