Characteristics of sub-surface sediments in southern Stella Passage, Tauranga Harbour

Abstract

The Port of Tauranga is considering port developments that would require capital dredging of a section of the southern Stella Passage to achieve depths comparable to the northern Stella Passage. Seismic profiles, core samples, and CPT data were collected by the University of Waikato and OPUS for the area impacted by proposed development.

The core samples were analysed for sediment texture, including assessment of the fines (silt + clay) content. Four main stratigraphic units were identified from the available data. These were, in order of increasing stratigraphic depth and age: Holocene sand; Pleistocene alluvial fan; Pleistocene organic silt; and Pleistocene terrestrial and shallow marine sand. In general, the fines content increased with depth and age. Younger units thin southwards along Stella Passage, resulting in increasing fines content southwards along the channel.