Geology of a Neogene caldera cluster in the Borgarfjörður eystri–Loðmundarfjörður area, Eastern Iceland

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Steffi Burchardt
https://orcid.org/0000-0002-3316-658X
Birgir Oskarsson
https://orcid.org/0000-0001-5653-670X
Ludvik Gustafsson
https://orcid.org/0000-0002-6582-3206
Sylvia E. Berg
https://orcid.org/0000-0001-9509-8917
Morten S. Riishuus

Abstract

The Borgarfjörður eystri–Loðmundarfjörður area in Eastern Iceland hosts several volcanic centres in a relatively small area. Large volumes of silicic, as well as an unusual amount of intermediate rocks, occur in this area, alongside other volcanic and sub-volcanic features that formed in the Miocene between 14 and 12:2 Ma. We compiled the first comprehensive geological map of the area and summarise the geology based on more than 40 years of fieldwork. We identify regionally extensive marker horizons that comprise intermediate (icelandite) and mafic (olivine basalt and porphyritic basalt) lavas. These marker horizons, along with new paleomagnetic data and some previous radiogenic dating, allow us to bracket a phase of magmatic activity that is one of the oldest in Eastern Iceland. We describe the prominent features of the volcanic centres, including remnants of collapse calderas in Njarðvík, Dyrfjöll, Breðuvík and other ignimbrite-producing vent structures in Kækjuskörð and Herfell. Notably, the area also contains extremely well exposed examples of volcanic vents, cone sheets, and unique caldera-lake sediments. We conclude with open questions to inspire future research on this understudied area.

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How to Cite
Burchardt, S., Oskarsson, B., Gustafsson, L., Berg, S. E. and Riishuus, M. S. (2022) “Geology of a Neogene caldera cluster in the Borgarfjörður eystri–Loðmundarfjörður area, Eastern Iceland”, Volcanica, 5(1), pp. 133–161. doi: 10.30909/vol.05.01.133161.
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Author Biography

Ludvik Gustafsson

retired

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