Polar constituents of organic matter rich marls from evaporitic series of the Mulhouse basin     

P. Schaeffer  F. Fache-Dany  J.M. Trendel  P. Albrecht 《Organic Geochemistry》1993,20(8)

A suite of marl samples from the evaporitic series of the Mulhouse basin (France; Lower Oligocene) was studied for its biomarker content, in particular its polar constituents. Novel series of 3-carboxyalkyl steranes and 15-oxo triaromatic ketones were identified by synthesis. The 3-carboxyalkyl steranes probably originate from highly polar precursors yet unreported in living organisms. Our data suggest that micro-algae could be the major source of these compounds which seem to be indicators of high algal input rather than characteristic of evaporitic environments. The 15-oxo triaromatic ketones could be oxidation products of triaromatic steroid hydrocarbons formed during diagenesis, although their formation during work-up procedure could not be excluded.  相似文献   

Fractal analysis of long-range paleoclimatic data: Oxygen isotope record of pacific core V28-239   总被引：1，自引：0，他引：1  

Richard H. Fluegeman Jr.  R. Scott Snow 《Pure and Applied Geophysics》1989,131(1-2):307-313

R/S analysis of the oxygen isotope curve of Pacific core V28-239 yields a fractal dimension of 1.22. This value is considered to characterize global climatic change over the last 2 million years as expressed by changing O¹⁸ ratios and confirms that climatic variations are characterized by long-term persistence. The fractal dimension of 1.22 compares favorably with the approximate fractal dimension of 1.26 for annual precipitation records for nine major cities in the United States. Although the precipitation and oxygen isotope data are measured in different physical units and recorded at different time scales, fractal analysis allows for a mathematical comparison of the two phenomena. Additionally, since the fractal dimensions of the oxygen isotope and precipitation records are similar, it is implied that such fractal dimensions are characteristic of climate change over the spectral range of 10 to 10⁶ years. Given this temperature curves based on fractal parameters of long-term O¹⁸ data could be constructed which would allow examination of characteristics of temperature variation over tens and hundreds of years. Such studies may allow the establishment of limits on natural temperature variation and document the persistence of temperature trends through time. If these trends and limits can be resolved, long-range climatic prediction is feasible.  相似文献   

大布苏湖沉积剖面碳酸盐含量氧同位素特征的古气候意义   总被引：10，自引：3，他引：10  

沈吉  吴瑞金  羊向东  潘红玺  安芷生 《湖泊科学》1997,9(3):217-222

对大布苏湖沉积剖面碳酸盐含量和氧同位素特征研究表明，湖区15000年以来经历了多期冷湿与暖干气候旋回，大约距今6700年左右，气候变干并进入稳定的温暖时期，湖水逐渐高度浓缩，形成了现今的盐碱湖。  相似文献   

Paleoclimatological and paleoenvironmental records since 4 000 a B. P. in sediments of alpine lakes in Taiwan     

Jiann-Yuh Lou  Chen-Tung Arthur Chen 《中国科学D辑(英文版)》1997,40(4):424-431

The 3 310-m-high Chia-min Lake records the climatic history since 4 ka B. P. in Taiwan. The warm/wet period before 2.2 ka B.P. seemed to correspond to the later part of the Holocene Megathermal, and the cold/dry period during 0–2.2 ka B. P. corresponded to the Katathermal. Before the termination of the Megathermal, an especially warm and humid segment (2.2–2.4 ka B. P.) emerged. The paleoclimatic records from Yuen-yang and Chi-tsai Lakes support the notion that the Megathermal in Taiwan terminated during 2—2.3 ka B. P. A warm segment (820–1 320 AD) in the Katathermal could be considered the Medieval Warm Period. The climate turned cold and dry after 1 320 AD and this indicated the onset of the Little Ice Age. These paleoclimatic variations are also in good agreement with those recorded in Great Ghost Lake.  相似文献   

Coastal Massachusetts pond development: edaphic,climatic, and sea level impacts since deglaciation     

Marjorie Green Winkler  Patricia R. Sanford 《Journal of Paleolimnology》1995,14(3):311-336

Kettle ponds in the Cape Cod National Seashore in southeastern Massachusetts differ in their evolution due to depth of the original ice block, the clay content of outwash in their drainage basins, and their siting in relation to geomorphic changes caused by sea-level rise, barrier beach formation, and saltmarsh development. Stratigraphic records of microfossil, carbon isotope, and sediment changes also document late-glacial and Holocene climatic changes.The ponds are separated into 3 groups, each of which follow different development scenarios. Group I ponds date from the late-glacial. They formed in clay-rich outwash, have perched aquifers and continuous lake sediment deposition. The earliest pollen and macrofossil assemblages in Group I pond sediments suggest tundra and spruce-willow parklands before 12 000 yr B.P., boreal forest between 12 000 and 10 500 yr B.P., bog/heath initiation and expansion during the Younger Dryas between 11 000 and 10 000 yr B.P., northern conifer forest between 10 500 and 9500 yr B.P., and establishment of the Cape oak and pitch pine barrens vegetation after 9500 yr B.P. Sedimentation rate changes suggest lowered freshwater levels between 9000 and 5000 yr B.P. caused by decreased precipitation on the Atlantic Coastal Plain. Lake sediment deposition began in the middle Holocene in Group II ponds which formed in clay-poor outwash. These ponds date from about 6000-5000 yr B.P. In these ponds sediment deposition began as sea level rose and the freshwater lens intersected the dry basins. The basal radiocarbon dates of these ponds and stable carbon isotope analyses of the pond sediments suggest a sea-level curve for Cape Cod Bay. Holocene topographic changes in upland and the landscape surrounding the ponds is reconstructed for this coastal area.Group III ponds in the late Holocene landscape of the Provincelands dunes originated as interdunal bogs about 1000 yr B.P. and became ponds more recently as water-levels increased. Peat formation in the Provincelands reflects climatic changes evident on both sides of the Atlantic region.This is the 8th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.  相似文献   

苏北淮安盐盆杨槐区块浦二段盐韵律特征及其古气候意义     

张文淼  丁国生  于兴河  完颜祺琪  垢艳侠  吴子瑾  孙乐  付超 《现代地质》2019,33(2):370-378

盐湖沉积因具有成盐多期性和连续完整性的特点,是恢复成盐期古环境的重要研究对象,形成的不同级次盐韵律记录了不同尺度周期下古气候的干湿变化。上白垩统浦口组是淮安盐盆的主要含盐层系,对含盐层段盐韵律的研究有助于恢复该地区成盐期的古气候特征。在对资料井A1井取心段岩心精细观察和岩样矿物成分分析的基础上,分析资料井岩性的垂向变化,对浦口组盐韵律特征进行识别并划分。根据盐韵律对古气候的指示作用研究成盐期区块短尺度气候周期下的古气候变化。将淮安盐盆杨槐区块浦口组划分出Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ级韵律,识别出完整的盐韵律组合,即泥岩—钙芒硝质盐岩—盐岩—钙芒硝质盐岩。含盐段中广泛发育暖温相矿物钙芒硝,指示气候特征为炎热的暖旱型。在Ⅳ级韵律尺度下建立了气候干湿性变化曲线,表明区块气候干湿性波动频繁,但仍以干旱为主,韵律厚度大致反映了气候波动频率大小。  相似文献   

鄂尔多斯盆地南缘上二叠统——中下三叠统地球化学特征及其古气候、古环境指示意义     

谭聪  袁选俊  于炳松  刘策  李雯  崔景伟 《现代地质》2019,33(3):615-628

为探索陆相湖泊环境记录中二叠纪—三叠纪之交古气候演化的信息,以鄂尔多斯盆地南缘陕西铜川石川河剖面上二叠统石千峰组(P3s)和三叠系的刘家沟组(T1l)、和尚沟组(T1h)、纸坊组(T2z)为研究对象,对界面上下地层开展了系统的矿物学、岩石学和地球化学研究。通过主量和微量元素、碳氧同位素以及TOC测试对古盐度、古氧化还原环境和古气候演化规律进行分析。测试结果显示在二叠系—三叠系(P/T)界线附近主、微量元素和碳、氧同位素发生较明显的变化,气候环境代用化学指标的波动指示了从晚二叠世至早中三叠世鄂尔多斯盆地的古气候、古环境的变化。研究结果表明上二叠统石千峰组形成于河流-三角洲沉积环境,氧化程度相对低,古气候相对温暖湿润;下三叠统刘家沟组与和尚沟组的紫红色砂泥岩代表水体较浅的河流-三角洲相,强氧化环境,气候干旱炎热;而到中三叠统纸坊组沉积期,湖平面上升,元素的迁移作用加强,氧化程度变弱,气温降低,气候转为半干旱半湿润气候。碳同位素分析结果显示,鄂尔多斯盆地陆相P/T界线上δ^13CPDB存在显著负偏,与全球范围内的海相P/T界线具有一致性,说明在华北地台陆相P/T界线上同样存在气候突变和生物灭绝等重大地质事件的沉积记录,与海相地层可对比。  相似文献   

江西九江红土生物标志化合物的分布特征及其古气候环境意义     

彭红霞  詹成  马瑞元  顾延生  胡圣虹 《地球学报》2019,40(3):447-455

为了探求江西九江红土地层中所记录的古气候环境信息,论文在对江西九江红土剖面的野外地貌、岩性和相关沉积环境调查分析基础上,利用气相色谱-质谱联用仪对正构烷烃、一元正脂肪酸等生物标志化合物进行了研究,着重分析了正构烷烃和一元正脂肪酸的来源及其碳数分布特征。结果显示:江西九江红土剖面上部均质红土中正构烷烃的CPI、∑C_(21)~–/∑C_(22)~+及一元正脂肪酸的CPI_L值均大于其下部的网纹红土,且波动较为明显,表明网纹红土的形成气候比其上的均质红土形成时期气候暖湿,反映了中更新世中期(600～300kaBP)的极端暖湿期;正构烷烃的∑C_(21)~–/∑C_(22)~+、(C_(15)+C_(17)+C_(19))/(C_(27)+C_(29)+C_(31))、(C_(16)+C_(17)+C_(18))/(C_(29)+C_(31)+C_(33))、C_(17)/C_(31)在剖面上表现出一致的旋回性变化,反应了江西九江中更新世以来气候的冷暖旋回变化。结果表明红土地层中的生物标志化合物具有很好的古气候环境意义。  相似文献   

豫西宜阳地区晚二叠世晚期—早三叠世沉积记录及其对古气候变化的响应          下载免费PDF全文

邢智峰  林佳  周虎  李妲  齐永安  郑伟 《高校地质学报》2019,25(3):401

晚二叠世-早三叠世宜阳地区位于东特提斯低纬度地区的华北板块南缘,发育一套连续且沉积特征显著的陆相碎屑 岩相沉积,是研究陆相晚二叠世-早三叠世古环境与古气候变化的理想地层。本文在前人研究与野外实测的基础上,采用 岩石学、沉积学、古生物学方法综合分析研究区的沉积记录,识别出宜阳地区在该时期由陆源近海的滨湖沉积环境向河流 沉积环境过渡的古环境,重建了晚二叠世晚期-早三叠世宜阳地区的古地理面貌。沉积特征显示,此期整体气候条件为炎 热-半干旱,并且在长兴期末期与奥伦尼克期早期出现了极端干旱气候,可能是受到当时全球性巨型季风环流的影响。这 一时期的古气候与古环境的变化可能对二叠纪末陆地大灭绝事件起到了推动作用,并抑制了早三叠世生物复苏的进展。  相似文献   

Paleoclimatic changes in southern Africa during the intensification of Northern Hemisphere glaciation: evidence from ODP Leg 175 Site 1085     

B. A. Christensen  J. L. Kalbas  M. Maslin  R. W. Murray 《Marine Geology》2002,180(1-4):117-131

Pliocene age sediments from Ocean Drilling Program Leg 175, Site 1085-A and B in the Cape Basin were analyzed to investigate the impact of the intensification of Northern Hemisphere glaciation (INHG) on the South Atlantic Benguela Current system from 4 to 2 Ma. Proxies for productivity (concentrations and mass accumulation rates of total organic carbon, carbon to nitrogen ratios, percent calcium carbonate, and percent biogenic silica) as well as weight percent sand (a proxy for preservation or winnowing) peak at 3.2, 3.0, 2.4, and 2.25 Ma. Normative calculations of allied trace and major elemental determinations indicate synchronous increases in productivity peaks, as well as high concentrations and accumulations of terrigenous sediments. Coeval increases in hemipelagic sedimentation and productivity indicators could be the result of enhanced eolian sedimentation resulting from strengthened winds, leading to elevated rates of upwelling and enhanced productivity. However, rapid burial, as indicated by high sedimentation rates, could also enhance preservation. The very high concentrations (>30%) and accumulations (up to 60 g/cm²/kyr) limit the likelihood that eolian sedimentation was the only transport mechanism, invoking an additional fluvial source. Rapid burial by either eolian or fluvial transport links these intervals of enhanced preservation and productivity with continental climate changes resulting from (1) increased winds and/or dust availability due to higher aridity in the Namibia/northern South Africa region; (2) lowered sea-level related to increased ice volume; (3) increased sediment load due to wetter conditions in the continental interior; or (4) some combination. Peaks at 3.2, 2.4 and 2.25 Ma are coincident with maximum precession, suggesting a link between hemipelagic sedimentation and enhanced monsoonal circulation over southern Africa. The Site 1085 sedimentary record during the INHG seems to be controlled by low-latitude processes linked to precession rather than hig-latitude processes.  相似文献