Geomagnetic intensity and inclination variations at Hawaii for the past 98 kyr from core SOH-4 (Big Island): a new study and a comparison with existing contemporary data

Abstract

Reliable Thellier–Thellier paleointensity determinations were obtained from 321 (out of 766 examined) samples from the upper 200 units (675 m) of core SOH-4 drilled in the Kilauea volcano. The main trend of the SOH-4 record is a marked decrease from values higher than present in the last 4 kyr to values about 40% smaller from about 20 kyr to the bottom of the sampled interval. Three main lows, coinciding with shallow or negative inclinations, observed in the record were identified with an excursion previously documented in Hawaii, and the Mono Lake and Laschamps events. For the last 15 kyr, the SOH-4 intensities are largely in agreement with the worldwide distribution of volcanic data. In the 15–75 kyr interval, the general lack of volcanic data makes comparison with the SOH-4 data difficult. The SOH-4 record is similar to a composite record of paleointensity largely based on a recent North Atlantic sedimentary paleointensity stack (NAPIS-75). The SOH-4 record is also generally consistent with a record of geomagnetic field intensity obtained from a study of 36 Cl in the GRIP ice core, calculated with the assumption that the production rate of 36 Cl is controlled only by the geomagnetic field. One pronounced discrepancy between the different records is observed around 50 kyr BP, when the sedimentary and cosmogenic based records document high intensities which are not observed in SOH-4. These high intensities are also absent in a recent record based on the analyses of sea-floor magnetic anomalies. The histogram of VADMs obtained from SOH-4 is different from that obtained from the sedimentary or 36 Cl based records and is more skewed than the distribution given by Kono and Tanaka for the last 2.5 million years.