中国海岸风沙沉积记录的环境变化

海岸是陆、海、气相互作用的地带。海岸风沙沉积是这一特殊动力环境的产物，是研究海岸环境演变及海平面变化的良好信息载体。中国海岸主要存在3种风沙沉积，分别为“老红砂”、沙丘岩及海岸沙丘。本文通过比较已报道的风沙堆积的物质组成、地层变化等，进一步总结了海岸风沙沉积的特征；选择已开展绝对测年的沉积剖面，利用概率密度函数分析了风沙沉积年代的分布特征，考察了中国海岸风沙活动历史，结合其他气候记录，探讨了不同地质历史时期海岸风沙堆积的关键影响因素。结果表明：“老红砂”沉积主要记录了冰期-间冰期尺度的风沙活动，在120 ka BP前后、73—55 ka BP等时期，风沙活动主要与海平面下降时陆架提供的丰富沙源和强盛的冬季风有关；而在105 ka BP、80 ka BP前后，风沙活动与高海平面时期丰富的沙源或季风气候的季节性增强有关；55 ka BP以来风沙活动强度降低更多地反映了沉积记录保存环境的变化，末次冰期海岸风沙沉积大多分布在现代海面之下，并不代表实际的海岸风沙活动减弱。相比之下，海岸沙丘沉积所记录的风沙活动主要发生在近3 000 a，可能与中国海岸冬季风的增强有关。

Environmental changes recorded by aeolian deposits in the coasts of China

The coasts are the critical zones in which complex interactions among the land， ocean and atmosphere are intensive. The coastal aeolian deposits are a product in the dynamic environments， and therefore are good archives for studying evolution of coastal environments and changes in sea level. There are mainly three types of aeolian deposits along the coasts of China， i.e.， the “Old Red Sand”， aeolianites and sand dunes. This paper reviews the sedimentary characteristics of aeolian deposits by comparing the material composition and stratigraphic variability of different types of aeolian deposits that have been reported formerly. In this study， we selected the aeolian deposits sections dated by absolutely dating， used probability density function to analyze the distribution characteristics of the ages of aeolian deposits， investigated the history of aeolian activity on various timescales， and discussed key factors affecting coastal aeolian deposition along the coasts of China. The results show that aeolian activity on a glacial-interglacial scale were mainly recorded by the “Old Red Sand”. At around 120 ka BP and 73-55 ka BP， aeolian activity was mainly related to abundant sediment supply， originated from continental shelfs due to decline in sea level and strong winter monsoon circulation； whereas at around 105 ka BP and 80 ka BP， aeolian activity was ascribed to abundant sediment supply due to intensified runoffs resulted from enhanced monsoonal circulation and/or enhanced seasonality of monsoon climate. The decrease in the intensity of aeolian activity since 55 ka BP most likely reflected changes in preservation environments of sedimentation record， and most coastal aeolian deposits during the last glacial were inundated below the modern sea level， which does not mean that actual coastal aeolian activity weakened at that time. Aeolian activity recorded by sand dune deposits mainly occurred in the past 3 000 years， which may be related to the strengthened winter monsoon during the late Holocene. Our results may have been helpful for further understanding of key processes affecting coastal aeolian depositions and environmental changes as inferred from them.