摘要
根据1985—1989年度的野外考察和定位重复测量、坑探、物探、砾向组构及地肮衣测年、室内分析等,总结出本区各类冰缘地貌空间分布特点和在发生学卜的联系与转化;分析了基岩寒冻风化速率、倒石堆、岩屑坡、石冰川的分布、运动特点和发育年代;讨论了冻疱和烛状冰型冻胀丘、泥流舌、石环和热喀斯特沉陷的分布、演变及成因;概述了沉积物室内分析得出的结果。
This paper is designed to discuss the periglacio-geomorphic distribution and evolution in the source region of Urumqi River on the Tianshan Mountain on the basis of repeated measurements and investigation in the field during the period of from 1985 to 1989. The major conclusions are as follows.
1. This area's frost weathering is violent. Rock crack has an average frost enlarging rate of 1.2cm/yr, and rock slope has a weathering retrograde rate of 1.1cm/yr.
2. A diversity of periglacio-geomorphic types was discovered in the study area. The series
of periglacial tor-block field-talus (or scree)-rock glaciers is formed orderly on
the steep rocky slopes. The series of periglacial tor-block field-block slope-sorted
stepes-sorted nets-sorted circles-block slope-sorted stepes-sorted nets-sorted circles-block streams-seasonal frost mounds-stone pavements is formed orderly on the gentle rocky slopes. The series of periglacial tor-block field-gelifluction lobes (or steps)-sorted stripes-nonsorted circles and nets is formed orderly on the soil
forming slopes. Stone pavements and thermokarst hollows can be found at the smooth valleys. All forms are transformable and related with each other in spatial distribution and genesis.
3. Talus movement is 146cm/yr on average on southward slope, but 73cm/yr on northward slope. The average rate of the downward movements of debris is 8.1cm/yr on block slopes.
4. Besides individual tongue-shaped rock glacier, most of the glaciers are lobate rock glaciers in the area. They belong to talus-type rock glaciers (on protalus rampart-type rock glaciers) in origin. Their average movement is 30.3cm/yr. According to lichenometry, 14C age and sedimentation analysis, they are formed during 10000-180 years BP(from the end of Upper Wang Feng Stage to the Little Ice Age).
5. Frost blisten type and candle ice type seasonal frost mounds are found in the region. The former can be divided into 5 layers, namely, surface alpine meadow soil, domelike massive ice, empty dome, loose debris as well as permafrost layer with paniculate ice; the latter can be divided into 4 layers, namely, surface alpine meadow soil, candle ice, massive ice and perafrost layer with paniculate ice. Their growing mechanisms are that the freezeback of the active layer constricts suprapermafrost ground water circulation and results in high hy-draulic potentials which either cause overlying sediments to from a frost blister, or force water to move to the ground surface along thermal contraction cracks to form a mound of candle ice.
6. The mean velocity of gelifluction lobes is 25 cm/yr.
7. Stone circle can be divided into the low center type with a settling rate of 0.6-1 cm/yr and the high center type with a lifting rate of 1-2 cm/yr.
8. Thermokarst settlement resulted from human influence there has an average sinking rate of 3 cm/yr and a horizontal displacement of 12.5 cm/yr.
9. The features of sediment in the periglacial region are as follows: (1) surface layer (0-20 cm) main substance is weathering debris; (2) 20-90 cm brown brecciated ground layer (seasonal melting layer); (3) below 0.9-1.5m, frozen brecciated ground. Main clay minerals are illite (62.5-64.7%)-chlorite (25.8-32.3%)-kaolinite(0-6.6%)-vermiculite (2.9-5.2%). A fact is confirmed by this information that the area has a physical weathering environment mainly, and the debris are transported only short distance under the cold periglacial climate.
出处
《地理学报》
EI
CSSCI
CSCD
北大核心
1992年第6期526-535,2,共11页
Acta Geographica Sinica
基金
本课题属中国科学院兰州冰川冻土所天山站课题。
关键词
冰缘地貌
石冰川
分布
乌鲁木齐河
Periglacial landform
Rock glacier
Lichenometrly
Debris fabric
Frost blister
