Holocene paleomagnetic secular variation records from the western Equatorial Pacific Ocean

Abstract

We have carried out detailed rock magnetic and paleomagnetic studies on a suite of four deep-sea sediment cores from Indonesia and the Philippine Islands, which form a transect from 6.3°N to 10.6°S. The cores have average sediment accumulation rates of 35–65 cm/kyr that all yield high-resolution paleomagnetic secular variation (PSV) records. The PSV records contain 44 correlatable inclination and declination features that corroborate the individual PSV records and indicate that they are all continuous with no significant stratigraphic gaps. Thirty-four AMS radiocarbon dates provide a high-resolution time stratigraphic framework for the PSV records, which extend from ∼ 0–18,000 yrs BP. These are the first high-resolution Holocene PSV records ever recovered from anywhere on Earth within 17° of the Equator (almost 1/3 of the Earth's surface area). Statistical analysis of the Holocene PSV records indicates that they have Δ I anomalies of − 5° to − 9°, consistent with 5 MA averaged results. The strong similarity in Δ I anomaly pattern of Holocene and longer-term (5 Ma) averaged PSV data suggest that the dynamo process causing the anomaly is largely described by Holocene PSV. By contrast, the Holocene PSV records have VGP angular dispersions that are significantly lower than 5 MA averaged PSV data yet significantly higher than PSV data averaged over only the last few thousand years. This difference indicates that whatever dynamo process causes the overall directional variability of the Earth's magnetic field is not totally described by recent (last few thousand year) PSV or even by late Quaternary (last ∼ 20,000 yrs) PSV.