Collaborative Research: The Impact of Late Cenozoic Himalayan-Tibetan Uplift on C4 Plant Expansion, Climate and Mammalian Evolution in Northern China

各种证据表明，全球陆地环境在中新世晚期经历了重大变化。在中新世晚期以前，陆地生态系统主要由C3植物组成。C4草在今天低海拔的热带到温带生态系统中很常见，直到中新世晚期才出现，或者在当地生物量中只占很小的比例。对于晚中新世C4扩张的原因，人们提出了几种假说，但东亚地区的数据覆盖范围存在很大差距。该项目计划建立详细的晚新生代植被和气候变化的同位素记录，并记录中国北部两个化石地点-通古尔盆地和天水盆地-哺乳动物动物群的变化。这些盆地包含长序列的新近系沉积记录和丰富的脊椎动物化石。我们的主要目标是：(1)根据周转、灭绝以及物种丰富度和组成的变化，研究这些地区哺乳动物化石饮食的变化；(2)确定这些盆地中C4草传播的时间模式；(3)通过与其他地方的成熟记录(例如，南亚的Siwalik记录)进行比较，确定这些地区的碳和氧同位素变化是否反映了当地或区域对全球气候的变化；(4)确定氧同位素记录中气候条件的变化是否与碳同位素和化石记录的任何拟议的隆升事件和/或生物变化相对应；以及(5)将当地哺乳动物组合中看到的同位素趋势置于跨物种生态地貌变化的背景下。这项研究不仅将填补全球C4扩张覆盖的关键空白，而且有助于阐明晚新生代喜马拉雅-青藏隆起对中国北部C4植物扩张、气候和哺乳动物演化的影响，并检验关于晚中新世C4植物的全球扩张和喜马拉雅-青藏高原隆升样式的假说。

Various lines of evidence indicate that global terrestrial environments underwent major transformations in the late Miocene. Prior to the late Miocene, terrestrial ecosystems consisted primarily of C3 plants. C4 grasses, which are common in low-elevation tropical to temperate ecosystems today, either did not exist or were a minor component of the local biomass until the late Miocene. Several hypotheses have been proposed to explain the cause of the late Miocene C4 expansion, but there is a large gap in data coverage in East Asia. This project plans to establish detailed isotopic records of late Cenozoic vegetation and climate changes and to document changes in mammalian fauna at two fossil localities - the Tunggur and Tianshui basins - in northern China. These basins contain long sequences of Neogene sedimentary records and rich vertebrate fossils. Our primary objectives are: (1) To examine changes in the diet of fossil mammals at these localities against patterns of turnover, extinction and changes in species richness and composition; (2) To determine the temporal pattern in the spread of C4 grasses in these basins; (3) To determine whether the carbon and oxygen isotopic shifts seen at these localities reflect local or regional to global climatic changes through comparison with well-established records elsewhere (for example, the Siwalik record of South Asia); (4) To determine whether changes in climatic conditions seen in the oxygen isotopic records correspond to any of the proposed uplift events and/or biotic changes documented by carbon isotopes and fossils; and (5) To place the isotopic trends seen in local mammalian assemblages in the context of ecomorphological change across taxa.This research will not only fill a critical gap in the global coverage of C4 expansion, but also help to elucidate the impact of late Cenozoic Himalayan-Tibetan uplift on C4 plant expansion, climate and mammalian evolution in northern China and test hypotheses concerning the late Miocene "global expansion" of C4 plants and the style of uplift of the Himalayan-Tibetan Plateau.