INFILLING RATES OF A STEEPLAND CATCHMENT ESTUARY, WHANGAMATA, NEW-ZEALAND

Apparent sedimentation rates for the Whangamata Harbour, a barrier-enc losed estuarine lagoon on the eastern Coromandel coast of New Zealand, were assessed from three cores taken at representative locations with in the estuary. Palynology was utilised to interpret vegetation change s in the catchment during the last 6,000 years; Pb-210 dating was appl ied to the upper sediment layers to infer changes over the last 100 ye ars, and C-14 dating of shell beds within the estuary was undertaken t o obtain actual dates. apparent sedimentation rates were found to have increased from 0.1 mm yr(-1) in pre-Polynesian times (similar to 700 BP), to 0.3 mm yr(-1) evidently due to Polynesian agricultural practis es, After the 1880's, rates increased dramatically to 11 mm yr(-1), wh ich is attributed to European clearance of the relatively steep catchm ent, and more recently, the development and falling of commercial erot ic forestry. Future rapid estuarine infilling may be offset by acceler ated sea-level rise.