Sources of organic matter and paleo-environmental implications inferred from carbon isotope compositions of lacustrine sediments at Inexpressible Island, Ross Sea, Antarctica

The carbon isotopic composition of organic matter （δ^13Corg） was determined in two sediment cores （IIL1 and IIL9） recovered from Inexpressible Island, Ross Sea, Antarctica, and analyzed to identify the sources of that organic matter. The δ^13Corg values of sediments of IIL9 were found to vary between -14.6‰ and -11.6‰, with a mean of-13.4‰ （n=48）. These values were significantly higher than those of IIL1 sediments which varied between -23.2‰ and -20.4‰, with a mean of-21.8%o （n=55）. The variation in δ^13Corg values in these two sediment cores indicate different sources of organic matter, The relatively high 6~3Corg values in IIL9 are in accordance with a source from algae, while the low δ^13Corg values in IIL1 evince significant influence from penguin guano with algae as the secondary source. Compared with the reference data from other high-latitude lake sediments and plants, the δ^13Corg values in IIL9 were extremely high, a result likely related to intense competition for CO2 assimilation among algal species during the growing season in this relatively shallow pond. These results indicate that sedimentary δ^13Corg is a reliable proxy for paleo-primary productivity in ponds at Inexpressible Island.

Application of sedimentary pyrite in paleo-environment：a case study of Meihe Formation

The indices related to sedimentary pyrite are widely used in paleo-environmental studies; however its application principles and flaws have not been presented in detail so far,therefore it is necessary to review the controlling factors of them. In this study the authors described the application principles in detail,including pyrite morphology,C/S ratio,DOP,size distribution,sulfur isotope,and further discussed the C-S-Fe system in oil shale in Meihe Formation which indicates oxic or suboxic conditions during oil shale deposition. The concentration of TOC and S in the oil shale in Meihe Formation is more than that in background mudstone,and the pyrite formation is limited by sulfate. Therefore studying the indices related to pyrite proves to be of great importance.

Paleo-environmental conditions,paleoclimatic significance and effects of weathering on clay deposits in the Lower Benue Trough,Nigeria.Mineralogical approach

Combined methods for mineralogical identifications were used to characterise the clay deposits within the Lower Benue Trough of Nigeria to interpret paleo-environmental conditions,the paleoclimatic significance of the trough,and effects of weathering on the minerals as factors that favour its deposition/accumulation within the trough which host other important industrial minerals like coal,barite,limestone etc.Bulk-sample random-powder XRD data and data for clay fractions deposited onto zero-background quartz plates were measured.The samples contained kaolinite,vermiculite,and traces of smectite,and the non-clay phases included quartz,microcline,and muscovite.All samples were unaffected after glycolation,confirming the absence of significant smectite.Muscovite was characterized by the nature of its 10Åbasal peak with a width of<0.10°2θ,which was very sharp.DTA/TGA results support the presence of kaolinite,and the characteristic kaolinite O-H,Al-OH,Si-OH and Si-O-Al FTIR bands also confirmed its presence.Vermicular and book-like morphologies were observed under the SEM,typical of kaolinitic clay from in situ alteration.High kaolinite abundance in these sediments is consistent with intense weathering of parent rocks rich in Al under wet/tropical paleo-climatic conditions with fresh and/or brackish water conditions in a continental setting.The variety of observed morphologies suggests that the deposits suffered more of chemical weathering.The clay deposits in Lower Benue Trough are quartz-rich,kaolinitic and derived from the chemical weathering of Al-rich source rocks.

PALEO-ENVIRONMENTAL RECONSTRUCTION DURING THE PERIOD OF NANJING HOMO ERECTUS

Using five group dating of the fossil by Uranium series age method shows that the age of Nanjing Homo Erectus is between 280－ 430 ka B. P. Combining with the analysis of fossil mammalian form Stegodon, Sus.Lydekkeri Zdansly, M.pachyosteus Young, P.grayi Zdansky and E.SanmeniensisTeilhard et Pive teau, which are located in the same stratum, the authors thinks that the Nanjing Homo Erectus may have lived in the late Mid Pleistocene (about 350 ka B.P.). Based upon the spores and pollen in the cave sediments of the area, we can find that most of spores and pollen are subtropical and warm temperature types. For instance, broad leaf trees which are fond of warm climate, including Cunning hamia, Jsuga and Pinus ,as well as Morus, Carpinus and Ptendium. Among the above spores and pollen, only Tsuga,Liquidambar, Betula,Ulmus and Salix are the remainders of Humid hot environment from the Tertiary period. Above evidences illustrate that the living environment of the Nanjing Homo Erectus not only was not cloder but also was not drier than the Peking Man’s. It could be said that dry climate and the ice age of the Mid Pleistocene didn’t undergo this area.As for the manner of the Homo Erectus’s making stone artifact and using fire, because now we have not found the evidence of the stone artifact and the ash, the futher excavation to the talus of the Huludong cave should be needed.

Geochemistry of Clayey Aquitard Pore Water as Archive of Paleo-Environment, Western Bohai Bay

The record of paleo-environment in clayey aquitard pore water is much more effective relative to aquifer groundwater owing to the low permeability of clayey aquitard. Oxygen-18（18O）, deuterium（D）, and chemical patterns were determined in pore water samples extracted from two 500 m depth boreholes, G1 and G2, in western Bohai Bay, China. Shallow pore water samples（depth〈102 m） are saline water, with the TDS（total dissolved solids） of 3.69–30.75 g/L, and deeper ones（depth=102–500 m） are fresh water, with the TDS〈1 g/L. Content of major ions（i.e., Cl-, Na＋, K＋, Mg2＋, SO2-4, Ca2＋） is high in marine sediment pore water samples and gradually decrease towards to terrestrial sediment pore water, together with the Cl/Br and Sr/Ba ratios changing significantly in different sedimentary facies along the study profile, indicating that pore water may be paleo-sedimentary water and not replaced by modern water. δ18O profile and positive correlation between δ18O and Cl- of shallow saline pore water indicated diffusion as the main transport mechanism, and distinguished four transgressive layers since Late Quaternary（i.e., Holocene marine unit, two Late Pleistocene marine units and Middle Pleistocene marine unit）, further supporting the finding that pore water retained the feature of paleo-sedimentary water. Climate was identified as the main influence on the isotopic signature of aquitard pore water and four climate periods were determined by δ18O profile.

Multiple enrichment mechanisms of organic matter in the Fengcheng Formation of Mahu Sag,Junggar Basin,NW China

Based on core and thin section data,the source rock samples from the Fengcheng Formation in the Mahu Sag of the Junggar Basin were analyzed in terms of zircon SIMS U-Pb geochronology,organic carbon isotopic composition,major and trace element contents,as well as petrology.Two zircon U-Pb ages of(306.0±5.2)Ma and(303.5±3.7)Ma were obtained from the first member of the Fengcheng Formation.Combined with carbon isotopic stratigraphy,it is inferred that the depositional age of the Fengcheng Formation is about 297-306 Ma,spanning the Carboniferous-Permian boundary and corresponding to the interglacial period between C4 and P1 glacial events.Multiple increases in Hg/TOC ratios and altered volcanic ash were found in the shale rocks of the Fengcheng Formation,indicating that multiple phases of volcanic activity occurred during its deposition.An interval with a high B/Ga ratio was found in the middle of the second member of the Fengcheng Formation,associated with the occurrence of evaporite minerals and reedmergnerite,indicating that the high salinity of the water mass was related to hydrothermal activity.Comprehensive analysis suggests that the warm and humid climate during the deposition of Fengcheng Formation is conducive to the growth of organic matter such as algae and bacteria in the lake,and accelerates the continental weathering,driving the input of nutrients.Volcanic activities supply a large amount of nutrients and stimulate primary productivity.The warm climate and high salinity are conducive to water stratification,leading to water anoxia that benefits organic matter preservation.The above factors interact and jointly control the enrichment of organic matter in the Fengcheng Formation of Mahu Sag.

准噶尔盆地玛湖凹陷风城组有机质多元富集机制

基于岩心和薄片资料,对准噶尔盆地玛湖凹陷风城组烃源岩开展了锆石SIMS U-Pb年代学、有机碳同位素组成、主/微量元素含量和岩矿分析等测试工作。在风城组一段获得2个锆石U-Pb年龄分别为(306.0±5.2)Ma和(303.5±3.7)Ma,结合碳同位素地层学数据,推断风城组的沉积年代约为距今297~306 Ma,跨越石炭纪—二叠纪界线,对应古气候划分的冰期事件C4和P1之间的间冰期。在风城组识别出多个Hg/TOC高值段,同时在页岩中普遍发现了蚀变的火山灰,表明在其沉积期发生多期火山活动。在风城组二段中部出现B/Ga高值段,与蒸发岩矿物及硅硼钠石的出现密切相关,表明水体高盐度与热液活动有关。综合分析表明,风城组沉积期温暖湿润的气候既有助于湖泊中藻类及细菌等生烃母质的发育又可加速大陆风化,促进营养元素输入;火山活动给湖泊提供了大量营养物质,提高了初级生产力;温暖的气候和较高的盐度有助于水体分层并导致缺氧,进而促进有机质的保存。以上多种因素相互作用,共同控制了玛湖凹陷风城组有机质的富集。

Quantitative relationship between surface sedimentary diatoms and water depth in North-Central Bohai Bay,China

To study the quantitative relationship between surface sedimentary diatoms and water depth,67 surface samples were collected for diatom analysis on eight profiles with water depth variation from the muddy intertidal zone to the shallow sea area in North-Central Bohai Bay,China.The results showed that the distribution of diatoms changed significantly in response to the change in water depth.Furthermore,the quantitative relationship between the distribution of dominant diatom species,their assemblages,and the water depth was established.The water depth optima for seven dominant species such as Cyclotella striata/stylorum,Paralia sulcata,and Coscinodiscus perforatus and the water depth indication range of seven diatom assemblages were obtained in the study area above the water depth(elevation)of-10 m.The quantitative relationship between surface sedimentary diatoms and water depth provides a proxy index for diatom-paleo-water depth reconstruction in the strata in Bohai Bay,China.

Factors controlling the formation and evolution of source rocks in the Shahezi Formation,Xujiaweizi fault depression,Songliao Basin

The types and quality of source rocks in the Shahezi Formation are the key factors affecting the distributions of various deep gas reservoirs in the Xujiaweizi fault depression in Songliao Basin.To clarify the quality differences and origins of different types of source rocks in the Shahezi Formation,this study reconstructed the sedimentary and water environment,determined the controlling effects of fault activity,sedimentary facies,and paleo-sedimentary environment on the quality of various source rocks,by making full use of seismic,logging,core,organic geochemical and element geochemical analysis.The results show that two types of source rocks developed in the Shahezi Formation,namely,mudstones and coals.The mudstones have a relatively high abundance of organic matter,which consists of type-Ⅱ kerogen and partial type-Ⅲ kerogen,and are concentrated in Sha-I Member.The coals have a high abundance of organic matter,which consist of type-Ⅲ kerogen,and are mainly distributed in Sha-Ⅱ Member.During the deposition of Sha-I Member,intense fault activity formed arrow,deep-water lacustrine basins with high salinity and strong reducibility on the downthrow sides of faults.During the deposition of Sha-II Member,fault activity progressively weakened,and the areas of lacustrine basins enlarged to their maximum values and became wide,shallow-water basins with low salinity and low reducibility.The development of source rocks was controlled by fault activity,sedimentary facies,and paleo-sedimentary environment.Fault activity formed accommodation space on the downthrown sides of faults for mudstone accumulation,thus determining mudstone thickness.The sedimentary environment controlled the organic matter input and determined the distribution of mudstones and coals.The paleo-sedimentary environment,which consisted of paleo-salinity,as well as paleo-water depth and redox conditions,affected the accumulation and preservation of organic matter and is the main controlling factor for the quality difference of various source rocks in the Shahezi Formation.

孟加拉湾深海记录中的等深流活动特征及其环境意义初探

实地观测和对沉积记录的研究表明 ,孟加拉湾存在强大的等深流活动 .通过采自孟加拉深海扇东部和中部的 3支活塞岩心的沉积学研究表明 ,那些氧化色彩强烈、钙质生物壳体溶蚀严重、不存在粒序层理的粉砂质薄层实际上是等深积作用的产物 .源自两极的等深流是全球温盐循环系统的关键组分 ,它们在过去 15 0ka的历史中曾经多次得到强化 ,不仅对研究区的环境变化产生重要影响 ,而且可能作为纽带 ,加强了低纬地区与极区在气候意义上的遥相关 .等深流的强化与冰川旋回之间似乎不存在密切关联 ,氧同位素第 3 ,4,5期内均可发现明显的强化记录 .关于强化的控制机制有待深入探讨 .

辽东湾LDD7孔晚更新世以来的沉积层序与古环境演化

对取自渤海辽东湾中部LDD7孔的300个沉积物样品进行了微体古生物分析,对196个样品进行了粒度分析,并选取8个层位的底栖有孔虫混合种进行了AMS^14C测年,利用线形插值方法建立了该孔的年代地层框架。研究结果表明：自晚更新以来辽东湾中部保持了相对连续的沉积序列,LDD7孔记录了该区约60.85cal.kaBP以来的沉积环境演化过程。根据垂向上微体化石组合和岩性的变化,将全长50.1m的沉积物柱状样划分为9个沉积单元,分别代表晚更新世冰期旋回中随着海平面的变化,辽东湾中部区域在不同阶段分别处于海相、陆相或海陆过渡相沉积环境;LDD7孔中共识别出两次主要的海侵过程,分别对应着渤海中部Bc-1孔所记录的献县海侵与黄骅海侵;此次测年结果进一步明确了辽东湾中部两次海侵持续的确切时间,分别是45.84～27.66cal.kaBP和10.64～0cal.kaBP。此外,几个相关岩心的年代框架计算结果表明,献县海侵过程中辽东湾南部沉积速率低于中部,而献县海侵之后辽东湾南部的沉降总量和平均沉积速率都明显高于中部。

内蒙东部及邻区晚石炭世—二叠纪构造古地理环境及演变

建立构造地层等时格架和不同构造地理单元地层的沉积相变序列,研究化石群落古生态学、生物建造发育和大地构造对环境的制约,将内蒙东部及邻区晚石炭世-二叠纪构造古地理环境及演变分为三个阶段。古亚洲洋阶段(晚石炭世—早二叠世)、兴-蒙海槽阶段(中二叠世)和兴-蒙张裂海槽阶段(晚二叠世)。区内该时期构造古地理环境始终受两条构造线控制,从南到北呈现三分性。索伦山-西拉沐伦断裂以南属华北板块,查干敖包-阿荣旗断裂以北属西伯利亚板块,两大板块之间先期为宽阔海洋,后期变窄成海槽,并夹有多个中间地块,如贺根山地块、索伦山地块、黄岗梁地块和佳木斯地块等。各地块在不同时期相互愈合并增生到板块边缘。林西地区晚二叠世晚期生物礁和海相化石的发现,马达屯期大规模火山喷发,及暴露在内蒙巴林右旗与吉林九台县的P\T角度不整合,均证明兴-蒙海槽在晚二叠世末期最终闭合,并区域褶皱隆起。

鄂尔多斯盆地镇北地区延长组长4+5段沉积期古环境条件及意义

以鄂尔多斯盆地镇北地区三叠系延长组长4+5段为研究对象,通过野外露头剖面、钻井岩芯共47块泥岩样品的微量元素、稀土元素地球化学分析,运用Sr/Ba、Th/U、Rb/K、硼(B)法,钴(Co)法、δU、V/(V+Ni)、V/Cr、Ni/Co、Ce/Ce^(+)、Eu/Eu^(+)、Sr/Cu、Mg/Ca等相关元素比值,定性、定量对长4+5段沉积期的古盐度、古温度、古水深、古气候及古氧化-还原条件进行了判识。结果表明,长4+5段沉积期古气温介于14.5~24.6℃之间,为半潮湿—半干燥的温带—亚热带气候;古盐度为陆相微咸水环境,介于0.50‰~3.78‰之间;古水温为8.9~11.9℃;古水深介于10~85 m之间;沉积物形成于弱还原—氧化条件。相对于延长组长7段沉积期来说,长4+5段尽管发育暗色泥岩,但由于环境条件的明显改变,气温升高致使水温增加,水体盐度增大,最终影响有机质发育和保存,不利于该段有效烃源岩的形成。

宝鸡关桃园遗址动物环境考古研究

目的揭示关桃园遗址各文化期的动物组成及其所反映的古代人类的食物结构、古环境演变。方法动物类型鉴定和居群统计,生态地理和动物地理分析。结果关桃园、北下和西王村时期的气温都比现在高,属于全新世以来气候的大暖期,其中,北下时期气温最高,其次为关桃园时期,再次为西王村时期;西周时期气温和现在非常接近。结论不同文化类型生物居群的变化主要是由于气候变化引起的,到西周时期东洋界动物已不存在,人们更多地依靠家畜来满足肉食的供给。

南海北部神狐海域晚末次冰期以来有孔虫特征及其对古海洋环境的指示

南海北部陆坡有大量高分辨率沉积记录,对研究全球变化响应及驱动机制有着举足轻重的作用。本研究选取南海北部神狐海域2007年水合物钻探区Site 6A站位柱状沉积物,开展有孔虫群落、稳定同位素及AMS14 C分析研究,试图了解该区域晚末次冰期以来古海洋和古气候演化历史。结果显示,Site 6A站位柱状沉积物中底栖有孔虫连续分布,优势属种突出,丰度、分异度波动明显。沉积物底界为MIS3期约50kaBP,全新世沉积速率最高,为13.37cm/ka,在MIS2期可能存在由水合物分解导致的地层缺失。有孔虫氧碳同位素特征恢复了冰期/间冰期气候旋回变化及冰盖体积变化,也指示该海域沉积环境氧化还原状况基本不变。通过对具有特殊生态意义的底栖有孔虫Uvigerina、Cibicidoides、Bulimina的相对丰度分析,结合似瓷质壳体百分含量及浮游有孔虫碳同位素,得出在末次冰期40kaBP东亚夏季风增强带来大量降雨,陆径流量增大导致古生产力增加。12~17ka的古生产力高值可能与增强的冬季风携带大量陆源碎屑沉积有关,并使得北大西洋低温、低氧、高营养盐的水团对该站位影响更大。

江苏金坛三星村地区7000年来古环境演变初探

对江苏金坛三星村新石器遗址JS98T0 82 0号探坑南壁剖面进行采样 ,并对样品作了氧化物、孢粉、微古 (有孔虫和介形虫 )、粘土矿物等古环境指标的测定分析 ,据此对该区新石器时代古环境演变状况进行了初步探讨 ,得出以下几点认识 :① 氧化物分析反映本区自全新世以来 ,气候有从干凉→干冷的变化趋势 .② P2 O5的含量在马家浜墓葬层和崧泽文化层可达生土层的 5～ 6倍 ,反映了人类活动愈益频繁 .③ 生土层样品中没有发现有孔虫、介形虫等微体古生物 ,通过对该层孢粉和粘土矿物分析可看出该层形成的气候环境是逐渐增暖的 ,而且温度渐增 .④ 该研究表明在三星村遗址剖面当中并未发现海相层 ,因此 ,全新世最大海侵到了指前镇一说尚待进一步研究考证 .

珊瑚的古环境信息研究进展

珊瑚由于有独特的生物学和生态学特性，成为研究热带海洋环境的信息载体。珊瑚骨骼“年轮”的发现和 Ｔ Ｉ Ｍ Ｓ铀系法高精度测年的应用奠定了珊瑚时间序列研究的基础，珊瑚骨骼的生长率、钙化率以及其中所含的元素、同位素成为示踪环境的重要手段。系统地评述了近年来这方面研究的进展情况，包括珊瑚骨骼的生长率、钙化率的环境意义；δ１８ Ｏ、 Ｓｒ／ Ｃａ、 Ｍ ｇ／ Ｃａ、 Ｕ／ Ｃａ 温度计的应用比较；珊瑚的荧光研究；以及 Ｔ Ｉ Ｍ Ｓ铀系法测年等。这些研究反映出珊瑚作为研究热带海洋环境的信息载体的重要性。

方解石沉积速率控制的物理化学机制及其古环境重建意义

本文总结了作者有关方解石沉积动力学研究的结果,发现方解石沉积速率受环境温度、CO2分压、水动力条件、水层厚度和溶液中钙浓度等多因素的控制。总的规律是温度愈高、CO2分压愈低、流速愈快、水层厚度愈大、溶液中钙浓度愈高,方解石沉积速率愈大。而且,方解石沉积速率随水中钙浓度的增加呈近似线性增加。文中对自然界类似环境条件下的速率系数和我国南北气候环境条件下的方解石沉积速率进行了总结和分析。文章最后对利用钙华和石笋的沉积速率进行古环境重建的复杂性进行了简要的讨论。

黄河源地区晚更新世湖泛事件及其意义

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