ass=MsoNormal>ang=EN-US>The miocene sediments in the amespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />aceName w:st="on">LinxiaaceName> aceType w:st="on">BasinaceType> are important for understanding the ate w:st="on">ace w:st="on">Qinghaiace>ate>-Tibetan Plateau uplift and the east Asian monsoon developments. Hematite and goethite from the Heilinding section in the southern margin of the ace w:st="on">aceName w:st="on">LinxiaaceName> aceType w:st="on">BasinaceType>ace> were tested. The content of the hematite was high in 11.88.6 Ma, decreasing obviously at 8.6 Ma and kept stable in 8.6ascii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">～ative="False" HasSpace="True" SourceValue="5" UnitName="m">ang=EN-US>5.0 Mang=EN-US>. The trend of hematite/goethite ration was similar to hematite content. Such hematite, goethite and hematite/goethite contents in the Heilinding section probably indicate a strong aridification process since 8.6 Ma in central ace w:st="on">Asiaace>, which was linked to the Qinghai-Tibetan Plateau uplift during this time.