【摘要】 新近纪中晚期以来吕梁山西麓堆积了一套厚层红粘土。由于红粘土堆积早期有水流作用的参与,导致红粘土中夹杂有数层砾石层,这些砾石层记录了吕梁山山体隆升的信息。文章对山西省吕梁市中阳县吴家峁剖面红粘土进行了沉积学和磁性地层学研究,探讨吕梁山西麓红粘土的堆积过程以及吕梁山新近纪的抬升事件。磁性地层结果显示吴家峁剖面的古地磁年龄大约为7. 1～2. 6 Ma。所含砾石层的古地磁年龄分别为6. 2 Ma、5. 9 Ma、5. 8 Ma、5. 5 Ma、4. 9 Ma、4.0 Ma和3.7 Ma,其中6.2 Ma和4.9 Ma两层砾石层较厚,延伸较远,较稳定。结合吕梁山西麓中段卫家洼和复兴剖面的研究,得出红粘土中砾石层是吕梁山隆升剥蚀的产物,推断在大致8.1～3.7Ma之间吕梁山有较为明显的隆升。目前在吕梁山西麓中段的研究不支持这些砾石层是古黄河或者古湖泊沉积物。更多还原

【Abstract】 Thick red clay were deposited in the west piedmont of the Lüliang Mountains during the Neogene period.Previous studies have more focused on the eolian deposits and its paleoclimate information. Here, we described and interpret an 91. 1-m-thick red clay sequence which interbedded with 6 gravel layers in the lower part in west piedmont of the Luliang Mountains. The studied section was named Wujiamao and located in the Zhongyang County, Shanxi, with the coordinate and elevation of 37°15′43. 07″N,111°03′22.15″E and 1175 m a.s.l. The upper part of the red clay with deep reddish brown color, which are similar with other red clay deposits on the Chinese Loess Plateau. The lower part of red clay deposits were interbedded with several gravel layers which can be attribute to runoff transporting in the early period of red clay deposit. These gravel layers recorded the uplift of the Lüliang Mountains in Neogene. Based on magnetostratigraphy and sedimentology studies in the Wujiamao red clay section,the deposit process of the red clay and uplift events of the Lüliang Mountains were discussed. Rock magnetic results demonstrate that the magnetic carriers of the red clay deposits in Wujiamao section are mainly magnetite and hematite. The magnetostratigraphy results show that the paleomagnetic age of the red clay in Wujiamao section spans between 7. 1 Ma and 2. 6 Ma. The age of the gravel layers are 6. 2 Ma, 5. 9 Ma, 5. 8 Ma, 5. 5 Ma, 4. 9 Ma, 4. 0 Ma and 3. 7 Ma, respectively. The gravel layers with the age of 6. 2 Ma and 4. 9 Ma are thicker, more stable and farther extending than others. The age of the fossil layer between 89. 7 m to 89. 1 m is about 7. 0 Ma. The gravel layers in the red clay were the denudation and accumulation products of growth of the Ltiliang Mountains based on the studies of the gravel layers in Wujiamao and compared with other sections which located in the northern part of the west piedmont of the Lüliang Mountains. Our results indicate that the Lüliang Mountains had uplift rapidly from 8. 1 Ma to 3. 7 Ma, based on magnetostratigraphy and sedimentology studies of the red clay sections at Wujiamao, Fuxing and Weijiawa in the middle part of the west piedmont of the Lüliang Mountains. Our current studies don’t support the idea of the gravel layers were the deposits of the ancient Yellow River or a paleolake.更多还原