The “old red sand” is aeolian deposits of Pleistocene ages widely distributed on the coasts of southern China. There are still arguments about the exact time when the “old red sand” deposited and how many stages can be classified during the deposition period. In recent two years, detail studies were made on the “old red sand” along the coasts of west Guangdong and south Fujian, China. The sediment strata and ages of the “old red sand” were determined on some typical sections by field investigations, magnetic stratigraphy and earth chemistry, as well as thermoluminescenc (TL), electron spin resonance (ESR) and carbon-14 (¹⁴C) dating techniques.

1. Depositional characteristics in sections

The sections of the “old red sand” can be founded in outcrops on roadsides or in gullies in dissected platforms formed by the “old red sand”. The thickness of the “old red sand” varies in places. In general, it is about 3-5 m in thickness and some could be over 10 m. The field investigations show that “old red sand” mainly consists of fine and medium sand with a certain content of very fine sand and clay. Some of them, lying upon weathering crusts on hill slopes, contain small portion of coarse sands and fine pebbles washed from the slopes by heavy rains. Most of the “old red sand” has massive structures with no bedding and very few sections have high angle cross bedding or wedge cross bedding.

2. Stratum classification

It is difficult to classify strata of the “old red sand” by biostratigraphy due to that almost no spore-pollen or other microfossil can be found in it. So that the color, grain size, interfaces found in the sections, contents of Fe₂O₃ and magnetic susceptibility, in association with dating techniques, were used as standards to divide the strata.

The typical sections can be composed of two similar layers vertically, each of which has two units according to colors, degree of cementation of the sediments, contents of Fe₂O₃ and magnetic features. The upper unit is red, brown red or light brown red in color while the lower one dull yellow orange, yellow orange or light yellow orange. The cementation of the upper unit is better then that of the lower one. The thickness of the upper unit ranges from several ten-cm to several meters and that of the lower one is quite different everywhere. No clear boundary is found between the two units. The color changes gradually from red to yellow downwards in each layer. However, the interface between the base of the yellow unit in the upper layer and the top of the underlying red one in the lower layer can be clearly identified

3. Age of the deposits

32 dating samples taken from the “old red sand” in this study and 15 ones from published literatures show that the “old red sand” deposited during the period of time from 55400a.B.P.to 9000a.B.P., indicating that they were the aeolian deposits in middle and late Pleistoncene times. Most of the ages concentrate into two periods of 56-42Ka and 30-10Ka, denoting stronger aeolian activities in these times in which the “old red sand” in the period of 30-10Ka developed on the largest scale and had the widest distribution, induced by dryer and colder climate, more powerful winter monsoon and stronger aeolian activities in the later Wurm glacier sub-stage (Q₃³).