Volume 11, numéro 1, march 1984

EN :

Geological research and survey work by the Alberta Geological Survey is concentrated in three main areas — energy resources, mineral resources and environmental geology. The collective results of current investigations reveal some exciting new perspectives on Alberta's geology, particularly with regard to the faciès and depositional environments of the oil sands, petroleum and coal-bearing strata of the plains, the industrial mineral potential of the province, and the region's Quaternary stratigraphy and glacial history.

FR :

L'Alberta Geological Survey concentre sarecherche et ses relevés dans trois principaux domaines de la géologie: les ressources énergétiques, les ressources minières et la géologie de l'environnement. Le résultat global des investigations encours nous ouvrent d'intéressantes perspectives sur la géologie de à Alberta, tout particulièrement en ce qui concerne les faciès et conditions de sédimentation dessables bitumineux et des couches productrices du charbon et du pétrole des plaines, le potentiel minier industriel, la géologie glaciaire et la stratigraphie du Quaternairede la région.

EN :

Earthquakes have been felt or reported in the Maritime Provinces for over two hundred years but it is only within the last decade that enough seismographs have been in place to detect the smaller events. In general, the epicenters of more recent earthquakes are in the same area as the larger historical earthquakes: Grand Banks, Bay of Fundy, Moncton-Dorchester area and the Central Highlands of New Brunswick, although the latter area has only been really emphasized by the Miramichi earthquakes of 1982. Values of magnitude for historical earthquakes have been reduced by basing them on felt area, rather than on maximum intensity, and there is some evidence that the epicenter of the large earthquake of 1869 in New Brunswick may have a more northerly location. Reactivation along old fault lines, concentration of stress at pluton boundaries and glacio-isostatic movements have all been offered as explanations for the cause of earth-quakes in the region. Support for all three hypotheses has been found in various studies and it is not possible at the moment to refute any of these explanations.

FR :

Dans les provinces maritimes, des tremble-ments de terre ont été ressentis ou rap-portés sur plus de 200 ans, mais ce n'estque durant les dix dernières années qu'unnombre suffisant de sismographes enplace a permis de détecter des événe-ments de moinures ampleurs. Générale-ment, les epicentres des tremblements deterre récents se situent aux environsmêmes de ceux des grands tremblementsde terre historiques: les Grands Bancs,la Baie de Fundy, la région de Moncton/Dorchester et les Hautes Terres du Nau-veau Brunswick, quoique l'attention n'aitété attirée sur cette dernière région quedepuis le tremblement de terre de Mirami-chi en 1982, Les magnitudes des tremble-ments de terre du passé ont des valeursinférieures aux intensités maximales carelle ont été déduites de ce qui a été res-senti dans les régions secouées et il existedés evidences indiquant que l'épicentredu tremblement de terre de 1869, au Nou-veau Brunswick, aurait eu une positionplus Nord que celle antérieurement admise.Diverses origines pour ces tremblementsde terre ont été proposées: réactivationd'anciennes failles, concentration des con-traintes en bordure des plutons ou réa-justement isotastique. Des arguments enfaveur de l'une ou de l'autre de ces hy-pothèses peuvent être trouvé dans différ-entes études et il n'est actuellement guèrepossible d'en rejeter une seule.

EN :

North and west of Thunder Bay Archean rocks of the western Superior province consist of metasedimentary schists, gneisses, migmatites and granitic plutonic rocks of the Quetico belt in contact with metamorphosed pillow lavas and various volcanoclastic rocks of the Wawa belt.

At Hazelwood Lake steeply plunging, isoclinal folds accompanied by a pervasive east-west striking axial planar cleavageare developed in a well stratified sequence of greywackes and slates. Fold hinge lines commonly parallel the dip direction of the axial surface. Consequently, the folds close sideways and are neutral folds.

In most outcrops local younging of strata is readily determined from graded beds. When bedding and local younging are projected onto the axial planar cleavage, the structural facing of the folds and the stratigraphic younging of the succession as a whole is in the direction of the younger strata along a line at right angles to the trace of bedding in the cleavage. At Hazelwood Lake the trace of bedding on the cleavage is commonly subvertical and therefore the structural facing of the folds is primarily side ways. Reversals in the structural facing direction imply that these F2 folds were generated in previously folded strata.

A succession of metavolcanic rocks in contact with the polyphase deformed meta-sedimentary terrain appears also to have been folded by the F2 event.

The nature of the contact prior to the F2 folding, the presence of previous folds in the metavolcanic rocks, and their stratigraphic position with respect to the grey-wackes and slates are not clear from the available data.

EN :

There are encouraging signs of the potential of the Huronian Supergroup to host Witwatersrand-type paleoplacer gold. A total of thirty-one Au or Au-U occurrences are recognized as being stratiform. Of these, two occur in the Cobalt Group, four in the Quirke Lake Group, nineteen inthe Hough Lake Group and six in the ElliotLake Group. The greatest number of occurrences are located in the Matinenda and Mississagi Formations of the Elliot Lakeand Hough Lake Groups. Gold in basal Huronian rocks is related to basement geology and to a local source. Exciting recent finds in the upper Huronian Lorrain Formation in the northern half of the Cobalt Embayment represent extensively re-worked fluvial deposits in braided streams distant from the provenance of the gold. Geological conditions closely resemble those of the Witwatersrand. Sedimentological studies hold the key to locating the more attractive concentrations of gold.