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1.
Four morphotypes of structurally preserved, filamentous fossil bacteria have been discovered in petrographic thin sections of laminated, carbonaceous cherts from the 3500 Ma-old Warrawoona Group of northwestern Australia. These tubular and septate microfossils are interpreted here as being syngenetic with Warrawoona sedimentation; as such, they are apparently the oldest such fossils now known in the geological record. The diversity of this assemblage, and the evident complexity of its individual components, suggest that the beginnings of life on Earth may have appreciably pre-dated the deposition of the Warrawoona sediments. 相似文献
2.
The continental terrace of Israel consists of Nile-derived sediments. They are classified into three major groups, according to their structures: (1) irregularly to wavy laminated, coarse-grained sediments (quartz and skeletal debris) of the flat outer shelf and upper bend of the slope (10–20% of the bulk) which are influenced by currents. These sediments are bioturbated to various degrees. Smectitic silty clays (80–90%) form two structural groups: (2) laminated, turbiditic sediments which accumulate on the slope, particularly in the canyons of the northern slope. Irregular, wavy, thickly laminated, coarse-grained sediments of the upper slope and canyon heads merge downslope with parallel, thinly laminated, fine-grained sediments. Toward the foot of the slope and on the adjacent deep-sea floor lamination becomes indistinct and the sediment is visually homogeneous. (3) Slump-generated mud lumps of various size which accumulate on the lower slope and along the transport axes of the canyons. These are the most visible evidence for large-scale slumping mass movement. Transportational and depositional processes are far more intensive over the steep northern continental slope of Israel, and especially in its canyons than over the gentle southern slope. Very stiff overconsolidated sediments unconformably overlain by the ubiquitous recent silty-clayey sediment were cored on steep sections of the middle continental slope and along the canyon walls. Their preconsolidation stress values suggest that these sections were formerly overlain by more than 40 m of sediment and now are exposed by slumping. The downsliding slabs usually disintegrated into small fragments although several huge fragments could be identified along the canyon axes. 相似文献
3.
Lower Pleistocene sediments recovered in boreholes from the Aberdeen Ground Formation in the central North Sea indicate that the unit was deposited in a delta front to prodelta/shallow, open shelf marine setting. Possible estuarine and clastic nearshore marine deposits have been identified on the western margin of the basin. The delta front sediments consist of interbedded, structureless to laminated sands and muds with organic debris, ferruginous nodules and common soft sediment deformation structures. Sporadic rippled and graded beds, basal scours to beds and starved ripples suggest periodic wave–current reworking. Prodelta/shelf marine sediments are predominantly argillaceous with only occasional thin sand beds and rare phosphatic bands. One exceptionally thick sand body or submarine channel-fill although this remains uncertain. The estuarine/clastic nearshore marine sediments include coarse channel-lag deposits and rippled and laminated subtidal sands. A rich microfossil assemblage recovered from the prodelta/shelf marine sequence indicates that deposition occurred under fluctuating climatic conditions. 相似文献
4.
Sandy hyperpycnal flows and their deposits, hyperpycnites, have been documented in modern environments and, more recently, in Cretaceous and Tertiary strata; they may be more common in the rock record, and within petroleum reservoirs, than has been previously thought. Muddy hyperpycnites also occur within the rock record, but these are more difficult to document because of their finer‐grained nature and lack of common sedimentary structures. This paper documents the presence of submarine slope mudstone and siltstone hyperpycnites (and muddy turbidites) in the delta‐fed, Upper Cretaceous Lewis Shale of Wyoming; based on field measurements, analyses of rock slabs and thin sections, and laser grain‐size distributions. Four lithofacies comprise laminated and thin‐bedded mudstones that are associated with levéed channel sandstones: (L1) grey, laminated, graded mudstone with thin siltstone and sandstone interbeds; (L2) dark grey to tan, laminated mudstone with very thin siltstone and sandstone stringers; (L3) light grey, laminated siltstones; and (L4) laminated mudstones and siltstones with thin sandstone interbeds. Two styles of mudstone grain‐size grading have been documented. The first type is an upward‐fining interval that typically ranges in thickness from 2·5 to 5 cm. The second type is a couplet of a lower, upward‐coarsening interval and an upper, upward‐fining interval (sometimes separated by a micro‐erosion surface) which, combined, are about 3·8 cm thick. Both individual laminae and groups of laminae spaced millimetres apart exhibit these two grain‐size trends. Although sedimentary structures indicative of traction‐plus‐fallout sedimentary processes associated with sandier hyperpycnites are generally absent in these muddy sediments, the size grading patterns are similar to those postulated in the literature for sandy hyperpycnites. Thus, the combined upward‐coarsening, then upward‐fining couplets are interpreted to be the result of a progressive increase in river discharge during waxing and peak flood stage (upward increase in grain‐size), followed by waning flow after the flood begins to abate (upward decrease in grain‐size). The micro‐erosion surface that sometimes divides the two parts of the size‐graded couplet resulted from waxing flows of sufficiently high velocity to erode the sediment previously deposited by the same flow. Individual laminae sets which only exhibit upward‐fining trends could be either the result of waning flow deposition from either dilute turbidity currents or from hyperpycnal flows. The occurrence of these sets with the size‐graded couplets suggests that they are associated with hyperpycnal processes. 相似文献
5.
青藏高原北部可可西里库赛湖年纹层微区分析及形成机理 总被引：2，自引：0，他引：2
湖泊年纹层是进行高分辨率古气候环境研究的重要载体之一,其形成机理的研究能够为高分辨率古气候环境信息的提取提供重要的依据。本文以青藏高原北部可可西里库赛湖沉积的年纹层为研究对象,通过纹层薄片显微镜观察,以及纹层的扫描电镜、X衍射和同步辐射X射线荧光等微区分析,对库赛湖沉积年纹层的形态、沉积和成分特征进行了研究,以探讨库赛湖年纹层形成过程和机理。结果表明:年纹层层偶由深浅相间的微层组成,深色层主要由灰褐色—黑褐色的粗颗粒物质组成,磨圆中等、分选性差,矿物以石英、长石、白云母、黏土矿物等为主,其中石英含量占73%左右,且具有明显的风力搬运特征;浅色层呈灰白色,矿物颗粒较细,除石英、长石、白云母、黏土外,还有自生的文石,同时浅色层中含有大量的枝角类碎片和半月形介形类生物壳体。研究认为,库赛湖冬季温度低、风力强劲,风的机械搬运作用使大量的陆源物质在冰面堆积,等到春季湖泊开封,冰面上粗颗粒物质沉积到湖底形成库赛湖年纹层的深色层(粗颗粒层);夏季温度升高,冰雪融化,降水增加,河流搬运的陆源粗颗粒物质由于重力作用先在湖泊边缘沉积,而黏土矿物等细颗粒物质则在湖泊中心沉积,同时夏季湖水温度升高,蒸发作用加强,生物活动增强,湖泊自身的生物、化学作用加强,从而形成以细碎屑矿物、生物残体、自生碳酸盐沉积为主的浅色层(细颗粒层)。因此,库赛湖的年纹层层偶是由冬季冰面风成物质形成的粗颗粒深色层(冰融化后,风成物质沉降至湖底堆积)和夏季沉积的细颗粒浅色层两者交替而形成的。 相似文献
6.
Improved methods for sampling, photographing and varve-counting of varved lake sediments 总被引：14，自引：0，他引：14
INGEMAR RENBERG 《Boreas: An International Journal of Quaternary Research》1981,10(3):255-258
An improved crust-freeze sampler for taking undisturbed cores of the surface sediments from ice-covered lakes is described together with a technique for subsampling the frozen sediment. Hints are given on how photography and varve-counting in frozen and in fresh cores of varved lake sediments can be made easier, and on how to make thin sections of sediments for examination under the light microscope 相似文献
7.
纹层计年与137Cs、210Pb法对比研究东北二龙湾玛珥湖现代沉积速率 总被引：1，自引：0，他引：1
通过对东北二龙湾玛珥湖顶部无扰动岩心显微研究,证明此岩心发育有良好的年纹层。据精确统计,0~5.5 cm间为36个年纹层,纹层计年的误差为4％~7％,年纹层厚度为1.1~2 mm不等,平均沉积速率为1.53 mm/a,5.5 cm处对应于1965年。而二龙湾沉积物（从6.5 cm到5.5 cm)岩心的137Cs比活度值急剧增加,从（4.67±0.29） dpm/g增加到（12.06±0.47） dpm/g,在5.5 cm处有一个较为明显的蓄积峰值,这一峰值被确认对应为1963年全球137Cs散落的高峰期。另外据210Pbex比活度CIC模式,5.5 cm处约为1962年,这和137Cs比活度曲线的1963年时标相一致。印证了纹层计年的精确性,完全可以建立高分辨率时间序列。 相似文献
8.
Storm-influenced siliciclastic and carbonate ramp deposits, the Lower Ordovician Dumugol Formation, South Korea 总被引：4，自引：0，他引：4
The Dumugol Formation (Lower Ordovician) in the southern part of the Baegunsan syncline, South Korea, contains mixed siliciclastic and carbonate ramp deposits. The ramp sediments were frequently influenced by storm events resulting in tempestites of sandstone-mudstone couplets, bioclastic grainstones to packstones, flat-pebble conglomerates, a skeletal lag layer and laminated calcisiltites. All tempestites are characterized by an erosive to sharp base, poor grading and a transitional upper boundary. The difference in lithology of tempestites appears to have been controlled by the nature of substrates and by proximality. For example, laminated calcisiltites have developed on the shallow carbonate ramp, flat-pebble conglomerates are closely associated with nodular limestones on shallow and deep ramps, and thin skeletal lag layers from fossiliferous argillaceous sediments formed in a basinal setting. The stratigraphic succession of the Dumugol Formation represents an initial transgression followed by a regression. The vertical facies change records the transition from a shallow siliciclastic ramp to a deep carbonate ramp, to a basin, shallowing to a deep carbonate ramp, and to a shallow carbonate ramp. Storm effects are mostly well preserved in shallow to deep ramp deposits. 相似文献
9.
鄂尔多斯盆地中部奥陶系马家沟组赋存有丰富的天然气资源,前人研究多集中于顶部与风化壳相关的储集层。文中基于岩心、薄片及阴极发光分析,将鄂尔多斯盆地中部奥陶系马五盐下碳酸盐岩-蒸发岩划分为10种岩石类型。根据各岩类的宏观、微观特征以及它们在纵横向上的组合与分布特点,利用岩石类型组合的方法,将研究区划分为局限-蒸发潟湖、台内滩、滩间海、微生物丘和台坪5种沉积环境。根据各亚段岩石类型发育的差异性及统计结果发现,研究区马五盐下具有蒸发岩与碳酸盐岩间互的旋回性沉积演化与海平面升降特征,每个亚段都代表一次海侵或海退的旋回沉积。其中,马五6、马五8和马五10亚段为海退期沉积,以纹层状云质膏岩、泥晶云岩构成的局限-蒸发潟湖沉积为主,蒸发岩矿物含量高,反映沉积环境相对闭塞、能量较低且盐度较高;马五7和马五9亚段为海进期沉积,以相对高能的台内滩或微生物丘沉积为主,并与相邻的局限-蒸发潟湖和台坪沉积构成较完整的向上变浅米级沉积旋回,表明该阶段水体循环相对更好,整体沉积环境开阔且能量较高。 相似文献
10.
Studies on the genesis of subaerial debris flows and associated deposits are relatively rare in the literature, especially in an ice-marginal context of moraine formation. The present contribution reports results from both the macro- and micro-scales of a subaerial depositional setting in order to contribute to closing this gap. At the macroscale, alternating loose, stratified, clast- and matrix-supported diamicts and finely laminated sand units indicate deposition of debris flows and fluvial units in a subaerial, ice-marginal setting that were stacked up to form a terrestrial ice-contact fan. Macroscale and micromorphological analyses show that this fan displays evidence of a three-phased formation: (a) overriding and glaciotectonisation of pre-existing sediments followed by retreat and burial of this core by (b) ice-contact fan deposition dominated by water-rich fluvial deposition with relatively little debris flow activity and (c) a switch to a gravitational sedimentation style with dominantly debris flow deposition and fewer and thinner fluvial units. Thin sections of both the diamict and laminated sand units show evidence of deposition of a mud and fine sand-rich slurry being expelled from the tops of advancing mass flows. Water-rich fine-grained slurries appear to have been progressively overridden and deformed in response to ductile shear occurring at the base of individual flows. Liquefaction and remobilisation of sand within laminated deposits occurred during such basal shear events, resulting in the injection of liquefied sediments into variably deformed laminated sands and clays. Deformation is more likely to have taken place through internal movement of the sediment due to changing porewater conditions and loading upon emplacement. Our approach confirms previous results that highlight the possibilities of increasing the accuracy of sedimentological investigations through combined sedimentological analyses at varying scales. 相似文献
11.
北京十三陵中元古界蓟县系雾迷山组原地风暴沉积的砾屑体 总被引：1，自引：1，他引：1
研究区雾迷山组的层状藻叠层白云岩中存在一种属原地风暴成因的砾屑透镜体?砾屑体的底部为略下切的侵蚀面,顶为上凸形?砾屑呈放射状或叠瓦状排列,无磨圆作用?其形成过程是:在风暴初期,风暴浪对海底沉积物冲击?掀起?破碎,而后迅速原地堆积而成?风暴衰减后,正常沉积顺应砾屑体的顶面形态? 相似文献
12.
Michael A. Blazevic Matthew E. Kirby Adam D. Woods Brandon L. Browne David D. Bowman 《Sedimentary Geology》2009,219(1-4):151-168
A combined sedimentological and high-resolution petrographic analysis was conducted on a glacial-age (20,000–65,000 cal yr BP) sediment core from Baldwin Lake, Southern California. The results of this research represent the most complete glacial-age, terrestrial climate record from Southern California to date. These results are used to characterize the different sediment types and to investigate the difference in depositional processes and environments between the core's three predominant sediment types: massive, semi-laminated, and laminated sediments. Massive sediments are commonly associated with a blocky texture and/or desiccation cracks, are organic-poor, have high magnetic susceptibility values, and are coarser-grained. Thin-sections from massive sediments reveal a homogenous sediment fabric. Sub-centimeter-scale laminated and centimeter-scale semi-laminated sediments are generally organic-rich, have low magnetic susceptibility values, and are finer grained. Thin-sections from laminated and semi-laminated sediments reveal diffuse sub-millimeter- to millimeter-scale laminae. This combination of sedimentological and high-resolution petrographic data enabled us to characterize four sediment facies, each related to specific depositional processes and environments: (1) a playa lake; (2) a perennial shallow lake; (3) an intermediate lake with variable lake level; and, (4) a perennial deep lake. At centennial-to millennial-timescales, lower lake levels are represented by deposition of massive to semi-laminated sediments in a playa to a perennial shallow lake environment. At similar timescales, higher lake levels are recorded by semi-laminated to laminated sediments deposited in an intermediate lake to a perennial deep lake environment. These results provide an additional sedimentological study for comparison to similar arid environment basins, and for comparison to existing regional paleoclimatic reconstructions. 相似文献
13.
三塘湖盆地二叠系芦草沟组喷爆岩岩石学、矿物学特征及相关问题探讨 总被引：1，自引：0，他引：1
在对新疆北东部三塘湖盆地二叠系芦草沟组黑色细粒岩系进行研究时发现,这套长期被当作由黑色泥岩、凝灰岩和碳酸盐岩组成的岩系里还发育一套既不同于陆源碎屑、内碎屑沉积岩,也不同于热水沉积岩(喷流岩)的岩石,认为是一套以夹层形式发育在纹层状泥/页岩中,由气、液、固三相共存的深源岩浆—热液物质流体上涌进入湖(海)底喷流通道,由喷口喷出后与热液流体或与湖(海)水混合沉积形成的沉积岩—喷爆岩。喷爆岩呈薄层—纹层状展布,矿物组成种类单一,以不稳定、次稳定矿物为主。晶质颗粒碎屑或团块均呈大小混杂、形态各异的棱角状,分选差,分布无规律。基于大量岩芯、岩石薄片观察,结合电子探针及相关数据,以构成岩石碎屑颗粒的主要组成矿物为依据,将喷爆岩分为方解石喷爆岩、白云石喷爆岩、透辉石喷爆岩及长英质喷爆岩四类,并详细论述了各类岩石学、矿物学特征。研究结果显示构成喷爆岩的碎屑颗粒不再是传统认识的来自周缘母岩风化搬运或热液沉淀,而是在陆内裂谷欠补偿湖盆背景下、源自地球内部不同深度、不同性质的岩浆—热液物质流体。在此基础上,对喷爆岩与碎屑沉积岩、火山碎屑岩及喷流岩区别进行讨论,认为喷爆岩分别在矿物组成、物质来源、分布规模、形成方式等方面有别于上述三者。 相似文献
14.
通过野外露头详细观察、薄片鉴定、X射线衍射分析、微量元素分析等技术,对大河沿地区塔尔朗组细粒沉积岩矿物成分、沉积构造、岩性岩相类型及沉积环境进行研究。结果表明:塔尔朗组细粒沉积岩矿物成分以石英和方解石为主,含少量长石及黏土矿物;沉积构造类型包括较强水动力下的粒序层理、小型交错层理、脉状层理以及静水环境下的纹层状构造;以颜色、矿物成分、沉积构造等因素为依据将细粒沉积岩划分为5种岩相,包括灰黑色薄层状混合细粒岩相、深黑色页状黏土岩相、灰黑色纹层状混合细粒岩相、灰色薄层状粉砂岩相、灰白色页状灰岩相;岩石类型包括碳酸盐岩类、细粒长英沉积岩类、细粒混合沉积岩类3种岩石类型。塔尔朗组细粒沉积岩沉积期温暖湿润,整体上属于还原的半咸水-咸水湖盆的产物。 相似文献
15.
Andrew R. Farrant Peter M. Hopson James B. Riding 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(5):888-905
Recent geological mapping on the Isle of Wight by the British Geological Survey has shown the ‘Plateau Gravel’ to be a mixture of fluvial, solifluction, pedogenic and marine deposits ranging from pre-Anglian to Holocene age. As part of the resurvey of the island, several new exposures of the ‘Plateau Gravel’ between Newport and Downend were examined. A working gravel pit on St George's Down, near Newport, revealed a succession of flint gravels with an inter-bedded sequence of laminated silts. An upper in situ succession of pre-Anglian fluvial gravels caps the plateau, but a second, probably younger suite of gravel-rich sediments is exposed in a quarry on a topographically lower spur. These overlie in situ Clay-with-flints resting on Upper Cretaceous Chalk. These lower sediments are well exposed and display a complex stratigraphy. They consist predominantly of flint gravel, but include a dipping succession of laminated silts and palaeosols preserved in a hollow or small channel feature, intercalated between two distinct soliflucted cold-stage gravel sheets. Palynological and pedological evidence analysis suggests that these laminated silts and sands were deposited under a temperate climate but with frequent episodes of disruption caused by mass-movement and possibly freeze-thaw. The age of these laminated sediments are not known with any certainty but are likely to date to a temperate interval within the Late Pleistocene. The top of the laminated unit is cut by a heavily cryoturbated horizon presumed to be of Devensian age. 相似文献
16.
鄂尔多斯盆地东南部山2段是该盆地重要的天然气富集层位。通过重矿物分布、岩屑组分、砂岩岩屑类型及阴极发光特征分析山2段沉积物源体系,经研究认为盆地东南部山2段沉积同时受南、北部物源供源。山2段为曲流河三角洲前缘沉积亚相,碎屑颗粒分选中等偏好、磨圆较好、颗粒之间接触紧密,沉积构造主要为板、槽状交错层理、平行层理及浪成交错层理。本区山2段沉积物以跳跃组分和悬浮组分为主,水下分流河道微相粒度概率曲线呈现三段式和四段式;河口坝微相分选较好、粒度概率曲线形态为两段式和三段式。研究区北部、南部及中部志丹、甘泉等地区砂体发育较厚,剖面上河道砂体呈不对称式相互叠置,水动力条件中等-较强。通过物源体系重建、沉积特征分析与薄片特征鉴定,建立了鄂尔多斯盆地东南部山2段双物源曲流河三角洲沉积模式。该研究明确了盆地东南部山2段物源方向,明晰了山2段沉积特征,创建了典型曲流河三角洲沉积模式,为进一步勘探开发提供了理论支持。 相似文献
17.
A. H. M. Ahmad A. F. Khan S. M. Wasim 《Journal of the Geological Society of India》2013,82(2):181-189
The study deals with the depositional environment of Jumara Dome sediments. The Jumara Dome is an important outcrop of Bathonian to Oxfordian sediments amongst the Kachchh Mainland exposures. On the basis of facies analysis three associations have been documented, namely, G-1 consisting of low energy facies comprising of cross-bedded sandstone, massive sandstone, grey shale and thin bedded sandstone, bioclastic — lithoclastic grainstone, bioclastic — lithoclastic packstone, microbioclastic packstone/wackestone, bioturbated laminated wackestone to mudstone and pelagic lime mudstone; G-II consisting of moderate energy facies comprising of laminated sandstone and grapestone or agglutinated grainstone; G-III consisting of high energy facies comprising of interbedded gypsiferous shale and sandstone/siltstone, oolitic grainstone to conglomerate and bioclastic grainstone. The facies associations reflect an ideal shallowing upward sequence representing slope, bioclast bar, lagoon and inner shelf. Presence of wide range of facies indicates that the rocks of the studied area were deposited during the fluctuating sea level, interrupted by the storms, in the shallow marine environment. 相似文献
18.
B. CHARLOTTE SCHREIBER GERALD M. FRIEDMAN† ARVEDO DECIMA‡ EDWARD SCHREIBER 《Sedimentology》1976,23(6):729-760
In Sicily, Messinian evaporitic sedimentary deposits are developed under a wide variety of hypersaline conditions and in environments ranging from continental margin (subaerial), to basin-margin supratidal, to intertidal, to subtidal and out into the hypersaline basin proper. The actual water depth at the time of deposition is indeterminate; however, relative terms such as ‘wave base’ and ‘photic zone’ are utilized. The inter-fingering relationships of specific evaporitic facies having clear and recognizable physical characteristics are presented. These include sub-aerial deposits of nodular calcium sulphate formed displacively within clastic sediments; gypsiferous rudites, arenites and arenitic marls, all of which are reworked sediments and are mixed in varying degrees with other clastic materials (subaerial, supratidal, and intertidal to deep basinal deposits). Laminated calcium sulphate alternating with very thin carbonate interlaminae and having two different aspects; one being even and continuous and the other of a wavy, irregular appearance (subtidal, intertidal, and supratidal deposits). Nodular calcium sulphate beds, usually associated with wavy, irregular laminated beds (supratidal, sabkha deposits); very coarsely crystalline gypsum beds (selenite), associated with more even, laminated beds (subaqueous, intertidal to subtidal deposits); wavy anastomozing gypsum beds, composed of very fine, often broken crystals (subaqueous, current-swept deposits); halite having hopper and chevron structures (supratidal to intertidal); and halite, potash salts, etc. having continuous laminated structure (subaqueous, possibly basinal). Evidence for diagenetic changes is observed in the calcium sulphate deposits which apparently formed by tectonic stress and also by migrating hypersaline waters. These observations suggest that the common, massive form of alabastrine gypsum (or anhydrite, in the subsurface) may not always be ascribed to original depositional features, to syndiagenesis or to early diagenesis but may be the result of late diagenesis. 相似文献
19.
The use of petrographic thin sections to examine archaeological sediments has centered on the study of detrital and chemical components of the material. There has been relatively little effort made to study botanical remains—particularly charcoal—with this technique. This paper illustrates that millimeter-size or even smaller fragments examined in undisturbed, artificially indurated samples, which normally would escape collection with standard flotation and sieving techniques, can furnish significant paleobotanical information about the types of vegetal matter found in a site. Samples from cave sediments in Israel and an open-air site in Canada are presented. © 1994 John Wiley & Sons, Inc. 相似文献
20.
EILIV LARSEN STEINAR GULLIKSEN STEIN-ERIK LAURITZEN ROLF LIE REIDAR LØVLIE JAN MANGERUD 《Boreas: An International Journal of Quaternary Research》1987,16(3):267-292
Skjonghclleren is a marine-cut cave with 15–20. m thick pre-Holocene sediments. Corings and excavations reveal three beds of extremely fine-grained, laminated sediments alternating with blocky sediments. The laminated beds are interpreted as glaciolacustrine sediments deposited subglacially at times when ice sheets covered the area, suggesting at least three glaciations after the cave was formed. The blocky/diamictic sediments were formed by frost-shattered blocks from the roof of the cave during ice-free periods, and mixing with the fines through slow mass movements along the floor of the cave. In the diamictic sediment beneath the uppermost laminated bed, almost 7,000 bone and teeth fragments of birds, mammals and fish were found. Birds dominated, with little auk and brunnich's guillemot as the most frequently occurring species. Arctic fox was the dominating mammal. During climatic optimum of the interstadial, conditions seem to have been similar to present-day coastal Finnmark, with North Atlantic warm water entering the Norwegian Sea. Two radiocarbon dates on bones and three Uranium series dates on speleothems from this bed all cluster around 30,000 B.P., i.e., the end of the Ålesund interstadial. Above the uppermost laminated bed, bone fragments of birds, fish and mammals, deposited between c . 12,000 and c . 10,000 B.P., were found. Little auk dominate. The occurrence of squirrel is worth noting since it is limited mainly to areas with coniferous forest today. The beds below the 30,000B.P. bed are poorly dated or undated, but it is tentatively concluded that the entire sediment sequence was deposited during the Weichselian stage. It seems that the cave was formed at a high relative sea-level stand sometime during the Early Weichsclian. Two recorded palaeomagnetic excursions seem to correlate with the Laschamp/Olby and the Lake Mungo events, respectively. 相似文献