阿尼玛卿山第四纪古冰川与环境演变

Quaternary Glaciations and Environment Change in the A'nyêmaqên Mountains

阿尼玛卿山是黄河上游现代冰川和第四纪古冰川最发育的地区.其中出现时间最早、发育规模最大的是倒数第三次冰期,东坡的古冰川末端下伸到海拔3600m,古雪线较现代雪线降低801m,冰川面积扩大了381km2,是现代冰川面积的16 2倍;西坡的古冰川末端下伸到海拔4100m,古雪线较现代雪线降低了635m,冰川面积增加了80 8km2,是现代冰川面积的5 8倍.之后,气候类型由海洋性逐渐过渡到大陆性,经历了湿冷—干冷—干暖的演变过程,冰川面积渐次缩小,特别是在晚末次冰期之后,进入全新世大暖期,气候急剧趋于干暖化.

The A'nyêmaqên Mountains is located in the upper reaches of the Yellow River, where glaciers are well developing and also well developed in the Quaternary. Among the Quaternary Glaciations the Antepenultimate Glaciation in the mid-Pleistocene was the earliest and the maximum one. At that time, the ancient glacier termini reached (3 600 m) a. s. l., the snow line was 801 m lower than that at present, and the glacierized area reached 381 km^(2), 16'2 times of that at present in the Qiequ River basin on the east slopes of the mountains. In the Antepenultimate and the Penultimate Galciations, the Dala Glacier in the Zhihedai River basin on the west slopes of the mountains had extended to (4 100) m a. s. l., with the snow line 539 m lower than that at present and the glacierized area of 76'8 km^(2), 5'5 times of that at present. At that time, most of the mountains were covered by snow and ice with large-scale ice caps, indicating that climatic environment belonged to maritime type. The Penultimate Glaciation, the Last Glaciation, the Neoglaciation and the Little Ice Age after the Antepenultimate Glaciation were all influenced by the continuous uplift of the Tibetan Plateau, when precipitation was deceasing and glacier termini and snow line were increasing. For example, the glacier termini retreated from (3 600 m) a. s. l. in the Antepenultimate Glaciation to (4 500 m) a. s. l. at present on the east slopes, and retreated from (4 100 m) a. s. l. in the Antepenultimate Glaciation to 4 600 m a. s. l. at present on the west slopes. After the Antepenultimate Glaciation, the glacierized area decreased in large scale and climate gradually changed from maritime type to continental type. Climate in the mountains was going to be dry and warm after the later Last Glaciation and came into the great warm period in the Holocene.