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1.
The marine benthic fauna and the δ18Oc of foraminifers and ostracods from six sites situated on a west–east transect through central Sweden have been analysed in order to estimate the palaeosalinity and palaeocirculation in this shallow‐marine environment. The measurements have been undertaken on material from the early Preboreal, when the Baltic Basin was in contact with the North Sea through straits in central Sweden. The δ18Oc values have a more negative value towards the east, indicating decreasing salinity. This was the result of limited possibilities for marine water to penetrate into the Baltic Basin and the mixing with freshwater from the melting Fennoscandian ice‐sheet. Four water masses existed in the area: a surface layer of freshwater, marine water from the North Sea, brackish–marine intermediate water on the Swedish west coast and brackish Yoldia Sea water in the Baltic Basin. The chronology is based on radiocarbon dates of marine fossils and, at one site, on the occurrence of the Vedde Ash (10 400–10 300 14C yr BP). This is the first record from marine settings in Sweden. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

2.
Isoleucine epimerization (alle/Ile) ratios have been measured on foraminiferal tests from interglaical sites in the southern North Sea region. In order to evaluate the possibilities of this amino acid method on benthic foraminifera, sites were chosen from areas where the stratigraphy was already well known. The study demonstrates that the isoleucine epimerization reaction in benthic foraminifera can be used for correlation and as a means of relative age estimation within a limited geographic area. Previous suggestions of a Holsteinian age for the Rugrd, Tornskov, and Wacken sites are supported for the Kås Hoved site. The age of most presumed Eemian sites is supported by the amino acid results; the Reighton site also seems to belong in this interglacial.  相似文献   

3.
A new sea-level curve (MHW, mean high water level) for the southern North Sea is presented, spanning the last 10 000 years and based on new data recently obtained along the German coast. The 118 dates were selected from basal as well as intercalated peats of the Holocene sequence and archaeological dates from the last 3000 years. Because of different MHW levels along the German North Sea coast, all data were corrected to the standard tide gauge at Wilhelmshaven to make them comparable. Special advantages of this area for sea-level reconstructions are negligible tectonic and isostatic subsidence and the absence of coastal barrier systems that might have mitigated or masked sea-level changes. Changes of water level had therefore immediate consequences for the facies and could be dated exactly. The chronostratigraphic Calais-Dunkirk system has been improved and adapted to the new data. Altogether seven regressions (R 1-R 7) have been identified, each of them characterized by a distinct decline in sea level. These fluctuations are in accord with the evidence from other parts of the North Sea region. A draft of former North Sea shorelines is presented on the basis of this sea-level curve.  相似文献   

4.
BOREAS Harland, R., Gregory, Diane M., Hughes, M. J. & Wilkinson, I. P. 1978 06 01: A late Quaternary bio- and climatostratigraphy for marine sediments in the north-central part of the North Sea. Boreas, Vol. 7, pp. 91–96. Oslo. ISSN 0300–9483.
Micropalaeontological studies of three boreholes in the north-central North Sea have led to the erection of a bio- and climatostratigraphy for the area. Palaeoenvironmental interpretations have depended largely upon oceanographic concepts and changes in the micropalaeontological assemblages have been related to postulated alterations in water mass regimes. The biostratigraphy can then be utilized as a climatostratigraphy since such water mass changes are most probably linked to alterations in the circulation of the North Atlantic, and in particular to the positions of the climatically important North Atlantic Current and Polar Front. The North Sea sequences are compared to similar sections in Europe and related to the commonly accepted standard chronostratigraphy.  相似文献   

5.
Seismic slip vectors along the Japan Trench, the eastern margin of the Japan Sea and the Sagami Trough are compared with global relative plate motions (RM2, Minster and Jordan, 1978) to test a new hypothesis that northern Honshu, Japan, is part of the North American plate. This hypothesis also claims that the eastern margin of the Japan Sea is a nascent convergent plate boundary (Kobayashi, 1983; Nakamura, 1983).Seismic slip vectors along the Japan Trench are more parallel to the direction of the Pacific-North American relative motion than that of the Pacific-Eurasian relative motion. However, the difference in calculated relative motions is too small avoid to the possibility that a systematic bias in seismic slip vectors due to anomalous velocity structure beneath island arcs causes this apparent coincidence. Seismic slip vectors and rates of shortening along the eastern margin of the Japan Sea for the past 400 years are also consistent with the relative motion between the North American and Eurasian plates calculated there. Seismic slip vectors and horizontal crustal strain patterns revealed by geodetic surveys in south Kanto, beneath which the Philippine Sea plate is subducting, indicate two major directions; one is the relative motion between the North American and Philippine Sea plates, and the other that between the Eurasian and Philippine Sea plates.One possible interpretation of this is that the eastern margin of the Japan Sea may be in an embryonic stage of plate convergence and the jump of the North American-Eurasian plate boundary from Sakhalin-central Hokkaido to the eastern margin of the Japan Sea has not yet been accomplished. In this case northern Honshu is a microplate which does not have a driving force itself and its motion is affected by the surrounding major plates, behaving as part of either the Eurasian or North American plate. Another possibility is that the seismic slip vectors and crustal deformations in south Kanto do not correctly represent the relative motion between plates but represent the stresses due to non-rigid behaviors of part of northern Honshu.  相似文献   

6.
鄂尔多斯盆地奥陶纪华北海和祁连海演变及岩相古地理特征   总被引：31，自引：5，他引：31  
鄂尔多斯盆地奥陶纪华北海与祁连海演变关系是多年来研究中的一大难题。本依据古生态演化的不可逆性及地理分区，并结合盆地中东部、西部和南部奥陶纪地层的系统对比，深入探讨了奥陶纪牙形刺动物群在不同沉积分区的演化特征及其与华北海和祁连海之间的关系。并在此基础上，将祁连海侵漫到盆地西缘地区的时间，确定在华北海马家沟四期最大海侵的晚期，侵漫范围尚末过中央古隆起带的鄂6井到定探1井一线。中央古隆起在马家沟四期沉积后，对华北海和祁连海具有明显的分隔作用。根据牙形刺动物群的面貌及不同阶段的地理分区，结合古构造格局及岩石、岩相标志，系统分析了奥陶纪不同阶段的沉积特征，再现了各期岩相古地理面貌，为鄂尔多斯奥陶系天然气勘探奠定了地质基础。  相似文献   

7.
Gravitational collapse in response to the creation of salt swells and diapirs is a common phenomenon within regions such as the Southern North Sea. Although collapse faulting and slumping of linear salt swell flanks has previously been documented, the existence of concentric collapse structures surrounding diapirs and isolated salt lows is a recently recognised feature. 3-D seismic data from the Southern North Sea demonstrates that concentric collapse faulting around both diapirs and subcircular salt lows is common. The recognition of concentric collapse structures formed in response to salt withdrawal, and adjacent inflation, provides an alternative mechanism for the origin of the proposed Silverpit impact crater.  相似文献   

8.
As the majority of the data on Quaternary sediments from the North Sea Basin are seismostratigraphical, we analysed the Elsterian Swarte Bank Formation, the Late Saalian Fisher Formation and the Late Weichselian (Dimlington Stadial) Bolders Bank Formation in order to determine genesis and provenance. The Swarte Bank Formation is a subglacial till containing palynomorphs from the Moray Forth and the northeastern North Sea, and metamorphic heavy minerals from the Scottish Highlands. The Fisher Formation was sampled from the northern and central North Sea. In the north, it is interpreted as a subglacial till, with glaciomarine sediments cropping out further south. These sediments exhibit a provenance signature consistent with the Midland Valley of Scotland, the Eocene of the North Sea Basin, the Grampian Highlands and northeast Scotland. The Bolders Bank Formation is a subglacial till containing palynomorphs from the Midland Valley of Scotland, northern Britain, and a metamorphic heavy‐mineral suite indicative of the Grampian Highlands, Southern Uplands and northeast Scotland. These data demonstrate that there was repeated glaciation of the North Sea Basin during the Middle and Late Pleistocene, with ice sheets originating in northern Scotland. There was no evidence for a Scandinavian ice sheet in the western North Sea basin. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

9.
北黄海盆地构造变形及动力学演化过程   总被引：2，自引：0，他引：2  
李文勇 《地质学报》2007,81(5):588-598
以北黄海盆地构造几何学、运动学特征为基础,探讨了北黄海盆地的构造变形样式及动力学演化过程。研究表明,北黄海盆地的构造变形包括伸展构造变形、挤压构造变形、扭动构造变形以及反转构造变形等,北黄海盆地发育的区域动力学背景即是以区域拉伸作用为主、且叠加有水平挤压作用以及相关的扭动作用,并由此导致了北黄海盆地是以一系列地堑、半地堑式坳陷组成的拉张断陷盆地;北黄海盆地的伸展、挤压与升降作用受控于板块相互作用引起的区域引张与挤压应力场并辅以深部软流圈的微弱上拱隆起作用,其动力学演化过程包括晚侏罗世—早白垩世伸展断陷、晚白垩世—古新世热隆、始新世—渐新世裂陷、渐新世末期—新近纪早期构造反转以及新近纪热沉降等5个阶段。  相似文献   

10.
A 140.2 m deep boring (BH 81/29) from the central North Sea (British sector) has been investigated for its foraminiferal content. Fourteen assemblage zones are identified, and these are correlated with other records from the North Sea region. The stratigraphical interpretation of BH 81/29 is supported by palaeomagnetic data and by amino acid dates and thermoluminescence dates from the same boring. Foraminiferal zones 14 to 8, from the bottom of the core, have been referred to the Early Pleistocene. Zones 7 to 4, which occur above the Bruhnes/Matuyama boundary, seem to belonged in the Middle Pleistocene, and zones 3 to 1 are referred to the Late Pleistocene. A characteristic feature of the present sequence is that a major part of the Quaternary record seems to be missing. As is also known from other areas of the North Sea, interglacial deposits are especially badly represented.  相似文献   

11.
《Geochimica et cosmochimica acta》1999,63(13-14):1991-1999
Vertical profiles of dissolved indium and yttrium were determined in the eastern North Atlantic and the Mediterranean Sea to compare with those of the North Pacific reported earlier. The Y concentrations in the surface waters are 120 pmol/kg in the North Atlantic and 205 pmol/kg in the Mediterranean Sea, which are significantly higher than 80 pmol/kg in the North Pacific. The difference may be attributable to the different strength of input of Y to the oceans from fluvial and aeolian sources. In contrast, the deep water concentration of Y increases in the order of North Atlantic < Mediterranean < North Pacific. This trend is similar to that of dissolved Si, suggesting that Y is involved in the biogeochemical regeneration cycle. The vertical profiles of In are far more complex than Y. The In profile shows a systematic increase from 0.6 pmol/kg at the surface to 1.7 pmol/kg at 2100 m in the North Atlantic, whereas it is almost featureless at a mean concentration of 3.8 ± 0.6 pmol/kg in the Mediterranean Sea. The North Atlantic and Mediterranean In concentrations are considerably higher than those observed in the North Pacific (∼0.1 pmol/kg), and such a large interoceanic variation has been reported before only for Al and Ga. Like Al, the deep water In concentration that decreases in the order of Mediterranean > North > North Pacific exhibits an inverse trend of Y and nutrients. Indium is highly particle-reactive (47% association in the Mediterranean Sea), and must have a short mean oceanic residence time. However, the featureless dissolved In profile in the Mediterranean Sea is clearly different from the profiles of dissolved Al, showing increase with depth Hydes et al 1988, Measures and Edmond 1988, suggesting that significant fractionation of the two elements is taking place in the ocean.The interoceanic variations of dissolved In and Al may be ascribed to the different intensities of external input of which aeolian has been considered to be major rather than fluvial. However, the difference of In and Al concentrations in the deep waters of the above oceanic basins are significantly greater than those of other refractory elements, such as Ce, Ti, Hf, and Zr, whose major sources to the ocean are also considered to be aeolian. Furthermore, the In/Al ratios in seawater are about two orders of magnitude greater than the average crustal ratio. Thus, some additional sources, though not yet certain, may be required to explain the high concentrations of In in the Atlantic and the Mediterranean deep waters.  相似文献   

12.
This paper details and describes a suite of 143 sub-seismic-scale clastic injectites encountered within the early Cretaceous, early post-rift of the deep-lacustrine North Falkland Basin. The injectites, referred to here as the Sea Lion Injectite System, are encountered below, above and in between the hydrocarbon-bearing, deep-lacustrine turbidite sandstones of the Bleaker 30, Sea Lion North, Sea Lion, Casper and Beverley fans. Sedimentary structures are documented within the injectites including: planar laminations, mud-clast imbrication and clast alignment. Clasts align along centimetre-scale foresets formed through ripple-scale bedform migration in a hydraulically-open fracture. The style of flow within the injectite system is interpreted as initially through fluid turbulence during an open fracture phase, which was followed by a later stage where laminar flow dominated, most likely during the closing phase of the fracture system. The host rocks display evidence for ductile deformation, which along with ptygmatic folding of dykes and internally injected mud-clasts, suggests a period of injection into relatively uncompacted sediments. Evidence for brittle fracturing, in the form of stepped margins may be indicative of a separate phase of emplacement into more-compacted sediments. This variability in deformation styles is related to multi-phased injection episodes into host strata at different stages of consolidation and lithification at shallow burial depths. Injectites have been identified in four stratigraphic groupings: above the Bleaker 30 Fan and within/above the Sea Lion North Fan; within the hydrocarbon-bearing Sea Lion Fan; overlying the Sea Lion Fan; and above/below the hydrocarbon-bearing Casper and Beverley fans. This spatial association with the hydrocarbon-bearing fans of the North Falkland Basin is important, considering the ability of injectite networks to form effective fluid-flow conduits in the subsurface. Consequently, the findings of this study will improve the characterization of sub-seismic scale injectites (and therefore fluid conduits) within otherwise impermeable strata.  相似文献   

13.
东亚石炭-二叠纪有孔虫迁移与海水进退规程的相关模式   总被引：1，自引：0，他引：1  
徐炳川 《地球学报》1996,17(Z1):155-163
亚洲东部石炭-二叠纪生物地层，沿北纬42°左右存在一条质变线。此线南北海水进退呈现互为消长的关系，反映了海水南北方向的4次活动过程：早石炭世早与早二叠世，自南而北；中晚石炭世与晚二叠世，自北而南。生物最低层位的变化情况，反映了生物也经历了相应的南北方向的4次迁移过程。这种迁移可能与气候的冷暖变化有关，而海水运动可能源于地球自转速率的不均衡，甚至气候的变化最终也是地球自转不均衡的结果。  相似文献   

14.
The methane concentration in the atmosphere andsurface water was surveyed along 58° N acrossthe North Sea. In addition, the vertical methanedistribution in the water column was determined at sixstations along the transect. The methane contents ofthe surface water as well as in the water column wereextremely inhomogeneous. Input by freshwater fromriver discharge and injection of methane from thesediment were both observed. The survey continued fromthe western side of the North Sea to the Elbe Riverestuary. The Elbe River appears to have low methaneconcentrations compared to other European rivers, itsaverage input into the North Sea is estimated to be70 nmol s-1 of methane. Near 58° N,1°40' E, an abandoned drill site releases about 25 % ofthe North Sea's emission of methane to the atmosphere.The advective methane transport induced by watercirculation was assessed for May 16, 1994, using a 3-DNorth Sea circulation model. For the period of thissurvey, the North Sea's source strength foratmospheric methane is estimated using in situwind velocities. In comparison to the advectivetransport by the water circulation, the gas flux tothe atmosphere appears to be the dominant sink ofNorth Sea methane. This flux is estimated to bebetween 1500 · 106 mol a-1 and 3100 ·106mol a-1, depending on the relationbetween wind speed and gas transfer velocity.  相似文献   

15.
The North Yellow Sea Basin is a Mesozoic and Cenozoic basin.Based on basin-margin facies,sedimentary thinning,size and shape of the basin and vitrinite reflectance.North Yellow Sea Basin is not a residual basin.Analysis of the development of the basin’s three structural layers,self-contained petroleum systems,boundary fault activity,migration of the Mesozoie—Cenozoic sedimentation centers, different basin structures formed during different periods,and superposition of a two-stage extended basin and one-stage depression basin,the North Yellow Sea Basin is recognized as a superimposed basin.  相似文献   

16.
秦岭二叠纪古海洋再造   总被引：3，自引：2，他引：3       下载免费PDF全文
杨逢清  王治平 《地球科学》1995,20(6):641-647
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17.
Parke  Minshull  erson  White  McKenzie  Ku&#;çu  Bull  Görür  & &#;engör 《地学学报》1999,11(5):223-227
Turkey is moving westward relative to Eurasia, thereby accommodating the collision between Arabia and Eurasia. This motion is mostly taken up by strike-slip deformation along the North and East Anatolian Faults. The Sea of Marmara lies over the direct westward continuation of the North Anatolian Fault zone. Just east of the Sea of Marmara, the North Anatolian Fault splits into three strands, two of which continue into the sea. While the locations of the faults are well constrained on land, it has not yet been determined how the deformation is transferred across the Sea of Marmara, onto the faults on the west coast of Turkey. We present results from a seismic reflection survey undertaken to map the faults as they continue through the three deep Marmara Sea basins of Çlnarclk, Central Marmara and Tekirdag, in order to determine how the deformation is distributed across the Sea of Marmara, and how it is taken up on the western side of the sea. The data show active dipping faults with associated tilting of sedimentary layers, connecting the North Anatolian Fault to strike-slip faults that cut the Biga and Gallipoli Peninsulas.  相似文献   

18.
Non-marine strata of Early Cretaceous age ('Wealden facies') are found at outcrop in the type localities of the Wessex Basins, southern England (and adjacent subsurface) and in extensive and thick successions filling the North Celtic Sea Basin. Sedimentology, paleontology, petrology and geochemistry have traditionally been used as evidence in determining the climatic, tectonic and sea level controls on Wealden facies, sedimentary processes and stratigraphy. Analysis of seismic data, through seismic facies and sequence stratigraphic analysis, allows direct comparison of the Wealden in these basins and new interpretations to be made of the tectonic and depositional influences. In the north-eastern end of the North Celtic Sea Basin, tectonic controls on seismic facies can be demonstrated and are related to coarse-grained fan-delta horizons documented in core. In the south-western North Celtic Sea Basin, adjacent to the Cretaceous proto-Atlantic, tectonic controls are less apparent, and changes in relative sea level were probably more important in controlling the preservation of stratigraphic sequences. Where the non-marine Lower Cretaceous succession is imaged clearly, the stratigraphic similarity between parts of the North Celtic Sea and the Weald and Channel Basins suggests a wider control by relative sea-level fluctuations. However, important variations in seismic facies within the basins indicate localized, dominant tectonic control. The recognition of a very distinctive 'lower' Wealden seismic facies, observed as undulatory (?channelized) and downlapping reflections, is contrasted with either the parallel or synsedimentary fault-dominated 'upper' Wealden facies. These seismic characteristics reflect the previously recognized climatic/tectonic change from Hastings to Weald Clay Group environments. The debate on tectonics versus eustacy is further complicated: palaeoclimate appears to be a third process responsible for stratigraphic variation.  相似文献   

19.
Tracer technology has been used to understand water circulation in marine systems where the tracer dose is commonly injected into the marine waters through controlled experiments, accidental releases or waste discharges. Anthropogenic discharges of 129I have been used to trace water circulation in the Arctic and North Atlantic Ocean. Here, 129I, together with 127I, is utilized as a tracer of water pathways and circulation in the Baltic Sea through collection of seawater depth profiles. The results indicate the presence of 129I signatures which are distinct for each water mass and provide evidence for: (1) inflow water masses through the Drogden Sill that may reach as far as the SW of the Arkona Sea, (2) a portion of North Atlantic water in the bottom of Arkona basin, (3) cyclonic upwelling which breaks through the halocline in a pattern similar to the Baltic haline conveyor belt and (4) more influx of fresher water from the Gulf of Finland and Bothnian Sea in August relative to April. These findings provide advances in labeling and understanding water pathways in the Baltic Sea.  相似文献   

20.
Phytoplankton plays a dominant role in shelf biogeochemistry by producing the major part of organic matter. Part of the organic matter will reach the sediment where diagenetic processes like denitrification, apatite formation or burial will remove nutrients from the biogeochemical cycle. In this article current knowledge on the decadal plankton variability in the North Sea is summarized and possible implications of these changes for the biogeochemistry of the North Sea are discussed. Most of the observed interdecadal dynamics seem to be linked to large-scale oceanographic and atmospheric processes. Prominent changes in the North Sea ecosystem have taken place around 1979 and 1988. In general, the phytoplankton color (CPRS indicator of phytoplankton biomass) reached minimum values during the end of the 1970s and has increased especially since the mid 1980s. Changes with a similar timing have been identified in many time series from the North Sea through the entire ecosystem and are sometimes referred to as regime shifts. It is suggested that the impact of global change on the local biogeochemistry is largely driven by the phyto- and zooplankton dynamics during spring and early summer. At that time the extent of zooplankton–phytoplankton interaction either allows that a large part of the new production is settling to the sediment, or that a significant part of the new production including the fixed nutrients is kept within the pelagic system. The origin of the extent of the phytoplankton–zooplankton interaction in spring is probably set in the previous autumn and winter. In coastal areas, both large-scale atmospheric and oceanographic changes as well as anthropogenic factors influence the long-term dynamics. Due to eutrophication, local primary production nowadays still is up to five times higher than during pre-industrial conditions, despite a decreasing trend. Recently, introduced species have strengthened the filter feeder component of coastal ecosystems. Especially in shallow coastal seas like the Wadden Sea, this will enhance particle retention, shift organic matter degradation to the benthic compartment and enhance nutrient removal from the biogeochemical cycle by denitrification or apatite formation.  相似文献   

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