Carbon Dioxide Content of Mesozoic and Cenozoic Atmospheres using Paleosols

新生代（800万~5600万年）的碳同位素组成 古土壤碳酸盐岩与中生代碳酸盐岩明显不同 古土壤碳酸盐， C值约为-10至-12 permil (118样品）和-6至-8 permil（21个样品）。 在 这个初步数据集只有一个数据点， 重叠。 考虑这种不同的可能原因 差异导致可能的浓度差异， 大气CO2 如果这是真的，它可能会导致一种方法， 估计大气中的P（CO2）至少在200 Ma前， 扩展了我们对古大气化学的认识 到目前为止， 直接测量的古二氧化碳测量值仅可追溯到0.16 Ma（Barnola等人，1987年）。 土壤碳酸盐的同位素组成记录了 土壤CO2的同位素组成，这是直接相关的 大气中的二氧化碳浓度。 对于现代土壤， 大气对土壤CO2总量的贡献几乎可以忽略不计。 然而，较高的大气P（CO2）水平使 土壤CO2同位素组成的差异， 碳酸盐与土壤CO2平衡形成。 本研究 研究了古土壤碳酸盐的同位素组成， 中生代和新生代，目的是确定P（CO2） 古老的气氛 初步结果表明，这是一个 可行的方法，中生代的二氧化碳水平显着 比今天高，大约1500到2500 ppmV。

The carbon isotopic composition of Cenozoic (8 to 56 Myr) paleosol carbonates is significantly different than Mesozoic paleosol carbonates, having C values of about - 10 to - 12 permil (118 samples) and -6 to -8 permil (21 samples), respectively. In this preliminary data set there is only one data point that overlaps. Consideration of the possible causes for this distinct differences leads to a possible difference in the concentration of atmospheric CO2 . If this is true it could lead to a method to estimate P(CO2) in the atmosphere to at least 200 Ma ago, greatly extending our knowledge of paleoatmospheric chemistry. So far, direct measurements of paleo-CO2 measurements go back only 0.16 Ma (Barnola, et al., 1987). The isotopic composition of soil carbonate records the isotopic composition of soil CO2 which is directly related to the concentration of CO2 in the atmosphere. For modern soils the atmospheric contribution to total soil CO2 is almost negligible. However, higher atmospheric P(CO2) levels make a significant difference in the isotopic composition of soil CO2 and hence, soil carbonate formed in equilibrium with soil CO2. In this study we examine the isotopic composition of paleosol carbonates from the Mesozoic and Cenozoic with the aim of determining P(CO2) of the ancient atmosphere. Preliminary results suggest that this is a viable approach and that Mesozoic CO2 levels were significantly higher than today, on the order of 1500 to 2500 ppmV.