EarthRef.org Reference Database (ERR) -- Shane & Froggatt 1991

New Zealand middle Pleistocene (Castlecliffian) rhyolitic tuffs older than 0.5 Ma are characterised on the basis of glass chemistry and paleomagnetism for the purpose of correlation. Of the tuffs examined, Rewa Pumice (c. 0.74 Ma), Potaka Pumice (c. 0.64 Ma), and Lower Te Muna Tephra (c. 0.75 Ma) are particularly widespread marker horizons. Their proven proximity to the Brunhes-Matuyama paleomagnetic reversal provides a useful framework for correlation and absolute age control between regions in southern North Island-Wanganui, Wairarapa, and Hawke's Bay-and with deep-sea cores from the Western Pacific. The tuffs allow correlation between a diverse range of sedimentary facies including marine, freshwater, and terrestrial, and provide absolute age control for thick sequences of unfossiliferous strata in Wairarapa and Hawke's Bay. The characterisation and correlation of the tuffs has a number of implications for Castlecliffian paleoclimatic, tectonic, and stratigraphic studies. The Rewa Pumice is contained in periglacial facies, and we assign it to oxygen isotope stage 20. Some tuffs in Hawke's Bay contain charcoal and are considered to be derived from ignimbrites. Their presence implies that the main axial ranges in Hawke's Bay were uplifted after 0.6 Ma. Previous lithostratigraphic correlations from the Castlecliffian stratotype along the Wanganui coast to sections across the Wanganui Basin, which contain radiometrically dated tuffs, are not sustainable, suggesting greater facies variations than hitherto assumed. The sequence of strata in the Rangitikei section containing the Rewa and Potaka Pumices is not a correlative of Kaimatira Pumice Sand at the coast section. Previous tuff correlations were made on the basis of age and mineralogy. Only the integrated use of glass chemistry and paleomagnetism allows correlation of tuffs in this time interval.