摘要
海岸带岩土动力学特征的差异是影响海岸侵蚀过程与方向的重要因素之一。南海北大陆海岸带主要由花岗岩风化边坡组成。通过对该海岸带的北东翼及西南翼典型花岗岩风化壳剖面的黏土矿物及风化指标研究发现,两者存在不均一性:横向上,北东翼黏土矿物主要以高岭石、伊利石为主;西南翼黏土矿物主要以高岭石、伊利石和绿泥石为主,两翼均未见较明显的蒙脱石。相同层位比较,西南翼黏土矿物总量高于北东翼。垂向上,自地表到深部,北东翼黏土矿物组合及总量无明显的分层性,而西南翼则呈明显的分层性且地表含量明显高于深部。海岸带的风化作用也存在明显的不均一性:表现为横向上,北东翼海岸带风化程度要稍弱于西南翼;垂向上,北东翼化学风化指标n(Al2O3)/n(SiO2),n(Fe2O3+Al2O3)/n(SiO2),n(TiO2)/n(Al2O3)、CIA在风化壳中呈无规律变化,而西南翼则呈明显的分层性,这种分层基本与表土层、红土层及砂土层成一定的对应关系。从化学可蚀性指标来看,由南海北大陆海岸带花岗岩风化壳演化而成的土壤均为强抗蚀性,但相同层位比较,北东翼可蚀性要稍弱于西南翼剖面。研究认为,组成南海北大陆海岸带的花岗岩风化壳之黏土矿物与风化作用的不均一性可很大程度影响海岸带的可蚀性。
Dynamic feature of rock and soil distributing along coastal belt is of essential factors controlling process and direction of coastal erosion.Continental coastal belt of northern South China Sea are dominantly composed of slopes of granitic weathering rinds（GWRs）,according to the investigation on spatial variation of clayed minerals and weathering criteria in typical profile of GWR in two limbs of the coastal belt of northern South China Sea,it is suggested that heterogeneities of spatial distribution of clayed minerals and weathering criteria in profile of GWR notably occured in the two studied profiles in GWR with the following evidences：Firstly,dis-tribution of clayed minerals are of heterogeneity in GWR.In detail,transversely,clayed minerals of GWR of northeastern limb mostly comprise of kaolinites,illites,while clayed mineral in GWRs of southwestern limb are dominantly composed of kaolinites,illites and chlorites.Smectite is not found in both profiles.Compared with the same layer in different GWRs,the total volume of clayed minerals of southwestern profile is higher than that in northeastern profile.Vertically,from surficial soil layer towards deep sandy soil layer,the layered boundary of the total quantities and associations of clayed minerals in GWR profiles of northeastern limb of coastal belt does not exist,which differing from that of GWR in southwestern limb accompanying by notable layered varied inclination.Both profiles have the features that the total quantities of clayed minerals in surficial soil are higher than those in deep soil layer.Secondly,spatial heterogeneities of chemical weathering also occur in the GWRs within the two coastal limbs.Transversely,weathering degree of GWR in northeastern limb of northern South China Sea coastal belt is more weaker than that in southwestern limb.Vertically,chemical weathering index including Al2O3/SiO2,（Fe2O3＋Al2O3）/SiO2,TiO2/Al2O3 and CIA in GWR in northeastern limb of coastal belt show a inclination of heteroclite variations,differing from that in GWR distributing in southwestern limb,which showing a layered trend of variation.Layered varying trend those chemical weathering indexes are on a large scale corresponding to surfical soil layer,red soil layer and sand soil layer respectively.Base on results of studying chemical erosive indexes,it is indicated that soils in both weathering profile are not feasible to be eroded.Compared with soil erodibility in corresponding vertical layers of differed granitic weathering rind,soil erodibility in northeastern limb of coastal belt is weaker than that in southwestern limb.In summary,spatial distributing heterogeneities of clayed minerals and weathering features in GWR profile,to a great extent,influent the erodibility of soil and relative stability of continental coastal belt of northern South China Sea.
出处
《生态环境学报》
CSCD
北大核心
2011年第2期199-207,共9页
Ecology and Environmental Sciences
基金
国家自然科学基金项目(40771129
40871140)
广东省自然科学基金项目(04101225)
中国科学院边缘海重点实验室开放基金项目
关键词
花岗岩风化壳
不均一性
大陆海岸带
可蚀性
南海北
Granitic weathering rinds（GWR）
heterogeneity
continental coastal belt
erodibility
Northern South China Sea
