华南沿海老红砂的成因与红化作用

RESEARCH ON THE FORMATION AND LATERIZATION OF THE “OLD RED SANDY SEDIMENT”ALONG THE COAST OF SOUTH CHINA

根据野外调查和室内实验分析，以及测年数据，本文讨论了华南沿海老红砂的成因、年龄与形成环境。认为老红砂是晚更新世末次冰期海岸风沙堆积，红色特征与亚间冰期的温暖古气候有关。在湿热气候下，古风成砂中含铁硅酸盐矿物氧化生成赤铁矿，而使无色石英沙粒染成红色，是其红化的主要机制。风成砂形成红色的时间不超过１万年。

One kind of semicement medium-fine sand sediment with red (10 R 4/8) of brown-red (2. 5YR 4/8) colour which is known as 'Old Red Sandy Sediment'. is intermittently distributed southwards along the coast of South China from the Pingtan island in Fujian Province. By investigating in field along the coast of South China and experimental analysing in laboratory, the authers confirm that the 'old Red Sandy Sediment' is belong to the coastal aeolian deposit formed in the last glacial period of late Pleistocene according to its distribution. landform, deposition and age, which was considered as the proximal littoral deposit in the past. The experimental research also shows that the red colour of the seiment is contributed to a film of red clay material coating on the suface of uncoloured quartz sands. which is composed of clay minerals mainly as kaolinite, mixing with ferric oxides such as hematite and geothite. The clay minerals were formed by weathering of the minerals as feldspar in the paleo-aeolian sands under the condition of a wet and hot climate in the high-temperature period of sub-interglacial or postglacial stage, and the ferric oxides are derived from oxidization ferric-silicate minerals.Development of the 'Old Red Sandy Sediment' went through about two different stages which were coastal aeolian deposition stage in the period of the sub-glacial──the lower sea level andweathering (oxidization) stage in the sub-interglacial or postglacial high-temperature period the higher sea level. The former is the original formation process of coastal aeolian deposition and the latter is the intense subsequent oxidization (laterization) process. The time of laterization is no more than 104 years.