Preliminary Study Of The Geomorphology Of Keriya River Valley On Northern Margin Of West Kunlun Mountains

Deformation and uplift of Qinghai-Tibet plateau is the hot topic of international geological researches, nowadays. Geomorphic feature of rivers within plateau is the basic element formed and recording the changes of climate-environment and tectonic characters during the deformation-uplift process. It's attempted to investigate and get the basic tectonic-geomorphic feature of Keriya River located in northwest of plateau. By the restriction of exact age of geomorphic marker, Keriya River's relief which may be observed directly was formed since 1.09Ma.B.P. Geomorphic feature records the process of earth's surface's evolvement controlled by regional tectonic-climate. Combined with geomorphic parameter, records of strata, age of geomorphic markers, and the shape of paleo-stream of Keriya River, it's succeed to acquire the processes of Keriya River geomorphic evolvement.1 Regional stratum's record shows since Cenozoic the sedimentary environment changes a lot. It experienced the early lacustrine facies, late fluvial-alluvial facies and eolian deposit. The Keriya relief since 1.09Ma.B.P restricted by the ⁴⁰Ar/³⁹Ar dates be divided into the early broad valley and late canyon by measuring geomorphic elements, geological information, and the age of geomorphic markers.2 The Keriya river stream evolvement is divided into three stages restricted by the geomorphic markers, paleo-stream, the regional paleoclimate-environment and tectonic information.1) The period of Xiyu conglomerate formed (late pliocene¹.09Ma.B.P). The regional uplift of upriver of Keriya River's leads to that the former river valley and the basin in frontal-mountain were full with a great many of fluvial facies' Xiyu conglomerate deposition in study field. In Kangsulake, the facies changes to the alluvial facies. During this period, regional climate was wetness and with frequent rainstorm. Late in the period, basalt erupts frequently in the upriver ,and flowing, depositing along the river, and now we could find the basalt remnants in five position along the Keriya River in Wugeyeke anabranch, sheep farm of Yutian county, and Kangsulake, et al. During this period, Kangsulake was the edge of the alluvial fan.2) Broad valley stage (1.09Ma.B.P～middle Pleistocene (?)). Since the basalt erupting ended, study field's uplift result in river bed is high than the erosion basis, and river bed began incision. Then, the paleo-climate was warm-wet, with frequent rainfall, Keriya River with strong dynamic, and alluvial fan extend to the basin.3) Canyon stage (Middle Pleistocene to nowadays). The geomorphic feature changed from Broad valley to canyon, and study filed was in the stage of uplift. The main climate was dry-cold, and water from upriver and regional precipitation tail off. In study field there're no alluvial fan.