Depositional Ralation between the Loess, Red Clay and Sedimtation of the Lakebasin in the Loess Plateau

Key words: 
• magnetostratigraphy /
• loess /
• red clay /
• Sanmen group /
• Youhe group

Abstract: This paper discusses the relation of sedimentation between the loess, red clay and deposits of the Sanmen lake in the Chinese loess highland by studies of magnetostratigraph, biostratigraph, sedimentology and environmental analysis. Main results are 1)the Early Pleistocene loess overlies continuously on the top of the Neogene red clay in some sections. 2)the Brunhes normal polarity zone and Matsuyama reversal polarity zone were recorded in the loess section and the deposit of the Sanmen lake. The B/M boundary is located in the L ₈ loess layer. The J subzone is located between the S ₁₀S ₁₃loess beds. The O subzone is located in S ₂₂ S ₂₃ loess beds, or in the deposit of the Sanmen lake. The M/Ga boundary corresponds to the loess/red clay boundary, and also basically to the Sanmen group/Youhe group boundary. 3)the red clay includes not only the sediment of Miocene Baode epoch, but also the deposits of Pliocene and Miocene. The Pliocene Jingle group recorded the Gauss normal polarity zone and the Gilbert reversel polarity zone, but the Miocene Lantian group recorded Epoch 5. 4)the deposit of the Sanmen lake includes the Early Pleistocene Sanmen group (1.20-2.45Ma, Matsuyama reversel polarity zone) and the Late Pliocene Youhe group (2.50-3.50Ma, Gauss mormal polarity zone). The Sanmen group and Wuyu loess are the contemporaneous different facies deposits, the Matsuyama reversal polarity zone was recorded in them. The Youhe group and the upper red clay(upper of Jingle) are the contemporaneous different facies deposits as well, which recorded the Gauss normal polarity zone.