Faunal trends and sea-level changes: biogeographic patterns of Kimmeridgian ammonites on the Western European Shelf     

P. Hantzpergue 《International Journal of Earth Sciences》1995,84(2):245-254

The Kimmeridgian series of the northern Aquitaine margin is representative of the marine sedimentation on the Western European Shelf. It has been used to demonstrate a fundamental relationship between relative sea-level changes and the biogeographic dynamics of the Kimmeridgian ammonites.This synthesis, based on comparative sedimentological and paleobiogeographical studies, shows that the shelf was settled by submediterranean and/or subboreal ammonites during transgressive phases and maximum sea-level rises. Endemic lineages differentiated during the sea-level highstands and the beginning of lowstands. Correlative with the long-term sea-level rise, endemic elements have progressively taken a prominent role within the Kimmeridgian ammonite faunas of the shelf.The patterns of faunal changes have been deduced from studies of ammonite lineages from distinctive biogeographic origins: Rasenioides, Lithacosphinctes, Orthaspidoceras and Gravesia. Compared with subboreal ammonites, it seems that the submediterranean species were more tolerant of changing environments and adapted to new environments more easily. Therefore most of the endemic lineages which settled the Western European area originated in submediterranean faunas.  相似文献   

溆浦陆相红盆地质特征及其演化探讨     

李福顺 《湖南地质》2001,20(1):1-4

本文根据构造－岩性－岩相法，将涂浦红盆划分为5个岩组，4类构造界面，2个二级层序地层，进而探讨了该陆相红盆的演化特征。  相似文献   

层序地层研究——找矿勘探的重要手段   总被引：1，自引：0，他引：1       下载免费PDF全文

李志明  刘家军 《地质找矿论丛》2001,16(4):215-218

层序地层地理论和方法已在油气勘探开发中发近重要作用，实践证明层序界面，沉积体系域对沉积，层控型矿床的成矿作用具控制作用，文章从理论和实例阐述了层序界面，沉积体系域的控矿作用，指出层序地层研究将是找矿勘探的重要手段。  相似文献   

A role for organic petrology in integrated studies of mudrocks: examples from Devonian black shales of the eastern US     

Jürgen Schieber   《International Journal of Coal Geology》2001,47(3-4)

Over the years, the study of mudrocks has lagged far behind that of other lithologies, a circumstance that is in part due to their fine-grained nature, and in part due to economic realities. Yet, within petroleum systems mudstones are usually the main source of hydrocarbons and typically are also important as hydrocarbon seals. Recent work on Late Devonian mudstones from the eastern US shows that much progress can be made through an integration of outcrop study, macro- and micropaleontology, ichnofossils, gamma ray spectroscopy, microscopic examination of thin sections in transmitted and reflected light, electron microscopy (SEM, BSE), electron microprobe, carbon and sulfur isotopes, and organic geochemistry.Erosion surfaces within this black shale succession have been traced over large distances and provide the foundation for a sequence stratigraphic re-interpretation of these rocks. Evidence of storm wave reworking of the seabed, as well as the realization that benthic colonization was much more widespread than previously believed, suggest that anoxic conditions in the water column were not a controlling factor in the accumulation of the large quantities of organic matter found in these shales.These distal Devonian shales accumulated slowly and allowed accumulation of large proportions of organic matter. In modern settings of abundant organic matter accumulation, the original material is broken down by bacteria within a matter of months into a mass of largely unidentifiable organic particles and extracellular bacterial slime. Although one can still find identifiable material within this mass, slime and amorphous material strongly dominate. After burial and maturation this material turns into the various organic macerals that organic petrologists are accustomed to describe. One might wonder in this context, how much information about the origin of a given mudstone unit can we hope to extract through organic petrology?In order to illustrate how organic petrology of mudrocks can contribute to their better understanding, Late Devonian black shales of the eastern US will be examined from a sedimentological perspective. Combining sedimentologic and geochemical data with basic observations on organic petrology, illustrates how the latter can contribute to more realistic scenarios of black shale genesis.  相似文献   

Tectonothermal evolution of the High Himalayan Crystalline Sequence, Langtang Valley, northern Nepal   总被引：15，自引：0，他引：15  

S. INGER  N. B. W. HARRIS 《Journal of Metamorphic Geology》1992,10(3):439-452

The High Himalayan Crystalline Sequence in north-central Nepal is a 15-km-thick pile of metasediments that is bound by the Main Central Thrust to the south and a normal fault to the north. The Langtang section through the metasediments shows an apparent inversion of metamorphic isograds with high-P, kyanite-grade rocks exposed beneath low-P, sillimanite-grade rocks. Textural evidence confirms that the observed inversion is a result of a polyphase metamorphic history and phase equilibria studies indicate that thermal decoupling has occurred within a mechanically coherent section of crust. Rocks now exposed at the base of the High Himalayan thrust sheet underwent Barrovian regional metamorphism (M1) prior to 34 Ma in the early stages of the Himalayan orogeny, recording metamorphic conditions of T= 710 ± 30° C, P= 9 ± 1 kbar. After the activation of the Main Central Thrust, which emplaced these metapelites southwards onto the lower grade Lesser Himalayan formations, the upper part of the thrust sheet was overprinted by a second heating event (M2), resulting in sillimanite-grade metamorphism and anatexis of metapelites at T= 760 ± 30° C, P= 5.8 ± 0.4 kbar between 17 and 20 Ma. Crustally derived, leucogranite magmas have been emplaced into low-grade Tethyan sediments on the hangingwall of the normal fault that bounds the northern limit of the metapelitic sequence. The cause of the selective heating of the upper section of the metasediments during M2 cannot be reconciled with either post-thrusting thermal relaxation or advection models. The cause of M2 remains problematical but it is suggested that heat focusing has occurred at the top of the High Himalayan Crystalline Sequence as a result of movement on the normal fault blanketing metapelites of high heat productivity with low-grade sediments of low thermal conductivity. This model implies that the normal fault was active before M2, consistent with decompression textures that formed during, or shortly after, sillimanite-grade metamorphism.  相似文献   

断层气Rn、Hg时值序列中的潮汐波分量     

张慧  王长岭 《地震工程学报》1993,15(3):19-24

本文采用潮汐波最优谱分析法,对武山观测点断层气Rn、Hg时值资料进行了计算分析。结果表明,断层气Rn、Hg时值序列中存在着与理论固体潮相一致的半日波和日波分量,说明上述两种气体组分浓度的变化能够反映地壳岩石的应力、应变。本文的研究结果为用断层气预报地震的研究提供了一定的理论依据。  相似文献   

浙江江山晚古生代岩相古地理及其构造控制   总被引：3，自引：0，他引：3       下载免费PDF全文

郭福生 《沉积与特提斯地质》1993,(6):44-52

根据岩石学、古生态学、地球化学特征及沉积序列,结合区域地质资料的系统研究,本文论述了浙江江山地区石炭纪和二叠纪沉积相与沉积环境的演变规律及其构造意义。叶家塘组属辫状河流快速堆积的产物,区域上为早石炭世大塘期华夏古陆西缘冲积相带的组成部分;藕塘底组具海陆交互沉积特征,剖面结构为岸进序列;石头山灰岩为浅海碳酸盐台地稳定沉积;丁家山组是浙西台地发展过程中浑水干扰叠加的产物。研究表明,华夏古陆在晚石炭世威宁期和早二叠世茅口期发生过差异性隆起,威宁期隆升造成藕塘底组的岸进序列。茅口期隆升提供泥砂浑求,浙皖海盆碳酸盐台地的发育受到干扰。由此可见,古陆间歇性活跃、海浸持续稳定是本区华力西期构造发展的基本特点。  相似文献   

中缅交界地区6.9级强震与地电阻率突变序列     

刘心恒  周郧生 《地震研究》1994,17(3):216-221

根据断裂力学观点，分析了１９９２年４月２３日中缅交界６．９级地震的地电变化、结果表明，震前震中附近的台站，也观测到了有关地震的地震的地电阻率突变与突变序列异常、这使曾在全国短临预报计研会（１９９０．１０兰州）上提出的地电阻率突变序列法受到一次很好的实际检验，从而更加证实了该法在短临预报实际应用中的可行性。  相似文献   

燕山地区蓟县纪：青白口纪层序地层学初探     

刘振锋  郑桂森 《城市地质》1994,(3):10-15

本文对燕山地区蓟县纪～青白口纪的层序地层学问题作了初步研究。着重描述了各组、段岩石的基本层序特征和沉积体系域，共划分出两个Ⅰ型层序和一个Ⅱ型层序，并对岩石地层格架作了初步的解释。  相似文献   

TEMPORAL ORDERLINESS OF EARTHQUAKES (M≥8) ON CHINA MAINLAND——A NEW APPROACH TO THE PREDICTION OF EARTHQUAKES   总被引：2，自引：0，他引：2  

Xu Dao-yi  Huang Jian-fa  Wang Xiang-nan 《地震地质》1991,13(3):237

Some great earthquakes of magnitude 8 or greater on China mainland repeatedly occurred at the intervals of 252, 94, 48, and 25 years. It incited us to study the time interval between every pair of great earthquakes (M≥8) on China mainland. The result shows that there are four groups of clear orderliness distinguished in the most disorder distribution of earthquakes. The distinguished orderliness can be used to estimate the occurrence of next great earthquakes in China  相似文献