Magmatic Mapping of Greer Region, AZ

Field mapping techniques in the south-eastern area of the Springerville Volcanic Field

Presenter: Sara Hawthorne

Presenter Status: Undergraduate student

Academic Year: 22-23

Semester: Spring

Faculty Mentor: Marissa Mnich

Department: Geology

Funding Source/Sponsor: Other

Other Funding Source/Program: EDMap GSA

Abstract:
The Springerville Volcanic Field (SVF) is located in central-eastern Arizona and the region mapped for this project included the town of Greer, AZ and the surrounding area. This monogenetic volcanic field is situated on the edge of the Colorado Plateau, and has an eruption history ranging from 2.1 - 0.3 Ma. The field is over 3000 km2 and erupted mainly basaltic magma, with an overall trend of tholeiitic to alkalic magma from the west to the east. There are approximately 450+ distinct magma flows, primarily from cinder cone eruptions, and the Greer mapping area is located in the southeastern region of the SVF. Mapping of this area was done during the summer of 2022, with the goal of adding this new data onto the larger Dynamic Digital Map (DDM) that was started by Chris Condit in the eighties. A total of 36 distinct flows were identified in the ~25-30 km2 covered in the mapping area. The flows were determined in the field by walking the contact lines between the different flows and making note of the lithological differences in the hand samples collected. The lithologic differences were then compared to and confirmed through geochemistry and analysis of thin sections. This particular mapping area has several regions which would be ideal for paleomagnetic coring and age dating due to the stratigraphic relation of several flows. Since this area is on the east side of the SVF we would expect the ages of the flows to be younger relative to the magma flows dated on the western side of the SVF and geochemically more alkalic than tholeiitic. Several features of note within the field were columnar basalt columns which were situated under several other flows, and a feature that resembled a collapsed lava tube near the middle of the field.