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甘肃灵台县任家坡黄土－红粘土剖面的磁性地层学研究表明；中国北方连续的风成堆积可下推到705MdB．P。第三纪红粘土的粒度组成从上到下变化很小，与黄土－古土壤序列的粒度大幅度变化形成强烈的反差，意味着晚第三纪时期的气候总体上要比第四纪时期稳定。在705～2．6MaB．P．的红粘土沉积中，可分出的110～115个土壤B层与钙质结核层的组合，初步表明在这个时期有约110～115次气候旋回。
The magnetic stratigraphic study of the loess-red clay section of Renjiapo, Lingtai County, Gansu Province shows that the continuous wind accumulation in northern China can be pushed down to 705MdB. P. The composition of the Tertiary red clay changed little from top to bottom and formed a strong contrast with the sharp change in the grain size of the loess-paleosol sequence, suggesting that the climate in the late Tertiary period was generally stabler than the Quaternary period . At 705 ~ 2.6MaB. P. Of the red clay sediments, the combination of 110-115 soil B layers with calcareous nodules, which can be separated, initially showed that there were about 110-115 climate cycles during this period.