Through integrated analysis of the chroma parameters

magnetic susceptibility

grain size and Rb/Sr ratio on the Tuojiawan loess-paleosol profile in Yunxi County

the correlation between the features of chroma parameters and palaeoclimate change in the upper reaches of Hanjiang River was revealed. The results showed that: a* was strongly correlated with the content of iron oxide

and the average value of a* was significantly different between loess and paleosol layers

and followed the order of S0(6.34)＞MS(5.52)＞Lt(5.18)＞L0(4.98)＞L1(4.82)＞T1-al2(3.66). L* was negatively with the content of iron oxide and the organic matter

with iron oxide having a agreater effect on L*

which reached the peak in the lows layers. h* was the lowest (68.64°) in the palwosol layers

but was high in the loess layers. In contrast

a*/b* was high in the paleosol layers (0.39)

but was low in the loess layers. In Manlan Loess

there were two weak paleosol layers

i.e. L1-S2 and L1-S1

which showed higher a* and a*/b*

but lower of L*and h* than Manlan Loess. h*

a*/b*

L* and a* could be used as good indicators of climate change. A high a* and a*/b*

or a low L* and h* indicated that the climate was warm and wet

and the pedogenesis was strong. In conclusion

h*

a*/b*

L* and a* together recorded climate evolution since the late Pleistocene: the climate was cold and dry during the late Pleistocene

but a short warm and wet period happened in the glacial period (27.3-21.6 ka B.P.)

Then the climate gradually became warm and humid during the early-mid Holocene. However

cold and dry climate appeared again since the late Holocene in the region.