Doctoral Defense in Earth Sciences - Sigurveig Árnadóttir

Doctoral candidate:
Sigurveig Árnadóttir

Title of thesis:
Evolution of the Late Miocene Torfufell Central Volcano, North Iceland: Geology, magnetostratigraphy, geochemistry, age and geochronology

Opponents:
Dr. Godfrey Fitton, Professor, Personal Chair in Igneous Petrology, School of Geosciences, The University of Edinburgh, Scotland
Dr. Richard Brown, Associate Professor, Department of Earth Sciences, Durham University, England

Advisor:
Dr. Þorvaldur Þórðarson, professor in Volcanology and Petrology at the Faculty of Earth Sciences, University of Iceland

Other members of the doctoral committee:
Dr. Árni Hjartarson, Geologist, Iceland GeoSurvey Dr. Bjarni Gautason, Geologist and project manager, Iceland GeoSurvey

Chair of Ceremony:
Dr. Guðfinna Th Aðalgeirsdóttir, Professor at the Faculty of Earth Sciences, University of Earth Sciences

Abstract:
Iceland features numerous Miocene and Pliocene central volcanoes that have been excavated by rivers and glaciers, thereby providing excellent windows into their volcanic interiors and opportunities to explore the construction and histories of volcanic edifices. At the same time, addressing the timing of silicic volcanism and magmatism of ancient volcanic centres provides spatio-temporal constraints that can significantly improve our understanding of the geodynamic evolution of Iceland. This thesis aims at detailing the evolution of the Late Miocene Torfufell central volcano and the surrounding area in central North Iceland through detailed geological mapping, paleomagnetic measurements, geochemistry, descriptions of key geological features, and integration with new and existing age data. These observations indicate that the edifice construction commenced at ~7.8-8.0 Ma, with the early stages featuring mafic effusive volcanism producing series of basaltic ā´a lavas and latter stages typified by a broader compositional range, including intermediate and silicic volcanic products. This volcanism was associated with intrusive activity on the form of mafic dykes and silicic plugs. The two volcanic sequences are separated by a peculiar tephra-, smectite and fossil-bearing sediment horizon in several outcrops. Silicic activity – which commenced at approximately 7.12 Ma and lasted ~400,000 years – was characterized by both intrusions and effusive and explosive volcanism and formed a complex in the central zone of the volcano.

The silicic magmatism at the Torfufell volcano took place at a crucial time in the region’s geological history, in a period when a major reorganization of rift segments is inferred and may mark the onset of the presently active rift in North Iceland. The Torfufell central volcano was not among the large Miocene volcanos. However, the mapping indicates a mountain that may have risen some hundred of meters above its surroundings. The volcanic activity continued in the vicinity and little by little it was covered by younger geological formations. Finally its traces disappeared from the surface. Much later, the forces of erosion, especially the Ice Age glaciers, uncovered it again and exposed its interiors.

About the doctoral candidate

Sigurveig Árnadóttir was born in 1978 in Gothenburg, Sweden. She graduated from the natural science program of the Akureyri Junior College in 1998, pursued preparatory studies at the Iceland University of the Arts in 1999-2000 and received a BA degree in Fine Arts from the same university in 2003. Sigurveig completed her BS and MS degrees in geology from the University of Iceland in 2006 and 2008 and received a teacher certification from the University of Akureyri in 2011. After graduating with a BS degree in geology, she worked for two years as a specialist at the Icelandic Construction Industry Laboratories, where she primarily conducted research and quality tests on aggregates for construction purposes, as well as working on her MS project. Sigurveig worked as a geologist at Iceland GeoSurvey (ÍSOR) in Akureyri from 2008 until late March this year. Her primary tasks at ÍSOR regarded borehole geology, geological mapping and project management. She conducted the PhD studies in parallel with her work at ÍSOR. Sigurveig lives in Akureyri with her two kids. Since April this year, she has worked as the project manager of research and maintenance at Akureyri’s local power company.