Sediment deposition in the central Hauraki Gulf, New Zealand

Florian Boxberg,Bethany Fox,Willem P De Lange,Dierk Hebbeln,Brice Blossier

doi:10.1007/s00367-019-00583-1

Florian Boxberg, Bethany Fox + Show 3 more

Open Access

https://doi.org/10.1007/s00367-019-00583-1

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Abstract

Based on the analysis of 14 short sediment cores, we present new insights into the distribution of surficial sediments in the central Hauraki Gulf, a semi-enclosed coastal embayment on the northeast coast of New Zealand’s North Island. We identify and discuss the effects of interaction of modern wind-generated waves and currents with regard to deposition and reworking of sediments in the Gulf. The modern hydrodynamic regime is controlled by tidal currents, oceanic inflows, and wave-induced currents and it is responsible for a N-S gradient in sediment texture and elemental concentrations in the central Hauraki Gulf sediments. The present-day sediment input into the system is generally low and consists of fine-grained fluvial sediments mostly deposited in the southern study area and comparatively high inputs of relict carbonate material to the northern study sites. The central Hauraki Gulf sediments, which show numerous age reversals in the sedimentary record, can be characterised as palimpsest sediments, as a consequence of continuous reworking and storm-induced sediment transport. In view of the new data, a previously assumed significant post-transgression accumulation of sediments of > 10 m in the central Hauraki Gulf appears to be very unlikely.

Highlights

In recent times, the management, conservation, and sustainable use of near-coastal marine ecosystems have become increasingly important due to the ongoing anthropogenic modification and utilisation of these ecosystems (e.g. Waycott et al 2009)
Through analysis of 14 short sediment cores retrieved from the central Hauraki Gulf, this study aims to (i) improve the understanding of surficial sediment distribution in the central
All sediment cores consisted of greenish-grey, massive silty sands with abundant shell fragments, occurring either as isolated fragments or concentrated in shell beds (Fig. 2)

Summary

Introduction

The management, conservation, and sustainable use of near-coastal marine ecosystems have become increasingly important due to the ongoing anthropogenic modification and utilisation of these ecosystems (e.g. Waycott et al 2009). Two main conceptual models have been proposed: a conceptual model of partly event-driven near-bed sediment transport (Manighetti and Carter 1999), and a numerical model invoking “normal” residual or net circulation patterns in the Gulf as the dominant control (Proctor and Greig 1989). These two models would result in different sedimentation patterns, but the extent to which either is accurate in the central Hauraki Gulf is not known

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