David Gubbins | USGS Science

USGS2009

New and revised 14C dates for Hawaiian surface lava flows: Paleomagnetic and geomagnetic implications

Radiocarbon dates have been obtained for 30 charcoal samples corresponding to 27 surface lava flows from the Mauna Loa and Kilauea volcanoes on the Island of Hawaii. The submitted charcoal was a mixture of fresh and archived material. Preparation and analysis was undertaken at the NERC Radiocarbon Laboratory in Glasgow, Scotland, and the associated SUERC Accelerator Mass Spectrometry facility. The resulting dates range from 390 years B.P. to 12,910 years B.P. with corresponding error bars an order of magnitude smaller than previously obtained using the gas‐counting method. The new and revised 14 C data set can aid hazard and risk assessment on the island. The data presented here also have implications for geomagnetic modelling, which at present is limited by large dating errors.

Hawaii↗

USGS2006

Palaeomagnetic intensities from 14 C-dated lava flows on the Big Island, Hawaii: 0-21 kyr

Thellier–Thellier experiments were carried out on 216 lava samples collected by the USGS on the Big Island. 35 individual flows from the Kilauea, Mauna Loa and Hualalai volcanoes are represented and independent radiocarbon dating of the flows yields absolute ages ranging from 290 to 20,240 yrs old. The palaeomagnetic analysis was carried out at the Laboratoire des Sciences du Climat et de l'Environnement in Gif-sur-Yvette, France, in two custom built, large capacity furnaces that have been specifically designed to minimise oxidation. The temperature steps were adapted to accommodate the characteristic loss of magnetisation at low temperatures seen in the Curie balance results and the use of half-size samples allowed secondary experiments to be carried out where necessary. The strict PICRIT-03 selection criteria were rigorously applied to the data and a high success rate of 53% has been achieved on a sample level. The flow averaged results almost double the existing 14 C-dated palaeointensity dataset for this time window and confirm a period of high intensity over the past 4 kyr preceded by a period in which the dipole moment was weaker. However, the values attained in this study are on average higher than previously published data; reliability of these values is discussed.

Hawai'i↗