Planktic foraminiferal and sea surface temperature record during the last 1 Myr across the Subtropical Front, Southwest Pacific

摘要: Planktic foraminiferal faunas and modern analogue technique estimates of sea surface temperature (SST) for the last 1 million years (Myr) are compared between core sites to north (ODP 1125, 178 faunas) south (DSDP 594, 374 present location Subtropical Front (STF), east New Zealand. Faunas beneath cool subtropical water (STW) STF dominated by dextral Neogloboquadrina pachyderma, Globorotalia inflata, Globigerina bulloides, whereas strongly sinistral N. pachyderma (80–95% in glacials), with increased G. bulloides (20–50%) (15–50%) interglacials (beneath Subantarctic Water, or SAW). Canonical correspondence analysis indicates that at both sites, SST related factors were most important environmental influences on faunal composition. Greater climate-related fluctuations occur south. Significant changes through time particularly towards end mid-Pleistocene climate transition, MIS18–15 (e.g., decline crassula STW, disappearance puncticulata SAW), during MIS8–5. Interglacial similar day throughout Myr. To south, interglacial SSTs more variable peaks 4–7 °C cooler than much early middle Pleistocene, but MIS11, MIS5.5, MIS1, estimated have been 2–4 warmer present. These high temperatures attributed southward spread across submarine Chatham Rise, along which appears dynamically positioned For Myr, glacial only 1–2 interglacial, except MIS16, MIS8, MIS6, MIS4–2 when cooler. jetting SAW Mernoo Saddle (across Rise) and/or waning STW current. consistently 10–11 present, currently found vicinity Polar Front. One interpretation is these cold reflect thermocline Circumpolar Surface Water spinning off as an enhanced Bounty Gyre side Rise. gradient has considerably greater 4 °C. During episodes, this region did not migrate northwards, instead there was intensification it (interglacials 4–11 °C; glacials 8–14 °C).