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1.
贵州长顺代化石炭系中间界线的沉积相研究   总被引：3，自引：3，他引：3  
周志澄 《地层学杂志》1994,18(1):1-8,T002
在碳酸盐微相的详细研究基础上，贵州长顺代化下、上石炭统剖面由下至上可分出５个主要沉积相：盆地相、开阔海陆架相、下斜坡相、中斜坡相和上斜坡相，下、上石炭统界线处于连续沉积的中斜坡相内。  相似文献   

2.
Late Devonian (Famennian) marine successions globally are typified by organic-rich black shales deposited in anoxic and euxinic waters and the cessation of shelf carbonate sedimentation. This global ‘carbonate crisis’, known as the Hangenberg Event, coincides with a major extinction of reef-building metazoans and perturbations to the global carbon cycle, evidenced by positive carbon-isotope excursions of up to 4‰. It has been suggested that authigenic carbonate, formed as cements in sedimentary pore spaces during early burial diagenesis, is a significant mass fraction of the total global carbon burial flux, particularly during periods of low oxygen concentration. Because some authigenic carbonate could have originated from remineralization of organic carbon in sediments, it is possible for this reservoir to be isotopically depleted and thereby drive changes in the carbon isotopic composition of seawater. This study presents bulk isotopic and elemental analyses from fine-grained siliciclastics of the Late Devonian–Early Mississippian Bakken Formation (Williston Basin, USA) to assess the volume and isotopic composition of carbonates in these sediments. Carbonate in the Bakken black shales occurs primarily as microscopic disseminated dolomite rhombs and calcite cements that, together, comprise a significant mass-fraction (ca 9%). The elemental composition of the shales is indicative of a dynamic anoxic to sulphidic palaeoenvironment, likely supported by a fluctuating chemocline. Despite forming in an environment favourable to remineralization of organic matter and the precipitation of isotopically depleted authigenic carbonates, the majority of carbon isotope measurements of disseminated carbonate fall between −3‰ and +3‰, with systematically more depleted carbonates in the deeper-water portions of the basin. Thus, although there is evidence for a significant total mass-fraction of carbonate with contribution from remineralized organic matter, Bakken authigenic carbonates suggest that Famennian black shales are unlikely to be sufficiently 13C-depleted relative to water column dissolved inorganic carbon to serve as a major lever on seawater isotopic composition.  相似文献   

3.
南秦岭淅川地区上石炭统周营组有多门类化石共生 ,类为晚石炭世的标准分子 ,菊石、腕足、珊瑚、双壳、腹足类多具泥盆纪生物群特征。岩石组合、岩性特征、层序特征、沉积环境演变及构造古地理、生态的综合研究表明 ,周营组为晚石炭世沉积地层 ,其内的晚石炭世、中晚泥盆世古生物组合是在有障壁的局限滞留盆地这一特殊的古地理和生态环境下形成和发展起来的 ,是南秦岭淅川地区特有的组合 ,不具有搬运再沉积的物质条件 ,不是搬运再沉积的结果。每一次海侵 ,海水的加深和有机质的富集 ,是周营组生物群得以发生和发展的有利条件。海水的退出、咸化和相对闭塞环境下食物的缺乏 ,是生物群绝灭 ,并很好保存埋藏的主要原因。  相似文献   

4.
Across the Late Devonian biotic crisis, sclerobionts declined in diversity and abundance and the proportions of brachiopod shell textures changed radically. Most of the major sclerobiont clades were common to Givetian through Mississippian ecosystems. Microconchids, most abundant sclerobiont in most Devonian assemblages, were replaced by bryozoans in the Mississippian. Diversity and abundance of Mississippian sclerobionts were lower than Frasnian–Famennian assemblages.  相似文献   

5.
Although Late Cambrian microbial build-ups were recognized in the Point Peak Member of the Wilberns Formation in Central Texas (USA) nearly 70 years ago, only a few studies focused specifically on the build-ups themselves. This study focuses on the interpretation of the regional (15 measured sections described in literature representing an area of 8000 km2) and local (field and drone photogrammetry studies in a 25 km2 area from within south Mason County) microbial build-up occurrence, describes their growth phases and details their interactions with the surrounding inter-build-up sediments. The study establishes the occurrence of microbial build-ups in the lower and upper Point Peak members (the Point Peak Member is informally broken up into the lower Point Peak and the upper Point Peak members separated by Plectotrophia zone). The lower Point Peak Member consists of three <1 m thick microbial bioherms and biostrome units, in addition to heterolithic and skeletal/ooid grainstone and packstone beds. One, up to 14 m thick, microbial unit associated with inter-build-up skeletal and ooid grainstone and packstone beds, intercalated with mixed siliciclastic–carbonate silt beds, characterizes the upper Point Peak member. The microbial unit in the upper Point Peak member displays a three-phase growth evolution, from an initial colonization phase on flat based, rip-up clast lenses, to a second aggradation and lateral expansion phase, into a third well-defined capping phase. The ultimate demise of the microbial build-ups is interpreted to have been triggered by an increase of water turbidity caused by a sudden influx of fine siliciclastics. The lower Point Peak member represents inner ramp shallow subtidal and intertidal facies and the upper Point Peak member corresponds to mid-outer ramp subtidal facies. Understanding the morphological architecture and depositional context of these features is of importance for identifying signatures of early life on Earth.  相似文献   

6.
华北地台中元古界主要由环潮坪石英砂岩、浅海碳酸盐岩和浅海—泻湖相暗色页岩3种沉积相组合构成,以陆表海浅水碳酸盐岩占主导。碳酸盐岩中除含有丰富的微古植物、宏观藻类和微生物建隆外,还发育大量的微生物成因构造(MISS)和微生物诱发的碳酸盐沉淀(MMCP)。微生物席和MISS构造在高于庄组上部(约1.6 Ga)和雾迷山组下部(约1.45 Ga)碳酸盐岩中尤为发育,表明活跃的微生物活动和高有机质产量。在石化微生物席中,发现有丝状、球状细菌化石和草莓状黄铁矿;围岩中发现有针状文石、花瓣状重晶石、放射状菱铁矿、铁白云石和葡萄状碳酸盐胶结物等多种自生碳酸盐矿物,指示甲烷厌氧氧化(AOM)导致的自生碳酸盐沉淀。中元古代的温暖气候和海洋分层、缺氧、硫化条件有利于微生物的高生产量和高有机质埋藏率。气隆构造和核形石状碳酸盐结核反映浅埋藏条件下活跃的成烷作用和甲烷排放,围岩和MMCP中富沥青质。华北地台中元古界富微生物席碳酸盐岩有良好的生烃潜力,有可能形成重要的烃源岩。据微生物席、MISS构造及MMCP的研究,初步估算华北地台中元古代碳酸盐岩的概略生烃潜力约为10×108t石油当量。  相似文献   

7.
华南中二叠统栖霞组沉积了一套特殊的碳酸盐岩地层, 该套地层富含有机质和硅质结核, 是中国南方四套区域性海相烃源岩之一.在野外露头上, 灰岩-泥灰岩韵律层因为其抗风化能力不同而受到广泛关注, 其在整个华南栖霞组分布广泛.其中, 灰岩层富含各种生物碎屑, 主要包括钙藻、有孔虫和腹足, 其次还有腕足, 棘皮类和介形虫, 偶尔见苔藓虫和三叶虫.灰岩层中较好的保存了易碎的钙质藻类, 说明灰岩的胶结作用发生在成岩早期, 没有明显压实作用的痕迹.泥灰岩以粒泥生物碎屑灰岩和黑色钙质泥岩为主, 主要的生物碎屑以腕足和介形虫为主.生物碎屑都非常破碎, 壳体大都平行层面, 颗粒之间发育大量压溶缝, 说明泥灰岩层经历过强烈的成岩压实作用.基于对灰岩-泥灰岩韵律层的生屑类型和成岩现象的分析, 提出差异成岩作用来解释该套地层的形成过程: 泥灰岩层中不稳定的文石在早期成岩过程中溶蚀, 然后迁移到灰岩层中形成方解石胶结灰岩层; 随后机械压实作用和化学压实作用主要发生在泥灰岩层中; 最终灰岩-泥灰岩层由于差异成岩作用导致其抗风化能力不同而形成不同的露头特征.其中文石溶蚀发生在海水埋藏环境, 有机质的分解为其提供了动力来源, 这与栖霞期较高的原始生产力相符合.   相似文献   

8.
The end-Permian mass extinction devastated most marine communities and the recovery was a protracted event lasting several million years into the Early Triassic. Environmental and biological processes undoubtedly controlled patterns of recovery for marine invertebrates in the aftermath of the extinction, but are often difficult to single-out. The global diversity and distribution of marine lophophorates during the aftermath of the end-Permian mass extinction indicates that stenolaemate bryozoans, rhynchonelliform brachiopods, and lingulid brachiopods displayed distinct recovery patterns.Bryozoans were the most susceptible of the lophophorates, experiencing relatively high rates of extinction at the end of the Permian, and becoming restricted to the Boreal region during the Early Triassic. The recovery of bryozoans was also delayed until the Late Triassic and characterized by very low diversity and abundance. Following the final disappearance of Permian rhynchonelliform brachiopod survivors, Early Triassic rhynchonelliform brachiopod abundance remained suppressed despite a successful re-diversification and a global distribution, suggesting a decoupling between global taxonomic and ecological processes likely driven by lingering environmental stress.In contrast with bryozoans and rhynchonelliforms, lingulid brachiopods rebounded rapidly, colonizing shallow marine settings left vacant by the extinction. Lingulid dominance, characterized by low diversity but high numerical abundance, was short-lived and they were once again displaced back into marginal settings as environmental stress changed through the marine recovery. The presence in lingulid brachiopods of the respiratory pigment hemerythrin, known to increase the efficacy of oxygen storage and transport, when coupled with other morphological and physiological adaptations, may have given lingulids a survival advantage in environmentally stressed Early Triassic settings.  相似文献   

9.
The end-Permian mass extinction devastated most marine communities and the recovery was a protracted event lasting several million years into the Early Triassic. Environmental and biological processes undoubtedly controlled patterns of recovery for marine invertebrates in the aftermath of the extinction, but are often difficult to single-out. The global diversity and distribution of marine lophophorates during the aftermath of the end-Permian mass extinction indicates that stenolaemate bryozoans, rhynchonelliform brachiopods, and lingulid brachiopods displayed distinct recovery patterns.Bryozoans were the most susceptible of the lophophorates, experiencing relatively high rates of extinction at the end of the Permian, and becoming restricted to the Boreal region during the Early Triassic. The recovery of bryozoans was also delayed until the Late Triassic and characterized by very low diversity and abundance. Following the final disappearance of Permian rhynchonelliform brachiopod survivors, Early Triassic rhynchonelliform brachiopod abundance remained suppressed despite a successful re-diversification and a global distribution, suggesting a decoupling between global taxonomic and ecological processes likely driven by lingering environmental stress.In contrast with bryozoans and rhynchonelliforms, lingulid brachiopods rebounded rapidly, colonizing shallow marine settings left vacant by the extinction. Lingulid dominance, characterized by low diversity but high numerical abundance, was short-lived and they were once again displaced back into marginal settings as environmental stress changed through the marine recovery. The presence in lingulid brachiopods of the respiratory pigment hemerythrin, known to increase the efficacy of oxygen storage and transport, when coupled with other morphological and physiological adaptations, may have given lingulids a survival advantage in environmentally stressed Early Triassic settings.  相似文献   

10.
Late Devonian to Early Carboniferous stratigraphic units within the ‘Zhulumute’ Formation, Hongguleleng Formation (stratotype), ‘Hebukehe’ Formation and the Heishantou Formation near the Boulongour Reservoir in northwestern Xinjiang are fossil-rich. The Hongguleleng and ‘Hebukehe’ formations are biostratigraphically well constrained by microfossils from the latest Frasnian linguiformis to mid-Famennian trachytera conodont biozones. The Hongguleleng Formation (96.8 m) is characterized by bioclastic argillaceous limestones and marls (the dominant facies) intercalated with green spiculitic calcareous shales. It yields abundant and highly diverse faunas of bryozoans, brachiopods and crinoids with subordinate solitary rugose corals, ostracods, trilobites, conodonts and other fish teeth. The succeeding ‘Hebukehe’ Formation (95.7 m) consists of siltstones, mudstones, arenites and intervals of bioclastic limestone (e.g. ‘Blastoid Hill’) and cherts with radiolarians. A diverse ichnofauna, phacopid trilobites, echinoderms (crinoids and blastoids) together with brachiopods, ostracods, bryozoans and rare cephalopods have been collected from this interval. Analysis of geochemical data, microfacies and especially the distribution of marine organisms, which are not described in detail here, but used for facies analysis, indicate a deepening of the depositional environment at the Boulongour Reservoir section. Results presented here concern mainly the sedimentological and stratigraphical context of the investigated section. Additionally, one Late Devonian palaeo-oceanic and biotic event, the Upper Kellwasser Event is recognized near the section base.  相似文献   

11.
The Gordon Group carbonates consist of biota of the Chlorozoan assemblage, diverse non‐skeletal grains and abundant micrite and dolomite, similar to those of modern warm water carbonates. Cathodoluminescence studies indicate marine, meteoric and some burial cements. Dolomites replacing burrows, mudcracks and micrite formed during early diagenesis.

δ18O values (‐5 to ‐7%ō PDB) of the non‐luminescent fauna and marine cement are lighter than those of modern counterparts but are similar to those existing within low latitudes during the Ordovician because of the light δ18O values of Ordovician seawater (‐3 to ‐5%o SMOW). The δ18O difference (2%o) between marine and meteoric calcite indicates that Ordovician meteoric water was similar to that in modern subtropics. Values of δ13C relative to δ18O indicate that during the Early Ordovician there were higher atmospheric CO2 levels than at present but during the Middle and Late Ordovician they became comparable with the present because of a change from ‘Greenhouse’ to glacial conditions. δ18O values of Late Ordovician seawater were heavier than in the Middle Ordovician mainly because of glaciation.

Dolomitization took place in marine to mixed‐marine waters while the original calcium carbonate was undergoing marine to meteoric diagenesis.  相似文献   

12.
Uplifted during the 1964 Alaskan earthquake, extensive intertidal flats around Middleton Island expose 1300 m of late Cenozoic (Early Pleistocene) Yakataga Formation glaciomarine sediments. These outcrops provide a unique window into outer shelf and upper slope strata that are otherwise buried within the south‐east Alaska continental shelf prism. The rocks consist of five principal facies in descending order of thickness: (i) extensive pebbly mudstone diamictite containing sparse marine fossils; (ii) proglacial submarine channel conglomerates; (iii) burrowed mudstones with discrete dropstone layers; (iv) boulder pavements whose upper surfaces are truncated, faceted and striated by ice; and (v) carbonates rich in molluscs, bryozoans and brachiopods. The carbonates are decimetre scale in thickness, typically channellized conglomeratic event beds interpreted as resedimented deposits on the palaeoshelf edge and upper slope. Biogenic components originated in a moderately shallow (ca 80 m), relatively sediment‐free, mesotrophic, sub‐photic setting. These components are a mixture of parautochthonous large pectenids or smaller brachiopods with locally important serpulid worm tubes and robust gastropods augmented by sand‐size bryozoan and echinoderm fragments. Ice‐rafted debris is present throughout these cold‐water carbonates that are thought to have formed during glacial periods of lowered sea‐level that allowed coastal ice margins to advance near to the shelf edge. Such carbonates were then stranded during subsequent sea‐level rise. Productivity was enabled by attenuation of terrigenous mud deposition during these cold periods via reduced sedimentation together with active wave and tidal‐current winnowing near the ice front. Redeposition was the result of intense storms and possibly tsunamis. These sub‐arctic mixed siliciclastic‐carbonate sediments are an end‐member of the Phanerozoic global carbonate depositional realm whose skeletal attributes first appeared during late Palaeozoic southern hemisphere deglaciation.  相似文献   

13.
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   

14.
铁元素对海相沉积物早期成岩作用的影响   总被引：1，自引：0，他引：1  
铁元素是地壳中丰度最高的元素之一,在海相沉积物成岩过程中起着非常重要的作用.铁元素作为海洋初级生产力的微营养元素,影响海相沉积物中有机质的输入,其在早期成岩阶段与硫化物和磷元素的耦合关系,可以促进或者降低有机质的保存;铁元素在海相沉积物早期成岩过程中可以改变孔隙水的化学性质,影响亚稳定碳酸盐矿物的保存,导致碳酸盐沉积物...  相似文献   

15.
永珠地区位于申扎古生代盆地,区内发育连续的早奥陶世—中二叠世海相沉积序列。石炭系永珠组岩石组合特征为细粒石英砂岩、页岩、粉砂岩,夹多层生物碎屑灰岩,含丰富的生物化石,主要有腕足类、双壳类、牙形刺、珊瑚、苔藓虫、菊石、三叶虫。牙形刺Gnathodusgirtyi—Gnathodustexanus为早石炭世晚期组合;腕足类Productus—Rhipidomellatibetena为早石炭世晚期组合,Choristites—Spirigerella为晚石炭世早期下部组合,Trigonatretacf.paucicostulata—Elivellabaschkirica为晚石炭世早期上部组合。Uncinunellina是典型的冷水习性腕足类,Cyathaxonia是典型的冷水习性珊瑚,表明了全球石炭纪冰期已影响到本区。确定了永珠组的时代为早石炭世晚期—晚石炭世早期,且早石炭世与晚石炭世分界线在第11层与第12层之间。  相似文献   

16.
The Mississippian (Early Carboniferous) is generally a period of scarce carbonate buildups in South China. This study documents outcrops of stromatolite mounds at Mengcun and Helv villages, in Laibin City, Guangxi Province, South China. The stromatolite mounds contain various stromatolite morphologies including laminar, wavy-laminar, domal or hemispheroidal, bulbous, and flabellate-growth columns. Intramound rocks are brachiopod floatstone and dark thin-bedded laminated micrite limestone. Individual stromatolites at Mengcun village are generally 3–6 cm thick and morphologically represent relatively shallow-water laminar (planar and wavy-undulated stromatolites) and deeper-water domal, bulbous and columnar forms. Where mounds were formed, the stromatolites continued growing upward up to 60 cm thick. Thrombolitic fabrics also occur but are not common. Stromatolite microscopic structure shows the bulk of the lamination to consist of wavy microbialite and discrete thin micritic laminae. These mounds are intercalated in deep-water fore-reef talus breccia, packstone formed as a bioclastic debris flow and thin-bedded limestone containing common chert layers of the Tatang Formation (late Viséan). Further evidence supporting the deep-water setting of the stromatolite mounds are: (1) a laterally thinning horizon of brachiopod floatstone containing deep-water, small, thin-shelled brachiopods, peloidal micritic sediments and low-diversity, mixed fauna (e.g., thin-shelled brachiopods, tube-like worms and algae) that have been interpreted as storm deposits, (2) common fore-reef talus breccias, (3) lack of sedimentary structures indicating current action, (4) preservation of lamination with sponge spicules, and (5) lack of bioturbation suggesting that the stromatolites grew in a relatively low energy, deep-water setting. The stromatolite mounds are the first described stromatolite mounds in Mississippian strata of South China and contain evidence that supports interpretations of (1) growth history of Mississippian microbial buildups and (2) environmental controls on stromatolite growth and lithification.  相似文献   

17.
《Sedimentary Geology》2006,183(1-2):99-124
The snowball Earth hypothesis suggests that the Neoproterozoic was characterized by several prolonged and severe global glaciations followed by very rapid climate change to ‘hot house’ conditions. The Neoproterozoic Port Askaig Formation of Scotland consists of a thick succession of diamictite, sandstone, conglomerate and mudstone. Sedimentological and stratigraphic analysis of Port Askaig deposits exposed on the Garvellach Islands was carried out to establish the nature of Neoproterozoic palaeoenvironmental change preserved in this thick succession. Particular emphasis was placed on identifying and distinguishing between climatic and tectonic controls on sedimentation.Port Askaig Formation diamictite units are attributed to deposition by sediment gravity flow processes or ‘rainout’ of fine-grained sediment and ice-rafted debris in a glacially influenced marine setting. Associated facies record various depositional processes ranging from sediment gravity flows (conglomerate, massive sandstone and laminated mudstone) to deposition under other unidirectional currents (cross-bedded and horizontally laminated sandstone). The Port Askaig Formation is also characterized by abundant soft sediment deformation features that occur at discrete intervals and are interpreted to record episodic seismic activity.Stratigraphic analysis of the Port Askaig Formation on the Garvellach Islands reveals three phases of deposition. Phase I was dominated by sediment gravity flow processes and sedimentation was primarily tectonically controlled. Phase II was a transitional phase characterized by continued tectonic-instability, an increased supply of sand to the basin and the preservation of current-generated facies. In the third and final phase of deposition, the interbedded units of sandstone and diamictite are interpreted to reflect development of large sandy bedforms and ice margin fluctuations in a tectonically stable marine setting.Sedimentological and stratigraphic analysis of the Port Askaig Formation demonstrates that tectonic activity had a significant influence on development of the lowermost parts of the succession. Climatic influences on sedimentation are difficult to identify during such phases of tectonic activity but are more easily discerned during episodes of tectonic quiescence (e.g.,, Phase III of the Port Askaig Formation). The thick succession of diamictite interbedded with current-deposited sandstone preserved within the Port Askaig Formation is not consistent with deep freeze conditions proposed by the snowball Earth hypothesis.  相似文献   

18.
The clay assemblages of the Late Jurassic-Early Cretaceous sediments of the Agadir Basin are affected by burial diagenesis. Apparent ages of these formations, from the K-Ar dating of fine grain size fractions (< 2 μm), decrease downward. This indicates an opening of the K-Ar isotopic system of detrital Hercynian minerals during burial. The extent of the isotopic rehomogenisation is more important in sandstones than in clayey marl facies. During burial diagenesis, a temperature of 165°C in clayey marl and 110°C in sandstone can be enough for isotopic rehomogenisation of fine-grained Hercynian illite. The migration of pore water seems to favour the diffusion of radiogenic 40Ar in sandstones.  相似文献   

19.
ABSTRACT
The carbon and oxygen isotopic composition of the Austin Chalk was examined in cores representing a range of depths from surface to 3000 m in order to document the effects of burial diagenesis on carbon and oxygen isotopic composition. Low magnesium calcite oysters were separated (from 500 um wide areas) and analysed to estimate the starting composition of Cretaceous marine sediment. These gave an average value of -2·5%δ18O; + 2·0%δ13C (PDB). The compositions of micrite, intergranular cement, and fracture cement were analysed, and their deviation from this original marine composition was evaluated to document the progression of chalk diagenesis. Interestingly, micrite exhibits only minor variation in composition from marine values despite present burial depth ranges in excess of 3000 m. The average deviation from δ18O marine is less than 1·5. Furthermore, intergranular cement and particularly fracture cements, which occur only in the deepest cores and which clearly post-date micrite lithification, are generally indistinguishable from micrite in composition. Isotopic compositions exhibit no correlation with depth of burial despite abundant petrographic evidence of deep burial diagenesis. This uniformity in composition is interpreted as reflecting a closed, rock-dominated diagenetic system in which the compositions of precipitated carbonate cements were controlled by the composition of dissolving carbonates during lithification. As such, the composition of burial cement is not representative of the rock-water temperatures during precipitation.
Thus, in the context of isotopic analyses from other carbonate systems, unless the degree of openness of the diagenetic system is known, oxygen isotopic signatures of cements cannot directly be converted to the rock-water temperatures at which they were precipitated unless the composition of the ambient porefluid is also known.  相似文献   

20.
黔南晚石炭世叶状藻礁灰岩的成岩作用   总被引：1，自引：1，他引：0  
通过偏光显微镜研究和阴极发光技术, 对黔南晚石炭世叶状藻礁灰岩的成岩作用做了详细研究, 认为礁灰岩主要成岩作用类型有: 生物黏结障积作用、泥晶化作用、胶结作用、压实压溶作用、破裂作用、重结晶作用和溶解作用等。根据岩石薄片阴极发光测试结果的观察、分析, 将成岩过程划分为4个阶段: 准同生成岩阶段、早期成岩阶段、埋藏成岩阶段和后生成岩阶段。通过各种成岩作用的标志性特征及它们在阴极发光下的特征, 推测藻礁灰岩主要经历了海底成岩环境、大气淡水成岩环境和埋藏成岩环境。  相似文献   

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