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封面故事：青海共和达连海东湖相沉积及钙质结核和铁壳。共和盆地是青藏高原东北部晚新生代期间形成的一系列构造盆地之一, 出露于达连海东的共和组中下部地层剖面厚度近200 m, 以湖相沉积为主。其中的铁壳薄层和钙质结核是当时气候较为暖热和干旱的重要证据。剖面ESR测年结果表明, 共和组地层形成于上新世。哺乳动物化石和孢粉分析结果反映了区域气候由暖温带向温带以及数次冷热和干湿的变化和干旱化的总趋势。这项由赵希涛研究员主持的研究成果, 详见本期451-471页。（图片提供: 赵希涛）
Cover Story：Lake facies deposits, calcareous concretion and iron shell of Gonghe Formaiton in the east of Dalian Lake, Gonghe County, Qinghai Province. Gonghe Basin, is one of the numerous Cenozoic tectonic basins in north-eastern Tibetan Plateau. The thickness of middle-lower Gonghe Formation in east of Dalian Lake is about 200 m, in which the facies types are mainly lacustrine deposits. The iron shell and calcareous concretion are important evidences of a warmer and drier climate at that time. The ESR dating results show that the Gonghe Formation was formed in Pliocene. Mammalian fossils and sporo-pollen analysis reflect the general trend of regional climate from warm temperate zone to temperate zone, with several changes of hot to cold, and wet to dry, and mainly aridification. The research achievement was led by Professor ZHAO Xi-tao. For details, see pp. 451-471 of this issue. (Photo by ZHAO Xi-tao)
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