Distal records of Katla’s explosive past: Ocean-rafted pumice in raised shorelines on Varanger Peninsula, Northern Norway

• Main Authors: Zernack, A., Jørgensen, E., Romundset, A., Newton, A.
• Format: Conference Object
• Language: English
• Published: 2023
• Subjects: Lofoten; Norway; Katla; Iceland; North Atlantic; Northern Norway; Varanger
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5018693

Ocean-rafted pumice is found on modern and paleo-beaches across the North Atlantic and elsewhere. While not as accurate as tephrochronology, ocean-rafting events can be fingerprinted to their volcanic source and used to date sedimentary records and landforms, including raised shorelines. They also provide records of large explosive eruptions that might not be preserved near the volcano due to extensive erosion or a submarine volcanic source and as such can be used for petrological and geochemical investigations. Our study focuses on the Varanger Peninsula in Norway in order to establish a detailed distal record of large silicic eruptions from Katla Volcanic Centre in Iceland. Here, strong Holocene uplift rates and sea-level changes have built a unique succession of fossil beaches up to the marine limit that are covered in little vegetation. We found that pumice was abundant on specific paleo-shorelines and in defined geomorphic settings but absent from older beach ridges, with the distinct mid-Holocene transgression high-stand accumulating the largest variety of pumice types and clast sizes. Initial EMP glass analyses of pumice samples allowed correlations with the Víkurhóll Pumice and individual or groups of SILK (silicic to intermediate Katla) tephras. Our ongoing work aims at providing further insights into the nature and frequency of Holocene silicic eruptions from Katla while also improving age control for existing relative sea-level curves. In addition, the acquired beach pumice data will be integrated with compositional information of archaeological pumice pieces from an ongoing excavation on Lofoten to contribute coarse age frameworks for this important context.