Late Pleistocene sedimentary sequences and paleoclimate changes in Xunhua basin in the upper reach of Yellow River in China

The third terrace of the Yellow River was well developed in Xunhua basin in the north-east margin of the Tibetan Plateau. The terrace was formed at ca 75 ka as dated by the optically stimulated luminescence (OSL) method. On the basis of grain size, magnetic susceptibility and palynological data, six episodes of the climatic change were identified in Xunhua basin; they include very warm and humid period during 120–114 ka, cool and dry period during 114–105 ka, warm and humid period during 105–98 ka, gradually cooling period during 98–85 ka, warm and humid period during 85–75 ka, very cold and dry period during 75–63 ka. The six stages of climatic change recorded in Xunhua basin correspond to the marine oxygen isotope stages (MIS) of 5e, 5d, 5c, 5b, 5a and 4, respectively.