Tree-ring dating of recent volcanic ash and Lapilli, Mt Egmont

Abstract

Abstract Previous literature on the recent volcanic history of Mt Egmont is reviewed. In the present account nine beds, constituting the volcanic ash and lapilli deposited on the mountain within the last 500 years, are described, mapped, and approximately dated. In stratigraphic sequence these are: Newall Ash, Newall Lapilli, Waiweranui Lapilli, Waiweranui Ash, constituting the Newall Formation dated about A.D. 1604; Burrell Ash, Burrell Lapilli, Puniho Lapilli 1, Puniho Lapilli 2, constituting the Burrell Formation dated about A.D. 1655; and Tahurangi Ash, the sole member of the Tahurangi Formation dated about A.D. 1755. The dating is based on tree-ring counts for the most part, but relative depths of interbedded peat have also been used. Sources of error in tree-ring dating and the problems involved in applying the method to the particular ash beds are discussed in detail. The recent volcanic history of the mountain is outlined. Further study needs to be made of the beds on the west side to elucidate th...