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1.
在地质历史时期的碳循环中,生物的作用很大.生物产氧光合作用消耗CO2而产生有机质与O2;有机质及生物成因碳酸盐岩埋藏又进一步固定CO2并减少O2消耗,所以生物产氧光合事件与冰期、成（增）氧期应存在因果关系.论述了5次事件,分别是:与产氧光合蓝细菌有关的古元古代初期大氧化事件（Early Proterozoic great oxygenation event,GOE）、与真核生物辐射事件有关的新元古代大成氧事件（Neoproterozoic oxidation event,NOE）、与早期陆生植物繁盛事件有关的晚奥陶世增氧和冰期事件、与维管植物繁盛事件有关的石炭纪-二叠纪增氧和冰期事件及与被子植物和浮游微植物繁盛有关的第四纪冰期事件.结果表明,5次成氧事件和冰期与生物事件有因果关系,主要表现为,都有冰期和成氧事件共存或相继出现的证据,反映大气CO2降低和O2增加同时或相继发生,而这只能由生物的光合作用及其产物的埋藏造成.这说明生物不仅仅是适应于环境,它也对环境产生重大影响,生物与环境的这种相互作用在漫长的地质历史中表现为协同演化.但是早期生物事件并不立刻产生成氧或冰期等环境效应,这种效应开始是微量的,逐渐积累,达到阈值后才发生质变,所以在时间上是滞后的.随着生物多样性和丰度的增加,这种效应越来越大,速率越来越快,滞后性逐渐减弱,耦合性日渐明显.生物与地球环境之间的相互作用构成了生物与地球系统的自我调节,使地球与其他星球不同,其表层始终保持在生命宜居的环境范围内.今天人类更要理智地、科学地善待地球,避免对地球造成重大的负面影响. 相似文献
2.
The study of dust deposition records in geological history is of great significance to the study of paleoclimate evolution during deep periods. Because dust can directly influence the biochemical processes and climate evolution of the Earth. However, the absence of quantitative data on dust limits the systematic and comprehensive study of paleoclimate evolution during deep periods. Prior to the Quaternary period, most quantitative studies on atmospheric dust have focused on the Permian era. However, in the entire Mesozoic era, there are still no quantitative data available on atmospheric dust deposition rates. We utilized the average concentration of inorganic matter in coal from the Jurassic and Cretaceous periods to depict the dust concentration and corresponding dust deposition rate in the atmospheric system during these periods. We also conducted a correlation analysis using the distribution of arid source areas. The results show that the values of ash concentration and dust deposition rates are higher near the arid provenance and lower far away from it. Furthermore, in this study, we have compared the latitudinal variation gradient of dust deposition rates under the icehouse and greenhouse climates by using the end of the Permian and Quaternary as representatives of icehouse climate and the Jurassic and Cretaceous periods as representatives of the greenhouse climate. Our findings indicate that there is a higher ash concentration, dust deposition rate, and dust deposition rate variation gradient in the air under the icehouse climate, while there is a lower ash concentration, dust deposition rate, and dust deposition rate gradient in the air under the greenhouse climate. We have also discussed the dust sources during the Mesozoic period, as well as the differences in ash data under greenhouse and icehouse conditions. This provides a strong basis for studying the atmospheric environment after the modern climate entered the ice age. 相似文献
3.
Response of reef coral communities to sea-level rise: a Holocene model from Mauritius (Western Indian Ocean) 总被引：1，自引：0，他引：1
The fringing reef at Pointe-au-Sable (Mauritius, Indian Ocean) was used to examine the effects of Holocene sea-level rise on coral growth. This reef is about 1000 m wide and comprises a forereef slope (30 m maximum depth), a narrow reef crest and a very shallow backreef (1·5 m maximum depth). Four major coral communities were recognized, which developed within relatively narrow depth ranges: a Pachyseris/Oulophyllia community (deeper than 20 m), an Acropora‘tabulate’Faviid community (20–6 m); a robust branching Acropora community (less than 6 m) and a Pavona community (less than 10m). Three high-recovery cores show the Holocene reef sequence is a maximum of 19·3 m thick and comprises four coral biofacies which are similar to counterparts identified in modern communities: robust branching, tabular-branching, robust branching-domal and foliaceous coral facies. A minimum sea-level curve for the past 7500 years was constructed. Using distribution patterns of coral biofacies and radiocarbon dates from corals, reconstruction of reef growth history indicates that both offshore and onshore reef zones were developing coevally, aggrading at rates of 4·3 mm year?1 from 6900 years B.P. The reef caught up with sea-level only after sea-level stabilized. Changes in coral community and reef growth rates were driven principally by increasing water agitation due to the decrease in accommodation space. Based on the composition of the successive coral assemblages, the reef appears to have grown through successive equilibrium stages. 相似文献
4.
Deborah Painter 《Geology Today》2017,33(4):138-141
In south‐central Pennsylvania, USA, is the world's only Upper Silurian/lower Devonian period shallow water marine reef, located deep within a cave and operated for the tourist trade. Other unusual features in the cave include black basaltic rock, the presence of nearly perfect clear calcite crystals and varied cave decorations. The reef is primarily composed of stromatoporoids with brachiopods and crinoids and is part of the Upper Silurian Jersey Shore Member of the Keyser Formation siliciclastics and carbonates. Just outside the cave itself is a transition to the Devonian New Creek and Corriganville formations, also siliciclastics and carbonates. In these formations are the only actual fossil corals in the vicinity of the cave discovered by Boy Scouts in 1928 by climbing through a natural entrance. ‘Wonderland Coral Caverns’ was opened to the public in the 1930s and closed in the 1980s until a safer entrance could be created. The cave is the result of the Alleghanian Orogeny in which Silurian and Devonian sedimentary strata were buried without metamorphism beneath the encroaching northwest African continental mass as the proto‐Atlantic Ocean and the Rheic Ocean closed. The mass eroded completely and the resulting sediments were transported to the west of modern day Pennsylvania, leaving a karst topography and a well preserved fossil reef. 相似文献
5.
新生代至前寒武纪海相和陆相沉积记录显示,405 ka长偏心率周期贯穿整个地质历史,从陆地季风降水到大洋碳循环都有表现,是地球表层系统中水循环和碳循环的基本节拍,不仅可用作基本的地质计时单位,还是低纬过程的重要特征之一.现有的地质记录表明405 ka长偏心率周期存在被隐匿或被破坏的现象,火山岩浆活动释放CO2、生物圈重大变革和冰盖增大事件等都可以造成405 ka长偏心率周期的隐匿,这为揭示地球表层系统重大变化提供了一个新的切入点.通过研究405 ka长偏心率周期的演变特征和破坏机制,可望穿越暖室和冰室期,建立起完整的气候演变理论.最后对我国开展天文旋回研究力争走到世界前列提出了建议和展望. 相似文献
6.
特提斯地球动力学 总被引：19，自引：9，他引：10
特提斯是地球显生宙期间位于北方劳亚大陆和南方冈瓦纳大陆之间的巨型海洋,它在新生代期间的闭合形成现今东西向展布的欧洲阿尔卑斯山、土耳其-伊朗高原、喜马拉雅山和青藏高原。根据演化历史,特提斯可划分为原特提斯、古特提斯和新特提斯三个阶段,分别代表早古生代、晚古生代和中生代期间的大洋。大约在500Ma左右,冈瓦纳大陆北缘发生张裂,裂解的块体向北漂移,并使其与塔里木-华北之间的原特提斯洋在420～440Ma左右关闭,产生原特提斯造山作用,与北美-西欧地区Avalonia地体与劳伦大陆之间的阿巴拉契亚-加里东造山作用基本相当。原特提斯造山带之南、早古生代即已存在的龙木错-双湖-昌宁-孟连古特提斯洋在380Ma向北俯冲,使早期闭合的康西瓦-阿尼玛卿洋重新张开,并由于弧后扩张形成金沙江-哀牢山洋。330～360Ma左右,特提斯西部大洋由于南侧非洲板块和北侧欧洲板块的碰撞而关闭,形成欧洲华力西造山带。而特提斯东段的上述三条古特提斯洋在250Ma左右基本同时关闭,华北、华南、印支等块体聚合形成华夏大陆。该大陆与冈瓦纳大陆、劳亚大陆和华力西造山带一起围限形成封闭的古特提斯残留洋,并一直到晚三叠世-早侏罗世海水才全部退出。此后,南侧冈瓦纳大陆在三叠纪晚期重新裂解形成新特提斯洋,该洋盆在新生代初期由于印度和亚洲的碰撞而关闭。原、古、新特提斯三次造山作用基本代表了中国大陆显生宙期间的地质演化历史,并在此过程中形成了特色的特提斯域金属成矿作用。广布的被动陆缘和赤道附近的古地理位置,以及后期的造山作用同时也成就了特提斯域内巨量油气资源的形成;塑就的地貌与海陆分布格局,也对当时的古气候与古环境产生了重要影响。特别是,与原、古、新特提斯洋消亡相关的三次弧岩浆活动与显生宙地球历史上三次温室地球向冰室地球的转变,在时间上高度吻合。上述演化历史同时还表明,特提斯地质演化以南侧冈瓦纳大陆不断裂解、块体向北漂移并与劳亚大陆持续聚合为特征,其动力机制主要来自俯冲板片的拖拽力,而地幔柱是否对大陆的裂解与漂移有所贡献,则有待进一步评价。 相似文献
7.
Two surface‐sediment sampling campaigns were carried out in November and December 2003, before and after a strong swell event, in the back‐reef area of a microtidal fringing reef on the western coast of La Reunion, Indian Ocean. The spatial distributions of the mean grain size, sorting and skewness parameters are determined, and grain‐size trend analysis is performed to estimate the main sediment transport pathways in the reef. The results of this analysis are compared with hydrodynamic records obtained in the same reef area during fair weather conditions and during swell events. Sediment dynamics inferred from the hydrodynamic records show that significant sediment erosion and transport occur only during swell events and under strongly agitated sea states. Under normal wave conditions, there is a potential for onshore sediment transport from the reef‐flat to the back‐reef, but this transport is episodic and occurs principally during high‐tide stages. Sediment transport trends revealed by the grain‐size trend analysis method show onshore and alongshore low‐energy transport processes that are in agreement with the hydrodynamic records. The grain‐size trend analysis method also provides evidence of an offshore high‐energy transport trend that could be interpreted as a real physical process associated with return flow from the shore to the reef. The impact of swell on the reef sediment dynamics is clearly demonstrated by onshore and alongshore transport. Considering different combinations of the vector transport trends computed through the grain‐size trend analysis approach, more realistic and pertinent results can be obtained by applying an exclusive OR operation (XOR case) on the vectors. The main results presented here highlight a trend towards the accumulation of carbonate sands in the back‐reef area of the fringing reef. These sediments can only be resuspended during extreme events such as storms or tropical cyclones. 相似文献
8.
楚科奇海R12a沉积柱状样500年以来生物标记物记录 总被引：2，自引：0，他引：2
通过多参数生物标志物法对取自中国第二次北极考察的R12a岩心顶部40 cm样品进行了浮游植物和种群结构变化的研究,获得了500 a以来浮游植物初级生产力和种群结构变化信息。结果表明:R12a岩心在过去的500多年来,所记录的海洋初级生产力呈上升趋势,单一藻类的生产力总体上也呈现上升趋势。浮游植物种群结构主要表现为颗石藻相对含量下降,硅藻相对含量上升,甲藻没有明显的波动,这可能与北太平洋水输入决定的楚科奇海营养盐结构及夏季海冰覆盖变化有关。 相似文献
9.
青藏高原龙木错-双湖板块缝合带与羌塘古特提斯洋演化记录 总被引：27，自引：17，他引：27
龙木错-双湖缝合带、西金乌兰-金沙江缝合带和昆仑-秦岭缝合带是青藏高原上3条主要的晚三叠世板块缝合带,目前的研究资料表明后2条缝合带不具备冈瓦纳北界的基本要素。简要介绍了龙木错-双湖缝合带中有关古特提斯洋存在的基本事实,即早古生代洋壳残片、二叠纪蛇绿岩、泥盆纪—二叠纪放射虫硅质岩、各类不同性质的增生岩片、2种类型的构造混杂岩带和蛇绿混杂岩盖层体系的时代与性质等,已有的资料初步确定羌塘古特提斯洋盆演化的时限为晚泥盆世到晚三叠世。认为龙木错-双湖缝合带是青藏高原上古特提斯洋消亡的主要场所,是恢复和反演青藏高原早期形成演化的最重要的窗口,也是地学界几十年关注的冈瓦纳大陆的北界。 相似文献
10.
11.
Coral reefs are influenced by global and local factors, and living corals are currently faced with a potential loss of species diversity. Knowledge of the relationship between species diversity and reef growth during the Holocene is important in terms of accurately reconstructing natural conditions prior to recent disturbances (e.g., human impact, pollution, and over-harvesting) and in predicting future scenarios (e.g., abrupt sea-level rise, coastal change, and economic services). This study seeks to characterize the Holocene and present-day reef at Ishigaki Island in the Ryukyu Islands, focusing on spatial and temporal variations in the relationship between species diversity and reef growth. The analysis is based on a drilling core obtained for the Holocene reefs and quantitative species-diversity data (Shannon and Weaver's diversity index, H′) obtained for the present-day reef. H′ was calculated for four coral communities surveyed at the Ibaruma and Fukido reefs. The Holocene sequence was dominated by the corymbose coral community (e.g., Acropora digitifera, A. hyacinthus, Goniastrea retiformis, and Platygyra ryukyuensis), yielding an H′ value of 1.6. The encrusting coral community (e.g., Echinopora lamellose and Pachyseris rugosa) showed the highest diversity at the reef (H′ = 2.2); however, this community was not one of the main reef builders during the Holocene. The massive coral community (e.g., Porites lutea and Favites chinensis) showed the lowest diversity (H′ = 0.6). It also made a minor contribution to reef building; this community appeared in a shallow lagoon once sea level had stabilized. The arborescent coral community (e.g., A. formosa and A. nobilis) was one of the main reef builders, although yielding an H′ value of much less than 1.0. Species diversity is not a prerequisite in terms of Holocene reef growth. Thus, a few species (e.g., A. digitifera, A. hyacinthus, A. formosa, A. nobilis, G. retiformis, and P. ryukyuensis) from two main reef-building communities are important for reef growth. These corals that act as reefs are characterized by high growth rates, having an upward reef growth rate of 2–12 m kyr? 1 in the Indo-Pacific during the Holocene. 相似文献
12.
The mechanical breakdown of rock by physical weathering exerts a significant control on chemical weathering rates because it produces surface area. During periods of icehouse conditions on Earth, the grinding of rock by glacial processes should lead to faster chemical weathering of the continents, perhaps particularly during periods of pronounced climatic variability, like the Quaternary. Evidence is reviewed here for both high and cyclical chemical weathering rates during the Quaternary, and the implications for both marine geochemical budgets and climate-chemical weathering feedbacks are discussed. 相似文献
13.
The transition from the Last Glacial Maximum to the Holocene was an internal of climate variability that was characterised by large spatial and temporal variations. Here we show that deglaciation warming in the northern Indian Ocean was initiated ca. 19 ka, which is contemporary with deglaciation warming in the Antarctica and Southern Ocean. A gradual warming occurred during the glacial/Holocene transition in the northern Indian Ocean, unlike the two‐step warming seen in Greenland and the North Atlantic. Synchronous deglacial warming ca. 19 ka in Antarctica and the northern Indian Ocean suggests a strong connection in the propagation of climate signals between Antarctica and the Indian Ocean, probably through the Indonesian Throughflow and/or Subantarctic Mode Water. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
T. V. Litvinova 《Lithology and Mineral Resources》2014,49(5):416-426
The electron microscopic study of stromatolites in the northern Anabar region revealed that the cyanobacterial colony represents a community of diverse microorganisms making up a very thin biofilm on the mineral layer surface. The morphology of fossilized bioparticles and their mutual arrangement in organogenic layers alternating with mineral layers play a crucial role in the formation of specific (banded, varved, clotted, and others) rock microstructures, which served as a basis for the classification of stromatolites. 相似文献
15.
中扬子台地下奥陶统红花园组造礁生物群落主要有五种 :蓝绿藻群落 (S群落 )、Calathium 蓝绿藻群落 (C S群落 )、Batostoma-Calathium群落 (B C群落 )、Archaeoscyphia-Calathium群落 (A C群落 )和Batostoma-Calathium 蓝绿藻群落 (B C S群落 )。群落的演化模式有两种 :①A C群落 /B C群落→C S群落 /B C S群落→S群落;②S群落→C S群落 /B C S群落→A C群落 /B C群落,它们分别对应于上下两期生物礁。群落最大的生态差别可能是其最适合的水深,说明其演化的主要动力可能是相对海平面的变化,根据各群落适应的水深特征,可推测红花园建礁期为一个海平面下降到上升的一个过程,相对海平面变化的最大幅度约为 15m。生物礁内生物群落的演化是海平面变化的灵敏示踪剂,可识别 5m左右的相对海平面的变化. 相似文献
16.
Edward J. Phlips Susan Badylak Jane Hart Daniel Haunert Jean Lockwood Kathyrn O’Donnell Detong Sun Paula Viveros Mete Yilmaz 《Estuaries and Coasts》2012,35(1):335-352
The St. Lucie Estuary, located on the southeast coast of Florida, provides an example of a subtropical ecosystem where seasonal
changes in temperature are modest, but summer storms alter rainfall regimes and external inputs to the estuary from the watershed
and Atlantic Ocean. The focus of this study was the response of the phytoplankton community to spatial and temporal shifts
in salinity, nutrient concentration, watershed discharges, and water residence times, within the context of temporal patterns
in rainfall. From a temporal perspective, both drought and flood conditions negatively impacted phytoplankton biomass potential.
Prolonged drought periods were associated with reduced nutrient loads and phytoplankton inputs from the watershed and increased
influence of water exchange with the Atlantic Ocean, all of which restrict biomass potential. Conversely, under flood conditions,
nutrient loads were elevated, but high freshwater flushing rates in the estuary diminished water residence times and increase
salinity variation, thereby restricting the buildup of phytoplankton biomass. An exception to the latter pattern was a large
incursion of a cyanobacteria bloom from Lake Okeechobee via the St. Lucie Canal observed in the summer of 2005. From a spatial
perspective, regional differences in water residence times, sources of watershed inputs, and the proximity to the Atlantic
Ocean influenced the composition and biomass of the phytoplankton community. Long water residence times in the North Fork
region of the St. Lucie Estuary provided an environment conducive to the development of blooms of autochthonous origin. Conversely,
shorter residence times in the mid-estuary limit autochthonous increases in biomass, but allochthonous sources of biomass
can result in bloom concentrations of phytoplankton. 相似文献
17.
应用特征光合色素研究东海和南海北部浮游植物的群落结构 总被引：23，自引：0，他引：23
应用高效液相色谱并结合二极管阵列检测器分析技术，研究了东海与南海北部典型断面浮游植物的光合色素组成，进而由CHEMTAX软件估算浮游植物群落结构。结果表明：东海断面浮游植物叶绿素a生物量大于南海北部断面。受海水层化结构影响，东海PN断面浮游植物群落结构形成上层和下层两种类型，上层以蓝藻为主要优势类群；下层以硅藻为主要优势类群。南海北部S断面浮游植物群落形成近岸与离岸两种类型，近岸以硅藻、隐藻、绿藻为主要优势类群；离岸以定鞭金藻、蓝藻、原绿球藻为主要优势类群。初步分析了研究海区浮游植物群落结构与环境因子的关系。 相似文献
18.
2015年3月"海马"号遥控无人潜水器(ROV)在南海北部陆坡西部海域首次发现活动冷泉,并命名为"海马"冷泉,此后中国地质调查局广州海洋地质调查局先后组织了3个航次,对"海马"冷泉开展进一步勘查和研究。本次研究在综合分析4个航次调查数据的基础上,初步阐述"海马"冷泉的分布范围、地形地貌、生物群落、自生碳酸盐岩和流体活动等特征。总体而言,"海马"冷泉区地势平缓,气体渗漏现象非常发育,是以CH4为主要气体渗漏形成的活动冷泉区,且气体渗漏活动具有时空迁移性。气体碳同位素组成表明,海马冷泉区的CH4为混合成因气,且以微生物成因为主;"海马"冷泉区发育有多种类型的化能自养冷泉生物群落,冷泉区种类丰富,目前已报道了多个冷泉生物新种。这些发现为研究南海北部陆坡西部海域天然气水合物分解及其环境效应、冷泉生物生命起源与演化和南海与印度洋及太平洋物种迁移贯通等科学问题提供重要依据。 相似文献
19.
在《印度洋底大地构造图》的基础上,分析了印度洋盆构造格局和洋盆演化重大事件序列,并从印度洋盆初始裂解机制、扩张中心跃迁与热点作用、洋中脊扩展作用等方面讨论了印度洋盆的张开过程,提出以下几点认识:(1)现今印度洋洋中脊可分为两个系统:东南印度洋中脊-中印度洋中脊-卡斯伯格洋脊系统(东支)和西南印度洋中脊系统(西支),前者是太平洋洋中脊扩展作用的产物,后者是太平洋-东南印度洋中脊与大西洋中脊之间构造调节的产物;(2)印度洋盆最初裂解受地幔柱垂向挤压-水平伸展作用控制,沿前寒武造山带等地壳薄弱带发育;(3)印度洋盆经历两次扩张中心的跃迁,其趋向性跃迁方向与热点相对板块的运动方向具有一致性,显示两者存在内在联系。(4)大西洋和太平洋洋中脊在印度洋交汇,于古近纪连通,末端伴随陆块持续发生碎裂化、裂解化,可称为鱼尾构造模式,表明印度洋盆衔接和调节了三大洋盆的发育和演化过程,具有全球洋盆枢纽的关键意义。 相似文献
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地球圈层相互作用中的深海过程和深海记录（I）：研究进展与成果 总被引：1，自引：1，他引：0
由五大系统11个实验室组成的项目组,2000—2005年开展了以“地球圈层相互作用”为主题的深海基础研究。项目以“热带碳循环”作为核心问题,依靠国际大洋钻探和国内“大洋专项”两大支柱,对西太平洋暖池和南海等海区进行深海过程和深海记录的研究,已圆满完成计划任务。一方面在南海大洋钻探的基础上,围绕热带海洋在地球系统中的作用向纵深发展,在“热带碳循环”研究中取得了原创性的成果;另一方面依托国内大洋专项和国内外合作航次,在深海研究和圈层相互作用上朝横向发展,取得了一系列国际性成果,在我国形成了与国际接轨的深海研究力量。对该项目的设计和进展做了简单而又全面的阐述,对于古环境研究中取得的突破性进展将另有续篇介绍。 相似文献