Tuesday, January 6, 2009

Photos from the Black Hills in Southeastern Arizona

One highlight from my holiday break in Arizona was my trip south to Safford to visit David and Adina Morris. David, my mentor in Geology, and Instructor of Geology and Astronomy at EAC, took me out to the Black Hills (the northern end of the Peloncillo Mountains -a Miocene volcanic mountain range) roughly northeast of Safford en route to Morenci. The above photo shows the exposed plumming system of a volcano -a basaltic plug dome.
The photo below -a caliche breccia with basaltic clasts.
An old pumice mine with David in the foreground, for scale :).
A more detailed photo of the ash deposits at the pumice mine. Notice the lighter-colored clast near the bottom. The yellow tint to it is indicative of sulfur-rich groundwater percolation. There was an entire layer of tuff which had been altered by hydrothermal processes and exhibited similar coloration.
A scoria cinder pit. This was once the site of scoria harvesting, most likely for landscape purposes.
A more detailed shot shows the size of some of the basaltic clasts in the scoriacious matrix. Notice the silicic deposits in this clast -amygduloidal scoria.
Amygduloidal basalt, and the single jack. WARNING! Use protective eyewear! (Some nice chalcedony is visible just to the left of the hammer -and all over the photo if you look closely)
Some of the chalcedony amygdules are quite large, and lovely.