摘要:

Jurassic index fossils of the Canadian Cordillera indicate the presence of some zones of most Jurassic stages. In this report the more important localities are listed, the source of information, published and unpublished, is indicated, and an up-dated correlation chart is presented. The importance of tectonic events and their effect on the completeness of the Jurassic fossil record and on the Jurassic paleogeography are stressed.

ISSN:0008-4077    

DOI:10.1139/e70-001

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Lower Paleozoic carbonatites associated with the St. Lawrence graben system are correlated with carbonatites of similar age (565 m.y.) in Greenland and Scandinavia. The correlation is well established in Canada where the intrusions all occur along a continuous rift system. The reconstruction of the whole province is made possible by restoring the continents to the positions they occupied prior to their separation.The combination of unique petrologic character, age, and structural setting shows that these rocks belong to a single alkaline rock province, defined by a rift system extending at least from central Canada to eastern Sweden that was active throughout its length about 565 m.y. ago.Periodic intrusion of alkaline rocks has occurred later, on both continents, associated with the components of the fracture system. In eastern Canada, alkaline rocks occur locally with ages of 520, 450, 300, and 110 m.y. in addition to the widespread 565 m.y. event.

ISSN:0008-4077    

DOI:10.1139/e70-002

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Miospores of early Frasnian age are described from the third unit of the Escuminac Formation in eastern Québec, Canada. The assemblage comprises 34 species, including 8 species proposed as new, 2 new combinations, and 12 sparsely represented forms not considered synonymous with previously described species.The assemblage is most closely comparable to a Middle Devonian assemblage from the Orcadian Basin, Scotland. Similarities are also noted with European and Russian assemblages, particularly from the Eifelian–Givetian of the Russian Platform. Except for five long-ranging species, elements of Lower Carboniferous assemblages are lacking. Evidence suggests a transitional nature for this Escuminac assemblage. Miospores of relatively large size, a feature of Middle Devonian assemblages, are present. Marked differentiation of large and small spore types, found in several other Upper Devonian assem blages is absent. Apiculate and anchor-spined species dominate the Escuminac assemblage.

ISSN:0008-4077    

DOI:10.1139/e70-003

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The lower Cretaceous Crowsnest Formation of the Crowsnest Pass area, Alberta, is predominantly trachytic, but some sodic, analcite-rich, rocks occur. It consists of bedded pyroclastic and epiclastic material with minor flows and dikes. Most of the volcanism appears to have been explosive in nature. Almost all the igneous material is porphyry tic; nearly all the phenocrysts are zoned, and evidence of resorption is common. Sanidine phenocrysts show evidence of repeated growth and solution with as many as 60 cycles per crystal. The primary, igneous, analcite phenocrysts of the analcite phonolites and blairmorites crystallized at depth, and were preserved by rapid vertical transport and quenching at the surface. In many cases, however, partial or complete decomposition of the crystals occurred, and thermal discoloration of the analcite can be reproduced in the laboratory.

ISSN:0008-4077    

DOI:10.1139/e70-004

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A curve relating composition of synthetic pentlandite with interplanar spacing was determined experimentally as follows:d115 = 1.9407 – 0.0023x + 0.0077x2, wherexrepresents the iron to nickel weight ratio withd115measured in Å and the sulfur content is fixed at 33.05wt %. The following iron, nickel, and sulfur solid solubility limits of pentlandite were determined:X-ray powder patterns of monosulfide solid solution heated at 500 and 400 °C with a composition (wt %) of 18.8 Fe, 43.8 Ni and 37.4 S showed a modulated structure. A solvus interrupts the monosulfide solid solution at 275 ± 10 °C and the approximate composition in wt %: Fe = 22.5, Ni = 40, and S = 37.5.The relatively common occurrence of the pyrite–pentlandite assemblage in nickel ores shows that the solid state reactions attendant upon cooling of these ores, proceed to temperatures at least below 200 °C.

ISSN:0008-4077    

DOI:10.1139/e70-005

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

At Cobalt the Nipissing diabase intrusive occurs as a 1000 ft (~305 m) thick undulating sheet exposed in a series of basin and arch structures from which 112 specimens were collected at 14 sites. Paleomagnetic analysis of the cleaned natural remanence directions from the 11 acceptable sites suggests that these structures are dominantly primary. Minor post-solidification compression associated with the NW–SE trending faults may have amplified the primary NE–SW axial trends of the structures. Significant folding adjacent to the faults does not appear probable. The origin of the narrow argentiferous veins is probably related to minor local differential movements of large blocks of diabase or to cooling-contraction of the sheet. A revised pole position of 91.9 °E, 19.4 °N (dp = 3.9°; dm = 6.5°) is given for the 2140 m.y. old Nipissing diabase.

ISSN:0008-4077    

DOI:10.1139/e70-006

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Many new age determinations are reported for the Precambrian of Rajasthan and Bundelkhand in northern peninsular India. All are by Rb–Sr and mostly from total-rock analyses. They show that the oldest rocks in the area are undated sediments intruded by the Bundelkhand and Berach Granites, dated at about 2550 m.y. The overlying Aravalli System was intruded by granites dated at between 1900 and 2100 m.y., and is succeeded by the Delhi System, which was intruded by granite dated at 1650 m.y. Other granitic intrusion at 950–1000 m.y. was followed by repeated pegmatitic intrusion. The Banded Gneiss Complex of Rajasthan contains components of ages varying from at least 2000 m.y. to less than 1000 m.y. Nepheline-syenites at Kishangarh have an age of 1490 ± 150 m.y., but a biotite in an inclusion gives 970 m.y., which is the age of the Newania carbonatite.These determinations show that the Precambrian sequence in Rajasthan is much older than previously suggested. They confirm the antiquity of the Bundelkhand–Berach craton suggested by field studies, denying its derivation from Aravalli System rocks by granitization.

ISSN:0008-4077    

DOI:10.1139/e70-007

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Data relating to the mixing rate of the Liard and Mackenzie Rivers were collected in June 1968, for a distance of 300 miles (~482.8 km) downstream from their confluence. Samples were collected from 11 cross sections, spaced about 30 miles (~48.3 km) apart. At each cross section, 5 surface samples and 3 subsurface samples from a depth of 20 ft (~6 m) were collected, to give a total of 88 samples.The temperatures at the 88 sample points were measured in place. Secchi disk transparency readings were taken for the 55 surface sites. Water samples collected at the 88 sites were laboratory tested for their turbidity, conductivity, and sodium and chloride concentrations.Analyses of the results show that the Mackenzie and Liard waters were not fully mixed some 300 miles (~482.8 km) downstream from their confluence. Some overflow and underflow, due to density differences, probably occurred.Quite possibly the long distance required for mixing may be more common, in large broad rivers, than is generally realized.

ISSN:0008-4077    

DOI:10.1139/e70-008

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

In eastern Prince of Wales Island the Peel Sound Formation is subdivided into upper and lower members on the basis of lithology. The upper member comprises five laterally equivalent north–south facies belts which are in westward order:1) Conglomerate Facies: cobble and boulder conglomerates deposited on alluvial fans mainly by the action of debris floods.2) Conglomerate–Sandstone Facies: interbedded conglomerate, fine to coarse red sandstone and red siltstone in a repeated fining-upward succession, deposited by low sinuosity braided streams. Cyclic sedimentation is attributed to channel migration and infill.3) Sandstone Facies: the presence of laterally extensive planar cross sets suggests point bar deposition in high sinuosity streams. Tabular bedded sandstone was deposited by stream floods in upper regime flow.4) Sandstone–Carbonate Facies: streams flowing westward formed small deltas, accumulating red, pink, and buff sandstones as topset deposits, interbedded with dolomites containing marine fossils, and clean washed gray sandstones, shales and dolomites with ostracods, pelecypods, gastropods, andLingula, indicating an estuarine environment.5) Carbonate Facies: dolomites with abundant marine fauna and limited clastic content. Sedimentary structures indicate quiet, shallow water conditions.Paleocurrent evidence indicates an easterly source, confirmed by conglomerate clasts derived from the Boothia Uplift, an area of Lower Paleozoic and Proterozoic rocks extending northwards from the Boothia Peninsula to Somerset Island.

ISSN:0008-4077    

DOI:10.1139/e70-009

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Samples of Cretaceous sediment have been dredged from the Scotian Shelf at a locality 100 km north-northwest of Sable Island.Continuous seismic-reflection profiles across the sample area show the presence of well defined stratification within the bedrock. These beds are truncated by the slopes of submarine valleys which transect the area. Bedrock appears to outcrop along the upper portion of the valley walls or be covered by a layer of unconsolidated material so thin as to be beyond the resolution of the seismic equipment. The dredged material appears to have come from rubble heaps near the base of the valley slopes and is believed to have originated locally.Approximately 450 kg of sedimentary rock were recovered consisting principally of sideritic quartz sandstone and arenaceous sideritic carbonate, both with fossiliferous material. Glauconite is a significant constituent of many samples.The macrofauna include sufficiently diagnostic forms to suggest correlation with the early Upper Cretaceous (Cenomanian) though the possible presence of older or younger forms cannot be wholly excluded. The microflora and microfauna appear to correlate mainly with the Albian-Aptian, and Albian-Cenomanian, respectively.Cretaceous strata immediately underlie much of the central and eastern portions of the Scotian Shelf. Tertiary sediments reported by Marlowe and Bartlett overlie the Cretaceous toward the continental margin and appear to occur as a discontinuous veneer at other localities on the shelf.

ISSN:0008-4077    

DOI:10.1139/e70-010

出版商:NRC Research Press    

年代:1970

数据来源: NRC