• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Morphology and features of Cambrian oncoids and responses to palaeogeography of the North China Platform

    2020-06-23 02:35:32EnZhaoXiaoMingXiangMeiShuJiangandTehseenZafar
    Journal of Palaeogeography 2020年2期

    En-Zhao Xiao ,Ming-Xiang Mei,Shu Jiang and Tehseen Zafar

    Abstract

    Keywords: Morphological classification, Microbial mat, Girvanella, Carbon and oxygen isotopes,Miaolingian series,North China

    1 Introduction

    As a significant type of carbonate grain, oncoids have attracted extensive attention from geologists for decades.Oncoids in the geological record are characterized as unattached, rounded, and mm- to cm-sized and commonly exhibit a micritic cortex consisting of more or less concentric and partially overlapping laminae around a bio- or lithoclastic nucleus (Jones and Renaut 1997;Shapiro et al. 2009; Flügel and Munnecke 2010; Han et al. 2015; Wang and Xiao 2018). Studies of oncoids have revealed that clear understanding of the formation mechanism, classification and microbial metabolism recorded by exquisite internal structures (Zhang et al.2013; Han et al. 2015; Wilmeth et al. 2015) can guide the reconstruction of palaeogeography and palaeoenvironments (Dahanayake 1977; Peryt 1983; Jones 1992,2011; Jones and Renaut 1997, 2010; Gradziński et al.2004; Védrine et al. 2007; Védrine 2008; Yang et al.2009, 2011; Flügel and Munnecke 2010; Zhang et al.2014a, 2014b, 2015; Wang and Xiao 2018). Previous studies usually noted that the oncoid nucleus is composed of biodetritus or carbonate debris (Peryt 1983;Tucker and Wright 1990; Riding 1991), which was captured and surrounded by calcareous particles during the growth processes of microorganisms or algal communities (Flügel and Munnecke 2010). In recent years,through further studies of potential biosignatures from geological records and microbial-mediated organomineralization, the discussion of oncoids, including definition,genesis, type characteristics, classification and positions within microbialites (Wang and Xiao 2018), has again become a major topic in sedimentology.

    Cambrian oncoids have been reported in the southern and eastern margins of the North China Platform(Zhang et al. 2014a, 2014b), including western Henan Province (Zhang et al. 2015; Qi et al. 2016) and western Shandong Province of China. However, very few studies have examined the oncoids in the Cambrian Miaolingian Series that are exposed in the northern margin of the North China Platform in detail. Therefore, this study was conducted to provide an extensive range of reference materials for the latter. In total, 240 representative oncolitic limestone samples were collected from Wuhai,Diaoquan, Xiaweidian, Sandaogou, Fuzhou Bay, and Jinzhou Bay sections (Figs. 1, 2). The standard carbonate microfacies analysis shows morphological differentiation of oncoids in the study area. The study aims to demonstrate the origin of these oncoids and analyze possible factors that led to their morphological differentiation through comparative studies in a large region using sedimentological and geochemical methods.

    2 Materials and methods

    Field observations were conducted, involving measuring and sampling the Cambrian Miaolingian Series exposed in six sections in the North China Platform (Fig. 1).Stratigraphic successions were reconstructed based on field and laboratory studies. Two hundred fouty fresh,representative oncolitic limestone samples were collected from the Xuzhuang and Zhangxia formations, i.e.,40 from each section. Microfacies observations of polished samples and thin sections (under crosspolarized light (XPL) and plane-polarized light (PPL))were performed to identify the main lithological and biological components.

    Fig. 1 Cambrian outcrops in the North China Platform and the locations of studied sections (red stars). A-Wuhai section: Gandel Mountain,Wuhai City, Inner Mongolia Autonomous Region, China; B-Diaoquan section: Diaoquan village, Lingqiu county, Datong City, Shanxi Province,China; C-Xiaweidian section: Xiaweidian village, Mentougou district, Beijing, China; D-Sandaogou section: Sandaogou village, Suizhong county,Huludao City, Liaoning Province, China; E-Fuzhou Bay section: Fuzhou Bay town, Jinzhou district, Dalian City, Liaoning Province, China; F-Jinzhou Bay section: Dalian City, Liaoning Province, China. Topographically, the western margin of Yimeng landmass was steeper than the eastern during the Cambrian, which means that the Cambrian successions in the Wuhai section is related to a deeper water environment than those of the other five sections(Feng 2004)

    Fig. 2 Lithology and sedimentary facies of the Cambrian Miaolingian Series in the six studied sections (Peng et al. 2012; Xiao et al. 2017a, 2017b).Among these sections, Wuhai section has the thinnest succession, with a small thickness of limestone, and a large thickness of mudstone and dark-green organic muddy-sandy shale, which indicates deep-water deposition. The other five sections in the east reveal similar lithological variations and comparable boundaries. The Xuzhuang Formation shows a transition from red shale associated with tidal flats to oolitic limestone associated with grain banks (Ma et al. 2017; Xiao et al. 2017a, 2017b; Xiao et al. 2019a). Sedimentary facies of the Zhangxia Formation display cyclic changes from nongrain bank to grain bank and from deep-water to shallow-water, demonstrating shallowing-upward trends (Xiao et al.2017a, 2017b).The oncoids mainly developed in the Xuzhuang and Zhangxia formations

    Among these samples, 10 from each section, i.e., a total of 60 samples were selected, and were prepared into 60 small cubes with fresh broken surfaces as well as 60 polished thin sections, which were observed under a FEI Quanta 200F scanning electron microscope (SEM). Meantime, the 60 polished thin sections were gold-coated for secondary electron imaging.Semiquantitative elemental analyses of submicronsized spots during SEM observations were attained through energy dispersive X-ray spectroscopy (EDX).The voltage of the EDX element analysis was 10.0 kV,and the current pulse ranged from 19.83 kcps to 42.58 kcps.

    Another 30 samples, i.e., 5 from each section, were microdrilled on their fresh surface to prepare microsamples for carbon and oxygen isotope analyses. The micro-sampling process was taken under a microscope to avoid calcite veins and neomorphic processes. Isotopic compositions (δ13C and δ18O) were measured by a Thermo Scientific Delta V Advantage continuous-flow isotope ratio mass spectrometer. The results are presented in delta (δ) notation relative to the Vienna Pee Dee Belemnite (VPDB) standard. In addition, the precision of the carbon and oxygen isotopic ratios for duplicate analyses was better than 0.1%. The bulk mineral compositions of the samples were determined by XRD analyses, which were performed on prepared powder samples using the Bruker D2 PHASER instrument. All geochemical analyses of oncolitic limestone samples were performed in the State Key Laboratory of Oil and Gas Geology and Exploitation, Chengdu University of Technology, China.

    A total of 200 oncoids from each section were randomly selected and observed under a microscope to identify oncoid types as well as their proportions in different sections.

    3 Results

    3.1 Macroscopic characteristics of oncoids

    The studied oncoids mainly developed in shallow-water environments. They occur within oolitic limestones(Fig. 2), which range in thickness from approximately 0.3 m to 5 m, and are composed of layered limestone interbedded with thin micritic limestone layers. The oncoids are ellipsoidal or elongated in shape, with the long axis approximately 0.3-2.3 cm long (Table 1;Fig. 3).

    These oncoid-bearing beds are relatively thin, i.e., 0.3 m thick in the Wuhai section and 2.2 m thick in the Diaoquan section, respectively. In contrast, they are much thicker in the other four sections, i.e., 3.75 m thick in the Xiaweidian section, 4.5 m thick in the Sandaogou section, 5.2 m thick in the Fuzhou Bay section, and 4.9 m thick in the Jinzhou Bay section, respectively(Table 1).

    3.2 Microscopic characteristics of oncoids

    Microscopic observation shows that the oncoids grow together with ooids in the studied sections. The individual oncoids are circular to subcircular in shape and vary in size. Most oncoids contain a nucleus, which is typically composed of dark micrite, trilobite debris or echinoderm debris. In addition, most oncoids are characterized by alternating light and dark laminae and can be thought of as spherical stromatolites (Logan et al. 1964). Petrographically, the light laminae are composed of microspar, while the dark laminae are composed of dark micrite. In addition, filamentous cyanobacterial fossils,particularly Girvanella, are observed in the cortex and inside the interior laminae of oncoids.

    Based on the oncoid morphology, including the internal structure revealed by petrography, development of nucleus and laminae, location of nucleus, and other morphological features, the oncoids are divided into six varieties as follows: type 1, concentric fine-laminar oncoids; type 2, concentric rough-laminar oncoids;type 3, lateral-growth oncoids; type 4, multicore oncoids; type 5, flaggy oncoids; and type 6, thincortex oncoids.

    3.2.1 Type 1, concentric fine-laminar oncoids

    Concentricfine-laminar oncoids are the most common type of oncoids documented in geological records (Li et al.2000;Schaefer et al. 2001;Shi and Chen 2006;Reolid and Nieto 2010; Yang et al. 2011; Wang and Xiao 2018). Based on microscopic observations, this type is circular or elliptical in shape, with obvious nuclei and relatively smooth edges (Fig. 4a), and contains a large number of 50-μm-thick concentric laminae, which are highly-distinct and in light-and-dark color. Additionally,filamentous microbial fossils are observed inside the dark laminae and between the light and dark laminae at a high magnification. They show typical features of Girvanella, i.e., a dark-micrite sheath and microspar interior (Fig. 4b) (Riding 2011; Xiao et al. 2018),which are intertwined with each other inside the oncoid laminae (Fig. 4b).

    Except in the Wuhai and Diaoquan sections, type 1 oncoids are observed with a relatively large spatial distribution and make up a large proportion among all oncoid types in the Jinzhou Bay (73%, 146 in 200), Fuzhou Bay(79%, 158 in 200), Sandaogou (72%,144 in 200) and Xiaweidian (56.5%, 113 in 200) sections.

    Table 1 Field observation characteristics of various oncoids in the Cambrian Miaolingian Series, North China Platform

    3.2.2 Type 2, concentric rough-laminar oncoids

    Concentric rough-laminar oncoids have characteristics similar to those of type 1 oncoids containing concentric laminae (Han et al. 2015). However, the present study classifies them as two independent categories for the following reasons: (1) individual type 2 oncoids are noticeably smaller, and their concentric laminae are very sparse (Fig. 4c); (2) the concentric laminae of type 2 oncoids display light-dark differentiation, with their single lamina being much thicker than that in type 1 oncoids (Fig. 4d); (3) the nucleus volume of type 2 oncoids occupies a larger proportion of the oncoid than does that of type 1 oncoids (Fig. 4c); and (4) Girvanella is absent in the light laminae but present and intertwined in the dark laminae in type 2 oncoids (Fig. 4d).Among the six measured sections, type 2 oncoids are most abundant in the Diaoquan (14%, 28 of 200) and Xiaweidian (33%, 66 in 200) sections, and accounts for 5% (10 of 200) in the Wuhai section. However, the proportions drop to 1% (2 in 200) in the Sandaogou,Fuzhou Bay and Jinzhou Bay sections.

    3.2.3 Type 3, lateral-growth oncoids

    Lateral-growth oncoids show thick alternating light and dark laminae, smooth edges, a high degree of regularity in individuals, and nuclei usually composed of trilobite debris, making these oncoids analogous to type 1 oncoids microscopically.

    The differences are that the majority of lateral-growth oncoids are larger than type 1 oncoids, with the nucleus not located in the center (Fig. 5a). The laminae on one side of the nucleus are thick and well-developed,whereas they are thin and poorly-developed on the other side (Fig. 5b). Some dispersed sparry calcite microcrystals are observed inside the laminae, mostly on the well-developed side (Fig. 5c). Girvanella filaments are observed inside the dark micrite with an intertwined arrangement (Fig. 5b) or aligned parallel to the laminae with an ideal orientation (Fig. 5c). Type 3 oncoids are observed in the Jinzhou Bay(23%,46 in 200),Fuzhou Bay(19%,38 in 200)and Sandaogou(19%,38 in 200)sections respectively.

    3.2.4 Type 4, multicore oncoids

    Each multicore oncoid typically contains more than two nuclei. They are irregular in shape, mainly long and narrow but occasionally round to subround, and can reach large sizes. The nucleus is often made up of trilobite debris or ooids. The inner laminae near the nucleus are usually concentric (Fig. 6a, b). The relatively outer laminae are composed of light microspar and dark micrite. Typical Girvanella filaments are observed inside the dark micritic bands(Fig. 6c, d).

    Fig. 3 Macroscopic characteristics of oncoids in the Cambrian Miaolingian Series, North China Platform. a Oncoids from the Xuzhuang Formation,Wuhai section; b Oncoids from the Zhangxia Formation, Diaoquan section; c Oncoids from the Xuzhuang Formation, Xiaweidian section; d Oncoids from the Zhangxia Formation, Sandaogou section; e Oncoids from the Zhangxia Formation, Fuzhou Bay section; f Oncoids from the Zhangxia Formation,Jinzhou Bay section

    Notably, multicore oncoids are recognized and exhibit similar morphological characteristics in the Diaoquan and Sandaogou sections. However, in the Sandaogou section, they contain light and dark laminae and are analogous to type 1 oncoids (Figs. 6a,4a), while in the Diaoquan section, the light and dark laminae are poorly developed in the multicore oncoids and are comparable to those of type 2 oncoids (Figs. 6b, 4c).

    3.2.5 Type 5, flaggy oncoids

    Fig. 4 Microscopic characteristics of types 1 and 2 oncoids. a A type 1 oncoid from the Sandaogou section, characterized by concentric finelaminar structure and clear nucleus (made up with trilobite debris and dark micrite); b Local magnification of a, showing the interlaced and intertwined calcified filamentous fossils of Girvanella; c A type 2 oncoid from the Diaoquan section, characterized by a concentric rough-laminar structure with lower frequency alternation than that in type 1; d Local magnification of c, showing the micrite conglomeration and rough edges of the oncoid.Girvanella fossils can be observed inside the dark micrite laminae with a disordered winding occurrence

    Flaggy oncoids differ greatly from other oncoid varieties in shape (Fig. 7a). Their composition is fairly simple and predominantly composed of a nucleus and surrounding dark micrite layer. The nucleus is made up of slender trilobite debris (Fig. 7a). Only a small number of flaggy oncoids show laminar structures. Most flaggy oncoids are irregular in shape and are much smaller in size than other oncoids. Girvanella filaments are observed inside the dark micritic cortex(Fig. 7b).

    Flaggy oncoids are only observed in the Wuhai, Diaoquan and Xiaweidian sections. Importantly, the numbers of flaggy oncoids in these sections differ greatly. The proportion in the Xiaweidian section is only 5.5% (11 in 200) but reaches 26% (52 in 200) in the Diaoquan section and 42% (84 in 200) in the Wuhai section.

    3.2.6 Type 6, thin-cortex oncoids

    This type of oncoid is typically determined as thincortex oncoids (Han et al. 2015). They are irregularly shaped and sized (Fig. 7c), with a long axis of 4-6 mm long, while the short axis is around 800 μm long.The nuclei are made up of ooids, trilobite debris and dark micrite grains and are surrounded by a uniform thin dark micritic cortex. Further observations via high-power microscopy reveal the presence of Girvanella (Fig. 7c) inside the dark micrite in these oncoids.

    Thin-cortex oncoids are widely distributed in the Wuhai, Diaoquan, Xiaweidian and Jinzhou Bay sections,with different proportions and sizes. The Jinzhou Bay and Xiaweidian sections have minute proportions (3%, 6 in 200, and 5%, 10 in 200, respectively) of the total number of oncoids, with measured sizes of approximately 800 μm long. However, the proportion reaches 45% (90 in 200) in the Diaoquan section and 53% (106 in 200) in the Wuhai section, with sizes of 4-6 mm long in both sections.

    Fig. 5 a A type 3 oncoid, characterized by concentric laminae, an off-center nucleus and lateral growth; b Local magnification of a, showing the disordered Girvanella fossils with intertwined arrangement; c Local magnification of a,showing the directional arrangement of Girvanella fossils

    3.3 Ultramicroscopic characteristics of oncoids and the mineral composition of lamina

    According to SEM observations, the dark and light laminae of oncoids exhibit different ultrastructures(Fig. 8a, b). The light laminae are composed of CaCO3microspars (Fig. 8a-c, g), showing welldeveloped cleavage and relatively smooth surfaces.The dark laminae are composed of micrite, whose main component is also CaCO3, showing a distinct morphological structure (Fig. 8a, d, f). The micrite is similar to microbially-derived carbonate mud, which is consistent with the findings of previous studies(Perry 1999; Flügel and Munnecke 2010; Guido et al.2012; Edgcomb et al. 2013; Ka?mierczak et al. 2015;Gischler et al. 2017; Yu et al. 2019). Moreover, two kinds of pyrite particles are observed in the micrite(Fig. 8e): ordinary massive pyrite and framboidal pyrite. The framboidal pyrite is associated with sulfatereducing bacteria and stimulates the microbial metabolism of carbonate precipitation, which therefore indicates a microbial origin of the studied oncoids(Baumgartner et al. 2006; Xiao et al. 2017c, 2018,2019b).

    3.4 Geochemical analysis

    In this study, the oncolitic limestones are similar in lithology and strata position; however, the microscopic analysis reveals that oncoids from different sections differ obviously in terms of variety and abundance. To examine whether these differences are linked to the Cambrian palaeogeographic settings of the North China Platform,XRD and carbon and oxygen isotopic analyses were conducted on the samples of oncolitic limestone collected from the six sections.

    3.4.1 XRD

    Fig. 6 Microscopic characteristics of type 4 oncoids. a A type 4 oncoid from the Sandaogou section, characterized by a concentric laminar structure and two nuclei (made up of trilobite debris and dark micrite); b A type 4 oncoid from the Diaoquan section, characterized by a concentric rough-laminar structure, unsmooth edges and two nuclei; c Local magnification of a, showing typical Girvanella fossils inside the dark micritic laminae with an intertwined arrangement;d Local magnification of b, showing typical Girvanella fossils inside the dark micritic laminae

    Five samples of oncolitic limestone were taken from each section of the Cambrian Miaolingian Series, specifically, from the Xuzhuang and Zhangxia formations,and XRD analysis was performed to determine the basic mineral components (Table 2). The results show that the main mineral component of the oncolitic limestone in the six sections is calcite; however, there are several differences in other mineral components,as follows. (1) In the Jinzhou Bay, Fuzhou Bay, Sandaogou and Xiaweidian sections, the content of quartz in the oncolitic limestone samples is 1%-2%, while in the Wuhai and Diaoquan sections, this value is markedly higher, reaching 9%. (2) Feldspar is not observed in the samples from the Jinzhou Bay and Fuzhou Bay sections, and its content in the Sandaogou and Xiaweidian sections is extremely low. Conversely, it has relatively higher content in the Wuhai and Diaoquan sections, reaching 4%. (3) Although dolomite occurs in all six sections, its content is much higher in the Wuhai and Diaoquan sections than in the other sections. (4) Additionally, the contents of pyrite and clay minerals are low and exhibit no obvious regularity.

    3.4.2 Carbon and oxygen isotopes

    Carbon and oxygen isotopic compositions of marine limestone can reflect the sedimentary environment (Li et al. 2013, 2017). Therefore, carbon and oxygen isotopic analysis was applied to 30 oncolitic limestone samples to further interpret the depositional environments of oncoids. The results show that the mean δ13C values in the Xuzhuang and Zhangxia formations decrease from west to east (Table 3). The mean δ13C value of the Xuzhuang Formation in the Wuhai section is ?0.302‰VPDB, which is higher than those of the Xuzhuang Formation in the Xiaweidian section (?0.788‰ VPDB),Fuzhou Bay section (?0.890‰ VPDB) and Jinzhou Bay section (?0.716‰ VPDB) (Table 3). In addition, the mean δ13C values of the samples from the Zhangxia Formation also exhibit the same pattern, i.e., the mean value of ?0.626‰ VPDB in the Diaoquan section (west) is higher than that of ?0.796‰ VPDB in the Sandaogou section (east) (Table 3; Fig. 9).

    The δ18O values in the six sections also exhibit apparent variations. The mean δ18O values in the western sections are higher than those in the eastern sections. (1)The value of the Xuzhuang Formation decreases from?6.664‰VPDB in the Wuhai section to ?8.758‰VPDB in the Xiaweidian section, to ?9.712‰ VPDB in the Fuzhou Bay section, and to ?10.404‰ VPDB in the Jinzhou Bay section (Table 3; Fig. 9). (2) The value of the Zhangxia Formation in the Diaoquan section is?6.65‰ VPDB, which is higher than that of ?7.854‰VPDB in the Sandaogou section (Table 3).

    Fig. 7 a A type 5 oncoid, marked by an irregular shape with a clearly external enveloping micritic cortex and the nucleus; b Local magnification of a, showing the typical Girvanella fossils inside the dark micritic cortex. Some spherical cross-sections can be observed; c A type 6 oncoid,marked by a larger individual size, irregular shape and thin cortex. The local magnifications show the two arrangements of Girvanella fossils,which are parallel and intertwined

    4 Discussion

    The study of ancient oncoids can indicate changes in depositional conditions and the controlling effects of microbial activities on their formation; therefore, the results are important for reconstructing palaeoclimate,palaeoenvironments, sea-level fluctuations and chemical conditions in sedimentary environments (Peryt 1983;Védrine et al. 2007; Védrine 2008; Yang et al. 2011;Zhang et al. 2014a,2014b; Zhou et al. 2017).

    4.1 Classification and biogenicity of oncoids

    The classification of oncoids has not been comprehensively interpreted and is considered as an important direction of oncoids study (Dahanayake 1977; Peryt 1983).The macro- and microcharacteristics and the mineral compositions of oncoids are influenced by the physical,chemical and biological conditions of the aquatic environment and microbial activity. The current classifications include: (1) morphological classification (Yang et al. 2011); (2) mineral component classification (Flügel and Munnecke 2010); and (3) formational environment classification (Védrine et al. 2007; Védrine 2008). In this study, the classification of oncoids on the basis of morphological characteristics is applied.

    The morphological similarities of the oncoids reported in this study compared to those of previous works on oncoids in similar or different environments suggest that the oncoids in the Cambrian Miaolingian Series, North China Platform, are microbial in origin (Table 4) (Krumbein and Cohen, 1977; Zeng et al, 1983; Gerdes et al,1994;Davaud and Girardclos,2001;Flügel and Munnecke,2010;Jones,2011;Han et al,2015;Wang and Xiao,2018).Typical filamentous cyanobacterial fossils, including Girvanella (Riding 2011; Xiao et al. 2018), are abundant among the oncoids in this study (Figs. 4-7), which is clearly related to microorganisms and indicates that the origin of these oncoids is associated with the calcification of cyanobacteria-dominated microbial communities and the biodegradation of heterotrophic bacteria. The framboidal pyrite particles were produced by the sulfate reduction reaction dominated by sulfate-reducing bacteria (Fig.8e)(Xiao et al.2017c,2019b).

    Fig. 8 SEM and EDX analyses of the light and dark laminae. a Various mineral structures of oncoids, with the two points of EDX analysis marked;b A cortex showing a bimineralic structure; c Local magnification of b, showing calcite crystals in the light laminae; d Local magnification of b,showing amorphous calcium carbonate mud in the dark laminae; e Two kinds of pyrite particles observed inside the oncoids: framboidal pyrite(pink arrows)and ordinary massive pyrite(yellow arrows);f, g EDX results of the two analyzed points in a

    As concluded in the above discussion, the oncoids in this study are predominantly composed of calcite. The alternation of light and dark laminae is associated with different microstructures of the calcium carbonate minerals (Fig. 8a, b). The light laminae are composed of calcite microspar, whereas the dark laminae are mainly composed of amorphous calcium carbonate (ACC),which is inferred to be the product of Girvanella calcification (Pratt 2001) and can be comparable to previously documented examples of ACC (Jones and Peng 2012;Diaz et al., 2017). Similarly, the discovery of Girvanella inside oncoids and the ultrastructure of the dark micrite laminae, including the presence of framboidal pyrite, are likely related to cyanobacteria-dominated calcification and the involvement of heterotrophic bacteria in the promotion of calcium carbonate precipitation (Dupraz et al. 2009).

    4.2 Response to palaeogeography and palaeoenvironment

    The formation process of an oncoid can be inferred from its structure and form, including the nucleus development, concentric laminae, and cortex morphological characteristics. It is controlled by palaeogeographic and palaeoenvironmental factors, such as the water and atmospheric chemical conditions, as well as sea-level changes (Védrine et al. 2007; Védrine 2008).Therefore, the study of the morphology and origin of oncoids may provide remarkable insights for reconstructing palaeogeography and palaeoenvironments(Peryt 1983; Yang et al. 2011; Zhang et al. 2013, 2015;Zhou et al. 2017).

    The oncoids from the six sections developed during approximately the same period.This study based on sedimentology and stratigraphy, in combination with previous reports on the Cambrian palaeogeography of the North China Platform (Feng 2004; Ma et al. 2017),clarifies that the thicknesses of the oncolitic limestone in the two sections of nearshore environment (0.3 m thick in the Wuhai section and 2.2 m thick in the Diaoquan section) are obviously thinner than those in the other four sections of offshore setting (Table 1). Additionally,macroscopic observations in the field show that the Xuzhuang Formation in the Diaoquan section and Wuhai section has more crossbeds and scouring surfaces. These characteristics can be explained by the fact that sea-level change on a steeper slope resulted in more rapid environmental changes over time, which caused the smaller thicknesses of the oncolitic limestone in the Wuhai and Diaoquan sections.

    Table 2 XRD analysis results showing the mineral compositions and contents of the oncolitic limestone from the Cambrian Miaolingian Series, North China Platform

    In addition, there are obvious differences in the types and proportions of each type of oncoids in each section(Fig. 10). In total, 200 oncoid individuals were randomly selected from each section for microscopic observation.Based on their morphology, six types of oncoids were classified, and their proportions in each section were determined. The results demonstrate that the types andproportions of different types of oncoids have the following patterns. (1) Oncoids with well-developed laminae (type 1, concentric fine-laminar oncoids, and type 3,lateral-growth oncoids)mostly develop in sections of offshore environment (Fig. 10a). (2) Oncoids with poorlydeveloped laminae (type 2, concentric rough-laminar oncoids) and irregular oncoids (type 5, flaggy oncoids,and type 6, thin-cortex oncoids) predominantly occur in the two sections of nearshore setting (Wuhai and Diaoquan sections) (Fig. 10a). The proportions of the most abundant oncoid varieties (types 5 and 6) are 95% and 71% in the Wuhai and Diaoquan sections, respectively.In contrast, in the Jinzhou Bay section, type 6 oncoids account for only 3% (Fig. 10a). (3) Type 4 oncoids only occur in the Zhangxia Formation in the study area and comprise only a small proportion (14% in the Diaoquan section and 8% in the Sandaogou section).

    Table 3 Carbon and oxygen isotopes of the oncolitic limestone samples from the Cambrian Miaolingian Series, North China Platform

    Fig. 9 C-O isotopic data for the oncolitic limestone from the Cambrian Miaolingian Series, North China Platform. The progressive decreasing trend of carbon and oxygen isotopic data from west to east can be obviously observed

    These clear patterns can be summarized as follows.Oncoids with fine laminae, clear cores and regular shapes exist in almost all offshore sections, and in contrast, oncoids with poorly-developed laminae and irregular shapes occur in nearshore sections (Fig. 10a). These patterns are also perceptibly associated with the main mineral compositions (Table 2; Fig. 10b, c) and the carbon and oxygen isotopic compositions (Table 3; Figs. 9,10d, e) of the oncoids in different sections. The XRD results confirm that the proportions of quartz and feldspar in the two nearshore sections (i.e., the Wuhai and Diaoquan sections) are significantly higher than those of the offshore sections (Table 2; Fig. 10b, c), which suggests that the carbonate sediments contain more terrigenous clasts. The presence of dolomite indicates the occurrence of dolomitization (burial, evaporation, etc.) caused by the shallowing depositional environment during the process of relative sea-level fall (Fig. 2) (Kendall and Schlager 1981; Hardie 1987; Xiao et al. 2017c). The occurrence of detrital quartz and feldspar signifies the input of terrigenous clasts during the deposition of the limestone and indicates that the depositional environment of the oncolitic limestone was characterized by shallow water and offshore conditions.

    The results of the isotopic study show that the carbon and oxygen isotope values exhibit a decreasing trend from west to east (Table 3; Fig. 10d, e). The δ18O and δ13C trends can be further explained as signifying the depositional environment changing from west to east during the same period in the North China Platform.This observation also confirms the macroscopic sedimentology and stratigraphic inference that the depositional environment of Wuhai and Diaoquan sections differed from that of Xiaweidian, Sandaogou, Fuzhou Bay and Jinzhou Bay sections (Table 1; Figs. 1, 2). The results are consistent with the palaeogeographic conditions of the sections and signify that the nearshore sections are dominated by higher carbon and oxygen isotopic values and that the offshore sections are dominated by lower isotopic values. This isotopic trend reflects geochemical changes related to differences in the depositional environments of the six sections, which may have been controlled by terrigenous inputs. Furthermore, the variations in the palaeoenvironmental conditions had a noticeable impact on the occurrence of oncoids in different sections. For example, types 2, 5 and 6 oncoids are the main oncoid varieties produced in the nearshore sections, whereas types 1 and 3 oncoids are the main types produced in the offshore sections(Fig. 10a-c).

    These features are evident in the morphological characteristics of two groups of oncoids from the Zhangxia Formation in the Diaoquan and Sandaogou sections.Multicore oncoids (type 4) only occur in these two sections (Fig. 10a). In the Sandaogou section, the laminae of multicore oncoids are distinct, and the oncoid morphology is irregular due to the multiple nuclei and theinner and outer laminae in the cortex of these oncoids,whereas in the Diaoquan section, the inner laminae are relatively rough, with an extremely irregular cortex (Fig.6a, b). Additionally, the closer location of these oncoids related to the ancient Yimeng landmass resulted in a greater influence of terrigenous debris, greater salinity and higher overall topography. These factors resulted in a shorter time required for the development of cyanobacteria (Girvanella)-dominated microbial mats and caused the formation of oncoids with less-exquisite laminae and less-regular shapes (Fig. 10a). In contrast, the offshore sections are featured by a more favorable environment with less interference from terrigenous debris and a gentler terrain, which provided a stable environment for cyanobacteria (Girvanella)-dominated microbial mats and promoted oncoids with well-developed laminae and regular shapes.

    Table 4 Morphological classification of oncoids from the Cambrian Miaolingian Series in the study area

    5 Conclusions

    1) Six Cambrian sections in the North China Platform contain exquisitely preserved oncoids with different shapes in the Xuzhuang and Zhangxia formations of the Miaolingian Series. Based on the morphologies and internal structures revealed by microscopy, the oncoids can be divided into six types: type 1, concentric finelaminar oncoids; type 2, concentric rough-laminar oncoids; type 3, lateral-growth oncoids; type 4, multicore oncoids; type 5, flaggy oncoids; and type 6, thin-cortex oncoids.

    2) The morphological and ultrastructural characteristics and XRD results of the oncoid samples reveal the presence of carbonate minerals, predominantly calcite.SEM observations of the oncoid microstructure indicate that the light laminae are composed of calcite microspar and that the dark laminae are composed of ACC. Girvanella fossils and framboidal pyrite can be found inside oncoids. These observations suggest a biogenic origin of the Cambrian oncoids exposed in the North China Platform. These oncoids are inferred to have formed through the interaction between cyanobacteria and heterotrophic bacteria (sulfate-reducing bacteria) inside microbial mats.

    Fig. 10 a Types and proportions of oncoids in different sections, with a total of 200 oncoids from each section randomly selected and observed under a microscope; b and c Approximate positions of different sections relative to the Yimeng landmass during different periods (Meng et al.1997; Feng 2004); d and e Variation trend of C-O isotopic values from west to east. MMC: Main mineral component; Q: Quartz; Pl: Potassium feldspar;C:Calcite;D:Dolomite;P:Pyrite;Cm:Clay minerals

    3) The occurrence of detrital quartz and feldspar in the oncolitic limestone in the Cambrian Xuzhuang and Zhangxia formations signifies the input of terrigenous clasts. The presence of small amounts of dolomite suggests a shallowing depositional environment during relative sea-level fall. The carbon and oxygen isotopes further imply that the formational environments of the oncolitic limestone varied spatially in the study area.The oncoids in nearshore environments were significantly influenced by the terrigenous input, and the steeper terrain resulted in relatively rapid changes in accommodation space during sea-level changes, resulting in rougher oncoid growth (rough and indelicate laminae,uneven cortex, and irregular shape). In contrast, the oncoids that developed in offshore sections were less affected by terrigenous factors, resulting in an environment favorable for the production of exquisite oncoids in cyanobacteria (Girvanella)-dominated microbial mats in a stable carbonate platform that was comparatively flat in the east.

    Abbreviations

    ACC: Amorphous calcium carbonate; EDX: Energy dispersive X-ray spectroscopy; MMC: Main Mineral Component; PPL: Plane-polarized light;SEM: Scanning electron microscopy/microscope; VPDB: Vienna pee dee belemnite; XPL: Cross-polarized light; XRD: X-ray diffraction

    Acknowledgements

    We gratefully acknowledge Prof. Zeng-Zhao Feng for the critical review of the earlier version of the manuscript. We are also thankful for the help from Dr. Muhammad Riaz and Dr. Khalid Latif in the field work.

    Authors’ contributions

    EZX proposed the viewpoint, carried out the analysis, and wrote the manuscript. MXM instructed the field work. SJ instructed the manuscript writing. TZ improved the language. All authors read and approved the final manuscript.

    Funding

    National Natural Science Foundation of China (Nos. 41472090 and 40472065).

    Availability of data and materials

    The data used to support the findings of this study are available from the corresponding author upon request.

    Competing interests

    The authors declare that they have no competing interests.

    Author details

    1School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China.2Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education and Faculty of Earth Resources, China University of Geosciences (Wuhan), Wuhan 430074, China.3Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.4Institute of Geology, University of the Punjab, Lahore 54590, Pakistan.

    Received: 15 May 2019 Accepted: 16 January 2020

    少妇猛男粗大的猛烈进出视频| 日日啪夜夜爽| 精品酒店卫生间| 熟女电影av网| www.色视频.com| 久久99热这里只频精品6学生| 中文乱码字字幕精品一区二区三区| 三上悠亚av全集在线观看| 国产精品不卡视频一区二区| 只有这里有精品99| 夫妻午夜视频| 少妇 在线观看| 涩涩av久久男人的天堂| 国产有黄有色有爽视频| 久久久久久伊人网av| 日日摸夜夜添夜夜爱| 性色av一级| 久久久欧美国产精品| 交换朋友夫妻互换小说| 亚洲精品色激情综合| av国产久精品久网站免费入址| 亚洲国产成人一精品久久久| 伦理电影大哥的女人| 草草在线视频免费看| 日本av手机在线免费观看| a级毛片黄视频| 久久久久久久亚洲中文字幕| 人成视频在线观看免费观看| 国产成人精品婷婷| 国产成人aa在线观看| 欧美97在线视频| 日本免费在线观看一区| 久久久国产一区二区| 人妻人人澡人人爽人人| 国产又爽黄色视频| 欧美精品一区二区大全| 精品一区在线观看国产| 欧美丝袜亚洲另类| 在线精品无人区一区二区三| 99热国产这里只有精品6| 中国国产av一级| 欧美日韩av久久| 天天影视国产精品| 日韩人妻精品一区2区三区| 午夜激情久久久久久久| 下体分泌物呈黄色| 97超碰精品成人国产| 亚洲av中文av极速乱| 亚洲欧洲日产国产| 麻豆精品久久久久久蜜桃| 久久久欧美国产精品| 1024视频免费在线观看| 多毛熟女@视频| 人妻少妇偷人精品九色| 免费在线观看完整版高清| 亚洲精品久久久久久婷婷小说| 夫妻午夜视频| 亚洲av综合色区一区| 亚洲,欧美,日韩| 街头女战士在线观看网站| 国产日韩一区二区三区精品不卡| 如何舔出高潮| 国产男女超爽视频在线观看| 色吧在线观看| 亚洲欧美中文字幕日韩二区| 熟女av电影| 亚洲精品,欧美精品| 一级毛片电影观看| 少妇熟女欧美另类| 宅男免费午夜| 中文字幕人妻熟女乱码| 毛片一级片免费看久久久久| 国产色爽女视频免费观看| 最近中文字幕2019免费版| www.色视频.com| av电影中文网址| 午夜福利视频在线观看免费| 男的添女的下面高潮视频| 国产亚洲午夜精品一区二区久久| 丰满饥渴人妻一区二区三| 人人妻人人爽人人添夜夜欢视频| 亚洲美女视频黄频| 成人无遮挡网站| 精品人妻一区二区三区麻豆| 永久免费av网站大全| 国产国拍精品亚洲av在线观看| 成年人午夜在线观看视频| 日韩一区二区视频免费看| 伊人亚洲综合成人网| 国产激情久久老熟女| 亚洲人与动物交配视频| 99国产精品免费福利视频| 哪个播放器可以免费观看大片| 免费观看无遮挡的男女| 又黄又爽又刺激的免费视频.| 日本免费在线观看一区| 欧美另类一区| 一本大道久久a久久精品| 熟妇人妻不卡中文字幕| 在线天堂最新版资源| 最近最新中文字幕免费大全7| 美女xxoo啪啪120秒动态图| 一本久久精品| 欧美精品高潮呻吟av久久| 国产不卡av网站在线观看| 免费高清在线观看视频在线观看| 免费观看无遮挡的男女| 久久久国产欧美日韩av| 久久久亚洲精品成人影院| 国产视频首页在线观看| 中文字幕制服av| 成人免费观看视频高清| 国产国拍精品亚洲av在线观看| 狂野欧美激情性bbbbbb| 十八禁网站网址无遮挡| 七月丁香在线播放| 国产精品久久久久成人av| 巨乳人妻的诱惑在线观看| 成人毛片60女人毛片免费| 午夜久久久在线观看| 亚洲精品第二区| 18禁国产床啪视频网站| 菩萨蛮人人尽说江南好唐韦庄| 欧美日韩国产mv在线观看视频| 久久久久久久亚洲中文字幕| 91国产中文字幕| 国精品久久久久久国模美| 国产深夜福利视频在线观看| 精品福利永久在线观看| 天美传媒精品一区二区| 国产亚洲精品第一综合不卡 | 国产亚洲欧美精品永久| 一边摸一边做爽爽视频免费| 亚洲人成77777在线视频| 成人国语在线视频| a级毛色黄片| 久久鲁丝午夜福利片| 国产国语露脸激情在线看| 18禁在线无遮挡免费观看视频| 免费黄频网站在线观看国产| 汤姆久久久久久久影院中文字幕| 王馨瑶露胸无遮挡在线观看| 久久毛片免费看一区二区三区| 大香蕉久久成人网| 欧美日韩国产mv在线观看视频| 巨乳人妻的诱惑在线观看| 亚洲精品日韩在线中文字幕| 国精品久久久久久国模美| 熟妇人妻不卡中文字幕| 在线精品无人区一区二区三| 亚洲av国产av综合av卡| 黑人猛操日本美女一级片| 国产69精品久久久久777片| 在线天堂中文资源库| 亚洲av成人精品一二三区| 夜夜骑夜夜射夜夜干| 在线观看免费视频网站a站| 这个男人来自地球电影免费观看 | 欧美精品国产亚洲| 国产一级毛片在线| 波野结衣二区三区在线| 免费av中文字幕在线| 超碰97精品在线观看| av有码第一页| 一级毛片电影观看| 男人舔女人的私密视频| 日韩人妻精品一区2区三区| 日本爱情动作片www.在线观看| 十八禁高潮呻吟视频| 交换朋友夫妻互换小说| 精品少妇内射三级| 80岁老熟妇乱子伦牲交| 免费播放大片免费观看视频在线观看| 老司机亚洲免费影院| 国产成人午夜福利电影在线观看| 亚洲综合色惰| 国产无遮挡羞羞视频在线观看| 老司机影院毛片| 久久人人爽人人爽人人片va| 亚洲精品中文字幕在线视频| 亚洲精品美女久久av网站| 成人国语在线视频| 啦啦啦啦在线视频资源| 最近最新中文字幕大全免费视频 | 五月开心婷婷网| 免费不卡的大黄色大毛片视频在线观看| 51国产日韩欧美| 捣出白浆h1v1| av免费在线看不卡| 在线观看www视频免费| videosex国产| 在线观看国产h片| 成年av动漫网址| 精品福利永久在线观看| videossex国产| 久久这里有精品视频免费| 香蕉国产在线看| 免费大片18禁| 国产欧美日韩一区二区三区在线| 国产免费现黄频在线看| 日本vs欧美在线观看视频| 男男h啪啪无遮挡| 晚上一个人看的免费电影| 99精国产麻豆久久婷婷| 看免费av毛片| 80岁老熟妇乱子伦牲交| 国产精品国产三级国产av玫瑰| 韩国av在线不卡| 亚洲人成77777在线视频| 丰满乱子伦码专区| 伊人久久国产一区二区| 国产一区二区三区av在线| 中文字幕精品免费在线观看视频 | 在线观看免费高清a一片| 国产xxxxx性猛交| 波多野结衣一区麻豆| av不卡在线播放| 久久av网站| 一级毛片 在线播放| 一级黄片播放器| 亚洲成色77777| 男女高潮啪啪啪动态图| 免费少妇av软件| 国产 一区精品| 国产精品久久久久成人av| 高清视频免费观看一区二区| 一级片'在线观看视频| 国产精品久久久久久精品古装| 肉色欧美久久久久久久蜜桃| 国产免费视频播放在线视频| 国产成人一区二区在线| 亚洲欧洲日产国产| tube8黄色片| 国产精品一国产av| 日本欧美国产在线视频| 波野结衣二区三区在线| 精品少妇久久久久久888优播| 男人添女人高潮全过程视频| av片东京热男人的天堂| 久久久精品区二区三区| 国产免费现黄频在线看| xxx大片免费视频| 最近2019中文字幕mv第一页| 国产精品国产av在线观看| 午夜av观看不卡| 国产在视频线精品| av线在线观看网站| 岛国毛片在线播放| 久久久久久伊人网av| 亚洲欧美清纯卡通| 亚洲精品久久成人aⅴ小说| 日韩人妻精品一区2区三区| 日韩大片免费观看网站| 日本午夜av视频| 亚洲成人手机| 99久久人妻综合| 人成视频在线观看免费观看| 2018国产大陆天天弄谢| 性色av一级| 久久精品人人爽人人爽视色| 在线精品无人区一区二区三| 久久久久久久久久久久大奶| 青春草亚洲视频在线观看| 欧美成人午夜精品| 国产探花极品一区二区| 国产色婷婷99| 成人亚洲欧美一区二区av| 一级a做视频免费观看| 欧美日韩av久久| 高清在线视频一区二区三区| 亚洲欧美精品自产自拍| 黑人高潮一二区| 国产日韩欧美视频二区| 色94色欧美一区二区| 日本猛色少妇xxxxx猛交久久| 国产精品蜜桃在线观看| 一级毛片黄色毛片免费观看视频| √禁漫天堂资源中文www| 女的被弄到高潮叫床怎么办| 国产av码专区亚洲av| 中文字幕最新亚洲高清| 天天躁夜夜躁狠狠躁躁| 国产精品一区二区在线观看99| 又粗又硬又长又爽又黄的视频| 性色av一级| 人人妻人人澡人人爽人人夜夜| 国产精品国产三级国产av玫瑰| 免费日韩欧美在线观看| 午夜福利乱码中文字幕| 天堂中文最新版在线下载| 国产国拍精品亚洲av在线观看| 丰满饥渴人妻一区二区三| 成人午夜精彩视频在线观看| 亚洲久久久国产精品| 成人手机av| 精品国产国语对白av| 国产亚洲av片在线观看秒播厂| 制服丝袜香蕉在线| 久久久久久久精品精品| 秋霞在线观看毛片| 97超碰精品成人国产| 国产极品天堂在线| 国产精品三级大全| 人妻少妇偷人精品九色| 另类亚洲欧美激情| 亚洲成国产人片在线观看| 亚洲精品久久午夜乱码| 99热这里只有是精品在线观看| 日韩在线高清观看一区二区三区| 91午夜精品亚洲一区二区三区| 色哟哟·www| 国产成人欧美| 国产男女超爽视频在线观看| 激情五月婷婷亚洲| 一二三四在线观看免费中文在 | 最近2019中文字幕mv第一页| 免费看光身美女| 91aial.com中文字幕在线观看| xxx大片免费视频| 韩国av在线不卡| 90打野战视频偷拍视频| 亚洲综合色网址| 亚洲av综合色区一区| 国产av码专区亚洲av| 精品一区在线观看国产| 内地一区二区视频在线| 纵有疾风起免费观看全集完整版| 欧美性感艳星| 国产亚洲精品第一综合不卡 | 欧美xxxx性猛交bbbb| 免费大片黄手机在线观看| 精品久久蜜臀av无| 国产精品国产三级国产专区5o| 亚洲成色77777| av一本久久久久| 久久久国产欧美日韩av| 亚洲精品乱久久久久久| 国产又爽黄色视频| 亚洲内射少妇av| 国产免费又黄又爽又色| 又粗又硬又长又爽又黄的视频| 国产精品麻豆人妻色哟哟久久| 日韩制服骚丝袜av| 天天躁夜夜躁狠狠躁躁| 精品一区二区三区四区五区乱码 | 街头女战士在线观看网站| 人妻系列 视频| 寂寞人妻少妇视频99o| 春色校园在线视频观看| 最近最新中文字幕大全免费视频 | 日本av免费视频播放| 激情视频va一区二区三区| 国产黄色免费在线视频| 国产69精品久久久久777片| 只有这里有精品99| 婷婷成人精品国产| 美女主播在线视频| 婷婷色av中文字幕| 国产欧美日韩综合在线一区二区| 久久久久久久国产电影| 亚洲欧美成人综合另类久久久| 狠狠精品人妻久久久久久综合| 久久精品国产自在天天线| 999精品在线视频| 国产一区二区三区av在线| 热re99久久精品国产66热6| 街头女战士在线观看网站| 啦啦啦啦在线视频资源| 最黄视频免费看| 亚洲国产成人一精品久久久| 国产麻豆69| 欧美成人午夜免费资源| 日本wwww免费看| 精品亚洲乱码少妇综合久久| 如何舔出高潮| 亚洲,欧美,日韩| 一本一本久久a久久精品综合妖精 国产伦在线观看视频一区 | 亚洲人成网站在线观看播放| 少妇的逼水好多| 香蕉丝袜av| 欧美人与性动交α欧美精品济南到 | a级毛片黄视频| 尾随美女入室| 国产精品国产三级专区第一集| xxx大片免费视频| 久久精品夜色国产| 九草在线视频观看| 极品人妻少妇av视频| 国产精品99久久99久久久不卡 | 搡老乐熟女国产| 国产欧美日韩一区二区三区在线| 亚洲经典国产精华液单| 亚洲国产欧美在线一区| 一边摸一边做爽爽视频免费| 国产欧美亚洲国产| 亚洲综合色惰| 欧美日韩av久久| 少妇高潮的动态图| 亚洲精品乱久久久久久| 亚洲五月色婷婷综合| 看免费成人av毛片| av又黄又爽大尺度在线免费看| 亚洲欧美中文字幕日韩二区| 90打野战视频偷拍视频| 成人国产麻豆网| 丝袜脚勾引网站| 狂野欧美激情性bbbbbb| 久久久久久久久久久免费av| 国产亚洲午夜精品一区二区久久| 另类精品久久| 黄色配什么色好看| 五月玫瑰六月丁香| 国产一级毛片在线| 久久99一区二区三区| 久久热在线av| 国产色爽女视频免费观看| 免费人妻精品一区二区三区视频| 欧美日韩国产mv在线观看视频| av视频免费观看在线观看| 精品一区二区免费观看| 国产亚洲一区二区精品| 全区人妻精品视频| 丰满迷人的少妇在线观看| videos熟女内射| 街头女战士在线观看网站| 在现免费观看毛片| 日本黄色日本黄色录像| 色哟哟·www| 亚洲国产精品国产精品| 日产精品乱码卡一卡2卡三| 一级毛片我不卡| 热99久久久久精品小说推荐| 亚洲欧美成人综合另类久久久| 最近2019中文字幕mv第一页| 国产成人精品福利久久| 午夜久久久在线观看| 久久精品国产鲁丝片午夜精品| 久久久亚洲精品成人影院| 成人无遮挡网站| 国产伦理片在线播放av一区| 黑人高潮一二区| 国产爽快片一区二区三区| 交换朋友夫妻互换小说| 国产成人a∨麻豆精品| 宅男免费午夜| xxx大片免费视频| 亚洲国产精品国产精品| 国产精品无大码| 水蜜桃什么品种好| 精品国产一区二区三区久久久樱花| 亚洲情色 制服丝袜| 久久狼人影院| 日本wwww免费看| 韩国高清视频一区二区三区| 欧美xxⅹ黑人| 卡戴珊不雅视频在线播放| 亚洲精华国产精华液的使用体验| 黄色 视频免费看| 国产成人精品一,二区| 亚洲精品乱码久久久久久按摩| 亚洲婷婷狠狠爱综合网| 亚洲精品一二三| 亚洲av成人精品一二三区| 日韩欧美精品免费久久| 国产又色又爽无遮挡免| 国产男人的电影天堂91| 亚洲精品国产av蜜桃| 午夜日本视频在线| 最后的刺客免费高清国语| 国产成人一区二区在线| 大片电影免费在线观看免费| 亚洲精品一区蜜桃| 制服诱惑二区| 九色亚洲精品在线播放| 熟女电影av网| 亚洲精品久久午夜乱码| 亚洲精华国产精华液的使用体验| 亚洲精品色激情综合| 国产深夜福利视频在线观看| 亚洲熟女精品中文字幕| 建设人人有责人人尽责人人享有的| 久久99一区二区三区| 精品久久久精品久久久| 亚洲中文av在线| 亚洲av电影在线观看一区二区三区| 日韩精品免费视频一区二区三区 | 国产av国产精品国产| 国产成人午夜福利电影在线观看| 一级片'在线观看视频| 新久久久久国产一级毛片| 精品国产乱码久久久久久小说| 亚洲av综合色区一区| 这个男人来自地球电影免费观看 | 国产一区二区三区av在线| 51国产日韩欧美| 精品国产一区二区三区久久久樱花| 亚洲欧美日韩卡通动漫| 国产毛片在线视频| 有码 亚洲区| 国产精品麻豆人妻色哟哟久久| 精品一区二区免费观看| 午夜精品国产一区二区电影| 亚洲熟女精品中文字幕| 韩国高清视频一区二区三区| 男女边摸边吃奶| 成年人午夜在线观看视频| 午夜福利在线观看免费完整高清在| 99九九在线精品视频| 久久久国产精品麻豆| 天美传媒精品一区二区| 国产伦理片在线播放av一区| 中文字幕最新亚洲高清| 成人午夜精彩视频在线观看| 午夜久久久在线观看| 日韩视频在线欧美| 成人国语在线视频| 女人精品久久久久毛片| 亚洲精品国产av蜜桃| 欧美日韩视频精品一区| 黄网站色视频无遮挡免费观看| 精品福利永久在线观看| 欧美日韩av久久| 男女边摸边吃奶| 最近的中文字幕免费完整| 国产女主播在线喷水免费视频网站| 人妻少妇偷人精品九色| 边亲边吃奶的免费视频| 亚洲国产精品成人久久小说| 国产福利在线免费观看视频| 女性被躁到高潮视频| 在线看a的网站| 亚洲国产色片| 满18在线观看网站| 在线 av 中文字幕| 男的添女的下面高潮视频| 午夜激情av网站| 国产精品 国内视频| 精品一区二区三区视频在线| 亚洲精品aⅴ在线观看| 国产精品熟女久久久久浪| 男女免费视频国产| 亚洲精品日本国产第一区| 久久99一区二区三区| 丝袜脚勾引网站| 亚洲av中文av极速乱| 建设人人有责人人尽责人人享有的| 国产极品天堂在线| 欧美成人午夜精品| 在线观看免费日韩欧美大片| 成年人午夜在线观看视频| 亚洲国产精品一区二区三区在线| 又黄又粗又硬又大视频| 国产成人精品久久久久久| 国产精品熟女久久久久浪| 亚洲精品aⅴ在线观看| 韩国av在线不卡| 寂寞人妻少妇视频99o| 精品一区二区三区视频在线| 国产成人精品无人区| 国产成人aa在线观看| freevideosex欧美| 天堂俺去俺来也www色官网| 91aial.com中文字幕在线观看| 婷婷成人精品国产| 国产一区二区在线观看日韩| 内地一区二区视频在线| 视频区图区小说| 丁香六月天网| 亚洲成国产人片在线观看| 国产日韩欧美在线精品| 久久久国产一区二区| 人妻 亚洲 视频| 9色porny在线观看| 亚洲性久久影院| 校园人妻丝袜中文字幕| www.av在线官网国产| 卡戴珊不雅视频在线播放| 中文字幕另类日韩欧美亚洲嫩草| 老司机影院成人| 亚洲激情五月婷婷啪啪| 天堂俺去俺来也www色官网| 亚洲熟女精品中文字幕| 中文字幕免费在线视频6| 日韩精品有码人妻一区| 高清在线视频一区二区三区| 黑人高潮一二区| 80岁老熟妇乱子伦牲交| 中国国产av一级| 久久鲁丝午夜福利片| 精品国产国语对白av| 国产免费福利视频在线观看| 国产成人aa在线观看| 国产精品成人在线| 亚洲国产欧美日韩在线播放| 五月伊人婷婷丁香| 国产乱人偷精品视频| av又黄又爽大尺度在线免费看| 亚洲精品久久成人aⅴ小说| 成人18禁高潮啪啪吃奶动态图| 亚洲久久久国产精品| 毛片一级片免费看久久久久| av.在线天堂| 下体分泌物呈黄色| 久久99蜜桃精品久久| 午夜精品国产一区二区电影| 十分钟在线观看高清视频www| 美女中出高潮动态图| 青春草亚洲视频在线观看| 亚洲国产日韩一区二区| 最后的刺客免费高清国语| 最近最新中文字幕大全免费视频 | 久久久久久久国产电影| 色婷婷av一区二区三区视频| 成人综合一区亚洲| 亚洲精品国产色婷婷电影|