论文部分内容阅读
位于黄土高原东南缘的三门峡黄土地层 ,以陕县张汴乡曹村剖面为其典型代表。厚度 1 5 3m的曹村剖面由上部厚 1 45 m的黄土地层和下伏红粘土沉积组成 ,黄土地层为 L1 — L33的连续风尘沉积。磁性地层研究显示 :B/ M界线位于 L7下部 ,J事件位于 S1 1 —S1 2 ,O事件位于 L2 3—L2 6,M/ G界线位于黄土与红粘土界线之上 2 0 cm处。古季风代用指标的磁化率、碳酸盐及 >30μm的粒度组分均显示了约 2 .6 Ma以来季风变迁的阶段性特点。曹村黄土剖面具有持续时间在 4万年以上的黄土沉积所指示的 1 3次气候寒冷事件 ,所反映的古气候变化具有周期性。应用粒度年龄模式建立曹村剖面高分辨率的年代地层序列 ,通过曹村剖面近 30万年来的磁化率及粒度变化与深海氧同位素对比 ,曹村黄土剖面与深海沉积有良好的可比性。
The Sanmenxia loess formation, located on the southeastern margin of the Loess Plateau, is a typical representative of the Caocun section of Zhangjian Township in Shan County. The Caocun section with a thickness of 155 m consists of a loess layer with a thickness of 1 45 m and an underlying red clay sediment. The loess layer is a continuous deposition of dust from L1 to L33. Magnetic stratum studies show that the B / M boundary is located in the lower part of L7, the J event is located in S1 1 -S1 2, the O event is located in L2 3-L2 6, and the M / G boundary is located 20 cm above the boundary between loess and red clay. The magnetic susceptibility, carbonates and the grain size of> 30μm of the paleotymas indicate that the monsoon changes from the stage of about 2.6 Ma. The 13 cold climatic events indicated by loess sediments with a duration of more than 40,000 years in the Loess Section of Caocun reflect the cyclical changes in paleoclimate. By using the grain-age model, a high-resolution chronostratigraphic sequence is established. By comparing the magnetic susceptibility and grain size changes of the Caocun section over the past 300,000 years with the deep-sea oxygen isotopes, the Caocun loess section has good comparability with the deep-sea sediments.