南沙群岛永暑礁小潟湖岩心有孔虫动物群及其沉积环境   总被引：1，自引：0，他引：1  

温孝胜  涂霞  秦国权  郑范  赵焕庭 《热带海洋学报》2001,(4)

根据永暑礁小潟湖"南永3"井高分辨率的岩心材料,结合其高精度TIMS U系测年,系统研究了1 682 a B.P.以来环礁潟湖沉积柱样的有孔虫分类?类型与属种的组成,揭示了其垂直变化?有孔虫共48属62种,都是全新世-现代种,其中底栖有孔虫55种?其组成表征了印度洋-太平洋有孔虫区系和热带珊瑚礁相环境?即使由温凉水种浮游有孔虫偏多的时段所反映的表层水温也相对偏低,推测其变化幅度很小?底栖有孔虫茸刺距轮虫δ18O含量的变化曲线呈4峰4谷交替,反映了永暑礁海区近1 682 a以来的气候有4个凉期和4个暖期,同2 000a以来的全球气候变化周期一致?有孔虫种类的垂向变化也反映了海平面有些小变动?  相似文献   

底栖有孔虫对厦门筼筜湖污染的监测作用     

方惠瑛  王健  郑瑞芝  张钒 《台湾海峡》1997,(1)

1992年11月至1993年8月对厦门湖及厦门西港部分海域底栖有孔虫及相关的环境化学要素进行了4个季度月的调查，发现湖的底栖有孔虫可分为三个群落，即正常群落、半污染群落和污染群落，分别代表了湖内不同污染程度环境，同时发现了底栖有孔虫的耐得种类和对污染敏感种类，它们具有指示环境的意义。  相似文献   

台湾海峡中、北部浮游有孔虫同海流和沉积环境的关系   总被引：1，自引：0，他引：1  

方惠瑛 《海洋与湖沼》1995,26(5):542-551

于１９８７年７月和８月及１９８８年５月和７月，在台湾海峡中、北部海域，利用浮游生物网和蚌式采泥器分别采集了水层中的浮游有孔虫标本和表层沉积里的浮游有孔虫遗壳样品。对活体和遗壳在数量和组成方面对比分析研究表明，调查海区暖水性最强的水域位于东南角的Ａ５站一带，海峡暖流水由此向北延伸，在海坛岛以东Ｄ１站附近，因与闽浙沿岸水交汇而减弱。遗壳高值区位于深水的盆地，活体则出现在台地上，两者分布不一致。其原因在  相似文献   

南海南部活体浮游有孔虫分布特征及其影响因素初探   总被引：1，自引：0，他引：1  

崔喜江  向荣  郑范  陈木宏 《热带海洋学报》2006,25(4):25-30

通过对2002年5月采自南海南部海区11个站位20个垂直分层浮游拖网样品的浮游有孔虫组成和分布特征的初步分析,发现该区表层水体中浮游有孔虫分布广泛,共鉴定属种20种,以热带暖水种占绝对优势,广适应性冷水种有零星出现。深水种Globorotalia menardii在南海南部50 m水层中广泛出现,但壳体相对较小,壳壁较薄。该区0—50m水层活体浮游有孔虫丰度范围为(6 138—64 174)枚.1 000 m-3海水,大致呈西高东低的分布趋势,在西南部浅水区和西北部上升流区丰度最高,与表层水体的营养水平密切相关。将水样浮游有孔虫分布数据与该海区23个站位表层沉积样数据进行对比分析,发现遗壳浮游有孔虫与活体的分布关系密切,虽然在种属丰度以及分布范围等方面有明显差异,但两者具有相似的优势种组合。主要差异在于水体中浮游有孔虫优势种相对丰度差异较大,易溶种Hastigerina pelagica含量较高,而遗壳中浮游有孔虫各种属分布趋向于均匀化。此外,陆源物质的释稀作用对沉积物中的有孔虫丰度分布有明显的控制作用。  相似文献   

Lithium Isotope Composition of Marine Biogenic Carbonates and Related Reference Materials          下载免费PDF全文

Luc Bastian  Nathalie Vigier  Stéphanie Reynaud  Marie‐Emmanuelle Kerros  Marie Revel  Germain Bayon 《Geostandards and Geoanalytical Research》2018,42(3):403-415

In this study, the accuracy and the precision corresponding to Li isotopic measurements of low level samples such as marine and coastal carbonates are estimated. To this end, a total of fifty‐four analyses of a Li‐pure reference material (Li7‐N) at concentrations ranging from 1 to 6 ng ml^?1 were first performed. The average δ⁷Li values obtained for solutions with and without chemical purification were 30.3 ± 0.4‰ (2s, n = 19) and 30.2 ± 0.4‰ (2s, n = 36), respectively. These results show that the chosen Li chemical extraction and purification procedure did not induce any significant isotope bias. Two available carbonate reference materials (JCt‐1 and JCp‐1) were analysed, yielding mean δ⁷Li values of 18.0 ± 0.27‰ (2s, n = 6) and 18.8 ± 1.8‰ (2s, n = 9), respectively. Small powder aliquots (< 15 mg) of JCp‐1 displayed significant isotope heterogeneity and we therefore advise favouring JCt‐1 for interlaboratory comparisons. The second part of this study concerns the determination of δ⁷Li value for biogenic carbonate samples. We performed a total of twenty‐nine analyses of seven different tropical coral species grown under controlled and similar conditions (24.0 ± 0.1 °C). Our sample treatment prior to Li extraction involved removal of organic matter before complete dissolution in diluted HCl. Our results show (a) a constant δ⁷Li within each skeleton and between the different species (δ⁷Li = 17.3 ± 0.7‰), and (b) a Li isotope fractionation of ?2‰ compared with inorganic aragonite grown under similar conditions. Comparison with literature data suggests a significant difference between samples living in aquaria and those grown in natural conditions. Finally, we investigate ancient (fossil) carbonate material and foraminifera extracted from marine sedimentary records. Different leaching procedures were tested using various HCl molarities. Results indicate that carbonate preferential dissolution must be carried out at an acid molarity < 0.18 mol l^?1. Possible contamination from silicate minerals can be verified using the Al/Ca ratio, but the threshold value strongly depends on the carbonate δ⁷Li value. When the silicate/carbonate ratio is high in the sediment sample (typically > 2), contamination from silicates cannot be avoided, even at low HCl molarity (? 0.1 mol l^?1). Finally, bulk carbonate and foraminifera extracted from the same core sample exhibited significant discrepancies: δ⁷Li values of foraminifera were more reproducible but were significantly lower. They were also associated with lower Sr/Ca and higher Mn/Ca ratios, suggesting a higher sensitivity to diagenesis, although specific vital effects cannot be fully ruled out.  相似文献   

冲绳海槽MIS6期以来底栖有孔虫碳氧同位素特征及其古海洋指示意义     

窦衍光  李清  吴永华  赵京涛  孙呈慧  蔡峰  陈晓辉  张勇  范佳慧  石学法 《地学前缘》2022,29(4):84-92

基于AMS ¹⁴C年龄和底栖有孔虫氧同位素建立的地层年代框架,重点探讨了冲绳海槽中北部CSHC-15孔MIS6期以来(约200 ka)底栖有孔虫δ¹³C特征及其古海洋指示意义。结果显示,冰期-间冰期表层初级生产力和有机质通量的变化是导致底栖有孔虫δ¹³C值在MIS4和MIS6期负偏而在MIS1、MIS3和MIS5期正偏的主要原因。MIS2期的底栖有孔虫δ¹³C正偏,指示了NPIW侵入冲绳海槽,导致通风性加强,底层水呈弱氧化状态。甲烷渗漏引发的甲烷厌氧氧化作用(AOM)是导致CSHC-15孔底栖有孔虫在MIS4期碳同位素大幅负偏的原因。  相似文献   

Phase relationship and surface water mass change in the Northeast Atlantic during Marine Isotope Stage 11 (MIS 11)     

Evgeniya S. Kandiano  Henning A. Bauch 《Quaternary Research》2007,68(3):445-455

Planktic foraminiferal census data, faunal sea surface temperatures (SSTs) and oxygen isotopic and lithic records from a site in the northeast Atlantic were analyzed to study the interglacial dynamics of Marine Isotope Stage (MIS) 11, a period thought to closely resemble the Holocene on the basis of orbital forcing. Interglacial conditions during MIS 11 persisted for approximately 26 ka. After the main deglacial meltwater processes ceased, a 10- to 12-ka-long transitional period marked by significant water mass circulation changes occurred before surface waters finally reached their thermal maximum. This SST peak occurred between 400 and 397 ka, inferred from the abundance of the most thermophilic foraminiferal species and was coincident with lowest sea level according to benthic isotope values. The ensuing stepwise SST decrease characterizes the overall climate deterioration preceding the increase in global ice volume by  3 ka. This cooling trend was followed by a more pronounced cold event that began at 388 ka, and that terminated in the recurrence of icebergs at the site around 382 ka. Because the water mass configuration of early MIS 11 evolved quite differently from that of the early Holocene, there is little evidence that MIS 11 can serve as an appropriate analogue for a future Holocene climate, despite the similarity in some orbital parameters.  相似文献   

Early Miocene carbonate ramp development in a warm ocean,North West Shelf,Australia     

Rosine Riera  Julien Bourget  Tony Allan  Eckart Hkansson  Moyra E. J. Wilson 《Sedimentology》2022,69(1):219-253

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On the Validity and Evolution of Assilina Species during the Ypresian–Lutetian: Example from Bir Dakhl, Eastern Desert, Egypt     

Safia AL MENOUFY  Mohamed BOUKHARY 《《地质学报》英文版》2021,95(4):1080-1085

The genus Assilina is a taxon within the Nummulitacea that appeared early in the Ypresian (Early Eocene) and continued until the end of the Lutetian (Middle Eocene). Thus, this taxon could be useful for the chronostratigraphy of this time interval. Lower Eocene rocks in southern Galala, Egypt are exposed at Bir Dakhl. This section includes marl sediments with debris flow shallow-marine facies deposits laid down during early Eocene times and includes fossils of large foraminifera: Assilina placentula Deshayes, 1838 and Nummulites burdigalensis de la Harpe, 1926. These are systematically treated, described and illustrated. Nummulites burdigalensis belongs to the N. burdigalensis group, and Assilina placentula belongs to the group of Assilina exponens. This assumption is based on qualitative morphology and quantitative measurements. Both species, together with Operculina libyca Schwager, 1883, enable the assignment of the Bir Dakhl (D5-40 Section) to the Early Eocene, Ypresian (SBZ10 of Serra- Kiel et al., 1998) supporting an earlier opinion that Assilina placentula belongs to that zone in the calibrated larger foraminiferal biostratigraphic zonation.  相似文献   

Microfacies Analysis and Paleoecology of the Oligocene Succession in a Central Tethyan Carbonate Platform,Zagros Basin,SW Iran     

Tahereh HABIBI 《《地质学报》英文版》2021,95(5):1634-1646

Two stratigraphic sections (Arjooieh and Firoozabad) of the Mymand anticline, located in the Interior Fars sub-basin of the Zagros Mountains, were measured and sampled, in order to document sedimentological characteristics, microfacies types and paleo-seagrasses indicators of the Oligocene succession (Asmari Fm.). Planktonic and benthic foraminifera and coralline red algae are the principal fossils from these strata. Foraminifera are represented by the following families: Soritidae, Peneroplidae, Austrotrillinidae, Alveolinidae, Planorbulinidae, Discorbidae, Lepidocyclinidae, Amphisteginidae, Rotaliidae, Nummulitidae and Globigerinidae. Nine microfacies types were recognized, namely planktonic foraminifera-peloidal packstone (MF1), bioclast nummulitid/Nerorotalia/Amphistegina?packstone-grainstone-rudstone-floatstone (MF2),?Neorotalia-echinoid coralline red algae packstone-grainstone (MF3), coral boundstone (MF4), coral/coralline red algae rudstone-floatstone-packstone-grainstone (MF5), diverse imperforate foraminifera bioclast packstone-grainstone (MF6), peloid wackestone-packstone-grainstone (MF7), fenestrated mudstone and microbial mats (MF8) and anhydrite (MF9). MF1 indicates an outer ramp, MFs 2-4 represent a mid-ramp and MFs 5–9 are interpreted as inner ramp environment. Paleo-seagrass indicators consisting of foraminifera, hooked and tabular forms of coralline red algae and corals. They were identified in MFs 5 and 6, reflecting the presence of vegetated environments within the mid/inner ramp setting.?The Mymand anticline was dominated by the outer ramp environment at the start of the Rupelian. Mid to inner ramp environments prevailed during the Rupelian. The Chattian corresponds to the spread of the inner ramp setting over the Mymand anticline.  相似文献