Seven climatic cycles in New Zealand during the last half-million years

At Upper Hutt, New Zealand (Lat. 41 deg 07' S) there is a sequence of seven loess/soil pairs that represents seven climatic cycles spanning the last half-million years (Fig. 1). Each loess layer accumulated in a dry, cool, possibly periglacial environment with an average temperature about 4 deg C to 6 deg C lower than at present. The five oldest soils (paleosols) are red and each was probably formed in a seasonally humid climate with a hot dry period, with a mean annual temperature above 15.5 deg C and an annual rainfall of more than 1000 mm. Although the present soil and the youngest paleosol are not red at Upper Hutt both are strongly coloured. The sequence, known to be of Brunhes age, is divided by the Mangaroa Ash (340,000 yr B.P.), the Mt Curl Tephra (230,000 yr B.P.) and the Aokautere Ash (Kawakawa Tephra) (20,600 yr B.P.). Correlation with the delta oxygen isotope stages of deep-sea cores indicates that the Aokautere Ash was deposited in ''glacial'' stage 2, the Mt Curl Tephra in ''interglacial'' stage 7,l and the Mangaroa Ash probably near the beginning of ''interglacial'' stage 9. The oldest loess layer is correlated with ''glacial'' stage 14 that began 517,000 years ago; the younger six loess layers are assigned to ''glacical'' stages 12, 10, 8, 6, 4 and 2 respectively, and the six paleosols are assigned to ''interglacial'' stages 13, 11, 9, 7, 5 and 3; the present day soil is assigned to ''interglacial'' stage 1 (Fig. 1). The seven cyclic climatic changes recorded in the Upper Hutt sequence apparently indicate a response to cyclic changes in the earth's orbital parameters and the alternating climatic regime at Wellington supports the suggestion that cyclic climatic changes have been globally synchronous for the past 500,000 years