Molecular Evidence for Primary Producers and Paleo-environmental Conditions in Mesoproterozoic in the Xuanlong Depression in North China

The molecular organic compounds have been identified by gas chromatography (GC) and GC-mass spectrometry (GC-MS) from Mesoproterozoic rocks in the Xuanlong depression in North China. The main saturated compounds are n-alkanes, monomethylalkanes, n-alkylcyclohexanes, acyclic isoprenoids, and hopanes. The dominant lower-molecular-weight n-alkanes are indicative of the main contribution of microorganisms, in particular, the chemosynthetic bacteria. The presence of abundant monomethylalkanes (mid- and end-branched) and the long chained (>C₂₀) acyclic isoprenoids indicates the existence of abundant bacteria and/or archaea in ancient oceans. The low abundance of pristane and phytane is suggestive of the relatively low abundance of photosynthetic autotrophs in comparison with chemosynthetic bacteria in the Mesoproterozoic oceans in North China. The sedimentary environmental condition is suboxic/anoxic, as indicated by the low value of the Pr/Ph ratio as well as the presence of abundant sulfur-bearing organic compounds, consistent with the other geochemical data in North China and elsewhere in the world. Both the composition of the primary producers and the sedimentary environmental conditions are favorable for the formation of hydrocarbon source rocks.     

湖北梁子湖近代沉积记录对人类活动的响应

为了研究人类活动背景下的湖泊生态响应过程和机制, 分析人类活动对湖泊富营养化的贡献, 在210Pb计年和历史事件记载基础上, 通过梁子湖沉积物水生生物遗存和色素分析重建了梁子湖地区过去100多年来湖泊生态系统演化过程.沉积物色素和水生生物遗存组合带的变化表明梁子湖营养演化具有5个阶段: 过去100多年梁子湖地区经历了生态环境良好的贫营养化期(1885-1902A.D.)、轻度富营养化期(1902-1964A.D.)、中度富营养化期(1964-1988A.D.)、富营养化期(1988-1998A.D.)、中度富营养化期(1998-2003A.D.).水生生物遗存随着湖泊富营养化的发生而呈现一定的分布特征, 对富营养化敏感的奥古茨藻、荇菜、角果藻、纹沼螺、表壳虫等逐步减少.通过湖泊演化阶段与区域人类活动重大阶段的联合对比研究发现随着人类活动的增强及对湖泊生态的持续干扰, 湖泊生态演化呈现明显的阶段性, 湖泊富营养化的发生与流域强烈的人类活动如围垦与农业活动带来的营养物质输入有着直接联系, 湖泊生态环境演化对重大人类活动事件具有响应性.本研究对于认识湖泊生态环境演化与人类活动的关系、整治湖泊环境具有重要的指导意义.      

The Pleistocene vermicular red earth in South China signaling the global climatic change: The molecular fossil record

The widespread (with a distribution area of 2.2?06 km2) Pleistocene red earth is believed to be one of the most detailed records of the environmental and climatic changes in South China. However, the previous research mainly covers the rough dating, pedo…     

示踪全球环境变化的微生物代用指标

文章详细总结了示踪全球环境变化的一系列微生物替代指标。重建古温度的定量指标包括藻类长链烯酮的U、古菌甘油二烷基甘油四醚化合物(GDGTs)的TEX_(86)指标、细菌GDGTs的甲基化指数(MBT)与环化指数(CBT)的组合。古温度的定性指标有脂类单体的氢同位素组成、不饱和脂肪酸的相对含量、有孔虫和硅藻的组合及其生物体的同位素组成和微量元素比值。重建古水文的指标包括有壳变形虫组合、细菌GDGTs的环化指数CBT、细菌和古菌GDGTs的陆源输入指数BIT、古菌和细菌GDGTs的相对丰度R、直链脂肪族化合物的碳优势指数CPI、好氧与厌氧微生物的丰度。古大气CO_2分压的估算可采用藻类长链烯酮的碳同位素组成、有孔虫的硼同位素组成。认为这些微生物指标在古环境重建中潜力巨大,并对一些重要微生物指标的应用原理和限定条件进行了分析。有些指标因受多种环境因子和成岩作用的影响,在应用中需特别的注意,不能无限夸大其应用领域。     

古今结合论碳汇、见微知著识海洋

海洋是地球上最大的活跃碳库,发挥着全球气候变化"缓冲器"的作用,研究海洋碳循环过程与储碳机制是当前的国际热点。然而,地球系统的复杂性注定了这个重大命题必须通过学科交叉、古今结合才能取得较全面的认识和新的突破。     

Paleofire Indicated by Polycyclic Aromatic Hydrocarbons in Soil of Jinluojia Archaeological Site,Hubei,China

Combustion-derived and land-plant-derived polycyclic aromatic hydrocarbons (PAHs) have been investigated by using the GC-MS analysis in an ancient soil profile from Jinluojia (金罗家) archaeological site at Macheng (麻城),Hubei (湖北) Province,Central China.Retene,cadalene and simonellite were proposed to be derived from contemporary land plants.The pyrolytic PAHs identified include fluoranthene,pyrene,benzofluoranthenes,benzo[e]pyrene and benzo[a]pyrene.The distribution of these pyrolytic PAHs varies with depth,d...     

浙江长兴中-晚更新世红土植硅体与分子化石记录及其环境意义

在野外地貌、岩性和相关沉积环境调查分析基础上,对浙江长兴中—晚更新世红土进行了分析,发现其中含有较丰富的植硅体形态类型,主要来自草本、阔叶和裸子植物等,植硅体含量分布具有一定的组合特征。在温暖指数和草本覆盖指数计算基础上,获得了中—晚更新世以来的3个古植被、古气候演化组合带;运用植硅体和分子化石的相关指标(C21-/C22 、C23/C30)揭示了洪积扇红土沉积时期的植被与气候信息,即间冰期气候暖湿,风化作用强,降水较多,高等草本植物繁盛;而冰期时气候干凉,风化作用弱,降水减少和地下水位降低等则有利于洪积扇体上木本类植被发育。