Late Quaternary geomagnetic secular variation from historical and C-14-dated lava flows on Hawaii

A paleomagnetic record of geomagnetic paleosecular variation (PSV) is constructed for the last 4400 years based on 191 sites in historical and C-14-dated lava flows from Mauna Loa, Kilauea, and Hualalai Volcanoes on the island of Hawaii. The features of this new record are similar to those recorded by sediments from Lake Waiau near the summit of Mauna Kea Volcano, but overall mean inclinations for the lava flows (31 degrees to 33 degrees, depending on window size) are nearer the expected dipole-field value (35 degrees) than is that for the sediments (27 degrees). Divergence of the inclination records with increasing age suggests that the Lake Waiau values at depths below 2 m have been affected by compaction-related inclination shallowing, although magnetic terrain effects cannot be ruled out. The rate of PSV indicated by the record presented here is highly variable (<0.5 degrees/century to >20 degrees/century), and a pronounced shift in inclination from 25 degrees to 40 degrees occurred between similar to 1030 and similar to 975 years B.P. Paleomagnetic directions from undated materials can be correlated with our calibrated curve, but the resolution is largely dependent on the PSV rate and data densities for both the reference and unknown directions. The upper part of the Puna Basalt (18 lava flows), previously sampled for paleomagnetism along the northern wall of Kilauea's caldera (Uwekahuna Bluff), was likely deposited sometime between 1030 and 750 years B.P., but the lowest two flows beneath the Uwekahuna Ash (similar to 2100 years B.P.) are correlated with an age of similar to 3034 years B.P. Paleomagnetic data for 54 lava flows of the Ka'u Basalt, exposed in the northwest wall of Mauna Loa's summit caldera (Mokuaweoweo), indicate that they probably accumulated over a relatively short time interval (similar to 200+ years) and are assigned to a 1000 to 1199 year B.P. time window. The mean of ages within this window is similar to 1030 years B.P., but mapping and other C-14 dates indicate that these summit overflows are probably closer to similar to 1200 years B.P. in age.