Abstract:

Palygorskite  is an  important environmental and climate change  indicator mineral. The  formation of autogenic
palygorskite may  indicate a dry, high-evaporation environment. Using  field emission scanning electron microscopy  (FE-SEM)
and X-ray diffraction (XRD), we investigated  the palygorskite content and palygorskite distribution in the Zhaojiachuan section,
Xifeng, Gansu province. The results showed that palygorskite began to appear at 2.04 Ma. It has a wide distribution in the entire
red clay section. The  fibrous palygorskite crystallizes at  the edges of clay mineral particles and  the platy clay mineral particles
are gradually replaced by  fibrous palygorskite crystals, which  indicates an autogenic origin of palygorskite. We propose  that  the
palygorskite changes are correlated with  the uplift of  the Qinghai-Tibet Plateau during  the Late Miocene and   coupled with  the
development of  the Asian  inland drought.  It evidenced  the  important control of  the Qinghai-Tibet Plateau uplift over  the East
Asian monsoon and the eolian deposits. It also verified that the climate began to be arid at the Late Pliocene, and the drought was
intensified at the Pleistocene.

Key words:  palygorskite, paleoclimate, loess-red clay section, Zhaojiachuan