Aeolian characteristics of red stratum in Linxia Basin, China and its sedimentation environment analysis

The Cenozoic stratum in Linxia basin, Gansu, China is nearly horizontal, reddish deposits. It is usually regarded as lake sediments, very likely due to red-gray interbeds known as "zebra layer" in the sequence. Especially gray layers, absolutely different from loess soil sequence. However, there are still many paleosols with calcium nodules/or layers in the red stratum, which are similar to the Later Ter tiary Red Clay; These zebra layer tilt with the terrain in side-slope of the modern valley. We collected orientated samples for 2 groups: 1) horizontal layer, and 2) the side-slope in these zebra layer to measure their anisotropy of magnetic susceptibility (AMS). Meanwhile aeolian loess samples from both positions of the side-slope and horizontal layer were also collected for comparison. The results show that: both horizontal and titled layers of "zebra layer" are all likely to be the original stratum. These tilted red and white zebra layer following modern terrain were likely to the overlying loess, forming on the ancient terrain which accepted aeolian deposition at that time, and as a result of the latter water overflowing and submerged, reddish colour was bleached away.