喜马拉雅山中段上新世三趾马动物群生活环境的探讨

PLIOCENE ENVIRONMENT OF HIPPARION FAUNA OF MIDDLE HIMALAYA RANGE

前言喜马拉雅山的隆起是地球史上,新生代以来重大的地质事件之一。隆起的喜马拉雅山阻挡了印度洋暖湿季风的影响,形成了气候的屏障作用,致使喜马拉雅山南北坡自然环境发生了巨大的变化。因此,要了解青藏高原及相邻地区自然环境的现状和演变历史。

The basin of Jilong is one of the intermontane basins of the Himalaya fold belt during Cenozoic. According to the Hipparion Fauna found there the basin is Pliocene age. Based upon the characteristics of the sediments, two assemblages of fluvio-lacustrine facies are, recognized: one is composed of basal conglomerate, greyish siltstone, yellow siltstone with brownish yellow ferruginous layers and iron nodules, and greyish mudstone; thus, it represents a sort of fluvio-lacustrine swamp deposit; and the an other assamblage is composed of yellowish mudstone, yellowish and violet mudstone, sandstone and several thin gravel bed intercalations, a representation of fluvio-lacustrine sands and mud deposit. Three kinds of clay mineral groups are distingished. The kaolinite-hydromica group constitutes the bottom layer of the basin. It represents a sort of warm-wet climatical environment. The montmorillonite-kaolinite.-hydromica group constitutes the middle part of the basin section and represents a sort of climatical condition of alternatively hot and cold, and wet and dry. The last group of montmorillonite-hydromiea occurs on the top of the basin-section. Its environment of deposition has been already dry and hot. Based on the analysis of the heavy minerals, organic substances, carbonates, chemical make-up, pollen, aquatic living fossils and vertebrates, etc. of the Pliocene Jilong basin, and also in comparing these results with those of similar recent sedimentary environment, a conclusion is drawn that it might have been an environment of subtropic, rather hot and wet, having been absolutely different from what really is in this basin. Based on the actual data mentioned above, maps of Palaeogeography, Palaeoclimatology and Palaeoecological environment of the Hipparion Fauna were restored concerning the Jilong basin during Pliocene. This paper is not just an aid to the understanding of the changeable climate and natural environment before and after the uplifting of the highland of Qinghai and Xizang, but also is of benefit to make a further understanding on the Palaeoecological environment of Hipparion Fauna and its development history.