西藏定结地区全新世风沙地貌格局与变化

The geomorphic patterns of aeolian geomorphology can reflect the degree of desertification directly. The syudy of geomorphic patterns of aeolian geomorphology in the Holocene has an important reference value for understanding the desertification trend in the future. Aeolian geomorphology is widely distributed in PumQu valley, although in the Tibet Plateau, but the wind regime of aeolian activity comes from the southern slope of the Himalayas. Its formation mechanism is different from which in the northern part of China and other regions in the Tibet Plateau. Aeolian deposition in PumQu valley are concentrated in the Dinggye area. This project intends to select the Dinggye as the study area, carry out the study of the geomorphic patterns and variability of aeolian geomorphology in the Holocene. Firstly, Combined the interpretation of DEM and remote sensing images with field verification, we analyze the geomorphic patterns of modern aeolian geomorphology in Dinggye area. Secondly, Identified the palaeo-aeolian strata according to the characteristics of the sedimentary facies, and on the basis of the unity of the sources of the aeolian deposition, we choose several typical palaeo-aeolian profiles and establish their chronological sequences with OSL dates. The chronological sequences of other palaeo-aeolian profiles in the study area were established according to cross-section stratigraphic contrasts. Based on the geomorphic patterns of modern aeolian geomorphology, analyzing the characteristics between modern and paleo-aeolian deposition, we reconstruct the geomorphic patterns and variability of aeolian geomorphology in the Holocene, and investigate the regional evolution mechanism of aeolian geomorphology. Overall, this research is of significance for the rich of the theory of aeolian geomorphology of China. Meanwhile, provide a scientific basis for the prevention of land desertification in the Dinggye.

风沙地貌格局最能直接的反映沙漠化程度，全新世风沙地貌格局研究对预测未来的沙漠化趋势最具有参考价值。朋曲河谷风沙地貌分布广泛，其风沙地貌形成动力来自喜马拉雅山南坡，具有与我国其他地区风沙地貌不同的成因机制。项目拟以朋曲河谷风沙沉积集中分布的定结地区为研究区，开展全新世风沙地貌格局与变化研究。首先，通过DEM和遥感影像解译，结合野外验证，获取现代风沙地貌格局；其次，根据沉积相特征识别古风沙沉积地层，在确定物源统一性的基础上，选择具有代表性的古风沙地层剖面，开展OSL测年，结合剖面间地层对比，建立古风沙年代序列。最后，以现代风沙地貌格局为参照，对比分析全新世与现代风沙沉积特征，恢复全新世风沙地貌格局，重建全新世风沙地貌格局的变化过程，探索研究区风沙地貌演化机制。项目的开展不仅可以丰富我国风沙地貌学理论，还可为定结地区土地沙漠化防治提供科学依据。

青藏高原北部以及藏南河谷地带广泛分布着大量的晚更新世以来的风沙沉积。这些风沙沉积的形成与高原冰川和荒漠化作用进程密切相关，是揭示青藏高原地质历史时期冰川演化和粉尘活动历史的理想载体。但是由于青藏高原特殊的气候条件及地貌形态，目前对于青藏高原地质历史时期风沙地貌格局及其演化过程仍缺乏足够的认识。本项目通过对青藏高原南部定结地区现代风沙地貌格局、风沙沉积特征及全新世以来古风沙沉积的年代学研究，恢复研究区全新世风沙地貌格局，重建全新世风沙地貌格局的变化过程。研究结果显示：（1）定结地区现代风沙地貌格局总体沿朋曲河、协林藏布、叶如藏布、吉隆藏布以及曲强藏布等河流河谷呈条带状分布，沿错母折林、强左错、共左错以及登么错等湖泊零星分布；（2）定结地区风沙沉积物粒度和元素地球化学特征显示，风沙沉积的物质来源主要为研究区内的河漫滩和湖滩沉积，现代风沙和古风沙沉积具有同源性；（3）相较现代风沙地貌分布格局，定结地区全新世风沙地貌有3个扩张期、3个收缩期和1个相当期。扩张期包括12.0～9.8 ka B.P.、8.6～6.8 ka B.P.和2.1 ka B.P.以来3个时期；收缩期包括12.83～12.0 ka B.P.、9.8～8.6 ka B.P.和6.8～4.8 ka B.P. 3个时期；4.8～2.1 ka B.P.期间研究区风沙地貌格局和现代风沙地貌格局相当。研究结果对揭示青藏高原全新世风沙活动历史具有重要的理论意义，对定结地区土地荒漠沙化防治具有重要的实际意义。