The Geologic Time Scale 2012
The Geologic Time Scale 2012
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发表时间：
2012
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通讯作者：
M. Saltzman;E. Thomas
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作者：
M. Saltzman;E. Thomas
通过对海洋碳酸盐岩（dCcarb）的地层学研究，记录了世界海洋中总溶解无机碳（DIC）的C/C值随时间的变化。这种变化已被用来确定沉积物的年代和相关性。碳同位素的地层记录是复杂的，因为从C中分离C的主要过程是光合作用，而有机质中的重同位素（C）是贫化的。碳同位素记录（在这里考虑的地质时间尺度上）在很大程度上由有机碳和碳酸盐之间碳分配的变化来定义，因此与生物圈和全球碳循环直接相关。本章总结了从多个文献来源汇编的地质时期的dCcarb变化。用于曲线构建的材料在作者之间和地质时期之间存在差异，并且应该仔细考虑特定生物分泌的骨架碳酸盐或散装碳酸盐是否用于评估或比较碳同位素地层记录。中侏罗世至新生代的曲线主要来自远洋碳酸盐，相对于记录早期的曲线（元古宙从3到108年，元古宙和太古代从15到1015年），dCcarb变化幅度较低（从1到104年）。中侏罗世和更老的曲线主要基于台地碳酸盐岩的数据，其显示出更大的变化性和更大的空间非均质性。与较年轻的远洋记录相比，来自较老的台地碳酸盐岩的碳同位素曲线的不同特征可能反映了原生和/或成岩过程、古环境的差异、钙化生物的差异或全球碳循环随地质时间和生物进化的内在变化（例如，水库规模的变化）。
Variations in the C/C value of total dissolved inorganic carbon (DIC) in the world’s oceans through time have been documented through stratigraphic study of marine carbonate rocks (dCcarb). This variation has been used to date and correlate sediments. The stratigraphic record of carbon isotopes is complex because the main process fractionating C from C is photosynthesis, with organic matter depleted in the heavy isotope (C). The carbon isotope record (on the geological time scales considered here) is to a large extent defined by changes in the partitioning of carbon between organic carbon and carbonate, and therefore linked directly to the biosphere and the global carbon cycle. This chapter summarizes dCcarb variations through geologic time compiled from multiple literature sources. Materials analyzed for curve-construction differ between authors and between geological time periods, and one should carefully consider whether skeletal carbonate secreted by specific organisms or bulk carbonate has been used in evaluating or comparing carbon isotope stratigraphic records. Mid-Jurassic through Cenozoic curves have been mainly derived from pelagic carbonates, and exhibit low amplitude dCcarb variability (from 1 toþ4&) relative to curves for the earlier part of the record (from 3 to þ8 & for the Phanerozoic, from 15 to þ15& for the Proterozoic and Archean). The Mid-Jurassic and older curves are dominantly based on data from platform carbonates, which show greater variability and more spatial heterogeneity. The different character of carbon isotope curves derived from older platform carbonates as compared to younger pelagic records may reflect primary and/or diagenetic processes, difference in paleoenvironments, difference in calcifying organisms, or inherent changes in the global carbon cycle with geologic time and biotic evolution (e.g., changes in reservoir size).