摘要
本文提出海岸风沙沉积和海岸风尘沉积是晚更新世期间，由东北季风风系控制的风沙流活动所成。每一期风沙流活动的时限不恒定，其盛行风向前缘随着风力衰减而产生风尘沉积，形成海岸风沙—海岸风尘沉积匹配带。中国海岸带自北而南可划分出四个海岸风沙—海岸风尘沉积匹配区。海岸风沙－海岸风尘沉积均具有多发、高频变化特征，与其中交互更叠的土壤层、冲－洪积层、侵蚀间断面等一起，可成为晚更新世期间气候－环境判别的标志。
Three types of Late Pleistocene coastal eolian sand sediments in the areas of Liaodong Peninsula, Qinghuang Island, shandong Peninsula, Putuo Island,Pingtan island, Dahao Peninsula, the coastal area of Hailufeng, Leizhou Peninsu la, the coastal area of Fangcheng-Dongxing (Guangxi Province), Hainan Island and Xisha Archipelago are recently found and studied. They are characterized by frequent alternations of eolian sand deposit and soil layers (or fossil soils,pedogenetic clay layers, carboniferous mud layers, alluvial layers, ferricrust),indicating frequent alternations of action and stagnation of eolian sand currents.In addition, eolian sand beds are often found to be seperated by erosional hiatuses. No matter what types of the eolian profiles, they reflect the rise and fall of paleo-wind power and alternative changes between sedimentary environment and equilibrium environment or erosional environment, and they resulted from repeated and different event sedimentation. Formation of these eolian profiles seems to be closely related to the general instability of the Late Quaternary climate with rapid cold-warm- fluctuations, and these eolian deposits can be regarded as a distinguishing indicator for the climatic-environmental changes. The number of such climatic cycles in each profile varies from several to more than thirty. All eolian sand beds show foreset laminae inclining south or southwest, demonstrating that they were formed predominantly by northeast monsoons. When the eolian sand current was very active and lasted for a relatively long time, the eolian sediment can show a typical sequence which changes from the basal dune deposits with high-angle foreset beddings to second order bounding surface then to interdune deposit showing low-angle cross-beddings. When the eolian sand current was weak and lasted for a relatively short time, the eolian sediment accumulated in the form of low sand dunes, and is not evident in sedimentary structures.These cyclic deposits are of significance to understand the climatic history in the Late Pleistocne, to study the changing regulation of monsoon systems and the relationship between monsoon and southwest wind system, and to probe into paleo-geographic environments of shelves of China and the mechanism causing the frequent climatic changes. It is undoubtedly necessary to incorporate the eolian deposits into the reseach scope of the past global changes.It is possible that the Late Pleistocene widely-distributed eolian deposits along coastal areas of China extended into the present-day continental shelves.On shelves, these eolian sediments might not occur as continuous deserts, but were probably a serial of dune areas. According to the defined spatial distribution of these eolian dust and sand deposits, the eolian sand deposits show close genetic relation with Miaodao Loess, Xiashu Loess and other coastal eolian dust sequences,which are now being caught attention. Observations show that the coastal eolian dust sequences are always located to the southwest side of the eolian sand deposits, with a systematic decrease in grain size from northeast to southwest.These dust deposits also show alternative dust deposits and soil layers as well as associated materials and interbedded layers which are all compatible with those in the coastal eolian sand deposits.Based on the neighbouring relation between the spatial distributions of coastal eolian sand and dust deposits, four sedimentary zones can be recognized from north to south. The first zone includes the Northern Bohai Bay, shelves around the Liaodong Bay, and Miaodao Archipelago to the basins in central Shandong Province. This zone extends in a NE direction as a wide band-like area. The second zone is from the south of Shandong Peninsula to the South Yellow sea shelf and the north of the Dabie Mountain, including the lower reaches of the Yangtze caver where Xiashu Loess is distributed. The third zone is situated in the north to the Nanling Mountains, where the eolian deposits are located in low-lying areas between mountains. The southmost
出处
《第四纪研究》
CAS
CSCD
1996年第1期31-41,共11页
Quaternary Sciences
