Авторы: Ao H., Dekkers M., Deng C., Zhu R.

2009 г.

GJ Int.

Here, we report an increased cooling coupled with an intensified aridification for the Xiantai fluvio-lacustrine sequence of Pleistocene age (1.9–0.1 Ma) in the Nihewan Basin (North China), known for the occurrence of several hominin sites. The cooling is related to an up-section decrease in propensity to chemical weathering as inferred from an increase in lowfield susceptibility after cycling to 700^o C. Close to 700^o C, reacting chlorite is providing the iron source for newly formed very fine-grained ferrimagnetic minerals which enhances the susceptibility signal. The reactivity of chlorite after annealing at temperatures above 600^o C is documented with X-ray diffraction and the up-section decrease in propensity to chemical weathering is confirmed by the up-section declining illite/chlorite ratios and increasing chlorite and illite contents based on X-ray diffraction analysis on selected samples.

Файл: 849.PDF