Magnetostratigraphy of deep-sea sediments from piston cores adjacent to the Hawaiian Islands: Implication for ages of turbidites derived from submarine landslides

Abstract

Volcaniclastic turbidite beds in ocean-floor piston cores provide a distal record of large Hawaiian submarine landslides adjacent to the Hawaiian Islands. Cores were obtained north of Oahu, where the Nuuanu and Wailau debris avalanches were derived from Koolau and East Molokai volcanoes, and in the front of the active Hilina slump south of the Island of Hawaii. Magnetic measurements were carried out on the cores to determine turbidite ages. Two magnetostratigraphic models are possible for the cores north of Oahu, using paleontological age markers. Both age models yield turbidite ages that are close to published ages for the source volcanoes. A near-constant sedimentation-rate model indicates ages of about 2 Ma and older than 2.58 Ma for turbidites inferred to record the Wailau and Nuuanu debris avalanches, respectively. These ages are close to the initial-shield building stages of each source volcano. The second model, involving variable sedimentation rates, indicates ages of about 1 Ma and older than 1.77 Ma for these debris avalanches, ages that are close to post-shield stages. The proximal core in the front of the Hilina slump contains only turbidites younger than 0.78 Ma. Turbidites recovered in the distal core are 0.78 Ma or older, predating any published volcano ages for the island of Hawaii, and suggesting sources from volcanoes on other islands.