Absolute Paleointensities From the Gilbert-Gauss to the Upper Mammoth Reversal Sequences in Lavas on the Wai'anae Volcano, Hawaii

University Of Hawaii, Honolulu

Investigators

Abstract

EAR-0207787 Emilio Herrero-Bervera Paleomagnetic directions measured from 240 lava flows in 5 sequences on the island of O'ahu (Hawaii) cover about 0.36 Ma of geomagnetic field changes and include detailed records of the successive Gilbert-Gauss (3.57 Ma), Lower Mammoth (3.33 Ma) and Upper Mammoth (3.22Ma) reversals. Thus, it is clear that proper analysis of these observations require to document the total field vector and thus to conduct an exhaustive study of absolute paleointensity. The objectives of the study are primarily related to the knowledge of the field variations during periods like reversals or excursions but also to the critical time intervals that precede and follow reversals that so far have been only documented from a few sedimentary sections with conflicting observations. The Wai'anae sequences offer the first exceptional opportunity to document field variations over a time period that includes several polarity intervals and thus document the field vector over various time constants. This is a basic condition to extract and bring up significant constraints for theoretical and numerical modeling of the geodynamo. Multiple records offer the best approach to determine the suitability of the field values and the degree of confidence of the results.