Microwave palaeointensities from Holocene age Hawaiian lavas: Investigation of magnetic properties and comparison with thermal palaeointensities

Abstract

Sixteen C 14 -dated Hawaiian surface lava flows spanning 0–4.5 ka have been investigated using the microwave perpendicular applied field palaeointensity technique and classical thermal Thellier–Thellier palaeointensity technique in parallel. The overall microwave experimental success rate is 63% compared to 59% in the thermal experiments. Nineteen percent of the microwave results are deemed to be first class compared to 52% of the thermal results. High palaeointensities and a large amount of within-flow variation are seen in the microwave results with reliable palaeointensity estimates ranging from 25.10 to 82.94 μ T. These variations do not appear to be systematically related to variations in rock magnetic properties such as mineralogy, grain size, texture or oxidation state. The flow-means from the microwave and thermal studies agree for 9 of the 13 flows that can be directly compared and the average difference between the two techniques is not significantly different from zero. Neither experimental technique produces mean palaeointensities systematically lower or more precise than the other, suggesting that the differences seen are a reflection of natural within-flow variation rather than experimental technique.