萨拉乌苏河流域米浪沟湾剖面主元素记录的末次间冰阶气候波动

Climate Fluctuations during Marine Isotope Stage 3 Suggested by Major Element Records in The Milanggouwan Stratigraphical Section in Salawusu River Valley,Inner Mongolia,China

位于鄂尔多斯高原萨拉乌苏河米浪沟湾剖面是重建毛乌素沙地晚更新世以来古气候的理想地点。其末次间冰阶（MIS3）层序含4种沉积相，划分为19个沉积单元，构成9.5个风成的砂丘砂与河流相、湖相和古土壤交替的沉积旋回。主元素分析结果显示，该剖面MIS3层序中河流相、湖相和古土壤的Al2O3、TOFE、CaO、MgO、K2O、Na2O、TiO2含量明显高于古风成砂，而SiO2则相反，构成与沉积旋回相应的9.5个元素波动旋回。这些元素旋回指示了该地末次间冰阶至少经历了10次温湿（w事件）和9次冷干（C事件）气候波动，且可划分为MIS3e（58.90-49.50kaBP）、MIS3d（49.50-40.70kaBP）、MIS3c（40.70-36.90kaBP）、MIS3b（36.90-27.00kaBP）和MIS3a（27.00-22.30kaBP）等5个亚段。其中，19次冷／暖波动可与格陵兰GRIP冰芯δ^18O冰段／间冰段大致对应，5个亚段与我国古里雅冰芯和V23-81冷性浮游有孔虫数代表的北大西洋地区气候也具有较好的可比性。

The Milanggouwan stratigraphical section in Salawusu river valley on the Ordos Plateau is an ideal site for reconstructing the paleoclimate of Mu Us Desert since the Late Pleistocene. Its MIS3 sequence contained four sedi- mentary types and were divided into nineteen units, and they constituted half nine sedimentary cycles for paleo-mobile dune sands alternating with fluvial-lacustrine facies and paleosols. The results of major elements analysis showed the contents of Al2O3, TOFE, CaO, MgO, K2O, Na2O and TiO2 in fluvial-lacustrine facies and paleosols were apparenfly higher than that in paleo-mobile dune sands; contrary is the contents of SiO2 for them; and thus these major el- ements constituted the similar half nine “element cycles”. These “element cycles” showed that the megainterstadial climates of the Salawusu valley at least went through ten wet-warm events（W） and nine cold-dry events（C） and could be divided into five substages： MIS3e （58.90-49.50 kaBP）, MIS3d （49.50-40.70 ka BP）, MIS3c （40.70-36.90 ka BP）, MIS3b （36.90-27.00 ka BP） and MIS3a （27.00-22.30 ka BP）. Thereinto, the nineteen cold warm climatic fluctuations were roughly corresponded with the stadial interstadial of GRIP ice core; as well, the five substages were rather consistent with the Guliya ice core in the climatic fluctuating features and phase as well as the North Atlantic climate reflected by the N. pachydema（s.） numbers of V23-81 core.