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温度变化研究是理解地球气候系统变化的关键环节之一.通过对海水温度变化的了解,可以系统地了解全球气候演化规律及其驱动机制.由于腕足化石具有保存完好以及分布年限长等优势,提取腕足化石中氧同位素信息进行古生代海水温度变化研究,已成为常用手段,但利用其Mg/Ca比值进行古温度变化的探讨却很少报道.通过对四川龙门山泥盆纪腕足化石中氧同位素以及Fe、Mn、Sr、Mg、Ca等微量元素的提取,结合微体结构观察、阴极发光等实验,在判定腕足化石保存良好的前提下,发现根据腕足化石中Mg/Ca(mmol/mol,下同)比值计算的温度相比氧同位素推算的温度,同生物学、古地理学证据显示的温度更为接近.此结果可能是由于利用氧同位素计算温度时古海水氧同位素未知及其不稳定性造成的.尽管腕足化石Mg/Ca比值温度计同样受海水的盐度以及pH等因素的影响,但计算结果显示,其反演的古温度比较接近真实的温度变化.
The study of temperature change is one of the key points to understand the changes of the Earth’s climate system.According to the change of seawater temperature, we can systematically understand the global climate evolution and its driving mechanism.Because the brachiopod fossils have the advantages of well-preserved and long-lived distribution, It has become a common method to study Paleozoic seawater temperature changes based on the oxygen isotope information of the brachiopod fossils, but few studies have been done to investigate the palaeoclimate changes based on their Mg / Ca ratios.On the basis of the Oxygen Isotopes Fe, Mn, Sr, Mg, Ca and other trace elements, combined with the microstructure observation, cathodoluminescence and other experiments, in determining the good preservation of the brachiopod fossil found under the foot of the fossil Mg / Ca Same) than the temperature estimated by oxygen isotope, which is closer to the temperature indicated by the paleogeographic evidence, probably due to the unknown and unstable water oxygen isotopes Caused by. Although the foothill fossil Mg / Ca ratio thermometer also affected by seawater salinity and pH and other factors, but the calculation results Show, the ancient temperature of its inversion is relatively close to the real temperature changes.