Recent aggradation in Whangaehu Valley, Central North Island, New Zealand

Abstract Alluvial deposits and paleosols containing radiocarbon dated trees show that since deposition of Taupo Pumice Alluvium in Whangaehu Valley there have been repeated phases of aggradation and soil formation of the lower terraces. The alluvium has emanated principally from volcanic eruptions and lahars in the southern central volcanic zone and appears to have accumulated rapidly. The last recorded event in the sequence of deposits formed a terrace about 19 m above the present river level and is shown, by radiocarbon dating of a small tree in the underlying paleosol, to have been deposited about (NZ1363) 407 ± 70 yr B.P. Formation of Karapoti gravelly sand, the present soil on the terrace, probably commenced about this date.