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

• Published in: Journal of geophysical research. Solid earth 2021-02, Vol.126 (2), p.n/a
• Main Authors: Béguin, Annemarieke, Pimentel, Adriano, de Groot, Lennart V.
• Format: Article
• Language: English
• Subjects: Age; archeomagnetic dating; Archipelagoes; Archives & records; Confidence intervals; Data; Dating; Direction; Earth; Estimates; Geomagnetic field; Geomagnetism; Geophysics; Holocene; Islands; Lava; Lava flows; Magnetic field; Magnetic fields; Magnetic studies; Magnetism; Oceans; Palaeomagnetism; paleointensity; paleomagnetic secular variation; Paleomagnetism; Radiocarbon dating; Radiometric dating; Variation; Volcanic eruptions
• ISSN: 2169-9313; 2169-9356
• DOI: 10.1029/2020JB019745

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. Plain Language Summary The Earth’s magnetic field is highly variable over time and space. Lava flows archive the geomagnetic field upon emplacement and thereby forming an archive of geomagnetic field changes. The Azores Archipelago is located in the mid‐North Atlantic Ocean providing a unique location to study the changes of the Earth’s magnetic field. Here, we present new paleomagnetic data from Pico Island, Azores. We combine the newly derived data with available data from neighboring islands and compose a curve of the changes, for both the direction and the strength of the Earth’s magnetic field over the past 2,000 years. Key Points New paleomagnetic data from Pico Island in the mid‐North Atlantic region Data reveals an inclination low with minimum values of 32° from 900 to 1560 AD We present the first full‐vector paleosecular variation curve for the Azores covering the past 2 kyr, suitable for paleomagnetic dating