Surficial Sediments of Hamilton Harbour: Physical Properties and Basin Morphology

Abstract

Abstract Studies of surficial sediments of Hamilton Harbour over the past decade have established the sediment-distribution pattern and its temporal and spatial variation. Data are now available for 226 sites sampled during 10 surveys between 1984 and 1993. They include particle size, particle density, water content, shear strength, magnetic susceptibility and sedimentation rate. The basic sediment pattern consists of inshore sands along the undeveloped north and east coasts, disturbed sandy muds along the industrial south shore, and uniform silty sediments in basin depths of 5–25 m. Sediment grain size is dependent upon both water depth and position in the basin, and grain-size statistics for the past decade indicate that the size pattern has been stable over that time span. Limited data on other physical properties give some idea of their scale but not of their areal or temporal trends. Modern sedimentation rates from 210Pb dating range from 0.067 to 0.222 g cm-2 y-1. The average rate is about five times the presettlement rate from radiocarbon dating of long piston cores and is in agreement with sediment-loading data. Reliable data on rates are difficult to obtain because of extensive disturbance of the southern half of the harbour by shipping, dredging and dumping.