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

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.