首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
安徽宿松,繁昌,江西彭泽间长江两岸的武穴组织透镜体展布,组成岩石类型(1)藻屑灰岩;(2)海绵灰岩;(3)棘屑灰岩;(4)核形石白云岩;(5)白云岩,从四条剖面的研究曲线由下向上明显地区分出三个粒屑含量与基质含量百分比连续变化序列,这种序列称基本单元,一般的变化规律为由下向上,由粗变细的正向序列,但是其中也有由细→粗→细的反向序列,这种反向序列反映出较快的沉积过程,往往起着障壁作用,几乎全由棘屑灰  相似文献   

2.
徐世球  李富强 《地球科学》1997,22(5):520-525
川黔湘交境早寒武世“变马冲组”为一套陆源碎屑岩沉积,是在三角洲环境中形成的,该组相当于一个Ⅱ型三级层序,由陆棚边级体系域、海侵体系域和高水位体系域组成,分别代表了三角洲发育、萎缩和再发育的3个演化阶段,陆棚边缘体系域期,发育充相、三角洲前缘相和前三角洲相,以三角洲前缘相为主;海侵体系系域期,发育三角洲前缘相和前三角洲相,以前三角洲相为主;高水位体系域期,发育三角洲平面相、前缘相和前三角洲相、以三角  相似文献   

3.
Pollen analysis, glacial varve chronology and palaeomagnetic measurements were carried out on Late Weichselian lake sediments from southwestern Smaland, south Sweden. The sequence is correlated to the GRIP event stratigraphy, expressed in calendar years BP, and covers the period from the deglaciation at c. 14 400 to 11 300 calendar years BP. The series encompasses c. 930 varves and has been connected to the local varve chronology. Varve thickness increases markedly after the Older Dryas stadial, which indicates an accelerated deglaciation and melting of dead ice. The pollen diagram displays the vegetation development from the deglaciation at c. 14 400 calendar years BP to the transition to the Holocene. The vegetation succession starts with an arctic pioneer vegetation at the deglaciation, changes to a more stable tundra environment and displays a development which concurs with the traditional lateglacial pollen stratigraphy for southern Sweden. A palaeo-magnetic secular variation curve is presented displaying two westerly declination swings at 14200-13800 and 12 800-11 600 calendar years BP, respectively. The upper one can be recognized from other palaeomagnetic stratigraphies from southern Sweden and Estonia.  相似文献   

4.
Tree-ring and peat stratigraphy data were examined back to 5000 BC in order to identify and compare humidity changes in Fennoscandia. The temporal variation in distribution of Scots pine ( Pinus sylvestris L.) was used as a measure of past lake-level fluctuations in central Sweden. The chronology, which spans 2893 BC–AD 1998 with minor gaps in AD 887–907 and 1633–1650 BC and with additional floating chronologies back to 4868 BC, was cross-dated and fixed to an absolute timescale using a chronology from Torneträsk, northern Sweden. The peat stratigraphy from the Stömyren peat bog, south-central Sweden, was transformed into humification indices to evaluate humidity changes during the past 8000 years. The peat chronology is established by four tephra datings and eight 14C datings. Synchronous periods of drier conditions, interpreted from regeneration and the mortality pattern of pine, tree-ring chronology and peat humification, were recognized at c. 4900–4800 BC, 2400–2200 BC, 2100–1800 BC, 1500–1100 BC, AD 50–200, AD 400–600 and AD 1350–1500. Possible wetter periods were encountered at 3600–3400 BC, 3200–2900 BC, 2200–2100 BC, 1700–1500 BC, 1100–900 BC, 100 BC-AD 50, AD 200–400, AD 750–900 and AD 1550–1700. The wet and dry periods revealed by the tree rings and peat stratigraphy data indicate considerable humidity changes in the Holocene.  相似文献   

5.
在详细的露头层序地层学研究的基础上,建立了贵州早、中三叠世台地和盆地过渡区2个三级层序7个四级层序和层序地层格架。并分析了该地区早、中三叠世地层微量元素分布的规律,探讨了三叠纪层序地层与微量元素之间的关系。  相似文献   

6.
南天山造山带综合地层学研究   总被引:8,自引:0,他引:8  
造山带综合地层学研究是造山带研究的重要基础问题之一 ,由于受区域构造和区域变质影响 ,造山带原始地层层序常受到强烈破坏 ,因此在区域地层研究中须采用综合地层学的方法。通过构造地层、岩石地层和生物地层等方面的综合研究 ,将南天山造山带古生代地层划分为四个地层小区 ,建立各自的地层序列和南天山造山带古生代地层的初步对比关系。  相似文献   

7.
Harbor-estuaries are complex sedimentary environments where both natural and anthropogenic processes influence the distribution and accumulation of sediments, which in turn is of importance for maintenance dredging and pollution control. This paper uses sediment characteristics from the Göta älv estuary, Sweden to evaluate the natural estuarine processes that persist despite the extensive human impact on the estuary and to separate and characterize depositional sub-environments. The most important harbor processes include maintenance dredging and turbulence from ship traffic, and their influence upon shallow stratigraphy and sediment distribution and deposition is significant. Polymodal particle-size distributions are interpreted to reflect the natural estuarine transport processes. Suspension transport is generally predominant, except in the river and inner harbor where bottom transport and selective deposition of sand occur. Particle-size characteristics divide the estuary into four depositional areas: the river and the inner, middle, and outer harbor. The shallow stratigraphy reveals a hiatus between the firm silty clays and the loose recent sediments. The hiatus in the stratigraphy is probably related to dredging in most areas of the harbor. Significant maintenance dredging and turbulence from ship traffic also influence the accumulation (0–61 cm) of recent sediments, during the 20th century.  相似文献   

8.
赣东北—皖南地区主体位于杨子板块与华夏(南)板坎接合部位,多期的构造成撞造山作用,使分布于其问的中元古代地居发生了不同程度的“非史密斯”化,单一的、传统的史密斯地居工作方法已不能适应该区的地质填图工作。通过对造山带等理论的具体运用,结合近年来在该区的工作实践,在构造—地层法基础上提出了造山带低级变质地居区先划分构造—岩坎,再分块建立地层层序的地质填图方法:构造—岩块—地层法。  相似文献   

9.
华南晚二叠世碳酸盐岩碳同位素旋回对海平面变化的响应   总被引:23,自引:1,他引:22  
李玉成 《沉积学报》1998,16(3):52-57
华南晚二叠世的碳同位素变化曲线是逐渐降低的,与全球海平面变化趋势相一致。华南晚二叠世碳酸盐岩碳同位素旋回可分为两个三级旋回,与两个三级海平面变化响应,其中吴家坪晚期和长兴期组成了一个三级旋回。华南长兴期识别出了三个四级碳同位素地层旋回可能与四级海平面变化旋回相对应。华南晚二叠世碳同位素旋回记录了全球海平面变化的信息:高值区和高海平面相对应,而低值区和低海平面相对应。  相似文献   

10.
The author gives a brief review of the most important research on Quaternary geology in Sweden during the last few years and the main lines of development of ideas. Emphasis is put on the present 'state of the art' within the following fields: Mapping, international projects, Quaternary deposits, dating methods, Pleistocene stratigraphy, glaciation models, deglaciation, sea-level changes, and Holocene.  相似文献   

11.
论沉积盆地分析领域的追踪与创新   总被引:17,自引:3,他引:17  
李思田 《沉积学报》1992,10(3):10-15
层序地层学的产生为研究盆地充埙提供了较完整的理论与方法体系。层序地层分析与当代沉积体系分析、构造-地层分析和高分辨事件地层分析的密切结合将形成新的综合的成因地层分析系统。  相似文献   

12.
Frost-shattered bedrock and ventifacts interpreted to be abraded by drifting snow or ice particles occur frequently in the wooded areas of northernmost Sweden. Ice-wedge casts and periglacial involutions are encountered more sporadically. The phenomena cannot be explained by the present or the Holocene climate and demonstrably pre-date the last deglaciation. The relation to glacial and non-glacial stratigraphy, and to ice flow during the latest glacial stade, strongly suggests that the periglacial activity dates from the local Tärendö Interstadial, tentatively correlated with Odderade. The presence of the periglacial features implies not only that different morphological formations survived the erosive impact of the last continental ice sheet but also that in wide areas the very ground surface, including ventifacts in primary position, is the same today as during the interstadial. A similar situation appears to prevail in northernmost Dalecarlia and parts of Härjedalen and Jämtland in central Sweden.  相似文献   

13.
华南二叠纪盆地层序地层特征及聚煤规律   总被引:3,自引:0,他引:3  
龚绍礼  张春晓 《地学前缘》1999,6(Z1):167-173
华南二叠系形成于基底构造不均一的陆表海盆地,古特提斯海的演化控制着华南板块上二叠纪的构造格局及沉积、聚煤作用。华南二叠纪可划分为6个Ⅲ级层序。在不同构造区域层序地层界面有其特殊的识别标志,层序地层也有不同模式,主要表现为低位体系域(LST各有不同的沉积特点,聚煤作用在不同体系域也各有规律。  相似文献   

14.
This study presents the Weichselian stratigraphy on Kriegers Flak in the southwestern Baltic Sea, and correlates it to new sections in southernmost Sweden and to previously published stratigraphic sequences from SW Skåne. A total of four Weichselian advances are identified based on our correlations. The oldest till, observed only on Kriegers Flak, is dated to the Early or Middle Weichselian and tentatively correlated to the Ristinge advance, previously identified in Denmark. It is overlain by three interstadial sediment units, starting with brackish clay and followed by terrestrial and lacustrine deposits, which have been dated to 42–36 ka, and finally by glaciolacustrine clay dated to 28.5–26 ka. After 30 ka, the Fennoscandian ice sheet advanced through the Baltic Basin and into the coastal areas of southernmost Sweden where the Allarp Till was deposited, followed by a deglaciation sequence. The uppermost tills, the Dalby Till and the Lund till, were deposited during the LGM advance and the subsequent re‐advances through the Baltic Basin. Based on the new evidence it has been possible to identify and date a Middle and Late Weichselian till succession in southern Sweden and provide a strong correlation to the established glacial stratigraphies in Sweden and Denmark.  相似文献   

15.
Robertsson, A.-M., Svedlund, J.-O., Andrén, T. & Sundh, M. 1997 (September): Pleistocene stratigraphy in the Dellen region, central Sweden. Boreas, Vol. 26, pp. 237–260. Oslo. ISSN 0300–9483. The Pleistocene stratigraphy in the Dellen region, central Sweden was studied using field observations made during mapping of Quaternary deposits and fabric analyses in excavated sections. The lithostratigraphy was also studied by seismic refraction measurements, analyses of grain-size distribution and organic carbon content. Biostratigraphical methods applied were pollen and diatom analyses. A general outline of the Pleistocene stratigraphy in the area is presented. Three different till beds are identified, the lowermost suggested to have been deposited during the Saalian glaciation and the other two during the Weichselian glaciation. According to the interpretation of the stratigraphy, it is questioned whether the first Weichselian ice sheet did in fact reach the Dellen area. A clayey sediment sequence at Norra Sannas accumulated during an interglacial, probably the Eemian. Most of the interglacial vegetation succession is reflected in the identified pollen flora. An initial phase with a light-demanding forest of Belula and Pinus was followed by immigration of Alnus, Picea and scattered occurrences of Corylus. A freshwater diatom flora was identified dominated by plankton taxa, e.g. Aulacoseira italica, A. distans and Cyclotella spp. In the lower part of the sequence a brackish-marine flora was registered, representing accumulation in a bay of the Eemian Sea. Fine-grained sediments at the Sundson and Vastansjd sites are interpreted as rebedded Eemian sediments according to the pollen flora. An (Early Weichselian) interstadial age is suggested for sediments found at Bjuraker. Dating by the 14C- and OSL methods was carried out on the interglacial and interstadial sediments, respectively. The ages range from approximately 19000 to 92000 BP. Correlation of interglacial vegetation history with central Finland and other areas is discussed.  相似文献   

16.
A revised lithostratigraphy of Skåne, South Sweden, constitutes the basis of an alternative Weichselian glaciation model for southern Scandinavia, progressively anchored to the stratigraphy. Skåne was not glaciated during the Weichselian until 21,000 B.P. The concepts, outlet surge and marginal dome (the main tools of the model) are defined. The palaeogeography of the Baltic and Kattegatt basins during the Mid-Weichselian are reconstructed. Shorelines, during the advance stage, are calculated from an inferred proglacial depression. Outlet surges, which occurred in three basins of the Baltic, guided the ice sheet during its growth. The growth of marginal domes on the outlet surge lobes resulted in changes in the configuration of the ice sheet and in the lowering of its surface profile. The South Scandinavian ice divide became located over a former outlet surge lobe NNE-NE of the island of Gotland in the northern Baltic. This gave the main ice in South Sweden and Denmark a NE ice movement during the whole glaciation until the deglaciation of SE Sweden. The Kattegatt Ice Lake was formed due to damming in the Skagerack area. Surging ice tilled in the basin resulting in the formation of vast areas of stagnant ice in front of the advancing NE-ice. Marginal domes were formed on these giving rise to the early glacial episodes in the southwest of Sweden and Denmark. During the deglactanon, tnree pnases of marginal dome formation are recorded in the soutnern Baltic area and the growth of these domes resulted in the East Jylland advance, the Bælthav readvance and the Simrishamn readvance. The marginal domes were formed on vast fields of stagnant ice left behind by the receding main ice. Baltic erratics, englacially present in the main ice as well as in the stagnant ice in front of it, were transported (stepwise) towards the west and northwest, partly by the advancing marginal domes and partly by ice streams formed between the marginal domes and the main (NE-) ice. It is argued that the classical, so-called Low Baltic ice stream in the sense of a readvancing glacier lobe never existed. The first two marginal domes collapsed due to starvation and the ice movement returned gradually to the independent NE ice movement of the main ice. The third marginal dome collapsed due to a downdraw caused by a large transgression recorded in the Kattegatt and the Öresund regions. The transgression took place roughly around 13,300 B.P. and was possibly caused by damming of the Kattegatt basin in the north in connection with a marine downdraw. The collapse of the third marginal dome and the subsequent ‘ice lake downdraw’ of the dome centre NNE-NE of Gotland took place during a cold period of the deglaciation. This resulted in an extremely high recessional rate on the Swedish cast coast compared with the west coast and a contemporaneous westwards displacement of the South Scandinavian ice divide. After the downdraw, the recession rate on the east coast slowed down markedly and became more or less equal to that of the west coast. Pure dynamic causes for the extremely high recession rate in SE Sweden are expected because the decrease in this rate coincides with the onset of a recorded, marked climatic amelioration at around 12,600 B.P. Formation of the marginal domes during the deglaciation indicates periods of increased cyclon activity at the southwest margin of the Weichsclian Scandinavian ice sheet alternating with periods of ice sheet starvation. Detailed modelling of the marginal domes is therefore expected to have significant palaeoclimatic implications. The marginal dome concept is believed to he useful also in the reconstruction of earlier glaciations.  相似文献   

17.
吉辽徐淮地区新元古代地层对比格架   总被引:3,自引:0,他引:3  
根据层序地层学最大海泛,Sr、C同位素测年,地质事件,生物化石和古地磁资料对吉辽徐淮地区新元古代地层进行了时代界定和对比。研究表明吉辽徐淮地区震旦纪海平面变化趋势基本一致,旋回层序基本上可以对比,其沉积主体除辽南兴民村组和淮北史家组的2个数据小于750Ma之外,相互之间的Sr、C同位素比值对比性很好,沉积时限在750—860Ma之间,为北方青白口系之后的沉积。吉南的八道江组、辽南的十三里台组和徐淮的魏集组可作为三地的对比标志,并提出了新的地层对比方案。  相似文献   

18.
Problems of Sequence Stratigraphy in China   总被引:4,自引:0,他引:4  
Sequence stratigraphy is the study of rock relationshipwithin a chronostratigraphic fram ework of the genetically re-lated strata bounded by unconform ities and its correlative con-formities(Van Wagoner,1995 ) .As a subdiscipline of stratig-raphy,sequence stratigraphy evolved in the late 1980 s fromseismic stratigraphy which was established in the late 1970 s(Mitchum,1977;Mitchum et al.,1977;Vail et al.,1977) .Although the history of sequence stratigraphy as a subdisci-pline is very brief,th…  相似文献   

19.
中国南方古特提斯阶段的构造古地理格局   总被引:8,自引:2,他引:8  
对于华南及秦岭造山带的大地构造演化存在不同的认识,其关键问题是地层时代的归属不同,笔者提出造山带地层的研究方法,对华南及秦岭地区近年来深水相古生物学及地层学研究进展进行了综述,指出海西-印支期扬子板块周缘存在的许多大小不等的陆块,它们被不同海域性质的深水盆地包围,扬子板块及这些陆块群为全球古特提斯多岛洋的一个组成部分。  相似文献   

20.
Upper Devonian and Lower Carboniferous Sequence Stratigraphy of South China   总被引:9,自引:0,他引:9  
SequencestratigraphyhashopaidmoreattentionforitSrelativelycompletetheoreticalsyStemandgreatsuchesinpracticesinceitwasadvancedinthe197ds.Integratingonthedataofbiostratiglaphy,lithostratigraphy,seismicstfstigraphy,geochendstryandsedirnentology,sequencestratigraphyattemptStoestablishachronostratigraphicframeworkandcormectsdepositionalsequencewithglobalsealevelchange,andhencemakeSitpossibletOpreciselycorrelatethestrataindifferentfactesareasoveraconsiderabledistance,evenovertheworld.TheUpperDevon…  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号