Late Quaternary paleoclimatic and paleoceanographic change over northern Chatham Rise, New Zealand

Abstract

Four cores from the lower northwestern flank (3010–3726 m water depth) of the Chatham Rise, east of New Zealand, penetrated a post-glacial to last glacial sequence of mainly hemipelagic muds. An accurate time frame for this study is provided by well dated tephra layers and additional 14C-dates. A hiatus is detected at the core tops of all cores studied, with the last 900 to 1000 years missing. Sedimentological and micropaleontological analyses reveal that: 1. (1) Isotope Stage 2 ended ca. 15 000 yr B.P. After a transitional period with a fluctuating composition of planktonic foraminifera assemblages and fluctuating isotopic values more stable post-glacial conditions were established at ca. 10 000 yr B.P. 2. (2) From the end of Isotope Stage 2 to Isotope Stage 1 accumulation rates of diatoms, aeolian quartz and calcareous microfossils decreased stepwise by a factor of 10, 4, and ca. 1.5, respectively, in response to decreasing wind intensities and upwelling. 3. (3) In spite of significant climatic and oceanographic changes from the last Glacial to the Present, the Chatham Rise has remained the northern distributional boundary for endemic subantarctic diatoms. This implies that east of New Zealand, the Subtropical Convergence has remained bound or close to the Chatham Rise during both glacial and post-glacial times. 4. (4) Sediments are slight influences of contour currents or turbidity currents are recognised only in sediments younger than 16 000 years.