Planktonic and benthic foraminiferal abundances in ODP Holes 133-819A and 133-821A

To reveal changes in the oceanic environment on the continental slope adjacent to the Great Barrier Reef, east of Cairns (NE Australia), planktonic and benthic foraminiferal abundances were counted and planktonic percentages (P/B ratios) were determined in sediments from two sites. Counts of planktonic and benthic specimens per gram of sediment over the last glacial/interglacial cycle at the shallowest Site 821, located in a water depth of 212 m just below the core of Subtropical Lower Water, show high abundances in the last glacial compared with the Holocene interglacial. We interpret the apparent increase in abundances during the last glacial as mainly a consequence of fluctuations in the intensity of flow of Subtropical Lower Water along the outer shelf edge and upper slope. During the lowstand in sea level, the increased flow winnowed the sediments, concentrating the foraminiferal skeletons. The P/B ratios are low throughout, with the highest values occurring during the Holocene interglacial and glacial stage 2. This suggests that some upwelling might have occurred during glacial stage 2. […]为揭示澳大利亚东北部凯恩斯以东、毗邻大堡礁（Great Barrier Reef）的大陆坡海域海洋环境变化，本研究对两个站位沉积物中的浮游有孔虫（planktonic foraminifera）与底栖有孔虫（benthic foraminifera）丰度进行了计数，并测定了浮游/底栖比值（P/B ratios）。针对位于亚热带下层水（Subtropical Lower Water）核心下方、水深212米的最浅站位821，其末次冰期-间冰期旋回内每克沉积物中浮游与底栖标本的计数结果显示，末次冰期的有孔虫丰度显著高于全新世间冰期。我们将末次冰期丰度的明显升高主要归因于沿陆架外缘与上陆坡流动的亚热带下层水强度波动。在海平面低水位期，增强的水流对沉积物进行淘洗，使得有孔虫壳体得以富集。整体而言P/B比值始终偏低，最高值出现于全新世间冰期与冰期2期（glacial stage 2），这表明冰期2期可能存在一定程度的上升流活动。[…]