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沉积于兰州黄河北岸山足面之上的烟洞沟风成黄土,剖面厚约120m,据磁性地层学研究,该剖面包括B/M界线、后贾拉米洛、贾拉米洛、考伯、奥尔都维、吉尔萨等事件,结合沉积速率推算,剖面底界的年代约为1.7MaB.P.
According to the study of magnetic stratigraphy, the profile includes the B / M boundary, the post-Jalamito, Jalamilo, and Coperbourg , Orduville, Jilla and other events, combined with the deposition rate calculation, the basal boundary of the age of about 1.7MaB.P.