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1.
Few studies have been conducted into the environmental history of the North Coast region of New South Wales (NSW). To address this, two sedimentary sequences located in the coastal Bundjalung National Park and at Bungawalbin Creek, just north of the Park (both near Evans Head, NSW) have been investigated. Palynological and geochemical analyses were used to reconstruct the history of the sites. Fossil pollen evidence representing much of the Holocene period — basal radiocarbon dates of 8700 ± 60 years BP and 6600 ± 60 years BP are available from the Bundjalung National Park and Bungawalbin Creek sites, respectively — indicates a dynamic past environment, with an overall tendency towards drier conditions. This evidence is supported, in part, by charcoal analyses indicating an increase in the occurrence of fire over time. Chemical analyses of the sediments indicate that the Bungawalbin site was strongly influenced by estuarine conditions, whereas the Bundjalung National Park site was only influenced indirectly by estuarine conditions.  相似文献   

2.
Geografisk Tidsskrift—Danish Journal of Geography 110(2):261–278, 2010

In a comprehensive overview of evidence for fishing in the Thule period of the eastern North American Arctic, Whitridge (2001) noted that fish bones are either extremely rare or absent in archaeofaunal samples, despite the fact that artifact assemblages typically contain a variety of fishing implements. In this paper, we present new faunal data from two sites on southeastern Victoria Island, Nunavut, which offer a marked contrast to this pattern. The Pembroke site, located just north of Cambridge Bay, is a small Thule site probably occupied during an early migration into the region. The Bell site, located on the Ekalluk River, is a more substantial site, occupied for a much longer duration during the Thule period. These sites are located in areas devoid of many taxa preferred by Thule peoples, which led the sites' occupants to rely on caribou and fish for much of their winter subsistence. At the Bell site, storage of caribou and fish was critical for winter survival. However, the occupants of the Pembroke site appear to have been unable to acquire sufficient stores during the fall, and therefore relied on fishing through the ice during winter to supplement their inadequate stores. Although both sites indicate a more important economic role for fish than has been recorded on any other eastern Arctic Thule winter site, the use of fish at the two sites differs markedly, adding nuance to archaeologically known Thule subsistence patterns.  相似文献   

3.
A multi-proxy paleolimnological record obtained from a small, lowland closed-drainage basin located in the Peace-Athabasca Delta (Alberta, Canada), 10 km northwest of the present-day shore of Lake Athabasca, captures evidence of pronounced hydroecological changes over the past ~400 years. Consistent with historical maps produced by early European explorers of western Canada, paleolimnological data support the existence of a Lake Athabasca highstand during the Little Ice Age (LIA), c. 1600–1900 Common Era (CE). This contrasts with interpretations from previous analyses on sediment cores from an upland closed-drainage basin located centrally within the Peace sector of the delta that indicate low water levels during this interval. The different paleohydrological records at these two basins reflect the relative influence of different controls on the lake water balances. During the LIA, the lowland site was influenced by high levels in Lake Athabasca, whereas the elevated basin was outside the range of water-level rise in the lake and its distributaries, and was instead controlled by dry atmospheric conditions that led to evaporative drawdown. Integration of paleolimnological records and historical sources demonstrates that the ecosystem has undergone marked climate-driven hydroecological change over the past century, which is important information for effective management.  相似文献   

4.
The Kråkenes late-glacial palaeoenvironmental project   总被引：1，自引：0，他引：1  
Kråkenes is the site of a small lake on the west coast of Norway that contains a long sequence of late-glacial sediments. The Younger Dryas is well represented, as a cirque glacier developed in the catchment at this time. This site offers unique opportunities to reconstruct late-glacial environments from independent sources of evidence; physical evidence (glacial geomorphology, sedimentology, palaeomagnetism, radiocarbon dating), and biological evidence from the remains of animals and plants derived from both the terrestrial and aquatic ecosystems. This report describes the background to the site, and the international multidisciplinary project to reconstruct late-glacial and early Holocene environmental and climatic changes at Kråkenes.  相似文献   

5.
ABSTRACT. This paper presents evidence for a neotectonic influence on Late Pleistocene/Holocene records of environmental change in the southern Strait of Magellan. We concentrate on one site, Puerto del Hambre, a key location for reconstructing palaeoenvironmental change in southernmost South America. We report geomorphological, structural geological, seismic and topographic data that all show the site has been affected by postglacial faulting. There is also indirect evidence from the site stratigraphy that the site has been displaced. Also, recent faulting explains some of the puzzles associated with interpretation of the palaeoenvironmental record at Puerto del Hambre. The implication of this work is that neotectonic faulting had a pervasive influence in the southern part of the Strait of Magellan and southernmost Tierra del Fuego, and thus affects glacial or sea level reconstructions in the area.  相似文献   

6.
This article examines the nature and timing of U.S. foreign direct investment (FDI) in the London legal market. Evidence from a survey of thirty–eight U.S. subsidiaries suggests that FDI has taken place primarily to serve U.S. clients located within the United Kingdom. The evidence also suggests that early investors (pre–1990) belong to a core group of multinational companies with headquarters located in first–tier U.S. cities (New York, Chicago, Los Angeles). Later investors more typically hail from smaller cities. The evidence reveals a number of important differences between early versus late investors. Specifically, subsidiaries that were established prior to 1990 are more likely to enjoy local decision–making autonomy than are their counterparts that entered the London market more recently. The article concludes with a brief discussion of the implications of the survey findings for future research on FDI in professional services.  相似文献   

7.
Pollen and macroscopic charcoal have been analysed from a sedimentary sequence representing approximately 6100 years from a site within Wollemi National Park. This is located to the north-west of Sydney and forms a part of the Greater Blue Mountains World Heritage Area. The overall aim of the work was to examine the prehistoric interrelationships between vegetation, fire and human activity. There were relatively minor changes in the vegetation over the last ～6000 years, perhaps reflecting the climate- and fire-resilient nature of the sclerophyllous vegetation found on Hawkesbury Sandstone throughout the Sydney Basin. Casuarinaceae declined in the late Holocene, a trend that has been detected in numerous palaeoecological studies throughout south-eastern Australia. This decline was unrelated to fire, which has been a persistent feature at the site over the entire analysed sequence. The fire regime at the site changed from 5.7 ka, which is interpreted as reflecting the onset of increased climatic variability associated with El Niño-Southern Oscillation (ENSO) events. Another dramatic change in the fire regime occurred at 3 ka, which was coeval with archaeological changes in the region. It is possible that the change in fire activity from 3 ka represented an alteration to Aboriginal management strategies associated with an increasing population and/or the increased risk of conflagrations in an ENSO-dominated climate.  相似文献   

8.
The Mjølnir impact crater in the Norwegian Barents Sea features among the 20 largest impact craters listed in the Earth Impact Database. The impact is dated to 142 ± 2.6 Ma, corresponding closely to the Jurassic/Cretaceous boundary in the Boreal stratigraphy. Multidisciplinary studies carried out over the last three decades have suggested that the up to 40 km wide crater was created by a 1–3 km diameter impactor colliding with a shallow epicontinental sea, causing regional havoc and a regional ecological crisis that followed in its wake. Only minor evidence for the consequences of the impact for the surrounding depositional basins has been documented so far. This study describes a large submarine slump penetrated by hydrocarbon exploration well 7121/9-1, located in the southern Hammerfest Basin and approximately 350 km away from the impact site. The slump is dated by a black shale drape, which contains characteristic impact-related biotic assemblages and potential ejecta material. This precise dating enables us to associate the slump with large-scale fault movements and footwall collapse along the basin-bounding Troms-Finnmark Fault Complex, which we conclude were caused by shock waves from the Mjølnir impact and the passage of associated tsunami trains. The draping black shale is interpreted to represent significant reworking of material from the contemporary seabed by tsunamis and currents set up by the impact.  相似文献   

9.
We report palaeomagnetic and rock magnetic results of a sedimentary sequence (Pertigalete cement quarry) located in northeastern Venezuela. Sampling was restricted to the vicinity of the contact between the upper Cretaceous Chimana and Querecual formations. Biostratigraphic evidence reveals an upper Albian age for this formational transition. Profiles of site-averaged NRM intensity of the high-coercivity (over 30 mT) and high-temperature (over 400 °C) components appear to be related to the contact and distance from the contact. We interpret this profile as the probable outcome of overlapping thermochemical remagnetization events resulting from hydrothermal activity that was focused along the two formations. Direct spectral analyses performed on the site-averaged stable NRM intensity profile allow the separation of at least two of these remagnetization events. On the other hand, palaeomagnetic results show a considerable streaking of site mean declinations, suggesting that tectonic or structural horizontal movements around a vertical axis have occurred after NRM acquisitions. Horizontal rotation angles, plotted against stratigraphic levels for bedding-corrected data, show some features that seem to coincide with the alteration peaks isolated in the profile of site-averaged stable NRM intensities. Thus, it appears that repeated thermochemical remagnetizations with overlapping unblocking spectra, and horizontal movements around a vertical axis could have been responsible for much of the within-site dispersion. A simple three-stage reconstruction of the possible chain of thermochemical and tectonic occurrences that could lead to the present-day palaeomagnetic and rock magnetic evidence is proposed. These events, including clockwise horizontal rotations around a vertical axis, are tentatively placed in a geological time framework between middle Miocene and Pliocene times according to the main geological and geochemical evidence available.  相似文献   

10.
New stratigraphic evidence from the Rossendale area, Manitoba, Canada, provides insight into the early postglacial evolution of the southeastern Assiniboine Delta. In this region, much of the upper 13+ m of sediment accumulation is characterized by multiple cycles of sandy rhythmites interbedded with massive to laminated silt. These sediments were deposited rapidly by traction or turbidity currents and record the construction of the Assiniboine fan-delta during the deep-water Lockhart Phase of glacial Lake Agassiz (>10.8 14C ka BP). Shortly before ∼10 14C ka BP, fluvial incision into deltaic deposits occurred locally at the Rossendale Gully site in response to the regression of glacial Lake Agassiz during the Moorhead Phase. Plant macrofossils deposited in the gully by 10 14C ka BP provide the first information on early postglacial plant colonization of the distal Assiniboine delta. These data suggest initial establishment of Scorpidium scorpioides, Potamogeton spp., Scirpus spp., and other wetland plants, followed by colonization of uplands by a Picea-Populus assemblage. Importantly, because the gully is located in a protected depression behind the Campbell beach, evidence of water table rise from aquatic macrophytes suggests that glacial Lake Agassiz transgressed to the Campbell level during the early Emerson Phase (∼10 14C ka BP). Furthermore, no evidence exists for a post-Lockhart rise in Lake Agassiz above the Upper Campbell beach. If Agassiz stood at the Campbell level during the early Emerson Phase, then drainage through the southern outlet may have been possible at this time. This scenario, if true, may suggest that the northwestern outlet was temporarily closed by a glacial advance shortly before 10 14C ka BP. This is the first in a series of ten papers published in this special issue of Journal of Paleolimnology. These papers were presented at the 47th Annual Meeting of the International Association for Great Lakes Research (2004), held at the University of Waterloo, Waterloo, Ontario, Canada. P.F. Karrow and C.F.M. Lewis were guest editors of this special issue  相似文献   

11.
A sediment core from a high-elevation bog on Maui in the Hawaiian Islands contains evidence for drier conditions between 9.4–5.8 kyr BP, followed by a wetter interval between 5.8–2.2 kyr BP, and a variable late Holocene. These precipitation changes may be a reflection of vertical displacements of the upper boundary of the mid-Pacific Trade Wind Inversion (TWI) cloud layer. Fires, probably volcanically ignited, occurred in the forests prior to human arrival. Polynesian activity in this high-elevation, remote site was apparently limited, with no pollen, charcoal, or sedimentological evidence for local anthropogenic disturbance. After European contact, grass fires increased and introduced plant species invaded the site. Values for Cd, Cu, Pb, and Zn in sediments throughout the Holocene indicate low trace-metal deposition from atmospheric particulates at the site, even in the twentieth century.This paper is one of a series of papers guest edited by Dr. Mark Brenner on tropical paleolimnology  相似文献   

12.
塔里木河中游植物群落与环境因子的关系   总被引：40，自引：2，他引：40  
应用数量分类和排序方法，对新疆塔里木河中游地区植被进行了多元统计分析。结果表明，该地区共有植物23种，隶属于11科21属。其中，多数植物种类在样方中的出现频次较低，说明该地区植物物种丰富度较低。TWINSPAN结果表明，该地区3个断面19个样地可分为3个主要类型，与实际调查结果一致。CCA排序结果同TWINSPAN分类结果基本一致，反映出植物群落分布格局的一般规律及其随环境因子梯度变化的趋势。分析了不同环境因子间的关系，并从定量的角度，以CCA排序图直观地揭示了决定塔里木河中游地区植物群落分布的环境因子主要是地下水位和土壤含水量，其回归模型分别为：X1＝-9.5991L 100.86（R^2=0.6459)；X2＝1.65W 43.011(R^2=0.7646)。  相似文献   

13.
戴湘毅  阙维民 《地理研究》2011,30(4):747-757
文物保护单位制度经过半个世纪的实施和推广,已经成为中国影响最大、覆盖范围最广的文化遗产保护机制,其收录的矿业遗产无疑是中国矿业文明的代表.通过对文物保护单位中矿业遗产项目信息的提取,建立数据库,对中国矿业遗产的时空分布特征及其影响因素进行研究.结果表明:文物保护单位中矿业遗产在空间上分布广泛,但呈不均衡状态,主要以东部...  相似文献   

14.
High seismic activity, difficult permafrost and hydrogeological conditions of South Yakutia (Russia) complicate building and exploitation of engineering construction and require additional detailed and complex research. These conditions are evident within two sites. The first site is located in the middle reach of the Duray River, where it is crossed by the highway Lena. The second site is located on the right side of the Chulmakan River Valley, 400 meters to the east of the ESPO oil pipeline route. Seismic events, occurring four years ago, led to landslides in the mentioned sites. Formation of joint fissures on slopes assisted drainage of aquifers of free water exchange zone. It is worth noting that at the Duray River site, 59 cm of active soil slumping movement towards the roadbed has occurred within two summer months. Such a process is complicated by cryogenic disintegration of rocks in the base of the landslide body due to groundwater discharge and icing formation in winter.  相似文献   

15.
Ancient agricultural systems based on runoff harvesting techniques are abundant in the Negev Highlands. The current study examined traditional classification and investigated the distribution of ancient agricultural systems around the Roman-Byzantine “Negev Towns” Avdat and Shivta, and across the terrain located between these sites and Makhtesh Ramon in the south. It led to an elaboration of the traditional classification of runoff agricultural systems in the Negev desert of southern Israel. We found that the key factors for building these types of agricultural systems were the geological and geomorphological characteristics of the specific site locations and the geographic distance from nearby towns and roads. Depending on these factors, a multitude of types of agricultural systems were constructed in accordance with the physical characteristics of the local desert environment. This clearly indicates the continuation of the current desert climate throughout historical times. Furthermore, the large diversity of agriculture installations indicates that they were constructed by local farmers and not by an external plan imposed by the central government.  相似文献   

16.
Geografisk Tidsskrift—Danish Journal of Geography 110(2):245–259, 2010

This paper presents results of recent archaeological research at the site of Oakes Bay 1 (HeCg-08), on Dog Island, Labrador, dated from the late 17th to late 18th century. Analyses of faunal remains provide a means of reconstructing the site's subsistence economy. The site's inhabitants practiced a very consistent mode of hunting throughout this time period, depending heavily on adult ringed seals taken on the fast ice in winter and spring. Juvenile ringed seals, taken at the ice edge in the spring were a secondary resource. A lack of evidence for the hunting of harp seals in the fall and of ringed seal pups in late spring suggests that the site had a relatively short season of occupation. The consistent pattern of hunting through time suggests that the impacts of climatic variability on Inuit subsistence in the Nain region were relatively limited, moderated by their capacity for mobility on the sea ice rather than by whole scale changes in hunting practices and species choice. The Oakes Bay 1 site presents an example of a different subsistence economy than that seen at other recently examined sites in Labrador, suggesting that the impacts of the so-called Little Ice Age were not global or uniform.  相似文献   

17.
Paleosalinity records of the Tianluoshan site are derived from measurations data of clay mineral,boron,strontium,barium,after field sampling in three profiles of the Tianluoshan site.The relative sea level changes are discussed according to the lab results.The record indicates that the region where the Tianluoshan site located has witnessed at least three times of relative sea level high-stand before,during and after the Hemudu period.Based on previous researches,this paper also focuses on discussing severa...  相似文献   

18.
苏干湖夏季鸟类调查及观鸟潜力评价   总被引：1，自引：0，他引：1  
苏干湖位于甘肃省西部阿克赛哈萨克族自治县境内,地处青藏高原北缘。该湖为多种水鸟的重要栖息地,已建为侯鸟自然保护区,但迄今未见有鸟类的专门调查。１９９７年７月至８月期间在该地区采用定点观察和路线观察法对苏干湖的水域、浅滩、沼泽和周围草地的鸟类进行了调查。调查的重点为鸟类的种类构成和居群数量,共记录到各种栖息生境的４６种鸟类,个体数量达２万多只,表明苏干湖是一处极为重要的湿地,并有观鸟旅游的价值。同时需加强对这一保护区的管理  相似文献   

19.
The Qinling Mountain Range (QMR) spans a large region in China and is an im-portant area of hominin activities.Many Paleolithic sites are found in Bahe,South Luohe,and Hanjiang river valleys in the northern,eastern,and southern part of the range,respectively.The Danjiang River valley acts as a channel connecting these valleys and stretches from the north to the south of the QMR.The previous dating of the Paleolithic sites in the Danjiang valley mainly relied on geomorphologic comparison,stratigraphic correlation,fossil charac-teristics,and Paleolithic artifacts,indicating a lack of absolute data.In this study,we con-ducted a detailed geochronological investigation of the entire valley,and selected an ideal site--the Miaokou profile.Based on the identification of the Ioess-paleosol sequences,opti-cally stimulated luminescence,and magnetostratigraphy,the Paleolithic artifacts of the Mi-aokou site located within the S5 and S6 layers of the profile belong to ～0.6-0.7 Ma.This suggests that the Paleolithic site is an old site in the Danjiang River valley,and this period also witnessed a rapid increase in the number of hominin sites during the Middle Pleistocene.Combining our results with previous reports across the QMR,we propose that the Danjiang River valley might have been a corridor for hominin migration,and is worthy of further inves-tigation.  相似文献   

20.
Summary. A seismic study of the Lesser Antilles arc has been carried out, first for the period 1950–1978, for which we can use local seismic networks to draw maps of instrumental seismicity, then for the period 1530–1950, for which we have catalogues of felt earthquakes. The striking feature of the spatial distribution of foci is the cluster of epicentres in the northern half of the arc; all large earthquakes ( M > 7.5) are located north of 14° latitude. Seismicity cross-sections through the arc show a variable dipping subduction zone along the arc; the deep seismic zone is steeper in the centre of the arc than on the extremity.
The time-space diagram for historical seismicity, and the evidence of a seismic gap at the east of Guadeloupe lead us to consider the northern half arc as a likely site for a large earthquake in the near future.
The seismic slip rate calculated from all major earthquakes since 1530 is of much greater value than that obtained from recent plate tectonic models, suggesting that the recurrence rate of earthquakes is more than many hundreds of years with a possible aseismic creep.  相似文献   

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