西藏安多县东巧晚侏罗世生物礁的发现

首次发现西藏安多县东巧地区晚侏罗世生物礁,造礁生物以层孔虫和六射珊瑚为主,其中,层孔虫可分为枝状、筒状和块状三种类型,它们多以原地生长状态保存.礁岩石学特征研究表明,礁岩可分为筒状-枝状层孔虫障积岩、枝状层孔虫障积岩、筒状层孔虫障积岩、筒状-块状层孔虫障积-骨架岩和筒状层孔虫-六射珊瑚障积-骨架岩.礁体类型可分为筒状-枝状层孔虫障积岩隆礁、枝状层孔虫障积岩隆礁、筒状层孔虫障积岩隆礁、筒状-块状层孔虫障积-骨架岩隆礁和筒状层孔虫-六射珊瑚障积-骨架岩隆礁,礁体的演化均经历了奠基阶段、发育阶段和衰亡阶段.     

黔南宾夕法尼亚亚纪生物礁类型及其特征

黔南宾夕法尼亚亚纪海域广大,普遍发育了一套台地相碳酸盐岩.该区碳酸盐台地浅水非常适宜生物生存,特别是底栖生物大量繁盛,生物造岩作用十分强烈.宾夕法尼亚亚纪地层中含有极为丰富的底栖生物化石,其中包括多种造礁生物并建造了不同类型的生物礁,主要礁体有:Fomitchevella 珊瑚骨架礁、叶状藻骨架一障积礁、Ivanovia cf.manchurica珊瑚骨架一覆盖礁、未名造礁生物骨架礁、黏结生物Tubiphytes黏结礁.生物礁不仅种类较多,而且数量可观,反映了该时期生物礁的发展达到了较高的水平,应该是石炭纪生物礁发育的一次高潮期.     

黔南晚石炭世礁相地层中造礁生物Tubiphytes研究

广泛分布在黔南晚石炭世礁相地层中,具有多样的生物形态。其造礁作用以粘结方式为主,可以集中密集形成粘结岩礁块,也可以与其它造礁生物共同建造礁体。其建造的礁体分布局限,礁体一般规模不大。Tubiphytes在工作区除形成礁体外,还通过包覆其它生物碎屑和粘连灰泥和碎屑颗粒形成粘结岩,构成珊瑚礁体的基底,起到固结基底的作用;也可以在其它礁体内部粘结充填在礁骨架中的灰泥和碎屑颗粒形成块状粘结岩,起到加固礁体的作用。Tubiphytes与其它生物碎屑一起作为碳酸盐岩造岩的重要组成部分,在礁相地层中也广泛存在。Tubiphytes在黔南晚石炭世礁相地层中是一类具有特色的生物。     

重庆开县上二叠统长兴组红花生物礁成礁模式

通过对红花生物礁露头的精细解剖和微相分析,研究了礁的内部构成和成礁模式。红花生物礁发育3期礁体旋回：礁A、礁B和礁C。礁A由生屑泥晶灰岩和骨架岩构成;礁B由生屑泥晶灰岩、粘结岩、骨架岩和生屑灰岩构成;礁C由粘结岩、骨架岩和生屑灰岩构成。红花生物礁造礁生物有钙质海绵、钙藻类、苔藓虫和水螅类,附礁生物为有孔虫、腕足类、双壳类、腹足类和棘皮动物等。单个礁体内,由下往上的生物演化为：腕足类+双壳类+有孔虫组合→钙藻类→钙质海绵+水螅类+钙藻类+苔藓虫组合→生物碎屑;岩性演化为：生屑泥晶灰岩→粘结岩→骨架岩→生屑灰岩。礁B的生屑滩内生屑间为泥晶充填,生屑分选、磨圆较好,是由相邻的高能生屑滩侵蚀搬运到礁B侧翼低能区沉积形成。3期礁都发育在碎屑滩上,礁A为低能环境下形成的礁,礁B和礁C在礁A形成的高地上成礁,为高能环境礁;单个礁体的完整成礁模式为：在浅滩之上,钙藻类大量生长、粘结吸附颗粒固结基底,钙质海绵和钙藻类在硬质基底上繁茂生长,形成具有抗浪格架的生物礁,礁体暴露水面死亡后遭波浪、水流改造形成生屑滩。     

湘南上二叠统长兴组生物礁基本特征

湘南生物礁发育于上二叠统长兴组。该礁体的岩石组合类型有:骨架岩、障积岩、粘结岩等。组成礁体的生物极为丰富,类型繁多。造架生物有:串管海绵、纤维海绵、Tabulozoan、水螅类、四射珊瑚等。粘结生物有:Archaeolithoporella、Tubiphytes、Tabulozoan及蓝绿藻。附礁生物有:腕足类、有孔虫等。礁体发育大致可以分为四个阶段:萌芽期、发育期、繁盛期和衰亡期。从礁体的发育关系来看,具有海侵过程中向岸推移的趋势。     

川东北地区上二叠统长兴组生物礁组成及成礁模式

川东北地区在地表露头上目前发现的长兴组生物礁以盘龙洞、通江铁厂河和羊鼓洞生物礁为代表。野外和室内综合研究表明：盘龙洞生物礁发育完好,生长有大量骨架岩,而羊鼓洞生物礁骨架岩几乎不发育,以障积岩为主夹少量粘结岩;盘龙洞骨架间充填物为生物碎屑和砂屑为主,泥晶灰泥很少,而羊鼓洞以生物碎屑和方解石灰泥为主;盘龙洞生物礁普遍发生了白云岩化,而羊鼓洞白云岩化极其微弱。通过盘龙洞与羊鼓洞生物礁对比研究,认为两者非同时形成,羊鼓洞生物礁早于盘龙洞,生物礁有由台地向盆地迁移趋势,其成礁模式为台地边缘礁滩组合型缓坡模式。     

生物岩的分类

生物岩是新兴交叉学科生物岩石学的主要研究对象，是生物作用形成的岩石，主要包括生物礁岩、非造礁生物骨骼和泥晶组成的岩石、微生物骨骼组成的岩石、微生物作用形成的岩石。以往的生物礁和微生物岩分类系统只包括了一部分生物礁岩和微生物岩，尚有一部分宏体生物形成的岩石类型和微生物形成的岩石类型没有准确命名。为了促进生物岩的研究，作者提出一个包括生物礁岩、非造礁生物骨骼碳酸盐岩、微生物岩和其他微生物成因岩石的统一的生物岩分类系统，包括4个层级24种基本岩石类型。新增的基本岩石类型包括生物泥晶岩、微礁岩、微屑岩、包壳石、微骨架岩、微绑结岩、丝状岩、微泥晶岩等。作者还对部分岩石例如骨架岩等的定义进行了补充修正与完善，讨论了生物岩研究中存在的4个问题。     

南盘江坳陷二叠纪生物礁油气勘探前景

本文总结近40个礁体的特征后,提出南盘江坳陷内礁分为台缘礁和台隆礁两种,礁体中普遍发现沥青,多数富集在礁顶50m范围内,礁体邻近有较好的生油岩,礁顶有巨厚的三叠纪平尔关相泥质岩和碎屑岩覆盖,地腹台隆型构造存在,具有较好的生物礁气勘探前景。     

塔中Ⅰ号坡折带上奥陶统成礁背景分析

自塔中Ⅰ号坡折带上奥陶统良里塔格组发现生物礁滩作为重要储集层后,有关礁的形态和规模一直存在较大的争议。本研究解析该地区礁的古生物组合、古生态结构和沉积环境,以此为基础系统论证生物礁的沉积序列。礁的建造方式可归属于珊瑚骨架礁丘、层孔虫—海绵骨架礁丘、海绵—层孔虫骨架礁丘以及管孔藻—层孔虫骨架礁丘几种生态类型,这些骨架礁丘无论从造礁生物多样性、生态组合特征以及造礁规模,皆不同于前时代的前寒武纪叠层石礁、寒武纪古杯礁、早奥陶世的灰泥丘和托盘海绵礁,而呈现出单个礁体厚度大、发育旋回多之特点,多期礁体的垂向叠加、横向迁移造成礁体叠置连片, 形成了呈条带状展布的大型生物礁群。     

广西二叠纪生物礁的特征和分布规律

广西二叠纪生物礁（丘）非常发育，自栖霞期至长兴朝的均有分布，以茅口期最繁盛，生物礁主要发育于具陡斜坡的孤立浅水台地边缘，包括堤礁，马蹄形礁，环礁，链状礁和块状礁，造礁生物以钙质海绵为主，另有水螅，管壳石、苔藓虫及红藻等。包覆粘结生物以古三石孔藻、层纹状蓝绿藻为主，附礁生物为底栖生物和藻类，礁岩类型以复合型为主，包括包覆骨架岩，粘结骨架岩，包覆障积粘结岩，包覆粘结岩等。生物丘则主要产在碳酸盐缓坡，孤     

Late Quaternary barrier and fringing reef development of Bora Bora (Society Islands,south Pacific): First subsurface data from the Darwin‐type barrier‐reef system

The universally known subsidence theory of Darwin, based on Bora Bora as a model, was developed without information from the subsurface. To evaluate the influence of environmental factors on reef development, two traverses with three cores, each on the barrier and the fringing reefs of Bora Bora, were drilled and 34 uranium‐series dates obtained and subsequently analysed. Sea‐level rise and, to a lesser degree, subsidence were crucial for Holocene reef development in that they have created accommodation space and controlled reef architecture. Antecedent topography played a role as well, because the Holocene barrier reef is located on a Pleistocene barrier reef forming a topographic high. The pedestal of the fringing reef was Pleistocene soil and basalt. Barrier and fringing reefs developed contemporaneously during the Holocene. The occurrence of five coralgal assemblages indicates an upcore increase in wave energy. Age–depth plots suggest that barrier and fringing reefs have prograded during the Holocene. The Holocene fringing reef is up to 20 m thick and comprises coralgal and microbial reef sections and abundant unconsolidated sediment. Fringing reef growth started 8780 ± 50 yr bp ; accretion rates average 5·65 m kyr^?1. The barrier reef consists of >30 m thick Holocene coralgal and microbial successions. Holocene barrier‐reef growth began 10 030 ± 50 yr bp and accretion rates average 6·15 m kyr^?1. The underlying Pleistocene reef formed 116 900 ± 1100 yr bp , i.e. during marine isotope stage 5e. Based on Pleistocene age, depth and coralgal palaeobathymetry, the subsidence rate of Bora Bora was estimated to be 0·05 to 0·14 m kyr^?1. In addition to subsidence, reef development on shorter timescales like in the late Pleistocene and Holocene has been driven by glacioeustatic sea‐level changes causing alternations of periods of flooding and subaerial exposure. Comparisons with other oceanic barrier‐reef systems in Tahiti and Mayotte exhibit more differences than similarities.     

Holocene and Pleistocene fringing reef growth and the role of accommodation space and exposure to waves and currents (Bora Bora,Society Islands,French Polynesia)

Holocene fringing reef development around Bora Bora is controlled by variations in accommodation space (as a function of sea‐level and antecedent topography) and exposure to waves and currents. Subsidence ranged from 0 to 0·11 m kyr^?1, and did not create significant accommodation space. A windward fringing reef started to grow 8·7 kyr bp , retrograded towards the coast over a Pleistocene fringing reef until ca 6·0 kyr bp , and then prograded towards the lagoon after sea‐level had reached its present level. The retrograding portion of the reef is dominated by corals, calcareous algae and microbialite frameworks; the prograding portion is largely detrital. The reef is up to 13·5 m thick and accreted vertically with an average rate of 3·12 m kyr^?1. Lateral growth amounts to 13·3 m kyr^?1. Reef corals are dominated by an inner Pocillopora assemblage and an outer Acropora assemblage. Both assemblages comprise thick crusts of coralline algae. Palaeobathymetry suggests deposition in 0 to 10 m depth. An underlying Pleistocene fringing reef formed during the sea‐level highstand of Marine Isotope Stage 5e, and is also characterized by the occurrence of corals, coralline algal crusts and microbialites. A previously investigated, leeward fringing reef started to form contemporaneously (8·78 kyr bp ), but is thicker (up to 20 m) and solely prograded throughout the Holocene. A shallow Pocillopora assemblage and a deeper water Montipora assemblage were identified, but detrital facies dominate. At the Holocene reef base, only basalt was recovered. The Holocene windward–leeward differences are a consequence of less accommodation space on the eastern island side that eventually led to a more complex reef architecture. As a result of higher rates of exposure and flushing, the reef framework on the windward island side is more abundant and experienced stronger cementation. In the Pleistocene, the environmental conditions on the leeward island side were presumably unfavourable for fringing reef growth.     

Salt Marsh and Fringing Oyster Reef Transgression in a Shallow Temperate Estuary: Implications for Restoration,Conservation and Blue Carbon

The importance of intertidal estuarine habitats, like salt marsh and oyster reef, has been well established, as has their ubiquitous loss along our coasts with resultant forfeiture of the ecosystem services they provide. Furthering our understanding of how these habitats are evolving in the face of anthropogenic and climate driven changes will help improve management strategies. Previous work has shown that the growth and productivity of both oyster reefs and salt marshes are strongly linked to elevation in the intertidal zone (duration of aerial exposure). We build on that research by examining the growth of marsh-fringing oyster reefs at yearly to decadal time scales and examine movement of the boundary between oyster reef and salt marsh at decadal to centennial time scales. We show that the growth of marsh-fringing reefs is strongly associated to the duration of aerial exposure, with little growth occurring below mean low water and above mean sea level. Marsh-shoreline movement, in the presence or absence of fringing oyster reefs, was reconstructed using transects of sediment cores. Carbonaceous marsh sediments sampled below the modern fringing oyster reefs indicate that marsh shorelines within Back Sound, North Carolina are predominantly in a state of transgression (landward retreat), and modern oyster-reef locations were previously occupied by salt marsh within the past two centuries. Cores fronting transgressive marsh shorelines absent fringing reefs sampled thinner and less extensive carbonaceous marsh sediment than at sites with fringing reefs. This indicates that fringing reefs are preserving carbonaceous marsh sediment from total erosion as they transgress and colonize the exposed marsh shoreline making marsh sediments more resistant to erosion. The amount of marsh sediment preservation underneath the reef scales with the reef’s relief, as reefs with the greatest relief were level with the marsh platform, preserving a maximum amount of carbonaceous sediments during transgression by buffering the marsh from erosional processes. Thus, fringing oyster reefs not only have the capacity to shelter shorelines but, if located at the ideal tidal elevation, they also keep up with accelerating sea-level rise and cap carbonaceous sediments, protecting them from erosion, as reefs develop along the marsh.     

波浪在珊瑚岸礁礁坪上传播变形的数值研究

波浪的传播变形对珊瑚岛礁附近的营养物质输送以及近岸珊瑚沙运动都起着关键的作用,同时也是礁盘顶部建筑物在设计和施工过程中需要重点考虑的因素,因此,对波浪在礁坪上的传播变形进行研究具有重要意义。利用FUNWAVE 2.0数值模型模拟了不规则波浪在不同形状岸礁上的传播变形过程,讨论了礁前斜坡坡度以及珊瑚底面粗糙程度对波浪在礁坪上传播变形的影响。结果显示,随着礁坡斜率增大,不对称度参数绝对值的增长趋势逐渐变缓,波浪在光滑礁坪上的不对称度绝对值要略大于粗糙底面上的值,而不同地形下计算得到的波浪偏度参数则基本相同。说明礁坡坡度对波浪的不对称度特征具有显著影响,礁坪粗糙度的影响则相对较小,而上述因素对波浪偏度的影响则完全可以忽略。给出了考虑这两个影响因素的礁坪区域内波浪偏度和不对称度经验公式。     

不规则波在岸礁地形增水变化规律试验

波浪增水抬升了岸礁礁坪的平均水位,对岸礁后方陆域安全有重要影响。通过水槽试验,研究了不规则波况下岸礁礁坪的增水。试验组次为3种礁坪水深、4种有效波高和4种谱峰周期的组合。试验结果表明:①岸礁地形上的波浪要素需至少统计200个波才能达到稳定;②不规则波列在岸礁上破碎过程比规则波列复杂,同一波列中波高较大的波以卷破形式在礁前斜坡上破碎,波高较小的波以崩破形式在礁坪上破碎或者不破碎;③礁坪上最大增水值随入射波周期的增大而增大、随礁坪水深的增大而减小,并与入射波波高呈正比。结合试验数据,发现基于规则波试验得出的Gourlay礁坪增水公式,在使用有效波高和谱峰周期作为代表波要素时,公式能良好地预测不规则波在岸礁礁坪上的最大增水值。     

Contradicting Barrier Reef relationships for Darwin’s Evolution of reef types

The Darwinian progressive subsidence model for the evolution of fringing reefs, barrier reefs and atolls has been generally accepted following the indisputable proof of subsidence provided by drilling results in the Pacific. Nonetheless, there are data that do not fit the expectations of the model, such as the similar lagoon depths of barrier reefs and atolls as opposed to the subsidence theory’s implicit prediction that atolls should have significantly greater depths. In contrast, a great deal of evidence supports the influence of meteoric solution on barrier reef morphology. For example, the maximum lagoon depth of 56 modern barrier reefs is statistically correlated with the lagoon catchment area for modern annual rainfall. These modern rainfall patterns would seem to be a reasonable proxy for relative geographic differences in glacial lowstand rainfall, even though the absolute amounts of such rainfall are unknown. The correlation therefore suggests the importance of Pleistocene subaerial solution in contributing to barrier reef morphology. Further support for antecedent influence occurs in the form of barrier reef passes in which the depth of the reef pass is correlated with onshore drainage volumes. On a larger scale, the Cook Island of Mangaia provides evidence that solution can produce barrier reef morphology independent of reef development. In contrast, there are no examples of the subsidence-predicted lagoon transition of fringing reefs to barrier reefs to atolls. Moreover, the common occurrence of fringing reefs within barrier reefs negates subsidence as a causal factor in their ‘presumed progressive evolutionary development. Consequently, the evidence to date suggests that a solution morphology template has been accentuated by reef construction to produce the diagnostic barrier reef morphology we see today. The importance of subsidence would seem to be in accounting for the overall thickness of the resulting carbonate caps of oceanic examples and in contributing to lagoon depth variation among the larger continental entities.

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鄂尔多斯盆地奥陶系丘形反射的解释及其与礁的关系

鄂尔多斯盆地Ｔ９－Ｔ１０地震反射波组之间的奥陶系碳酸盐岩中存在着许多丘形反射,其中一部分属于以藻类生物为主的藻丘类型,一部分为东部盐凹中的盐丘,一部分为奥陶系顶古风化壳残丘,其它丘形反射为绕射波,回转波,或者为地表静校不当引起的假象,奥陶系的礁丘一般规模很小,岩性以粘结为主,其孔隙发育好坏同风化残丘一样,主要取决于次生溶蚀作用,但礁丘生长过程中由于受海面波动影响,曾发生过多次暴露,形成多期溶孔,礁     

Large earthquakes kill coral reefs at the north-west Gulf of Aqaba

Down‐faulting at the north‐west margins of the Gulf of Aqaba is inferred to have triggered a catastrophic sedimentary event at 2.3 ka that killed the Elat fringing coral reef. Whereas segments of the Holocene reef were perfectly fossilized and preserved beneath a veneer of siliciclastic sediments, other segments were abraded, settled by nomads, and later re‐submerged under 4 m of water. Repeated damage triggered by down‐throwing earthquakes degenerate the fringing reefs of the north‐west end of the gulf. Conversely, on the north‐eastern and southern parts of the gulf, where earthquakes uplift the margins, modern reefs are thriving, attached to uplifted fossil reef terraces. Therefore, coastal subsidence moderates the development of fringing coral reefs during the late Holocene sea‐level stand still.     

Mesoproterozoic deep-water reefs from Borden Peninsula, Arctic Canada

A superbly exposed stromatolite reef complex occurs in the Victor Bay Formation near Strathcona River on northern Baffin Island. Individual reefs are up to 130 m thick and nearly 1 km in length, and their development was clearly related to their position in the facies spectrum and to sea-level dynamics. In the first sea-level cycle, metre-scale reefs grew amongst mid-ramp calcarenites and outer-ramp shales during slow sea-level rise; a 25-m-thick oblate reef tract, separating mid-ramp and outer-ramp facies, formed during the highstand. The greatest period of reef growth was during the second sea-level cycle. Pinnacle reefs nucleated on the karsted upper surface of the oblate reef tract and aggraded rapidly in response to rising sea-level, producing structures with more than 75 m of depositional relief. A gradual symmetrical succession of stromatolite growth forms, from stratiform to cylindrical columns to conical columns and then back through cylindrical columns to stratiform, is mirrored by evidence in offreef deposits for deepening to a maximum flooding surface and then shallowing. The tops of these high-standing reefs were karsted during the following regression, while dolomite ‘cryptodomes’ grew as sheets on their submerged flanks and as progradational tongues extending basinward of the reefs. Continued sea-level fall resulted in subaerial exposure of the entire reef complex and the extensive formation of surface and subsurface karst. These Proterozoic slope buildups are similar to Phanerozoic deep-water reefs in size, shape, prevalence of synsedimentary lithification, presence of Neptunian dykes and in their well-developed vertical zonation of reefbuilders. However, they differ in being constructed exclusively by stromatolites rather than being mud mounds with small skeletal elements, and in lacking halos of perireefal sand- and gravel-sized calcareous debris. Their responses to changes in sea-level were strikingly similar to those shown by their younger counterparts, and suggest that sequence-stratigraphic concepts derived from studies of Phanerozoic reefs can also be applied to the Proterozoic.