1984 Vol. 2, No. 1
column
Display Method:
1984, 2(1): 1-17.
Abstract:
The main reservoir sandstones in the Maling oil field and its periphery in ShanXi-Gansu-Ningxia Basin, Northwest China-Yan-10 sandstones of lower Jurassic(including Fuxian formation)are referred to as confined valley fill deposits.The difference of mineral compositions of the sandstone bodies deposited in different paleochannel systems leads to the different processes of diagenesis and then results in the difference of pore textures and reservoir properties of sandstones thus formed.Mechanical compaction during the immature period of mesodiagenesis seriously damages the primary intergranular pores of sandstones with more flexiblecomponents，but only slightly hits the interg pores in the quartzose sandstones.Cementation subsequent to the compaction usually and more easily occurs in the quartzose sandstone but not in the sandstone with more flexible clastics.when these two kinds of sands tones have undergone the process of diagenesis of different charactersaad reduced their porosity to the same level.the pore-throat and the permeability of quarizose sand-stones would be much larger than those of other sandstones because the intergranular pores in the former are still better developed.Secondary enlargement of quartz would destroy the homogeneity of primary pores and pore-throats of sandstones.Secondary solution porosity of subsurface origin improves the reservoir properties of Yan-10 sandstones.The differential of authigenic minerals and asphalts in sandstone bodies create the trapping conditions updip to the east of the South Area 1 in the Maling Oil field as well as the low permeability zone bordering the oil pool between the Middle and North Areas of the Field. The effects of clay miaerals of different origin and their diagenesis on reservoir property of sandstones and on oil and watersaturation and electric response of the reservoir rocks different.And the effect of illite is far greater than that of the authigenic kaolinite.
The main reservoir sandstones in the Maling oil field and its periphery in ShanXi-Gansu-Ningxia Basin, Northwest China-Yan-10 sandstones of lower Jurassic(including Fuxian formation)are referred to as confined valley fill deposits.The difference of mineral compositions of the sandstone bodies deposited in different paleochannel systems leads to the different processes of diagenesis and then results in the difference of pore textures and reservoir properties of sandstones thus formed.Mechanical compaction during the immature period of mesodiagenesis seriously damages the primary intergranular pores of sandstones with more flexiblecomponents，but only slightly hits the interg pores in the quartzose sandstones.Cementation subsequent to the compaction usually and more easily occurs in the quartzose sandstone but not in the sandstone with more flexible clastics.when these two kinds of sands tones have undergone the process of diagenesis of different charactersaad reduced their porosity to the same level.the pore-throat and the permeability of quarizose sand-stones would be much larger than those of other sandstones because the intergranular pores in the former are still better developed.Secondary enlargement of quartz would destroy the homogeneity of primary pores and pore-throats of sandstones.Secondary solution porosity of subsurface origin improves the reservoir properties of Yan-10 sandstones.The differential of authigenic minerals and asphalts in sandstone bodies create the trapping conditions updip to the east of the South Area 1 in the Maling Oil field as well as the low permeability zone bordering the oil pool between the Middle and North Areas of the Field. The effects of clay miaerals of different origin and their diagenesis on reservoir property of sandstones and on oil and watersaturation and electric response of the reservoir rocks different.And the effect of illite is far greater than that of the authigenic kaolinite.
1984, 2(1): 29-43.
Abstract:
This paper describes a process including: extraction of metalloporphyrins from sediments with 9:1(v/v)benzene and methanol mieture，separation using column chromatography,and purification using Thin Layer chromatography. The metallopor-phyrins were identified by- means of h1S, computer sy-stem.The results of this study-indicate the presence of two series of metalloporphv-tins, i. e. Ni-ETIO(or vo-ETIO)and Ni-DPEP(or vo一OPEP)in geologic samples. Average molecular weight and ranges of the two series of metalloporphytins, homologous compound ratios,skewness and band width of MS spectrum peaks for each of the serieswere calculated.The significance of these parameters in petroleum geochemistry is also discussed in detail.This paper also presents a useful method for mass spectrometric identi-fication of metalloporphytins.The authors believe that the geochemical significance of these parameters is as follows:(1)The significance of nickel and vanady-1 porphyrins on sedimentary facies:According to the analytical result，the porphyrins from the marine carbonate source rocks of southern China are mainly- composed of vanadyl porphyrin,and no nickel porphyrin is detected.While the samples recognized geologically as continental facies are mainly composed of nickel porphy-rin, and no vanady-1 porphyrin is detected.In addition, vanady1 porphyrin has a much broader range of molecular weight than nickel porphyrin.Thus，different porphyrins can be used as indicators of sedimentary facies.(2)The maturity- and evolution of organic matter:In geological body，the degree of transformation of the porphyrins from deoxophylloerythroetioporphyrin( DPEP) to etioporphyrin(ETIO)is proportiuual to heat history，temprcture, pressure and time.Therefore，We can use series ratio, i.e.ΣIDPEP, ΣIETIO ratio, to reflect the mat:rity of organic matter.hor example, the series ratio for sample 1 is 1.24,that for sample 2 is 3.09.Sample 3 comes from the depth interval of 1615一1686m with immature hydrocarbons, while Sample 4 comes from the depth of 2200m with mature hydrocarbons.Their series ratios are 9.06 and 3.96 respectively.Furthermore.the molecular weight of the porphyrin and the relative content of low carbon numberporphyin also show a tendency relating to the heat evolution regularity of organicmatter.(3)Skewness of metalloporphyrins: fable 3 shows that sample 3 is an imma-Lure source rock, its skewness of ETIO series is negative, other samples are all positive for the ETIO series，and the skewness of DPEP series is all negative.Therefore，the polarity and value of skewness can be used as evolution and maturity-indicators to point out the evolutional tendency.(4)bass spectrometry of metalloporphyrin shows that the peak on the mass spectrogram is carbon number C32 and that the chlorophylla being converted into DPEP is also carbon C32.It is suggested that chlorophylla may be postulated as petro-porphyrin precursor.(5)Quantitative mass spectrometric analysis of metalloporphyrins can precisely provide the average molecular weight of porphyrins.Thus when porphyrins is quantified with UV一VIS spectrophotometer, the content of porphyrin can be calculated more correctly，if the data obtained from mass spectrometry are used。
This paper describes a process including: extraction of metalloporphyrins from sediments with 9:1(v/v)benzene and methanol mieture，separation using column chromatography,and purification using Thin Layer chromatography. The metallopor-phyrins were identified by- means of h1S, computer sy-stem.The results of this study-indicate the presence of two series of metalloporphv-tins, i. e. Ni-ETIO(or vo-ETIO)and Ni-DPEP(or vo一OPEP)in geologic samples. Average molecular weight and ranges of the two series of metalloporphytins, homologous compound ratios,skewness and band width of MS spectrum peaks for each of the serieswere calculated.The significance of these parameters in petroleum geochemistry is also discussed in detail.This paper also presents a useful method for mass spectrometric identi-fication of metalloporphytins.The authors believe that the geochemical significance of these parameters is as follows:(1)The significance of nickel and vanady-1 porphyrins on sedimentary facies:According to the analytical result，the porphyrins from the marine carbonate source rocks of southern China are mainly- composed of vanadyl porphyrin,and no nickel porphyrin is detected.While the samples recognized geologically as continental facies are mainly composed of nickel porphy-rin, and no vanady-1 porphyrin is detected.In addition, vanady1 porphyrin has a much broader range of molecular weight than nickel porphyrin.Thus，different porphyrins can be used as indicators of sedimentary facies.(2)The maturity- and evolution of organic matter:In geological body，the degree of transformation of the porphyrins from deoxophylloerythroetioporphyrin( DPEP) to etioporphyrin(ETIO)is proportiuual to heat history，temprcture, pressure and time.Therefore，We can use series ratio, i.e.ΣIDPEP, ΣIETIO ratio, to reflect the mat:rity of organic matter.hor example, the series ratio for sample 1 is 1.24,that for sample 2 is 3.09.Sample 3 comes from the depth interval of 1615一1686m with immature hydrocarbons, while Sample 4 comes from the depth of 2200m with mature hydrocarbons.Their series ratios are 9.06 and 3.96 respectively.Furthermore.the molecular weight of the porphyrin and the relative content of low carbon numberporphyin also show a tendency relating to the heat evolution regularity of organicmatter.(3)Skewness of metalloporphyrins: fable 3 shows that sample 3 is an imma-Lure source rock, its skewness of ETIO series is negative, other samples are all positive for the ETIO series，and the skewness of DPEP series is all negative.Therefore，the polarity and value of skewness can be used as evolution and maturity-indicators to point out the evolutional tendency.(4)bass spectrometry of metalloporphyrin shows that the peak on the mass spectrogram is carbon number C32 and that the chlorophylla being converted into DPEP is also carbon C32.It is suggested that chlorophylla may be postulated as petro-porphyrin precursor.(5)Quantitative mass spectrometric analysis of metalloporphyrins can precisely provide the average molecular weight of porphyrins.Thus when porphyrins is quantified with UV一VIS spectrophotometer, the content of porphyrin can be calculated more correctly，if the data obtained from mass spectrometry are used。
1984, 2(1): 53-64.
Abstract:
The pyrite ore deposit discovered in Hunan Province in recent years is a medium scale sedimentary deposit.Its ore-bearing strata are the laiziqiao Formations of the Middle Devonian Series.In this region, the Devonian system possesses two petrographical division and marl division，and this mine belongs to the latter.In this division, the Qiziqiao Formation can be divided into four lithological sections.The ore-bearing section is situated at the top(the fourth section)，and is composed of thin beded,dark grey- siliceous rock, siliceous banded limestone and carbonaceous and pelitic limestone，about 20-60m thick.The ore beds are stratiform,stratoid and Tense-like with a thickness of 0.4一31m and conformably deposited the strata in synchronous fold.It extends in NE direction, and the thickness of its northern part is greater than that of the southern one.The ore is composed of pyrite w ith framboids texture.lts struc-ture is massive, closely banded, and sparsely banded.A number of Tentaculite fossila still retained in the ore rock.The rate of Co/Ni in the single mineral of pyrite is 0.01.The composition of sulfur isotope is rich in S32, its variation range is from-17.4 to -28.0‰. and its average is -23.7‰. In the upper and lower ore beds the values of the δS34 are stable.Along the strike of the ore body, the value of the δS34 is also even, but from east to west it decreases from -20 to -27‰ in the dip.In this region, the Devonian system was the first sedimentary covering strata after the Caledonian Movement.In the early stage of Qiziqiao, the whole region was in the open shallow sea environment, and in the middle and late stages, the large rift emerging in NE direction in the Caledonian Movement began to revive.And then,the landform of the sedimentary region presented the relief in alternat-ing high and lov- parallel to the NE direction.The high division formed the half-li-mited and limited regions of carbonate platform，and the low division w-as the region of deep water basin.The rock type.chemical composition.teaiure and structure.organic assemblage and ecological characteristics of the sediments were distinctly different in various sedimentary regions.Particularlt，in the late stage of Qiziqiao.the basin was completely situated in the environment of deep water.low grade energy and lacking of oxygen. The characteristics of the sediments were very similar to those of the Craton basin carbonate zone described by J，L.Wilson(1975)，but these basins appeared within the platform and developed in a short time.Their forms mostly occurred in the narrow and linear structure which related to the specific teotonic setting in southern C hina.Therefore，they are specially called intraplatform linear basins.The palaeogeographical site of Putou pyrite ore deposit appeared at the eastern margin of the basin in the extension of NE direction.The sedimentary environment of Putou pyrite deposit was in the deep water basin lacking of om gen, and the supplies of organic m atter and ferriginous m ateri-als were comparatively- sufficient.T he relief difference caused the existence of bioherm was not compensated it that time. Therefore, the relative strong retarding environ went appeared in the west side of the reef body，which was more favoura-ble for the concentration of the ore forming material and the organic matter.The study of sulf ur isotope of the mine has proved that the sulphates in marine water were continuously replenished to the sedimentary strata in the open condition.In the dia-genesis stage, the ore beds of pyrite, with well一developed horizontal laminated structure of large thickness and rich in S32, were formed。
The pyrite ore deposit discovered in Hunan Province in recent years is a medium scale sedimentary deposit.Its ore-bearing strata are the laiziqiao Formations of the Middle Devonian Series.In this region, the Devonian system possesses two petrographical division and marl division，and this mine belongs to the latter.In this division, the Qiziqiao Formation can be divided into four lithological sections.The ore-bearing section is situated at the top(the fourth section)，and is composed of thin beded,dark grey- siliceous rock, siliceous banded limestone and carbonaceous and pelitic limestone，about 20-60m thick.The ore beds are stratiform,stratoid and Tense-like with a thickness of 0.4一31m and conformably deposited the strata in synchronous fold.It extends in NE direction, and the thickness of its northern part is greater than that of the southern one.The ore is composed of pyrite w ith framboids texture.lts struc-ture is massive, closely banded, and sparsely banded.A number of Tentaculite fossila still retained in the ore rock.The rate of Co/Ni in the single mineral of pyrite is 0.01.The composition of sulfur isotope is rich in S32, its variation range is from-17.4 to -28.0‰. and its average is -23.7‰. In the upper and lower ore beds the values of the δS34 are stable.Along the strike of the ore body, the value of the δS34 is also even, but from east to west it decreases from -20 to -27‰ in the dip.In this region, the Devonian system was the first sedimentary covering strata after the Caledonian Movement.In the early stage of Qiziqiao, the whole region was in the open shallow sea environment, and in the middle and late stages, the large rift emerging in NE direction in the Caledonian Movement began to revive.And then,the landform of the sedimentary region presented the relief in alternat-ing high and lov- parallel to the NE direction.The high division formed the half-li-mited and limited regions of carbonate platform，and the low division w-as the region of deep water basin.The rock type.chemical composition.teaiure and structure.organic assemblage and ecological characteristics of the sediments were distinctly different in various sedimentary regions.Particularlt，in the late stage of Qiziqiao.the basin was completely situated in the environment of deep water.low grade energy and lacking of oxygen. The characteristics of the sediments were very similar to those of the Craton basin carbonate zone described by J，L.Wilson(1975)，but these basins appeared within the platform and developed in a short time.Their forms mostly occurred in the narrow and linear structure which related to the specific teotonic setting in southern C hina.Therefore，they are specially called intraplatform linear basins.The palaeogeographical site of Putou pyrite ore deposit appeared at the eastern margin of the basin in the extension of NE direction.The sedimentary environment of Putou pyrite deposit was in the deep water basin lacking of om gen, and the supplies of organic m atter and ferriginous m ateri-als were comparatively- sufficient.T he relief difference caused the existence of bioherm was not compensated it that time. Therefore, the relative strong retarding environ went appeared in the west side of the reef body，which was more favoura-ble for the concentration of the ore forming material and the organic matter.The study of sulf ur isotope of the mine has proved that the sulphates in marine water were continuously replenished to the sedimentary strata in the open condition.In the dia-genesis stage, the ore beds of pyrite, with well一developed horizontal laminated structure of large thickness and rich in S32, were formed。
1984, 2(1): 76-84.
Abstract:
Jixian coal field is 8-10 km wide from east to west and 50 km long from south to north, with an area of 500 km2.The coal field is an asymmetrical syncline slan-ting to ward the north, with a gentle east limb and a teep west limb. The major object explored is C hengzihe group, including tens of coal beds.In exploration，it has been found that there are a large number of exploitable coal beds with great thickness in the southern part, but local parts of the sa me coal bed become thin. or branch and pinch towards the north.In this paper the author pick up sections Nos.16-20 of the coal beds for analysis .Judging from the Changing trends of the isolines of the thickness of the coal beds and the strata, the thickness of the coal bed changes obviously with that of the stratigraphic thickness.By using mathematical statistics method of regression anaiysis, it can be seen that primary influential factors for contemporaneous variation are subsidence range and sedimentary environment.Thus,some simple numerical concepts of this section can be expressed follows:(1)As the stratigraphic thickness is 80-110m and the sand-conglomerate thickness is 50-80m. this belongs to the relative stable region, and coal-bearing is in good condition.(2)As the stratigraphic thickness is less than 80m and the sand-conglomerate thickness is less than 50m, this belongs to the relative upwarped region,and coal-bearing is in bad condition.(3)As the stratigraphic thickness is more than 110m and the sand-conglome-rate thickness is more than 80m, this belongs to the relative subsidence region and coal-bearing is in bad condition.Thus, it can be seen that coal一forming conditions given above are controlled by stratigraphic thickness(subsidence range)and relative stability of sedimentation.The main factor of coal formation is the assemblage relation of various environments in which rock association is taken as a representation、whereas organism is substantial condition of coal formation.
Jixian coal field is 8-10 km wide from east to west and 50 km long from south to north, with an area of 500 km2.The coal field is an asymmetrical syncline slan-ting to ward the north, with a gentle east limb and a teep west limb. The major object explored is C hengzihe group, including tens of coal beds.In exploration，it has been found that there are a large number of exploitable coal beds with great thickness in the southern part, but local parts of the sa me coal bed become thin. or branch and pinch towards the north.In this paper the author pick up sections Nos.16-20 of the coal beds for analysis .Judging from the Changing trends of the isolines of the thickness of the coal beds and the strata, the thickness of the coal bed changes obviously with that of the stratigraphic thickness.By using mathematical statistics method of regression anaiysis, it can be seen that primary influential factors for contemporaneous variation are subsidence range and sedimentary environment.Thus,some simple numerical concepts of this section can be expressed follows:(1)As the stratigraphic thickness is 80-110m and the sand-conglomerate thickness is 50-80m. this belongs to the relative stable region, and coal-bearing is in good condition.(2)As the stratigraphic thickness is less than 80m and the sand-conglomerate thickness is less than 50m, this belongs to the relative upwarped region,and coal-bearing is in bad condition.(3)As the stratigraphic thickness is more than 110m and the sand-conglome-rate thickness is more than 80m, this belongs to the relative subsidence region and coal-bearing is in bad condition.Thus, it can be seen that coal一forming conditions given above are controlled by stratigraphic thickness(subsidence range)and relative stability of sedimentation.The main factor of coal formation is the assemblage relation of various environments in which rock association is taken as a representation、whereas organism is substantial condition of coal formation.
1984, 2(1): 96-106.
Abstract:
The late Sinian strata in Hubei Province are situated in the eastern part of the shallow-sea area of the I'angtse shelf.The widspread Dengying group consists main-ly of dolomite generally 200-500m in thickness, and even up to more than 800m.Abundant small shell fossils are rich in the upper part of the Dengving group, and many blue-green algae in the middle so various types of rocks are formed. Accord-ing to the texture and genesis of the rocks, the dolomites can be grouped into six types:(1)Algae grain dolomite This type of rock includes oncolite-dolomite, lamina-ted dolomite, algae-ring dolomite, thrombolite-dolomite and algae pellet-dolomite.There are many depositional structures in algae grain-dolomite such as cross-bed-ding, scouring face and vados sand.This represents the lower part of the intertidal enironment.(2)Algae-bind dolomite This type includes stromatite dolomite, laminated do-lomite, grape-shaped dolomite sheet fissure, desiccation fissure and bird's-eye can often be found in algae-bind dolomite.This represents the part of intertidal environment. (3)Algae-mark dolomite This type of rock consists mainly of micrete. And desiccation fissure, desiccation break breccia and bird's-eye can be found in it.This reflects the upper part of the intertidal environment.(4)OÖlitic dolomite The cements mainly- are sparry calcites of two genera-tions .This is formed at the edge of carbonate platform in high energy environment.(5)Intraclastic dolomite The cements are sparry calcites.The depositional environment is as the oÖlitic dolomite.(6)Micritic dolomite Micrite-fine grain structure presents light color.The average content of Bolo mite is more than 90% and CaO/MgO=1.34.The laminated structure can often be seen, but desiccation fissure and break breccia can rarely be observed.This represents the clcsed and quiet restricted sea of intertidal and sub-tidal zones.The relationship between the above types of rocks and sedim entary structure indicates that at the end of late Sinian the environ went w as a carbonate platform for the shallow-water quiet and the energy was low.This is distributed in Jianghan plain, Hubei province, being a trumpet一like restricted sea platform.In this restri-cted sea, there are Huitingshan and Yanchihe.Algae flat is distributed in the northern part and the algae-dune of Hai-9 in the southern. The offshore lagoon facies is located at the north side of the restricted sea.The Sichuan-Guizhou platform is separated by a submarine groove in the west.At Cili there is an oolitic beach of platform edge.Yuanling-Xianning region belonges to the basin facies.Because the sedimentation at the end of late Sinian mainlw developed in the intertidal belt, dolomite predominated pores were well developed.The authigenic pores are bird's-eye, sheet fissure and intergranular pore.Secondary- pores are mainly solution-pore and intercry-stalline pore. Based on the above analysis. it is suggested that all these pores are well-developed and favourable for the oil and gas accumulation.
The late Sinian strata in Hubei Province are situated in the eastern part of the shallow-sea area of the I'angtse shelf.The widspread Dengying group consists main-ly of dolomite generally 200-500m in thickness, and even up to more than 800m.Abundant small shell fossils are rich in the upper part of the Dengving group, and many blue-green algae in the middle so various types of rocks are formed. Accord-ing to the texture and genesis of the rocks, the dolomites can be grouped into six types:(1)Algae grain dolomite This type of rock includes oncolite-dolomite, lamina-ted dolomite, algae-ring dolomite, thrombolite-dolomite and algae pellet-dolomite.There are many depositional structures in algae grain-dolomite such as cross-bed-ding, scouring face and vados sand.This represents the lower part of the intertidal enironment.(2)Algae-bind dolomite This type includes stromatite dolomite, laminated do-lomite, grape-shaped dolomite sheet fissure, desiccation fissure and bird's-eye can often be found in algae-bind dolomite.This represents the part of intertidal environment. (3)Algae-mark dolomite This type of rock consists mainly of micrete. And desiccation fissure, desiccation break breccia and bird's-eye can be found in it.This reflects the upper part of the intertidal environment.(4)OÖlitic dolomite The cements mainly- are sparry calcites of two genera-tions .This is formed at the edge of carbonate platform in high energy environment.(5)Intraclastic dolomite The cements are sparry calcites.The depositional environment is as the oÖlitic dolomite.(6)Micritic dolomite Micrite-fine grain structure presents light color.The average content of Bolo mite is more than 90% and CaO/MgO=1.34.The laminated structure can often be seen, but desiccation fissure and break breccia can rarely be observed.This represents the clcsed and quiet restricted sea of intertidal and sub-tidal zones.The relationship between the above types of rocks and sedim entary structure indicates that at the end of late Sinian the environ went w as a carbonate platform for the shallow-water quiet and the energy was low.This is distributed in Jianghan plain, Hubei province, being a trumpet一like restricted sea platform.In this restri-cted sea, there are Huitingshan and Yanchihe.Algae flat is distributed in the northern part and the algae-dune of Hai-9 in the southern. The offshore lagoon facies is located at the north side of the restricted sea.The Sichuan-Guizhou platform is separated by a submarine groove in the west.At Cili there is an oolitic beach of platform edge.Yuanling-Xianning region belonges to the basin facies.Because the sedimentation at the end of late Sinian mainlw developed in the intertidal belt, dolomite predominated pores were well developed.The authigenic pores are bird's-eye, sheet fissure and intergranular pore.Secondary- pores are mainly solution-pore and intercry-stalline pore. Based on the above analysis. it is suggested that all these pores are well-developed and favourable for the oil and gas accumulation.
1984, 2(1): 125-135.
Abstract:
On the basis of the analysis, identification and estimation of the clay minerals of northern Jiangsu, this paper deals with a more detailed analysis of the charac-teristics of the contents and combinations of the clay minerals.According to the morphology of thereflecting peaks of the X-ray diffraction spectrum pattern of the clay minerals,the difference in intensity and the distribution of the peak heights at 7Ä，10Ä and 14Ä in the triangular diagram, the surficial clay minerals in that region may be subdivided into three regions, namely: the region of the underwater delta of the ancient H uanghe River(I)，the radial sand bar region(II)，and the region of the north side of the Changjiang River mouth(III).In constrast with the clay mineral characteristics of the coastal land and rivers，it is found that the sediments of region(I)were mainly affected by the ancient H uanghe River, those of region(III) mainly came from the Changjiang River,and those of region(II)were a mixture of the sediments of the ancient H uanghe River and the C hangjiang River in its early stage.According to the analysis of the correlation data on grain size, heavy minerals,chemistry, spores and pollen, and ancient microorganisms, the distributional charac-teristics of the clay minerals have been further verified and supplemented.After the contrast is made between the distributional characteristics of the clay minerals and the data on suspended substances,salinity，hydrodynamics and sub-marine relief, it has been shown that the movement and spreading conditions of the sediments of this region are controlled by the hydrodynamic conditions.This has been also verified by satellite images.T hus,the clay mineral characteristics play an important role in the study of the sedimentary features.
On the basis of the analysis, identification and estimation of the clay minerals of northern Jiangsu, this paper deals with a more detailed analysis of the charac-teristics of the contents and combinations of the clay minerals.According to the morphology of thereflecting peaks of the X-ray diffraction spectrum pattern of the clay minerals,the difference in intensity and the distribution of the peak heights at 7Ä，10Ä and 14Ä in the triangular diagram, the surficial clay minerals in that region may be subdivided into three regions, namely: the region of the underwater delta of the ancient H uanghe River(I)，the radial sand bar region(II)，and the region of the north side of the Changjiang River mouth(III).In constrast with the clay mineral characteristics of the coastal land and rivers，it is found that the sediments of region(I)were mainly affected by the ancient H uanghe River, those of region(III) mainly came from the Changjiang River,and those of region(II)were a mixture of the sediments of the ancient H uanghe River and the C hangjiang River in its early stage.According to the analysis of the correlation data on grain size, heavy minerals,chemistry, spores and pollen, and ancient microorganisms, the distributional charac-teristics of the clay minerals have been further verified and supplemented.After the contrast is made between the distributional characteristics of the clay minerals and the data on suspended substances,salinity，hydrodynamics and sub-marine relief, it has been shown that the movement and spreading conditions of the sediments of this region are controlled by the hydrodynamic conditions.This has been also verified by satellite images.T hus,the clay mineral characteristics play an important role in the study of the sedimentary features.
1984, 2(1): 18-28.
Abstract:
A kind of rock- tubules(3-25 mm in diameter and 30-50cm in length)occurs in the late Pleistocene biosparites on the Shidao Island of lisha Islands，China.These tubules, whcih had been misunderstood as colony of corals species Acropora, or colony of warm pipes, have concentric stratoid structures.Its inner stratu m, having acentral tubule 5一8 mm in diameter, is made of dark brown micrite with corrosional cements but the light gray outerstratum is made of biosparites cemented by finely crystalline sparry calcites(0. 03-0. 04mm)，and locally filled up the intergranular space.Another kind of rocky tubules occurs in the Pleistocene fine sandy-silty sediments interbedded with stratoid and lenticular dolomites is the Paipu area of northwestern Hainan Island,China.These tubules have mainly vertical and horizontal occurrences with circle and oval cross section.They- also have stratoid structures.The loose and rough central area ,about 4 mm in diameter. consists of 65一75% quartz and other elastic materials and 10-15% crystalline dolomite.The fine and dense intensely dolomitized inner stratum( 5 -10 mm in thickness)consists of 90% dolomite,only 5% clastic materials and 5 % pore space.This dolomite is a euhedral rhombohedron,medium to very finely crwstalline with porphwritic testure.The silty clastic particles have relict structures caused by the infiltration and replacement.The loose cemented outer stratum consists of 40% elastic particles(medium to coarse grain size)，40%euhedral finely一medium crystalline dolomite and about 20% pore.The physiological action of plants controls the formation of these rocky tubules around the plant roots. Their formation mechanism is as follows:The transpiratio and respiration or metabolism of plants suck up moisture from below.drain，off the CO2 and organic acid on the one hand. and the vadose watr moves down along the roots on the other.Thus. in the microen}ironment near the root, the dissolution.precipitation and metasomatism of carbonate take place re-etpeatedly around the root system.and primary carbonate tubules are formed during their living time。After their death.the surface water may infiltrate along the formed tubules, the dissolution of the sediments and precipitation of crystalline calcite within the pore space mac continuously- take place.Carbonate tubules formed in such a way are called infiltration rocky tubules by the authors. In the vadose zone with fresh water, calcite rocky tubule is formed, whereas in the intertidal zone of the coast.the dolomitized infiltration rock3- tubule is formed under the influence of schizahaline condition produced by sea water alternating with fresh ground water.This unusual process of dolomite formation may- be called dolomitization of plants.The formation of infiltrated rocky tubules as a process of early diagenesis is of great sigricance for the romprehension of the direct effect of plants on the diagenesis
A kind of rock- tubules(3-25 mm in diameter and 30-50cm in length)occurs in the late Pleistocene biosparites on the Shidao Island of lisha Islands，China.These tubules, whcih had been misunderstood as colony of corals species Acropora, or colony of warm pipes, have concentric stratoid structures.Its inner stratu m, having acentral tubule 5一8 mm in diameter, is made of dark brown micrite with corrosional cements but the light gray outerstratum is made of biosparites cemented by finely crystalline sparry calcites(0. 03-0. 04mm)，and locally filled up the intergranular space.Another kind of rocky tubules occurs in the Pleistocene fine sandy-silty sediments interbedded with stratoid and lenticular dolomites is the Paipu area of northwestern Hainan Island,China.These tubules have mainly vertical and horizontal occurrences with circle and oval cross section.They- also have stratoid structures.The loose and rough central area ,about 4 mm in diameter. consists of 65一75% quartz and other elastic materials and 10-15% crystalline dolomite.The fine and dense intensely dolomitized inner stratum( 5 -10 mm in thickness)consists of 90% dolomite,only 5% clastic materials and 5 % pore space.This dolomite is a euhedral rhombohedron,medium to very finely crwstalline with porphwritic testure.The silty clastic particles have relict structures caused by the infiltration and replacement.The loose cemented outer stratum consists of 40% elastic particles(medium to coarse grain size)，40%euhedral finely一medium crystalline dolomite and about 20% pore.The physiological action of plants controls the formation of these rocky tubules around the plant roots. Their formation mechanism is as follows:The transpiratio and respiration or metabolism of plants suck up moisture from below.drain，off the CO2 and organic acid on the one hand. and the vadose watr moves down along the roots on the other.Thus. in the microen}ironment near the root, the dissolution.precipitation and metasomatism of carbonate take place re-etpeatedly around the root system.and primary carbonate tubules are formed during their living time。After their death.the surface water may infiltrate along the formed tubules, the dissolution of the sediments and precipitation of crystalline calcite within the pore space mac continuously- take place.Carbonate tubules formed in such a way are called infiltration rocky tubules by the authors. In the vadose zone with fresh water, calcite rocky tubule is formed, whereas in the intertidal zone of the coast.the dolomitized infiltration rock3- tubule is formed under the influence of schizahaline condition produced by sea water alternating with fresh ground water.This unusual process of dolomite formation may- be called dolomitization of plants.The formation of infiltrated rocky tubules as a process of early diagenesis is of great sigricance for the romprehension of the direct effect of plants on the diagenesis
1984, 2(1): 44-52.
Abstract:
Polyclic aromatic hydrocarbons(PAH)in source rock from Wells A 3 and Sai 1 of the Erlian basin ofNeimongol autonomous Region are taken for examples.In this article alkylnaphth-alene and alkylphenathrene homologs of the short chains, flouranthene, pyrene, mephylpyene, benz(a)anthracene; perylene, etc.are identified and quantified by GC and GC-MS. Pimanthrene(1，7-dimethylphe-manthrene)，retene(1 -methyl一7-isopropyl phenanthrene)and 1-methyl-7-isop-ropyl-1，2，3，4-tetrahy drophenanthrene regarded as representative materials of high plant lipide have been found in different depths of PAH in source rock.The relative contents of alkylphenanthrenes(phenanthrene, C1一Phenanthrene,C2一phenanthrene, retene, etc.)exhibiting gradual changes with increasing depth in aromatic fraction of sedimentary rocks from the two wells in different depths are calculated and revealed in this article.It seems that the changes can reflect the maturity of source rocks.The unclear changes of relative contents of fluran thene, pyrene, etc.R-ith different depths are discussed as well。
Polyclic aromatic hydrocarbons(PAH)in source rock from Wells A 3 and Sai 1 of the Erlian basin ofNeimongol autonomous Region are taken for examples.In this article alkylnaphth-alene and alkylphenathrene homologs of the short chains, flouranthene, pyrene, mephylpyene, benz(a)anthracene; perylene, etc.are identified and quantified by GC and GC-MS. Pimanthrene(1，7-dimethylphe-manthrene)，retene(1 -methyl一7-isopropyl phenanthrene)and 1-methyl-7-isop-ropyl-1，2，3，4-tetrahy drophenanthrene regarded as representative materials of high plant lipide have been found in different depths of PAH in source rock.The relative contents of alkylphenanthrenes(phenanthrene, C1一Phenanthrene,C2一phenanthrene, retene, etc.)exhibiting gradual changes with increasing depth in aromatic fraction of sedimentary rocks from the two wells in different depths are calculated and revealed in this article.It seems that the changes can reflect the maturity of source rocks.The unclear changes of relative contents of fluran thene, pyrene, etc.R-ith different depths are discussed as well。
1984, 2(1): 65-75.
Abstract:
A lot of strata-bound carbonate uranium deposits occurred in the Proterozoic Era and Paleozoic Era.Their ore bodies are concentrative, shallow-buried and of the high tenor，so they are the spceial and important economic deposits in China.According to our investigations,the genetic geological-geochemical conditions may be summarized as follows;(1)In the carbonate formations, uranium abundance is higher within the ho-rizons which contain clay, carbonaeous materials and pyrite as absorbents or reduc-tors. They provided the material source and favourable reservoir for the uranium mineralization. (2)Tectonic-magma activities developed intensively from Indo-China to Yan-shan period in the”Diwa"regions where faults mobilized repeatedly and created fa-vourable spatial conditions for uranium activation and mineralization.(3)The mineralization underwent a long.multistage and polygenetic.Generally speaking, the more stages the mineralization underwent，the more distinctly the uranium evolution separated, and the more favourable for mineralization.The reg-ions where underwent the three main evolutional stages, i.e. geosyneline-plate-form一"Diwa" were favourable for mineralization.(4)The areas of fossil hydrothermal development, the terrestrial heat ano-maly and the section containing fossil karst are the places for the medium activa-tion of mineralization.Under certain geological structure and dry paleoclimatic condi-tions, uranium concentration in mineralization solution increased continuously and superimposed on the carbonate section where uranium was initially enriched, and this is often the place where uranium deposits occurred.
A lot of strata-bound carbonate uranium deposits occurred in the Proterozoic Era and Paleozoic Era.Their ore bodies are concentrative, shallow-buried and of the high tenor，so they are the spceial and important economic deposits in China.According to our investigations,the genetic geological-geochemical conditions may be summarized as follows;(1)In the carbonate formations, uranium abundance is higher within the ho-rizons which contain clay, carbonaeous materials and pyrite as absorbents or reduc-tors. They provided the material source and favourable reservoir for the uranium mineralization. (2)Tectonic-magma activities developed intensively from Indo-China to Yan-shan period in the”Diwa"regions where faults mobilized repeatedly and created fa-vourable spatial conditions for uranium activation and mineralization.(3)The mineralization underwent a long.multistage and polygenetic.Generally speaking, the more stages the mineralization underwent，the more distinctly the uranium evolution separated, and the more favourable for mineralization.The reg-ions where underwent the three main evolutional stages, i.e. geosyneline-plate-form一"Diwa" were favourable for mineralization.(4)The areas of fossil hydrothermal development, the terrestrial heat ano-maly and the section containing fossil karst are the places for the medium activa-tion of mineralization.Under certain geological structure and dry paleoclimatic condi-tions, uranium concentration in mineralization solution increased continuously and superimposed on the carbonate section where uranium was initially enriched, and this is often the place where uranium deposits occurred.
1984, 2(1): 85-95.
Abstract:
Birdseye structure is a sedimentary structure formed by physical, chemical and biological processes.Based on the studies of the carbonate rocks of the Upper Sinian in southern China and the Upper Cretaceous-Lower Tertiary in southern Xin-jing and northern liangsu, this Paper sums up sit birdseye structural categories:isolate, isolate-like, irregular, tabular-and-striped, vermiform, and discontinuously laminated.The isolate-type birdseye structure in mudstone and wackestone was formed by the aggregation of gases produced by decomposition of organic matter in the sediments.The birdseye pores of this type are characteristic of isolated spots of mm level in distribution, filling sparry dolomite or calcite and normally lacking rim cement and geotropic sediments.In packstone anti grainstone it might result from the aggrega-tion of gases or and air bubbles sealed by capillarity when drying sediments were flooded .The former might occur in various environments f rom subtidal zone to intertidal zone and supratidal marsh, but the latter mostly developped in the inter-tidal zone and flooded supratidal marsh.The isolate-like一type birdseye pores, usually in wackestone, exhibit laterally elongate patches which are roughly- parallel to stratification and better link up with each other. and in which there are commonly geotropic sediments of vadose silts.This type of birdseye pores might result from the air bubbles sealed by means of capillarity under the condition alternating drying with wetting.The surfaces of geotropic sediments in the birdseye pore spaces appear often to be at the same level which might roughly represent groundwater level at that time.Irregular type and tabular-and-striped type of birdseye structures, which developed commonly in various cryptalgal carbonate rocks, were formed by non-calcified growth of blue一green algae. The host rock with irregular birdseyes appear to be distinctly characteristic of abundant peloids and clots and of the irregular birdseye pores linking up each other very- well which occupy relatively high percentage in volume so that the rocks exhibit poorly supporting state in thin section.They develop best in both of lower intertidal zone and seaward edge of supratdal marsh(Monty, 1976,Monty and Hardie, 1976)，and sometimes they can occur in the upper subtidal zone (Kinsman and Park, 1976).Vermiform一type birdseye structure was caused clearly by drying and shrinking and usually developed in the carbonate muds and laminated cryptalgal carbonate sediments of intertidal or supratidal zone。 Discontinuously laminated type of birdseye structure was mostly formed by evaporation, partly by penecontemporaneous leaching process. This type of birds-eye structure in laminated cryptalgal carbonate rocks could occur in the intertidal zone and supratidal marsh, but that in laminated non-cryptalgal carbonate rock(mostly dolostone)could be found only in the supratidal zone.It is considered that the aggregation of gases, noncalcified growth of blue一green algae. drying and shrinking, and sealed air bubbles are the four main origins forming birdseye structures. In the laboratory. two patterns of birdseye struc-tures caused by the aggregation of gases and sealed air bubbles have been obtained.The sample of recent unconsolidated sediments collected from the incertidal zone of Shanya Bay, Hainan Island, resulted in two layers in colour, brownish yellow layer in upper 1/3 of the height of the sample in the bottle and brownish grey layer in lower 2/3，after two to three months. Isolate一type birdseye pores in millimetre size(the largest up to over 1 cm)took place in the lower because of the aggregation of gases produced by decomposition of organic matter in this layer(Plate 1一5 a and 5 b, Fig.1).In addition, when the samples.skeletal fragments from the reef flats of Xisha Islands, were set into the bottles and then water was slowly poured into it till the samples were covered at all, numerous air bubbles occurred and were kept in intergrain pore spaces, and might later aggregate to form isolate一like type of birdseye structure.From mentioned above, birdseye structures may be formed by various modes of origin and in various environments, i.e.from subtidal zone to supratidal marsh.Therefore, it is inexact to consider all birdseye structures as a symbol indicating supratidal or iniertidal environment.We can give the birdseye structure a more correct paleoenvironmental interpretation only after the mode of origin has been defined and petrological characteristics have been studied.
Birdseye structure is a sedimentary structure formed by physical, chemical and biological processes.Based on the studies of the carbonate rocks of the Upper Sinian in southern China and the Upper Cretaceous-Lower Tertiary in southern Xin-jing and northern liangsu, this Paper sums up sit birdseye structural categories:isolate, isolate-like, irregular, tabular-and-striped, vermiform, and discontinuously laminated.The isolate-type birdseye structure in mudstone and wackestone was formed by the aggregation of gases produced by decomposition of organic matter in the sediments.The birdseye pores of this type are characteristic of isolated spots of mm level in distribution, filling sparry dolomite or calcite and normally lacking rim cement and geotropic sediments.In packstone anti grainstone it might result from the aggrega-tion of gases or and air bubbles sealed by capillarity when drying sediments were flooded .The former might occur in various environments f rom subtidal zone to intertidal zone and supratidal marsh, but the latter mostly developped in the inter-tidal zone and flooded supratidal marsh.The isolate-like一type birdseye pores, usually in wackestone, exhibit laterally elongate patches which are roughly- parallel to stratification and better link up with each other. and in which there are commonly geotropic sediments of vadose silts.This type of birdseye pores might result from the air bubbles sealed by means of capillarity under the condition alternating drying with wetting.The surfaces of geotropic sediments in the birdseye pore spaces appear often to be at the same level which might roughly represent groundwater level at that time.Irregular type and tabular-and-striped type of birdseye structures, which developed commonly in various cryptalgal carbonate rocks, were formed by non-calcified growth of blue一green algae. The host rock with irregular birdseyes appear to be distinctly characteristic of abundant peloids and clots and of the irregular birdseye pores linking up each other very- well which occupy relatively high percentage in volume so that the rocks exhibit poorly supporting state in thin section.They develop best in both of lower intertidal zone and seaward edge of supratdal marsh(Monty, 1976,Monty and Hardie, 1976)，and sometimes they can occur in the upper subtidal zone (Kinsman and Park, 1976).Vermiform一type birdseye structure was caused clearly by drying and shrinking and usually developed in the carbonate muds and laminated cryptalgal carbonate sediments of intertidal or supratidal zone。 Discontinuously laminated type of birdseye structure was mostly formed by evaporation, partly by penecontemporaneous leaching process. This type of birds-eye structure in laminated cryptalgal carbonate rocks could occur in the intertidal zone and supratidal marsh, but that in laminated non-cryptalgal carbonate rock(mostly dolostone)could be found only in the supratidal zone.It is considered that the aggregation of gases, noncalcified growth of blue一green algae. drying and shrinking, and sealed air bubbles are the four main origins forming birdseye structures. In the laboratory. two patterns of birdseye struc-tures caused by the aggregation of gases and sealed air bubbles have been obtained.The sample of recent unconsolidated sediments collected from the incertidal zone of Shanya Bay, Hainan Island, resulted in two layers in colour, brownish yellow layer in upper 1/3 of the height of the sample in the bottle and brownish grey layer in lower 2/3，after two to three months. Isolate一type birdseye pores in millimetre size(the largest up to over 1 cm)took place in the lower because of the aggregation of gases produced by decomposition of organic matter in this layer(Plate 1一5 a and 5 b, Fig.1).In addition, when the samples.skeletal fragments from the reef flats of Xisha Islands, were set into the bottles and then water was slowly poured into it till the samples were covered at all, numerous air bubbles occurred and were kept in intergrain pore spaces, and might later aggregate to form isolate一like type of birdseye structure.From mentioned above, birdseye structures may be formed by various modes of origin and in various environments, i.e.from subtidal zone to supratidal marsh.Therefore, it is inexact to consider all birdseye structures as a symbol indicating supratidal or iniertidal environment.We can give the birdseye structure a more correct paleoenvironmental interpretation only after the mode of origin has been defined and petrological characteristics have been studied.
1984, 2(1): 107-124.
Abstract:
A systematic petrological research has been made on nearshore surficial sedi-ments(the mazimum depth is 30m)of southern Shandong Peninsula(the area is located between the mouth of liaozhou Bay- and Rizhao County).The nearshore surficial sedimentsare divided into three sedimentary regions as follows,Recent coastal sedimentary region:This is distributed within the depth of 10-15m，and presents a striped form parallel to the coastline.The sediments are mainly sand. muddy silt and sand-silt-mud.Their granulometric parameters vary within a large range because of the、一arious types of sediments.T he sediments are rich in feldspar, but owing to the difference of the characters of coastal source rock，the Q/F ratio is less than 1 in the south and 1一3 in the north.The content of nemetamorphic quartz is more in the south and less in the north.The mean round-ss of quartz of coarse sand grain is 0.29(according to Power standard)，so it is subangular.almost all the sediments consist of terrigenous materials, with a little-organic and authigenic components.Common organisms are Forominifera and Pelecypoda.Recent shelf sedimentary- region:This is located at the northeast of the studied area, where the water depth is more than 15 m.The sediments are principally sand-silt-mud and muddy- silt(Mz=6.38-7.59Φ)，for hydrodynamic effect is weak.Since there is not only one source, the sediments are very poorly sorted(σ1=2.70-3.-12).After CaCo3 being removed, sorting coefficient rises, but ii is still greaterthan 2 .It is positively skew and its kurtosis smooth.In> 0.063mm fraction,Q, F ratio is high(4-8).The content of metamorphic polycrystalline quartz is medium, less than 10% at bathvmetric line of about 20 m，and it increases outward to 10-20% T he roundness of coarse sand fraction(Ms=0.30) is higher than that of recent coastal sedimentary region.Basically, there is little glauconite and calca-reous concretion,but organic content is higher than that in the coastal region, com-monly 5-10% in sand fraction.Foraminifera is major organism and its principal species is Ammonia compressiuscula.residual sedimentary region:This is situated in the south of the studied area, where water depth is more than 10-15 m.The sediments(except calcareous concretion)are conglomeratic sand and san(Mz=0.98-3.51Φ).Granulometric parameters are extremely abnormal, such as very poor sorting(σ1=3.98-4.78)，positive or extre-mely positive skewness(SK=0.15-0.39)and commonly abnormal kurtosis.The types of sediment compositions are conglomeratic arkose and arkose(Q, F<2).The con-tent of metamorphic polycrystalline quartz is rather high near the shore，but drops rapidly outward to less than 10%.The roundness of quartz is high, belonging to subrounded class(Mρ = 0.34)，much higher than that in the other two regions.The content of iron-staining quartz of tile region is also high(> 40%).The sedimen-ts of this region are rich in calcareous concretion which belongs to terrigenous authigenic component, so the content of CaC03 is commonly higher than 12%.The content of glauconite is also much higher than that in the other two regions.Organ-ic association is characterized by the appearance of oyster-bryozoa and contains Candoniella sp.The textures of sediments in recent coastal and shelf sedimentary regions are is equilibrium with the water depth where they are.Palimpsest sediments are origin-ally of intertidal zone-coastal facies, and were formed 30,000 yrs B.P.They ex-perienced reformation in a continental envionment because of regression.Calcareous concretions were formed during this period(14C dating is 17,870±260 yr).They were not submerged until the Holocene transgression and they have received little sediments since then。
A systematic petrological research has been made on nearshore surficial sedi-ments(the mazimum depth is 30m)of southern Shandong Peninsula(the area is located between the mouth of liaozhou Bay- and Rizhao County).The nearshore surficial sedimentsare divided into three sedimentary regions as follows,Recent coastal sedimentary region:This is distributed within the depth of 10-15m，and presents a striped form parallel to the coastline.The sediments are mainly sand. muddy silt and sand-silt-mud.Their granulometric parameters vary within a large range because of the、一arious types of sediments.T he sediments are rich in feldspar, but owing to the difference of the characters of coastal source rock，the Q/F ratio is less than 1 in the south and 1一3 in the north.The content of nemetamorphic quartz is more in the south and less in the north.The mean round-ss of quartz of coarse sand grain is 0.29(according to Power standard)，so it is subangular.almost all the sediments consist of terrigenous materials, with a little-organic and authigenic components.Common organisms are Forominifera and Pelecypoda.Recent shelf sedimentary- region:This is located at the northeast of the studied area, where the water depth is more than 15 m.The sediments are principally sand-silt-mud and muddy- silt(Mz=6.38-7.59Φ)，for hydrodynamic effect is weak.Since there is not only one source, the sediments are very poorly sorted(σ1=2.70-3.-12).After CaCo3 being removed, sorting coefficient rises, but ii is still greaterthan 2 .It is positively skew and its kurtosis smooth.In> 0.063mm fraction,Q, F ratio is high(4-8).The content of metamorphic polycrystalline quartz is medium, less than 10% at bathvmetric line of about 20 m，and it increases outward to 10-20% T he roundness of coarse sand fraction(Ms=0.30) is higher than that of recent coastal sedimentary region.Basically, there is little glauconite and calca-reous concretion,but organic content is higher than that in the coastal region, com-monly 5-10% in sand fraction.Foraminifera is major organism and its principal species is Ammonia compressiuscula.residual sedimentary region:This is situated in the south of the studied area, where water depth is more than 10-15 m.The sediments(except calcareous concretion)are conglomeratic sand and san(Mz=0.98-3.51Φ).Granulometric parameters are extremely abnormal, such as very poor sorting(σ1=3.98-4.78)，positive or extre-mely positive skewness(SK=0.15-0.39)and commonly abnormal kurtosis.The types of sediment compositions are conglomeratic arkose and arkose(Q, F<2).The con-tent of metamorphic polycrystalline quartz is rather high near the shore，but drops rapidly outward to less than 10%.The roundness of quartz is high, belonging to subrounded class(Mρ = 0.34)，much higher than that in the other two regions.The content of iron-staining quartz of tile region is also high(> 40%).The sedimen-ts of this region are rich in calcareous concretion which belongs to terrigenous authigenic component, so the content of CaC03 is commonly higher than 12%.The content of glauconite is also much higher than that in the other two regions.Organ-ic association is characterized by the appearance of oyster-bryozoa and contains Candoniella sp.The textures of sediments in recent coastal and shelf sedimentary regions are is equilibrium with the water depth where they are.Palimpsest sediments are origin-ally of intertidal zone-coastal facies, and were formed 30,000 yrs B.P.They ex-perienced reformation in a continental envionment because of regression.Calcareous concretions were formed during this period(14C dating is 17,870±260 yr).They were not submerged until the Holocene transgression and they have received little sediments since then。
