The Sedimentary Characteristics And Provenance Analysis Of Fangyan Formation Of Lower Cretaceous In Jianglang Mountain,ZheJiang Province

Jianglang mountain is developed typical old age danxia landform landscape,has been named as the world natural heritage site and the state 5 a-class tourist scenic spot,this paper constitutes a Jianglang mountain danxia landform Fangyan formation of lower cretaceous in the sedimentary structure,grain size characteristics,the study of the geochemical characteristics of rocks,and carry out the provenance analysis.Mainly known is as follows:(1)Jianglang below cretaceous Fangyan formation rock type to sandstone,conglomerate,gravel composition is mainly for the intermediate-acid volcanic rock,mainly tuff chip(ignimbrite,crystal tuff),followed by siliceous rocks,poor sorting characteristics generally,gravel flat degree between 1.01-1.01,sphericity of 0.54-0.76,grinding roundness of 20.87% to 20.87%.Outcrop on graded bedding,imbricate structure and the surface of the scour development.Sedimentary type is given priority to with alluvial fan and fluvial deposition,its grain size parameters of skewness,kurtosis,the standard deviation indicates the hydrodynamic condition is not stable,velocity variable but overall has the characteristics of rapid pouring accumulation.(2)Fangyan formation sandstone and conglomerate rich silicate minerals,alkaline degree is strong,lean aluminum magnesium iron,iron is low,lithophile elements relative on the high side,close relative enrichment of rare earth and heavy rare earth relative losses,Eu negative anomaly is obvious,the Sr values are relatively low,rare earth elements on different samples have the same general trend,as the same source.(3)The early cretaceous,regional background by squeezing into tension environment,Jianglangmountain in the throat become fault basin,basin near to accept the deposit of the Jurassic volcanic rocks in the material.Gap basin in rapid flash floods environment,accumulated the massive conglomerate,sandstone,forming many times alluvial fan.Consolidation after the diagenetic,regional uplift formed by a large number of vertical fracture,cementation are relatively strong sandstone under the action of vertical fracture and weathering erosion,the collapse of the issue from more accumulation of alluvial fan into this part of the glutenite preserved.,and outside under the action of dynamic mutual,finally formed today’s Jianglangmountain danxia landform landscape.Based on the formation of the landscape can be seen: danxia landform landscape of lithofacies selective,often formed alluvial fan facies is the material basis of danxia landform landscape.