Late Holocene Sedimentation in the Firth of Thames

This study includes an investigation of processes associated with late Holocene mud sedimentation in the southern Firth of Thames, using a number of shallow marine cores. From thesis: Late Holocene mud sedimentation in the southern Firth of Thames has been described from analysis of a number of shallow marine sediment cores. Three distinct lithofacies are distinguished on the basis of sediment texture and mineralogy. A laterally extensive greenish grey mud, tyically bioturbated and massive, with sporadic uncorrelatable interbedded shell layers is termed the Firth of Thames mud facies. Nearer shore sediments are usually coarser and are subdivided into two facies: a siliciclastic sand facies (river mouth sand facies) comprising more prominent interbeds of sand in mud and associated with sedimentation of the mouth of the Waihou River; and a mixed terrigenous-carbonate gravel facies (delta fan gravel facies) associated with deposition on small delta fans adjacent to streams draining the Coromandel Range. The areal distribution of all three facies over the late Holocene has been controlled largely by northward progradation of the coastal Hauraki Lowland associated with the rapid sediment infilling of the Firth of Thames since sea level reached its present height 6500 y. B.P. From seismic evidence the Holocene muds are up to 10 m thick. The cores in this study penetrated only to 5.5 m sub-bottom depth and yielded an oldest radiocarbon age of 5000 y B.P. The age data indicate an average rate of offshore vertical sediment accumulation of 1.5 mm/y.

Analysis of shallow marine cores. Physical, mineralogical and radio-carbon dating anlaysis. Interpretation of development of area.

Firth of Thames

Study completed in 1990

Collection of shallow marine cores.

Unknown

Thesis freely available in University of Waikato library. No confidentiality

Study completed.