鄂尔多斯东南地区150kaB.P.以来CaCO₃旋回与气候变迁的探讨

【作者】 罗开利；

【导师】 李保生； 丘世钧；

【作者基本信息】 华南师范大学 ， 自然地理学， 2002， 硕士

【摘要】 以萨拉乌苏河流域米浪沟湾剖面为代表的鄂尔多斯东南洼地地区150ka B.P.以来的地层中存在38个由风砂沉积与河湖相和／或古土壤构成的地层旋回。地层中的CaCO₃含量分布呈现出与沉积物粗细韵律相同步的变化，从风成砂到其上覆的河湖相和／或古土壤，CaCO₃含量亦相应表现出38个由低到高的旋回分布。CaCO₃含量在不同沉积相中的这种不同于深海和黄土地区的独特分布特征，是在低洼地貌背景下，古气候干湿冷暖及风力大小更叠的结果。风砂相形成于干寒多风的气候条件下，其时物理作用占主导，其CaCO₃含量基本是物源本身原有成分；河湖相和古土壤中CaCO₃含量的增加，可能反映出当时气候较为温暖湿润，较多的降水使CaCO₃在研究区周围的高地上淋失而在洼地区域聚集，冬季风减弱导致粉砂物质在区内沉降量增加，由于粉砂具备有利于与CaCO₃相结合的特点，故它的增加从另一方面导致了CaCO₃含量的增加。 米浪沟湾剖面150ka B.P.以来的CaCO₃含量的多波动分布情况可与极地GRIP冰芯和深海沉积中氧同位素阶段进行对比，对应δ¹⁸O1、δ¹⁸O3和δ¹⁸O5的层段，其CaCO₃含量平均值和分布范围，特别是平均值均明显地表现为高含量，对应δ¹⁸O2、δ¹⁸O4和δ¹⁸O6层段的CaCO₃含量则较低。研究区末次冰期CaCO₃含量的波动还能够体现出10ka～70ka存在的6个Heinrich事件。这些耦合关系的确立，说明研究区150kaB.P.以来CaCO₃含量变化所揭示的区域气候环境变迁其实是全球环境演变在本区的响应。更多还原

【Abstract】 The formation in Southeast Depression of Ordos Plateau, which takes Milanggouwan section in the Salawusu River valley as represent, exists 38 stratigraphical cycles of palaeo-aeolian sands, fluvio-lacustrine facies or/and palaeosols since ISOka B.P. The content of CaCOa in the section takes on remarkably correlative relationship, which appears 38 low-high change cycles with the sedimentary cycles of palaeo-aeolian sands to its overlying fluvio-lacustrine facies or/and palaeosols. The special character of calcium carbonate distribution, which is different from that of blue water and loess area, is the result of cold-dry and warm-humid palaeo-climate change, under its special low-lying geomorphological background. The aeolian sands deposit under the cold-dry and windy climate, when the physics action accounts for dominant. The content of CaCOa basically is the component of origin substance; the higher numerical value distribution in the fluvio-lacustrine facies and palaeosols are probably related to warm and humid climate background. More precipitation makes CaCOs drench on the highland, whereas gather in the depression. The winter monsoon weaken, makes silty sand substance subside in the area in the gross, as the silty sand is easy to combine with CaCOs, the increase of them cause the addition of CaCOs content.The multi-fluctuation of CaCOj content in Milanggouwan section since ISOka B.P. can contrast with oxygen isotope phases of blue water and polar region GRIP ice core. It shows the formation corresponds to phases 18O1, 6 I8O 3 and 8 18O5, the mean and extent of CaCO3, especially the mean value manifests higher content, whereas formation of phases 1802, 6 18O4 and 5 1806 manifests lower value. The fluctuation of CaCOa content also embodies six Heinrich Incidents since 10ka ~70ka B.P. These well coupling relationship indicate that the climate change in the Salawusu River valley since 150ka B.P., which denoted by the CaCOs content variety is the response of past global environmental evolvement.更多还原