Foraminifers from DSDP Leg 87 holes@en

Leg 87 investigated two sites in the Nankai Trough, off southeastern Japan, and one in the Japan Trench, off northeastern Japan. Several holes at the Nankai Trough sites penetrated mostly Quaternary interbedded sandy turbidites and hemipelagic mud. Foraminifers are common only in certain turbidite sands because both sites are at or just below the carbonate compensation depth. The planktonic assemblages from these sandy layers consist of mixed cool-temperate and warm-water species, and include both solution-resistant and solution-prone species. The benthic assemblages from these same layers are composed of mixtures of shelf to abyssal species. The northward-flowing Kuroshio is important in producing the mixed planktonic faunas, whereas turbidity currents are the primary agents in mixing benthic faunas and in the rapid burial of both planktonic and benthic foraminifers, which protects them from solution. Interbedded hemipelagic muds are barren or contain sparse faunas. Hole 582B penetrated through the trench-fill deposits into hemipelagic sediments that originated in the Shikoku Basin. These muds contain a dissolution facies of solution-resistant planktonic species, partially dissolved tests, and deep bathyal benthic species. […]第87航次（Leg 87）对日本东南部海域的南海海槽（Nankai Trough）两处站位，以及日本东北部海域的日本海沟（Japan Trench）一处站位开展了钻探调查。南海海槽站位的多个钻孔主要钻遇第四纪互层砂质浊积岩与半远洋沉积物。仅在部分浊积砂层中发育有孔虫（Foraminifers），因两处站位均处于碳酸盐补偿深度（carbonate compensation depth, CCD）或略低于该深度。该类砂质层位中的浮游有孔虫组合由温凉型与暖水型物种混合构成，同时包含抗溶蚀与易溶蚀物种。同一层位的底栖有孔虫组合则由陆架至深渊的各类物种混合组成。向北流动的黑潮（Kuroshio）是形成混合浮游有孔虫群的关键因素，而浊流（turbidity currents）则是混合底栖有孔虫群、快速埋藏浮游与底栖有孔虫的主要营力，该过程可保护有孔虫免受溶蚀作用影响。互层的半远洋泥层中缺乏生物化石，或仅含少量生物群。582B钻孔穿透海槽充填沉积物，进入源自四国盆地（Shikoku Basin）的半远洋沉积层。该套泥质沉积物中发育有抗溶蚀浮游物种的溶蚀相、部分溶解的壳体，以及半深海深水底栖物种。[…]