Diatom data from voyage 1 of the Investigator, 2017 - PC03 analysis

These data were generated by Raffaella Tolotti ([e-mail]) thanks to a scholarship founded by the Italian P.N.R.A. ‘TYTAN Project (PdR 14_00119): ‘Totten Glacier dYnamics and Southern Ocean circulation impact on deposiTional processes since the mid-lAte CeNozoic’ (Principal Investigator Dr. Donda Federica, Dr. Caburlotto A. - OGS, Trieste) and University of Genova (DISTAV - Prof. Corradi Nicola). These data are based on samples collected during research cruise IN2017_V01 of the RV Investigator, co-chief scientists, Leanne Armand and Phil O’Brien and were collected to provide paleoceanographic and bio/ stratigraphic information on Aurora Basin Antarctic margin evolution.The IN2017-V01post-cruise report is available through open access via the e-document portal through the ANU library.https://openresearch-repository.anu.edu.au/handle/1885/142525The document DOI:10.4225/13/5acea64c48693The preferred citation are:L.K. Armand, P.E. O’Brien and On-board Scientific Party. 2018. Interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles (IN2017-V01): Post-survey report, Research School of Earth Sciences, Australian National University: Canberra, http://dx.doi.org/10.4225/13/5acea64c48693Donda F., Leitchenkov, Brancolini G., Romeo R., De Santis L., Escutia C., O'Brien P., Armand L., Caburlotto, A., Cotterle, D., 2020. The influence of Totten Glacier on the Late Cenozoic sedimentary record. Antarctic Science, 1 -3; http://doi:10.1017/S0954102020000188O’Brien, P.E., Post, A.L., Edwards, S., Martin, T., Carburlotto, A., Donda, F., Leitchenkov, G., Romero, R., Duffy, M., Evangelinos, D., Holder, L., Leventer, A., López-Quirós, A., Opdyke, B.N., and Armand, L.K. in press. Continental slope and rise geomorphology seaward of the Totten Glacier, East Antarctica (112°E-122°E). Marine Geology.Samples for diatom analysis were collected on board ship immediately after core recovery. Sub-samples were sent, according to the Australian standard procedures, to the DISTAV sedimentological laboratory in Genoa (Italy) and prepared for the micro-paleontological analysis according to the laboratory’s protocol (imported and tested from Salamanca University lab.; Referring Prof. Bárcena). Smear-slides and the qualitative-quantitative analyses were performed every 20 cm. Previous onboard smear slides analyses on PC03 highlighted notable variations from the other piston cores, containing some older diatom species. Moreover this core exceptionally did not exhibit a clear cyclicity like the others. It was so assumed to target a condensed sedimentary sequence giving access to older sediments. The further, more in-depth diatom biostratigraphic and quantitative analyses were performed in accordance with the international stratigraphic guide (https://stratigraphy.org/guide/), with the pluri-decennial DSDP and IODP Antarctic diatom biostratigraphic reports and specific papers (see References). Sample preparation, diatom species identification and counting were those described in Schrader and Gersonde (1978), Barde (1981 - modified) and Bodén (1991). Diatom analysis was performed with an immersion 1000x LM Reichert Jung-Polyvar microscope (Wien). Whenever possible, almost 300 diatom valves were counted per slide following the counting methodology presented in Schrader and Gersonde (1978). When diatom concentration proved too low or too concentrated, slides with modified concentrations have been prepared to optimize counting and identification while at least one hundred fields-of-view per poor concentration slide have been analyzed. For samples that were too diatom-poor, the over-concentration of material on the slides resulted in limiting resolution and taxonomic identification of the rare and mostly fragmented valves. Where diatom occurrence was rare only major fragments (>50%) or entire valves were counted. The file (.xls) contains 2 sheets:Sheet: PC03 diatoms dataset.The absolute diatom valve concentration (ADA= Absolute Valves Abundance) was then calculated following Abrantes et al. (2005), Warnock and Scherer (2014) and ADA in Taylor, Silva and Riesselmann (2018), taking in account initial weights, concentration of the samples and microscope’s characteristics, as the number of valves per gram of dry sediment. Diatoms were identified to species level following Crosta et al. (2005), Armand et al. (2005), Cefarelli et al. (2010) for modern assemblages. Older diatom taxa were identified following Gersonde et Bárcena, 1998, Witkowski et al., 2014; Bohaty et al., 2011; Gombos, 1985; Gombos, 2007; Gersonde et al., 1990; Barron et al., 2004; Harwood et al., 2001; Harwood etal., 1992. Species were considered extinct when observed stratigraphically higher than extinction boundaries as identified by Cody et al. (2008) but the coexistence or the alternation in the stratigraphic sequence of taxa referring to different biostratigraphic age ranges were considered signs of reworking.Sheet: PC03 tephra dataset.During LM microscopic observations some volcanic glass shards were observed first in smear slides and then counted during the activities of microfossils count for diatoms. This allowed to obtain the number of glass shards/g. dry sed. useful to compare with diatom and sediment datasets.Core location:Station_core Longitude LatitudeA006_PC03 115.043 -64.463Depth:The core was taken at Site A006 that was chosen into an overbank deposit on the upper western side of a turbidite channel (Minang-a Canyon) (Fig. 39 – Armand et al., 2017; O’Brien et al., 2020). The setting is at 1862 m depth, shallower respect the other cores. A possible higher energy environment, with a lower sedimentation rate has been first supposed.Temporal coverage:Start date: 2017-01-14 - Stop date: 2018-11-30References:Armand, L.K., X. Crosta, O. Romero, J. J. Pichon (2005). The biogeography of major diatom taxa in Southern Ocean sediments: 1. Sea ice related species, Paleogeography, Paleoclimatology, Paleoecology, 223, 93-126.Cefarelli, A.O., M. E. Ferrario, G. O. Almandoz, A. G. Atencio, R. Akselman, M. Vernet (2010). Diversity of the diatom genus Fragilariopsis in the Argentine Sea and Antarctic waters: morphology, distribution and abundance, Polar Biology, 33(2), 1463-1484.Cody, R., R. H. Levy, D. M. Harwood, P. M. Sadler (2008). Thinking outside the zone: High-resolution quantitative diatom biochronology for the Antarctic Neogene, Palaeogeography, Palaeoclimatology, Palaeoecology, 260, 92-121; doi:10.1016/j.palaeo.2007.08.020Crosta, X., O. Romero, L. K. Armand, J. Pichon (2005). The biogeography of major diatom taxa in Southern Ocean sediments: 2. Open ocean related species, Palaeogeography, Palaeoclimatology, Palaeoecology, 223, 66-92.Rebesco, M., E. Domack, F. Zgur, C. Lavoie, A. Leventer, S. Brachfeld, V. Willmott, G. Halverson, M. Truffer, T. Scambos, J. Smith, E. Pettit (2014). Boundary condition of grounding lines prior to collapse, Larsen-B Ice Shelf, Antarctica, Science, 345, 1354-1358.Warnock, J. P., R. P. Scherer (2014). A revised method for determining the absolute abundance of diatoms, J. Paleolimnol.; doi:10.1007/s10933-014-9808-0Witkowski, J., Bohaty, S.M., McCartney, K., Harwood, D.M., (2012) . Enhanced siliceous plankton productivity in response to middle Eocene warming at Southern Ocean ODP Sites 748 and 749 Palaeogeog., Palaeoclimat., Palaeoecol., 326–328, 78–94; doi:10.1016/j.palaeo.2012.02.006Witkowski, J., Bohaty, S.M., Edgar, K.M., Harwood, D.M., (2014). Rapid fluctuations in mid-latitude siliceous plankton production during the Middle Eocene Climatic Optimum (ODP Site 1051, Western North Atlantic). Mar. Micropal., 106, 110–129. http://dx.doi.org/10.1016/j.marmicro.2014.01.001Raffaella Tolottiunpublished data

本数据集由Raffaella Tolotti（邮箱：[e-mail]）生成，其研究得到意大利国家研究计划（PNRA, P.N.R.A.）"TYTAN项目"（项目编号PdR 14_00119，全称“中晚新生代以来托滕冰川动力学与南大洋环流对沉积过程的影响（Totten Glacier dYnamics and Southern Ocean circulation impact on deposiTional processes since the mid-lAte CeNozoic）”）的奖学金资助，项目首席研究员为Donda Federica博士、Caburlotto A.博士（意大利的里雅斯特国家海洋地球物理研究所OGS）以及热那亚大学DISTAV学院的Corradi Nicola教授。

本数据集基于“调查者”号（RV Investigator）科考航次IN2017_V01采集的样品生成，该航次联合首席科学家为Leanne Armand与Phil O’Brien，样品采集旨在为奥罗拉盆地南极陆缘演化提供古海洋学与生物/地层学相关信息。IN2017-V01航次后报告可通过澳大利亚国立大学（ANU）图书馆的电子文档门户开放获取：https://openresearch-repository.anu.edu.au/handle/1885/142525，文档DOI：10.4225/13/5acea64c48693。

推荐引用格式如下：
1. L.K. Armand、P.E. O’Brien 与船上科研团队. 2018. 《多个冰期旋回中托滕冰川与南大洋的相互作用（IN2017-V01）：航后报告》，澳大利亚国立大学地球科学研究学院：堪培拉，http://dx.doi.org/10.4225/13/5acea64c48693
2. Donda F., Leitchenkov, Brancolini G., Romeo R., De Santis L., Escutia C., O'Brien P., Armand L., Caburlotto, A., Cotterle, D.. 2020. 《托滕冰川对晚新生代沉积记录的影响》，南极科学（Antarctic Science），1-3；http://doi:10.1017/S0954102020000188
3. O’Brien, P.E., Post, A.L., Edwards, S., Martin, T., Carburlotto, A., Donda, F., Leitchenkov, G., Romero, R., Duffy, M., Evangelinos, D., Holder, L., Leventer, A., López-Quirós, A., Opdyke, B.N., and Armand, L.K. 已刊印. 《南极东部托滕冰川外侧（112°E-122°E）的大陆坡与陆隆地貌》，海洋地质（Marine Geology）.

硅藻分析样品在岩芯回收后立即于船上采集，按照澳大利亚标准流程分装后，送往意大利热那亚的DISTAV沉积学实验室，并依据实验室规程（源自萨拉曼卡大学实验室并经测试，对应负责教授为Bárcena）完成微古生物学分析的样品制备。每20cm制作一张硅藻涂片，并开展定性-定量分析。此前针对PC03岩芯的船上涂片分析显示，该岩芯与其他活塞岩芯存在显著差异，其含有部分古老硅藻物种，且未像其他岩芯那样表现出清晰的沉积旋回性，因此推测该岩芯对应一套浓缩沉积序列，可获取更古老的沉积物。后续更深入的硅藻生物地层学与定量分析工作，依据国际地层指南（https://stratigraphy.org/guide/）、数十年的深海钻探计划（Deep Sea Drilling Project, DSDP）与综合大洋钻探计划（Integrated Ocean Drilling Program, IODP）南极硅藻生物地层报告及相关专业文献开展（参见文末参考文献）。样品制备、硅藻物种鉴定与计数方法参照Schrader与Gersonde（1978）、Barde（1981，修订版）及Bodén（1991）的标准流程。硅藻分析采用1000倍浸液式光学显微镜（Light Microscope, LM）Reichert Jung-Polyvar（产自维也纳）。按照Schrader和Gersonde（1978）提出的计数方法，每张涂片尽可能计数近300个硅藻壳瓣。当硅藻浓度过高或过低时，制备浓度调整后的涂片以优化计数与鉴定效果；对于浓度过低的涂片，至少分析100个视野。对于硅藻含量极低的样品，载片上沉积物过浓会限制对稀有且大多破碎的壳瓣的分辨率与分类鉴定，此时仅计数占比>50%的主要碎片或完整壳瓣。

本数据集保存为.xls格式文件，包含两个工作表：
1. PC03 diatoms dataset（PC03硅藻数据集）：
绝对硅藻壳瓣浓度（Absolute Valves Abundance, ADA）依据Abrantes等（2005）、Warnock与Scherer（2014）及Taylor、Silva与Riesselmann（2018）提出的方法计算，结合样品初始重量、样品悬浮液浓度与显微镜参数，最终得到每克干沉积物中的硅藻壳瓣数。硅藻物种鉴定参照Crosta等（2005）、Armand等（2005）、Cefarelli等（2010）针对现代硅藻组合的分类标准；古老硅藻类群的鉴定则参照Gersonde与Bárcena（1998）、Witkowski等（2014）、Bohaty等（2011）、Gombos（1985、2007）、Gersonde等（1990）、Barron等（2004）、Harwood等（2001、1992）的研究成果。当某一硅藻物种在其灭绝界线之上的地层中被发现时，即视为已灭绝物种；但若地层序列中同时存在或交替出现属于不同生物地层年代范围的类群，则判定为再沉积成因。
2. PC03 tephra dataset（PC03火山碎屑数据集）：
在光学显微镜观察过程中，研究人员首先在硅藻涂片中发现了火山玻璃碎屑，并在后续硅藻微化石计数过程中对其进行计数，由此得到每克干沉积物中的玻璃碎屑数，以便与硅藻及沉积物数据集开展对比分析。

### 岩芯基本信息
#### 站位坐标
| 站位岩芯 | 经度 | 纬度 |
| ---- | ---- | ---- |
| A006_PC03 | 115.043 | -64.463 |
#### 站位水深
该岩芯采自A006站位，该站位选在浊积水道（Minang-a峡谷）西侧上部的岸堤沉积中（参见图39——Armand等，2017；O’Brien等，2020），站位水深1862米，较其他岩芯更浅。最初推测该区域处于能量较高、沉积速率较低的沉积环境。
#### 时间覆盖范围
起始日期：2017-01-14，终止日期：2018-11-30

### 参考文献
1. Armand, L.K., X. Crosta, O. Romero, J. J. Pichon (2005). 南大洋沉积物中主要硅藻类群的生物地理学：1. 与海冰相关的物种，《古地理学、古气候学、古生态学》，223, 93-126.
2. Cefarelli, A.O., M. E. Ferrario, G. O. Almandoz, A. G. Atencio, R. Akselman, M. Vernet (2010). 阿根廷海与南极水域中脆杆藻属（Fragilariopsis）的多样性：形态、分布与丰度，《极地生物学》，33(2), 1463-1484.
3. Cody, R., R. H. Levy, D. M. Harwood, P. M. Sadler (2008). 突破传统带域思维：南极新近纪高分辨率定量硅藻生物年代学，《古地理学、古气候学、古生态学》，260, 92-121; doi:10.1016/j.palaeo.2007.08.020
4. Crosta, X., O. Romero, L. K. Armand, J. Pichon (2005). 南大洋沉积物中主要硅藻类群的生物地理学：2. 与开阔大洋相关的物种，《古地理学、古气候学、古生态学》，223, 66-92.
5. Rebesco, M., E. Domack, F. Zgur, C. Lavoie, A. Leventer, S. Brachfeld, V. Willmott, G. Halverson, M. Truffer, T. Scambos, J. Smith, E. Pettit (2014). 南极拉森-B冰架坍塌前的接地线边界条件，《科学》，345, 1354-1358.
6. Warnock, J. P., R. P. Scherer (2014). 一种测定硅藻绝对丰度的修订方法，《古湖沼学杂志》; doi:10.1007/s10933-014-9808-0
7. Witkowski, J., Bohaty, S.M., McCartney, K., Harwood, D.M., (2012) . 南大洋ODP站位748与749中始新世中期变暖导致的硅质浮游生物生产力提升，《古地理学、古气候学、古生态学》，326–328, 78–94; doi:10.1016/j.palaeo.2012.02.006
8. Witkowski, J., Bohaty, S.M., Edgar, K.M., Harwood, D.M., (2014). 始新世中期气候最佳期北大西洋西部ODP站位1051的中纬度硅质浮游生物生产快速波动，《海洋微体古生物学》，106, 110–129. http://dx.doi.org/10.1016/j.marmicro.2014.01.001

Raffaella Tolotti 未发表数据