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1.
主要研究了意大利上新统3个剖面Punta Piccola、Cape Spertivento以及Punta Rossello蛋白石含量的变化，综合其它古环境指标对非洲季风和地中海表层生产力加以分析，研究表明，Punta Piccola剖面和Cape Spertivento剖面各古环境指标对岁差周期影响的响应明显而单纯，即岁差低值，对应氧同位素偏负，有机碳和蛋白石高值以及碳酸盐低值，说明地中海表层生产力明显受到岁差的驱动。岁差驱动下的北非夏季风导致尼罗河泛滥，带来的丰富营养元素使得生产力剧增，同时淡水注入，阻碍了水体的垂向交换，直接导致了海底的缺氧环境，硅藻利用深层营养产生勃发，并组成“藻席”，快速沉降到海底，使得有机碳迅速埋葬和保存，从而引发了腐泥层的形成。Punta Rossello剖面硅藻层证实了“藻席”的存在，但是蛋白石含量并不高。
[HT5H]关 键 词:[HT5K]
[HT5H]中图分类号： 文献标识码：A[HT5SS][HK] 相似文献
2.
南海南部50万年以来碳酸钙和有机碳记录及其揭示的东亚夏季风演化 总被引：1，自引：0，他引：1
为了解南海南部第四纪冰期旋回中表层生产力的变化与东亚夏季风的演化关系,通过对南海南部MD05-2897孔晚第四纪500ka以来碳酸钙和有机碳含量及堆积速率高分辨率的研究发现,碳酸钙含量及堆积速率表现出明显的冰期-间冰期旋回变化,而有机碳的含量及堆积速率则主要呈现频率更高的周期性变化.碳酸钙和有机碳含量及堆积速率都在间冰期时增加,冰期时降低,反映了间冰期时夏季风的增强导致上升流的加强和营养物质的增加,促使表层生产力提高.碳酸钙和有机碳含量及堆积速率具有100ka偏心率周期、40ka斜率周期、20ka岁差和10ka半岁差周期等最为丰富的频谱,显示出低纬海区对轨道周期响应的特色.碳酸钙和有机碳的堆积速率与北半球低纬夏季日射量吻合较好,说明岁差相关的北半球低纬夏季太阳辐射量的变化可能是东亚夏季风强度变化的主要控制因素,而与全球冰量相关的气候变化可能是次要因素. 相似文献
3.
南海北部一百万年以来的表层古生产力变化：来自ODP1144站的蛋白石记录 总被引：7，自引：1，他引：6
通过南海北部ODP 1144站蛋白石含量测定及其堆积速率的计算,并结合氧同位素记录等相关资料,获得南海北部1050ka以来高分辨率的表层古生产力变化与冰期旋回和东亚季风的关系。约900ka以来,蛋白石含量及其堆积速率较900ka以前明显增加,反映了“中更新世革命”事件之后,全球气候变冷,并导致表层生产力的提高。由于第四纪冰期旋回中的冬、夏季风的加强,加上1144站特殊的地理位置,使该站在冰期时表层生产力增加,间冰期时表层生产力降低。浮游有孔虫氧同位素记录与蛋白石含量及其堆积速率的时间序列频谱分析结果显示,三者均出现了相对应的偏心率周期、斜率周期和岁差周期,说明该站表层生产力的变化主要受地球轨道周期的驱动。 相似文献
4.
在AMS14C精确定年的基础上,通过南海北部MD05-2905站高分辨率的氧同位素、粒度、元素分析,其结果显示所有指标均在11.2～8.5kaB.P.期间发生异常,根据夏季风指标认为这是夏季风极强事件。将本站位相同纬度（20°N）的夏季平均日辐射量与季风指标进行对比,发现全新世早期（11.2～8.5kaB.P.）东亚夏季风极强事件对应着夏季太阳辐射量最大值和热带辐合带（ITCZ）的位置向北移动,说明全新世早期夏季风突然增强可能是在岁差周期控制下,较高的太阳辐射量驱动了热带辐合带（ITCZ）及其有关的雨场向北移动,在南海北部产生了大量的降水,导致氧同位素偏负、碳酸盐的含量较低以及线性沉积速率较高。这与前人对相邻地区湖光岩玛珥湖的孢粉研究、江西南岭地区泥炭的记录以及中国南方石笋记录的研究结果相吻合。该季风最强事件与阿拉伯海发现的早全新世季风最强事件以及根据格陵兰冰芯记录的早全新世甲烷最大值推测低纬地区湿地扩张相一致,这反映了南海北部全新世早期与全球低纬地区早全新世气候变化格局一致。 相似文献
5.
6.
深海记录中的热带过程及其周期性 总被引：6，自引：4，他引：2
地球运行轨道参数包括偏心率、斜率和岁差, 在地质时期分别具有413ka和100ka、41ka、23ka和19ka的周期, 它决定地表太阳辐射在不同纬度和季节的周期性变化.太阳辐射变化中, 岁差周期最为明显, 斜率周期在中高纬度比较明显, 而偏心率周期本身作用微弱, 主要通过调控岁差周期的变幅影响气候.传统的地球轨道驱动理论认为, 北半球高纬的太阳辐射决定全球冰量和地表的气候变化, 轨道周期可能线性地反映到气候变化的周期中去.实际的深海记录反映的情况并非如此, 尤其在热带海区, 气候替代性指标的周期性与太阳辐射的周期性既存在相似性, 也存在较大区别.相似性在于, 热带海区的气候替代性指标均表现出较强的岁差和斜率周期, 而且通常情况下岁差周期的强度要高于斜率周期的强度, 说明热带海区的气候变化受控于岁差调控的太阳辐射的变化; 区别性在于, 热带海区气候替代性指标通常表现出较强的不容忽视的100ka、413ka的偏心率周期和10ka左右的半岁差周期, 而且100ka、413ka的偏心率周期还是季风系统的典型周期, 说明热带海区的气候变化并不是简单的线性响应太阳辐射的变化, 也不完全受北半球高纬的控制, 而是具有自身的特性. 相似文献
7.
沉积物中有机碳、生物碳酸盐和生物硅等生源组分的埋藏速率在很大程度上受到海洋古生产力的控制,常常被用作古生产力的替代指标.本文利用TOC、生物硅及CaCO3等生源组分探讨冲绳海槽中部DGKS9604孔(28°16.64'N,127°01.43'E;水深766m;柱长10.76m)距今28ka以来陆源物质输入和古环境演化对海洋生产力的影响.研究结果表明,在冬季风较强的末次冰期晚期(28～22kaB.P.),长江直接输运大量的陆源营养物质进入冲绳海槽,古生产力较高;在末次盛冰期(LGM,22～18kaB.P.),虽然河口距离海槽区更近,但大陆流域降水匮乏,河流人海径流量偏低导致海槽陆源营养物质明显减少,生产力降低,表现在生物硅和有机碳堆积速率明显降低;冰消期早期生产力与末次盛冰期相比并未明显降低,此阶段气候回暖,大陆流域降雨增加,陆源物质输入相对较高.全新世早期,古生产力快速下降,既反映海平面降低,陆源物质输入减少.还可能与冰消期寡营养盐的黑潮在海槽加强有关.DGKS9604孔CaCO3含量及堆积速率变化的总体趋势与有机碳和生物硅相反,表现为末次冰期晚期低.冰消期以来逐渐升高,一方面反映陆源物质输入的稀释作用;另一方面与黑潮加强致使钙质生物生产力增强有关.此外,15～7kaB.P.期间CaCO3含量及其堆积速率有几次明显降低,可能对应黑潮减弱、陆源冲淡水较强的环境事件. 相似文献
8.
《地球科学进展》2016,(3)
首先综述了现代热带海洋生产力的分类与影响因素,然后讨论了古生产力替代性指标的分类与各类方法的优点与局限性。在此基础上,通过收集整理前人使用不同替代性指标对热带海洋古生产力重建的结果,讨论了热带海洋古生产力记录的特征、周期性与驱动机制。发现从末次冰期到全新世热带海洋古生产力在冰期时明显偏高,但冰期生产力高间冰期生产力低的规律并不一直适用,MIS 22前后西太平洋初级生产力在冰期—间冰期的变化发生反转。热带海洋古生产力的周期性也与高纬海区显著不同,岁差和斜率的信号更为显著。还存在约30 ka等不同轨道周期叠加之后形成的周期。颗石藻计算的海洋生产力可能存在约400 ka周期,这对全球碳同位素的影响有待深入研究。 相似文献
9.
中国西部晚中新世以来气候演化初探──以甘肃临夏红色盆地中Cl-含量变化为例 总被引：5，自引：0，他引：5
Cl-是封闭湖盆中反映气候变化的敏感指标。临夏盆地晚新生代地层Cl-含量变化表明,气候的长期演化呈现明显的阶段性与周期性,在约6.3Ma气候突然产生显著的由湿变干,并于5.3～4.5Ma达到极端干旱,其干旱程度是第四纪早期的33倍,低频上,气候呈现出约400万年的干湿波动,在晚中新世与早上新世,与同周期的全球热冷（凉）波动相对,而在第四纪早期,则与冷暖相对,可能反映亚洲季风系统于晚上新世才开始逐步形成,并于第四纪初建立,3.4Ma开始强烈隆升的青藏高原可能与此密切相关。 相似文献
10.
藏南地区白垩纪时期广泛沉积了一套海相富有机质沉积物,而其中与C-T界线缺氧事件有关的黑色页岩引起了广泛关注。但是,其有机碳含量与西特提斯相比明显偏低。因此,有关该区对海相白垩纪富有机质沉积影响机制的认识显得尤为重要。文中选取前人研究程度较高的岗巴宗山Ⅱ剖面、定日贡扎剖面和江孜加不拉剖面、床得剖面,利用其相关数据,定量计算了这些剖面的沉积速率、堆积速率和古生产力值。结果表明,藏南地区沉积速率以C-T界线时期最高,而岗巴、定日地区与江孜地区的沉积速率表现出较大的差异,这主要与沉积环境有关;并且在沉积速率<4cm/ka时,随着沉积速率的增加,有机碳含量随之增加,而沉积速率较大时,则关系不明显。江孜地区初级生产力较低,其缺氧期黑色页岩的形成并不是高生产力的结果,可能与缺氧条件的保存作用相关;对于岗巴和定日地区而言,尽管计算的古生产力较低,但碳同位素正偏以及推测存在的沿岸上升洋流表明,该区白垩纪富有机质沉积拥有高的初级生产力和缺氧的保存条件,表明该区有良好的古海洋条件,富有机质沉积的形成是高生产力、缺氧的保存条件以及低的沉积速率(<4cm/ka)共同作用的结果。而产生有机碳偏低,从而使得计算的古生产力值偏低的原因,则可能与成岩后期强烈的风化作用,导致有机碳的损失有关;另外定日地区C-T期有机碳含量偏低则还与其沉积物粒度有关。 相似文献
11.
Soheir H. El-Shazly 《Journal of African Earth Sciences》2011,59(2-3):283-294
Eight pectinid shells were collected and subjected to quantitative study using δ18O and δ13C isotopic analysis in order to study the paleoenvironment which prevailed during their calcification. The scalerochronological variations in δ18O and δ13C values, among these shells are also discussed. The Early Miocene pectinid shells display highly depleted δ18O and δ13C signature as a result of paleo-meteoric water with heavy rainfall that was produced by Tropical Cyclones when the Mediterranean Sea was open. The Early Pliocene pectinid shells reveal depleted δ18O values, related to the influx of fresh water influenced by monsoonal activity following the formation of the Tibetan Plateau. Their enrichment in the δ13C isotopic excursion is referred to high productivity of the Indian Ocean, which was the main source of the Red Sea water. The Pleistocene pectinid shell shows highly depleted δ18O and δ13C signature with obvious diagenetic shell structure, indicating that a wetter humid climate prevailed during the Early–Middle Pleistocene and long sub-arial exposure of the shell. The Recent Mediterranean pectinid shell displays slight enrichment in δ18O and δ13C values referring to deeper inhabitation of this species with a low temperature and high salinity environment. The scalerochronological variations in both δ18O and δ13C values, along these shells is referred to seasonal variations or kinetic effects. 相似文献
12.
《Quaternary Science Reviews》2007,26(17-18):2042-2066
A review of seven outstanding issues on Mediterranean palaeoenvironments is presented. These are related to the dominant orbital pacing of climate variability, the length of the interglacial vegetation succession, the influence of the African summer monsoon, the seasonality of precipitation during boreal insolation maxima, the moisture balance during glacial maxima and the appearance of the mediterranean-type climate rhythm and evolution of mediterranean sclerophyllous plants. What emerges is that (1) marine δ18Oplanktonic and SST records show that precession has been a fundamental tempo of Mediterranean climate change, representing both a low-latitude signal (runoff from North Africa) and the direct influence of insolation at Mediterranean latitudes, but high-latitude glacial effects (41-kyr and 100-kyr cycles) became superimposed after 2.8 Ma. Sapropel and dust deposition patterns in marine cores reveal that obliquity also has an effect on Mediterranean climate through dry–wet oscillations, which are independent of glacial–interglacial variability. (2) The temperate part of interglacial vegetation succession has a duration of approximately half a precession cycle. This persisted during the interval of obliquity-dominated glacial cycles (∼2.8–1 Ma), with distinct forest successions following the precessional cycles. However, these are not always separated by an open vegetation phase because of minimal ice growth, producing an impression of a prolonged interglacial forest interval. (3) The effect of an enhanced African monsoon during summer insolation maxima has been mainly indirect, in terms of Nile discharge and runoff along the North African coast, leading to increased freshwater input into the Mediterranean Sea, reduced deep-water ventilation and sapropel deposition. (4) The notion of an accentuated summer rain regime in the northern Mediterranean borderlands also contributing to a freshening of the Mediterranean Sea during boreal insolation maxima is not supported by the available evidence, which suggests increased summer aridity. (5) Recent improvements in chronological precision and data resolution point to an increase in aridity and decreased temperatures during the Last Glacial Maximum (21±2 ka), but suggest an increase in effective moisture during the immediately preceding interval of 24–27 ka. (6) The mediterranean-type climate is not exclusively a post-3.6 Ma phenomenon, but may have appeared intermittently during the course of the Tertiary (or before). (7) If that is the case, then the paradigm that the sclerophyllous evergreen habit represents a pre-adaptation to summer drought may need re-evaluation. 相似文献
13.
研究季风区小冰期的结构特征和区域响应有助于深入了解季风系统与地球内外驱动力的耦合关系。利用湖北神农架永兴洞YX275石笋的7个230Th年龄和120个碳同位素数据，建立了1 360~1 955 AD期间5年分辨率的石笋碳同位素序列。石笋δ13C与δ18O记录在长期趋势上有很好的对应关系，对小冰期气候响应明显，δ13C记录在大尺度季风环流影响下主要反映了局域湿度变化特征。δ13C序列在1 453~1 890 AD显著正偏，表明小冰期时湿度明显降低。此外，石笋δ13C与亚洲夏季温度、南方涛动指数和热带辐合带记录有较好的一致性，表明亚洲大陆夏季温度和太平洋水汽可能通过影响夏季风的强弱来调控湖北地区的湿度变化。在小冰期内部，δ13C记录在1 450~1 550 AD和1 790~1 830 AD出现进一步正偏，这些振荡分别对应于太阳活动的Sp?rer和Dalton极小期，暗示太阳活动减弱期对中国中部小冰期水文振荡的进一步调控作用。 相似文献
14.
A 650-m-thick sequence of fluvio-lacustrine sediments from the Yuanmou Basin in southwest China was analyzed at 20-cm intervals for grain-size distribution to provide a high-resolution terrestrial record of Indian summer monsoon variations during the Pliocene. The concentrations of the clay and clay-plus-fine-silt fractions are inferred to reflect the water-level status of the lake basin related to the intensity of the Indian summer monsoon and high concentrations reflect high lake levels resulting from the intensified summer monsoon. The frequency of individual lacustrine mud beds is considered to reveal the frequency of the lakes developed in the basin associated with the variability of the Indian summer monsoon and an increased frequency of the lakes reveals an increased variability of the summer monsoon. The proxy data indicate that the Indian summer monsoon experienced two major shifts at 3.57 and 2.78 Ma and two secondary shifts at 3.09 and 2.39 Ma during the Pliocene. The summer monsoon displayed a general trend of gradual intensification during the period of 3.57–2.78 Ma, coeval with an accelerated uplift of the Tibetan Plateau, implying a close link between the monsoon intensification and the plateau uplift. At 2.78 Ma, the summer monsoon was markedly weakened, synchronous with the formation of extensive Northern Hemisphere ice sheets, denoting a quick response of the monsoon regime to the Northern Hemisphere glaciation. The variability of the summer monsoon decreased at 3.09 Ma and increased at 2.39 Ma, presumably suggesting that variations of the Indian monsoon would be modulated by the initiation and periodic fluctuations of ice-sheet covers in Northern Hemisphere high latitudes. 相似文献
15.
黄土中含有较为丰富的碳酸盐,其中次生碳酸盐记录了成壤时期的气候和环境,可以用来重建古气候.测试了末次盛冰期和全新世早期青藏高原东北部乐都、中国东北和新疆巴音布鲁克黄土中次生碳酸盐的δ18O值,结果显示高原东北部这两个时期的δ18O值分别为-1.38‰和-5.58‰,比该地区现代季风气候条件下次生碳酸盐δ18O理论值分别高5.74‰和1.54‰.温度的差异不足以导致次生碳酸盐δ18O值如此幅度的变化.同时,末次盛冰期和全新世早期乐都地区黄土中次生碳酸盐的δ18O值比同时期黄土高原和东北地区等东亚季风区明显偏正约2.0‰~6.2‰,但其与新疆等西风区次生碳酸盐的δ18O相近.这些不同时期黄土中次生碳酸盐的δ18O值的分布特征及空间差异,可能反映东亚夏季风夹带的水汽可能不是青藏高原东北部末次盛冰期和全新世早期降水最重要的来源,而西风降水和（或）局部水汽蒸发循环对该地区的降水可能有重要贡献.青藏高原东北部黄土次生碳酸盐的δ18O值从末次盛冰期到全新世早期逐渐降低,这可能是由于气候由干冷向暖湿转变、有效湿度增加而导致的.有限的数据表明不同气候带（青藏高原东北部、东亚季风区和西风带）的黄土中次生碳酸盐氧同位素存在明显差异,它所代表的气候意义值得进一步的深入研究. 相似文献
16.
湖北神农架石笋年纹层与氧碳同位素关系 总被引：2，自引：1，他引：1
基于湖北神农架青天洞石笋U 系测年和年纹层统计结果,分别建立了末次盛冰期( 17 474± 174～ 16 105± 151 aB. P. )和全新世大暖期( 6 935. 4± 33. 8～6 137± 48 aB. P. )长达1 000余年的两个石笋年纹层生长序列。全新世大暖期年纹层平均厚度( 265μm) 约为末次盛冰期( 102μm)的2. 5倍,说明在间冰期东亚季风增强时石笋沉积速率较大,冰期时则相反。两支分辨率为4～ 8年的石笋年纹层厚度与δ13 C变化曲线对比显示: 在百年尺度上,石笋年纹层厚度与δ13 C变化曲线均呈良好的相关性(相关系数分别为- 0. 53和- 0.60) ,说明两指标可能受洞穴上覆土壤带CO2 产率这一主控因素的影响。当上覆土壤层生物活动增强, CO2 分压较高时,导致石笋δ13 C值偏负、生长速率增大。然而,在相同尺度上,两支石笋δ18O变化与对应的δ13 C及年纹层厚度之间的相关性较弱,反映研究地点上覆土壤层CO2产率对东亚夏季风强弱变化响应关系比较复杂。 相似文献
17.
基于山西阳泉市莲花洞石笋8个230Th年代和109个δ13C数据,获取了末次冰期54.5~41.1 ka BP期间平均分辨率为120年的δ13C记录。综合对比亚洲季风区29°~41°N之间5条独立定年的、高分辨率石笋δ13C记录表明:不同洞穴石笋δ13C记录在相同生长时段具有较好的重现性,δ13C指标能够有效指示洞穴上覆地区土壤CO2产率,从而反映洞穴外部环境与季风气候的变化。δ13C记录的5个千年尺度亚洲夏季风增强事件在定年误差范围内响应于格陵兰冰芯记录的Dansgaard-Oeschger（DO）10~14事件,而2个弱季风过程与北大西洋钻孔记录Heinrich 5和Heinrich 5a事件密切联系。这种石笋δ13C记录的空间一致性表明亚洲夏季风及其控制下的区域生态环境波动在千年尺度上通过海－气耦合响应于北高纬气候变化。 相似文献
18.
Terrigenous plant wax inputs to the Arabian Sea: Implications for the reconstruction of winds associated with the Indian Monsoon 总被引：1，自引：0，他引：1
Kristina A. Dahl Delia W. Oppo Konrad A. Hughen Frank Sirocko 《Geochimica et cosmochimica acta》2005,69(10):2547-2558
We have determined the accumulation rates and carbon isotopic compositions (δ13C) of long-chain (C24-C32) terrigenous plant wax fatty acids in 19 surface sediment samples geographically distributed throughout the Arabian Sea in order to assess the relationship between plant wax inputs and the surrounding monsoon wind systems. Both the accumulation rate data and the δ13C data show that there are three primary eolian sources of plant waxes to the Arabian Sea: Africa, Asia, and the Arabian Peninsula. These sources correspond to the three major wind systems in this region: the summer (Southwest) monsoon, the winter (Northeast) monsoon, and the summer northwesterlies that blow over the Arabian Peninsula. In addition, plant waxes are fluvially supplied to the Gulf of Oman and the Eastern African margin by nearby rivers. Plant wax δ13C values reflect the vegetation types of the continental source regions. Greater than 75% of the waxes from Africa and Asia are derived from C4 plants. Waxes delivered by northwesterly winds reflect a greater influence (25-40%) of C3 vegetation, likely derived from the Mesopotamian region. These data agree well with previously published studies of eolian dust deposition, particularly of dolomite derived from the Arabian Peninsula and the Mesopotamian region, in surface sediments of the Arabian Sea. The west-to-east gradient of plant wax δ13C and dolomite accumulation rates are separately useful indicators of the relationship between the northwesterly winds and the winds of the Southwest monsoon. Combined, however, these two proxies could provide a powerful tool for the reconstruction of both southwest monsoon strength as well as Mesopotamian aridity. 相似文献
19.
Magnetic susceptibility (MS) is one of the most important indicators of the East- Asia summer monsoon. Presented in this study is a high resolution magnetic susceptibility record from the Xifeng section, which consists of Quaternary loess-paleosol sequence and Pliocene red clay. Variations in magnetic susceptibility are well correlated with the δ18O record in deep-sea sediments and the eolian flux of Greenland. The climatic evolution in the Xifeng section shows that since the Late Tertiary, the driving forc... 相似文献