中国西部晚中新世以来气候演化初探──以甘肃临夏红色盆地中Cl-含量变化为例

Cl-是封闭湖盆中反映气候变化的敏感指标。临夏盆地晚新生代地层Cl-含量变化表明，气候的长期演化呈现明显的阶段性与周期性，在约6.3Ma气候突然产生显著的由湿变干，并于5.3～4.5Ma达到极端干旱，其干旱程度是第四纪早期的33倍，低频上，气候呈现出约400万年的干湿波动，在晚中新世与早上新世，与同周期的全球热冷（凉）波动相对，而在第四纪早期，则与冷暖相对，可能反映亚洲季风系统于晚上新世才开始逐步形成，并于第四纪初建立，3.4Ma开始强烈隆升的青藏高原可能与此密切相关。

Climatic Change Since the Late Miocene in West China: Evidence from Anion Chlorine in the Linxia Red Basin

Anion Chlorine in inland lakes is a commonindicator highly sensitive to climatic change. The variation of the content of anion chlorime in the Late Cenozoic stratigraphy in the Linxia Basim, Gansu Province, China, demonstrates that climate changes clearly in phase (step) and periodicity. The climate was shited rapidly at about 6.3 Ma from relatively humid to very dry environments, and reached an extreme dry environment between 5.3 Ma and 4.5 Ma, with drought degree 33 times the early Quaternary. In low frequency, climate presents ca. 400 ka periodicity of dry-humid fluctuation, matching global hot-cold (cool) fluctuation in similar periodicity in the Late Miocene-Early Pliocene; w hile matching global cold-warm fluctuation in the early Quaternary. The change of moistureheat regime from the Late Pliocene to the early Quaternary may suggest that the Asian monsoon system began to form gradually since the Late Pliocene and was completely established in the esrly Quaternary. The strong whole uplift of the Tibetan plateau at ca. 3.4 Ma may be responsible for such change.