Volcanism & other nerdiness

Glacier-Volcano interactions: Who doesn't love volcanoes? I'm interested in the potential relationships between rapid deglaciation and magma-chamber behaviour. Throughout the Andes, high-relief Quaternary stratovolcanoes support some of the most extensive ice masses in the tropics and subtropics. On the flanks of such volcanoes, we have found lavas interbedded with relict glacial deposits attesting to the potentially dynamic interplay between the forces of glaciation and volcanism. Our goal is to exploit these two depositional records to help establish whether there is a causative link between changes in glacier extent/volume and the remobilisation of magma systems. This is important because glaciers today are receding rapidly, on a global scale, and so understanding the relationship between deglaciation and magmatism is central to assessing the likely ramifications of this recession for volcanic systems worldwide. I am also directly involved in dating relict lava flows with 3He to construct accurate eruption histories. The work is great fun.

Cosmogenic nuclide production rate calibration: Cosmogenic nuclides are formed by interactions between extra-terrestrial radiation and atoms within common minerals (e.g., quartz, pyroxene) forming Earth's surface, and provide a relatively straightforward means to resolving the ages of rock surfaces such as lava flows, landslides, and glacial landforms. Surface-exposure dating has truly revolutionised our understanding of how Earth's surface and its climate have functioned over timescales from decades to millions of years. 

Yet, the cosmogenic toolkit is only as good as the calibration of nuclide production, and a high priority for my team is the refinement of production rates for beryllium-10 and helium-3. Calibrations are made by comparing concentrations of cosmogenic nuclides in minerals to independent ages (e.g., 14C) for those same minerals. Our findings to date indicate that the widely used global average 10Be production rate is several % too high, resulting in apparent exposure ages that are too young and thus erroneous. For our mid-latitude palaeoclimate work, we use the Rannoch Moor production rate (Putnam et al., 2018), which was calibrated against robust 14C ages. But we also have active calibration projects ongoing in Ireland's Burren and the NW Scottish Highlands, so watch this space. 

Various projects included here were/are funded over the years by NSF grant EAR-10-03427 and grants from the Churchill Exploration Foundation (UMaine), Lamont Climate Center, and Geological Survey Ireland, and two Lamont Postdoctoral Fellowships.

Related Publications

Bromley, G., et al., 2019. In situ cosmogenic 3He and 36Cl and radiocarbon dating of volcanic deposits refine the Pleistocene and Holocene eruption chronology of SW Peru. Bull. Volcanol. 81: 64.

Putnam, A., Bromley, G., et al., 2019. An in situ 10Be production-rate calibration from a 14C-dated late-glacial moraine belt in Rannoch Moor, central Scottish Highlands. Quat. Geochr. 50, 109–125. 

Collaborators: Jean-Claude Thouret (Université Clermont Auvergne), Irene Schimmelpfennig(CEREGE, France), Kurt Rademaker (Texas A&M), Claire Todd (CSU, San Bernardino), Margaret Jackson (Trinity College Dublin), Pierre-Henri Blard (CNRS, France), Aaron Putnam & Brenda Hall (UMaine), Rigoberto Aguilar (INGEMMET, Peru), Colin Bunce (Galway)

Students/Postdocs/RAs: Peter Strand & Scott Braddock (UMaine), Matt Hegland (Pacific Lutheran University)