Application of paleomagnetic methods to identify and date the Matakaoa submarine avalanche, offshore East Cape, New Zealand

Zeeden, Christian.

Paleomagnetic data from a piston core off the East Cape, North Island, New Zealand, reveal a continuous record of the earth’s magnetic field for the last ca. 200 ka. This record is used to constrain the age of the Matakaoa Debris Avalanche. The pattern of geomagnetic reversals, geomagnetic excursions, the relative paleointensity and the magnetic susceptibility were obtained from the “MD06-3010” core, acquired by the French RV Marion Dufresne. Measurements were carried out in the Paleomagnetic Research Facility of the University of Otago, mainly on a 2G enterprises cryogenic magnetometer. The data acquired from geomagnetic excursions and the relative paleointensity can be combined with tephra correlations to form a consistent age model for the “MD06-3010” core.
Seven geomagnetic excursions are recognised. This is the first time such a complete excursion record is reported for the SW Pacific and it is an important step towards a high-resolution record of the paleosecular variation for the New Zealand region. The relative paleointensity was determined in this study by the ARM method. At ca. 11 m depth, the relative paleointensity loses intensity and amplitude because of the formation of greigite. Above 11 m, the relative paleointensity from this study is consistent with the results from other studies, including the GLOPIS-75 stack. The comparison of the pattern of the relative paleointensity contributes to the age determination of the MD06-3010 core.
The Matakaoa Debris Avalanche is shown to predate 200 ka and an age older than the Mamaku Ignimbrite (ca. 230 ka) is suggested.

xii, 157 leaves : ill., maps ; 30 cm. + 1 CD-ROM (4 3/4 in.)

2006Zeeden