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柴达木盆地中新世叠层石成因与古环境研究 总被引：3，自引：1，他引：3
柴达木盆地西部干柴沟一带发育了大量湖相叠层石，主要存在于新近纪中新世地层中。柴西地区的叠层石形态各异，成因各具特点，而且部分叠层石与现代叠层石完全不同而是更类似于前寒武时期的对应物，根据国内外叠层石研究的最新成果和成因分类标准，柴西地区主要发育了骨架、凝集和细粒叠层石。对应于不同的分类标准其成因也各不相同，细粒叠层石的形成主要是通过微生物自身的钙化作用和生物膜上过饱和碳酸盐等物质以及微生物的引发的沉淀作用；凝集型叠层石的形成主要与原核生物和真核藻类共同发挥粘附作用有关；骨架型叠层石的形成主要是真核藻类等的钙化与原地碳酸盐的沉淀综合作用的结果。柴达木盆地频繁变化的湖相水体条件和周围的构造运动是叠层石形态多样，成因各异的主要外部和环境因素。对各类叠层石的深入细致研究将对沉积学和环境学的研究提供宝贯的现代对应物。 相似文献
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四川秀山下寒武统清虚洞组的骨骼葛万藻藻鲕及岩石学意义 总被引：3，自引：1，他引：3
叠层石有正常叠层石和骨骼叠层石之分。与葛万藻有关的骨骼叠层石分为骨骼葛万藻叠层石、骨骼葛万藻核形石、骨骼葛万藻藻鲕和骨骼葛万藻凝块石等四类。骨骼葛万藻藻鲕是由葛万藻藻球经过重结晶作用而变成的。镜下观察,这种鲕由葛万藻及其捕获粘结的碎屑颗粒、葛万藻重结晶残余结构和重结晶方解石晶体三部分构成。骨骼葛万藻藻球是潮间和潮下低能环境中形成的,它为鲕的生物成因提供了有力的证据。 相似文献
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王承书 《沉积与特提斯地质》1991,11(1):62-68,61
一、陆相叠层石及纹层状钙结岩:评论纹层状碳酸盐是地表露头剖面及多种含钙结岩钙质土壤的显著特征。以前多注重于这些纹层岩与海相或湖相微生物叠层石和似核形石的区别;然而,最近的研究却表明,许多地表纹层状碳酸盐为生物成因形成的,但主要(不是全部)由微生物的活动所形成。本文评论了区分陆相碳酸盐纹层岩与非陆相叠层石和似核形石、生物成因与非生物成因陆相纹层岩的标志。 相似文献
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河北承德路通沟剖面芙蓉统凤山组中部发育厚层块状叠层石生物丘,构成一个淹没不整合型层序的强迫型海退体系域,指示这些叠层石形成于中高能浅海环境。该生物丘宏观上主要由柱状叠层石组成,叠层石内部纹层较粗糙,在构成叠层石的致密泥晶和微亮晶组构中,还见到球粒、底栖鲕粒及凝聚颗粒等多种生物成因颗粒类型,代表着复杂的微生物活动特征,以此而区别于前寒武纪的叠层石。更为重要的是,叠层石生物丘中的致密泥晶基质中发育一些“石松藻(Lithocodium)”状的钙化蓝细菌菌落残余物,以及一些丝状钙化蓝细菌化石,指示了形成叠层石的微生物席为蓝细菌所主导的微生物席。因此,凤山组叠层石生物丘内复杂而特殊的碳酸盐岩沉积组构为研究叠层石形成过程中复杂的微生物代谢活动所产生的钙化作用机制提供了一个宝贵的地质实例。 相似文献
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在柴达木盆地发育了各种类型的渐新世—中新世湖相叠层石，其中丘状叠层石具有重要的地质意义，丘状叠层石直接生长在砾岩上，并向上逐渐演化为藻礁，藻礁向上又重新转化为叠层石沉积。通过对内部纹层特征和沉积组分的研究并结合叠层石的同位素、地球化学以及古生物资料分析表明，微生物自身的钙化作用以及微生物引发的沉淀作用形成了这种具有典型内部纹层的丘状叠层石。较高的温度、炎热和干燥的气候条件、坚硬的基底以及较少的藻类干扰作用是叠层石生成的主要因素。总体上，叠层石形成于较为低能的环境中，与高能环境中所形成的藻礁完全不同，而且两者具有明显的相互竞争作用。因此，与气候和水体条件密切相关的后生生物的生长和真核藻类的发育是叠层石在显生宙迅速衰落的主要因素。 相似文献
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扬子克拉通北缘神农架地区中元古界神农架群叠层石十分发育。该群下部乱石沟组中叠层石类型丰富,根据形态可分为柱状、穹状、层状叠层石以及锥状、层柱状、包心菜状、墙状叠层石和叠层石丘等。研究区叠层石以中小型为主,少数为大型和巨型;多数无壁,部分具单层壁;对称性和继承性由好到一般,部分较差。研究表明,叠层石的形态和规模,与水动力条件、水体深度及陆源组分含量关系密切,其中层状叠层石主要发育于潮间带上部,柱状叠层石产于潮间带下部和浅潮下带,穹状叠层石出现在潮间带和潮下带,锥状叠层石多见于潮间带下部和潮下带,层柱状、锥柱状叠层石则集中于潮间带,叠层石丘位于潮间带和潮下带。依据各类型叠层石宏观和微观特征、垂向组合类型、沉积构造及沉积岩相相互关系,并结合碳、氧同位素测试结果,综合研究认为: 虽然叠层石的形成受生物和环境等多重因素影响,但生物因素主要影响叠层石的微观组构,水动力条件则控制叠层石的宏观形态类型,水体深度影响叠层石的规模;另外,生物繁盛、陆源物质供给少的环境更有利于叠层石发育。 相似文献
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叠层石衰减事件及臼齿构造作用幕：形成机制与研究进展 总被引：1，自引：0，他引：1
叠层石和臼齿构造碳酸岩的兴衰是沉积学界倍受关注的研究主题.地史中叠层石经证实发生了5次比较重要的衰减事件,分别在2 000 Ma、1 250 Ma、1 000 Ma、675 Ma、450 Ma.最近,根据燕山地区非叠层石碳酸盐岩序列,认为在1450 Ma又发生过叠层石衰减,所以存在6次叠层石衰减事件.现今叠层石的丰度已经非常稀少.究其原因主要在于:叠层石的形成与微生物钙化作用有关,而其钙化作用又受周围海水化学变化所影响.显生宙后生动物及海水饱和态共同影响了叠层石的形成.著名的"前寒武纪谜"表明,海水化学条件及微生物的进化则是叠层石发展的主要控制因素.臼齿构造(MT)仅出现在前寒武地层中,具有一定的时代限制,其形成及消失受海洋中CaCO3沉淀的影响,而且似乎主要发育在叠层石衰减事件之后,在空间上臼齿构造多产出于比叠层石更深的水体环境.所以古海洋化学的变化影响着地球表面生物演化及生物沉积的历史,上述研究进展对深入了解海洋化学在地质历史时期的长期变化具有重要意义,而且也有利于解开地质历史上的种种谜团. 相似文献
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扬子克拉通北缘中元古界神农架群乱石沟组叠层石类型及其沉积学意义 总被引：1，自引：1，他引：0
扬子克拉通北缘神农架地区中元古界神农架群叠层石十分发育。该群下部乱石沟组中叠层石类型丰富,根据形态可分为柱状、穹状、层状叠层石以及锥状、层柱状、包心菜状、墙状叠层石和叠层石丘等。研究区叠层石以中小型为主,少数为大型和巨型;多数无壁,部分具单层壁;对称性和继承性由好到一般,部分较差。研究表明,叠层石的形态和规模,与水动力条件、水体深度及陆源组分含量关系密切,其中层状叠层石主要发育于潮间带上部,柱状叠层石产于潮间带下部和浅潮下带,穹状叠层石出现在潮间带和潮下带,锥状叠层石多见于潮间带下部和潮下带,层柱状、锥柱状叠层石则集中于潮间带,叠层石丘位于潮间带和潮下带。依据各类型叠层石宏观和微观特征、垂向组合类型、沉积构造及沉积岩相相互关系,并结合碳、氧同位素测试结果,综合研究认为:虽然叠层石的形成受生物和环境等多重因素影响,但生物因素主要影响叠层石的微观组构,水动力条件则控制叠层石的宏观形态类型,水体深度影响叠层石的规模;另外,生物繁盛、陆源物质供给少的环境更有利于叠层石发育。 相似文献
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Ferriferous ooids and microoncoids occur in many sedimentary iron formations. These ferriferous-coated grains are found in fine-grained carbonate-rich groundmasses. Iron mineral-encrusted microbiota are observed in both the coated grains and the groundmass. The branching nature and other morphological features of the microorganisms suggest fungal origins for the oolitic iron ores particularly of the Lower Jurassic (Lorraine Minette). The similarity of the microbial structures in coated grains and their groundmasses suggests that both had developed within microbial mats growing under calm environmental conditions. The contribution of stromatolitic marine fungal mats to the fast extraction and immobilization of iron and thus to the genesis of iron ores is demonstrated. Observations on well-preserved freshwater-derived fungal stromatolites of the Tertiary and laboratory experiments with organotrophic fungal mats confirm the findings on the Jurassic and imply a general role of microorganisms in the formation of such deposits. 相似文献
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Robert J. Horodyski 《Precambrian Research》1975,2(3):215-254
The mode of formation and environmental setting of stromatolites from the lower Missoula Group (ca. 1.1·109 years old) in Glacier National Park, Montana, have been determined. The stromatolite-bearing interval in the lower Missoula Group was deposited in a shallow, intermittently exposed setting of very low relief, the stromatolites forming during periods of submergence. In situ carbonate precipitation was the dominant process involved in the formation of encrusting stromatolitic laminae. This precipitate was deposited within, and probably beneath, algal mats, most likely as a result of the photosynthetic removal of carbon dioxide by the mat-building microscopic algae. Calcite also was precipitated in several types of open-space structures occurring within these stromatolites. Other laminae were produced by the organic stabilization of detrital particles; by the solely physical accumulation of terrigenous material; and probably, by bacterially induced precipitation of iron sulfide which was later oxidized to form hematite layers.Three forms of filamentous microfossils, two of which appear to be oscillatoriacean cyanophytes and the third of which is probably either a cyanophyte or filamentous bacterium, have been detected in these structures. In addition, hematitic pillar-shaped microstructures, interpreted to have been produced by filamentous bacteria, are abundant locally.In gross morphology, the lower Missoula Group stromatolites are simple, unbranched, domal structures ranging from several millimeters to several decimeters in both height and diameter. Physical conditions played a major role in determining the macrostructure of these stromatolites. Of particular importance were the shape of the positive sediment-surface irregularities upon which the stromatolites initially formed, the rate of sedimentation between stromatolite colonies, and the deposition of layers of terrigenous material on stromatolite growth surfaces. The effect of biological factors on stromatolite structure is clearly seen in those portions of stromatolites relatively free of terrigenous material; biological activity was apparently greatest on positive irregularities of the growth surface, resulting in preferential enhancement of such irregularities and development of second- and higher-order hemispheroidal structures. 相似文献
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S. B. Misra 《Journal of Earth System Science》1984,93(4):447-464
Depositional environment of the Krol group varied temporally from subtidal in the Manora to intertidal in the Sleepy Hollow
times. The conditions that succeeded were peritidal in the Ayarpatta and supratidal in the Narainnagar times. These conditions
were the main controlling factors in the growth and development of the algal stromatolites. The Manora formation, due to subtidal
conditions, and the Sleepy Hollow formation, due to detrital influx, are almost devoid of stromatolites. The carbonates of
the Ayarpatta formation representing a peritidal complex possess columnar and oncolitic stromatolites, while the sediments
of the Narainnagar formation characterized by supratidal features contain blistered, domal and crinkled-laminar forms. The
types and sizes of stromatolites therefore are governed by the depositional conditions prevailing in the sedimentary basin. 相似文献
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Stromatolite, as the representative of recorder in the early life history of the Earth, has been traced back from 3.5 billion years to 3.7 billion years ago. Stromatolites do provide indirect evidence for the existence of early life on the Earth, especially the composition of modern carbonate stromatolites, which further proves that stromatolites are calcified structures of cyanobacterial mats. Among the modern carbonate stromatolites, the following examples have been studied for a long time: Coarse stromatolites on the platform of Bahamas, fine stromatolites in the ultra-salinity environment of Australia and ultra-salinity lagoon of southeastern Brazil. Based on the predecessors' research results, by tracing the growth mechanism of modern carbonate stromatolites and the complex microbial activities and deposition processes, the formation of stromatolites in the middle of the Zhangxia Formation of Cambrian in the Huolianzhai section of Benxi is obviously different from that of modern carbonate stromatolites, which indicates that the sedimentary model of modern stromatolites cannot be fully applied in the ancient stromatolites. Therefore, the comparison between modern carbonate stromatolites and ancient stromatolites provides a rich way to further understand the construction of Cambrian stromatolites and microbial carbonate factory. 相似文献
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皇藏峪及周边地区具有得天独厚的地质构造条件和自然地理环境,地质遗迹众多,分布集中,保存完整,构成了以皇藏峪国家森林公园为中心的地质遗迹景观区。主要地质遗迹有推覆构造、寒武纪和前寒武纪典型地层剖面、榴辉岩等深源捕虏体、灵璧石、叠层石等,具有重要的科学价值和美学价值。可以利用已有皇藏峪国家森林公园的旅游资源和知名度,开发地质遗迹为主题的地质旅游,建设并申报地质公园,建设地质博物馆,同时要系统开展地质遗迹调查工作,以及地质现象的成因研究工作,做好地质遗迹保护。 相似文献
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河南登封地区寒武系第三统馒头组二段中的核形石及其意义 总被引：1，自引：1，他引：0
河南登封地区寒武系第三统馒头组二段发育有三种类型的核形石:球状、椭球状核形石与大型柱状叠层石伴生,形成于高能的潮下带;长卵形核形石与小型柱状叠层石伴生,形成于低到中等能量的潮间带;不规则状核形石与近水平状、缓波状叠层石伴生,形成于低能的潮上带和潮间带。从核形石的成因可以看出,核形石等微生物成因构造与后生动物扰动构造存在耦合关系,水动力条件是核形石形态类型变化的决定因素,泥质（陆源物质）供应是影响核形石生长及消亡的直接因素。 相似文献
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Tadeusz M. Peryt M.Sc. 《International Journal of Earth Sciences》1975,64(1):143-158
When interpreting the depositional environment of the Buntsandstein sequence, thin stromatolite layers, if present, were often overlooked or given short shrift. The present paper provides evidence of value of stromatolites for the environmental interpretation of the Buntsandstein rocks. Algal stromatolites found in western Poland occur in form of thrombolites, LLH-type structures, SH-type structures, and rarely as oncolites. Stromatolites are usually associated with oolites. Very often stromatolites show important traces of scouring and channelling action of water. Since stromatolites occurred in the zone of clastic-carbonate deposition they were covered up by continuous sheet of detrital grains. Periodic catastrophic erosion and deposition was produced by hurricanes and severe storms in the peritidal and shallow subtidal zone. It is possible to distinguish the peritidal and subtidal stromatolites. In the vicinity of stromatolites are of frequent occurrence spirorbids, conchostracs, gastropods, and rare foraminifers. Besides, spirorbids are associated with stromatolites — they constituted the initial hard substratum for the stromatolitic structures and sometimes they also occur inside stromatolites. The not-hypersaline sedimentary environment of the Buntsandstein rocks can be compared with modern environments of the Persian Gulf and the Gulf of Aqaba. 相似文献