新疆塔里木塔中井区上奥陶统良里塔格组的生物绑结岩

塔里木板块塔中井区上奥陶统凯迪阶良里塔格组灰岩中底栖固着型的钙质微生物、钙藻以及动物苔藓虫、珊瑚、层孔虫,可通过障积、盖覆和粘结等方式形成多种类型的生物绑结岩。对15口井部分岩芯以常用的绑结岩分类方案作岩石学微相分析,并描记底栖固着型生物颗粒的形成特征。菌藻类可在内碎屑表面以包结方式形成粘结岩;钙藻,特别是分枝状钙藻可形成障积岩;层孔虫可被隐藻层纹包结,也可单独形成小型盖覆岩;床板珊瑚格架岩可大量障积生屑和灰泥基质;苔藓虫在动物格架岩比例上占优,可与菌藻类粘结岩互相包结生长,也可独立形成局部小型障积岩。对比巴楚露头区同期藻丘中的绑结岩特征,显示塔中良里塔格组代表晚奥陶世由高生物多样性形成的礁滩复合体生态群落。     

华南板块古生代生物礁及其古地理控制因素

华南板块在古生代处于中、低纬度,碳酸盐岩类型多样并形成不同时空背景下的多种生物礁建造,生物礁发展序列基本吻合于全球古生代生物礁的宏演化趋势,寒武纪生物群和古生代动物群演化过程中重要造礁生物门类的起源、辐射、灭绝与复苏事件是塑造礁群落基本生态结构的历史因素。寒武纪早期的古杯-藻礁和继之的微生物礁生长区域相当局限;早—中奥陶世的苔藓虫礁、藻礁以及瓶筐石-硬海绵礁群落分异明显;晚奥陶世珊瑚-层孔虫礁以及藻丘建造见于浙赣局限台地及台缘带,而扬子区志留纪兰多维列世生物礁的生长频繁受陆源碎屑岩覆盖;中泥盆世的珊瑚-层孔虫-藻礁群落结构相对稳定,晚泥盆世法门期—密西西比亚纪的微生物礁、苔藓虫-珊瑚礁、宾夕法尼亚亚纪—早二叠世的苔藓虫-海绵-藻礁、中—晚二叠世的珊瑚-苔藓虫-海绵-藻礁可诠释为与生物灭绝事件相关的幕式群落演替。区域构造活动导致的岩相分异和海平面变化显著制约生物礁的时空分布。中—晚奥陶世的偏深水环境、志留纪兰多维列世—早泥盆世早期扬子区整体抬升的古地理格局造成适宜于生物礁生长海域的缩减;泥盆纪较长的温室期促进了生物礁发展,而宾夕法尼亚亚纪—早二叠世偏凉的海洋水体对生物礁的规模影响力度明显。从华南板块古生界整体的视角看,海相碳酸盐岩具有量值优势,海水在时间尺度和空间展布上多维持较高的清澈度,陆源碎屑岩沉积在特定的时间段可视为生物礁生长的主控因素;海平面变化因其幅度有限可在单剖面或区域上控制生物礁群落的纵横迁移,碳酸盐岩沉积区多见基底沉降与沉积补偿速率基本均衡,具备不同规模的浅海相沉积空间,因此水深变化并非起到决定性作用。特定时段碳酸盐岩台地海水的盐度异常可造成大规模白云岩沉积可排除生物礁发育。     

钙质海绵之古生态

古生代生物礁中钙质海绵(纤维海绵、房室海绵、硬海绵)的生态位在中三叠世以后被生态竞争能力更强的六射珊瑚所占据.在古生代和中三叠世的钙质海绵礁上,0-10m深度内钙质海绵很发育.由于与钙藻共生,典型的造礁钙质海绵生活在透光带以内,并且在其上部更丰富.钙质海绵礁也会生长到破浪带内并受风浪的破坏而形成倒骨岩和骨屑岩.对古生代的钙质海绵礁而言,倒骨岩和骨屑岩形成于0-3m水深范围内,亮晶骨架岩形成于3-10m深度范围内,灰泥骨架岩形成于10-20m的水深,障积岩形成于20-30m的水深,潜障积岩形成于30-40m的水深.钙质海绵的生长形态与水深的关系与六射珊瑚与水深的关系一样:细枝状的钙质海绵生长在最浅的水中(相当于礁生长带的上部),在稍深的水中(相当于礁生长带的中部和下部)各种形态的海绵都会出现,在更深的水中可以出现特别大的、锥状的海绵.     

泥质对志留系礁滩生长的抑制作用:黔北桐梓韩家店组的例证

黔北桐梓的戴家沟剖面和狮溪剖面志留系兰多维列统特列奇阶下部的韩家店组出露完好,该组泥岩、粉砂岩中夹有厚度1—3m、直径4—7m的小型点礁。礁核相多具典型的障积格架岩特征,但生长时限短暂,群落分异度低,仅见床板珊瑚、单体四射珊瑚、苔藓虫和海百合茎,礁间为珊瑚、苔藓虫和海百合茎碎片堆积的滩相,伴生丰富的遗迹化石。在陆源碎屑快速沉积的背景下,浑浊海水频繁的富营养化过程限制了礁体纵横向生长和朝高分异度群落发展的可能性。     

新疆塔里木中央隆起区中2井上奥陶统良里塔格组礁滩沉积相和测井参数

塔里木中央隆起区中2井位于塔中南坡台缘带,上奥陶统凯迪阶良里塔格组频繁出现浅水粒屑滩沉积,以及由蓝藻、钙藻兼以少量珊瑚、苔藓虫等造礁生物以不等含量分别构成生物障积或粘结型礁灰岩,棘皮类、腕足类和三叶虫等壳相生物碎屑丰富。可分出数层典型的生物礁、滩组合序列,总体显示为原地生长和近源搬运的生物礁滩复合体建造。环境的动能条件略有变化,但皆属浪基面之上的沉积深度。礁、滩储层形成模式主要受于沉积相带、成岩改造的控制,储层以生屑灰岩、藻粘结灰岩、障积灰岩及砂屑灰岩为主,储集空间类型包括次生溶蚀孔隙、晶洞与裂缝,同时伴随少量的白云岩化作用,且孔隙以深埋藏溶蚀成因为主,次生胶结作用也十分强烈,礁相储层潜力好于滩相。     

陕南川北志留系特列奇阶宁强组礁相中的微生物岩和钙藻

分布于扬子区西北缘宁强-广元地区志留系宁强组以约三千米厚的浅水相泥页岩,海相红层夹灰岩为特征,部分灰岩层段中发育生物礁,通过对礁灰岩的微相分析表明,菌藻类可通过四种方式参与造礁过程;1）叠层石;2）凝块岩;3）核形石;4）钙藻碎屑堆积,其中以叠层石和凝块岩最为常见,它们对灰泥基质起显著的粘结作用。而核形石和钙藻相对较少,有的叠层石出现于礁顶相并作为后生动物骨架岩造礁衰减的标志。     

鄂尔多斯盆地西南缘陕西陇县晚奥陶世背锅山组生物礁

鄂尔多斯盆地西南缘的陕西陇县李家坡晚奥陶世背锅山组生物礁为典型的台地边缘礁,包括层孔虫礁、珊瑚礁、钙藻礁等几种类型,主要为层孔虫礁。经过系统古生物学研究,鉴定出层孔虫有5个属,分别为Ecclimadictyon(蜂巢层孔虫)、Clathrodictyon(网格层孔虫)、Tuvaechis(图瓦层孔虫)、Rosenella(罗森层孔虫)、Labechiella(小拉贝希层孔虫)等;珊瑚有6个属,分别为Tetradium(四分珊瑚),Hemiagetolitella(拟半阿盖特珊瑚),Plasmoporella(似网膜珊瑚),Eofletcheria(始弗莱契珊瑚),Catenipora(镣珊瑚),Reuschia(劳氏珊瑚);钙藻以Vermiporella(蠕孔藻)和Solenopora(管孔藻)为主。礁发育早期以层状层孔虫包卷砂屑、单体珊瑚、管状海绵、块状钙藻等形态为主要特征,礁发育中后期以块状和球状的层孔虫以及大型的床板珊瑚形成格架为主要特征。礁体发育过程中居礁生物都很丰富,有三叶虫、腕足类、介形类、大棘皮类和丛状的蓝细菌等。通过与塔中台地以及扬子台地的晚奥陶世台缘礁对比,发现造礁生物的属种和礁岩类型均有相似之处,说明中国晚奥陶世生物礁的分布具有等时性。     

浙赣交界地区上奥陶统三衢山组礁灰岩的分类

本文讨论了礁灰岩的分类历史,特别对Ｔｓｉｅｎ,Ｈ．Ｈ．的礁灰岩分类系统进行了介绍．浙赣交界地区上奥陶统三衢山组生物礁发育良好,通过对其所含造礁生物的形态及功能分析,区分出五大类礁灰岩,即格架岩、障积岩、盖复岩、绑结岩和生物粘结岩,并指出生物礁礁核相主要由以上各种礁灰岩的复合类型所组成．     

新疆巴楚中奥陶统上部一间房组瓶筐石礁丘的演化意义

从建造时代和群落组成的角度,专论新疆巴楚地区一间房组瓶筐石礁丘的演化定位。瓶筐石作为群落的主体造礁始于早奥陶世早期,繁盛于早奥陶世晚期,中奥陶世开始趋于衰落。一间房组发育中小型点礁丘,除礁灰岩中常见的藻屑外,主要由瓶筐石并伴生少量石海绵共同形成礁格架岩。在群落组成上,一间房组的瓶筐礁丘与世界其它地区的瓶筐礁类似,但在建造时间上却显得极为特殊:中奥陶世晚期。这时,一个全新的群落——珊瑚—层孔海绵礁群落开始在世界其它地区起源,却全然不见于一间房组。一间房组的礁丘在时间上完全不吻合于早奥陶世的瓶筐石造礁事件,而是晚于此类礁繁盛期并滞后了约10Ma,是目前所发现这类礁群落在全球范围内的孓遗孤例,是承先而不启后的礁群落。     

宁强广元地区志留系宁强组灰岩的微相研究

志留纪时期在扬子地台西北缘宁强湾沉积的宁强组,是一套巨厚的泥页岩夹小型局限台地相灰岩。局限台地相灰岩的沉积类型主要有生物礁、生物层和灰泥丘三种,按岩性可分为灰泥岩、颗粒岩、障积岩、粘结岩、格架岩、漂浮岩、灰砾岩等类型。岩石的微相分析和宏观相带的识别相结合,能指示各种沉积类型不同部位的环境和形成机制。     

The history of Devonian-Carboniferous reef communities: Extinctions,effects, recovery

Summary Analysis of the taxonomic composition, diversity and guild structure of five “typical” reef and mud mound communities ranging in age from Late Devonian-Early Carboniferous indicates that each of these aspects of community organization changed dramatically in relation to three extinction events. These events include a major or mass extinction at the end of the Frasnian; reef communities were also effected by less drastic end-Givetian and mid-late Famennian extinctions of reef-building higher taxa. Peak Paleozoic generic diversities for reef-building stromatoporoids and rugose corals occurred in the Eifelian-Givetian; reef-building calcareous algal taxa were longranging with peak diversity in the Devonian. These three higher taxa dominated all reef-building guilds (Constructor, Binder, Baffler) in the Frasnian and formed fossil reef communities with balanced guild structures. The extinction of nearly all reef-building stromatoporoids and rugose corals at the end of the Frasnian and the survival of nearly all calcareous algac produced mid-late Famennian reef communities dominated by the Binder Guild. Despite the survival of most calcareous algae and tabulate corals, the mid-late Famennian extinction of all remaining Paleozoic stromatoporoids and nearly all shelf-dwelling Rugosa brought the already diminished Devonian reef-building to a halt. These Devonian extinctions differ from mass extinctions by the absence of a statistically significant drop in taxonomic diversity and by their successional and cumulative effects on reef communities. Tournaisian mud mounds contain communities markedly different from the frame-building communities in Late Devonian and Visean reefs. Mound-building biotas consist of an unusual association dominated by erect, weakly skeletonized members of the Baffler Guild (chiefly fenestrate Bryozoa; Pelmatozoa) and laterally expanded, mud-binding algae/stromatolites and reptant Bryozoa. The initial recovery to reefs with skeletal frameworks in the Visean was largely due to the re-appearance of new species of abundant colonial rugose corals (Constructor Guild) and fenestrate Bryozoa. This Frasnian-Visean evolution in the taxonomic composition and structure of the reef-building guilds is also expressed by abrupt changes in biofacies and petrology of the reef limestones they produced. Thus, “typical” Frasnian reef limestones with balanced guild structures are framestones-boundstones-bafflestones, Famennian reefs are predominantly boundstones, Tournaisian mud mounds are bafflestones and Visean reefs are bafflestones-framestones.     

Plaeocene reef sediments from the maiella carbonate platform,Italy

Summary Upper Cretaceous and Paleocene reef limestones from the Maiella carbonate platform show how reefs evolved during a time of faunal turn-over. Biostratigraphy and facies analysis of the reef limestones reveal the details of reef growth, composition, and age. Rudists disappeared as reef builders from the Maiella platform shortly before the Cretaceous/Tertiary boundary. Small coral-algal reefs became established in the Danian to Late Thanetian. These scleractinian-red algal dominated boundstones and framestones represent two periods of reef sedimentation and the subsequent interruption of reef growth by emersion and erosion, controlled primarily by fluctuations of relative sea-level. The coral-algal reefs evolved as the taxonomic composition of reef organisms changed. The Paleocene reef sediments are preserved as large slide blocks and as boulders redeposited from the shallow-water platform onto the slope during the course of the Paleocene.     

A modern-type Kimmeridgian reef (Ota Limestone,Portugal): Implications for Jurassic reef models

Upper Jurassic reefs rich in microbial crusts generally appear in deeper (sponge—‘algal’ crust reefs) or in very shallow but protected settings (coral or coral-coralline sponge meadows with ‘algal’ crusts). Upper Jurassic high-energy reefs (coral reefs and coral-stromatoporoid reefs) normally lack major participation of microbial crusts but rather represent huge bioclastic piles with only minor framestone patches preserved. An exception to this rule is represented by the high-energy, coral-‘algal’ Ota Reef from the Kimmeridgian of the Lusitanian Basin (Portugal). The narrow Ota Reef tract rims a small intra-basinal carbonate platform exhibiting perfect facies zonation (from W to E: Reef tract, back reef sands, peritidal belt, low-energy shallow lagoon). The reef is dominated by massive corals (Thamnasteria, Microsolena, Stylina). Complete preservation of coral framework is rare: like other Upper Jurassic high-energy reefs, the Ota Reef is very rich in debris; however, this debris is largely stabilized by algal and microbial crusts, what contrasts the other examples and gives the Ota Reef the appearance of a typical modern high-energy coral-melobesioid algal reef. Further similarities to modern reefs are the likely existence of a spur-and-groove system, the perfect sheltering of inner platform areas and the occurrence of small islands, as indicated by local blackenings and early vadose and karstic features.     

Ramp morphology controlling the facies differentiation of a Late Ordovician reef complex at Bachu,Tarim Block,NW China

A carbonate ramp in the shallow‐marine northwestern part of the Central Tarim Uplift, Bachu, NW China, exhibits an extraordinary Late Ordovician reef complex along the Lianglitag Mountains, exposed for a distance of about 25 km. Seven localities within the ‘Middle Red Limestone’ of the Upper Member of the Lianglitag Formation (Katian, Late Ordovician) illustrated the changes in biofacies and lithofacies: northern, seaward‐directed patch reefs are replaced towards the south by coeval grain banks. The patch reef units are dominated by microbial and calcareous algal components. The reefs at the northernmost locality are knoll‐shaped, kalyptra‐shaped or irregularly shaped with sizes of individual reefs increasing from about 2 m in height and diameter. Stratigraphically upward, reefs notably expand to larger structures by several mounds coalescing; they are generally about 10 m thick and tens of metres in lateral extent. The maximum thickness of the main patch reef is more than 30 m, and its diameter is around 100 m. The reefal units turn into biostromes with gentler relief southward and still further south grade into banks composed of peloids and coated grains. The southernmost locality is still a shallow‐water bank, and the coastline is not documented in the study area. The present evidence indicates that the Late Ordovician palaeo‐oceanography provided a number of environments for the optimal growth of carbonate build‐ups; microbial‐calcareous algal communities could thrive in areas where the innovative metazoan reef frameworks consisting of corals and stromatoporoids did not play a significant role. The ramp morphology, especially changes in water depth, controlled the configuration of the reef complex.     

Anthracoporella mounds in the Late Carboniferous Auernig Group,Carnic Alps (Austria)

Summary A heretofore undocumented example of skeletal mounds formed by the dasycladacean algaAnthracoporella spectabilis is described from mixed carbonate-clastic cycles (Auernig cyclothems) of the Late Carboniferous (Gzhelian) Auernig Group of the central Carnic Alps in southern Austria. The massive mound facies forms biostromal reef mounds that are up to several m thick and extend laterally over more than 100 m. The mound facies is developed in the middle of bedded limestones, which are up to 16 m thick. These limestones formed during relative sea-level highstands when clastic influx was near zero. The mound facies is characterized by well developed baffler and binder guilds and does not show any horizontal or vertical zonation. Within the massive mound faciesAnthracoporella is frequently found in growth position forming bafflestones and wackestones composed of abundantAnthracoporella skeletons which toppled in situ or drifted slightly.Anthracoporella grew in such profusion that it dominated the available sea bottom living space, forming ‘algal meadows’ which acted as efficient sediment producers and bafflers. BecauseAnthracoporella could not provide a substantial reef framework, and could not withstand high water turbulence, the biostromal skeletal mounds accumulated in shallow, quiet water below the active wave base in water depths less than 30 m. The massive mound facies is under- and overlain by, and laterally grades into bedded, fossiliferous limestones of the intermound facies, composed mainly of different types of wackestones and packstones. Individual beds containAnthracoporella andArchaeolithophyllum missouriense in growth position, forming “micromounds’. Two stages of mound formation are recognized: (1) the stabilization stage when bioclastic wackestones accumulated, and (2) the skeletal mound stage when the sea-bottom was colonized byAnthracoporella and other members of the baffler and binder guilds, formingAnthracoporella bafflestones and wackestones of the mound facies. A slight drop in sea-level led to the termination of the mound growth and accumulation of organic debris, particularly calcareous algae, fusulinids, crinoids and bryozoans, forming well bedded limestones, which overlie the mound facies     

Paleoecology of Middle Ordovician stromatoporoid mounds in Vermont

Fossiliferous mounds of carbonate mud are a distinctive facies in the middle Chazy Group (Crown Point Formation) at Isle La Motte, Lake Champlain. The mounds are surrounded by bedded calcarenite of spar-cemented pelmatozoan debris. Channels which cut into the mounds during mound growth are filled with the same calcarenite. The mud-free intermound rocks and the mound biota suggest agitated, normal marine shallow-water environments. The principal lime-secreting organisms within the mounds are stromatoporoids, calcareous algae, tabulate corals, sponges, and bryozoans. Each mound is dominated in terms of biomass by one of three groups: stromatoporoids, calcareous algae, and bryozoans. Most of the mound biota first appear at the base of the Crown Point Formation. In the lower Crown Point Formation the organisms increase in number and species. Both changes in the biota are related to periods of shallowing of the Chazy sea which are also reflected in the character of the carbonate sands.     

A late-devonian (Famennian)Renalcis-Epiphyton reef at Zhaijiang, Guilin, South China

Summary Microbial reefs, together with stromatolitic mounds and ooid shoals, constitute massive limestones in Famennian platform marginal strata in Guilin, in sharp contrast to the well-known coral-stromatoporoid reefs in the Givetian and Frasnian. Microbes played a significant and important role as stabilizers in the Famennian carbonate deposits of Guilin. A reef at Zhaijiang was constructed byEpiphyton andRenalcis, and is representative of such carbonate buildups. The reef is situated 10 km west of Guilin and corresponds to a microbe-dominated platform margin carbonate complex. Organisms in the Zhaijiang microbial reef are low diversity and dominated by ostracods and two genera of microbes,Epiphyton andRenalcis. Other microbial genera such asSphaerocodium andWetheredella occur in most of reef facies in Guilin, but their role as reef builder is doubtful because they occur only in minor amounts. The same four genera occur in volumetrically significant amounts in the upper Devonian carbonate complexes of Alberta. Canada and Western Australia. However.Epiphyton is more abundant in the Guilin reefs. The Zhaijiang microbial reef developed above Famennian proximal slope faices, as suggested by reef architecture and paleogeographic setting. The facies sequence of the microbial reef can be divided into three parts. The lower part is composed of medium-bedded bioclastic grainstones with a few microbial framestone lithoclasts, representing a proximal slope facies. The middle part consists of thin-bedded mudstone and shale with limestone lenses that are thought to be low stand deposits. In some cross sections, mudstone and shale infilled tidal channels that developed in the bioclastic grainstones.Renalcis-Epiphyton framestone constitutes the upper part with massive stacking patterns. The reef is 35 m thick and over 50 m in width. Nine litho- and biofacies are recognized. Zhaijiang reef provides an example of a binder guild-dominated buildup in the almost vacant reef ecosystem of the Famennian and represents a characteristic kind of reef after the Frasnian/Famennian extinction.     

A geospatial assessment of the relationship between reef flat community calcium carbonate production and wave energy

The ability of benthic communities inhabiting coral reefs to produce calcium carbonate underpins the development of reef platforms and associated sedimentary landforms, as well as the fixation of inorganic carbon and buffering of diurnal pH fluctuations in ocean surface waters. Quantification of the relationship between reef flat community calcium carbonate production and wave energy provides an empirical basis for understanding and managing this functionally important process. This study employs geospatial techniques across the reef platform at Lizard Island, Great Barrier Reef, to (1) map the distribution and estimate the total magnitude of reef community carbonate production and (2) empirically ascertain the influence of wave energy on community carbonate production. A World-View-2 satellite image and a field data set of 364 ground referencing points are employed, along with data on physical reef characteristics (e.g. bathymetry, rugosity) to map and validate the spatial distribution of the four major community carbonate producers (live coral, carbonate sand, green calcareous macroalgae and encrusting calcified algae) across the reef platform. Carbonate production is estimated for the complete reef platform from the composition of these community components. A synoptic model of wave energy is developed using the Simulating WAves Nearshore (SWAN) two-dimensional model for the entire reef platform. The relationship between locally derived measures of carbonate production and wave energy is evaluated at both the global scale and local scale along spatial gradients of wave energy traversing the reef platform. A wave energy threshold is identified, below which carbonate production levels appear to increase with wave energy and above which mechanical forcing reduces community production. This implies an optimal set of hydrodynamic conditions characterized by wave energy levels of approximately 300 J m^?2, providing an empirical basis for management of potential changes in community carbonate production associated with climate change-driven increases in wave energy.     

Late Triassic reefs from the Northwest and South Tethys: distribution, setting, and biotic composition

The paleolatitudinal distribution patterns during Ladinian and Carnian time are characterized by an increasing expansion of reefs from the northern to the southern hemisphere. The optimum of reef diversity and frequency in the Norian is associated with the development of extended attached or isolated carbonate platforms. Norian-Rhaetian sponge and coral reefs of the Northern Calcareous Alps developed (1) as reef belt composed of patch reefs in platform-edge positions facing the open-marine northwestern Tethys basins and (2) as patch reefs in intraplatform basins as well as in ramp positions.Carnian and Norian-Rhaetian sponge and coral reefs of the Arabian Peninsula are formed (1) as reef complexes at the margins of carbonate platforms on the tops of volcanic seamounts in the southern Tethyan ocean, as small biostromes on these isolated platforms, and (2) as transgressive reef complexes on the attached platform of the Gondwana margin. The Norian Gosaukamm reefal breccia of the NW Tethys is a counterpart of Jabal Wasa reefal limestone of the Gondwana margin with similarities in geological setting and biotic composition. Rhaetian coral biostromes of low diversity known from the Austrian Koessen basin resemble to the time equivalent Ala biostromes of the isolated Kawr platform in the southern Neo-Tethys by forming a discontinuous layer in shallow intraplatform basin setting.