Table of Content

20 April 2018, Volume 24 Issue 2

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LA-ICP-MS Zircon U-Pb Geochronology and Geochemistry of the Kushenkuduke Quartz Diorite in Western Junggar and Its Tectonic Significance

QIAO Gengbiao, ZHAO Hansen, CHEN Junlu, BAI Jianke, PENG Suxia, FAN Jinsheng

2018, 24(2):  147. 

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The Kushenkuduke quartz diorite is located in the Late Paleozoic intermediate-acidic magmatic rocks belt along Dalbute
area in Western Junggar, Xinjiang. LA-ICP-MS zircon U-Pb dating yields an age of 305.3±2.8 Ma （n=19, MSWD= 0.17） for the
quartz diorite, indicating that it was generated during late stage of the Late Carboniferous (C2). The quartz diorite has a hypidiomorphic
heterogranular texture and a massive structure, and consists mainly of plagioclase, quartz, amphibole, and biotite, etc. A small amount
of quartz gabbro diorite with columnar pyroxene has also been observed in this pluton. The geochemical analyses show that the pluton
is characterized by SiO2 of 59.38%~63.37%, total alkali (Na2O+K2O) of 6.55%~7.51%, and Rittman index σ of 2.62~2.88, aluminumHREE=3.86~4.38, (La/Yb)N=2.99~3.66 ), with negative Eu anomalies (δEu=0.64~0.79) . The trace elements are characterized by Ba,
Nd, Zr, K, LREE enrichment, and Rb, Nb, Th, Sr, P, Ti, HREE depletion. All the features suggest a high K calcic-alkaline I-type
granite. The quartz diorite was likely derived from metabasalt in the upper crust, and subsequently underwent the fractional
crystallization of plagioclase, pyroxene, rutile, and apatite without amphibole. Based on comprehensive analysis of the genetic type of
the quartz diorite and evolution of regional tectonic environment, we suggest that when the Junggar Ocean perpetually continued its
deep subduction toward north from the early Late Carboniferous to the Early Permian, and the Kushenkuduke quartz diorite of the
island-arc type was formed during this tectonic evolution.

Geochronology, Geochemistry, and Hf isotopic Compositions of the Late-Carboniferous Volcanic Rocks in Tongshengmao of Daqinshan Area, Inner Mongolia and Their Geological Implications

ZHANG Qiao, LI Yuhong, CHEN Gaochao, HAN Wei, Wang Jing

2018, 24(2):  160. 

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The northern margin of North China Block (NCB) is a key region for exploring the closure and evolution of the Paleo-Asian
Ocean, which has attracted much attention. Previous research has shown that there exists intensive late-Paleozoic
magmatism which is composed almost entirely of intrusives and lack of coeval volcanic rocks. In this paper, we present detailed
LA-ICP-MS zircon U-Pb ages, major and trace elements, and Hf isotopic compositions of the volcanic rocks from the upper part of the
Shuanmazhuang Formation, Tongshengmao of Daqinshan district in Inner Mongolia. LA-ICP-MS zircon U-Pb dating shows that the
volcanic rocks of the upper part of the Shuanmazhuang Formation were generated at 305 Ma. The volcanic rocks consist of
weakly-welded rhyolitic tuffs that suffered from intense kaolinization. These volcanic rocks have low REE contents with subtle negative
Eu anomalies and show low HREE (e.g., Y, Yb) contents. They also have negative εHf(t) values ranging from -8.3 to -4.0. These
characteristics suggest that they were likely generated from partial melting of the thickened NCB crustal basements, and with some
involvement of mantle-derived magmas. In combination with the latest reports about the distribution of late Paleozoic volcanic rocks inthe northern margin of NCB, it is inferred that there likely existed two stages of volcanism at least during the late-Paleozoic, with ages of
305~290 Ma and 278~261 Ma, and a peak volcanism at 272 Ma.

Study on Petrogenesis and Uranium Mineralization Potential of Eastern Sanjiangkou Granitic Pluton

LAN Hongfeng, LING Hongfei, CHEN Weifeng, LIU Jianwei, OUYANG Pingning

2018, 24(2):  172. 

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The southern Zhuguangshan composite pluton (SZCP) is one of the important uranium resource bases of China. The S-type
granites in SZCP have a close relationship with uranium ore deposits, while the I-type granites in SZCP possess no uranium
metallogenic potential. The Sanjiangkou granitic pluton in the western part of SZCP has similar lithology to the adjacent
Yanshanian Changjiang granite which is a S-type granite and hosts uranium ore deposits. Till present, the Sanjiangkou granite has
rarely been studied, its precise chronology is lacked and its genetic type needs to be determined. In this paper, an integrated study
including geochronology, petrogeochemistry and Sr-Nd isotopic geochemistry of eastern Sanjiangkou granite and comparison with
uranium-bearing Changjiang granite has been conducted. LA-ICP-MS zircon U-Pb dating for the eastern Sanjiangkou granite yields an
age of 161.9±2.1 Ma, suggesting its emplacement in the early Yanshanian period. Chemically, the granite has high SiO2 contents (73.5%~76.1%) and low FeOT (1.12%~3.25%), MgO (0.07%~0.83%) and CaO (0.64%~1.27%) contents, thus is highly fractionated with high
differentiation index (DI) values (86.4~93.6). A/CNK values of the granite vary from 1.00 to 1.35, indicating that it is a peraluminous to
strongly peraluminous granite. The granite is depleted in Ba, Sr, Nb, Eu and Ti, but enriched in Rb, Th and U, showing characteristics
of a typical low Ba and Sr granite. The rock samples display medium total REE contents (ΣREE = 119 × 10-6~268 × 10-6), and their REE
distribution patterns are right-inclined. Isotopic geochemical analysis results reveal variable initial 87Sr/86Sr ratios (0.70789~0.71488),
yet low and constant εNd(t ) values (-10.8~-9.6) with two stage model ages of 1.73~1.83 Ga. The geochemical and geochronological
characteristics of the eastern Sanjiangkou granite are similar to those of the Changjiang granite. Both of them are believed to be S-type
granitoids. Combining zircon U-Pb dating and regional tectonic setting, we suggest that the genesis of these granites were likely related
to the crustal extension during the early Yanshanian in South China, and they were generated through partial melting of the Mayuan
Group para-metamorphic rocks, with possibly minor involvement of mantle materials. Compared with the Changjiang granite, the
eastern Sanjiangkou granite is believed to possess prosperous uranium mineralization potential.

Geochemistry, Element Migration and Mechanism of Uranium Mineralization in the Periphery of the Shazijiang Uranium Ore Deposit

WANG Zhengqing, FAN Honghai*, CHEN Donghuan, ZHENG Kezhi, LUO Qiaohua

2018, 24(2):  185. 

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The uranium content has positive correlations with the abundance of SiO2, CaO, Fe2O3, LOI and HREEs and Na is almost
depleted at the mineralization and alteration positions of a drill core in the Shazijiang uranium ore-deposit. In trace element spider
diagram and REEs distribution pattern diagram, the shapes of different mineralized and altered belt samples are very similar. The
REEs distribution pattern shows that LREEs are enriched and the distribution lines are lean to right. Compared with the fresh
surrounding rocks, the altered surrounding rocks have elevated Sb and U concentrations and a few more Ni and W concentrations.
Compared with the fresh surrounding rocks and altered surrounding rocks, the cataclastic granites (ore) have significantly increased Cd
and Sb concentrations, while W, Ni and Pb concentrations increase slightly, and Be and Bi concentrations reduce sharply. Compared with
the fresh surrounding rocks, cataclastic granites (ore) and the altered surrounding rocks are characterized by significantly increased Sb
and U concentrations and Sb, Cd and U concentrations, respectively. In addition, both W and Ni increase slightly. Research of element
migration in mineralization and alteration belts shows that Sb, LOI, CaO, Ni, Cu, In and Sr moved in, of which Sb has the largest positivemobility value. In contrast, Na2O, FeO, Be, Cs, Th and Nb all moved out, of which Na2O has the largest negative mobility value. Based on
the results and discussion of geochemistry and element migration, we deduce that the granitic surrounding rocks are one of the most
important sources of uranium and other components, and the ore-forming fluid is alkaline with high oxygen fugacity.

Mineralogical Characteristics and Geological Significance of Copper Minerals in Fule Pb-Zn Deposit, Yunnan Province, China

LI Zhenli, YE Lin*, HUANG Zhilong, ZHOU Jiaxi, HU Yusi, NIAN Hongliang

2018, 24(2):  200. 

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The mineral assemblage in the MVT Pb-Zn deposits is generally simple because the copper minerals of this type of deposit
are very rare. As one of the largest MVT deposits in the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic domain, the Fule Pb-Zn
deposit is hosted in the Permian Yangxin Formation dolostone, which is the youngest ore-bearing strata in the area, and the distance
between Pb-Zn ore bodies and the Permian Emeishan basalts is less than 160 m. By means of microscopic, Scanning Electron
Microscopy (SEM) and Energy Dispersive Spectrum (EDS) analysis, a great number of copper-bearing minerals were found in the
deposit, including chalcopyrite, Zn-tennantite, tetrahedrite and malachite. These minerals occur as banded, vein and irregular, and
replace sphalerite or pyrite. The research shows that the droplet chalcopyrite is distributed within sphalerite, implying that both of themsphalerite grain, or distributed at the edge of the sphalerite, indicating that it was formed later than that of Pb-Zn mineralization. The
copper minerals mentioned in this study commonly occur in middle-low temperature hydrothermal deposits, in which the Zn-tennantite
is a rare sulfosalts. The appearance of Zn-tennantite and tetrahedrite indicates an oxidizing environment, and malachite is a secondary
mineral formed at supergene weathering stage. The paragenetic sequence in the deposit is inferred as follows: pyrite→sphalerite
(droplet chalcopyrite)→galena→chalcopyrite→Zn-tennantite→tetrahedrite→malachite. Combined with the geologic and geochemical
characteristics of this deposit, it is suggested that there are two possible sources of copper. Early-stage copper was derived mainly from
the basement of the Kunyang group and the late-stage copper was likely stemmed from the upper Emeishan basalts, which are different
from those of Pb and Zn derived mainly from the Kunyang Group in the deposit. The research provids new geological and geochemical
evidence for understanding the genetic relationship between the Emeishan basalts and Pb-Zn mineralization in the SYG district.

Study on Characteristics of Lower Cambrian Strata and Genesis of Uranium Enrichment/Mineralization in the Strata in Xiushui Area

XUE Weiwei, LING Hongfei*, LI Da, WEI wei, WEI Guangyi, GAO Mengqi

2018, 24(2):  210. 

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In this study, we made microscopic investigation on drilling bore hole black shale samples of the Lower Cambrian Series
which consists of the Wangyinpu Formation and overlying lower part of the Guanyintang Formation (uranium content ranging from
9.37×10-6~202×10-6) in Xiushui area of Jiangxi Province, and found that the bore hole samples have features that reflect sedimentation
and diagenesis without hydrothermal process or supergene leaching/illuviation process. We further analyzed the relationship between
uranium content of the strata and various aspects of environment factors such as redox condition of bottom water during deposition of
the black shale, primary productivity and degree of water communication between the sedimentary basin and the open ocean. In most of
the samples, uranium content is positively correlated with total organic carbon content (TOC). The uranium content (202×10-6) in one
sample that is located in the upper part of the Wangyinpu Formation is the highest, as well is the productivity reflected by organicmatter. In this sample, pitchblende has been found within the carbonized organic matter by using SEM and EPMA. The uranium may
have deposited with the organic matter into the sediments. Afterwards, the uranium formed the pitchblende, and the organic matter
become carbonized during diagenesis of the sediments. The Wangyinpu Formation has higher uranium content than the lower part of
the Guanyintang Formation. It is also revealed that the Wangyinpu Formation was deposited mainly under sulfidic bottom waters and
the lower part of the Guanyintang Formation was deposited mainly under anoxic bottom waters without sulfide. Under sulfidic
condition, sediments deposited in an environment with less restriction would have higher uranium content than sediments deposited in
an environment with more restriction. In summary, during the period of deposition of the upper part of the Wangyinpu Formation,
sedimentation and degradation of organic matter produced by high bioproductivity in the photic waters of the basin consumes much of
the oxygen in the bottom seawaters of the basin, and thus strongly reducing sulfidic environment would prevail in the bottom seawaters.
At the same time, appropriately well connection of the sedimentary basin to the open ocean would provide enough uranium into the
sulfidic environment to deposit, resulting in highly enrichment or even mineralization of uranium in the sediments.

Environmental Geochemical Characteristics and Genesis of the Weathering Crust of Carbonate Rocks in Eastern Yunnan Province

MA Haiou, WANG Lifa, GUO Song, LI Shuangshuang, CAI Xiaojuan, JI Hongbing

2018, 24(2):  222. 

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The red soil formed by carbonate weathering has preserved the historical evidence of karst development and evolution, and it
is also an important object of soil research in karst area. In this paper, the two typical carbonate profiles in Shilin area of Yunnan were
selected to study the migration characteristics and distribution of the major elements, trace elements, and rare earth elements in the
weathering crusts, and further explore the genesis of the weathering crust. The results show that: (1) using the migration
characteristics of Ti as the reference element, the major elements of the two sections show similar migration patterns in the process
of soil formation, and most of them are characterized by leaching. The trace elements are slightly different and the degree of
leaching is different. (2) UCC normalized spider graphs show that Ca and Sr in the weathered crust are depleted with respect to thebedrock; Fe, Ti and other elements are slightly enriched in comparison to UCC, Mg, Ca, Na, K, P, and other elements show a large
decrease. (3) The REE distribution patterns of the weathering crust and bedrock are similar, but the REE of the weathering crust is
relatively rich, the difference between light rare earth elements is large while the difference between heavy earth elements is smaller,
and the ratio of light and heavy rare earth elements in the SJC profile is larger than that of the QST profile; After normalization of rare
earth element chondrites, Eu in the SJC section shows a negative anomaly. Ce negative anomalies are observed in the upper and lower
part of the section. The QST profile shows negative Ce anomalies and negative Eu qnomalies. (4) The change in elemental content and
the correlation of Al-Ti, Al-Fe and Zr-Hf with elemental elements show that the overlying red soil is a result of weathering of the
underlying bedrock. The results of this study show that the elemental geochemical characteristics of the two profiles have good
inheritance of the bedrock and the weathering layer is the in-situ weathering product of the bedrock.

Geochemistry of the Upper Triassic Clastic Rocks in the Nanzhao Basin of Henan Province and Its Implications for Provenance

WANG Yanpeng，YANG Wentao*，ZHENG Deshun

2018, 24(2):  233. 

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The Triassic is the critical period when the Qinling Orogenic Belt was marked by a completely collisional orogeny. With the
amalgamation of the Yangtze and Qingling blocks and the North China Block along the Mianlue and Shangdan sutures, respectively, the
Qinling Orogenic Belt started to form and transformed from plate tectonic systems to intracontinental orogenic systems. The active
orogenies controlled the formation and evolution of the basins adjacent to the orogenic belt. Based on the geochemistry of clastic rocks,
the provenance and tectonic setting of the Upper Triassic from the Nanzhao Basin were investigated in this study. Results show that the
composition of provenance was mainly felsic igneous rocks of the upper crust. The source rocks experienced a moderate chemical
weathering, and the corrected chemical index of alternation (CIAcorr) values indicated that the provenance was formed in warm and
humid climate and in relatively active tectonic environments. Tectonic setting of the provenance in the Taishanmiao Formation was
mainly continental island arc and active continental margin, while the Taizishan Formation was continental island arc and passive
continental margin. According to the near-source depositional characteristics of the Nanzhao Basin and the evolutionary process of the
Qinling Orogenic Belt, we suggest that the Qinling Orogenic Belt and the southern margin of the North China Block are the important
provenances of the Nanzhao Basin during the Late Triassic. The provenance of the Taishanmiao Formation is mainly provided by the
basement of the North Qinling Belt, and the provenance of the Taizishan Formation is probably derived from the South Qinling Belt,
North Qinling Belt and the southern margin of the North China Block, with the recycling of sediments. The transition of the UpperTriassic provenance from the Nanzhao Basin is the response to the gradually enhanced thrusting of the Qinling Orogenic Belt during the
Late Triassic. This has a crucial significance to reconstruct the process of mountain building and uplifting of the Qinling Orogenic Belt
and the evolutionary process of basin-orogeny systems in adjacent basins.

Provenances of the Major Loess Deposits in Eastern China Based on Sr and Nd Isotopic Characteristics

ZHENG Li

2018, 24(2):  246. 

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The provenance study of the major loess deposits in eastern China can help understand the evolution since the late
Quaternary in this area. Nd and Sr isotopes are the most commonly used source tracers for atmospheric dusts. This work applies the
Sr-Nd isotope to trace the source of classical loess deposits in eastern China, including the Shandong Peninsula and its adjacent
coastal area, the loess deposits along the lower reaches of the Yellow River and the Xiashu loess deposits in the lower reaches of the
Changjiang. We found that the Sr-Nd isotope composition was different between the loess in eastern China and the loess on the
Chinese Loess Plateau, suggesting a different source region for the loess in eastern China. The Sr-Nd isotope data indicate that the
loess deposits in eastern China mainly came from the near source. The loess deposits in the Shandong Peninsula and its adjacent
coastal area show similar εNd values and 87Sr/86Sr ratios ranging from 0.7140 to 0.7155, which were blown from the Yellow River
sediments exposed on the floodplain and the shelf during glacial times. The loess in the lower reaches of the Yellow River show similar
Sr-Nd isotope values with the sediments in the floodplain of lower reaches of Yellow River, suggesting that the floodplain of lower
reaches of Yellow River was the major source for the loess in the lower reaches of the Yellow River. The Xiashu loess deposits show 87Sr/ 86Sr ratios ranging from 0.7194 to 0.7209, which is lower than that of modern sediments in the lower reaches of the Changjiang, and εNd
values ranging from -11.3 to -12.0. The source region of fine grains in Xiashu loess has not yet been determined and needs further
study. The formation of loess deposits in eastern China may be related to the desertification during the glacial climate since the middle
Pleistocene transition.

Experimental Study on Correlation between Soil Resistivity and Thermal Conductivity

LIU Ziwen, ZHANG Dan*, CHENG Jian

2018, 24(2):  251. 

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Four different types of soil were made by mixing Nanjing Xiashu soil and fine sand in different proportions. The resistivity
of soil with different water content was measured by four electrodes method. It was found that the resistivity of soil decreased with the
increase of water content and clay content. Meanwhile, the thermal conductivity of soil samples was tested by DRE thermal conductivity
apparatus, and it was found that the thermal conductivity increased with the increase of water content and sand content. It has been
verified that the soil resistivity and thermal conductivity are related to the physical properties of soil, such as saturation and porosity,
etc. By fitting the resistivity and thermal conductivity of the soil, a good exponential relationship was found. A mathematical model was
established to characterize the correlation between resistivity and thermal conductivity. This study provides the basis for the indirect
determination of the thermal conductivity of the soil by using the measured in-itu resistivity index.

Characteristics of Groundwater Chemistry and Its Spatio-Temporal Variation in Abandoned Mine in Eastern Xuzhou

PAN Yue, LIU Yong, XU Hongxia, ZENG Xiankui, WU Jichun

2018, 24(2):  257. 

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When the mine is closed, the changes of groundwater hydrodynamic conditions may cause groundwater pollution and greatly
threaten the environment. The abandoned mine in eastern Xuzhou was chosen in this study, and groundwater samples were collected for
chemical analysis on the basis of hydrogeological survey. The results showed that the hydrochemical types in Taiyuan Formation
Aquifer exhibited obvious zonation, the types of which changed gradually from HCO3·SO4-Ca and SO4-Ca·Mg in north-west to HCO3·
SO4-Ca·Mg and HCO3-Ca·Mg in south-east. With the mine being closed, the groundwater level rose and the hydrogeological
conditions changed, leading to the variations of groundwater chemical components. According to the analysis of the evolution of
groundwater hydrochemical characteristics, groundwater in the study area was affected by cation exchange and adsorption, and the
concentrations of calcium ions, magnesium ions and sulfate ions increased, while those of sodium ions and potassium ions decreased.

Characteristics and Developmental Mechanism of the the Early Cambrian Carbonate Gravity Flow Deposits in Platform Marginal Slope of the Northern Sichuan

LIAO Jijia, MA Sihao, LIAO Mingguang*，LIN Dan

2018, 24(2):  263. 

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Based on field survey, outcrop analysis and microscopic observbation, we report the basic characteristics of the carbonate
gravity flow in platform margin in the lower Cambrian Xiannvdong Formation of the Northern Sichuan Basin and address its
developmental mechanism in this paper. Results show that the Xiannvdong Formation typically developed an environment of diamictic
carbonate platform marginal slope in shallow water. The bottom of this formation is mainly composed of three rock types, i.e., silty
mudstones, bioclastic micritic limestones and algal limestones. According to the planar morphologies, two types of carbonate gravityflow deposits were classified, including nodular-like and brecciated. Based on the grain size and lithological variation of the gravity flow
sediments in outcrops, five developmental stages were divided, which show an obvious superposition relationship vertically. The grain
size of these sediments roughly changes from fine to coarse within sedimentary cycles, consistent with the regressive environment of the
Xiannvdong period in general. In the vicinity of the platform marginal slope, slide and slump events occurred due to the triggering of
geological events, e.g., earthquake and storm. The mound and shoal mass moved down along the slope, and some of the blocks migrated
and deposited here, which formed the brecciated carbonate gravity flow deposits. With the increasing injection of water, the amount of
sediment-water mixture and the decomposition of the material rose, and some of the mass were broken and flowed as similar forms of
debris flow along the slope, and then the debris transformed into carbonate gravity flow deposits with plastic rheological characteristics.
Then, these deposits might be reworked by bottom current or experienced corrosion from seawater after deposition to form two types of
nodular-like carbonate gravity flow sediments. In contrast, the brecciated carbonate gravity flow sediments were products of transportation
and short-distance slumping of mega unbroken carbonate mound mass. They are co-deposited with the nodular-like calcirudites.

Characteristics of Microscopic Pore Structures and Its Influencing Factors of the Qiongzhusi Formation Shales in the Southern Sichuan Basin

WANG Zhe, LI Xianqing*, QI Shuai, YAO Suping, WANG Feiyu

2018, 24(2):  273. 

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Microscopic pore structures of shale are an important factor influencing the storage capacity of shale gas reservoirs. To
evaluate the reservoir properties of the Lower Cambrian Qiongzhusi Formation shales in the southern Sichuan Basin, we investigate
genetic types of microscopic pores, characteristics of pore structures and its influencing factors in this paper, based on the data from
core and drilling samples. Multiple methods were applied, including scanning electron microscopy, field emission scanning electronmicroscopy with argon ion polishing, image J2x software analysis, low-temperature CO2 and N2 adsorption, and high-pressure mercury
injection experiments. Results show that the porosity of the Qiongzhusi Formation shales ranges from 0.25% to 5.80% with an average
of 2.49%. Multiple genetic types of pores are present in the shales, with the inter-granular pores being dominant and the intra-granular
pores, organic matter pores and micro-cracks being subdominant. The total surface porosity of the microscopic pores in the shales
ranges from 3.58% to 5.92%. The total pore volume of the shales ranges from 2.86×10-3 to 12.55×10-3 mL/g, and the total specific
surface area ranges from 2.727 to 21.992 m2/g. Their pore-size distribution mainly occurs in three ranges: 0.30~1.00 nm, 2.5~4.7 nm
and 55~70 nm. Micropores (<2 nm) and mesopores (2~50 nm) are the main reservoir storage space for shale gas. Types of pore structure
are mainly circular pores, wedge-shaped pores, parallel-plate pores and mixed pores. The porosity and total specific surface area of the
shales show positive correlations with TOC and abundance of brittle minerals. The micropore volume and specific surface area of shales
show positive correlations with TOC. The porosity, total pore volume and specific surface area of shales show negative correlations with
Ro and abundance of clay minerals.

Depositional Model for Contourites the Kelimoli Formation, Middle Ordovician, Zhuozishan Area  

LI Xiangdong, QUE Yi, HUAN Yaqi

2018, 24(2):  285. 

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Contourite is an important sedimentary type of traction current deposits in a deep-water environment. Although there has
been a lot of research on contourites, most studies focus on contour concurrent deposition in modern oceans by bathymetric
investigation and deep-sea drilling (DSDP, ODP and IODP). Following the implementation of the IODP (Integrated Ocean Drilling
Program) Expedition 339 (The Mediterranean outflow), the study of contourites has reached a new stage for analyzing the vertical and
lateral succession of contour drifts. However, there is still a great restriction on further study of contourites, especially on the
depositional model for contour currents because of the big gap between modern sea floor and stratigraphic records. This article is
focused on the ancient contour current deposits developed in the northwestern margin of the Ordos Basin, in Darriwilian Stage, Middle
Ordovician. Sedimentology analysis based on the detailed field work in shixiagu section, Hainan area in Wuhai city of Inner Mongolia
allows us to differentiate three vertical successions, i.e., the medium-to thin-bedded amalgamated limestone, the alternation of
limestone-mudstone unit and mudstone, and the striation mudstone is the notable characteristics in the lower, middle, and upper part of
the Kelimoli Formation, respectively. These three successions are proposed to represent the deposits of channel, levee, and basin in
deep-water environments where contour currents dominate. Thus, a conceptual model of deep-water channel-levee system for the
deposition of contour currents is developed from the geological records in the western Ordos Basin

Characteristics of the Tidal Sedimentation in the Eastern Bohai Sea and the Environmental Evolution since MIS4

CHEN Shanshan, WANG Zhongbo*, LI Rihui, MENG Xiangjun, CHEN Xiaohui, GUO Zhengyan

2018, 24(2):  297. 

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The typical tidal sedimentations have been discovered in the eastern of the Bohai Sea, which consists of the Laotieshan
Channel, the Liaodong Shoal tidal sand ridges, and the Bozhong Shoal tidal sand sheets. In this paper, the sedimentary features and the
seismic reflections of the tidal bodies in eastern Bohai Sea are analyzed based on the new high-resolution seismic data from the marine
geological survey and the comparison with water depth changes. Combined with the lithology, 14C age data, and stratigraphy of borehole
CD5, four stratigraphic sequences have been identified, including the fine sand strata of land facies of MIS4, the silt and clay strata of
nearshore facies of MIS3, the silty clay and fine sandy silt strata of land facies of MIS2, and the sand strata of marine facies of
Holocene. Furthermore, the sedimentary facies of the Holocene strata can be divided into nearshore, neritic, and tidal environment. The
analysis of the four sedimentary facies reveals the evolution of sedimentary environment since MIS4.