Optical dating of sediments associated with a fossil moa skeleton near Tauweru, Wairarapa, New Zealand

Abstract

Optical dating was undertaken on the finegrained (4-11 µm diam.) fraction of potassium feldspars extracted from sediments associated with a nearly complete fossil moa skeleton uncovered near Tauweru. The optical ages show that the deposit in which the fossil occurred is younger than c. 45 ka, and no older than 18-22 ka. This result is broadly consistent with the calibrated radiocarbon age estimate for the fossil of 16-22 ka, and suggests that the skeleton is of Ohakean age.Keywords optical dating; moa; Kawakawa Tephra; Wairarapa 102 ± 18 ka (VUW37105), were interpreted to be maximum ages because debris flow deposits are not expected to have received sufficient sunlight exposure before burial (Collen et al. 2000). In order to refine this chronology, a new sample of the debris flow sediment from a correlative section 68 m away was collected for optical dating (sample VUW37101). In addition, two new samples from the overlying loess were also collected. Loess is more suitable for optical (and TL) dating because the associated mineral grains are expected to have received extended, and direct, sunlight exposure during transport. The first of these loess samples (VUW37102) came from the section where the new debris flow sample was collected, while the second loess sample (VUW37103) was collected from another correlative section c. 500 m away. The stratigraphy and location of the samples are shown in Fig. 2.