Interpretation of fracture and physiographic patterns in Alberta,Canada

Thousands of linear elements (joint traces, river trends and photolinears) have been identified and statistically analysed in the Province of Alberta, Canada, from the U.S. border to the Fort McMurray area. A statistical evaluation was performed on the data by fitting Dimroth-Watson distributions to groups of them. It is suggested that the joints represent shear surfaces formed in a neotectonic stress field whose maximum compression is oriented normal to the front of the Rocky Mountains, at least in the vicinity of that range. Further to the northeast, the stress trajectories swing to E-W and N-S directions. The river courses in Alberta do not align themselves with the joints and are presumably controlled by the general slope of the land towards Hudson's Bay. The photolineaments are features of uncertain origin and age.     

Hydrogeomorphology

A review of the current state of our knowledge of the mechanical effects caused by (liquid) water on the morphology of the Earth is presented. The mechanical interaction of surface water and groundwater with landscapes is described and the mechanical effects of the sea on coastal regions and on the ocean bottom are discussed.     

On solitary waves generated by a moving pressure field

Summary The waves generated by a steadily moving two-dimensional pressure distribution are examined using non-linear shallow water theory. The applied pressure is zero ahead of the disturbance, that is in the downstream direction, and is a constantP ₀ in the upstream direction, these regions being joined smoothly by a cubic function.We consider here only the case of supercritical flow in both regions, the solution representing an asymmetric solitary wave travelling with the disturbance. The wave profiles are determined by an iterative method previously employed for non-linear waves. Wave amplitudes and profiles, and the wave drag, associated with each system are computed for various values ofP ₀/Q g h, whereh is the undisturbed depth of water ahead of the wave.The solution obtained reduces to the classical solitary wave of finite amplitude when the applied pressure is everywhere zero.

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Résumé Nous avons calculé les expressions des profils d'ondes solitaires produites par une pression, qui se propagent sur la surface d'une couche d'eau peu profonde avec une vitesseU plus grande que (g h)^1/2. La pression appliquée est nulle en avant de l'onde, elle est une constanteP ₀ en arrière, et entre ces deux régions elle est representée par une fonction cubique. Les profils sont calculés par une methode iterative déjà employée pour des ondes non-linéaires. L'amplitude, le profil et la force ont été evalués pour diverses valeurs deP ₀/Q g h, ouh est la profondeur en avant de l'onde.

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Division of Numerical and Applied Mathematics, National Physical Laboratory.     

Some statistical properties of certain geophysical transport equations

Summary A previously noted analogy between certain transport equations and the heat conductivity equation is further analyzed. It is shown thatPrigogine's nonequilibrium formalism can be directly applied to statistical processes where there is a non-negative constant of the motion. If the total mass (of contaminant, tracer etc.) contained in a fluctuating system is taken as such a constant of the motion, a statistical theory of the corresponding transport process is obtained.     

Cover folding in the Sonmartel Chain (Jura Neuchatelois)

Sonmartel forms part of the anticlinal Cornu-Foulets Chain of the Neuchâtel High Jura. The strata exposed in the district include much of the Malm (Argovien to Purbeckien), the Lower Cretaceous (Berriasien to Hauterivien) and some Tertiary rocks (Siderolithique, Helvetian Miocene). An outline account is given of the Mesozoic formations, the distribution of marker bands being shown on the map (Pl. 1). The structure of the area is discussed in terms of its constituent parts. The folding is concentric but due to erosion-breaching following the earliest movements, subsequent deformation of the Pre- and Post-Kimeridgien rocks differed. The former are gently diapiric, while the folding of the latter is, in part, a gravity effect. Faults normal to the fold axes are present everywhere. They originated as tension cracks but later permitted transcurrent movements. Tear faults are best developed in regions where the trend of the fold axes changes. Thrusts are restricted to the Grand Sonmartel area. The joint systems are thought to result from stresses due to bed-over-bed sliding during the folding. The different types of deformation combine to produce a rhomboidal pattern of dissected cross-folds. Each of these strain-phenomena show that the region has been subjected to stresses of two different orientations, with a third also affecting the vicinity of Grand Sonmartel. These owe their origins to relative movements of basement blocks beneath the area — thrusting during the Post-Stampian phase, the thrusts re-activated as sinistral shears during the Post-Pontian phases when they were joined by conjugate dextral shears. On this basis the Alpine Push theory for the origin of the Folded Jura must be rejected. The Wegmann hypothesis of basement shears accounts best for the structures observed.     

Stratified airflow over one or two hills

Methods for calculating, interpolating and idealising air flow in complex terrain are reviewed. Then the general structure of stratified airflow over a single hill of height H and length L₁ is studied in detail and shown to be determined by the upwind velocity profile, the magnitude of a characteristic Froude number and the dimensions of the hill. Let N(L₁) be the buoyancy frequency upwind at a height L₁, and u_* and U₀ be the upwind friction and mean velocity respectively; then the flow is effectively neutral if u^*/NL₁>1. But if u_*/NL₁>1 and u₀/NL₁>1, the stratification is weak enough to affect the upwind turbulence and velocity profile but not the dynamics of the flow over the hill. If U₀/NL₁ <1 but U₀/NH>1 the buoyancy forces are strong enough to affect the mean flow over the hill but not strong enough to prevent it passing over the top. In this regime the flow is very sensitive to the form of the upwind temperature profile. If U₀/NH>1, much of the flow passes round the hill. A similar classification, with different flow patterns, is appropriate for unstably stratified flows. When the wind is weak enough, local slope winds can dominate. Results from the analysis of these different regimes are described and compared with laboratory of field measurements where possible. It is shown how some of these results can be extended to groups of hills.     

Minor elements in perovskite from kimberlites and distribution of the rare earth elements: An electron probe study

We report REE and minor element distributions for perovskites from seven kimberlites (South Africa and U.S.A.). The REE (1.6–6.3 oxides wt.%) are always strongly light REE enriched, often with Ce > La (chondrite-normalized), and show an expected close correlation with whole-rock analyses. Where examined, perovskite contains far more REE than coexisting apatite, by about an order of magnitude. Calculations indicate that iron is mostly present as Fe³⁺ and is low (1.0–2.9 wt.% Fe₂O₃) compared with perovskite from carbonatite complexes such as Oka (4.4 wt.% FeO [3]). In addition to established Nb (0.3–1.7 oxide wt.%), geochemically interesting elements encountered include Zr (up to 1.5 oxide wt.%), Ba and Sr (up to 0.2, 0.4 oxide wt.% respectively). Specific geological applications suggest a possible genetic link between Wesselton pipe and Benfontein Sills kimberlites, and that carbonate-rich dikes in the Premier mine were derived from kimberlites. The overall similarities with incompatible element-rich titanates in veined mantle peridotites suggest a more direct link between kimberlite magmatism and mantle metasomatism.     

The measurement of watertable levels in structured clay soils by means of open auger holes

In structured clay soils, water levels in open auger holes (dipwells) respond to water movement through macropores and may mask the existence of drier zones either at depth or within peds. Variability between replicated dipwells expresses the small scale variation in the soil, and statements about soil water regimes should be made in statistical terms. Suitably replicated dipwells give sufficiently precise measurements of mean watertable position for studies of soil water regimes.