Oceanographic and climatic evolution of Kerguelen Plateau region: Collaborative research aboard the Japanese research vessel Mirai

Metadata record for data from ASAC Project 2393See the link below for public details on this project.---- Public Summary from Project ----This project seeks to monitor Holocene-Quaternary variability of Antarctic bottom water outflow at a known deep pathway (east flank of Kerguelen Plateau) into a major ocean basin. Specifically, we can address the question of how sea-ice, frontal dynamics and SST variability are related to bottom-water production.Taken from the 2003-2004 Progress ReportTwo researchers from the ACE CRC and IASOS, Dr. Will Howard and Honours student Joanne Naylor, participated in a cruise to the Southern Kerguelen Plateau region in January-February 2004. The objectives were to carry out swath bathymetric mapping, subbottom profiling (using a 3.5 kHz echosounder), and coring, aboard the Japanese research vessel Mirai. We were successful in carrying out acoustic profiling and mapping in previously unmapped regions of the Southeast Indian Ridge and in the Labuan Basin area of Southern Kerguelen Plateau. Acoustic data have already been provided to Geoscience Australia, where these data will be incorporated into existing databases of bathymetry and bottom character of this (potential) part of the Australian Marine Jurisdiction.In addition we recovered two piston cores, one each from the SE Indian Ridge area and Kerguelen Plateau, as well as multicores (recovery of sediment-water interface). Inclement weather prevented us from recovering cores from all the suitable coring sites we identified, but we now have acoustic survey data in unprecedented detail and resolution to support future sampling efforts. The cores we recovered consist of pelagic sediments as follows:Split surfaces of archive half sections were exposed and lithological and sedimentological features were described using printed visual core description (VCD) sheets On MR03-K04 Leg 6, ODP-style nomenclature for lithological description (e.g., Mazzullo et al., 1988) was adopted. Results from smear slides, coarse-fraction microfossil observations were combined to construct summarised lithologic columns. This information was also confirmed by the later inspection of soft X-radiographs. Smear-slide descriptions and sieve sample also provide preliminary biostratigraphic estimates of base ages for the piston cores.ResultsIn general, the sediments at both sites are composed of homogenous fine-grainedpelagic sediments with extensive, though varying, bioturbation throughout.The lithological and sedimentological features are summarised as graphic columns with short notes, including a legend of symbols and lithologic patterns (Figures D-2-1, D-2-2, D-2-3).Digitised versions of individual VCD sheets and scanned soft X-radiographs used for constructing graphic columns are archived in the Appendix to this report.Southeast Indian Ridge (41 degrees 33.07'S, 90 degrees24,39 E, water depth: 2,913 m)The sediments from MC-05 and PC-05 from the northern flank of Southeast Indian Ridge are dominated by foraminifer-bearing nannofossil ooze. Foraminifera and nannofossils are abundant and well-preserved throughout the core. A qualitative analysis of the planktonic foraminiferal faunas from sieve samples taken at the base of the piston core and the top of the multicore show a diverse assemblage typical of coretops in the Southern Indian Ocean near the modern position of the Subtropical Front Zone, with abundant Globorotalia inflata, Globigerina bulloides, Globigerinita glutinata, and dextral Neogloboquadrina pachyderma (e.g. Howard and Prell, 1992 and 1994).The diatom Hemidiscus karsteni appears to be present in the core base whereas the radiolarian Stylatractus universus appears to be absent. These suggest a base age for PC-05 older that late Marine Isotope Stage (MIS) 7 (approx. 194 ka BP) and younger than late MIS 12 (approx 423 ka BP)*.Flow-in is severe in Sections IX and X and the core catcher of PC-05 (i.e. approx. the bottom 1.5 meters of the core). Comparison with the multicore indicates that the top of the piston core is also moderately disturbed by the piston action.Kerguelen Plateau (53 degrees 48.15'S, 81 degrees 52.75'E, water depth: 2,557 m)The sediments from MC-06 and PC-06 from Labuan Basin, Kerguelen Plateau are dominated by radiolarian-bearing diatom ooze with dispersed foraminifera, detrital grains, and rare nannofossils. Dispersed sand-to-gravel sized rock fragments are present in the core, indicating intermittent ice-rafted debris deposition. The soft X-radiographs similarly show the alternation of almost pure biogenic ooze with more clay-rich oozes with dispersed detrital grains. Though the core is bioturbated to some extent throughout its length, 1-2 cmscale laminations occur in Sections 3-8.Foraminifera present through core in varying states of preservation; nannofossils intermittently present. The planktonic foraminiferal assemblages are typical of coretops in the Subantarctic and Polar Front Zones, dominated by sinistral Neogloboquadrina pachyderma, Globigerina quinqueloba , and G. bulloides, with lesser contributions from globorotalids like Globorotalia crassiformis and and G. inflata.H. karsteni appears to be present from Section 6 (500 cm bsf) down, and abundant in Section 8, from 86 cm down (from approx. 786 cm bsf). The planktonic foraminifer G. crassiformis is present in the base. S. universus appears to be absent throughout the core. This preliminary estimate of the biostratigraphy suggests a base age for PC-06 older that late MIS 9 and younger than MIS 12 (i.e. between approx. 423 and 300 ka BP).The top 176 cm of this core are severely disturbed, being 'washed' during core recovery by water trapped in the core barrel by the stuck piston.All cores were also logged for geophysical properties and optical reflectance (an index of sediment properties).Also see the JAMSTEC (Japan Agency for Marine-Earth Science and Technology) site for more information.

ASAC项目2393数据集元数据记录
请点击下方链接查看该项目的公开详情。
—— 项目公开摘要 ——
本项目旨在监测已知深海通道（凯尔盖朗高原东翼）处，南极底层水向大型大洋盆地运移过程中全新世-第四纪的变化特征。具体而言，本项目旨在解答海冰、锋面动力学与海表温度（SST, Sea Surface Temperature）变化如何与底层水形成相关联的问题。

本节内容摘自2003-2004年度项目进展报告：
2004年1-2月，来自ACE CRC与IASOS的两名研究人员——威尔·霍华德博士与荣誉学生乔安妮·内勒，搭乘日本科研船“未来号”（Mirai）前往凯尔盖朗高原南部海域开展科考航次。本次航次的任务目标为开展条带测深制图、亚底剖面探测（使用3.5kHz回声测深仪）以及岩芯钻探作业。
我们成功完成了东南印度洋海岭此前未被测绘区域，以及凯尔盖朗高原南部拉布安盆地区域的声学剖面探测与制图工作。声学数据已提交至澳大利亚地质科学局（Geoscience Australia），这些数据将被整合入澳大利亚海域管辖范围内该（潜在）区域的现有水深与海底特征数据库中。

此外，我们成功获取了两根活塞岩芯，分别采自东南印度洋海岭区域与凯尔盖朗高原，同时还获取了多管岩芯（用于采集沉积物-水界面样品）。恶劣天气导致我们未能从所有选定的适宜钻探位点获取岩芯，但目前我们已获得分辨率与细节程度前所未有的声学勘测数据，可为未来的采样工作提供支撑。

我们获取的岩芯均为远洋沉积物，具体信息如下：
将归档岩芯半片的劈面暴露后，使用打印的可视化岩芯描述（VCD, Visual Core Description）记录表对其岩性与沉积学特征进行描述。在MR03-K04航次第6航段，我们采用了大洋钻探计划（ODP, Ocean Drilling Program）式的岩性描述命名规范（例如Mazzullo等人1988年的研究）。结合涂片镜检结果与粗粒组分微古生物观测结果，我们构建了汇总性的岩性柱状图。后续通过软X射线影像扫描结果验证了上述信息。涂片镜检描述与筛析样品分析结果，还为两根活塞岩芯提供了基底年代的初步生物地层学估算结果。

### 研究结果
总体而言，两处采样点的沉积物均为均匀细粒远洋沉积物，整体发育程度不一但分布广泛的生物扰动构造。岩性与沉积学特征以带简短注释的图形柱状图形式汇总，包含符号与岩性样式图例（见图D-2-1、D-2-2、D-2-3）。用于构建图形柱状图的单张可视化岩芯描述记录表数字化版本，以及扫描得到的软X射线影像，均归档于本报告附录中。

#### 东南印度洋海岭采样点（南纬41°33.07′，东经90°24.39′，水深2913米）
采自东南印度洋海岭北坡的MC-05与PC-05岩芯，其沉积物以含有孔虫的颗石藻软泥为主。岩芯中各层位的有孔虫与颗石藻均十分丰富且保存完好。对活塞岩芯底部与多管岩芯顶部的筛析样品中的浮游有孔虫动物群进行定性分析后发现，其组合类型丰富多样，与南印度洋亚热带锋带现代位置附近的岩芯顶部典型组合一致，优势类群包括膨泡拟抱球虫（Globorotalia inflata）、球室异足虫（Globigerina bulloides）、胶粘抱球虫（Globigerinita glutinata）以及右旋粗厚新抱球虫（Neogloboquadrina pachyderma 右旋型）（参考Howard与Prell，1992、1994年研究）。
硅藻Hemidiscus karsteni似乎存在于岩芯底部，而放射虫Stylatractus universus则未在岩芯中检出。据此推断，PC-05岩芯的基底年代晚于海洋同位素阶段（MIS, Marine Isotope Stage）7晚期（约19.4万年前），早于MIS 12晚期（约42.3万年前）*。
PC-05岩芯的第IX、X段以及岩芯捕获器处发生了严重的流体侵入现象，对应岩芯底部约1.5米的层位。与多管岩芯的对比结果显示，该活塞岩芯的顶部也因活塞作用受到了中等程度的扰动。

#### 凯尔盖朗高原采样点（南纬53°48.15′，东经81°52.75′，水深2557米）
采自凯尔盖朗高原拉布安盆地的MC-06与PC-06岩芯，其沉积物以含放射虫的硅藻软泥为主，伴生分散分布的有孔虫、碎屑颗粒以及少量颗石藻。岩芯中可见分散分布的砂-砾级岩屑，指示存在间歇性的冰筏碎屑沉积过程。软X射线影像同样显示，岩芯中几乎纯净的生物源软泥与含分散碎屑颗粒的富黏土软泥交替出现。尽管岩芯整体均受到一定程度的生物扰动，但第3-8段发育有1-2厘米尺度的层理构造。
岩芯各层位均有有孔虫分布，保存状态不一；颗石藻则呈间歇性分布。浮游有孔虫组合类型与亚南极锋带及极锋带附近的岩芯顶部典型组合一致，优势类群为左旋粗厚新抱球虫（Neogloboquadrina pachyderma 左旋型）、五叶抱球虫（Globigerina quinqueloba）以及球室异足虫（G. bulloides），另有少量厚壁抱球虫类群如Globorotalia crassiformis与G. inflata。
Hemidiscus karsteni（简称H. karsteni）似乎自第6段（500厘米bsf，bsf即below sea floor，海底以下深度）起出现，并在第8段（86厘米以下，对应约786厘米bsf处）大量富集。浮游有孔虫Globorotalia crassiformis存在于岩芯底部，Stylatractus universus（简称S. universus）则在整个岩芯中均未检出。本次生物地层学初步估算结果显示，PC-06岩芯的基底年代晚于MIS 9晚期，早于MIS 12（即约30万至42.3万年前）。
该岩芯顶部176厘米层位受到严重扰动，系因活塞卡滞导致岩芯管内积水，在岩芯回收过程中发生冲洗作用所致。

所有岩芯均进行了地球物理特性与光学反射率（沉积物特性的表征指标）的测井分析。
如需了解更多信息，可访问日本海洋地球科学技术厅（JAMSTEC, Japan Agency for Marine-Earth Science and Technology）官方网站。