A chronology of natural and anthropogenic influences on coastal sedimentation, New Zealand

Abstract

¹⁴C and& ¹³⁷Cs chronologies of sediment accumulation were obtained from five sediment cores taken from Wellington Harbour, New Zealand. A 10,000-year chronology records the Holocene transgression.  European colonisation, and variations in the general sediment accumulation rate caused by earthquake uplift and anthropogenic activity. Rates vary from a high of ~60 to a low of 0.1 mm a ^-1. In general, rates increased at the beginning of the Holocene marine transgression, but by ~5000 yr BP they reached a stable level. Harbour-wide, these rates remained stable until the second half of the 19th century when deforestation by European settlers caused order of magnitude increases in sediment accumulation. In the past 40-80 years rates have increased again as a result of urban growth and river channel management, although the effects are less pervasive. Harbour-wide influences can be placed in two categories, natural and anthropogenic, the latter being recent contributions to a sedimentary regime dominated by the Holocene marine transgression.

Sediment accumulation rates indicate that two major earthquake uplift events had only a local effect on harbour sediments. Anthropogenic influences are considered to be more significant sedimentologically than earthquake activity.