Organic geochemical proxies of paleoceanographic, paleolimnologic, and paleoclimatic processes
Organic geochemical proxies of paleoceanographic, paleolimnologic, and paleoclimatic processes
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DOI：
10.1016/s0146-6380(97)00049-1
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发表时间：
1997-10-01
影响因子：
3
通讯作者：
Meyers, PA
中科院分区：
文献类型：
--
作者：
Meyers, PA
有机质在海洋和淡水沉积物中只占很小的比例，但它对沉积记录的重要贡献可以用来重建海洋和大陆的古环境。沉积物中的有机质是过去生物群的残留物。因此，沉积物中有机物的数量和类型反映了过去不同时期影响生态系统的环境条件。一般来源的有机质推断从散装性能，如元素组成，碳和氮稳定同位素比值，岩石评价热解数据，和有机岩相。通过生物标志物分子组成的分析，有机质起源的细节得以完善。源的变化是海平面、海洋表面流和大陆气候波动的替代物。藻类的古生产力速率由有机碳质量积累速率和碳、氮稳定同位素组成指示。这些参数记录了过去营养物质的可用性，因此，是海洋表面混合和陆地径流到湖泊的数量的代理。海洋表面古温度是由海洋藻类产生的脂类生物标志物中碳-碳双键的数量记录的。较大比例的双键代表了较冷的表面沃茨，这些海水伴随着全球冰川期和上升流增强的间隔。植物有机物的δ（13）C和δ D值分别记录了过去大气中二氧化碳的浓度和大气水分输送的变化。成岩作用导致沉积环境中有机质的浓度和组成与原始生物合成物质不同，可能会使有机地球化学古环境记录产生偏差。必须始终考虑和评估这一潜在错误信息来源的严重程度。过去条件的多个有机地球化学指标的比较有助于补偿成岩蚀变的影响，从而提高古环境变化的解释。(C)1997 Elsevier Science Ltd.保留所有权利。
Organic matter constitutes a minor fraction of marine and freshwater sediments, yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments. The organic matter content of sediments is the residue of past biota. The amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times. General sources of the organic matter are inferred from bulk properties such as elemental compositions, carbon and nitrogen stable isotope ratios, Rock-Eval pyrolysis data, and organic petrography. Details of organic matter origins are refined by analyses of biomarker molecular compositions. Source changes are proxies for fluctuations in sea-level, oceanic surface currents, and continental climates. Algal paleoproductivity rates are indicated by organic-carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions. These parameters record past availability of nutrients and, therefore, are proxies of surface mixing in the oceans and amount of land runoff to lakes. Sea-surface paleotemperatures are recorded by the number of carbon-carbon double bonds in lipid biomarkers produced by marine algae. Larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling. The delta(13)C and delta D values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture, respectively. Diagenesis, which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials, can bias organic geochemical paleoenvironmental records. The magnitude of this potential source of misinformation must always be considered and evaluated. Comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change. (C) 1997 Elsevier Science Ltd. All rights reserved.