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沉积物的镁铝含量比——m 值(m=100×MgO/Al_2O_3)与沉积水介质的盐度、pH 水温关系密切。当水温处在冰点以下时,沉积物的m 值随水温降低而增大。当水温处在冰点以上时,水介质的盐度、pH 和水温的增加,都有利于m 值增大。由于气候条件能直接或间接地影响沉积水介质的特征,因此,沉积物的m 值对古气候的变化具有一定的判别功能。通过对中国元古宙以来沉积物m 值的分析,发现古气候的热冷变化有1200Ma 的周期,其中还有次一级的热冷气候波动。第四纪的气候是处在热气候期后期的一个冷的气候波动阶段。
The ratio of Mg to Al in the sediments is close to the value of - m (m = 100 × MgO / Al_2O_3) and the salinity and pH of the sediment medium. When the water temperature is below the freezing point, the value of m increases with decreasing water temperature. When the water temperature is above the freezing point, the increase of salinity, pH and water temperature of the aqueous medium will help increase the value of m. Because of the climatic conditions that can directly or indirectly affect the characteristics of sedimentary aquifer media, the m value of the sediment has a certain discriminating function on paleoclimate changes. Based on the analysis of the m value of sediments since the Paleozoic in China, it is found that there are 1200Ma periods in the paleo-climate change, including the sub-level hot and cold climate fluctuations. Quaternary climate is in a cold climatic phase of the latter part of the hot climate.