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1.
为了多角度理解海洋纹层沉积物的形成过程,利用在西菲律宾海采集到的含纹层硅藻席的XT47孔岩心样品,进行多囊虫类放射虫的组合变化与环境意义分析.研究表明XT47孔岩心上段260 cm厚硅藻席沉积中含有丰富的放射虫、丰度高于2×104个/克;中段260~460 cm出现5次放射虫丰度高峰与红粘土的交替旋回沉积;下段460~630 cm红粘土沉积层中放射虫稀少.依据放射虫地层种的初现生物事件,470 cm以深的年龄大于0.34 Ma,表明西菲律宾海硅藻质沉积形成于中更新世以来.此外,受暖水影响控制的Tetrapyle group和Didymocyrtis tetrathalamus tetrathalamus相对丰度在末次冰盛期（LGM）呈现显著的低值期,推测在LGM期西菲律宾海北赤道暖流的影响强度是变弱的.值得注意的是,多囊虫类放射虫的丰度与生物硅含量的变化趋势出现明显的不同步现象,推测4次生物硅含量高峰是由大型硅藻（盘筛藻）的急剧增加导致的,即西菲律宾海LGM期盘筛藻的勃发呈现明显的阶段性强弱变化;进一步发现盘筛藻的4次勃发强盛期对应着胶体虫相对丰度变化的低谷期和中深层冷水种相对丰度变化的高峰期,前者指示上层水体成层化减弱、后者指示中深层水体中营养物增多.据此,认为西菲律宾海LGM期盘筛藻勃发的4次强盛期是由于上层水体成层化减弱、下层水体中丰富的营养物上涌引起.研究结果可为菲律宾海盘筛藻勃发在LGM长时间持续并最终在海底形成厚达近3 m的硅藻席沉积提供了一种可能的解释. 相似文献
2.
<正> 江西早二叠世的硅藻土(岩),比较纯的呈白色,呈砂、粉砂粒状,结构疏松,质软而轻,孔隙度大,吸水性强,镜下具生物结构,大多具水平层理。有的呈黑色,因为含较多的有机藻类。如乐平就有20m厚的黑色硅藻岩。有的呈淡黄色,细如面粉。镜下观察主要为圆心目硅藻:直链藻、三角藻、双菱藻、盒形藻、伞藻等,羽纹目硅藻有针杆藻等。 由于江西的硅藻产出的地质时代比较老,原来的蛋白石均重结晶为石英,使壳面的显 相似文献
3.
LGM热带西太平洋硅藻席古生产力定量评估 总被引：1，自引：0，他引：1
巨型"树荫种"硅藻在成层化大洋中通过"秋季倾泻"勃发模式向深部大洋输出的有机碳通量等于甚至超过"春季勃发"硅藻, 其在第四纪全球气候转型、大洋碳储库演变中的重要地位最近才予以重视.作为大洋碳循环系统的重要参数, 生产力无疑成为探索这一作用的有效窗口.以东菲律宾海的Ethmodiscus rex硅藻席(LDM, laminated diatom mats)岩心WPD-03为材料, 以opal、TOC、bio-Ba等生源组分数据为基础, 运用前人建立的各种生产力经验公式, 试图估算LGM(last glacial maximum)热带西太平洋LDM的古生产力状况.结果显示, LDM沉积期初级生产力、有机碳雨率和埋藏生产力估算合理, 平均分别为248.42 g·m-2·a-1、61.93 g·m-2·a-1和5.27 g·m-2·a-1.估计的初级生产力与代表高生产力的世界大洋各上涌海区可比, 纠正了成层化大洋生产力低下的传统观点, 支持巨型"树荫种"硅藻对大洋有机碳生产与输出的充分贡献.然而, 估算的输出生产力明显不合理, 表明利用基于真光层建立的生产力模型评估次表层水中的巨型"树荫种"硅藻时应格外谨慎, 加强了区别对待"深部"生产力和"表层"生产力的重要性.LGM热带西太平洋LDM的高生产力状况与风尘硅输入的E. rex勃发条件以及还原的沉积环境相一致. 相似文献
4.
基于矿床地质特征,初步分析了江西广昌头陂硅藻土矿床的成因,提出了下一步勘查方向。头陂硅藻土矿赋存于新近系头陂组上段,呈层状和似层状,平面上呈面型展布并延伸至矿段外。上部矿层以圆筛藻属硅藻为主,下部矿层以羽纹目硅藻为优势。新近纪以来,头陂淡水湖泊盆地在温暖、湿润气候条件下,硅藻快速繁殖生长;中新世中晚期以来,盆地外围大面积的铝硅酸盐岩化学风化作用和少量火山灰飘落于水体中为硅藻土形成提供物质条件;硅藻死亡后,其硅质骨骸则保存下来形成硅藻淤泥,经过初步成岩后,便形成了硅藻土层。头陂地区硅藻土矿找矿标志为新近纪新地层和水平层理发育的浅色沉积岩。 相似文献
5.
硅藻群落对环境变化十分敏感,是自然河流水质变化的指示生物。为了解黄龙风景区藻席及藻席嗜冷硅藻群落结构与环境变量的关系,对景区内8个典型景点进行水样和藻席的采集并分析。结果表明,黄龙风景区藻席是以钙华作为基底,丝状藻作为骨架,栖息着大量硅藻的高寒岩溶微生态系统,共鉴定出25属72种硅藻,其中优势种13种,以桥弯藻属（Cymbella）为主。通过冗余分析发现,水温（F=2.8,P=0.02）和溶解硅（F=2.3,P=0.04）是影响黄龙风景区藻席嗜冷硅藻群落结构特征的主要驱动因子,TN是潜在驱动因子。硅藻可以为高寒岩溶区地表水监测提供重要的补充信息,建立完整的硅藻物种数据库,有利于区域水质监测。 相似文献
6.
新第三纪沉积物连续分布在位于日本海东南部Sado岛Oosado山脉的两侧,以中中新统到上新统,Nakayama组由具纹理的、生物扰动的和块状的硅藻泥岩组成。纹理由白色层和黑色层组成并间夹0.02～1mm厚的灰色层。白色纹层主要由硅藻壳组成,而黑色纹层则由如硅藻、海绵骨针、硅鞭藻、放射虫、碎屑颗粒和有机质的混合物组成。生物扰动泥岩中具有Thalassionoides,Planolites,Zoophcos,Chondrites遗迹化石(生物钻孔)。 相似文献
7.
8.
黄海晚更新世以来的硅藻组合及其沉积环境 总被引：3，自引：0，他引：3
黄海更新世晚期以来的硅藻化石,自下而上可划分为五个硅藻带。在Ⅰ带的上下层位,各含一个淡水藻类化石带,显示黄海在大理冰期时,由于气候变冷,海面下降,黄海陆架三次出露成陆。亚间冰期时,气候转暖,海面回升,复为海水淹没,海域中生长着Ⅰ带的各种海生硅藻。随着全新世气候转暖,沉积物中发现Ⅱ-Ⅴ带海生硅藻带,其中Ⅲ带硅藻外洋种比例较大,含亚热带暖海种多,表明此时水温较大,海域扩大,相当于大西洋期,其他各带与全新世各期相当。 相似文献
9.
10.
雷州半岛硅藻土中的硅藻及其化学成分 总被引：4，自引：5，他引：4
本文论述雷州半岛各硅藻土矿床中的硅藻形态和种属。九斗洋和田洋钻孔样品中硅藻种属随深度而变化，由直链藻到了冠盘藻，直到小环藻。总结了对不同种属硅藻的硅质硬过峭同部位的Ｘ射线能谱成分分析和研究结果。 相似文献
11.
Claus‐Dieter Hillenbrand James A. Smith Gerhard Kuhn Oliver Esper Rainer Gersonde Rob D. Larter Barbara Maher Steven G. Moreton Tracy M. Shimmield Monika Korte 《第四纪科学杂志》2010,25(3):280-295
Reliable dating of glaciomarine sediments deposited on the Antarctic shelf since the Last Glacial Maximum (LGM) is challenging because of the rarity of calcareous (micro‐) fossils and the recycling of fossil organic matter. Consequently, radiocarbon (14C) ages of the acid‐insoluble organic fraction (AIO) of the sediments bear uncertainties that are difficult to quantify. Here we present the results of three different methods to date a sedimentary unit consisting of diatomaceous ooze and diatomaceous mud that was deposited following the last deglaciation at five core sites on the inner shelf in the western Amundsen Sea (West Antarctica). In three cores conventional 14C dating of the AIO in bulk samples yielded age reversals down‐core, but at all sites the AIO 14C ages obtained from diatomaceous ooze within the diatom‐rich unit yielded similar uncorrected 14C ages between 13 517 ± 56 and 11 543 ± 47 years before present (a BP). Correction of these ages by subtracting the core‐top ages, which probably reflect present‐day deposition (as indicated by 210Pb dating of the sediment surface at one core site), yielded ages between ca. 10 500 and 8400 cal. a BP. Correction of the AIO ages of the diatomaceous ooze by only subtracting the marine reservoir effect (MRE) of 1300 a indicated deposition of the diatom‐rich sediments between 14 100 and 11 900 cal. a BP. Most of these ages are consistent with age constraints between 13.0 and 8.0 ka for the diatom‐rich unit, which we obtained by correlating the relative palaeomagnetic intensity (RPI) records of three of the sediment cores with global and regional reference curves. As a third dating technique we applied conventional radiocarbon dating of the AIO included in acid‐cleaned diatom hard parts extracted from the diatomaceous ooze. This method yielded uncorrected 14C ages of only 5111 ± 38 and 5106 ± 38 a BP, respectively. We reject these young ages, because they are likely to be overprinted by the adsorption of modern atmospheric carbon dioxide onto the surfaces of the diatom hard parts prior to sample graphitisation and combustion for 14C dating. The deposition of the diatom‐rich unit in the western Amundsen Sea suggests deglaciation of the inner shelf before ca. 13 ka BP. The deposition of diatomaceous oozes elsewhere on the Antarctic shelf around the same time, however, seems to be coincidental rather than directly related. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
12.
The Antarctic Peninsula is one of the most sensitive regions of Antarctica to climate change. Here, ecological and cryospheric systems respond rapidly to climate fluctuations. A 4.4 m thick laminated diatom ooze deposited during the last deglaciation is examined from a marine sediment core (ODP Site 1098) recovered from Basin I, Palmer Deep, western Antarctic Peninsula. This deglacial laminated interval was deposited directly over a glaciomarine diamict, hence during a globally recognised period of rapid climate change. The ultra‐high‐resolution deglacial record is analysed using SEM backscattered electron imagery and secondary electron imagery. Laminated to thinly bedded orange‐brown diatom ooze (near monogeneric Hyalochaete Chaetoceros spp. resting spores) alternates with blue‐grey terrigenous sediments (open water diatom species). These discrete laminae are interpreted as austral spring and summer signals respectively, with negligible winter deposition. Sub‐seasonal sub‐laminae are observed repeatedly through the summer laminae, suggesting variations in shelf waters throughout the summer. Tidal cycles, high storm intensities and/or intrusion of Circumpolar Deep Water onto the continental shelf introduced conditions which enhanced specific species productivity through the season. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
13.
I. O. Murdmaa G. H. Kazarina L. Beaufort E. V. Ivanova E. M. Emelyanov V. A. Kravtsov G. N. Alekhina V. E. Vasileva 《Lithology and Mineral Resources》2010,45(2):154-171
Core MD02-2508 retrieved from the plateau of the continental slope off Baja California recovered a 40-m-thick section of sapropel
(up to 15% Corg), calcareous clay, and diatom ooze with the age of 120 ka at the core bottom. The section is subdivided into three units:
Unit I (Holocene) consists of the laminated sapropel; Unit II comprising oxygen isotope stages (MIS) 2, 3, and 4 is represented
by homogeneous calcareous clay with interbeds of slightly siliceous sapropelic mud; and Unit III (MIS-5) is composed of laminated
sapropelic diatom ooze. Laminated intervals are characterized by the intercalation of two lamina types: (1) dark-colored organic-rich
laminae containing multi-species “oceanic” diatom assemblages, as well as radiolarians, coccoliths, planktonic and benthic
foraminifera; (2) lighter-colored laminae consisting of diatom ooze with the neritic colonial diatom assemblages commonly
composed of one to three species of a single genera. The dark laminae are assumed to be generated within a high productivity
zone over the slope, whereas light ones likely represent diatom mats produced by short-term boisterous phytoplankton blooms,
possibly in the coastal upwelling. 相似文献
14.
Core A9-EB2 from the eastern Bransfield Basin, Antarctic Peninsula, consists of pelagic (diatom ooze-clay couplets and bioturbated diatom ooze) and hemipelagic (bioturbated mud) sediments interbedded with turbidites (homogeneous mud and silt–clay couplets). The cyclic and laminated nature of these pelagic sediments represents alternation between the deposition of diatom-rich biogenic sediments and of terrigenous sediments. Sediment properties and geochemical data explain the contrasting lamination, with light layers being finer-grained and relatively rich in total organic carbon and biogenic silica content. Also, the high-resolution magnetic susceptibility (MS) variations highlight distinct features: high MS values coincide with clastic-rich sections and low MS values correspond to biogenic sections. The chronology developed for core A9-EB2 accounts for anomalous ages associated with turbidites and shows a linear sedimentation rate of approximately 87 cm/103 yr, which is supported by an accumulation rate of 80 cm/103 yr calculated from 210Pb activity. The late Holocene records clearly identify Neoglacial events of the Little Ice Age (LIA) and Medieval Warm Period (MWP). Other unexplained climatic events comparable in duration and amplitude to the LIA and MWP events also appear in the MS record, suggesting intrinsically unstable climatic conditions during the late Holocene in the Bransfield Basin of Antarctic Peninsula. 相似文献
15.
All data necessary to calculate the metal balance for Mn nodules in a well-investigated area of the North Central Pacific are now available. The nodules lie on porous siliceous ooze, and receive more than 96% of their metal content from the underlying ooze by diagenetic mobilisation. Only a very small portion of the metal contained in the sediment has to be mobilised to form the nodules, which explains why the expected depletion of metals from the sediments has never been demonstrated. 相似文献
16.
对地质研究的对象进行科学合理的分类,是地学研究的重要内容之一.为建立科学合理、量化统一、操作简便的深海沉积物分类与命名方案,详细分析国内外深海沉积物分类与命名现状,深刻了解海洋沉积物组成与分布,深入研究深海沉积物的水深、平均粒径和粘土含量3项参数指标,通过分析涂片鉴定粘土、钙质生物、硅质生物这三者的含量、粒度和化学分析之间的差异,建立钙质生物、硅质生物与CaCO3、生物SiO2的量化关系,完成沉降法和激光法粒度分析资料的对比和校正,分析深海沉积物分类与命名的兼容性和可比性.在上述研究成果基础上,自主创新提出深海沉积物分类与命名方案及其关键技术.深海沉积物类型简分法把深海沉积物分为深海粘土、钙质软泥、硅质软泥、粘土-硅质-钙质软泥4类,它能满足一般性海洋地质调查要求,达到基本了解深海沉积物类型的目的,在兼容世界深海沉积物类型现状的同时,充分考虑到混合沉积物的存在.深海沉积物类型细分法在简分法基础上细分了16种沉积物,使分类与命名更加详细和全面,满足海洋地质详细调查研究的要求.深海沉积物分类与命名方案与浅海沉积物分类与命名比较,在图形、类型指标、种类数量、冠字冠名法、混合沉积物表示法、可操作性等方面具有可比性,使浅海到深海的沉积物分类与命名呈渐变和有机联系. 相似文献
17.
东昆仑-阿尼玛卿地区早二叠世的沉积古地理 总被引：5，自引：0，他引：5
东昆仑-阿尼玛卿地区早二叠世古海洋自北而南可分为东昆仑半局限海、托索湖-花石峡礁岛链和阿尼玛卿洋三部分。托索湖-花石峡礁带的主体由块状的礁相灰岩和生物碎屑灰岩所组成 ;东昆仑南坡半局限海中以短轴型的礁岛或碳酸盐建隆及相对较深的岛间盆地相沉积为特征 ;阿尼玛卿洋中则主要以深海软泥及放射虫硅质岩沉积为主, 同时也点缀一些碳酸盐建隆高地。东昆仑南坡半局限海中的礁岛及碳酸盐建隆在分布上缺乏明显的规律性, 但该区生物礁较发育。阿尼玛卿洋中碳酸盐建隆的规模小、分布零星、生物礁相对不发育, 但这些碳酸盐建隆在面上多呈断续的串珠状分布, 具有较明显的规律性。东昆仑南坡半局限海中的岛间盆地相主体以中薄层灰岩夹黑. 相似文献
18.
D. MARC AUDET 《Sedimentology》1995,42(2):355-373
A continuum mechanics model for the gravitational compaction of sediments is derived by assuming that the sediments are normally pressured and in a one-dimensional state of stress. Sediment strength is characterized in terms of effective stress laws adopted from soil mechanics. The model is a relatively simple mathematical formula that gives the porosity as a function of burial depth. The shape of the porosity profile is controlled by two mechanical parameters, the compression index and the void ratio at an effective stress of 100 kPa. The model was verified by analysing the porosity—depth data of oozes and chalk from the Ontong Java Plateau, gathered during Leg 130 of the Ocean Drilling Program. The mechanical parameters of the sediments were estimated using a least-squares method to fit the theoretical profile to the porosity data. The theoretical profile described accurately the ooze porosity data over depth ranges of 100 m or more. However, over smaller length-scales of 10–50 m there were systematic deviations between the theoretical porosity values and the ooze porosity data. The porosity deviations correlated with variations in the mean grain size of the sediments, due in part to changes in the foraminifera abundance. In the case of the oozes, the estimated mechanical parameters were consistent with published values obtained from one-dimensional compression tests. In contrast, the estimated mechanical properties for the chalks differed from published values. The chalk porosities were lower than could be explained by mechanical compaction. This explanation is supported by the compressional (P-wave) velocity data. In the chalk sections, the P-wave velocity increases more rapidly with burial depth than it does in the ooze sections, suggesting that sediment elastic properties are increasing due to interparticle binding. 相似文献
19.
作者通过研究,发现东太平洋洋底沉积物主要是由<0.063mm的伊利石、蒙脱石加混层矿物、高岭石、绿泥石粘土矿物和放射虫、硅藻等组成。具有碱性、比表面积大,离子交换容量大的特点。该成果无异为东太平洋多金属结核分布区的大洋地质学的研究,提供了可贵的环境地质资料。 相似文献