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缝合线构造是古代碳酸盐岩中常见的一种沉积构造现象,属原生微构造类型。它在剖面中一般呈锯齿状曲线,状如动物头盖骨中的接合缝,平面上呈一个起伏不平的面。通常认为缝合线为压溶作用所形成,即在上覆岩层的静压力下,碳酸盐岩层产生不均匀的溶解而成。它的形成与岩石的成分、结构和环境有关。根据本区缝合线的发育特征,可将缝合线分为原生和次生两种成因类型:(1)原生 相似文献
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黔南、黔北及南盘江坳陷古生代碳酸盐岩储层特征 总被引：3，自引：1，他引：3
黔南、黔北及南盘江坳陷发育有相当规模的古生代海相碳酸盐岩沉积,沉积厚度大;重要储层岩性为微晶-亮晶生物碎屑灰岩、藻礁-生物礁灰岩和生物碎屑叠层泥晶灰岩;储集空间类型为原生和次生孔隙:原生孔隙有生物体腔孔、生物骨架孔和原生粒间孔,次生孔隙有晶间孔、粒内溶孔、铸模孔、溶蚀孔和微孔,以及缝合线孔隙和裂隙。本区溶蚀作用形成的次生孔隙增大了储层储集空间,使面孔率达到8.7%,而后期形成的构造裂缝又改善了储层的连通性,提高了储层的渗透能力;从储集空间的配置关系角度对碳酸盐岩储层进行油气资源评价分析,得出黔南坳陷碳酸盐岩储层为I类储集层;南盘江坳陷和黔北坳陷碳酸盐岩储层为II类储集层。 相似文献
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渤海湾西北岸大吴庄牡蛎礁是近年来研究程度最高的礁体,天津空港物流中心牡蛎礁则是近年来新发现的礁体。该两处礁体上部的牡蛎个体内部充填的泥、个体之间的泥以及礁体上覆沉积泥层中的硅藻研究表明,礁顶上下（即礁体的上部-顶部和上覆沉积泥层的下部）均富含潮间带环境指示种的Auliscus caelatus,表明礁体发育后期和上覆沉积泥层的初期,均为潮间带环境。尽管如此,从礁顶向上覆沉积泥层转换方式在两处礁体却不相同:（1）大吴庄:Auliscus caelatus种向上逐渐减少,暗示着大吴庄剖面由礁体上部的潮间带中上部、直至上覆沉积泥层下部的潮间带上部、进一步向上覆沉积泥层上部的潮上带转化的趋势。（2）空港:牡蛎礁上覆沉积泥层出现了比例达6%~23%的河口咸水-半咸水种Achnanches brevipes,而下伏礁体内则未见该种,暗示此处泥层受河口作用显著影响。此种不同揭示了礁体停止发育的原因有所不同:在5 520cal BP时,大吴庄礁顶进入潮间带中上部,礁体经常脱离海水而发育停止;在约4 000 cal BP时,空港礁体所在位置因河流作用突然增强,在时间上看很可能是黄河改道在天津入海,古黄河携带大量泥砂入海,掩盖了潮间带的牡蛎礁而导致牡蛎礁发育停止。 相似文献
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湖北省西部利川县境内的上二叠统发育有我国最典型的生物礁。礁体产于长兴组二段(含古纺锤(竹蜓) Palaeofusulina 带),以见天坝一带出露最佳。1977—1978年,江汉石油学院刘怀波、高振中等报道了黄泥塘生物礁的发现,并对该区生物礁的组成、形成环境提出了看法。1980—1982年,中国科学院地质研究所、四川石油管理局地质勘探开发研究院、江汉石油学院及江汉石油管理局等曾先后赴见天坝考察,并分别进行深入详细的研究,一致确认该区生物礁是以钙质海绵为主要造架生物的、晚二叠世碳酸盐台地边缘生物礁。 相似文献
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世界上许多大型石油、天然气田与海相生物礁碳酸岩沉积物有关,因为这些岩层对油、气的形成和储存可以提供极为有利的条件。为了指导古代生物礁区油、气资源的寻找和勘探,沉积学家必需对现代生物礁形成、沉积作用和沉积环境进行全面的研究,采用比较沉积学的方法,再造古代生物礁的 相似文献
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最近十几年,越来越多的人注意到若干金属、非金属矿床在空间位置上和成因上与生物礁有关,在矿床研究中开始运用碳酸盐沉积学和石油地质学的一些成果.在国内,这一问题也引起了不少同志的注意. 生物礁是一个常用术语,但1950年W.H.童豪富曾引述许多人对它的解释,说明对这一概念的理解各人并不一致,并由此产生了生物丘(bioherm)、生物层(biostrome)、碳酸盐岩隆(carbonate buildup)等同义或近义的词.根据最近30年来沉积学资料,可以认为生物礁是由于造礁生物的活动形成的、原地生长的抗浪构 相似文献
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新疆巴楚地区中上奥陶统生物礁群落古生态学 总被引：8，自引：0，他引：8
新疆巴楚东部地区良里塔格山出露有中奥陶统达瑞威尔阶一间房组和上奥陶统中部凯迪阶良里塔格组的生物礁。一间房组礁的厚度为数米到十多米,以棘屑滩为礁基,主要造礁生物为托盘类,形成典型的骨架岩,托盘类中央腔形成的原生孔隙发育,基质为灰泥,纹层状、皮壳状的藻类缠结包裹托盘类生长,可定为皮壳状藻托盘类密群落。良里塔格组的礁体主要由分枝状绿藻形成骨架岩,基质为灰泥,原有的原生或次生孔隙现被亮晶方解石充填;该组下部一些直径约1 m的小型礁由丰富的分枝状绿藻和少量乳孔藻构成,为分枝状绿藻密群落。良里塔格组上部较大的礁体（直径10~30 m）由分枝状绿藻和一种未知的球状生物（可能也是绿藻）构成,可称为“球状藻”分枝状绿藻密群落。 相似文献
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广西田林县龙江垌见晚石炭世的珊瑚格架礁,分三层旋回式生长于海百合碎屑滩上。造礁生物为丛状群体珊瑚Diphyphyllum sp.,附礁生物主要是海百合、腕足动物、藻类和有孔虫。造礁生物种群间仅是共同栖息生存,缺乏长期、稳定、复杂的生态关系,礁体生物群落成熟度低,除Diphyphyllum sp.搭建格架外,缺少其他造礁方式,在当时多变的水动力条件下,只形成了未成熟的层礁。对于龙江垌珊瑚礁生态特征形成原因归纳为以下几点:石炭纪中期全球地质构造变化影响、微生物群团和藻类造礁作用不明显、海百合的强大竞争作用使底栖生物群落受到抑制、Diphyphyllum sp.生态特点使其造礁能力差。 相似文献
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我国海南岛及南海诸岛沿岸,广泛发育海滩岩。1980年我队赴海南岛考察现代沉积时,对海滩岩的分布、岩性特征及其与周围环境的关系进行了观察和采样。样品采自崖县鹿回头三亚湾水尾岭海蚀崖、西洲岛、小东海、东瑁岛、西瑁岛、天涯海角,乐东县莺歌海,文昌县渔业等地(图1)。有关的地质、地貌及岩性特征等,已有许多描述,对海滩岩的岩石学及成岩作用也有许多研究。本文侧重探讨海滩岩的胶结作用及与成岩环境的关系。 相似文献
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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
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GREGORY E. WEBB LUKE D. NOTHDURFT BALZ S. KAMBER† J. T. KLOPROGGE‡ JIAN-XIN ZHAO§ 《Sedimentology》2009,56(5):1433-1463
Rare earth element geochemistry in carbonate rocks is utilized increasingly for studying both modern oceans and palaeoceanography, with additional applications for investigating water–rock interactions in groundwater and carbonate diagenesis. However, the study of rare earth element geochemistry in ancient rocks requires the preservation of their distribution patterns through subsequent diagenesis. The subjects of this study, Pleistocene scleractinian coral skeletons from Windley Key, Florida, have undergone partial to complete neomorphism from aragonite to calcite in a meteoric setting; they allow direct comparison of rare earth element distributions in original coral skeleton and in neomorphic calcite. Neomorphism occurred in a vadose setting along a thin film, with degradation of organic matter playing an initial role in controlling the morphology of the diagenetic front. As expected, minor element concentrations vary significantly between skeletal aragonite and neomorphic calcite, with Sr, Ba and U decreasing in concentration and Mn increasing in concentration in the calcite, suggesting that neomorphism took place in an open system. However, rare earth elements were largely retained during neomorphism, with precipitating cements taking up excess rare earth elements released from dissolved carbonates from higher in the karst system. Preserved rare earth element patterns in the stabilized calcite closely reflect the original rare earth element patterns of the corals and associated reef carbonates. However, minor increases in light rare earth element depletion and negative Ce anomalies may reflect shallow oxidized groundwater processes, whereas decreasing light rare earth element depletion may reflect mixing of rare earth elements from associated microbialites or contamination from insoluble residues. Regardless of these minor disturbances, the results indicate that rare earth elements, unlike many minor elements, behave very conservatively during meteoric diagenesis. As the meteoric transformation of aragonite to calcite is a near worst case scenario for survival of original marine trace element distributions, this study suggests that original rare earth element patterns may commonly be preserved in ancient limestones, thus providing support for the use of ancient marine limestones as proxies for marine rare earth element geochemistry. 相似文献
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Johannes H. Schroeder 《Sedimentary Geology》1973,10(3):179-204
Well-rounded pebbles and cobbles of reef rock, which in bio- and lithofacies closely resembles the Recent algal cup reefs, occur in the basal conglomerate of the Pleistocene Devonshire Formation cropping out along Grape Bay on the south shore of Bermuda. The framebuilders of this rock include coralline red algae, vermetid gastropods, and barnacles. Study by petrographic microscope, electron microprobe, and SEM revealed aragonite-needle and spherulitic cements, high-Mg calcite micrite and palisade cements including calcified algal filaments. Two or three generations of these may occur in a given pore. By analogy with the Recent cup-reef material, on the basis of their composition (high strontium content of aragonite, high magnesium content of calcite) and of circumstantial evidence, these are considered submarine cements.In addition, a vadose blocky low-Mg calcite cement occurs, which never precedes any, but frequently succeedes one, two, or three of the above cements. Its fabrics vary: it may exhibit an increase in crystal size toward the center or not, it may or may not be bounded by the meniscus outline characteristic of the vadose diagenetic environment. The limitation of cement precipitation by a meniscus gives rise to a large diversity of forms determined by respective combinations of solution supply, permeability of the micro-environment, and substrate morphology. To illustrate the diversity, the meniscus cement is shown in relation to sediment particles, aragonite-needle cement, and calcified filaments.From the blocky low-Mg cement, selective neomorphism extends into some aragonitic gastropod shells; it is controlled, in part, by original shell structure. The resulting low-Mg calcite mosaic is characterized by relic structures and plane crystalline boundaries. Aragonite needles between blocky calcite cement and neomorphic calcite were not affected by the process of mineralogic alteration.This study shows that cements recognized earlier in Recent Bermuda cup reefs can be traced into the past and that additions to the diagenetic sequence can be distinguished. Knowledge of these features and their sequences should help decipher the diagenetic history of other fossil reefs. 相似文献
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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
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New interpretations of Great Salt Lake ooids and of ancient non-skeletal carbonate mineralogy 总被引：2，自引：0，他引：2
PHILIP A. SANDBERG 《Sedimentology》1975,22(4):497-537
Earlier interpretations of textural alteration affecting Great Salt Lake ooids have greatly influenced concepts of ooid diagenesis. Scanning electron microscope study shows, however, that the coarse radial aragonite rays are depositional, that no recrystallization of pellet cores has occurred, and that Great Salt Lake ooids have not suffered noticeable diagenesis. As suggested by Kahle (1974), radial texture in ancient calcitic ooids is probably mainly original, not diagenetic. Retention of such fine textures has been attributed to organic matter (since found to be equivalent in modern skeletal and non-skeletal grains) or to paramorphic replacement (proposed for non-skeletal grains whose original aragonite mineralogy was only inferred from modern analogs). Pleistocene ooids known to have been aragonite alter like aragonite shells to coarse neomorphic calcite, often with aragonite relics. The striking uniformity of that coarse texture in neomorphic calcite replacing known skeletal aragonites throughout the geologic record has been noted for over 100 years. In contrast, Mississippian ooids retain fine texture as do calcite layers of coexisting gastropods, but unlike the strongly altered aragonite layers of these same gastropods. Therefore, inferences of original aragonitic mineralogy of ancient non-skeletal carbonate grains (including muds) which are now calcite but retain fine texture appear unwarranted, as do assumptions of differential diagenetic behaviour of ancient aragonitic skeletal and non-skeletal grains. Accordingly, modern depositional environments of marine ooids and carbonate muds must be rejected as chemically unrepresentative of comparable ancient environments. It is inferred that ancient non-skeletal carbonates were originally predominantly or exclusively calcite because of an earlier lower oceanic Mg/Ca ratio (<2/1) which altered progressively to values favouring aragonite (modern Mg/Ca value = 5/1). Major influencing factors are: selective removal of calcium by planktonic foraminifers and coccolithophorids since Jurassic-Cretaceous time and by abundant younger, Mg-poor aragonite skeletons and an erratic trend toward decreasing dolomite formation (decreasing removal of oceanic Mg). The change to aragonite dominance over calcite for non-skeletal carbonates was probably during early to middle Cenozoic time. 相似文献
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AXEL MUNNECKE HILDEGARD WESTPHAL† JOHN J. G. REIJMER† CHRISTIAN SAMTLEBEN 《Sedimentology》1997,44(6):977-990
Comparison of ultrastructures in Pliocene periplatform carbonates from the Bahamas with Silurian limestones from Gotland (Sweden) reveals that despite the differences in primary sediment composition and age, they reflect a similar mechanism of lithification. In both sequences calcite microspar was formed as a primary cement at an early stage of marine burial diagenesis. Neither significant compression nor meteoric influence are necessary for the formation of calcite microspar. A model is proposed for the process of microsparitic cementation of fine-grained aragonite needle muds comprising four stages: (1) unconsolidated, aragonite-dominated carbonate mud; (2) precipitation of microspar that engulfs aragonite needles; (3) dissolution of aragonite, resulting in pitted surfaces of the microspar crystals; and (4) slight recrystallization. Our results contradict the widespread opinion that microspar necessarily is a product of secondary recrystallization of a previously lithified micrite. 相似文献