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1.
Relatively few studies have so far addressed diagenetic processes in Heterozoan carbonates and the role that sediment composition and depositional facies exert over diagenetic pathways. This paper presents a study of Oligocene shallow-water, Heterozoan carbonates from the Maltese Islands. We investigate stratigraphic distribution, abundance and timing of diagenetic features and their relationship to sediment composition and depositional facies. The studied carbonate rocks comprise rud- to packstones of the Heterozoan association predominantly containing coralline red algae, bryozoans, echinoids and benthic foraminifers. XRD analyses show that all high-Mg calcite has been transformed to low-Mg calcite and that no aragonite is preserved. Diagenetic processes include dissolution of aragonitic biota, neomorphism of high-Mg calcitic biota to low-Mg calcite and cementation by fibrous, bladed, epitaxial and blocky cements. Stable isotopes on bulk rock integrated with petrographic data suggest that the study interval was not exposed to significant meteoric diagenesis. We interpret early cementation to have taken place in the marine and marine burial environment. The distribution and abundance of early diagenetic features, determining the diagenetic pathway, can be related to the primary sediment composition and depositional texture. Sorting and micrite content are important controls over the abundance of diagenetic features.  相似文献   

2.
During diagenetic stages, the aragonitic skeletons and the inter/intra-corallite cement of the upper Jurassic corals of Hanifa Formation either dissolved or subjected to diagenetic alterations including cementation, micritization, recrystallization, silicification, dolomitization and dedolomitization. The proposed sequence of diagenetic stages is as follows: early marine diagenesis, early meteoric and mixing zone diagenesis, late meteoric diagenesis, and shallow burial diagenesis. Each stage is characterized by certain diagenetic processes. The source of sulfate solutions for dedolomitization in the studied corals is the dissolved anhydrite deposits of the Arab–Hith Formations, sometime before their erosion. A possible source of silica, needed for the formation of chert and chalcedony, is the sponge spicules dispersed in many carbonates of the Hanifa Formation.  相似文献   

3.
以西科1井第四系乐东组生物礁-碳酸盐岩地层为研究对象, 通过偏光显微镜观察、茜素红-S和铁氰化钾混合溶液染色、扫描电镜和矿物阴极发光性观察等分析方法研究了生物礁-碳酸盐岩的岩石学和成岩作用特征.西科1井生物礁-碳酸盐岩成岩作用包括较弱的压实作用、新生变形作用、微生物泥晶化作用、溶解作用、胶结作用.以典型胶结物岩相学产状为标志, 结合矿物阴极发光性特征识别出了大气水和海水成岩环境.其中, 大气水成岩环境以典型的新月形或悬垂形方解石胶结物为识别标志, 海水成岩环境以纤维状-针状文石为识别标志.成岩环境的垂向分布表现为: 0~27 m深度内为显著的大气水成岩环境; 27~42 m深度内以大气水成岩环境为主, 其次为海水成岩环境; 42~105 m深度内以大气水成岩环境为主, 海水成岩环境的影响弱; 105~172 m深度内大气水和海水成岩环境均出现; 172.00~214.89 m深度内为海水成岩环境.   相似文献   

4.
对塔河油田奥陶系碳酸盐岩中方解石胶结物的阴极发光性和微量元素构成研究发现,一些与大气水成岩环境有关的方解石胶结物显示出亮、暗相间阴极发光环带,微量元素含量与阴极发光环带之间具有良好的对应关系,亮带具有较高的Mn、Fe含量,暗带则具有较高的Sr、Na含量,显示方解石胶结过程中大气水作用强度的变化。这些碳酸盐矿物的阴极发光环带受元素构成变化控制,并反映成岩流体中元素含量的变化和/或结晶速率的变化,这在一定程度上与大气水环境相对开放的成岩条件有关。相对晚期的环带发光较亮,并具有较高的Mn和较低的Sr、Na含量,显示与加里东—海西期构造运动有关的古岩溶过程中大气水作用逐渐加强的总体成岩趋势。  相似文献   

5.
The diagenesis of modern and ancient carbonatesedi ments has been widely studied and systematicallyreviewed since the 1960s (e .g. Moore ,2001 ,1989 ;Wang et al ., 1994 , 1991 ; McIlreath and Morrow,1990 ; Tucker and Bathurst , 1990 ; Schneidermannand Harris , 1985 ; Longman, 1980 ; Bathurst ,1975) . With the development of sequence stratigra-phy and its more widespread application, discussionabout the relationship between diagenesis and se-quence stratigraphy/sea-level changes ,as well as…  相似文献   

6.
Late Palaeozoic‐age strata from the Capitan Reef in west Texas show facies‐dependent heterogeneity in the sulphur isotopic composition of carbonate‐associated sulphate, which is trace sulphate incorporated into carbonate minerals that is often used to reconstruct the sulphur isotopic composition of ancient seawater. However, diagenetic pore fluid processes may influence the sulphur isotopic composition of carbonate‐associated sulphate. These processes variously modify the sulphur isotopic composition of incorporated sulphate from syndepositional seawater in shelf crest, outer shelf, shelf margin and slope depositional settings. This study used a new multicollector inductively‐coupled plasma mass spectrometry technique to determine the sulphur isotopic composition of samples of individual depositional and diagenetic textures. Carbonate rocks representing peritidal facies in the Yates and Tansill formations preserve the sulphur isotopic composition of Guadalupian seawater sulphate despite alteration of the carbon and oxygen isotopic compositions by meteoric and dolomitizing diagenetic processes. However, sulphur isotopic data indicate that limestones deposited in reef and slope facies in the Capitan and Bell Canyon formations largely incorporate sulphate from anoxic marine‐phreatic pore fluids isotopically modified from seawater by microbial sulphate reduction, despite generally preserving the carbon and oxygen isotopic compositions of Permian seawater. Some early and all late meteoric calcite cements have carbonate‐associated sulphate with a sulphur isotopic composition distinct from that of Permian seawater. Detailed petrographic and sedimentary context for carbonate‐associated sulphate analyses will allow for improved reconstructions of ancient seawater composition and diagenetic conditions in ancient carbonate platforms. The results of this study indicate that carbonate rocks that diagenetically stabilize in high‐energy environments without pore fluid sulphate gradients can provide a robust archive of ancient seawater's sulphur isotopic composition.  相似文献   

7.
The Vindhyan sedimentary succession in central India spans a wide time bracket from the Paleoproterozoic to the Neoproterozoic period. Chronostratigraphic significance of stable carbon and oxygen isotope ratios of the carbonate phase in Vindhyan sediments has been discussed in some recent studies. However, the subtle controls of facies variation, depositional setting and post-depositional diagenesis on stable isotope compositions are not yet clearly understood. The Vindhyan Supergroup hosts four carbonate units, exhibiting a wide variability in depositional processes and paleogeography. A detailed facies-specific carbon and oxygen isotope study of the carbonate units was undertaken by us to investigate the effect of these processes and to identify the least altered isotope values. It is seen that both carbon and oxygen isotope compositions have been affected by early meteoric water diagenesis. The effect of diagenetic alteration is, however, more pronounced in case of oxygen isotopes than carbon isotopes. Stable isotope compositions remained insensitive to facies only when sediments accumulated in a shallow shelf setting without being exposed. Major alteration of original isotope ratios was observed in case of shallow marine carbonates, which became exposed to meteoric fluids during early diagenetic stage. Duration of exposure possibly determined the magnitude of alteration and shift from the original values. Moreover, dolomitization is found to be accompanied by appreciable alteration of isotope compositions in some of the carbonates. The present study suggests that variations in sediment depositional settings, in particular the possibility of subaerial exposure, need to be considered while extracting chronostratigraphic significance from δ13C data.  相似文献   

8.
Different diagenetic transformations and their relative chronological sequence are studied in the meteoric diagenetic zone from the Upper Oligocene limestone at the North of the Aquitaine Basin (France), by combining high-resolution cathodoluminescence spectroscopy and electron-microprobe analyses. More than 128 spot analyses by electron microprobe and 60 analyses by cathodoluminescence spectroscopy are done on different meteoric cements firstly identified by classic optical microscopy. Three cement types are identified according to the relative intensity of the bands of their respective cathodoluminescence spectra (350, 380, 430, 500, and 620 nm). From these investigations, we could identify for each meteoric cement different phases of crystalline growth and crystalline dissolution. As a result, a better and more realistic meteoric diagenetic model is proposed. It illustrates the cyclic transformations from vadose zone (unsaturated) to meteoric zone (saturated). To cite this article: R. Chapoulie et al., C. R. Geoscience 337 (2005).  相似文献   

9.
以陕西镇安西口石炭-二叠系界线剖面为具体实例, 探讨了冰川型海平面变化控制下的台地碳酸盐岩成岩作用规律.描述了陕西镇安西口石炭-二叠系界线剖面碳酸盐岩的各种成岩作用类型.根据成岩组构将研究区碳酸盐岩的成岩环境分为海水、大气淡水和埋藏环境.综合分析了各种成岩作用及其成岩环境的纵向分布特征.研究表明, 剖面上碳酸盐岩成岩作用和成岩环境的特征与岩石在高频旋回中的相对位置存在明显的对应关系, 受大振幅、高频率的冰川型海平面变化控制.早期海平面相对上升, 形成旋回的下部单元, 岩石首先经历海底成岩作用, 随着上覆沉积物的增加, 逐渐进入浅埋藏环境, 成岩作用表现为以压溶、重结晶作用发育为主要特征.晚期形成旋回的上部单元, 由于海平面相对下降, 沉积物逐渐抬升, 早期海底成岩作用尚未充分发育就脱离海水环境, 进入大气淡水成岩环境, 以强烈的大气淡水成岩作用为特征.   相似文献   

10.
碳酸盐岩成岩作用与孔隙演化   总被引：20，自引：1，他引：20  
王英华 《沉积学报》1992,10(3):85-95
在总结我国碳酸盐岩沉积和成岩基本特征的基础上,阐明有利于孔隙形成的白云石化、去膏、去云化、淡水和埋藏溶解等作用,以及破坏性成岩作用的特征和识别标志。成岩地质体是成岩环境的产物,可根据成岩组构、地球化学和发光特征等加以鉴别。成岩模式是成岩组合、成岩特征和孔隙演化的总概括,以滩相成岩模式展示了成岩相与孔隙的关系。  相似文献   

11.
In order to understand the post-depositional history of carbonate rocks of Guri Member (Lower to Middle Miocene), three stratigraphic sections were selected in north Bandar-Abbas in southeast of Iran. Sampling was carried out, analyzed for selective parameters such as oxygen and carbon isotopic compositions (δ18O and δ13C) and interpreted in the present study. We recognized several diagenetic processes including micritization, cementation, neomorphism, compaction, dissolution, silicification, dolomitization, fracturing and vein filling. Some of the diagenetic processes occurred at different conditions, so in order to achieve precise interpretation, samples from different carbonate components such as, micrite, fracture cement, solution pore cement, intergranular cement, and some biotic allochems were analyzed. In this study micrite samples were subdivided into two groups including micro-spary and micrite. They were recognized under Cathodoluminescence microscope. In addition, micrite samples were classified into five groups based on their depositional environments: supratidal, lagoon, coral bar, open sea, and open basin. There were minor changes in stable isotope ratios based on the sedimentary environments, stratigraphy successions, and micro-spary or micrite properties. In this study, similar calcite cements in petrography studies were differentiated by stable isotope data. Those calcite cements have formed in different diagenetic environments such as meteoric and burial cements. Paragenetic sequence of carbonate rocks were interpreted by integration of petrographic and isotopic studies. We have reconstructed diagenetic models of Guri Member into four stages including marine, meteoric, burial, and uplifting.  相似文献   

12.
The Darlington (Sakmarian) and Berriedale (Artinskian) Limestones are neritic deposits that accumulated in high‐latitude environments along the south‐eastern margin of Pangea in what is now Tasmania. These rocks underwent a series of diagenetic processes that began in the marine palaeoenvironment, continued during rapid burial and were profoundly modified by alteration associated with the intrusion of Mesozoic igneous rocks. Marine diagenesis was important but contradictory; although dissolution took place, there was also coeval precipitation of fibrous calcite cement, phosphate and glauconite, as well as calcitization of aragonite shells. These processes are interpreted as having been promoted by mixing of shelf and upwelling deep ocean waters and enabled by microbial degradation of organic matter. In contrast to warm‐water carbonates where meteoric diagenesis is important, the Darlington and Berriedale Limestones were largely unaffected by meteoric diagenesis. Only minor dissolution and local cementation took place in this diagenetic environment, although mechanical compaction was ubiquitous. Correlation with burial history curves indicates that chemical compaction became important as burial depths exceeded 150 m, promoting precipitation of extensive ferroan calcite. This effect resulted from burial by rapidly deposited, overlying, thick, late Permian and Triassic terrestrial sediments. This diagenetic pathway was, however, complicated by the subsequent intrusion of massive Mesozoic diabases and associated silicifying diagenetic fluids. Finally, fractures most probably connected with Cretaceous uplift were filled with late‐stage non‐ferroan calcite cement. This study suggests that both carbonate dissolution and precipitation occur in high‐latitude marine palaeoenvironments and, therefore, the cold‐water diagenetic realm is not always destructive in terms of diagenesis. Furthermore, it appears that for the early Permian of southern Pangea at least, there was no real difference in the diagenetic pathways taken by cool‐water and cold‐water carbonates.  相似文献   

13.
Early marine diagenetic dolomite is a rather thermodynamically-stable carbonate phase and has potential to act as an archive of marine porewater properties. However, the variety of early to late diagenetic dolomite phases that can coexist within a single sample can result in extensive complexity. Here, the archive potential of early marine dolomites exposed to extreme post-depositional processes is tested using various types of analyses, including: petrography, fluid inclusion data, stable δ13C and δ18O isotopes, 87Sr/86Sr ratios, and U-Pb age dating of various dolomite phases. In this example, a Triassic carbonate platform was dissected and overprinted (diagenetic temperatures of 50 to 430°C) in a strike-slip zone in Southern Spain. Eight episodes of dolomitization, a dolostone cataclasite and late stage meteoric/vadose cementation were recognized. The following processes were found to be diagenetically relevant: (i) protolith deposition and fabric-preservation, and marine dolomitization of precursor aragonite and calcite during the Middle–Late Triassic; (ii) intermediate burial and formation of zebra saddle dolomite and precipitation of various dolomite cements in a Proto-Atlantic opening stress regime (T ca 250°C) during the Early–Middle Jurassic; (iii) dolomite cement precipitation during early Alpine tectonism, rapid burial to ca 15 km, and high-grade anchizone overprint during Alpine tectonic evolution in the Early Eocene to Early Miocene; (iv) brecciation of dolostones to cataclasite during the onset of the Carboneras Fault Zone activity during the Middle Miocene; and (v) late-stage regression and subsequent meteoric overprint. Data shown here document that, under favourable conditions, early diagenetic marine dolomites and their archive data may resist petrographic and geochemical resetting over time intervals of 108 or more years. Evidence for this preservation includes preserved Late Triassic seawater δ13CDIC values and primary fluid inclusion data. Data also indicate that oversimplified statements based on bulk data from other petrographically-complex dolomite archives must be considered with caution.  相似文献   

14.
卢欢  王清斌  牛成民  杜晓峰  宋章强  冯冲 《地球科学》2020,45(10):3721-3730
石臼坨凸起陡坡带Q29和Q36构造中深部储层是渤海最大的湖相碳酸盐岩和扇三角洲碎屑岩的混合沉积,这一亿吨级油气田的发现,刷新了碎屑岩储层最厚、单层油层最厚、测试产能最高纪录.通过岩心观察、薄片鉴定、碳氧同位素分析、元素分析等多种分析手段,认为同沉积大气水淋滤作用,对石臼坨凸起陡坡带混积岩系优质储层的形成起到了至关重要的影响.通过对岩石学标志和元素地球化学标志的分析认为,大气水淋滤作用的主要包括两个过程,一是同沉积淋滤作用下,砾石段产生的选择性溶蚀孔、粒内缝、碎屑高岭石;二是沉积后暴露下,碳酸盐岩段产生的垂直岩溶缝、悬垂状白云石、示顶底构造.在此基础上,提出了大气水淋滤作用的模式,可分为成岩作用差异明显两个成岩带,即大气水渗流带和大气水潜流带,并进一步总结了各带内部的成岩特征和演化模式.   相似文献   

15.
ABSTRACT Field, geochemical, and petrographic data for late Pleistocene dolomites from southeastern Barbados suggest that the dolomite precipitated in the zone of mixing between a coastal meteoric phreatic lens and normal marine waters. The dolomite is localized in packstones and wackestones from the algalAmphistegina fore-reef calcarenite facies. Stable isotopic evidence suggests that meteoric water dominated the diagenetic fluids responsible for dolomitization. Carbon isotopes in pure dolomite phases average about -15%0 PDB. This light carbon is attributed to the influence of soil gas CO2, and precludes substantial mixing with seawater. A narrow range of oxygen isotopic compositions coupled with a wide range of carbon compositions attest to the meteoric diagenetic overprint. Dolomitization likely occurred with as little as a five per cent admixture of seawater. Strontium compositions of the dolomites indicate probable replacement dolomitization of original unstable mineralogy. The dolomite is characterized by low sodium values. Low concentrations of divalent manganese and iron suggest oxidizing conditions at the time of dolomitization. A sequence of petrographic features suggests a progression of diagenetic fluids from more marine to more meteoric. Early marine diagenesis was followed by replacement dolomitization of skeletal grains and matrix. Limpid, euhedral dolomite cements precipitated in primary intra- and interparticle porosity subsequent to replacement dolomitization. As waters became progressively less saline, dolomite cements alternated with thin bands of syntaxial calcite cement. The final diagenetic phase precipitated was a blocky calcite spar cement, representing diagenesis in a fresh-water lens. This sequence of diagenetic features arose as the result of a single fall in eustatic sea-level following deposition. A stratigraphic-eustatic-diagenetic model constrains both the timing and rate of dolomitization in southeastern Barbados. Dolomitization initiated as sea-level began to fall immediately following the oxygen isotope stage 7–3 high stand, some 216 000 yr bp . Due to the rapidity of late Pleistocene glacio-eustasy, dolomitization (locally complete) is constrained to have occurred within about 5000 yr.  相似文献   

16.
祝仲蓉 Marsh.  J 《沉积学报》1992,10(1):133-145
更新世以来,剧烈的构造运动已将巴布亚新几内亚合恩半岛东北海岸的晚第四纪珊瑚礁阶地抬升上千米.阶地中造礁珊瑚的成岩变化和成岩产物的组构特征反映了该礁的成岩历史,充分体现该区快速构造上升的影响.海水潜流带和淡水渗流带为上升礁的主要成岩环境.生物钻孔、生物碎屑填隙、珊瑚文石针粗化、珊瑚骨骼的溶解和新生变形转化,以及其不同矿物成分和组构的种种胶结物的胶结作用是造礁珊瑚经历的主要成岩作用.地球化学资料表明其成岩变化发生于开放的化学体系之中.  相似文献   

17.
Although carbonate-associated sulfate (CAS) is used widely as a proxy for the sulfur isotope composition of ancient seawater, little is known about the effects of diagenesis on retention of primary δ34S signals. Our case study of the Key Largo Limestone, Pleistocene, Florida, is the first systematic assessment of the impact of meteoric diagenesis on CAS properties. Geochemical and petrographic data show that meteoric diagenesis has affected the exposed coralline facies to varying degrees, yielding differences now expressed as sharp reaction fronts between primary and secondary carbonate minerals within individual coral heads. Specifically, analyses across high-resolution transects in the Key Largo Limestone show that concentrations of strontium and sodium decrease across the recrystallization front from original aragonite to meteoric low-magnesium calcite by factors of roughly 5 and 10, respectively. Predictably, δ18O values decrease across these same fronts. The δ13C relationships are more complex, with the most depleted values observed in the latest-formed calcite. Such trends likely reflect carbon isotope buffering capacity that decreased as reaction progressed, as well as protracted development of soil profiles and the associated terrestrial biomass and thus depleted δ13C during sea-level lowstand. Conversely, δ34S values of CAS vary within a narrow ‘buffered’ range from 20.6 to 22.6‰ (compared to 20.8-22.0‰ of coeval Pleistocene seawater) across the same mineralogical transition, despite sulfate concentrations that drop in the diagenetic calcite by an average factor of 12. Collectively, these data point to robust preservation of primary δ34S for carbonates that have experienced intense meteoric diagenesis, which is encouraging news for those using the isotopic composition of CAS as a paleoceanographic proxy. At the same time, the vulnerability of CAS concentrations to diagenetic resetting is clear.  相似文献   

18.
Two oolites in the Dinantian (Mississippian/Lower Carboniferous) of Glamorgan, SW Britain, were deposited in similar depositional environments but have contrasting diagenetic histories. The Brofiscin and Gully Oolites occur in the upper parts of shallowing-upward sequences, formed through strandplain progradation and sand shoal and barrier growth upon a southward-dipping carbonate ramp. The Brofiscin Oolite is characterized by a first-generation cement of equant calcite spar, preferentially located at grain-contacts and forming non-isopachous fringes around grains, interpreted as meteoric vadose and phreatic in origin. Isopachous fibrous calcite fringes of marine origin are rather rare and occur only at a few horizons. Burial compaction was not important and porosity was occluded by poikilotopic calcite spar. Fitted grain-grain contacts locally occur and could be the result of near-surface vadose dissolution-compaction. Syntaxial overgrowths on echinoderm debris are common. Pre-compaction overgrowths are cloudy (inclusion-rich) and probably of meteoric origin, and post-compaction overgrowths are inclusion-free. By contrast, the Gully Oolite has little first-generation cement. However, marine fibrous calcite is common in oolitic intraclasts, as isopachous fringes of acicular calcite crystals closely associated with peloidal internal sediment; and early equant, drusy calcite spar occurs in the uppermost part of the Gully, beneath a prominent palaeokarst where pedogenic cements also occur. The major feature of Gully diagenesis is burial compaction, resulting in extensive grain-grain dissolution and microstylolitic grain contacts, and post-compaction poikilotopic spar occluded remaining porosity. The Brofiscin Oolite is pervasively dolomitized up-dip but the Gully Oolite for the most part only contains scattered pre-compaction dolomite rhombs and late veins of baroque dolomite, with less pervasive dolomitization. The difference in diagenetic style of the two Dinantian oolites is attributed to prevailing climate. The paucity of early meteoric cements in the Gully is a result of an arid climate, and this is supported by the nature of the capping palaeokarst. The abundant meteoric cements in the Brofiscin reflect a more humid climate, and effective meteoric recharge also resulted in up-dip pervasive mixing-zone dolomitization. The style of early diagenesis in these two oolites exerted a major control on the later burial diagenesis: in the Brofiscin, the early cements inhibited grain-grain dissolution and pressure solution, while these processes operated extensively in the Gully Oolite. Thus, prevailing climate can influence a limestone's diagenetic history from near-surface through into deep burial.  相似文献   

19.
延长油区上三叠统长 2地层河流相-三角洲相砂岩储层的物性明显受埋藏-成岩作用事件的影响。埋藏压实作用是导致砂岩孔隙丧失的主要原因,造成的平均孔隙度丧失为 17.8%。其中黑云母的早期成岩蚀变是造成原生孔隙丧失的一个重要原因。胶结作用造成的平均孔隙度丧失为 7.1%。其中碳酸盐胶结物和次生石英加大是造成砂岩物性降低的主要胶结物。碎屑颗粒周围绿泥石薄膜的存在阻止了一部分石英次生加大及碳酸盐胶结物的沉淀,使一部分原生粒间孔隙得以保存。晚期成岩阶段有机质分解形成的酸性流体及表生成岩作用阶段的大气降水是形成次生孔隙的主要原因,从而使长 2砂岩的物性得到改善  相似文献   

20.
The upper Jurassic carbonate settings in Iran are widely exposed in north and northeastern parts. Five stratigraphic columns were selected in the north eastern Iran. Their thickness ranges from 330 to 500 m. The various diagenetic processes identified include, micritization, cementation, compaction (physical and chemical), dissolution, neomorphism, pyritization, hematitization, silicification and dolomitization, which affected these carbonates. Elemental and stable isotopes analysis indicated that these deposits have undergone both meteoric and burial diagenesis in a relatively open system with moderate water-rock interaction. The positive trend between trace elements and oxygen isotope depletion also support these burial conditions. Lighter δl8O values of the dolomite samples may be related to an increase in temperature during the burial, which correspond to coarser euhedral crystals. Relatively higher δ18O values in finer dolomite crystals indicate their formation at lower burial depths relative to coarser crystals. Petrographic evidences such as coarse euhedral crystals with bright and dull zonation prove this interpretation. Chert nodules also have lighter 18O values relative to carbonate host rock, thus indicating the influence of burial diagenetic processes in their formation. The average environmental palaeotemperature was estimated to be 26°C on the basis of oxygen isotope values of less altered lime-mudstones.  相似文献   

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