Paleomagnetic study of the ages of lavas on the island of Lanai'i, Hawai'i

Abstract

A detailed paleomagnetic study of tholeiitic basaltic of eight sites drilled from Kaumalapau Harbor, Manele Bay and Maunalei Gulch areas was conducted to investigate the volcanic evolution of the island of Lana'i. Stepwise alternating field (AF) demagnetizations accompanied by investigations of rock magnetic properties such as low-field susceptibility versus temperature (k–T) and saturation isothermal remanent magnetization (SIRM) indicate that the characteristic remanent magnetization (ChRM) is primarily carried by Ti-poor magnetite. Demagnetization experiments have identified eight mean flow directions characterized by negative polarities. Our paleomagnetic results, along with the radiometric age determinations of the lavas in question indicate that the tholeiitic flows that formed the Lanai volcano were erupted very rapidly and only during the Matuyama Polarity Chron (0.780–2.58 Ma) and not during the Brunhes Chron (0–0.78 Ma), as reported previously for the K–Ar dated lavas in the Maunalei Gulch.