摘要:

Measurements of the14C concentration in a Douglas fir from Vancouver Island indicate a maximum variation of 44‰, during the past 1 100 years. The magnitude and trend of these variations are similar to those observed by de Vries (1958) in oak from Germany and by Williset al. (1960) in sequoias from California, confirming earlier observations that atmospheric mixing of CO2takes place rapidly on a large scale.14C measurements of successive annual growth rings from the piths of two firs (346 years and 1 142 years old) show no variations beyond those attributable to the statistical counting error of ± 6‰. Thus, cyclic variations in sunspot activity and (or) climate, if present during these intervals, did not affect the14C concentration in the biosphere appreciably.A mechanism, based on a climate-sensitive carbon pumping rate of the biosphere coupled with the temperature-dependent oceanic CO2content is postulated to explain, qualitatively, the observed short-term (150 years or less) and long-term (1 000 years or more)14C variations in the land biosphere. Short-term fluctuations are directly proportional to temperature because variations in the carbon fixation rate lead to a pulsating CO2content of the atmosphere. Long-term changes are inversely proportional to temperature because large quantities of carbon, normally stored in deeper regions of the ocean, are exchanged between biosphere and hydrosphere.

ISSN:0008-4077    

DOI:10.1139/e66-001

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Results of rapid-method chemical analyses of samples taken at about 500-ft stratigraphic intervals through two sections of Yellowknife Group volcanic rocks are presented in graphical and composite form. The Yellowknife section is about 40 000 ft thick with the base undefined; the Cameron River section, about 45 mi northeast, is about 7 000 ft thick and may be complete.Two aspects of the volcanic chemistry considered are (1) variation in composition with stratigraphic height; (2) bulk composition of the volcanic rocks.Chemical data of the Yellowknife section define two volcanic cycles in each of which mafic lavas show a small but significant increase in sialic components with stratigraphic height culminating abruptly in acidic layers. The Cameron River section shows a similar but less well-defined trend. Iron–magnesium ratios stage a succession of systematic increases, each persisting for a few thousand stratigraphic feet, but no overall systematic variation. The two types of chemical variation correspond to calc-alkali and tholeiitic differentiation trends respectively. The tholeiitic trend is attributed to fractionation in high-level magma chambers, demonstrated for Yellowknife magma by the Kam Point sill, and the calc-alkali trend to contamination of tholeiitic magma by sialic crust.Frequency distribution diagrams show Yellowknife volcanic rocks to be similar to Chayes' circumoceanic basalts in TiO2, CaO, and MgO and to his oceanic basalts in Al2O3. The characteristic rock type is basalt.

ISSN:0008-4077    

DOI:10.1139/e66-002

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Stromatoporoids are abundant in parts of the Sayabec, St. Leon, and Mont Wissick formations of Wenlock and Ludlow age in eastern Quebec, Canada. The fauna is a mixture of species from Wenlock strata of northern Europe, the Wenlock and Ludlow beds of Baie des Chaleurs, Quebec, and Niagaran rocks of the Great Lakes region.Clathrodictyon crickmayiandStromatopora primashow the affinity of the fauna to that described by Parka from Baie des Chaleurs.Densastroma astroitesindicates a close connection of the fauna with the rocks of Wenlock age in England and the Baltic area.Stromatopora antiquashows the affinity of the fauna to that of central North America.Ecclimadictyon fastigiatumis a widespread species in all these regions. A new species ofActinodictyon(A.quebecense) is described. Two unnamed species ofStromatoporaandClathrodictyoncf.podolicamake up the rest of the fauna.

ISSN:0008-4077    

DOI:10.1139/e66-003

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

One hundred and sixty-eight North American shales, ranging in age from Proterozoic to Cretaceous, have been analyzed for boron; analyses for CO2permitted corrections to a carbonate-free basis. The B values mostly agree with the inferred salinities of the environments of deposition, based on geological evidence: anomalously low values in the Devonian Littleton formation may be correlated with loss of B to regional quartz–tourmaline veins.The data do not permit drawing any inference regarding secular variations in oceanic B content.A review of recent work on B sedimentary geochemistry indicates the need for analyses of real, rather than hypothetical, mineral phases.

ISSN:0008-4077    

DOI:10.1139/e66-004

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The results of several seismic refraction profiles on the continental shelf and slope of the eastern seaboard of Canada are now available. Gravity measurements which begin near the coast of Nova Scotia and end over the abyssal plain have also been made along two tracks perpendicular to the shelf edge. Various models for the crustal and upper mantle structure are presented. A density distribution assumed for each model resulted in a computed gravity field satisfying the observed gravity measurements. The models in agreement with all seismic data suggest that horizontal and vertical density variations occur in the upper mantle down to 100 km. The results indicate a mantle density of 3.42 g/cm3under the continental shelf and 3.32 g/cm3under the ocean basin.

ISSN:0008-4077    

DOI:10.1139/e66-005

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Tide gauge data from Churchill, Manitoba, for the period 1928–1939 are reviewed and rejected as inaccurate. The rate of uplift proposed by Gutenberg on the basis of these data therefore is rejected also. Data from 1940 to 1964 are subjected to statistical analysis, which indicates an apparent lowering trend of water level. Linear regression suggests a rate of 2 ft per century.

ISSN:0008-4077    

DOI:10.1139/e66-006

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The results of seismic refraction profiles in the Gulf of St. Lawrence and on the northwest and northeast coasts of Newfoundland are presented. The thickness of the crust is about 45 km in the region of the Gulf of St. Lawrence southwest of the Cabot Strait Trough, and off the northeast coast of Newfoundland east of the Long Range Mountains. One interpretation of the data suggests that the compressional wave velocities through the underlying mantle are 8.50 and 8.69 km s−1respectively. An "intermediate" layer about 20 km thick is identified with compressional wave velocities of 7.35 and 7.52 km s−1beneath these areas. A thinner crust, 33 km thick approximately, underlies the west coast of Newfoundland, and a crustal thickness of 35 km is postulated near Anticosti Island. The compressional wave velocity in the upper part of the mantle beneath this thinner crust is close to 8 km s−1. The intermediate layer thins and, possibly, pinches out in the vicinity of Anticosti Island and northwest Newfoundland. The results lead to the suggestion that we see within the crust and upper mantle the subsurface expression of the two-sided nature of the Appalachian system. The system shows no sign of quietly dying away beneath the northeastern coast of Newfoundland.

ISSN:0008-4077    

DOI:10.1139/e66-007

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

In the converted-wave method of seismic refraction interpretation, travel times for compressional, converted, and transverse head waves are used in combination to obtain velocities and layer thicknesses. The applicability of the method over interfaces with high dip and curvature is investigated, treating the two- and three-layer cases for layers of uniform velocity, with upper-layer velocity known, where the problem is to calculate velocities at depth and delineate the interfaces. It is shown that although dip and curvature affect the calculation, procedures can be devised to obtain solutions in the presence of these factors. Examples of application of the method in the two-layer case to a plane interface dipping at 30°, and to a curved interface with dip changing linearly from 0° to 27° are given.Depth calculation using intervals between the travel times of converted waves are shown to be independent of dip for a plane interface, but sensitive to curvature for a curved interface. It is shown that in these cases, a satisfactory depth calculation is possible.Ratios of these time intervals are shown to produce depth ratios that are either independent of velocity or with low dependence upon this parameter.A number of capabilities peculiar to the converted-wave method are noted.

ISSN:0008-4077    

DOI:10.1139/e66-008

出版商:NRC Research Press    

年代:1966

数据来源: NRC

ISSN:0008-4077    

DOI:10.1139/e66-009

出版商:NRC Research Press    

年代:1966

数据来源: NRC

ISSN:0008-4077    

DOI:10.1139/e66-010

出版商:NRC Research Press    

年代:1966

数据来源: NRC