Cretaceous North America was divided throughout most of the period by the Western Interior seaway, which connected temperate waters to the developing Arctic Ocean and trop,cal waters of the opening Atlantic. Vast quantities of terrigenous clastic sediments, fed into the seaway from the Cordillera, accumulated in shallow waters during two, major, marine cycles of sedimentation. Widely distributed, rapidly evolving, invertebrate slocks and a reliable radiometric time-scale combine to produce an exceptionally refined stratigraphie system. Marginal-marine sand complexes, some of which have been used to establish model patterns of deltaic and interdeltaic sedimentation, record local and regional tectonic movements.
Durant presque tout le Crétacé, l'Amérique du Nord était coupée par la mer de l'Intérieur ouest qui reliait les eaux de l'Océan Arctique en voie de développement, à celles de l'Océan Atlantique. De grandes quantités de sédiments clastiques terrigènes provenant de la Cordillère se sont accumulées dans les eaux peu profondes durant deux cycles majeurs de sédimentation marine. Des groupes d'invertébrés très répandus et d'évolution rapide, ainsi qu'une échelle de temps radiométrique fiable nous offrent un système stratigraphique exceptionnellement raffiné. Des complexes de sables marins marginaux, dont quelques uns ont servi pour établir des modèles de sédimentation deltaïque et interdeltaique, se sont accumulés en réponse à des mouvements tectoniques locaux et régionaux.
Certain pairs of ammonite "species", different in size and exhibiting contrasting morphology on their adult stages, are shown to possess inner whorls (earlier growth stages) which are almost identical in all morphological aspects. The similarities indicate close genetic relationship, the divergence in size and adult body chamber being secondary sexual characters. Five such dimorphic pairs occur together in the same strata in the Middle Jurassic Yakoun Formation on the Queen Charlotte Islands and It is suggested that they represent the two sexes.
The continental margin of Atlantic Canada was formed by the rifting of continental masses in some areas and by the strike-slip motion between continental blocks in others. These motions imparted different structural characteristics to the basement. The subsequent development of the margins was controlled by thermal contraction and sediment loading which caused subsidence. These processes led to the formation of the East Coast Geosyncline. The geosyncline is divisible into a miogeociine encompassing the Mesozoic-Cenozoic succession underlying the continental shelf, and a eugeocline comprising strata of similar age underlying the continental rise and abyssal plain. The boundary between the miogeociine and eugeocline is in many areas represented by the modern and ancient continental slope.
I attempt in this article to put in context recent studies of the oceanic crust, studies which led to the drilling of the uppermost few hundred metres of the igneous rocks of the crust on Leg 37 of the Deep Sea Drilling Project. We see that physical measurements - seismic studies, heat-flow measurements and magnetic studies in particular, combined with observations of rocks dredged from the sea floor, and rocks drilled on oceanic islands lead to the idea that the oceanic crust is rather similar to the ophiolite suites seen on land. However, the oceanic crust is altered by the interaction of sea water with hot rocks near the ridge crests, and by cold weathering as the rocks lie exposed to water for millions of years. These alterations affect the physical and chemical properties of the crust, and must play a large part in determining the composition of sea water itself. The thermal processes involved in the rock-sea-water interactions modify the simple model of a cooling plate, where heat transported by the lateral convection of sea-floor spreading is lost by vertical conduction into the oceans.
The study of electromagnetic induction in the earth has provided a geophysical method for using magnetic and electric field variations observed on the surface to interpret electrical conductivity and earth structure over a wide range of depths. Analysis of geomagnetic data on a world-wide basis has shown that both conductivity and internal temperature increase rapidly in the mantle, between depths of 300 and 1000 km. In addition many localized zones of high conductivity have been found in the crust and upper mantle. Important anomalies of this type are located in the Cordillera regions of North and South America, in the Japanese Arc, North Germany, and in the Canadian Arctic to mention only a few. These large anomalies, some of them many hundreds of kms in extent, are often found near continental margins or near old plate boundaries. They appear to be associated in a fundamental way with the development of mobile belts and their study is becoming important in our understanding of global tectonics.
Ocean 74, the fifth IEEE International Conference on Engineering in the Ocean Environment, was held in Halifax, Nova Scotia, August 21 to 23, 1974, under the chairmanship of Ï. Ê. Gashus of Nova Scotia Technical College. This was the first time that the annual conference was held outside the USA. 529 people from many different countries attended: 125 papers by authors from 10 different countries were presented.
The major portion of the work presented was oriented toward electricai and electronic engineering but the Technical Program Committee did seek papers from other disciplines to exemplify the multidisciplinary nature of oceanography. The work in temperate and Arctic waters was the main emphasis of the conference and the largest session dealt with "Engineering and Physics of Sea Ice". Other subject areas included: 1. Seismic reflection methods and geological instrumentation and techniques, 2. Positioning at sea, Acoustic applications, techniques, instrumentation, and scattering, Data acquisition, communications, telemetry, and signal processing, Instrumentation, sensing in the ocean environment, and pressure 3. tolerant electronics, 6. Pollution monitoring, fish monitoring and counting, and deep-water fishing technology, 7. Tidal power and tidal measurements in the open ocean, 8. Buoys, manned submersibles and diving technology, ship behaviour and handling, and mechanical engineering.
The conference proceedings were made available prior to the conference and this appeared to stimulate discussion periods after each paper.
The earth science workshop at the University of Western Ontario has now completed five summer sessions and over 100 teachers from across Canada have attended. During the last three years, two Canadian teachers have supervised the development of a Canadian program, with emphasis on methodology with development of classroom exercises and field projects. Approximately one-third of the course is devoted to field trips. Visiting speakers discuss relevant matters of current interest. Present financing is provided by Shell Canada Ltd. Although this workshop is providing a need in the short term for earth science teachers, university-trained teachers will be required as the demand for a course on earth science increases at the secondary school level.
An international conference was held in Belgium, 2-10 September 1974, to discuss a complete revision of the biostratigraphy of the Devonian and Lower Carboniferous. The symposium was held in the field to permit participants to collect from the classic sections of the Dinant synclinorium and the Namur "synclinal". An example of the detailed bio-stratigraphie work that has been done is provided by one section in the Famennian, which has been subdivided into 73 micropaleonto-logical zones-a degree of subdivision even greater than the subdivision of the Cenozoic on the basis of microplankton. Although many of these zones may be of local significance, it is clear that the region visited constitutes a remarkable stratigraphie succession, where subsidence continued for a long time and where practically all mio-geosyncMnai faciès interfinger. Knowledge of the biostratigraphy of this area is well-advanced and it may be expected to serve as a valuable standard of reference. (Summary prepared by the editor).