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The faunal composition and temporal species succession dynamics during the Holocene are poorly known in Norway, and interpretations are often biased because of the potential overrepresentation of game species in the archaeological finds. Pitfall traps in limestone caves represent less biased long-term records of fauna, often being excellently preserved for thousands of years and thus providing an opportunity for reconstruction of the postglacial distribution history. We excavated fossiliferous sediments at the bottom of a 40-m entrance shaft, functioning as a pitfall trap, in the Sirijorda Cave, northern Norway, comprising 3467 identified vertebrate bone fragments. Radiocarbon-dating of mammalian bones at stratigraphic levels in excavated trenches was used for calibrating the time scale during the last 8000 14C years BP, with a reconstruction of local vegetation history from a pollen profile in the cave deposits. At least 20 species were identified: one frog, two birds (plus 1-2 to genus level) and 17 mammals. Most of the species appeared more or less continuously during the covered time periods of the Atlantic, Subboreal and Subatlantic chronozones. With the exception of one species, Sorex isodon, which seems to have disappeared during the past 2000 years, all the registered species in the time profile are present in the area today. The possible immigration routes and time periods for (re)colonization of the recorded species are discussed.  相似文献   

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The Coniacian 3rd-order sequence in the Iberian Basin is represented by a carbonate ramp-like open platform. The biofacies is mainly dominated by nekto-benthic (such as ammonites) and benthic organisms (such as bivalves, mainly rudists) with scarce solitary corals (hermatypics are absent), showing major differences among the Transgressive System Tract (TST) and Highstand Normal Regression (HNR). During the TST, platform environments were dominated by Pycnodonte, other oysters and molluscs (with only subordinate rudists) and ammonites, which were represented by ornamented platycones (Tissotioides and Prionocycloceras), and by smooth oxycones (Tissotia and Hemitissotia). During the HNR, shallow water depositional areas were occupied by rudist-dominated associations. Storm- and wind-induced currents and waves acting on these associations produced large amounts of loose bioclastic debris that covered outer platform areas. This facies belt graded landwards into protected, lower-energy settings (inner platform, lagoon and littoral environments). Rudist biostromes were preserved in seaward areas of these protected shallow environments of overall moderate to low hydrodynamic gradient, which was punctuated by storms. In this environment and landwards, large areas of marly substrate favoured the presence of gastropods, other bivalves, echinoderms, benthic foraminifera and solitary corals. Because of the input of siliciclastics and, probably, the lack of nutrients in suspension, the establishment of rudist communities was difficult in more landward areas of the lagoon and in tidal environments. This heterozoan carbonate factory was thus controlled by warm-water conditions and high energy levels, which were responsible for high-nutrient contents in suspension.  相似文献   

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The preservation process of faunal remains from the Middle Paleolithic levels of Kůlna Cave was studied within a taphonomic and palaeodietary framework. A visual examination of bones and teeth showed that they display a wide variety of colors. Chemical analyses (C, N, Fe, Mn) and a combination of analytical techniques, such as Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), and electron spin resonance (ESR) spectrometry, were conducted on 13 fossil remains. The crystallinity indexes, IR‐SF, XRD‐CI, XRD‐L200, the IR area band (Amide I), and the ESR analyses showed that the bones were not burned at a temperature higher than 200°C. This implies that the bone remains were not used as fuel by Neanderthals at Kůlna Cave. Coloring in these bones is largely due to the presence of Mn and Fe. © 2006 Wiley Periodicals, Inc.  相似文献   

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Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2 °C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus, appears to have formed during the Ipswichian (MIS 5e). This evidence is compared with other important sites of late Middle Pleistocene age in Britain and elsewhere on the continent and the importance of a multidisciplinary approach is stressed.  相似文献   

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A sediment core spanning  7000 cal yr BP recovered from Stella Lake, a small sub-alpine lake located in Great Basin National Park, Nevada, was analyzed for subfossil chironomids (non-biting midges), diatoms, and organic content (estimated by loss-on-ignition (LOI)). Subfossil chironomid analysis indicates that Stella Lake was characterized by a warm, middle Holocene, followed by a cool “Neoglacial” period, with the last two millennia characterized by a return to warmer conditions. Throughout the majority of the core the Stella Lake diatom-community composition is dominated by small, periphytic taxa which are suggestive of shallow, cool, alkaline, oligotrophic waters with extensive seasonal ice cover. A reconstruction of mean July air temperature (MJAT) was developed by applying a midge-based inference model for MJAT (two-component WA-PLS) consisting of 79 lakes and 54 midge taxa (rjack2 = 0.55, RMSEP = 0.9°C). Comparison of the chironomid-inferred temperature record to existing regional paleoclimate reconstructions suggests that the midge-inferred temperatures correspond well to regional patterns. This multi-proxy record provides valuable insight into regional Holocene climate and environmental conditions by providing a quantitative reconstruction of peak Holocene warmth and aquatic ecosystem response to these changes in the Great Basin, a region projected to experience increased aridity and higher temperatures.  相似文献   

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This paper deals with the chronology and the possible correlations among levels of different excavated areas in the Pleistocene vertebrate-bearing deposits at the large San Teodoro Cave (North-Eastern Sicily). Two trenches have been excavated along the eastern side of the cave, located at a distance from the entrance, respectively, of 8 m (α trench) and 28 m (β trench) and at different depths. Lithological features, biometrical data from small mammals and ecological data from molluscs point to similar environmental conditions for the α trench deposits and those located along the eastern wall of the cave in the eastern part of the β trench. The same evidence, and the taphonomic features of large mammals, points to different environmental conditions and perhaps to different ages for the deposits located in the western part of the β trench. The survival of elephants in Sicily up to 32,000 years ago is a new significant result of the 230Th/234U dating carried out from a concretionary stratum from the β trench and represents the youngest elephant survival in the western Mediterranean islands.  相似文献   

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Abundant and regionally unique dolostone lithoclast breccias occur throughout the shallow-marine, Lower to Middle Ordovician Pogonip Group in the Nopah Range and adjacent ranges in eastern California and southern Nevada. Breccia bodies display sharply cross-cutting relationships with host dolostone bedrock stratigraphy. They also show stratigraphic variability in size, shape and dolostone clast composition, but similarity in breccia matrix composition and framework texture and fabric. These characteristics are consistent with a palaeokarst origin. Upsection changes in breccia clast lithology as well as multiple occurrences of associated quartz sand-filled grikes (solution-widened fissures) indicate multiple episodes of carbonate platform exposure and karstification. Repeated karstification is also indicated by stratiform bodies of quartz sand and thin terra rossa palaeosols that locally truncate breccias and grike systems, thus bracketing karstified exposure surfaces. Facies successions and stacking patterns between recognized exposure surfaces are developed as transgressive–regressive cycles and thus show depositional sequence architecture. Hence, these breccias and other associated palaeokarst features are related to a succession of disconformities that provide a sequence-stratigraphic framework for assessing Ordovician relative sea-level history of the south-western Cordilleran margin of Laurentia.  相似文献   

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渤海湾盆地大歧口凹陷断裂系统与陆内拉分断陷   总被引:2,自引:0,他引:2       下载免费PDF全文
大歧口凹陷位于渤海湾盆地中部, 是在中生代构造基础上形成的新生代构造单元, 是我国最具勘探价值的大型富油气凹陷。前人对大歧口凹陷盆地结构、断裂构造、演化特征方面有了较为深入的研究, 但对凹陷内主要断裂的分段活动特征、构造迁移, 以及新生代基底走滑—盖层伸展构造体系的深浅部耦合关系并未进行全面细致的研究, 这在一定程度上限制了对凹陷内断裂活动特征、构造成因机制、断裂拓展演化规律详细的构造分析。本文在精细解释、深入分析地球物理资料的基础上, 开展了详细的构造研究。研究表明, 歧口凹陷充填格局主控断裂为东西走向, 近南北向的沿岸变换带是主变换带; 新生代的构造体系受北东向右行基底走滑断裂和东西向的盖层伸展构造的双重控制, 并形成三级断阶带。基底—盖层断裂的耦合方式主要有两种: 一是在盖层中形成强制性褶皱传递基底走滑, 二是在盖层中形成一系列雁列式正断层。欧亚板块下的地幔物质在印度板块和太平洋板块两大构造系统的共同作用下, 自南向北迁移并上涌, 导致歧口凹陷主要断裂的规模、活动期以及断裂活动由南西向北东迁移、演化。  相似文献   

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The Great Lakes Basin is a large, complex, diverse system of highly connected social, biological, and physical components. Its long history has culminated today in a variety of environmental, economic, and social problems and efforts to solve them. The idea of sustainability — meeting societal needs and desires without impairing the ability to meet them in the future — is gaining widespread acceptance as an appropriate goal for management of such systems. This paper shows that nonequilibrium systems theories dealing with chaotic and self-organizing behavior can provide some insight into the dynamics of complex sociobiophysical systems such as the Great Lakes Basin, and their prospects for sustainability. A methodology for describing and analyzing sociobiophysical systems is outlined, and used to focus on change, critical variables and transformations in the history of the Great Lakes Basin. Nonequilibrium systems theories are used to develop links between system characteristics and sustainability, ecosystem redevelopment, impact assessment and monitoring, and management of Great Lakes resources. An indicative framework for monitoring change, restructuring, and transformation by assessing the nature of change, evaluating system responsiveness, and monitoring the Basin sociobiophysical system, is presented.  相似文献   

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This article addresses the taphonomic issues surrounding artifact-bear associations in Yarimburgaz Cave, northwestern Turkey. Our purpose is to evaluate the circumstances of bone assemblage formation in the Middle Pleistocene deposits of the cave, identifying the agencies responsible for the accumulations and the causes of bone damage before and following deposition. Pleistocene species representation, bone damage, body part representation, and mortality data indicate that cave bear remains in Yarimburgaz are unrelated to hominid use of the same site. None of the observations on the cave bear remains contradicts the expectations developed from modern wildlife accounts of modern bear behavior; these accumulations resulted from mortality normally associated with hibernation over many generations of den use. Nonursid carnivores also played roles in bone collection and/or modification. We conclude that at least three distinct biological processes contributed to the formation of the Middle Pleistocene faunas: hibernating bears, bone-collecting carnivores such as wolves, and hominids in descending order of importance. The Yarimburgaz faunas represent palimpsests or overlays of many short-term depositional events, the close spatial associations of which are explained by slow or uneven sedimentation rates inside the cave. Although occupations by hominids appear to have been ephemeral in nature, hominids ultimately discarded nearly 1700 stone artifacts in Yarimburgaz Cave. The hominids did not discard many ungulate bones in the same circumstances. These observations suggest that hominid foraging efforts focused on resources other than large game while at the cave. © 1996 John Wiley & Sons, Inc.  相似文献   

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《Quaternary Science Reviews》2007,26(17-18):2167-2184
The northwestern Great Basin lies in the transition zone between the mesic Pacific Northwest and xeric intermountain West. The paleoenvironmental history based on pollen, macroscopic charcoal, and plant macrofossils from three sites in the northwestern Great Basin was examined to understand the relationships among the modern vegetation, fire disturbance and climate. The vegetation history suggests that steppe and open forest communities were present at high elevations from ca 11,000 to 7000 cal yr BP, and were replaced by forests composed of white fir, western white pine, and whitebark pine in the late Holocene. Over the last 11,000 years, fires were more frequent in mid-elevation forests (10–25 fire episodes/1000 years) and rare in high-elevation forests (2–5 fire episodes/1000 years). Applying modern pollen–climate relationships to the fossil pollen spectra provided a means to interpret past climate changes in this region. In the past 9000 years summer temperatures decreased from 1 to 4 °C, and annual precipitation has increased 7–15%. These results indicate that the millennial-scale climate forcing driving vegetation changes can be quantified within the intermountain West in general and northwestern Great Basin in particular. In addition, fire can be considered an important component of these ecosystems, but it does not appear to be a forcing mechanism for vegetation change at the resolution of these records.  相似文献   

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Late Quaternary environments and biogeography in the Great Basin   总被引:1,自引:0,他引:1  
Plant and animal remains found in packrat (Neotoma spp.) middens and cave fill from the eastern and southern Great Basin region reveal the presence of subalpine conifers and boreal mammals at relatively low elevations during the Late Wisconsin. Limber pine (Pinus flexilis) and bristlecone pine (P. longaeva) were important in the late Pleistocene plant communities throughout this region. Spruce (Picea cf. engelmannii) and common juniper (Juniperus communis) were present in some of the more northerly localities, and Douglas fir (Pseudotsuga menziesii) and white fir (Abies concolor) were present in southern and eastern localities. Single needle pinyon pine (Pinus monophylla), common across this region today, was apparently not present north of the Sheep Range of southern Nevada during the Late Wisconsin. Pikas (Ochotona cf. princeps), small boreal mammals present in only a few Great Basin mountain ranges today, were common throughout the region. Heather voles (Phenacomys cf. intermedius) have been found in two cave fill deposits in Nevada, though they are unknown in the Great Basin today. Limber and bristlecone pines are generally restricted to rocky substrates in modern subalpine habitats in the Great Basin, and this may also have been the case when these plants grew at lower elevations during the Late Wisconsin. Subalpine conifers were present on the rock outcrops sampled by the packrat middens, but shrub communities, perhaps dominated by sagebrush (Artemisia spp.), may have been present on alluvial valley-bottom substrates. Forested habitats would thus have been isolated habitat islands, as they are today. Boreal small mammals, including pikas and heather voles, were able to colonize the Great Basin mountain ranges during the late Pleistocene. We suggest that these mammals were able to survive in the intervening valley-bottoms under a cool-summer climatic regime, and that continuous forest or woodland corridors were not necessary for migration.  相似文献   

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Lithostratigraphical interpretation and 14C dating of adjacent lake-side sedimentary sequences at the Sulivan House lakes, West Falkland, indicate between-site non-synchronous records of Holocene aeolian sand deposition and landscape stability. It is inferred that the sands are associated with deflation of exposed sandy shorelines at times of lower lake levels, whereas stability phases are characterised by peat formation and/or organic matter incorporation into sand horizons at times of ‘normal’ lake levels. The data imply that a cautious approach to interpretation of lake-side sediments may be warranted if the purpose is to use lake-level changes and aeolian — non-aeolian interbeds as proxy indicators of regional climatic signals. © 1998 John Wiley & Sons, Ltd.  相似文献   

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大气降水渗入土壤,穿过围岩,将气候与地表环境信息导入洞穴滴水,最终被洞穴沉积物所记录,因而研究土壤、围岩与洞穴滴水的地球化学组成及3者之间的联系对了解气候和环境信号的传递以及石笋古环境信息的正确解译十分重要。通过对比清江地区和尚洞上覆土壤、围岩与滴水的元素及锶同位素N(87Sr)/N(86Sr)地球化学组成特征,进而调查土壤和围岩对洞穴滴水水化学的影响。结果表明:滴水的n(Mg)/n(Ca)、n(Ba)/n(Ca)、n(Sr)/n(Ca)及N87Sr)/N(86Sr)介于土壤和围岩之间,说明滴水物质组成来自土壤和围岩的混合;滴水的n(S)/n(Ca)大于土壤和围岩,说明有第三端元的混入,可能是大气硫沉降的结果。通过模型计算可知,土壤和围岩对和尚洞滴水各元素组成的贡献并不相同,贡献的相对大小不仅与元素本身的地球化学性质有关,而且随气候和环境而发生变化。  相似文献   

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广西百色盆地是我国南方最早发现和报道手斧的区域。狭义上的百色盆地位于右江干流的河谷地带,而广义上的百色盆地还包括了右江支流澄碧河流域的一部分(即澄碧河下游的澄碧河库区)。近期,由多家单位组成的联合科考队在澄碧河库区开展了野外调查工作,目前已在澄碧河第4级阶地上发现旧石器时代早期遗址18处,采集各类石制品300余件,另有60件玻璃陨石。值得关注的是,在其中的14处遗址中都发现了类似西方阿舍利技术的手斧工具,数量共计88件。澄碧河库区是目前百色盆地内手斧分布密度最高的地区之一,为深入探讨中国手斧工具的技术与形态特征,以及东西方古人类技术与文化的交流与传播提供了宝贵材料。玻璃陨石的发现表明,澄碧河库区含手斧遗址年代与目前已知的右江干流地区含手斧遗址的年代相近,处于早-中更新世过渡阶段。

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