临夏盆地晚新生代哺乳动物的多样性变化及其对气候环境背景的响应

甘肃临夏盆地的晚新生代沉积物厚度巨大,其中富含从晚渐新世到早更新世各个时代的哺乳动物化石,目前已知包括10目42科131属172种,在种级水平上全部是绝灭类型,仅少数属有现生代表。这些化石是研究哺乳动物群演化及其与气候环境背景关系的重要材料。哺乳动物的多样性和形态特征与气候环境因素密切相关,对温度、湿度和海拔高度的变化尤其敏感。依据中国陆生哺乳动物分期对临夏盆地沉积序列中的物种分异度、新纪录和消失种进行统计。临夏盆地哺乳动物的多样性变化在整个晚新生代时期相当显著,可以明显地分为不同阶段: 中中新世、晚中新世和早更新世是多样性水平最高的时期,晚渐新世至早中新世多样性最低,上新世处于中等水平。从哺乳动物多样性分析得到的临夏盆地各时期气候环境变化过程与根据其他独立证据,如群落线分析得到的结果高度吻合,也与青藏高原的隆升密切相关。

DIVERSITY VARIATIONS OF THE LATE CENOZOIC MAMMALS IN THE LINXIA BASIN AND THEIR RESPONSE TO THE CLIMATIC AND ENVIRONMENTAL BACKGROUNDS

The Late Cenozoic deposits of the Linxia Basin in Gansu,China are relatively thick,bearing abundant mammalian fossils of different periods from the Late Oligocene to the Early Pleistocene.Until now,172 species in 42 families of 10 orders have been found,all of which are extinct forms at the specific level and only a small number of genera have extant species.These fossils are important materials to study the evolution of mammalian faunas and their relationship with climatic and environmental backgrounds.The diversity and morphology of mammals are tightly related to climatic and environmental factors,and especially sensitive to changes of temperature,humidity and elevation.Interpretations to climatic and environmental changes reflect the evolution of mammals.Specific diversities,new records,and vanished species in the sedimentary sequence of the Linxia Basin are counted for each Chinese land mammal age.The diversity variations of mammals in the Linxia Basin were very noticeable throughout the Late Cenozoic,which are divided into different stages: the Middle Miocene,Late Miocene and Early Pleistocene have the highest diversities,the Late Oligocene and Early Miocene have the lowest,and the Pliocene has the moderate.The climatic and environmental variations of the Linxia Basin in different ages,which are judged from mammalian diversities,are highly consistent with other independent evidence,such as the result of the cenogram analysis,and closely relevant to the uplift of the Tibetan Plateau.