Cosmogenic dating techniques have been successfully applied to dating of geomorphically-young surfaces, such as glacial moraines, beach terraces, and basaltic lava flows that have intact surface features, and hence have undergone little erosion (e.g. Phillips et al., 1997a and b; Phillips et al, in review, Dunbar and Phillips, 1996; Zreda et al., 1991, 1993; Zreda, 1994; Anthony and Poths, 1992, Laughlin et al., 1994). These techniques rely on measurement of cosmogenic nuclides that begin to build up as soon as a rock is exposed to cosmic rays. Therefore, cosmogenic techniques can be applied to dating of any surface that is composed of material that was not exposed to cosmic rays prior to formation of the surface, and has been exposed more-or-less continuously since. In the case of an extrusive volcanic rock, buildup of cosmogenic nuclides begins when the rock is erupted, so measurement of the ratio of a cosmogenic isotope to a non-cosmogenic isotope can provide an estimate of eruption age (Phillips et al., 1986).
Masters of Science student, Karissa Vermillion, from New Mexico State University received an award for her proposal and will be mentored by Dr. Jake Ross.
The New Mexico Geochronology Research Laboratory (NMGRL) is a participant in the “Awards for Geochronology Student Research” program (AGeS2 ). AGeS2 grants are funded by the National Science Foundation Earthscope program, in conjunction with the Geological Society of America, and are designed to link students with geochronology laboratories to facilitate in depth student understanding of geochronology methods with hands on experience ultimately leading to publication of new data.
Ignimbrite calderas are large volcanic depressions, often 10-20 miles in diameter, that form when a large-volume, gas-charged viscous magma body ejects huge columns of ash that collapse and inundate the surrounding countryside with a thick blanket of welded ash (called ignimbrite) while the shallow roof of the chamber collapses. Caldera-forming eruptions are relatively rare catastrophic events, second only in scale to large asteroid impacts. Deep magma systems that feed these "supervolcanoes" appear to march to the beat of there own drummer; eruptions are both episodic and irregular in timing and intensity.
The Tibetan plateau is a product of the most dramatic tectonic event of recent geological history: the collision of the Indian sub-continent with Eurasia. In spite of the topographic and tectonic implications of the plateau, the mechanisms for its uplift remain controversial. The controversy is in large part a result of poorly constrained uplift history. Types of evidence that have been adduced for the uplift history include paleoecological date, cooling histories of plutonic and igneous rocks, and geomorphic interpretations. Some lines of evidence indicate relatively gradual uplift since the mid-Tertiary, while others support rapid acceleration of uplift during the latest Cenozoic, with the greatest portion during the Quaternary.
Volcanic ash and associated aerosol layers in glacier ice offer a uniquely complete record of explosive volcanism. Investigation of these layers, both in bare ice areas of and in ice cores offers insight into eruptive processes, local and regional ice flow processes, and the impact of eruptions on global systems (climate and ozone depletion). The Antarctic ice sheet is an ideal place to preserve a record of volcanic eruptions. The combination of chemical fingerprinting of glass shards, and chemical analysis of volcanic aerosols associated with tephra layers in Antarctic blue ice allows establishment of a high-resolution chronology of local and distant volcanism that can help understand patterns of significant explosive volcanism, atmospheric loading, and climatic effects associated with volcanic eruptions.
Despite recognition as one the most iconic volcanoes on the planet, there is still much to learn about Valles caldera in north-central NM. A new collaboration between researchers at the Bureau and from UT Austin is seeking to understand the events leading up to supereruptions. In particular, the team is studying the Cerro Toledo Formation, a group of volcanic domes and related ashes that erupted between the large caldera forming events at 1.61 and 1.23 million-years-ago.
A team of scientists from the Bureau of Geology has spent many Antarctic summers sampling layers of volcanic ash trapped between layers of ice to learn about climate conditions that existed at the time of the ice deposition. While the volcanic ash can be dated to constrain the time of deposition, oxygen isotope signatures in the ice reveal clues about temperatures that existed as the layers were deposited.
The Magdalena radial dike swarm (MRDS) is a large diameter (200- 250 km) radial array of basaltic-andesite dikes of Oligocene age broadly focused on the large volume (7000 km3) Socorro-Magdalena caldera cluster (SMCC) of the central Rio Grande rift. Five large overlapping calderas of the SMCC range in age from 32.5 to 24.7 Ma and show a pattern of migrating to the southwest over a distance of about 80 km during a period of about 8 million years.
The Jemez Mountains volcanic field, in northwestern New Mexico, has been active for at least the past 16.5 million years, and has produced a large number of explosive and effusive volcanic eruptions during that time. Volcanic ash from the Jemez Mountains volcanic field provides a temporal record of the young eruptions from the caldera and many such deposits have been recognized in a number locations in New Mexico. The ash is present as thick deposits near the eruptive source, and as thinner deposits interbedded in ancestral Rio Grande river sediments at greater distances from the vent.
