Benthonic foraminifera of ODP Site 116-717

We report on benthic foraminifer results from Site 717 in the Distal Bengal Fan. Only 80 out of 380 samples contained useful benthic foraminifer information. However, we were able to identify four assemblages: 1. A present-day one dominated by Nuttallides umbonifera with some North Atlantic species; 2. An agglutinated fauna consisting of one species; 3. A reworked assemblage consisting of shallow-water forms; and 4. A reworked fauna consisting of an abundance of all kinds of forms including Cretaceous species. The reworked assemblage 4, we believe, represents a period when fan sediments were blocked from this area by east-west trending intraplate deformation. In the remainder of the core section, sedimentation appears to be dominated by Fan deposition with abundant terrestrial debris. In the infrequent pelagic intervals, it appears that abyssal water masses changed little since the late Miocene.

本研究报道了孟加拉远端扇（Distal Bengal Fan）717站位的底栖有孔虫（benthic foraminifer）分析结果。380个沉积物样品中仅80个可提取到有效底栖有孔虫信息。本次研究共识别出4类有孔虫组合：1. 现代组合，以脐盖虫（Nuttallides umbonifera）为优势类群，伴生部分北大西洋属种；2. 单种胶结质有孔虫组合（agglutinated fauna）；3. 由浅水型属种构成的再沉积组合（reworked assemblage）；4. 包含各类丰富属种（含白垩纪（Cretaceous）物种）的再沉积组合。我们认为，第4类再沉积组合对应了该区域因东西走向板内变形（intraplate deformation）而阻隔扇体沉积物输入的地质时期。岩芯其余层段的沉积作用以扇体沉积为主，伴生大量陆源碎屑物质。在零星发育的远洋沉积层（pelagic intervals）中，自晚中新世（late Miocene）以来，深渊水团（abyssal water masses）未发生显著变化。