Zircon record of an ignimbrite flare-up in the footwall of the Snake Range Metamorphic Core Complex, Kalamazoo Tuff, Eastern Nevada USA

This project will investigate the chemical and chronological framework of a ~1 km thick Paleogene volcanic sequence in eastern Nevada, USA. The primary research objective will be to outline the petrogenesis and timescales of magma emplacement and eruption using whole rock geochemistry and zircon geochronology. Results will be used to understand the association of the sequence’s cataclysmic ignimbrite unit, the Kalamazoo welded tuff, to extreme crustal thinning (30-90%) associated with the adjacent Northern Snake Range Metamorphic Core complex. Emplacement of the Kalamazoo volcanic sequence marks the onset of Cenozoic volcanism in the region, and followed a long period of Mesozoic uplift and erosion associated with development of the western Cordilleran margin. This volcanism is associated with widespread ignimbrite flare-up and marks the beginning of regional extensional collapse of the overthickened orogenic wedge across the intermontane west, and specifically in eastern Nevada where the field site for this project is located.

Supervisors

Main supervisor: Ryan Portner, GEO-UiB
Co-supervisor: Leif-Erik Pedersen, GEO-UiB

Project description

The Kalamazoo volcanic group contains an unusually large amount of dacitic lavas that are underlain by felsic tuffaceous units. Limited K-Ar ages from these volcanic units (36-35 Ma) are closely in line with the inferred ages of motion along large-scale detachment faults in the Schell Creek and Snake Ranges (36-28 Ma; Long et al. 2022, Geosphere, and references therein). New U-Pb zircon ages generated during this study will better refine the geochronology of the volcanic sequence and help outline the timescales of magma generation that lead to eruption of the Kalamazoo welded tuff, an ~300 m thick ignimbrite. A detailed sampling strategy of the Kalamazoo welded tuff will help outline internal chemical and chronological stratification associated with its petrogenesis and emplacement.

Looking up at the Kalamazoo columns, ca. 5 m high. Three geologists in field gear standing ion top. — Kalamazoo volcanics. Photo: Ryan Portner / UiB

Field-, lab- and analysis work

The student will travel to Nevada in early summer 2026 to learn the stratigraphy and conduct a robust sampling program. Opportunities to participate with the San Jose State University summer geologic field mapping course* will be explored. Upon returning from the summer field season, the student will prep samples for whole rock geochemistry and zircon geochronology using LA-ICPMS.

Proposed course plan

GEOV242 Petrology (10 ECTS),
GEOV342 Geochemical toolbox (10ECTS)
GEOV302 Data analysis in Earth Science (10 ECTS)
*GEOL129B (equivalent; 10 ECTS),
GEOV251 Advanced structural geology (10ECTS)
GEOV341 Thermochronology and Tectonics (5 ECTS),
GEOV345 Regional Geologic Excursion to Western Norway (5 ECTS).

Last updated: 23.06.2026