Full-Vector Paleosecular Variation Curve for the Azores: Enabling Reliable Paleomagnetic Dating for the Past 2 kyr

Annemarieke Béguin*, Adriano Pimentel, Lennart V. de Groot

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

For archeomagnetic dating, high-quality directional and intensity paleosecular variation curves are needed. The Azores Archipelago in the mid-Atlantic Ocean provides a wealth of volcanic products erupted during the Holocene, making it an ideal location to (1) gather paleomagnetic data from well dated lava flows and (2) construct a paleosecular variation (PSV) curve that enables paleomagnetic dating of volcanic products with unknown age. Here, we present new full-vector paleomagnetic data from Pico Island, and combine the new data with existing data from neighboring islands to construct a new full-vector PSV curve for the Azores Archipelago. An extensive rock-magnetic study underpins the quality of our paleomagnetic carriers. From Pico Island, we obtained 21 new mean site directions; and 15 paleointensity estimates with the multimethod paleointensity approach from 12 sites, the age was known for 14 and 10 sites, respectively. By bootstrapping the non-Gaussian uncertainty estimates of the radiocarbon age calibrations and the confidence intervals associated with the direction and paleointensity estimates, we produce the first full-vector PSV curve with confidence intervals for the Azores covering the past 2 kyr. The PSV curve reveals a period of low inclination between ∼900 and 1560 AD, with minimum values of 32°. The potential of our new full-vector PSV curve is demonstrated by successfully dating five lava flows from Pico Island.

Original languageEnglish
Article numbere2020JB019745
Pages (from-to)1-18
Number of pages18
JournalJournal of Geophysical Research: Solid Earth
Volume126
Issue number2
DOIs
Publication statusPublished - Feb 2021

Bibliographical note

Funding Information:
Liz van Grinsven, Anna Gülcher, and Flor Wassing are gratefully acknowledged for their assistance in the field and carrying out parts of the measurements under our supervision as part of their BSc graduation projects. Matthijs Bloem is also gratefully acknowledged for preparing the SEM images and carrying out the thermal Thellier measurements under our supervision for his MSc graduation project. Andrew J. Biggin is acknowledged for the supervision on the microwave Thellier experiments. Wout Krijgsman is thanked for his help in the field. We thank J. C. Nunes for providing information about the radiocarbon ages. L. V. de Groot acknowledges NWO VENI grant 863.15.003. We thank F. Javier Pavón‐Carrasco and Anita Di Chiara for their constructive comments that significantly improved the manuscript and PSV curve. The paleomagnetism.org file with the directional data can be found in the supporting information ( S4 ). The data used for the construction of the PSV curves are provided as table in the supporting information ( S5 ). The PSV curves can be found in the supporting information ( S8 ). All new geomagnetic data for Pico Island can be found in the MagIC database repository at https://earthref.org/MagIC/16776 .

Publisher Copyright:
© 2020. The Authors.

Funding

Liz van Grinsven, Anna Gülcher, and Flor Wassing are gratefully acknowledged for their assistance in the field and carrying out parts of the measurements under our supervision as part of their BSc graduation projects. Matthijs Bloem is also gratefully acknowledged for preparing the SEM images and carrying out the thermal Thellier measurements under our supervision for his MSc graduation project. Andrew J. Biggin is acknowledged for the supervision on the microwave Thellier experiments. Wout Krijgsman is thanked for his help in the field. We thank J. C. Nunes for providing information about the radiocarbon ages. L. V. de Groot acknowledges NWO VENI grant 863.15.003. We thank F. Javier Pavón‐Carrasco and Anita Di Chiara for their constructive comments that significantly improved the manuscript and PSV curve. The paleomagnetism.org file with the directional data can be found in the supporting information ( S4 ). The data used for the construction of the PSV curves are provided as table in the supporting information ( S5 ). The PSV curves can be found in the supporting information ( S8 ). All new geomagnetic data for Pico Island can be found in the MagIC database repository at https://earthref.org/MagIC/16776 .

Keywords

  • archeomagnetic dating
  • paleointensity
  • paleomagnetic secular variation
  • paleomagnetism

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