A budget for modern‐Holocene sediment on the South Otago continental shelf

Abstract A sediment budget for the South Otago continental shelf and coast, between Nugget Point and Otago Peninsula, reveals modern (post 6500 y) sediment input is dominated by the Clutha River (total 3.14 Mt y ‐1 ; Mt = 10 6 tonnes). Contributions from the Taieri River (0.6 Mt y ‐1 ), the adjacent Southland shelf (0.4 Mt y ‐1 ), and the biogenic production of calcareous shell debris (0.25 Mt y ‐1 ) account for only 28% of the input. About half of the bedload (sand and gravel) reaching the Otago shelf is stored within a large nearshore sand wedge in the protected waters of Molyneux Bay, off the Clutha River. Bedload that escapes storage (1.1 Mt y ‐1 ) is transported north‐eastwards to be deposited on beach and inner shelf environments just north of Otago Peninsula. Suspended load (mud) accounts for over half of the sediment input (2.33 Mt y ‐1 ) and is nearly all transported from the study area to accumulate in north‐easterly shelf and slope depocentres.