Using foraminiferal faunas as proxies for low tide level in the estimation of Holocene tectonic subsidence, New Zealand

We use these two foraminiferal proxies, in association with the modern analog technique, to estimate former sea-level heights in four cores of Holocene sediment from two sites in the northern South Island of New Zealand. On the basis of these, we calculate a gradual subsidence rate of 0.55-1.05 m kyr− 1 over the last 4 kyr at Anakoha Bay in the outer Marlborough Sounds, and no significant vertical displacement over the last 6 kyr in Nelson Haven, 70 km to the southwest. The Anakoha Bay results provide independent evidence in support of long-held hypotheses favouring a recent subsidence origin for the deeply-drowned valley systems of the Marlborough Sounds. The Nelson Haven results provide constraints on recent vertical movement across the Waimea-Flaxmore Fault system, which forms the western boundary of the actively uplifting east Nelson mountains.