Geothermal gradients and heat flow in the Beaufort-Mackenzie Basin,Arctic Canada     

F. W. Jones  J. A. Majorowicz  J. Dietrich  A. M. Jessop 《Pure and Applied Geophysics》1990,134(3):473-483

Thermal gradients have been calculated and heat flow estimates made for 34 petroleum exploration wells along four regional profiles crossing the Mesozoic-Cenozoic Beaufort-Mackenzie Basin of northern Canada. The geothermal gradients vary from 22 mKm^–1 to 44 mKm^–1. Four sets of possible thermal conductivity values were used to calculate a range of heat flow values for each well. Generally low heat flow is observed in wells within the deeper portions of the basin and higher heat flow values occur in wells along the Aklavik Arch Complex which forms the southeastern margin of the basin.The contribution to heat flow by heat generation below the Mesozoic-Cenozoic basin fill sediments has been considered. The heat flow contribution from sub-Mesozoic sedimentary strata and underlying basement is highest along the basin-bounding Aklavik Arch Complex. The decrease in heat flow from below the basin fill sediments toward the basin depocenter may be related to basinward crustal thinning and corresponding reductions in intra-crustal radiogenic heat production.  相似文献   

Correlations among the reflectances of vitrinite, chitinozoans, graptolites and scolecodonts     

Rudolf Bertrand 《Organic Geochemistry》1990,15(6)

Paleozoic marine sequences sampled in outcrops and wells of northeastern Gaspe Peninsula (Quebec Appalachians) yield kerogen composed in part of vitrinite and zooclasts (chitinozoans, scolecodonts and graptolites) on which reflectance measurements were made.The comparison between means of random measurements show that reflectance of chitinozoans is similar to that of telinite (vitrinite with a cellular texture) and that the reflectance of scolecodonts is significantly lower than that of telinite in the lower range of studied values. At higher reflectivities differences decrease but, at the end of the condensate gas zone reflectancea are not yet identical. As shown by previous studies, reflectance of graptolites is slightly less than that of telinite.Pyrobitumen reflectance is related to the lithology of the host-rock and no generalized correlation can be established between the reflectance of pyrobitumen and that of vitrinite.  相似文献   

A densely feathered ornithomimid (Dinosauria: Theropoda) from the Upper Cretaceous Dinosaur Park Formation,Alberta, Canada     

《Cretaceous Research》2016

A recently discovered articulated partial skeleton of Ornithomimus from the Upper Cretaceous Dinosaur Park Formation of Alberta, Canada is remarkable in the extent and quality of preservation of integumentary structures including feathers. It is the first ornithomimid to preserve a tail bearing extensive plumaceous feathers that are slightly more elongate in comparison to those present on the remainder of the body. However, the underside of the tail and the hind limb distal to the middle of the femur appear devoid of plumage. Overall, the plumage pattern in Ornithomimus is similar to that of Struthio camelus (ostrich) and other large palaeognaths, indicating a probable function in thermoregulation. The specimen also preserves the body outline around the legs, including a skin contour anterior to the femur, analogous to skin webs in extant birds. Whereas the knee web of birds bridges the knee to the abdomen, in Ornithomimus it spans from the mid-femoral shaft to the abdomen, and is herein referred to as an anterior femoral web. This is the first report of such soft tissue structures in non-avian theropods. It may indicate that the resting position of the femur was positioned more anteroventrally in ornithomimids than in most theropods, and in that sense may have been transitional to the situation in modern birds.  相似文献   

Changes in the northern Gulf of St. Lawrence ecosystem estimated by inverse modelling: Evidence of a fishery-induced regime shift?   总被引：1，自引：0，他引：1  

Claude Savenkoff  Martin Castonguay  Denis Chabot  Mike O. Hammill  Hugo Bourdages  Lyne Morissette   《Estuarine, Coastal and Shelf Science》2007,73(3-4):711-724

Mass-balance models have been constructed using inverse methodology for the northern Gulf of St. Lawrence for the mid-1980s, the mid-1990s, and the early 2000s to describe ecosystem structure, trophic group interactions, and the effects of fishing and predation on the ecosystem for each time period. Our analyses indicate that the ecosystem structure shifted dramatically from one previously dominated by demersal (cod, redfish) and small-bodied forage (e.g., capelin, mackerel, herring, shrimp) species to one now dominated by small-bodied forage species. Overfishing removed a functional group in the late 1980s, large piscivorous fish (primarily cod and redfish), which has not recovered 14 years after the cessation of heavy fishing. This has left only marine mammals as top predators during the mid-1990s, and marine mammals and small Greenland halibut during the early 2000s. Predation by marine mammals on fish increased from the mid-1980s to the early 2000s while predation by large fish on fish decreased. Capelin and shrimp, the main prey in each period, showed an increase in biomass over the three periods. A switch in the main predators of capelin from cod to marine mammals occurred, while Greenland halibut progressively replaced cod as shrimp predators. Overfishing influenced community structure directly through preferential removal of larger-bodied fishes and indirectly through predation release because larger-bodied fishes exerted top-down control upon other community species or competed with other species for the same prey. Our modelling estimates showed that a change in predation structure or flows at the top of the trophic system led to changes in predation at all lower trophic levels in the northern Gulf of St. Lawrence. These changes represent a case of fishery-induced regime shift.  相似文献   

加拿大海洋-海岸带地质调查与"海底资源填图计划"     

刘健  何起祥 《海洋地质前沿》2003,19(1):26-28

简要介绍了加拿大海洋－海岸带地质调查的推动力和基本经验，以及即将启动的“海底资源填图计划”（SeaMap)。加拿大海洋－海岸带地质调查强调多波束测深技术的应用、多学科的协作和数据库建设，SeaMap将对整个加拿大专署经济区进行综合填图。  相似文献   

加拿大海岸带调查工作     

周良勇  刘健 《海洋地质前沿》2003,19(1):1-4

简要介绍了加拿大海岸带调查工作，包括海岸系统的定义、海岸带的调查技术和设备、遥感技术和在海岸带调查中的应用，以及海岸监测的意义和监测方法。  相似文献   

Mid and late holocene diatoms from ‘Water Supply Lake’, Baffin Island,N.W.T., Canada     

Alexander P. Wolfe 《Journal of Paleolimnology》1991,6(3):199-204

Diatom analyses from a 40 cm sediment core from Water Supply Lake, northeastern Baffin Island, reveal 67 taxa of primarily benthic forms, strongly dominated by small Fragilaria spp. No major stratigraphic changes are noted in the diatom floral record, which encompasses the last 7000 years. In the uppermost 2 cm, there are increases in: a) F. virescens var. subsalina, b) the ratio of symmetric: asymmetric valves of F. construens, and c) species richness. These are interpreted as reflecting anthropogenic modifications of the lake (chlorination and deepening) associated with its use as a source of water for the community of Pond Inlet since 1979.  相似文献   

Hydrological extremes in a southwestern Ontario river basin under future climate conditions/Extrêmes hydrologiques dans un basin versant du sud-ouest de l'Ontario sous conditions climatiques futures     

《水文科学杂志》2013,58(4)

Abstract

The global climate change may have serious impacts on the frequency, magnitude, location and duration of hydrological extremes. Changed hydrological extremes will have important implications on the design of future hydraulic structures, flood-plain development, and water resource management. This study assesses the potential impact of a changed climate on the timing and magnitude of hydrological extremes in a densely populated and urbanized river basin in southwestern Ontario, Canada. An ensemble of future climate scenarios is developed using a weather generating algorithm, linked with GCM outputs. These climate scenarios are then transformed into basin runoff by a semi-distributed hydrological model of the study area. The results show that future maximum river flows in the study area will be less extreme and more variable in terms of magnitude, and more irregular in terms of seasonal occurrence, than they are at present. Low flows may become less extreme and variable in terms of magnitude, and more irregular in terms of seasonal occurrence. According to the evaluated scenarios, climate change may have favourable impacts on the distribution of hydrological extremes in the study area.  相似文献   

Probability distribution type of Canadian annual minimum streamflow / Type de distribution de probabilité du débit minimum annuel au Canada     

《水文科学杂志》2013,58(3)

Abstract

The method of L-moment ratio diagrams along with the averaged weighted distance (AWD) is applied to identify a probability distribution of annual minimum streamflow, namely annual minimum daily streamflow in 11 climatic regions of Canada. Across the entire country, the Pearson type III probability distribution is an acceptable distribution for describing annual minimum streamflow with the 3-parameter lognormal and log Pearson type III distributions as potential candidates. Some minor differences in the probability distribution type among different climatic regions are also observed, which may be taken into account in the selection of the distribution type of annual minimum streamflow.  相似文献   

北极冰海耦合模式对两种不同大气再分析资料响应的分析   总被引：2，自引：2，他引：0  

牟龙江  赵进平 《海洋学报》2015,37(11):79-91

本文中我们比较了Climate Forecast System Reanalysis(CFSR)高分辨率的再分析数据集和低分辨率的Japanese 25-year Reanalysis Project(JRA25)再分析数据集在向下短波辐射、向下长波辐射、10m风场、近地面气温、降水、湿度上的不同,发现二者差异最大的为降水数据,其次为向下短波辐射数据、向下长波辐射数据。用这两个数据集驱动同一冰海耦合模式,CFSR强迫的海冰、北冰洋中层水和加拿大海盆温盐结构与实测相比有很大差距,等密度面上的地转流速在加拿大海盆和欧亚海盆比JRA25强迫的结果高20%,同时等密度面的深度偏深、位温偏高,在弗拉姆海峡的流通量也比海洋再分析数据Simple Ocean Data Assimilation(SODA)偏多。CFSR的向下辐射数据更加接近实测,采用此数据的敏感性实验模拟结果与实测符合的更好。对于海冰的模拟,云量起着至关重要的作用,降水带来的淡水通量通过影响大西洋入流水携带的热量进而影响到冰区。此外,CFSR过量的降水也是二者对于北冰洋温盐结构、弗拉姆海峡流通量以及地转流强度模拟产生偏差的主要原因。尽管风场的分辨率不同,在海盆尺度上对于海冰和海水温盐结构的影响并不大。  相似文献