I am have recently completed a Ph.D. in the Geological Sciences department at Oregon State University where I used various geochemical techniques to help the world with its volcano problems. With assistance from my advisor, Dr. Adam Kent, I completed three projects related to subduction zone volcanism at three different continental arcs (see below). In addition to research, I have taught introductory geology courses at OSU, Linn-Benton Community College and Yakima Valley Community College. The image to the right is the highest volcano in Bolivia, volcán Sajama, taken in March, 2010.
My most recent research concerns the magmatic evolution of the extinct Volcán Tunupa, located between the Salar de Coipasa and the Salar de Uyuni, two of world's largest salt flats. This glacially-dissected volcano is in the middle of a geologically interesting area north of the APVC and east of the modern volcanic arc. This region of volcanism is poorly understood and different hypotheses for the cause of magmatism have been suggested. One of the most interesting hypotheses is that of delamination, or lithospheric foundering. This process involves large portions of the lower lithosphere breaking away and dripping into the underlying lithosphere. This process is thought to occur following phase changes related to episodes of intense crustal thickening, which largely took place in the Eocene, in the central Andes and is related to the high altitudes of the Altiplano. I am examining the timing and geochemical signatures of eruptions from Tunupa and will weigh in on the delamination question.
PHOTOS: Tunupa with Nestor, BJ, and Victor (April, 2010).
PHOTOS: Tunupa with Alvaro and Alejandro (May, 2010).
A previous project involved describing the timing and distribution of some very large ignimbrites that erupted over the last 10 million years in the central Andes of South America. The research was focused in Bolivia, where little previous work had been performed. The ignimbrites erupted from a cluster of supervolcanoes in a region known as the Altiplano-Puna volcanic complex (APVC), which also spans into Argentina and Chile. Although another large eruption is still possible, the prodigious magmatism of the APVC appears to be waning. The melting mechanisms behind the cluster and the reason behind the 10 million year duration remain a mystery, but may be related to lithospheric foundering. The study, which included researchers from OSU, University of Wisconsin - Madison, Northern Arizona University, and the Universidad Mayor de San Andres in La Paz, Bolivia, combined field work with Ar-Ar ages of 60 samples to reconstruct the APVC ignimbrite eruptive history within Bolivia.
Publication reference
Salisbury, M., Jicha, B., de Silva, S., Singer, B., Jiménez C., Ort, M., 2010, 40Ar/39Ar chronostratigraphy of Altiplano-Puna Volcanic Complex ignimbrites reveals the development of a major magmatic province, in press , GSA Bulletin.
PHOTOS: Field work in Bolivia, 2006
Sumatra deep-sea tephras
A recently published tephra correlation study examined ash layers sampled from deep-sea cores taken along the Sunda trench off the coast of Sumatra, Indonesia. For this study I worked closely with Jason Patton , a Ph.D. student in the College of Ocean and Atmospheric Sciences (COAS) here at Oregon State University. Jay focused on the stratigraphical details (including carbon-14 age determinations) while I looked at the geochemistry of glass shards within the tephra to correlate the layers between the cores and to look for on-land eruptive sources. The image on the right shows the core locations where the tephra layers were found.
With a lot of help from advisor Dr. Wendy Bohrson of CWU and Dr. Michael Clynne of the USGS, I studied the physical and chemical processes of magma mixing prior to the 1918 eruption of Lassen Peak in California. The image to the right shows a plagioclase crystal and corresponding chemical composition analyzed using an electron microprobe at Oregon State University. We also analyzed trace element concentrations and Sr-isotope ratios to help determine the growth history of individual plagioclase grains. The analyzes and interpretation by Dr. Paul Hoskin (now at the University of Auckland) and Dr. Frank Ramos (now at New Mexico State University) contributed significantly to the paper
Publication reference
Salisbury, M., Bohrson, W., Clynne, M., Ramos, F., Hoskin, P., 2008, Multiple Plagioclase Crystal Populations Identified by Crystal Size Distribution and in situ Chemical Data: Implications for Timescales of Magma Chamber Processes Associated with the 1915 Eruption of Lassen Peak, CA, Journal of Petrology, v. 49, no. 10, p. 1755-1780.
