Quaternary isotope stratigraphy of DSDP Hole 90-593 from the Challenegr Plateau, South Tasman Sea

A moderate-resolution isotope stratigraphy (with an average of one sample per 17,500 yr.) derived from the benthic foraminifer Uvigerina (or Cibicides), the planktonic foraminifer Globigerina bulloides, and calcareous nannofossil concentrates is presented for the entire Quaternary (and latest Pliocene) section of mid-upper bathyal calcareous oozes from DSDP Site 593, western Challenger Plateau, south Tasman Sea. Superimposed on a trend of gradually increasing average delta18O values through the Pleistocene, reflecting the progressive buildup of polar ice sheets, is a record of highfrequency but generally low amplitude (0.5-1‰) isotope fluctuations in the early Quaternary (1.9-1.0 m.y.), followed by a greatly increased intensity (1.5-2.0 ‰) of glacial-interglacial fluctuations during the late Quaternary (< 1.0 m.y.). The standard late Quaternary isotope stages 1 to 24 are mainly resolvable. Significant excursions in both delta18O and delta13C values at various times during the Quaternary are suggested to be due to periodic, fundamental changes in ocean circulation properties over the plateau. For example, intensified upwelling of Antarctic Intermediate Waters during several glacial periods is indicated by the convergence of benthic and planktonic foraminiferal delta18O data, and productivity variations may account for certain delta13C spikes in the record. With increasingly higher resolution analysis this core will provide a useful Quaternary isotope reference section for southern temperate waters in the southwest Pacific, centered on New Zealand.本研究报道了一套中等分辨率同位素地层学数据（平均采样间隔为17500年），其数据取自塔斯曼海西部挑战者高原深海钻探计划（Deep Sea Drilling Project, DSDP）593站位的中-半深海钙质软泥完整第四纪（及上新世晚期）剖面，组分涵盖底栖有孔虫（benthic foraminifer）Uvigerina属（或Cibicides属）、浮游有孔虫（planktonic foraminifer）Globigerina bulloides以及钙质超微化石浓缩样。 更新世时期，氧同位素δ¹⁸O平均值呈逐渐升高的趋势，该趋势反映了极地冰盖的逐步发育；在此背景之上，早第四纪（1.9~1.0 Ma）记录了高频但振幅普遍较低（0.5~1‰）的同位素波动，晚第四纪（<1.0 Ma）的冰期-间冰期波动强度则大幅提升至1.5~2.0‰。标准晚第四纪同位素阶段1至24大多可被分辨。 第四纪不同时期出现的δ¹⁸O与δ¹³C显著偏移，被认为与挑战者高原海域海洋环流性质的周期性根本性变化有关。例如，底栖与浮游有孔虫的δ¹⁸O数据趋同，指示多个冰期时期南极中层水（Antarctic Intermediate Waters）上升流增强；而生产力变化可解释记录中部分δ¹³C峰值。 随着分析分辨率的持续提升，该岩芯将为以新西兰为中心的西南太平洋南温带水域提供一套极具价值的第四纪同位素参考剖面。