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1.
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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The framework‐building stromatoporoid Stachyodes, the encrusting calcimicrobe Rothpletzella and encrusting Graticula‐like red algae are major contributors to red algal–calcimicrobial–stromatoporoid bindstones in the Lower Devonian Elmside Formation of the Yass Basin, New South Wales, Australia. The distribution and accumulation patterns of encrusting organisms within the red algal–calcimicrobial–stromatoporoid bindstones observed by optical microscopy and SEM imply a biotic interrelationship between skeletal organisms and microbes that reflects environmental changes. Rothpletzella is characterized by prostrate filaments with frequent branching and a high angle of bifurcation. Filaments of Graticula‐like red algae exhibit rare branching and a relatively low angle of bifurcation. In addition, they are prostrate at the base before becoming erect. Both Rothpletzella and the red algae successively encrust the surfaces of skeletal frameworks, but exhibit different distributions. Rothpletzella and other calcimicrobes cover both the lower and upper surfaces of frameworks, whereas red algae are limited to the upper surfaces. Their individual distributions are thus significantly influenced by the frameworks formed by the thin, laminar stromatoporoid Stachyodes, which create different microenvironments as by‐products. The limited distribution of the red algae was probably related to light levels or phototropism. Upper framework surfaces are variously encrusted by calcimicrobes and the red algae to form thick crusts with varying accumulation patterns. Micritization around the algal thalli, covering of calcimicrobes such as Wetheredella, and microbial micrites between algal thalli all suggest interruptions of algal growth that correspond to episodes of harsh environmental conditions. Transitions from Graticula‐like red algae to Rothpletzella reflect periods of deteriorating environmental change for skeletal organisms, which resulted in the predominance of microbial growth. In contrast, a resurgence of red algae on calcimicrobes suggests improved environmental change. Repeated accumulation patterns between Graticula‐like red algae and Rothpletzella indicate changing habitat environments and competitive relations within skeletal organisms and microbes. These relationships provide insight into understanding how skeletal organisms and microbes utilized space and how they interrelated with each other to produce Devonian reefal limestones. 相似文献
4.
柴达木盆地西部古近纪—新近纪湖相生物礁的发现及意义 总被引：1，自引：0，他引：1
在柴达木盆地西部古近纪和新近纪地层中发育了典型的湖相生物礁,可以分为由基质支撑的叠层石礁、凝块礁和骨架支撑的藻礁3大类型,并对每种类型中亚类的特征和建造生物进行了简要介绍。生物礁孔隙度高、渗透性好,是优质储层。孔隙类型丰富多样,主要有骨架孔隙、体腔孔隙、粒内孔隙、溶孔等10种孔隙类型。生物礁的地震响应和测井曲线特征明显,在研究取心井段生物礁地球物理响应特征的基础上可以有效的识别和预测生物礁。综合应用古生物分析、孢粉分析、同位素分析、古地磁分析、地球化学分析和地球物理特征分析等技术手段,并结合生物礁发育的沉积条件和构造背景,初步探讨了生物礁对柴达木盆地古气候、古地理位置、古构造、古水介质、古沉积环境和青藏高原的隆升等方面的研究意义以及对油气勘探方面的意义。 相似文献
5.
The identification of the remains of organisms contributing to carbonate sediments by means of scanning electron-microscopy is limited to particles of the 2–20 μm size class. Mineralogy and the content of Mg, Sr and trace elements alone are usually insufficient to solve the problem of identification, especially in the differentiation between algal and coral aragonite. The organic matrix of calcareous organisms consists of stable biopolymers such as polysaccharides and glycoproteins which are intimately associated with the carbonate skeleton. Analysis of these hydrolysed compounds gives rise to characteristic arrays of monosaccharides which provide independent criteria for producer identification. The calcareous green algae Halimeda, Penicillus and Udotea show high xylose and low fucose levels. Xylose and fucose levels are elevated in the red algae Amphiroa but only fucose is prominent in the brown algae Padina. The corals Oculina, Porites, Millipora and Montastrea are relatively rich in fucose and show little or no xylose. In the bivalves Arca, Codakia and in Argopecten mannose may be characteristic. Analysis of artificial and natural sediments demonstrates that coral and algal aragonite can be distinguished on the basis of the total sugar concentration and respective xylose and fucose levels. The applicability of the technique in comparison to geochemical and mineralogical methods has been demonstrated for surface sediments from varying water depths of Harrington Sound, Bermuda. 相似文献
6.
Johannes H. Schroeder Ph.D. 《International Journal of Earth Sciences》1972,61(2):708-730
A variety of precipitative synsedimentary CaCO3 cements lines or fills cavities and surrounds sediment particles within Recent algal cup reefs which dot the rim of the Bermuda platform. These include aragonite needle, spherulitic, and lath cements as well as calcite micrite, palisade, scale, and blocky cements, listed according to respective relative abundances. No distribution pattern of cements is apparent; various combinations of three or four cements are found in almost every sample or thin section. From the occurrence of various cements, factors determining composition and fabric are deduced:
- Morphology, composition, and coating of the substrate.
- Direct or indirect influence of organisms such as algae, pelecypods, or crustaceans.
- Micro-environment, specifically size and permeability, rate of sea-water circulation through the micro-environment, substrates and organisms within the microenvironment.
7.
The complex pattern of biological accretion, internal sedimentation, early lithification, and biological destruction, that characterizes modern reefs and many fossil reefs has been recognized in archaeocyathid-rich patch reefs of Lower Cambrian age in the Forteau Formation, southern Labrador. Patch reefs occur as isolated masses or complex associations of many discrete masses of archaeocyathid-rich limestone and skeletal lime sands, surrounded by well-bedded skeletal limestones and shales. Each reef is composed of many loafshaped mounds stacked on top of one another. The limestone of each mound comprises archaeocyathids and Renalcis or Renalcis-like structures in a matrix of argillaceous lime mud rich in sponge spicules, trilobite and salterellid skeletons. Numerous growth cavities roofed by pendant Renalcis-like organisms and Renalcis are partially to completely filled with geopetal sediment indicating that much of the matrix was deposited as internal sediment. Two stages of diagenetic alteration are recognized: (1) syn-depositional, which affected only the reefs, and (2) post-depositional, which affected both reefs and inter-reef sediments. On the sea floor reef sediments were pervasively cemented and fibrous carbonate was precipitated in intraskeletal and growth cavities. These limestones and cements as well as archaeocyathid skeletons, were subsequently bored by endolithic organisms. Later post-depositional subaerial diagenesis resulted first in dissolution of certain skeletons and precipitation of calcite cement above the water table, followed by extensive precipitation of pore-filling calcite below the water table. These carbonate reefs are similar in structure to the basal pioneer accumulations of much younger lower and middle Palaeozoic reefs. They did not develop into massive ‘ecologic’ reefs because archaeocyathids never developed the necessary large, massive, hemispherical skeletons. This occurrence indicates that reefs developed more or less coincident with, and not long after, the appearance of skeletal metazoans in the Lower Cambrian. 相似文献
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Recent carbonate sediments from Jamaican north coast fringing reefs were collected along three parallel traverses in the vicinity of Discovery Bay. Each traverse extended from near shore across the back reef, reef crest, and fore reef to a depth of 75 m. Relative abundances of the biotic constituents vary between sites, reflecting general patterns of reef community composition. The sediment is dominated by highly comminuted coral fragments (27·1% to 63·1%), plates of the calcareous green alga Halimeda (0·4% to 38·7%), coralline algae (4·7% to 16·2%) and the encrusting foraminiferan Homotrema rubrum (0·7% to 9·5%), with lesser amounts of other taxonomic groups (non-encrusting foraminifera 1·3–5·5%; molluscs 1·4–7·0%; echinoderms 0·9–5·0%). Coral fragments, coralline algae and particles of Homotrema rubrum dominate the sediments of the shallow portions of the fore reef (5–15 m), whereas plates of Halimeda are most abundant in sediments from the back reef and deeper portions of the fore reef ( 24 m). Q-mode cluster analysis, using sediment constituent data, resulted in the delineation of four reef biofacies over the depth range of this study (1–75 m). 相似文献
10.
DAVIDE BASSI YASUFUMI IRYU MARC HUMBLET HIROKI MATSUDA HIDEAKI MACHIYAMA KEIICHI SASAKI SHINYA MATSUDA KOHSAKU ARAI TAKAHIKO INOUE 《Sedimentology》2012,59(7):2024-2041
Sandy and gravelly carbonate sediments found off Kikai‐jima, southern Japan, a coral reef‐related island shelf, represent the northernmost sub‐tropical, carbonate deposits in the Central Ryukyu Islands (Ryukyus). On the Kikai‐jima shelf, at water depths of 61 to 105 m, these sediments are characterized by macroid pavements. Since the abundance of very small and of exceptionally large macroids may indicate specific hydrodynamic controls regarding constraints on growth and taphonomy, the detailed analysis of recent and fossil macroid pavements is meaningful ecologically and environmentally. Macroids, ranging in size from ca 25 to 130 mm in diameter, are spheroidal and sub‐spheroidal in shape and consist mainly of the encrusting foraminifer Acervulina inhaerens and subordinate thin encrusting and lumpy coralline algae. Accessory components include bryozoans, serpulids and, to a lesser extent, encrusting arborescent foraminifera (Homotrema and Miniacina). Low sedimentation rates and occasional movement due to current action are indicated by sizes, shapes and growth‐forms of the studied macroids, the Entobia–Gastrochaenolites–Trypanites–Maeandropolydora ichnocoenosis and the ‘Bioerosion Index’ for coated grains (introduced herein). The deep‐water tidally induced current energy was sufficient to maintain multi‐directional growth (spheroidal shapes) of the larger macroids and to initiate macroid growth using the diverse biogenic remnants as nuclei. The asymmetrical inner arrangement suggests possible periods of stability for the macroids. The residence time of the coated grain in its original environment determines the size and morphology of the macroid and the selection of coating organisms. The composition of the coating community is mainly a consequence of component growth rates in relation to turnover time and residence time. Long‐term studies are needed to assess the spatial and temporal resolution of present‐day encrusting communities across biogeographic provinces and shelf to slope regions. 相似文献
11.
JULIAN E. ANDREWS 《Sedimentology》1986,33(4):499-520
Bathonian algal limestones from the Duntulm Formation of the Great Estuarine Group, western Scotland, are subdivided into three microfacies: cryptalgal laminites, thrombolites and porostromate-micrites. The distribution of early diagenetic, carbonate spherulites and cement fringes is fabric selective. Spherulites are common in the thrombolitic microfacies, whereas cement fringes were best developed upon algal nodules with porostromate microstructure. Syndiagenetic micrites, spherulites and cement fringes have stable carbon isotopic ratios indicative of abundant, organic-derived HCO3 incorporation (δ13C values of ?0·05 to ?15‰). Enhanced magnesium concentrations in these fabrics, relative to neomorphic and burial-diagenetic spar cements, suggest an original Mg-calcite mineralogy, probably with precipitation under the influence of microbial systems. Brecciated, early-diagenetic fabrics and localized pockets of calcite pseudomorphs after gypsum were probably formed during subaerial exposure. Sulphate supply was probably from storm-derived, saline lagoon-water washed on to supralittoral stromatolitic flats. These inundations also allowed the temporary establishment of green algae and encrusting foraminifera. The combined geological and geochemical information suggests a palaeoenvironment somewhat similar to Recent, sub-tropical humid zone, calcareous algal marshes. 相似文献
12.
世界上早二叠世生物礁分布于泛大陆的西北陆棚、乌拉尔山脉的西侧、美国的二叠盆地等地,并集中分布于前两个地区。其早期,以Palaeoaplysina礁或Palaeoaplysina和叶状藻礁占优势,而至晚期则形成以Shamovella (Tubiphytes)和苔藓虫为骨架的礁。中二叠世栖霞期的礁仅发现于北美格拉斯山脉、帕米尔和我国的阿尔格山等地。茅口期的礁是世界上最发育的生物礁之一,北美瓜德罗普山脉的二叠纪礁已成为世界上最典型的礁,其相带分异之清晰堪称为世界之最。北非突尼斯的礁也是研究程度较高的礁之一。中二叠世的礁以海绵、苔藓虫、Shamovella的大量出现为特征,古石孔藻、Shamovella和笛苔藓虫是常见的包覆生物。晚二叠世生物礁分布于欧洲镁灰岩统盆地、特提斯海西缘和最北缘的陆棚以及特提斯海域内的一些地体。我国晚二叠世礁十分发育,成为世界二叠纪礁的一个亮点。礁内的造架生物以珊瑚海绵为主,包括房室海绵和纤维海绵,古石孔藻和Shamovella (Tubiphytes)作为常见的包覆联结生物。 相似文献
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中国南方上震旦统灯影组中的古喀斯特洞穴磷块岩 总被引：1，自引：1，他引：1
晚震旦世,在中国南方存在一个大的碳酸盐台地,即大扬子台地。近来,在大扬子台地的次级单元-鄂西台地南北两侧边缘带的灯影组白云岩中发现古喀斯特洞穴磷块岩。北缘以湖北省南漳县的王家堡为代表,古喀斯特洞穴磷块岩不规则地分布于自灯影组上、下段之间的侵蚀面到其下约70m范围内。位于台地南缘的湖南大庸张家溪,古喀斯特洞穴磷块岩也产于灯影组下段白云岩内,据古生物学及地层学研究,张家溪灯影组下段上部白云岩中的洞穴磷块岩形成于早寒武世早期。古洞穴磷块岩的发现,证明灯影早期末有一次普遍而强烈的地壳运动,灯影晚期海侵的初期是晚震旦世除陡山沱期外的又一重要成磷期。 相似文献
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大地构造对上扬子区志留纪生物礁分布及发育的控制 总被引：5，自引：1，他引：5
根据上扬子板块的基底特征，及板块边缘特征等不同大地构造单元演化特征入手，分别对上扬子板块基底地貌、板块边缘构造及板内不同构造单元控制志留纪古沉积环境及生物礁发育演化进行了论述。在上扬子板块的北缘（南秦岭构造带），为被动大陆边缘，沉积环境适于生物礁发育，类型较多。而板块西缘（金沙江构造带）为主动大陆边缘，在岛弧区发育部分点礁以及生物层；板块内部受古隆起影响的地区（川西北、川东南、黔北），形成缓坡沉积环境，在浅缓坡区生物礁十分发育，类型众多；但是板内深断裂（龙门山，二郎山-攀西裂谷带）边缘生物礁不甚发育，仅见生物层-小型点礁组合。志留纪时，上扬子板块受全球海平面变化的影响明显，至Ｗｅｎｌｏｃｋ期后，大部分地区因海平面下降而无沉积。但是在板块边缘凹陷区，因区域构造的影响，全球海平面波动对其影响不大，Ｗｅｎｌｏｃｋ期后继续接受沉积且发育生物礁。 相似文献
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贵州紫云县猴场镇扁平村的上石炭统叶状藻礁及其周边灰岩中广泛发育大量的各类胶结物。通过对胶结物的形态、结构和阴极发光特征以及胶结物间的接触关系的研究,可以确定成岩作用的先后并识别成岩环境。浅海海底同生成岩阶段大的孔隙中形成等厚环边针状胶结物、葡萄状胶结物,小的孔隙里形成微晶胶结物。早成岩阶段形成微亮晶和斑块状亮晶方解石胶结物和放射纤维扇状胶结物,表生成岩阶段的溶蚀作用和胶结作用强烈,胶结物类型有斑块状或等粒的方解石胶结物和等厚环壁柱状胶结物,等厚环壁柱状胶结物在所有胶结物中体积是较大的。早期胶结作用使叶状藻礁灰岩孔隙度大为降低。中、晚成岩阶段,孔隙被等厚环壁刃状胶结物和晶簇或斑块状亮晶方解石所充填,有些先成的胶结物被热液改造。后生作用阶段发生的主要是构造破裂作用,其中少数裂隙被红褐色含Fe2O3微晶层和晶体粉砂及渗流豆粒充填。叶状藻礁灰岩的孔隙在晚成岩阶段前或中被胶结而之后没有创造出大且连通的孔隙,是它没能成为油气储集层的原因之一。 相似文献
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黔南地区宾夕法尼亚亚纪逍遥阶礁相地层中腕足动物普遍发育,主要产长身贝类和石燕贝类。本文主要研究该区腕足动物与造礁生物叶状藻和Fomitchevella 珊瑚之间的生态关系。在叶状藻礁内,小个体腕足动物常附着在藻叶上营假漂浮生活; 但藻叶密集处,小个体腕足动物也难见,可能藻丛造成水流循环不畅使腕足动物难以获得充足的食料; 藻叶稀疏处,腕足动物个体加大,数量增加。在大型Fomitchevella 珊瑚格架礁内,腕足动物与Fomitchevella 之间不存在食物上的竞争。腕足动物介壳层为Fomitchevella 幼虫定殖提供了生物成因的硬质基底,在此基础之上发育了大型珊瑚礁。腕足动物在 Fomitchevella 进入统殖阶段由于生态空间受到局限而退居次要地位。 相似文献
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东昆仑山脉西段二叠纪生物礁由早二叠世、中二叠世的栖霞期和茅口期三个层位组成，早二叠世的礁和中二叠世栖霞期的礁是我国首次发现的，填补了我国二叠纪礁的空白。早二叠世礁的时代相当于阿赛尔-萨克马尔-阿丁斯克期，主要表现为海绵礁、苔藓虫礁和Shamovella(Tubiphytes)-古石孔藻礁。但缺失由Palaeoaplysina组成的礁。中二叠世栖霞期的礁表现为海绵-苔藓虫礁、Shamovella-苔藓虫礁和叶状藻礁。中二叠世茅口期的礁与栖霞期的礁类型基本一致。阿尔格山礁是塔吉克斯坦-喀拉昆仑地体的一个部分，该地体位于南纬30°以北的东特提斯海内。此处的二叠纪礁由各种生物组成，包括珊瑚海绵、苔藓虫、Shamovella.古石孔藻、棘皮类、有孔虫、叶状藻、粗枝藻以及腹足类等，推测该礁形成于温暖和炎热气候条件下的暖水内，而非冷水礁。 相似文献
18.
On the experiemntal silicification of microorganisms. I. Microbial growth on organosilicon compounds
In the course of experimenting on the laboratory silification of algal cells and algal mats a series of organosilicon compounds was employed in attempts to simulate fossilization. These compounds provided a silica source for emplacement in the organic matrices of the algae. It was found that during the silicification process silicon acetate, triethoxysilane propylamine and tetraethylorthosilicate (tetraethoxysilane) yielded hydrolytic products which supported growth of microbes. Large numbers of microorganisms: several fungi, including yeast and an Aspergillus sp. and Pseudomonas aeruginosa were isolated from salt solutions containing these organosilicon compounds as the sole source of carbon. The rate of hydrolysis yielding silica for emplacement was not affected by growth of these microorganisms. The isolation and growth of pure cultures of P. aeruginosa on either triethylsilane propylamine or tetraethylorthosilicate is described. 相似文献
19.
晚二叠世是我国西南地区地史上的第二次造礁高峰期,礁体发育良好,分布广泛,类型齐全,且有较好的找矿前景,已先后在建南、石宝寨等潜伏礁体中打出了工业性气流。前人已对本区晚二叠世生物礁作了大量的研究,但主要侧重于古生物生态和礁体沉积相方面,而对海平面相对变化与礁体的关系以及礁控构造等方面的研究还很少。本文为《中国南方晚二叠世生物礁研究》课题成果中的一部份,主要探讨晚二叠世海平面相对上升与生物礁相沉积之间的关系。西南地区晚二叠世生物礁主要分布在南盘江地区(滇黔桂交界区)和川东鄂西地区,礁 相似文献
20.
Bermuda is a reef atoll along the northern edge of Caribbean coral province. Although investigated by seismic and some shallow drilling, the Pleistocene marine depositional geohistory is poorly constrained. Islands along the southern rim are built by tropical calcareous aeolianites that range in age from Holocene to early Pleistocene (ca 880 kyr). These dunes are composed of particles that were derived from adjacent Pleistocene marine environments at the time of formation. Thus, the aeolianites should contain a record of marine deposition through the Early to Late Pleistocene. Carbonate grains from all aeolian deposits can, via Ward cluster analysis, be separated into two distinct groups: (i) a Halimeda‐rich group; and (ii) a crustose coralline‐rich group. Distribution of these two groups is interpreted to broadly reflect low‐energy (lagoonal) and high‐energy marginal reef (coralline algae and cup‐reef) environments, respectively. Unlike the beach sources, coral particles are perplexingly absent in the aeolianites. This conundrum is interpreted to partly reflect the domal nature of Bermudan corals, which are not incorporated into aeolian deposits due to their relatively large size. Aeolianites from Marine Isotope Stages 7, 9 and 11 record sediments produced in adjacent shallow marine settings that were similar to those present today. The spatially consistent sediment trends are not, however, present in aeolianites from Marine Isotope Stage 5E, where the aeolian bioclastic components are uniformly rich in Halimeda along both southern and northern shores. Such a distribution, where coralline‐rich sediments would be expected, suggests an extrinsic oceanographic control, interpreted herein to be elevated seawater temperature brought in by the Gulf Stream. This interpretation is consistent with palaeozoological studies of Bermuda, as well as North America, the Mediterranean, Japan and Western Australia. 相似文献