Students Explore  El Pinacate-Southern Arizona Border Region

The photos below illustrate some of my students who have mapped basement rocks in several ranges on opposite sides of the international border east and southeast of  Sierra Los Alacranes.  Also shown are typical outcrops and field relationships.  Work related to the senior thesis of Terry Watkins in Sierra Choclo Duro and Cerro los Ojos is now published in GSA Special Paper #393.  Farther south at Sierra Hornaday and Cerro El Aguila, Miguel Espinoza is finishing up his thesis research on Proterozoic basement exposed at the northwest edge of the Pinacate basalt field .

For additional information and images, please also explore the following links:

Proterozoic Research     Sonora Field Excursions    Student Theses and Publications

Simplified geologic map of the Sonora-Arizona border region directly northwest of the Pinacate basalt field.  This map and detailed unit descriptions are provided in GSA Special Paper #393, Chapter 4.

Entrance to the field area!  Students examine an exposure of 1432 Ma porphyritic granite.

Terry points to xenolith of meta-arkose included in 1645 Ma coarse-granite augen gneiss.

Dr. Nourse rests in pass composed of Paleoproterozoic meta-sandstone.  Cerro Los Ojos is the prominent peak in the distance.

Jon Strom, Meredith Staley, Jeff DeLand, and Terry Watkins stand at the sample locality for the Borderland Quartzite #2.  Arizona's cabeza Prieta Wildlife Refuge is directly behind them. 

Miguel, Ashley, Leianna, John, Pablo, Dr. Nourse, Eli, and Dave pose as Jessica takes their picture in front of Crater Sykes.  On the way to Cerro El Aguila campsite.

Quaternary basalt flow overlies 1432 Ma granite directly north of Mexican Highway 2.

Prominent dikes of 1.1 Ga(?) diabase intrude Proterozoic basement units of Cerro Los Ojos.

Juan Navarro, Dr. Nourse, Allison Wingfield, and Erin Stahl enjoy breakfast at remote camp adjacent to the Late Cretaceous Sierra El Aguila granodiorite.

Terry Watkins sits on outcrop of Paleoproterozoic meta-arkose.  Foliations dip uniformly southeast in this area.

Close-up view of 1645 Ma augen gneiss with arkose xenolith.  One of Dr. Nourse's favorite rocks!

1645 Ma granite augen gneiss with meta-arkose screen.

Miguel, Randal, Terry, Chris, and Shaun take a break on the Arizona side of the border.  Camp is in Mexico beyond the distant range.

Miguel, Randal, Jose, Lauren, and Jessica stand in the wind at the rim of Crater Elegante.  On the way to Puerto Penasco.

Quaternary basalt flow extruded from central vent in Proterozoic basement.  Cerro Los Ojos is the highest peak on the left.

Screen of 1645 Ma alkali granite gneiss within 73 Ma quartz diorite of Cabeza Prieta area.

Xenolith of Paleoproterozoic meta-arkose within 1432 Ma coarsely porphyritic biotite granite