【摘要】 本文论述了晋东南榆社一带的各期黄土。这里是黄土自西而东分布的过渡地带，黄土的性状有共性也有各自的特性。晋东南的黄土分为早更新世老Ｒ红土、早至中更新世新Ｒ红土、中更新世上离石黄土、晚更新世马兰黄土和全新世黄土。古地磁年代学测试和剖面观察获得的各期黄土年龄为：老Ｒ红土形成于２．５－１．５ＭａＢ．Ｐ，新Ｒ红士形成于０．９—０．６ＭａＢ．Ｐ，离石黄土形成于０．６—０．１ＭａＢ．Ｐ。它们彼此之间都有不整合面相隔。自Ｒ红土开始出现，就意味着榆社古湖开始消失，气候环境向半干旱－半湿润方向发展。但比黄土高原略为湿润，夏季风的影响更强些。更多还原

【Abstract】 Southeastern Shanxi Province is situated in the eastern margin of the Loess Plateau, China. The famous Yushe basin is within this area, which is the transitional zone from the Loess Plateau to North China Plain. In this area the loess rests unconformably either on the Yushe Group or Triassic strata. The Yushe Group is a suit of fluvio-lacustrine deposits of Pliocene to the early stage of Early Pleistocene. The southeastern Shanxi loess can be divided into 5 Layers: (1) older red loam (Early Pleistocene), (2) younger red loam (the late stage of Early Pleistocene to the early stage of Mid-Pleistocene), (3) upper Lishi Loess (the middle-Late stage of Mid-Pleistocene), (4) Malan Loess (Late Pleistocene) and (5) Holocene loess;the total thickness amounts to about 50m. The Lishi Loess and the Malan Loess are much more widespread than the red loam.The red loam is a kind of specific sediments in southeastern Shanxi and is chiefly composed of silts. It is dark-red and brownish-red, quite homogeneous in lithology and commonly nonstratified. It is widespread in the Yushe basin and ad-jacent areas. It was first studied by P. Teilhard de Chardin and C.C. Young in 1933 and was called "R" loam for short.In this paper, the red loam is subdivided into two layers: (1) older red loam and (2) younger red loam. The older red loam is about 20m thick, contains 910 paleosol bands and has rich Fe-Mn nucleus but no calacareous concretions. Along the Zhuozhang River valley, the older red loam is underlaid with a gravel bed, in which mammalian fossils such as Equus sp. and Trogontherium sp. etc. were found. Besides, in Xiazhuang village a Myospalax tingi fossil was found on a section between the Yushe Group and the older red loam. The younger red loam is lighter in colour than the older red loam and about 10-15m thick, contains 2-4 paleosol beds, and is underlaid with well-developed calcareous concretions. The older red loam and younger red loam contain on an average 66.27% in silt, 10.71 % in fine sands and 23.02% in clay.The Lishi Loess rests on the red roam. It is 10-20m thick and contains 35 brownish-red paleosol beds and rich calcareous concretions. The concretions is the largest at the boundary between the Lishi Loess and the red loam.The Malan Loess is even more widespread in southeastern Shanxi and rests onthe Lishi Loess. It is less than 10m thick and contains small scattered calcareous coneretions.According to the loess section for paleomagnetic measurement shows that the older red loam accumulated at about 2.5-1.5Ma B. P., the younger red loam accumulated at about 0.9-0.6MaB. P. The Lishi Loess and the Malan Loess should be deposited during Brunhes. Lishe Loess at about 0.6-0.1Ma B.P. A correlation is that the older red loam corresponds to the lower part of the Wucheng Loess (Early Pleistocene)and the younger red loam corresponds to the lower part of the Lishi Loess. In fact,the Lishi Loess in southeastern Shanxi corresponds to the upper part of the Lishi Loess in the Loess Plateau.In the mineral composition of southeastern Shanxi loess, light minerals are mainly quartz. The quartz content is gradually decrease from the old red loam to the Malan Loess, while the calcite content is gradually increased. Ferriferous minerals are abundant in R Loam.Southeastern Shanxi is in the eastern part of China’s monsoonal region where the strong NW winds prevail in winter and spring. These winds bring much silt from the inland and lay it down in and around the Yushe basin. It is worthy to note that the loess in this region does not originate solely from dust brought by the NW wind from the interior of the Asian continent but partially from neighboring ancient lake sediments. This conclusion are supported by two pieces of evidence:(1) the loess here contains more fine sands than the loess in the Loess Plateau and (2) sand grains have both traces due to water currents and traces due to wind. In this region, generally, the content of near-source material is much more in the R loam than in the Lishi Loess and the Malan Loess.The nature of the R更多还原