Oxygen-isotope records, age-model results and sedimentation rates of core MD88-779

Core MD88-779 was taken during the 1988 French ASPARA IV cruise in the South East Indian Ocean aboard the Marion DuFresne. The core was situated on the South Tasman Rise (47º50.690S, 146º32.750E) at a depth of 2260m. Although the core recovered was 6.7m long, only the top 2.6m were studied as preliminary investigations had indicated that this section covered the last two glacial cycles.

Isotopic analysis was performed on tests of the benthic foraminifera Cibicidoides wuellerstorfi. The record contains two climatic cycles that reach into isotope-stage 7. The benthic isotope curve of core MD88-779, however, shows a melding of isotopic stages 3-5, which are difficult to separate with depth.

The age-model is derived through comparison with the benthic SPECMAP stack of Martinson et al. (1987). The core covers 200kyr over 260cm, and thus has a low sedimentation rate. It also shows a reduction of sedimentation from the Holocene rates to that of the last glacial (oxygen-isotope stage 2).

The complete loss of a diatom record at 170cm and 210/220cm in the core is extremely unusual. The diatom signal is interpreted as having been removed by increased water mass velocity, extreme post-depositional silica dissolution or decreased productivity. There is no sedimentological evidence from the core which provides further interpretation.

岩芯MD88-779采集于1988年法国"ASPARA IV"航次，搭载科考船为"Marion DuFresne"号，作业海域为东南印度洋。该岩芯采自塔斯曼海隆（South Tasman Rise），站位坐标为南纬47°50.690′、东经146°32.750′，采样水深2260米。尽管回收的岩芯总长6.7米，但仅对其顶部2.6米开展了研究，因前期预调查显示该段岩芯覆盖了最近两次冰期旋回。
研究团队对底栖有孔虫（benthic foraminifera）Cibicidoides wuellerstorfi的壳体开展了同位素分析。该同位素记录包含两个延伸至氧同位素7期（isotope-stage 7）的气候旋回。但岩芯MD88-779的底栖同位素曲线显示，氧同位素3期至5期发生了叠覆，难以通过深度对其进行区分。
该岩芯的年代模型通过与马丁森等人（Martinson et al.，1987）构建的底栖有孔虫SPECMAP堆叠曲线（SPECMAP stack）对比推导得到。该岩芯在260厘米的沉积层段中记录了20万年的沉积历史，因此沉积速率较低。同时，其沉积速率从全新世（Holocene）水平下降至末次冰期（氧同位素2期）水平。
该岩芯在170厘米、210/220厘米深度处完全缺失硅藻记录，这一现象极为罕见。研究认为，硅藻信号的缺失可能由水团流速增强、沉积后极端硅质溶解作用或生产力下降所致。该岩芯未提供可用于进一步解释该现象的沉积学证据。