Marine sedimentology and deep sea environments.

Quaternary deep sea sediment cores were collected from Lord Howe Rise; Tasman Sea in February 2006 during a survey of Capel and Fairway basins aboard the R. V: Marion Dufresne (MD Leg 153). Examination of three of these cores (MD060-3032, 3033 & 3036) identified numerous, thin (mm thick), green and grey laminations through the sediment. A thick (40cm) green unit was also observed in one of the cores (MD06-3032). The thin green laminae are interpreted as diagenetically altered volcanic ash layers from volcanic centres in the southwest Pacific, due to the high abundances of the smectite montmorillonite. The grey coloured laminae are an indication of diagenetic alteration of detrital organic material in the sulphate reducing redox zone of the marine sediment, due to their dark grey colour, low clay mineral content and recrystallisation of biogenic carbonate (identified by scanning electron microscopy). The thick green unit is interpreted to be a tephra related to a significant volcanic eruption in the region, most probably from the Taupo Volcanic Zone (TVZ), New Zealand. Approximation on the timing of this event compares with the Potaka Tephra (1.0 Ma) of the TVZ.