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&&&&The Tongziyan sedi- ments of tidal facies can be divided into four subfacies. 1. Muddy flat sub facies, which is chiefly composed of mudstones or sandy mud- stones, with horizontal bedding, trace fossils and bioturbate struc- tures.
&&&&其潮坪相沉积可以划分为:1泥坪相,由泥岩或砂质泥岩为主组成,具水平层理,分布有痕迹化石和动物扰动构造。
&&&&The Mesozoic terrigenous tempestite at Sankeyushu in Tonghua county is discovered, having the typical lag deposition bed, scour surface formed by windstorm, channel mold, horizontal bedding and dome-shaped bedding.
&&&&于通化三棵榆树等盆地发现的中生代陆相风暴岩具有较为典型的滞留层、风暴冲刷面、渠模、水平层理和丘状层理。
&&&&In the middle stage, withe the deepening of the sea water, horizontal bedding, deformation bedding and convolution bedding developed, suggesting a platform-marginal slope facies.
&&&&中期海水加深,发育了水平层理、变形层理及包卷层理等,近于台地边缘斜坡相。
&&&&Anshun formation dolomite can be divided into dolomitic breccia, dolomitic solution-collapse breccia,secondary birdeye pore dolomite, siliceous dolomite, argillaceous dolomite, micritic dolomite and dolomite with horizontal bedding and tent structure.
&&&&安顺组白云岩岩石类型有角砾状白云岩、溶塌角砾白云岩、纹层状白云岩、鸟眼状次生孔洞白云岩、硅质白云岩、泥质白云岩、水平层理白云岩和具帐蓬构造白云岩、泥晶白云岩、细晶～粗晶白云岩等。
&&&&In the sandstone and siltstone, the sedimentary structures of largemedium type slaty, trough and fishbone crossbedding, horizontal bedding, graded bedding and horizontal laminae are developed.
&&&&在砂岩及粉砂岩中，发育大—中型板状、槽状及鱼骨状交错层理、水平层理，粒序层理及水平纹层等沉积构造。 澄江组沉积主要由退积型基本层序构成，局部出露加积型层序。
Using the X-ray horizontal screw CT machine and the corresponding loading systems in the State Key Laboratory of Frozen Soil Engineering, the real-time CT uniaxial compression tests of two unsaturated jointed slate samples with different bedding distribution are conducted.
&&&&(2)采用冻土工程国家重点实验室X射线螺旋卧式CT机及岩土专用加载装置，进行了含水平层理和垂直层理锦屏水电站非饱和板岩试样的CT试验，从细观层次解释了板岩水平层理试样与垂直层理试样破坏模式不同的机理，对其损伤演化过程进行了阶段性划分；
&&&&Horizontal beddings were developed in high-grade oil shale whose oil yield usually are between 5%~8% and up to 12%.
&&&&富矿层中水平层理发育,含油率多为5%~8%,最高可达12%;
&&&&Flat bedding, wavy bedding and vermiglyph were often found in the shallow lake facies, and the log was usually straight or slight dentation.
&&&&其余地区则均为滨浅—半深湖相沉积。 滨浅湖相常发育水平层理、波状层理及虫迹，测井曲线形态较平直，常呈微齿状。
&&&&5. The lower member of Nantou Formation is the deposit of glacier-marine, the upper member is deposit of moraine.
&&&&7.灯影组沉积相下部浅海台地潮间—潮上带沉积:富含藻叠层石,钙球藻及少量藻丝体,泥—粉晶结构,水平层理为主,条纹状及网格状泥裂发育。
&&&&In the upper portion, the developed sericitic-calcareous phyllite with horizontal stratifications, which is present in the associated features of Bowma sequence A—E and is characterized by the environmental features, of allochthonous, shallow-water and autochthonous deep-water living things coexisting, was peculiarly occurring in turbidite sediment.
&&&&上部为具水平层理的绢云母钙质千枚岩,呈现出鲍玛层序A——E的组合特征,并具有浊流沉积特有的异地浅水生物与原地深水生物共存的环境特征;
查询“水平层理”译词为用户自定义的双语例句&&&&我想查看译文中含有：的双语例句
为了更好的帮助您理解掌握查询词或其译词在地道英语中的实际用法，我们为您准备了出自英文原文的大量英语例句，供您参考。&&&&&&&&&&&& Three of the fluvial reaches: upper, middle and lower, in the plains, 180 km in length, have been chosen for the study of recent sedimentation of the Futou River. We have analysed and studied sedimentary structure. grain-size, light and heavy mineral, and quartz surface texture of sediments in the main channel, longitudinal bar, point bar and natural levee respectively.All of the vertical sequences of the subfacies are the products of flood-dry stages. That is, during the flood stage, the beddings of the vertical... Three of the fluvial reaches: upper, middle and lower, in the plains, 180 km in length, have been chosen for the study of recent sedimentation of the Futou River. We have analysed and studied sedimentary structure. grain-size, light and heavy mineral, and quartz surface texture of sediments in the main channel, longitudinal bar, point bar and natural levee respectively.All of the vertical sequences of the subfacies are the products of flood-dry stages. That is, during the flood stage, the beddings of the vertical section of longitudinal bar are lagdeposits horizontal beddings which reflect upper flow regime, or large-scale cross tabular beddings and large-scale trough beddings from below. With the hydrodynamic dwindling, small-scale trough beddings, and undulate and parallel beddings appear.The total thickness of the longitudinal bar is about 1 m, the thickness of point bar being over 2 m.One of the fundamental methods adopted in this paper is grain-size analysis which can reflect the hydrodynamic condition during sedimentation. The research on grain-size suite in subfaces would be helpful to reconstruct the depositional environment of paleofluviation.Good results can be obtained if a mixed content of heavy mineral and light mineral is used to analyse fluvial deposits, and the subfacies can be divided on the basis of the percentage of hornblend, quartz and feldspar.Electrical scan on quartz surface is at the initial stage. but surely it will play a specific role in the days to come.在滹沱河平原段180公里范围内,选取上、中、下三个河段。对各段的主河道相、心滩相、边滩相及天然堤相分别进行了沉积构造、粒度结构、轻重矿物和石英表面结构的分析研究。各亚相垂向沉积层序是河流洪——枯水期水动力变化的产物。例如:洪水期心滩剖面自下而上层理表现为:滞留砂砾层中的低角度斜层理(5°～10°),高流态的平行层理或大型板状斜层理,大型槽状斜层理;随着水流的减弱,相继出现小型槽状斜层理及砂波交错层理、水平层理.心滩相整个沉积厚度为1.0米左右。边滩相剖面中层理表现为:洪水期由河床侧向运移而形成的滞留砂砾层中的低角度斜层理,大型槽状斜层理或多丛系大型交错层理,随着水流减弱,层理为小型槽状或小型板状,砂波交错层理及水平层理。边滩相的沉积厚度大于2.0米。粒度分析能反映沉积物沉积时的水动力条件。轻重矿物含量的组合分析效果较好,其中角闪石、石英、长石百分含量可作为划分本河流亚相的重要依据。通过扫描电子显微镜,研究各亚相石英颗粒表面结构的组合特征,可作为沉积环境分析的辅助标志。 The coal-bearing strata are of Upper Triassic ( T31 ) and Lower Jurassic (J1m) Age,consisting of medium-fine sandstones,siltstones and mudstones with interstratified thin beds of coal. Based on the grain size analysis,the log-probability curves of the sandstones are found to be of fluvial and saucer-lake types.In the coal measures are seen horizontal, ripple,large-size cross beddings,and parallel, massive beddings.They always make up specific vertical sequences. Abundant plant fossils are also found of tropical... The coal-bearing strata are of Upper Triassic ( T31 ) and Lower Jurassic (J1m) Age,consisting of medium-fine sandstones,siltstones and mudstones with interstratified thin beds of coal. Based on the grain size analysis,the log-probability curves of the sandstones are found to be of fluvial and saucer-lake types.In the coal measures are seen horizontal, ripple,large-size cross beddings,and parallel, massive beddings.They always make up specific vertical sequences. Abundant plant fossils are also found of tropical and subtropical flora.Facies analysis has showed that coal series are of fluvial and lacustrine deposits of terrestrial facies.The depositioaal types being alluvial fan, braided stream, meander stream,flood land, lake and bog land.The T31 group is mainly of lacustrine deposits, and the J1m group of fluvial deposits.Judging from the paleo-geo graphic environment and the paleotectonic framework of the district, the author considers that coal beds occurred chiefly in flood land bogs and saucer-lake bogs.The favourable coal forming district extended from Mount Shiluo and Mount Kun in Wuwei County to Mount Xiaohan in Zongyang County.含煤岩系为上三叠统(T_3l)及下侏罗统(J_1m),由中—细粒砂岩、粉砂岩、泥岩夹薄煤层组成。根据粒度分析结果,可知砂岩的粒度概率图主要属河流及浅湖型。煤系中见水平层理、沙纹层理、大型交错层理、平行层理及块状层理,它们常构成特定的垂向序列。煤系内产丰富的植物化石,属热带—亚热带植物群。 相分析表明:煤系属大陆河流及湖泊沉积,沉积类型有冲积扇、辫状河、曲流河、河漫滩、湖泊、沼泽等。T_3l以湖泊沉积为主,而J_1m则以河流相为主。 作者根据该区古构造格局及古地理环境指出,煤层主要产于河漫滩沼泽及浅湖沼泽中,聚煤有利地区在无为县石罗山、昆山至枞阳县小含山一带。 Ⅰ. Stratigaphic Summary
The Yangjiaping section in Shimen County is located in the northern border of Hunan Province. Geotectonically it lies on the northern limb of Dongshanfeng anticlinorium of the southern margin of Yangtze platform. In tthis section the Precambrian system is well developed, and the upper and lower boundaries, are well defined. I is stratigraphical sequence is continuous and the geological structure is simple, while a lot of stromato-lites, microfossils, and small shelly fossils can be collected... Ⅰ. Stratigaphic Summary
The Yangjiaping section in Shimen County is located in the northern border of Hunan Province. Geotectonically it lies on the northern limb of Dongshanfeng anticlinorium of the southern margin of Yangtze platform. In tthis section the Precambrian system is well developed, and the upper and lower boundaries, are well defined. I is stratigraphical sequence is continuous and the geological structure is simple, while a lot of stromato-lites, microfossils, and small shelly fossils can be collected in this section. The total thickness is 1193. 34m.
This section can be divided as follows:
O lower cambrian Yangjiaping Formation
Conformity
Upper Sinian Dengying Formaton 176. 44m. in thickness.
Upper Member, greyish white, lightgrey midium to thick bedded micro-litic dolomite, Clastic dolomite silicified muddy clastic dolomite, Sparry clastic dolomite. 69. 67m.
Lower Member, dark grey thin-midium bedded microlitic dolomite, Siliceous dolomite, calcareous dolomite. 106. 77m.
Conformity
Upper Sinian Doushantuo Formation 475. 68m.
Upper M grey, greyish-white midium thick micro-granular clastic dolomite, phosphoric calcium-bearing dolomite, intercalated with a few dolomitic limestone, phosphorite. 84. 53m.
Lower M greyish black thin bedded micrite micro-granular car-bonaceous dolomite, dolomitic limestone, calcareous dolomite and a few pelitic siltstone, sandstone, carbonaceous slaty shale. 391. 15m.
Conformity
Lower Sinian Nantou Formation 719. 77m.
Upper M grey massive morainic arenaceous mudstone, gompho- lite and siltstone with morainic pebbles. 68. 24m.
Lower M dark grey massive arenaceous mudstone with mora-inic pebbles and a few pebbles-bearing sandstone intercalcated with slaty shale. 11. 53m.
Conformity
Lower Sinian Xiangmeng Formation 11. 93m.
Dark-grey, greyish black slaty shale, carbonaceous slaty shale, Mn-bearing slaty shale intercalated with lens of dolomite.
Conformity
Lower Sinian Dongshanfeng Formaton 3. 7m.
Dark-grey massive arenaceous slate with morainie pebbles, pebbles-bearing sandstone.
Disconformity
(Xuefeng movement)
Presinian Banxi Group Xieshuihe Formation 260. 07m.
Upper M purplish red, greyish green thick bedded medium-coarse granular slight metamorphic feldspathic quartz-sandstone, quartzose-sand-stone, siltstone, arenaceous slate and slate. 97. 60m.
Lower M purplish red, greyish white quartzose conglomerate, arenaceous conglomerate, pebbles-bearing sandstone, coarse granular qu-artz-sandstone intercalated with a few quartz-siltstone and slate.
Conformity
Presinian Banxi Group Madiyi Formation 175. 50m.
Upper M purplish red, greyish green medium-thick bedded sli-ght metamorphic medium-fine granular quartz-sandstone, rudaceous sand-stone, siltstone.slate etc. 159. 37m.
Lower M purplish red thick bedded massive slight metamorphic quartzose conglomerate, arenaceous conglomerate, pebbles-bearing sands-tone, coarse sandstone intercalated with a few arenaceous slate.
Unconformity
(Wuling movement)
U presinian Lengjiaxi Group. Ⅱ. Geochemical characteristics of rocks The geochemical characteristics of rocks of precambrian system in Yangjiaping section may be mentioned as follows: 1. Si. Al. Ca. Mg. K. Na. Fe. being the pretty high content chemi-cal elements, may be further subdivided into four assemblages, i. e. Al. Ti. B. Fe. Mn; Si. K. Ba. Cu. Pb; Ca. Mg. Na. P. Sr; and Cr. Ni Co. V. Zn.
2. Elements with closely correlative relationships are: Mn-B-Al-Ti; Sr-P-Ca-Mg; Cr-Ni-V; and Ba-Cu-Pb.
3. Variables of CaO-MgO and TiO_2-Fe_2O_3-K_2O-Al_2O_3-Na_2O respecti-vely control the carbonate rocks and the silicate rocks and both of them are in reverse relation which have been throughout the course proved by the mathematical method of factor analysis.
4. The result of the cluster analysis shows that the Fe_2O_3-Al_2O_3-K_2O- TiO_2-Na_2O can be clustered together, and represents the clay-rock, siltsto-ne and sandstone with pretty high content of the feldspar, while the FeO and MnO can be clustered together and represents the carbonate rocks.
Ⅲ. Palaeomagnetic characteristics of rocks
The palaeomagnetic characteristics of upper precarmbrian system at Yangjiaping section are as follows:
1. During the time of sedimentation of Precambrian rocks the palaeo-magnetism was basically located in the normal polarity epoch. The average palaeolatitude of Madiyi Formation, Xieshuihe Formation, Dongshanfeng Formation, Xiangmeng Formation, Nantuo Formation, Doushantuo Forma-tion and Dengying Formation were 30.49°, 19.93°, 12.25°, 23.32°, 9.84°, -20.20°, -19.46°, respectively.
2. There were three times of polar reversion during the deposition of precambrian rocks. One of the three times happened at the base of Cam-brian, and it may be served the proof of the boundary of Sinian and cam-brian systems, the other two occured in Madiyi Formation of Banxi Group and its cause of formation needs further research.
3. By comparing Upper precambrian Apw path at Yangjiaping section with that of Yangtze gorges, an Upper Precambrian Apw path at studied area has preliminaryly been set up.
Ⅳ. Palaeontological characteristics
There are chiefly micropaleoflora, stromatolites, and a few trace fossils in the Precambrian system of Yangjiaping section, the micropaleoflora may be subdivided into two assemblages:
Banxi group-lower Sinian system consists of the first assemblage, They belong to unicellular alage Sphaeromorphitae (being the dominant eleme-nts) and numerous fragments of brown algae, among them, the sphaerical forms are dominant, and fibre fragments are secondary, and a few triangu-lar, quadrate or irregular forms, the diameters of most individuals are large than 50μ with coarse surfaces and simple-complicated ornament. The second assemblage consists of the micropaleoflora of Upper Sinian system, presenting acantomorphitae and a few elements of new genera and
species of prismatomorphitae and Lophosphaeridium yichangense, Hubeis- phaera sp., which have never been seen in the first assemblage.
The stromatolites are distributed in Doushantuo Formation and Dengy-ing Formation. In these formatio Nucleelo f., Boxonia f., Gymnosolen f., Baicalia f., etc. are dominant.
The trace fossils consist of some irregular tubular bodies.
V. Paleoglaciers
The glacier periods of early Sinian may further be subdivided into two subglacier periods and an inter-glacier period. The Nantuo Formation is typical sedimentary type of morainic facies. The Xiangmeng Formation is the deposits of Xiangmeng inter glacier Period. The Dongshanfeng form-ation is pretty typical sedimentary type of glaciomarine facies. The Com-mon characteristics of the two types of glacier sediments are as follo-ws.
1. The contents of moraine are complicate but the main compositions are basically identical.
2. The shapes of pebbles are various but the chief outlines, Sphericiti-es and roundnesses are similar.
3. The uneven distribution, different sizes, random arrangements, great changes in longitudinal distribution and without definite rules are characters of pebbles.
4. The Striae, carve-traces, pressed crevasses, pressed pit., slide tra-cks and grinding pebbles are all present.
The differences of the two types of the glacier sediments are:
1. The thickness of glacier marine deposit is rather stable and with a few intercalated beds that reveals the characteristics of marine deposit. but the thickness of morainic facies deposit varies greatly, intercalated beds almost absent, bedding also invisible.
2. There are litlle quantities of pebbles in glaciermarine deposit and with few boulders, ice slide tracks and grinding pebbles. The falling stone structures are well developed. On the contrary, the pebbles of morainic facies are very much with a definite of boulders. The ice slide tracks and grinding pebbles are generally seen, without falling stone-structures.
Ⅵ. Sedimentary facies
1. The lower member of madiyi Formation is of meanderring river de-posit, and the upper member is of tidal flat deposit of river mouth gulf.
2. The lower member of Xieshuihe Formation is of the deposit of braided river, The upper member is of tidal flat deposit of river mouth gulf.
3. The Dongshanfeng Formation is the deposit of glacialmarine.
4. The Xiangmeng Formation is the deposit of subtidal gulf.
5. The lower member of Nantou Formation is the deposit of glacier-marine, the upper member is deposit of moraine.
6. The lower member of Doushantuo Formation represents the deposit of subtidal basin, the upper member is the deposit of subtidal flat carbo-nate rock.
7. The lower part of Dengying Formation represents the deposit of subtidal half closed flat shallow beach and interbeach, the upper member is the deposit of subtidal flat margin gradient.
Based on the characteristics of isotopic age data, paleontology, crustal movement, and paleoglacier, the Precambrian System may be correlated as follows:
The Yangjiaping Formation rich in small shelly fossils is the equivale-nce of Tianzhushan Formation in east of the Yangtze Gorges, the Meishu-cun Formation in eastern Yunnan, the Maidiping Formation in Sichu-an.
The upper morainic Nantou formation may be correlated with Nantou formation in Yunnan and in east of the Yangtze Gorges, Silikou Forma-tion North of Guangsi, Leigongwu Formation in Western Zejiang and Nor-theast of Jiangsi.
The lower Morainic Dongshanfeng Formation is the equivalence of Gucheng Formation in Changyang, Hubei, the Changan Formation-lover Member of Fulu Formation in eastern Guizhou and Guangsi.
The Xueshuihe Formation is suitable to be correlated with the Liantuo Formation east of the Yangtze Gorges, the Qingshuijiang Formation-Rongli Formation east of Guizhou, Gongdong Formation, north, of Guangsi, Kaiji-anqiao formation in southwestern Sichuan. The Madiyi Formation may be correlated with Jialu Formation, Fan-shao Formation of eastern Guizhou. Baizhu Formation, Hetong Formation of Northern Guangsi. the Suxiong Formation of southwestern Sichuan.
The Lengjiaxi Group may be correlated with the Fanjingshan group of eastern Guizhou, the Sibao group of Northern Guangsi, the Kunyang group of eastern Yunnan, the Ebian group of southwestern Sichuan, the Sandouping group of the eastern Yangtze Gorges.一、地层剖面剖面全长2公里,出露较好,构造简单,层序连续完整,顶、底界接触关系清晰,产较丰富的微古植物、叠层石、小壳动物等古生物化石,可分一群、一系、两统、七组。地层总厚度为1193.34米。自上而下分为: 上覆地层:下寒武统杨家坪组黑色炭质页岩与薄层硅质岩互层。整合震旦系灯影组 176.44米上部:由灰白色、浅灰色中—厚层粉晶云岩、粒屑云岩、硅化泥晶云岩、亮晶粒屑云岩等组成。 69.67米下部:由深灰色薄—中厚层泥—粉晶云岩、硅质云岩、灰质云岩等组成。 106.77米整合陡山沱组 475.68米上部:由灰色、灰白色中—厚层状粉晶粒屑含灰质云岩、含磷质云岩、含硅质云岩夹少量白云质灰岩、磷块岩等组成。 84.53米下部:由灰黑色薄层泥晶—粉晶炭质云岩、白云质灰岩、灰质云岩及少量泥质粉砂岩、砂岩、炭质板状页岩等组成。 391.15米整合南沱组 90.02米上部:由冰碛砾砂质泥岩、冰碛砾泥岩及冰碛砾粉砂岩等组成。 78.49米下部:由深灰色冰碛砾砂质板岩、冰碛砾板岩及少许冰碛砾砂岩、板状页岩等组成。 11.53米整合湘锰组:由深灰色、灰黑色板状页岩、炭质板状页岩、含锰板状页岩及夹白云岩透镜体等组成。 11.93米整...一、地层剖面剖面全长2公里,出露较好,构造简单,层序连续完整,顶、底界接触关系清晰,产较丰富的微古植物、叠层石、小壳动物等古生物化石,可分一群、一系、两统、七组。地层总厚度为1193.34米。自上而下分为: 上覆地层:下寒武统杨家坪组黑色炭质页岩与薄层硅质岩互层。整合震旦系灯影组 176.44米上部:由灰白色、浅灰色中—厚层粉晶云岩、粒屑云岩、硅化泥晶云岩、亮晶粒屑云岩等组成。 69.67米下部:由深灰色薄—中厚层泥—粉晶云岩、硅质云岩、灰质云岩等组成。 106.77米整合陡山沱组 475.68米上部:由灰色、灰白色中—厚层状粉晶粒屑含灰质云岩、含磷质云岩、含硅质云岩夹少量白云质灰岩、磷块岩等组成。 84.53米下部:由灰黑色薄层泥晶—粉晶炭质云岩、白云质灰岩、灰质云岩及少量泥质粉砂岩、砂岩、炭质板状页岩等组成。 391.15米整合南沱组 90.02米上部:由冰碛砾砂质泥岩、冰碛砾泥岩及冰碛砾粉砂岩等组成。 78.49米下部:由深灰色冰碛砾砂质板岩、冰碛砾板岩及少许冰碛砾砂岩、板状页岩等组成。 11.53米整合湘锰组:由深灰色、灰黑色板状页岩、炭质板状页岩、含锰板状页岩及夹白云岩透镜体等组成。 11.93米整合东山峰组:由深灰色、灰色块状含冰碛砾石砂质板岩、含冰碛砾石砂岩等组成。3.70米假整合板溪群渫水河组 260.10米上段:由紫红色、灰绿色粗—细粒浅变质长石石英砂岩、石英砂岩、粉砂岩、砂质板岩、板岩等组成。 97.60米下段:由紫红色、灰白色厚层—块状变质石英砾岩、砂砾岩、含砾砂岩、粗粒石英砂岩夹少量石英粉砂岩、板岩等组成。 162.47米整合马底驿组 175.50米上段:由紫红色、灰绿色中—厚层状浅变质中—细粒石英砂岩、长石石英砂岩、含云母砂岩、粉砂岩、板岩等组成。 159.37米下段:由紫红色厚层—块状变质石英砾岩、砂砾岩、含砾砂岩、石英粗砂岩夹少量砂质板岩等组成。 16.13米不整合下伏地层:冷家溪群变质砂岩、板岩互层。二、岩石地球化学据1395个岩石光谱样、47个化学样的分析数据,用因子分析、聚类分析研究了各类岩石地球化学分类、元素间相关关系;用有序地质体最优分割法及对分移动窗口法研究了剖面上层序的划分。初步掌握了该剖面地球化学特征如下: 1.平均化学成分以Si、Al、Ca、Mg、K、Na、Fe为主,可划归A1、Ti、B、Fe、Mn;Si、K、Ba、Cu、Pb;Ca、Mg、Na、P、Sr;Cr、Ni、Co、V、Zn等组合。 2.元素相关关系较密切的有Mn-B-A1-Ti;Sr-P-Ca-Mg;Cr-Ni-V;Ba-Cu-Pb等,其中尤以Si、P、Ca、Mg关系密切。 3.元素丰度在时间上的演化规律与剖面上地层划分基本上相吻合。 4.因子分析表明变量CaO—MgO控制碳酸盐岩;变量TiO_2—Fe_2O_3—K_2O—A1_2O_3—Na_2O控制硅酸盐岩,且两者始终保持反间关系。 5.聚类分析表明Fe_2O_3、Al_2O_3、K_2O、TiO_2、Na_2O聚类一起,代表了粘土岩、粉砂岩、含长石较高的砂岩类;FeO、MnO聚集一起,反映了还原条件下形成的岩石;CaO、MgO聚类一起,代表了碳酸盐岩类岩石。三、古地磁据30个样品的磁测数据,获得了磁性地层的初步成果如下: 1.晚前寒武纪沉积期,基本上处于正极性时期,同时均处于低纬度地带,其中马底驿组平均古纬度为30.49°,渫水河组为19.93°,东山峰组为12.25°,湘锰组为23.32°,南沱组为9.84°,陡山沱组为-20.20°,灯影组为-19.46°。 2.晚前寒武纪沉积期,经历了三次极性倒转,其中寒武系底部求得的北磁极落在南半球的东经62.72°,南纬8.67°,该次极性倒转可作为震旦系与寒武系分界的佐证。另两次极性倒转发生在马底驿组沉积期内,其成因尚待进一步研究解释。 3.视古地磁极迁移轨迹表明,距今1000百万年前冷家溪群开始,地磁极位置从163.42°东、65.42°北起向西北方向迁移;板溪群时期,则在北极点附近绕动,而后向北西方向迁移;震旦纪时,磁极位置由早—晚,由5.65°—327.60°东、47.05°—39.00°北之间绕动。由于经验不够,又因受仪器设备限制,精度尚待进一步深化。但作为资料积累,对建立南方晚前寒武纪古地磁年表无疑将是有益的。四、古生物主要为微古植物、叠层石及一些虫迹化石。微古植物可建立两个组合:板溪群—下震旦统中微古植物为第一组合,是以球藻亚群为主的单细胞藻类及一些褐藻碎片,形态多为球形,其次为纤维状碎片,少数为三角形、方形及不规则形状,多数个体大于50微米,表面粗糙,有简单—复杂的纹饰。该组合近似蓟县青白口系及峡东莲沱组—南沱组中微古植物特征。上震旦统微古植物为第二组合,它除了继承下震旦统及板溪群中微古植物的许多分子外,更重要的是出现了刺球藻亚群及棱面藻亚群中少数分子及前所未见的Lophosphaerium yichangense, Hubeisphaera sp.等新属新种。该组合和南方各地上震旦统微古植物特征基本一致。叠层石产于陡山沱组及灯影组,主要为Nucleela f., Boxonia f., Gymnosolen f., Baicalia f. 等。虫迹化石较普遍,主要为一些不规则形管状体。五、古冰川统称早震旦世冰期,可进一步划分两亚冰期及一间冰期。南沱组代表南沱亚冰期沉积,为较典型的冰碛相沉积类型;湘锰组代表湘锰间冰期沉积;东山峰组代表江口组亚冰期沉积,为较典型的冰海沉积类型。两种沉积类型具有如下的共性: 1.冰碛物成分复杂,随地而异,但砾石的主要组分基本相同。 2.砾石的形状多种多样,但主要形态、球度及圆度相近似。 3.砾石分布不均匀,大小不一,排列杂乱,在纵向分布上,变化急剧,无一定规律。 4.均具有条痕、刻痕、压裂、压坑等冰溜遗痕及研磨砾石。上述共性说明冰海相与冰碛相有相近的亲缘关系。两种沉积类型有如下差别: 1.冰海相沉积厚度较稳定,具有少量夹层,其层理显示海相沉积特征;冰碛相沉积厚度变化大,几乎无夹层,不显层理。 2.冰海相沉积砾石数量少,大砾石少,冰溜遗痕及研磨砾石少见,落石构造非常普遍;冰碛相沉积砾石数量多,有一定数量大砾石,冰溜遗痕及研磨砾石普见,无落石构造。上述差异的原因,主要与冰川进入海洋的部位有关。六、沉积相共划分了3相组、4相、7亚相、16微相及62相段: 1.马底驿组沉积相下段曲流河沉积:结构成熟度低,杂基—颗粒支撑,板状及平行层理为主,剖面二元结构明显,粒度分析多数样品落在河流范畴。上段河口湾潮坪沉积:结构成熟度低,楔状、槽状、脉状再作用面、人字形等层理及波痕、泥裂大量出现,薄互层发育,粒度分析多数样品落在海(湖)滩范畴,部分样品落在河流范畴。 2.渫水河组沉积相下段辫状河流沉积:矿物及结构成熟度均较低,颗粒支撑为主,大型楔状、槽状交错层理发育,剖面二元结构发育不全,绝大多数样品落在费里德曼标准偏差散点图河流范畴。上段河口湾潮坪沉积:结构成熟度较低,杂基支撑,楔状、槽状、爬升、脉状、鱼骨状等层理及波痕、泥裂普见,薄互层发育,粒度分析结果,样品一半落在海洋,另一半落在河流范畴。 3.东山峰组冰海相沉积:矿物及结构成熟度低,杂基支撑,具微层理,落石构造发育,粒度分析参数值反映为中值,变化范围大,峰态及标准偏差变化范围小,偏度全为负偏。 4.湘锰组河口湾潮下海湾沉积:富含有机质、藻类及硫化物,常夹含锰碳酸盐岩及锰矿层,细纹状水平层理发育。 5.南沱组沉积相下段与东山峰组沉积相类似,为冰海相沉积,上段为冰碛相沉积。矿物及结构成熟度低,杂基支撑,不显层理,冰溜遗痕及研磨砾石普见,粒度参数值反映峰态中等—尖窄,偏度为极负偏。 6.陡山沱组沉积相下部浅海台地潮上—潮间—潮上带沉积:富含有机质、藻类及硫化物,岩石化学成分中Fe~(3+)/Fe~(2+) <1,微量元素Rb/K=0.0037,水平层理发育。上部浅海台地碳酸盐岩潮坪沉积:富含藻叠层石,岩石化学成分Fe~(3+)/Fe~(2+)<1,Rb/K=15.30,平行层理为主,局部有小—中型楔状交错层理。 7.灯影组沉积相下部浅海台地潮间—潮上带沉积:富含藻叠层石,钙球藻及少量藻丝体,泥—粉晶结构,水平层理为主,条纹状及网格状泥裂发育。上部浅海台地潮间—缘斜坡—盆地边缘:富含大型柱状叠层石,常见圆形或椭圆形、竹叶状砂屑、砾屑,具有大型滑动构造及包卷层理。七、划分与对比 (一)划分 1.震旦系与寒武系界线(顶界) 分界的主要依据为小壳动物群,已于188层炭质页岩与薄层硅质岩中发现:Protohertzina sp., P. unguliformis, P. anabarica, Turcutheca sp., Torellella sp. 等,此外尚见Oxe-aklostera monaxon等海绵骨针、微型海绵骨针及分类位置尚存疑的蚕形、球形类化石,其中Protohertzina sp., 为钱逸建立的早寒武世早期小壳化石带第一组合中的分子。其二,同时于188—190层中发现极为丰富的微古生物化石,计有蓝藻门、绿藻门、红藻门、细菌、疑源类及分类位置不明的藻微化石,共18属、19种(内3个新属、9个新种、9个未定种、2个未命名化石),它们保存好,属种类型复杂,除少数分子分别见于云南、四川下寒武统梅树村组、麦地坪组外,多数分子亦为首次发现,是国内已发现的相当层位微化石最特殊的类型,且与震旦系上统的微古化石组合有明显差异。其三,在震旦系顶部(187层)云岩中发现有虫管化石。综上三者依据对湖南湘西北地区震旦系与寒武系界线的划分和对比进行了论述,并将其界线置于产小壳化石的188层之底部。 2.板溪群与冷家溪群界线(底界) 界线置于1与0_2层之间,划分的主要依据为: (1)板溪群与冷家溪群呈高角度不整合接触,为一理想界面。 (2)冷家溪群为复理石建造,板溪群为类磨拉石建造。 (3)B、P、K、Cr、V、Sr等元素在冷家溪群顶部出现低值,进入板溪群后则出现高值。 (4)冷家溪群多数分子为一些形状简单、个体微小、膜壳较薄、表面光滑的球形藻类。板溪群多数分子则为形状较复杂、个体较大、膜壳较厚、表面具纹饰的藻类。 3.震旦系与板溪群界线界线置于102与103层之间,主要依据为古气候标志,即将冰成地层置于震旦系底部,这种意见的理由为: (1)早震旦世冰成地层遍布五大洲,便于世界对比。 (2)峡东震旦系经历了两次构造运动,缺失不少地层,如以冰成地层为底界,可摈除其中较大的一次构造运动的影响。 (3)如以莲沱组为底界,震旦纪时限大于2亿年,如从冰成地层开始,震旦纪时限小于1.5亿年,更符合建立新纪的时限要求。 (二)对比对比的依据主要是同位素、古生物及构造运动、古冰川,其次可考虑沉积建造、变质程度、岩性组合等因素。据此可作如&nbsp&&&&&相关查询
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