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China Forestry Science Academe (2018)

Study on Sediment Characteristics and Depositional Environment in Kumtagh Desert

唐进年;

Titre : Study on Sediment Characteristics and Depositional Environment in Kumtagh Desert

Auteur : 唐进年;

Grade : Doctoral Dissertation 2018

Université : China Forestry Science Academe

Résumé partiel
Kumtag Desert is the 6th biggest desert in China.The specialized research for the desert had not been conducted until the beginning of 20th century due to the extremely arid climate and harsh natural condition.It is the last desert in China where studies were conducted.Till now,there’s no systematic study on the characteristics of the sediments in the desert.Especially,studies on the formation and development of deserts as well as the ancient climate are scarce.The initial study found the natural stratigraphic section is widely distributed in Kumtag Desert,there are various sedimentation types,and there is much ancient wind-blown sand in the stratum.So the desert is an ideal place for the research on the formation and evolution of the desert in arid areas.Kumtag is located at the northern fringe of Tibet plateau,so its formation and development is closely related to the uplift of Tibet plateau.This study will provide the evidence for the uplift of Tibet plateau and the formation and evolution of the droughty environment in northwest China.Field study and observation were conducted.Samples of deposits on the surface of Kumtag Desert were collected,and samples of sediment strata on the on the typical stratigraphic section ZH on the up-reaches of Suosuo gully were also collected.Through the analysis of the sediments granularity,geochemistry,mineral composition and the climate,the particle size,geochemistry composition and distribution characteristics of the wind-blown sand in Kumtag Desert were illustrated.The analysis of sedimentation provenance further clarified the wind-blown sand provenance of Kumtagh Desert.Based on the sediment characteristics on the stratigraphic section,the ancient climate recording sequence,such as the sedimentation granularity,different substitute index of climate and geochemistry,were set up.The characteristics of ancient environment and ancient climate during the formation and development of Kumtagh Desert were disclosed.Following are the results of this study:1.The particle size of the aeolian sand in Kumtagh Desert varied between-110φ,but mostly between 13φ,that means the sand is mainly composed of medium-sized and fine sand,with average grain size of 2.25φ(0.21 mm),It is coarser than that in Takelamagan Desert whereas finer than those in Badajara and Tenggeli Deserts.Pneumatic classification is not good(averageσ=0.65).The sand becomes coarser from the southwest to northeast,which is the result of the long-term wind erosion and pneumatic classification of the prevailing northeastern and northerly winds.The provenance analysis showed the wind-blown sand comes through wind-carrying,alluvial-diluvial sediments and lacustrine sediments.So it is a short-distance carrying.2.The chemical composition of the sediments on the surface of Kumtagh desert is characterized by terrigenous intermediate rock,with Si and Al as the dominates.SiO2 content is enriching at various degree besides the area in the east.CaO is enriching in the areas of southeast and south.Other dominant elements,such as Al,Fe,Mg,K and Na are deficient.The spatial distribution of the dominant elements is different.Si and K take a significant positive relation with latitude,whereas Fe,Ca and Mg take a significant negative relation with latitude.Most of the micro-elements are enriching,among which,W,Sn,Zn,Cu,Y,Ni,Pb,Ga,Co,As and U are enriching at a high degree.The spatial difference is the result of the different provenance environment

Mots clés : surface sediment; stratal sediment; sediment characteristics; sediment environment; Kumtagh Desert;

Présentation (CNKI)

Page publiée le 9 avril 2019