1.Stratigraphic-lithological features
(1)Lower Proterozoic Xingzi Group Complex
The Xingzi Group Complex is composed of a suite of hypo-metamorphic rocks in the amphibolite facies.Based on the result from the Xixiansi and Guizong sections,the Xingzi Group Complex could be divided into two suite of rock combination.The lower one is mainly composed of schist with leptite and a few of amphibolite,the upper one is dominated by the leptite with schist and a few of amphibolite.The isotope dating(zircon,U-Pb in amphibolite）indicates an age of 1.893~2.180 billion years,belonging to the Lower Proterozoic.The Xingzi Group Complex is over 2,500m thick,with an exposed area of about 42km2.It is mainly distributed in the Dapailin Ridge,Haihuisi Temple,Bailudong Academy,Xixiansi Temple,Weishanlin Ridge,Xiufeng Peak,Hongshanwa,Guizong,Warm Spring,Yikou and Dahuashan Hill.
The lower part of Xingzi Group Complex is dominated by the grayish black,mid-thick-bedded plagio-biotite schist,garnet muscovite-biotite schist and garnet-plagioclase muscovite-biotite schist,commonly with gneissic plagioclase leptite,as well as quartzitite,amphibolite,amphibolite schist,kyanite schist,sillimanite schist and staurotide-garnet macscovite-biotite schist.
The metamorphic rock series of upper Xingzi Group Complex could be subdivided into three members,it is over 1,500m in thickness.
Lower member:dominated by gray mid-thin-bedded muscovite-biotite plagioclase leptite,second by gray muscovite-biotite monzonitic leptite,K-feldspar leptite,with garnet mica quartz-schist or quartz micaceous schist,with plagio-hornblende schist sometimes.
Middle member:dominated by grayish white mid-thick-bedded gravel-bearing quartzitite,quartzitite,plagio-quartz muscovite-biotite monzonitic leptite,with muscovite-biotite quartz-schist,garnet biotite schist and magneto-quartzitite.The gravels mainly are quartz,siliceous rocks,the gravel diameter less 4mm.The original rocks are mainly the marine gravel-bearing feldspar-quartz sandstone and quartzose sandstone with siltstone and mudstone.
Upper member:dominated by grayish epidote leptite and garnet epidote leptite,with muscovite-biotite quartz-schist,staurotide-garnet muscovite-biotite schist,staurotide schist and marble bands.The original rocks are dominated by the marine calcareous mudstone and sandstone with thin-bedded muddy limestone.
The lower point of isotopic dating(zircon,U-Pb in amphibolite)indicates an age of 1.8 billion years,it means that the regional metamorphism were occurred in the Lüliang Movement which took place about 1.8 billion years ago.Such old rocks of the Xingzi Group Complex are only exposed in the Lushan Mountain area within the wide east Yangtze Plate(several hundred thousands km2),it is belonging to a very rare geological heritage,which has been studied in detail.
The leptite is derived from greywacke and lithic sandstone,the petro-chemical analysis indicates that the greywacke was formed in continental margin.
The staurotide garnet biotite quartz-schist is changed from shale,the REE composition is identical to that of greywacke and mudstone in continental margin.
The amphibolite in the Xingzi Group Complex is originated from marine basic lavas,the petro-chemical analysis indicates the ancient structural environment,theωSiO2-ω(K2O+Na2O)is mainly belonging to the tholeiitic series,second to the calc-alkaline series;theωFeO*-ωMgO-ω(K2O+Na2O)is basically belonging to the tholeiitic series,individually to the calc-alkaline series.TheωK2O is about 0.29%in average,corresponding to the marine tholeiite(0.24%).
Basically,the rocks here belong to the marine basalt area,occasionally to the continental basalt and andesite areas.The REE distribution pattern is gentle.The trace element icon shows that it has a higher Rb,Ba,Th content and a lower Cr content compared with that of the mid-ocean ridge basalt,and a lower K content and a higher Th and Hf content with that of transitional basalt.
The regional metamorphic rocks of the Xingzi Group Complex in the Weishanlin-Changshoucun Section in the north of the geopark could be subdivided into biotite,microcline,sillimanite,garnet,staurotide,amphibolite and kyanite belts.
The metamorphic facies of the Xingzi Group Complex in the southwest of the geopark could be subdivided into staurotide,kyanite and sillimanite belts.The mineral combination of the staurotide belt is Stur+Bi+Mus+Qz+Gl+Plag+Chl,the staurotide displays as the sieve metacrystal.The mineral combination of the kyanite belt in the leptite is Bi+Hb+Act+Mier+Gi(Alm)+Kyi+Ept+Sphen+Qpag.The mineral combination of the kyanite belt in plagio-amphibolite is Hb+Gi(Alm)+Ept+Plag+Sphen+cpx,the kyanite shows as the giant phanerocryst.The mineral combination of the sillimanite belt is Stur+Bi+Qz+Sill+Opaq,the sillimanite displays as the metacrystal.The sillimanite belt is often related to the thermodynamic superimposed metamorphism.
The two samplings of amphibole are the actinolite amphibole and magnesiohornblende,they are located in amphibolite facies or above of the Si-AlIV diagram,and in the epidote-amphibolite facies in theωSiO2-ω(K2O+Na2O)diagram.According to the amphibole-plagioclase thermometer(Перцук,1966),the temperature is 520℃for one mineral sample(No.522);the temperature is about 555℃based on diagram of the relationship between An content and temperature in plagioclase(Plyusnina,1982);based on the Capl-ΣAlHB diagram(Plyusnina,1982),the temperature is 545℃,and the pressure is 510MPa.
The garnet sample in the garnet staurotide macscovite-biotite plagioclase leptite is almandine(ao=1.154039nm),it locates in the sillimanite belt(near the kyanite belt)in theω(CaO+MnO)-ω(FeO+MnO)diagram,and in kyanite belt in theω(FeO+MnO)/ω(CaO+MnO)-ao diagram.According to the staurotide-garnet thermometer(Федъкин,1975),the temperature of one sample(J92156)is 540℃.And according to the garnet-biotite thermometer,the temperature of the same sample(J92156)is 500℃(Перцук,1966)and 560℃(Глебовицкий,1977).
The temperature-pressure conditions of the Xingzi Group Complex are:the metamorphic temperature ranging from 530℃to 600℃,the pressure from 400MPa to 570MPa,the estimated depth is 15km to 21km.
(2)Meso-Proterozoic Shuangqiaoshan Group Complex
The Meso-Proterozoic Shuangqiaoshan Group Complex(about 1.8~1.0 billion years ago)is widely distributed in the south of the geopark.It is a suite of epi-metamorphic rocks about 5,500m in thickness,its original rocks are marine alternated sandstone and shale,with flysch rhythm.The greywacke is mainly composed of feldspar,quartz and debris,block-like,without grain-grade.The lower part consists of thin flysch rhythm layers interbedded with a few calc-slate and spilite,the middle part is composed of thick flysch rhythm layers with a higher greywacke content,and the upper part is of thin flysch rhythm layers with a higher grayish black slate content.
(3)Neo-Proterozoic Qingbaikou System
The lower part of the Qingbaikou System could subdivided into two members,the lower member is dominated by the turbidite flysch sandstone and slate,the sedimentary tuff and volcaniclastic greywacke show a clear graded bedding,with scouring lumps of angular black slate,locally with flame-structure.There is a suite of purple turidite or contourite(several hundred meters in thickness)in the outside of the geopark,it is a key marker which is of significance in regional stratigraphic correlation.The upper member is mainly composed of the marine lavas of spilite-quartz ceratophyre,typically exposed in the Kangwanggu,Xiaojiwa and Hongshiya areas.It could be subdivided into six beds.Bed 1(basal bed)is composed of spilite,with some metablastic volcanic breccia at bottom.Bed 2 consists of grayish white and green and black metaspilite-ceratophyre,meta-quartz ceratophyre with phyllitic siltstone.Bed 3 is of bluish gray blastic sandstone and fine-grained sandstone.Bed 4 is of grayish white quartz-ceratophyre with grayish metaspilite-ceratophyre.Bed 5 is of bluish grey blastic sedimentary tuff.And Bed 6 is of epidotized quartz-ceratophyre.The isotopic dating(zircon,U-Pb in spilite of Bed 1)indicates an age of 917±36ma,and the isotopic dating(zircon,U-Pb in quartz-ceratophyre of Bed 4)indicates an age of 878±51ma.The lavas belong to the marginal sea environment.The spilite,ceratophyre and quartz-ceratophyre belong to a comagmatic evolutional series.The rock composition belongs to the tholeiitic series,showing a petro-chemical feature of lower Calc and higher Alkali,itsσis less than 4,belonging to the calc-alkalic combination of Pacific type,the REE displays the Eu-deficient type.
The upper member is only exposed along the Hanyangfeng Peak to Yuanrenlin Range,composed of a suite of continental volcanic rocks with an angular unconformity with the underlying strata.This suite of rocks is resulted from the plate collision process,with a character of mollasse formation.
(4)Neo-Proterozoic Nanhuan System
Liantuo Formation
The sandstone and conglomerate of Liantuo Fm are distributed in the north half of the geopark central area,covering an area of 55km2,with a thickness is 913m(40-1200m),it could be subdivided into three members(in ascending order):
Lower member:it is the volcaniclastic coarse-grained sandstone with thin-bedded shale and gravel-bearing feldspar quartzose sandstone.
Middle member:it is dominated by the limestone and tuffaceous sandstone,with a huge-bedded conglomerate at its bottom.The trough cross-bedding could be seen in the sandstone,indicating a littoral and delta environment.
Upper member:it is mainly composed of sedimentary tuff with quartzose sandstone and shale,it is usually of a layer of quartzose fine-grained sandstone at the top.
Nantuo tillite Formation
The Nantuo tillite Fm is composed of grayish black gravel-bearing mudstone with a thickness of 15-35m,the gravels are very complex,unsorted,the maximum diameter is only 22cm,with horizontal bedding,it shows a character of littoral floating ice deposition.
(5)Neo-Proterozoic Sininan
Lower part:it is composed of grayish black carbonaceous shale interbedded with siliceous shale,with a thickness of over 151m and fine horizontal bedding,distributed along the slope of Lushan Mountain.It is the epicontinental depostion.
Upper member:with a thickness of 220-280m,its lower part is of black mid-thin-bedded siliceous rock with horizontal bedding,the upper part of grayish black carbonaceous siliceous rock also with horizontal bedding,with pyrite cores.The distribution area of the upper member is similar to that of the lower member.It represents a shallow sea environment.
(6)Lower Paleozoic Cambrian
It is distributed in the marginal area of the foot of the Lushan Mountain.It is incompletely exposed due to the influence of detachment fault,its thickness is over 823m.
Wangyinpu Formation
The lower part is composed of black carbonaceous shale(stone coal)with a lot of phosphate nodules and a few of pyrite nodules,the horizontal bedding is present;the upper part comprises the black carbonaceous shale with thin-bedded siliceous rock.The total thickness is 171m.This Formation represents a neritic deposition,yielding Protospongia(Early Cambrian),it is of a conformity contact with the underlying Sinian strata.
Guanyindang Formation
It is composed of the yellowish green silty shale,with sericite pieces,yielding Arthricocephalus(Early Cambrian).The thickness of this Formation is 114m.It was deposited in the neritic-shelf environment.
Wushimen Limestone
It is developed in both east and west sides of the Lushan Mountain,the lower part consists of grayish black dolomitic limestone and micrite;the upper of gray banded muddy limestone with micrite and carbonaceous shale.It is over 169m in thickness,belonging the shallow platform deposition,bearing fossils:Ptychagnostus,Triplangnostus,Deronopsis,Fushouia,Eoshengia aff.quadrata and Daralishania.
(7)Lower Paleozoic Ordovician
Due to the presence of post-faults,the Ordovician System is only exposed in Gaolong and Nancheng areas.The total thickness is 850-1200m.
Kunlun Formation
It is composed of grayish white huge-bedded dolomite,pure in lithology,over 260m thick,belonging to the Lower Ordovician carbonate-tidal flat deposition,with a conformity contact with the underlying Cambrian strata.
Tangshan and Tangtou Formations
Only distributed in Gaolong area,it consists of purple reticulated muddy limestone,yielding a few of Michelinoceras elongatum,M.densum(Middle and Late Ordovician),belonging to the carbonate tidal flat deposition,with a thickness of 56m.
(8)Lower Paleozoic Silurian
It is widely distributed in the Lushan Mountain area,most of lower hilly areas is composed of the Silurian strata.Its total thickness is 2,350m,with five formations.
Lishuwo Formation
It comprises the black carbonaceous shale,with a thickness over 150m,yielding Clyptograptus sp.,Climacograptus sp.,belonging to the neritic platform deposition,with a conformity contact with underlying strata.
Dianbei Formation
It is dominated by the yellowish green shale,sandy shale,second by siltstone,muddy siltstone and fine-grained sandstone,with a thickness 336.5m,yielding Mongraptus and other bryozoan and crinoid fossils,belonging to the littoral tidal flat deposition.
Qingshui Formation
It is mainly composed of purple and yellowish green fine-grained sandstone,lithic siltstone,muddy siltstone,lithic sandstone and fine-grained quartzose sandstone,with horizontal,wavy and oblique beddings.The thickness is about 413m,yielding Lingula aff.diprafi Mansuy,and Lingulella,belonging to the littoral tidal flat deposition.
Xiajiaqiao Formation
It is mainly composed of dark gray calcareous and silty mudstone,with three layers of thin-bedded bioclastic tempesites,with scale-shape ripples and many trace fossils in siltstone,yielding many fossils of trilobite,brachiopod,bivalve and arthropod,it is belonging to the littoral tidal mud flat deposition.The thickness is 164m.
Xikeng Formation
It is dominated by varicolored muddy sandstone,lithic siltstone and lithic sandstone with siltstone and mudstone,with cross oblique beddings,yielding a few of animal fossils.It is belonging to the littoral-delta deposition.The thickness is about 545m.
(9)Upper Paleozoic Devonian System
Upper Devonian Wutong Formation
It consists of purple and white mid-thick-bedded quartzose sandstone,sandy conglomerate,gravel-bearing quartzose sandstone,with cross bedding.The gravels are good in roundness and sorting,belonging to the fluvial deposition,over 18m thick,with a disconformity contact with the underlying Silurian strata.The Lower and Middle Devonian strata are absent here,it indicates that the vertical uplifting event took place in the Lushan Mountain area during the Caledonian movement.
(10)Upper Paleozoic Carboniferous System
It is distributed in the out side of west geopark and beach area of Poyang Lake.The Lower part of Huanglong Formation is about 60m in thickness,with dolomitic limestone and sparry limestone at the bottom,and thick-bedded limestone at the top,yielding a lot of marine fossils.The Chuanshan Formation is about 50m in thickness,psammitic dolomite in lower part and gray and pale red bioclastic limestone in the upper part,yielding abundant fusulinid and coral fossils.
(11)Upper Paleozoic Permian System
The distribution is similar to that of Carboniferous System.The Lower part of Xixia Formation is composed of gray bituminous chert limestone,about 150m thick,yielding a lot of marine fossils;the Maokou Formation,about 250m thick,consists of grey and pale red dense massive limestone,bearing a large amount of marine fossils.The Upper part of Wujiaping Formation,about 44m thick,is of black argillaceous limestone with carbonaceous shale and coal beds at the bottom,the gray chert limestone at the top,containing marine fossils.The Changxing Formation is,about 110m thick,composed of siliceous rock in the lower and massive limestone in the upper,yielding a great deal of fusulinid and brachiopod fossils.
(12)Mesozoic Upper Cretaceous
The Upper Cretaceous consists of the continental lacustrine red beds over 3,600m thick.Within the scope of the geopark,only the purple conglomerate of slope alluvial deposition is exposed,about 100m thick.The gravels are dominated by the Nanhuan sandstone,Sinian siliceous rocks and Cambrian muddy limestone.The gravels with a maximum diameter 25cm are angular,poor-sorted,purple mud cemented.It is of an unconformity contact with the underlying strata.
According to all these above,we can propose that the Lushan Mountain was as a sediment source area,the Sinian-Cambrian strata were denudated,the pre-Sinian strata might be not exposed during that period.
(13)Cenozoic Neogene
It is exposed in the northwest area of Xilinsi Temple,northwest of the geopark.The Neogene is a suite of red rocks deposited in interior basin.It has proved by drilling that the 90%or more gravels are derived from the Paleozoic limestone.It is mainly composed of red mid-thick-bedded pebble-bearing lithic siltstone interbedded with calcareous siltstone,with thin-bedded greywacke and mudstone,with massive and horizontal beddings,belonging to the lacustrine deposition of interior basin.The total thickness is over 1,500m,it is of a conformity contact with the underlying Cretaceous strata.
(14)Quaternary
The Quaternary moraine deposition is widely spread in the geopark,described as follows in ascending order:
Dapailing-phase moraine muddy boulder bed
This bed is only exposed in Dapailing Ridge,with an elevation of 284m.The muddy boulders are purple,poor-sorted,ranging from 0.5 to 1m,the maximum 7.23m.Most of boulders come from the Sinian sandstone,highly rounded.This bed is about 5-12m in thickness,with an unconformity contact with the underlying schist of Lower Proterozoic Xingzi Group Complex.The huge boulders ploughing into the schist or epigenetic structures could be observed.It has been proved by mining that the kaoline deposit underlying the Dapailing moraine muddy boulder bed might be formed under a humid and heat climate during the Neogene period.According to the paleomagnetic data,the Dapailing-phase moraine muddy boulder bed was formed about 3-2.5ma ago(Early Early Pleistocene).
Dapailing-Poyang interglacial-phase residual terra roja bed
The residual terra roja bed is discovered in Jindingshan Hill,the thickness is unknown,just under the Poyang-phase moraine muddy boulder bed.
Poyang-phase moraine muddy boulder bed
It is distributed in Jindingshan,Daling and Changling areas,the highest elevation is 193m.The boulder composition and structure are similar to these of the Dapailing-phase bed.This bed is about 9.5m thick,boulder size varied,un-sorted,boulder diameter about 1-2m,the maximum 7.5m.There is a Fe-film on the boulder surface,which might be formed in the interglacial period.Most of boulders came from the top of Lushan Mountain.According to the paleomagnetic data,the Poyang-phase moraine muddy boulder bed was formed about 1.8-1.5ma ago(Early Pleistocene).
Poyang-Dagu interglacial-phase residual terra roja bed
The residual terra roja bed is discovered in Saiyang of west Lushan Mountain and Matouzhen of east Lushan Mountain.The thickness is about 2.87m,it is just covered by the Dagu-phase moraine muddy boulder bed(Middle Pleistocene).This bed is composed of brownish red sabulous pulverulent soil,with a large amount of muscovite in the exposure of Matouzhen section.
Dagu-phase moraine muddy boulder bed
It is widely distributed in surrounding area of Lushan Mountain,Jiujiang City and Poyang Lake beach.The highest elevation is 150m,its thickness ranging from 3m to 9.8m.The boulders are mainly the Nanhuan sandy conglomerate,quartzitite,and a few of siliceous rocks and leptite.Most of boulders are semi-rounded and sub-angular,un-sorted.The boulder diameter is about 0.2-0.7m,the maximum 3.2m.There are oblique structure in Xiaqingshan area and lump structure in Jinshishanzhuang area.There are several thrusted structures in the boulder bed in Shetouling Ridge,and epigenetic structures at the top of underlying Cambrian shale.A large amount of glacial striated pebbles and drift boulders has been found in the margin of a small reservoir in Zhangjialaowu,the orientation of glacial streak is in 315o,consistent with the glacial flow direction.The glacial drift boulders are discovered in Xiaqiangshan and Xinqiao areas.The glacial wedge-structure is found in Huangni,an area.
The exposed Dagu-phase moarine muddy boulders are similar in color(brownish red or brown)to that of the Dapailing and Poyang-phase ones.However,we have found that the boulder color changes from purple in surface to grayish white in deep depth in Xiaqingshan section.It indicates that these moraine muddy boulders have not been affected under the interglacial humid and heat climate.
The rough dentation of outwash deposition and moraine muddy boulders has been founded in the terminal moraines in Xinqiao and Chemical Fibre Factory,or outwash deposition lying on the moraine muddy boulder beds.
According to the paleomagnetic data,the Dagu-phase moraine muddy boulder bed was formed about 1.1-0.9ma ago(Early Middle Pleistocene).
Dagu-Lushan interglacial reticulated terra jora bed
The reticulated terra jora bed,about 4.5m thick,is widely and stably distributed in the Lushan Mountain area,it is a regional marker bed.There are a large amount of opal worm-like reticulates in the terra jora bed,indicating a humid and heat climate.
Lushan-phase moraine muddy boulder bed
It is only exposed in the valley entrance of Daxiaochang with an elevation of 1050m.It is a yellowish red and grayish white muddy boulder bed.The boulder size is varied,the maximum boulder diameter 3.5m,the boulders are un-sorted,subrounded or angular.There is a glacial streak about 150mm long on a huge boulder.This bed is about 2.4-4m thick,directly overlying on the Nanhuan sandstone.According to the paleomagnetic data,the Lushan-phase moraine muddy boulder bed was formed about 0.4-0.2ma ago(Early Late Pleistocene).
It is worthy to point out that there is a“ring structure”about 0.8m in diameter arranged by small pebbles in the right side of this section.This structure might be resulted from the effect of subglacial spiral current.
Lulin detritus clay bed
It is,only 0.2-1.5m thick,composed of yellowish brown detritus clay bed,exposed in the two sides of Dayueshan Hill,Hankouxia Gorge and Mumachang areas,with an elevation of over 1,000m.The detritus is unsorted,loosely connected,mostly angular,the maximum diameter is about 1m.The detritus is dominated by quartzose sandstone,pebble-bearing sandstone,second by slate.It is considered as the Late Pleistocene Lulin epiglacial epoch deposition.
Xingang clay bed
There is a loess bed about 4m exposed in hilly area between the Lushan Mountain and Poyang Lake,sometime with gray silty clay.The regional correlation indicates this bed was deposited in a lake under the Late Late Pleistocene dry climate.This bed is the same horizontal with the yellow sand bed in the Poyang Lake beach.
Scientists from the Chinese Academy of Geological Sciences and other units have studied the Pleistocene tillites in detail with many modern techniques in the Lushan Mountain.
Boulder fabric features
The boulder fabric features of the Middle Pleistocene moraine boulder beds have been studied.It is indicated that the average boulder diameter does not become smaller as the boulders far away from the mountain body,but the change is contrast,it could not be explained by debris flow or river.It is only by glacier.Besides,the sorting degree and roundness are not determined by the transportation distance,it also expresses that the transportation media of these boulders is glacier.
Through the systematic measurement on the orientation,dipping direction,dip angle of theα-axis and ab surface of these boulders,the equidensity diagram shows that the direction of boulder arrangement is different from that of debris flow boulder.The arrangement of boulders in inner side of each moraine is less regular than that in outer side.All these imply that the transportation media of these boulders was glacier,not debris flow,nor river.
Geochemical features
The trace elements Cu,Zr and Mn are necessary for plant growth.These elements are sparsely distributed in moraines and outwash sediment,but concentrated in interglacial sediment.In the moraines and outwash sediment,the contents of SiO2,Al2O3,MnO,Na2O and K2O are lower,and the contents of FeO2 and P2O5 are higher,it is closely related to heat or cool climate.The ratioes of SiO2/Al2O3(Ki value),FeO/Fe2O3and CaO/MgO are higher than these in interglacial epoch.
The leached coefficient(SiO2/RO+R2O),ferrosilicine coefficient(FeO/Fe2O3)and residual coefficient(R2O3/RO+R2O)in moraines are lower than these in interglacial sediment.It indicates the changing role of cold,heat and dry climate.
Clay mineral features
Through the thermography,X-ray diffraction analysis,energy spectroscopy and transmission electron microscope,it is proved that the Quaternary clay minerals in Lushan Mountain are dominated by kaoline,second by idrargillite,hydromica,montmorillonite-illite mixed layer.The illite is formed in an alkaline environment under the cold climate,and the kaoline is formed in an acid environment under the humid and heat climate.The illite would change into the open illite even kaoline in an acid environment under the humid and heat climate.The horizons with the illite and open illite indicate that they were formed in an alkaline environment under the cold climate.It is estimated by statistics that there are illite(dominated),open illite and kaoline in the four glacial-phase sediments,the kaoline was secondary one during the interglacial epochs.The kaoline is dominated in the interglacial sediments,with open illite and montmorillonite mixed layers.
Quartz grain surface features
Through the scanning electron microscope analysis,the Quaternary quartz grain surface in the grayish white moraine muddy boulder bed in Xiaqingshan area displays the features of conchoidal fractures,streaks,parallel steps,cleavage planes,squeezing and abrasive pits and upturned cleavage planes,belonging to the products of glacier.The Quaternary quartz grain surface in the top of boulder bed in the Chemical Fibre Factory shows the features of conchoidal fractures,V-shaped impact pits and milling pits,belonging to the ice water deposition.The Quaternary quartz grain surface in the alluvial and deluvial fan bed in Wangjiapo area shows the features of V-shaped impact pits,conchoidal fractures and parallel cleavage planes,indicating to the alluvial and deluvial sediment.The quartz grain surface in the top of purple weathered bed in Xiaqingshan and Chemical Fibre Factory shows the features of solution pits and fissures,siliceous deposition and re-crystallized gypsum,implying to the change of glacial deposition during the interglacial humid and hot environment afterward.
The presence of X-shaped deformed lattice dislocation in some quartz grains in the Dagu-phase moraine boulders indicates that the quartz grains were suffered a slow and long-term shearing stress effect.Such phenomenon occurred in loose sediment just indicates that these quartz grains had been suffered a slow shearing stress effect of glaciers.
The mineral mosaic-like texture is widely occurred in the moraines,this kind of texture is characterized by the straight and clear boundaries between two minerals,without solution in the mosaic part,neither secondary mineral insert.The mineral mosaic-like texture could not be occurred in the debris flow condition.Such mosaic-like texture is only formed under the condition of the long-term strong pressure of glacier.In addition,there is the mineral crosscut commonly in moraines.
2.Magmatite
(1)Neo-Proterozoic Guanyinqiao granitic gneiss
It is mainly distributed in the Guanyingqiao,Xiufeng Peak,Jilongshan Peak and Gaojialing Ridge in the east side of Lushan Mountain,with an area of about 28km2.
Geological characteristics
The Guanyinqiao granitic gneiss is emplaced in the median-hypometamorphic rocks of Lower Proterozoic Xingzi Group Complex at the core of Lushan Mountain MCC.The orientation of gneissic layering is basically consistent with that of shcistosity of surrounding rocks.The boundary of the granitic gneiss body shows an irregular elliptical shape,declining outward,the dip angle of gneissic layering ranges from 15°to 20°.The boundary is figure-like,vein-like and serrated,wavy pitching toward the surrounding rocks.There are commonly xenoliths of surrounding rocks and topping residues in gneiss.It is inferred that the granite intrusion(emplacement)was in form of diaprism.
The zircon-dating(U-Pb)in the Guanyinqiao granitic gneiss is 823±64ma,this age is just equal to the time of Yangtze Plate collision,it indicates that the Guanyinqiao granitic gneiss(original granite)is the product of Jinning Movement.
The schistosity formed in the regional metamorphism in the Xingzi Group Complex was replaced by the mylonitic ductile shearing cleavages in post-dynamic metamorphism.It is impossible that the gneissic layering was formed in the same orogeny,it should be the ductile shearing cleavages formed during the process of Lushan MCC.Therefore,the orientation of gneissic layering is the same to that of ductile shearing cleavages in the surrounding rocks.
Petrological features
The Guanyinqiao granitic gneiss is mainly composed of schlieric fine-grained biotite monzonitic gneiss and schlieric fine-grained biotite K-feldspar gneiss.Two kinds of rocks are closely coexisted.
(2)Late Yanshanian Donggushan granite
Geological characteristics
The Donggushan granite is intruded into the metamorphic rocks of Lower Proterozoic Xingzi Group Complex.It is,with an area of 16km2,exposed in the southeast margin of the core of Lushan Mountain MCC.The K-Ar dating indicates an age of 132~115ma,corresponding to the Late Yanshanian period.This granite body is of a hybrid transition contact with the surrounding rocks,there is no thermometamorphism on the residues and contact margin.The granite body has no a clear chilled border,neither pegmatite crust,the facies structure is unclear.
Petrological features
The Donggushan granite is dominated by grayish white median-fine-grained muscovite-biotite granite,second by grayish white fine-grained muscovite-biotite granite,the mineral grain is generally 0.6-1.5mm in diameter.The plagioclase is dominated by the oligoclase-albite,the polysynthetic twin developed,partially by andesine,with a clear ring structure.
(3)Late Yanshanian Yujingshan granite
The Yujingshan granite body is at the core of the MCC,exposed in the southeast side of Yujingshan Hill.
Geological characteristics
There are two stages of granite intrusive bodies,the first stage body is the granite ductolith,only 0.8km2 in area,the surrounding rock is the Neo-Proterozoic Guanyinqiao granitic gneiss.The intrusive surface is uneven,pitching outward,with pegmatite veins filled along the contact border.The second stage body is a small granite knob,intruded into the first-stage granite body and the metamorphic rocks of the Xingzi Group Complex,the contact border is irregularly wavy,locally with xenoliths.
Petrological featuers
The first stage body is the grayish white median-fine-grained muscovite-biotite monzonitic granite,the second one is grayish black fine-grained muscovite-biotite monzonitic granite.They show a fine-grained granitic structure and weak gneissic structure(mylonitic layering).The plagioclase is of polysynthetic twin and Karlsbad-albite compound twin,belonging to the oligoclase-albite series(Am=25-10).The quartz displays an undulating extinction,the mica is thick platy,strong polychrism.The second-stage granite is dominated by the plagioclase,over 45%,microcline only 10-15%,quartz about 20%,and biotite as high as 10%.
(4)Late Yanshanian Haihui granite
It is located in the north end of the MCC,exposed in the south and north ends of Haihuizhen town.The rock age is 107ma(K-Ar dating).
Geological characteristics
The Haihui granite is intruded into the mica-schist of the Lower Proterozoic Xingzi Group Complex,its north end into the Nanhuan Liantuo sandstone.The intrusive border is wavy.There are a large amount of muscovite granite and granitic pegmatite veins in the mica-granite in outer contact zone.
Petrological features
The Haihui granite is mainly composed of median-fine-grained porphyritic biotite granite,with a large amount of residues and xenoliths.Affected by ductile shearing zone,it has a weak gneissic structure.The porphyritic crystals are dominated by the microcline and plagioclase,over 20-25%,the grain size up to 3×4~5×10mm.
(5)Granitic pegmatite field
More than 400 granitic pegmatite veins within the geopark are defined in the scope of the inner core of the Lushan MCC.The metamorphic rock in the inner core of Xingzi Group Complex or the Late Proterozoic granitic gneiss came from the mid-crust about 15km deep,belonging to the typical granitic pegmatite field.The three isotopic dates(K-Ar dating)of 104ma,126.7ma and 153.3ma indicate the Yanshanian Movement.
The shapes of pegmatite veins are complex,intercrossed frequently,its width ranges from 0.1m to 25m,1-2m in general.The longest vein is up to 1,100m.The major mineral is the K-feldspar,over 50-60%,the maximum crystal is 2-5cm long,there are fine muscovite and quartz in crystals,with a graphic texture.The quartz is up to 27-30%,biggest one 3cm long,the muscovite 15%,the largest crystal about 8cm.The accessory minerals are beryl,columbotantalite and monazite.
(6)Gabbro-diabase dike group
A series of SN-oriented gabbro-diabase dikes are distributed in Xiejiashan,Yikou and Hengtang areas at the south end of the geopark.The dike is 2,200m long and 1-24m wide,vertically filled along the faults,cut through the schistosity in the Lower Proterozoic Xingzi Group Complex.
The content of plagioclase in the gabbro-diabase is as high as 60-65%,and the pyroxene 25-30%,the biotite 1-3%,and the magnetite about 2%,with a typical pyroxene structure.The rare earth elementΣCe/ΣY=0.84,Eu=1.69 indicates a type of HREE,originated from the upper mantle.
The zircon dating(U-Pb)indicates an age of 136ma,belonging to the Late Yanshanian Movement.
(7)Garnet-amphibolite leptite
There are a few of garnet-amphibolite lumps in the inner core of the MCC of Lower Proterozoic Xingzi Group Complex,the smallest one is only 0.3×0.1m,the maximum 12m in diameter,mainly distributed in Xiejiashan and north of Warm Spring.The garnet crystal is big,3-5mm in diameter,with a sieve structure.The amphibolite is taramite,with a few of irregular quartz grains.Some considered that the taramite was degraded from the virescite.If it is true,the original rock should be eclogite,belonging to the tectonic emplacement of pyrolite.
3 Regional structural features
3.1 Tectonics and structural layer characteristics
Tectonically,the Mount Lushan Geopark is situated in the“Pengshan-Lushan Terrane”of the east section of Yangtze Plate.
The exposed Lower Proterozoic Xingzi Group Complex is a part of crystallized basement of the Yangtze Plate,belonging to the first structural layer,which was metamorphosed during the Lüliang Movement about 1.8 billion years ago.The regional metamorphic rock is the amphibolite facies.
The second structural layer is composed of Mesoproterozoic Shuangqiaoshan Group Complex and Neoproterozoic Qingbaikou System,with a thickness of over 5,500m,the exposed area is about 50%of the geopark.The lower part of this layer is dominated by the greywacke of littoral-neritic passive continental margin alternated with shale of bypathical environment,by the turbidite flysch of active continental margin of sipllite-quartz-ceratophyre formation in the upper part.It was metamorphosed and deformed during the Jinning Movement about 850-800ma years ago.The metamorphic rock is the low greenschist facies,the reclined close and inverted folds are developed.This layer formed the folded basement of the Yangtze Platform,when the Yangtze Plate was formed.
From Sinian to the Middle Triassic,it was the epicontinental environment,the sedimentary cap rock was formed.It is worthy to point out that the Lower and Middle Devonian are absent in the north of Jiangxi,the Upper Devonian and Lower Carboniferous strata are the continental clastic deposition,with a disconformity contact with the underlying Upper Silurian delta clastics.It indicates that the Caledonian Movement here just displays a vertical uplifting.
The third structural layer is the sedimentary cap rock of the Platform,which was deformed during the Indosinian Movement,dominated by the“Jura-type”folds.The structural direction is depended.The major folds are the Jiuling Composite Anticline and Jiujiang Composite Syncline.Within the scope of the geopark,it is an NE-oriented gentle and broad composite multi-folded anticline,the strata are inverted from the NW wing to pitching end.
It was the basin-range development stage in the Jurassic,the crust was extending in a long period.A series of NNE-SSW and NEE-SWW left slip shearing fault zones were occurred,accompanied by large-scale granite intrusions.The granite diapiric dome is occurred in the Pengshan area.The detachment structures and the MCC were formed during that period.
Generally,the major detachment faults are occurred between the sedimentary cap rock at the uplifted areas and metamorphosed folded basement,or the areas with huge thick carbonaceous shale in the cap rocks.The Silurian sandstone and shale are widely distributed in the geopark,they became the middle shear-slip zones of the detachment extending,locally with strong superficial folds,structural windows and detached masses.The front squeezed zones are often occurred in the Upper Paleozoic and Mesozoic strata in the composite synclines.
3.2 Major structural features
(1)Fold
The original folded shapes in the crystallized basement of Xingzi Group Complex are hard to be reconstructed due to the late intensive deformation,but the different folds are still visible in different forms.
The reclined composite folds are dominated in the folded basement of Meso-Neo-Proterozoic epimetamorphic rocks,the close homoclinal folds are the scond.The folded axis directs to the west-east.The inverted anticlines are occurred along the Yangtianping to Maerfeng Peak.
The asymmetric composite brachy-folds are dominated in the Sinian-Middle Trassic cap rocks.The axis direction is greatly varied.These folds were taken place during the Indosinian period.
The major fold in the gepark is the Lushan Composite Anticline,composed of the Qingliansi Syncline,Dayueshan Anticline,Dazhaishan Syncline and Hubeiling Anticline.The axis is on the NE-NW in general.The post detachment faults and associated detachment folds are on the fold wings.The axial plane of the folds reclines to SE.The Hubeiling Anticline is an inverted anticline,pitching toward SE,dip angle about 60°,the strata in its NW wing are inverted,and the strata in the SE wing are gentle,with a dip angle only 25°.
(2)Fractures
Lushan MCC structure
The Lushan MCC structure is the major structure in the geopark,distributed in the central area of the geopark.
The inner core of the MCC is composed of the intensively deformed and metamorphosed crystallized basement of the Lower Proterozoic Xingzi Group Complex.It displays an elliptical shape,the diameter of the inner core is about 7km,exposed in an isolated dome.
The basement rock of the Lushan MCC is located in the ductile deformed area,with the Mesozoic basic dikes and granite intrusive bodies of different size,strongly deformed.There is a blasto-mylonite belt near the décollement fault,the mylonitization is weakened as far away from the fault.The dynamic recrystallization is strong in the minerals in the blasto-mylonite belt,the amphibolite is extended and becomes silk-banded,rib-like,oriented arranged.The quartz and feldspar grains in the granitic mylonite show in“s”or“d”shapes,rotated,oriented arranged,with the typical structure of S-C structural rock.The micas in leptite are deformed as“mica-fish”-like extending lineation.The mylonitic schistosity is clear and developed,parallel to the décollement fault.
A low-angle main décollement normal fault at the top of the inner core of the MCC is intensified accompanied by the granite diapirism and extending detachment dome,the main décollement fault displays a long back-like shape.There are some strata absent in different localities in the décollement fault,but the lineation and bedding on the rocks of the upper and lower blocks seem to parallel to the fault plane,sometimes with chloritized cataclastite,microbreccia and fault gouge.The cataclastite is in lenticular structure by shearing extension,it could be observed in Yuanjiapeng,Yikou and Xiaomushan areas.As the main décollement fault declining toward plastic area,the cataclastite gradually changes into reticular ductile shearing belts.During the long-term process,several low-angle huge plough-like detachment normal faults were formed in the upper and lower blocks.
The metamorphic intensity in the rocks of upper block is much weaker than that in the lower one.There are only a few of epi-décollement faults in the cap rocks.
Based on the measurement of two sets of lineation in the Xingzi Group Complex in the east slope of Lushan Mountain,the detachment direction is shifting from the SE to NW,the extending lineation pitching to the NW direction.The microscopic observation gets a same result.
In sum,the folded layers,vaginal folds,extending lineation,S-C foliation,microscopic structure and associated structures show that the upper block of the main décollement fault slips toward NW direction.
The strain measurement indicates that the shearing strain rate in the inner zone of the metamorphic core is higher than that in the outer one,this is identical to that the deep ductile deforming rate is higher than the shallow one.
The shift rate is,estimated by detailed measurement,up to 10.72cm in the 8cm-wide shear zone in the major ductile shear zone,but the shift rate up to 27cm in the central area.It indicates that the shear shift rate in the main décollement fault is much higher than that in the detachment faults on the upper block of the main décollement fault.
The inner core has not only the Mesozoic basic dike group,but also some garnet-amphibolite lumps whose origin and causes are unknown,these lumps are mostly in the ductile shear zone.However,there are not only the Mesozoic multi-phase granite intrusive bodies in the inner core,but also a large amount of granitic pegmatite veins,the pegmatite field is limited in the inner complex.The thermodynamic superimposed metamorphism is clear in the main décollement fault,some components are absent in plagioclase,the An=0-22 is absent,but An=23,An=40-41 and An=83 are present,implying a relatively higher thermodynamic metamorphism.The dislocation of the main décollement fault is varied,biggest in the east segment,many strata are absent,the Lower Proterozoic strata are directly of a low-angle normal fault contact with the Upper Sinian strata,the carbonaceous shale in rocks of the upper block has been changed into the graphite schist(in Taohuapu area).The dislocation is smaller in the west segment.The main décollement fault has a long,continuous but stepwise evolutional process.The mylonite is superimposed by the late dense extending lineation of ductile and fragile deformation.The Mesozoic granitic pegmatite and plagioclasite veins were affected by the unified ductile shearing.There are two suites of cap rocks in the Lushan MCC structure.The lower cap rocks are composed of Meso-Neo-Proterozoic epi-metamorphic rocks,and the upper one consists of the platform cap rocks.The inner core could directly contact with the upper and lower cap rocks by detachment faults.There are not only the folded layer structures in the lower cap rocks,but also a series of densely penetrative shearing schistous belts,interlayer plastic deformed belts and vaginal folds.The ductile and ductile-fragile mylonite is only on the detachment fault zone.Theβdirection of folded layers is coincident with the main décollement fault.
The upper cap rocks are characterized by the ductile-fragile deformation,the extending folds and gravity detachment faults are well developed.The gravity detachment faults are controlled by the interlayer detachment faults and wetting layers.Sometimes,you can see that the newer strata are far away overlying on the older strata.The plastic fold groups are well developed in the Nanhuan sandstone near the upper block of main décollement fault,mainly exposed in a scope of 7.5km long and 500-1,000m long along Jiudiegu,Wuxiaofeng and Baihejian area,it could be distinguished into three belts based on their morphology:
IIA type:Semi-accordant bedding lying fold:Mainly developed in the interbeds of blastosandstone and blastosiltstone,tuffaceous phyllite.The close folds are developed in the harder beds,normal fan cleavages developed;and the complete cleavage and crumples in the weaker beds,with an inverted fan cleavage,there are a series of regularly“Z”-,“M”-and“S”-shaped secondary folds in a relatively big fold.The angular folds,lying folds and“S”-shaped folds are developed.
IIB type:Discordant bedding lying fold:Mainly distributed in the thick-bedded sandy tuffaceous phyllite,blasto-siltstone with thin-bedded blasto-quartzose sandstone,blasto-pebbly sandstone.There are a series of a-shaped conic,pan-like and vaginal discordant folds of different scales.The extending mineral group could be seen in the surface of harder beds,the orientation of extending lineation is 360°,dip angle 5°-15°;it is of complete cleavage and shistosity in the weaker beds.
IIC type:Accordant bedding lying fold:It is mainly distributed in the interbeds of gray blasto-silty sedimentary tuff and monozonitic schist and muscovite schist.These folds are similar or parallel to each other,in different patterns,showing a series of podiform folds,wavy bending.There are multi-phase mineral growth and extending lineation on bedding surface,locally with biolite growth lineation.
Judged by its exposed area,developed degree and perfect morphology,the plastic fold group is of great value in science and tourism.
Multi-level detachment faults
To take the Lushan MCC as the core,there are a series of outward-pitching detachment faults and associated detachment folded systems on the upper block of the main décollement fault.These detachment faults mostly display a plough-shaped(steep in upper and gentle in lower).
Bedding detachment fault zone at the base of Nanhuan System
There is a plough-like bedding detachment fault zone at the base of Liantuo Formation,distributed in Beifengkou,Shangxiaofeng,Ercengya,Baihejian,Yuanjiapeng and Guankou areas.The shallow-level detachment faults are superimposed onto the deep-level detachment faults.The shallow-level detachment faults form a high-angle bedding detachment normal fault zone about several ten meters wide in sandstone.As the sandstone slips down along bedding,the shearing lenses and a large of quartz lenticular veins are formed.During the process of sandstone slipping down,some secondary detachment faults and gravity detachment folds are also formed,locally very intensive,such as in Shimenjian,Qianfofeng,Biyunsi Temple and Luanluocheng areas.
The bedding detachment faults between the Lower and Upper Sinian
There is a set of bedding detachment normal faults zone between the Nanhuan tillite and Sinian carbonaceous shale.It is distinct in the east and west sides of Lushan Mountain,the Nanhuan tillite is absent there.
The bedding detachment faults at the bottom of Cambrian
The Cambrian carbonaceous shale is often acted as the wetting bed,the bedding detachment faults make the large amount of intensive gravity detachment folds occur in the Wushimen marls,we can see them in Mazushan and Zhujiashan areas.
The bedding detachment faults at the bottom of Silurian
Taking the black shale at the bottom of Silurian as the wetting bed,the bedding detachment faults are the largest in scale,it makes the Silurian slip far away onto the older strata.For instances,the Fuchuanshan and Nijiafan Detachment Structural Windows are formed by the Silurian sandy shale onto the Ordovician dolomite.
Ganjiang Fracture Zone
A large-scale left strike-slip shearing zone,called as Ganjiang Fracture Zone,is at the east side of Lushan MCC,it is about 500-1,000m wide,extending from Liuxingshan Hill on the south,northward to Taohuapu,Dapailing Ridge and Shiniushan Hill via Wulipai.It is mainly composed of the NNE-SSW-oriented granitic mylonite zone,about 500-750m wide.The S-C fabric is developed in the mylonite zone.The occurrence of Ss foliation is:130°~140°∠10°~15°,and the occurrence of Sc foliation is:120°~130°∠15°~20°.The plagioclase commonly becomes“s”-and“d”-shaped rotated porphyroclast,the two ends of mica are extending,the garnet shows a snowball rotation,indicating the shearing zone was a left strike-slip one in the earliest stage.This ductile shearing zone is modified by the detachment fault at the margin of MCC,the dense low-angle ductile-fragile shear belts(1 per 2-3mm)are superimposed on the granite mylonite zone of several hundred meters thick.There are dense mineral growth and extending lineation on shearing faces,indicating a character of normal fault.
Fault-block boundary fault
The Lushan Block Mountain was formed in two stages.The first stage is in the Late Cretaceous,when there were two huge NNE-NE left strike-slip faults on the two sides of Lushan Mountain,the two faults sheared the Lushan Mountain into a huge lense,this is the primary shape of the Lushan Block Mountain.The second stage is the period after the formation of MCC,when the crust was still in extending strain state.Dominated by the basal detachment fault,a series of bedding slip domino-type normal faults were occurred in the cap rocks.These faults slipped down from the inside toward the outside,then,the lofty Lushan Block Mountain was formed during the Neogene Himalayan Movement.On the cliffs of Zhujiashan Hill and Niaoershan Hill in the southwest side of Lushan Mountain,you can see clear normal-fault stepwise extending lineation composed of fault strain quartz.In Xilinsi Temple,the upper block is composed of Paleogene red beds,and the lower block of Sinian siliceous rocks.It indicates that the normal fault was formed in the Neogene.
4.Hydrogeological features
1.Basic characteristics of groundwater system
(1)Porous water system in loose rocks
Phreatic water
The phreatic water in the Pleistocene moraine muddy boulder bed and terra jora bed is not sufficient for exploitation.Its flow amount of a single well is less than 1t/d.
The Holocene sand-gravel beds are distributed in the alluvial plains and major river valleys surrounding Lushan Mountain,the phreatic water sources are abundant,and the flow amount of a single well could be up to 100-1,000t/d or more.
Piestic water
There is an impermeable layer about 10m thick on the top of Holocene sand-gravel bed,the piestic water is formed,the flow amount of a single well could be up to 100-1,000t/d or more.The flow amount of a spring is about 300L/S.The water is the HCO3-Ca or HCO3-Ca(K+Na)type,the mineralization degree is 0.1-0.5g/l,with a pH value of 7-8.
(2)Solution water system in carbonates
Fissure and cave water in carbonates
The karst is relatively developed in the Carboniferous,Permian and Lower-Middle Triassic limestone,the underground runoff module is 3-6L/S.km2,the bipole value is 1.1-11.7L/S.km2;the flow amount of the spring is about 0.1-1.5L/S.The water is the HCO3-Ca type with a pH value of 7-8.The flow amount of a single well is between 10 to 9797.6t/d,the conditions for groundwater exploitation are simple and intermediate in this karst area.
Fissure and cave water in carbonates with clastics
The karst caves are not developed in the Middle-Upper Cambrian and Ordovician muddy limestone.The underground runoff module is 1.83-4.42L/S.km2,the flow amount of the spring is about 0.1-1.3L/S.The water is the HCO3-Ca type with a pH value of 6-8.The flow amount of a single well is between 10 to 885.29t/d,the conditions for groundwater exploitation are complex.
(3)Fissure water system in basement rocks
Structural fissure water
The groundwater system in the Precambrian metamorphic rock,granogneiss,and Nanhuan sandstone belongs to the structural fissure water,the underground runoff module is 2.8L/S.km2,the flow amount of the spring is about 0.01-0.2L/S.The water is the HCO3-Ca(K+Na)type with a pH value of 6-8.The mineralization degree is 0.1-0.5g/l.The conditions for groundwater exploitation are relatively complex.
The water system in the Sinian and Lower Cambrian shale and siliceous rocks is also the structural fissure water.The fissures are extremely developed in the siliceous rocks,the underground runoff module is greatly varied,between 1.17 to 6L/S.km2,the flow amount of the spring is 0.1-0.5L/S.The water is the HCO3-Ca or HCO3-Ca(K+Na)type with a pH value of 6-8.The mineralization degree is 0.1-0.3g/l.The flow amount of a single well would reach up sometimes to 1,200t/d.But the content of the poisonous elements As and U is usually over the potable standard.
Network fissure water in the weathered zones
The groundwater in the Lower Silurian shale and Cretaceous and Paleogene red beds,granite and volcanic rocks belongs to the network fissure water system.The underground runoff module is greatly varied,between 0.6 to 1.08L/S.km2,the flow amount of the spring is 0.01-0.5L/S.The water is the HCO3-Ca(K+Na)type with a pH value of 7-8.The flow amount of a single well would reach up to 2,200t/d only in the fissure solution caves of the Paleogene basal conglomerate.
2.Evolution of groundwater system
When there is an impermeable layer on the top of the aquiferous beds,the Holocene phreatic water would evolve to the piestic water,the deeper the groundwater buried,the bigger the waterhead pressure.
The flow amount of the karst water or karst fissure water depends on the cave interconnection and exposed elevation.During the evolutionary process,the isolated caves would gradually connect with each other,the more caves connected,the larger the groundwater amount.While the connected caves depress down to the place below the phreatic surface,the cave water is sufficient;on the contrast,if the crust would uplift,the water-bearing caves would become dry caves.When the piestic or phreatic water in the Holocene sand-gravel beds were connected with underground karst caves,we could get the maximum flow amount.
The fissure water in the basement rocks was basically stable during its evolutionary process,the increase of surface weathered fissures would have a little influence on the groundwater.When there would be some extending fault zones,these zones would be become the water-rich belts,the ascending springs would be occurred,its flow amount of a single spring would be up to 2,200t/d.
Since the Quaternary,the Lushan Mountain body has kept a slow uplifting,which controls the evolution of groundwater system in the geopark.