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Field evidence suggests that the Palaeoproterozoic Gowganda Formation in Canada is non-glacial in origin

Molén Mats O.

Geologos

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2021

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Vol. 27, No. 2

73--91

EN

During more than a century since its original identification, the Gowganda Formation in Ontario (Canada) has gradually been reinterpreted from representing mainly subglacial tillites to secondary gravity flow and glaciomarine deposits. The main pieces of geological evidence advanced in favour of glaciation in recent articles are outsized clasts that have been interpreted as dropstones and patches of diamictites in a single small-sized area at Cobalt which is still interpreted as displaying subglacial basal tillites. The present research considers field evidence in the Gowganda Formation in the light of more recent work on gravity flows linked to tectonics. Detailed studies have demonstrated that the clasts which are interpreted to be dropstones rarely penetrate laminae and are commonly draped by sediments the appearance of which is similar to lonestones in gravity flows. The “subglacial area” at Cobalt displays evidence of tectonics and gravity flows, which can be traced from the underlying bedrock, and then further in the overlying sequence of diamictites and rhythmites. The sum of geological features displays appearances at odds with a primary glaciogenic origin, and there is no unequivocal evidence present of glaciation. The data indicate deposition by non-glaciogenic gravity flows, including cohesive debris flows for the more compact units, probably triggered by tectonic displacements.

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Impact of a Thermocline on Water Dynamics in Reservoirs – Dobczyce Reservoir Case

Hachaj P. S., Szlapa M.

Archive of Mechanical Engineering

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2017

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Vol. LXIV, nr 2

189--203

EN

While modeling water dynamics in dam reservoirs, it is usually assumed that the flow involves the whole water body. It is true for shallow reservoirs (up to several meters of depth) but may be false for deeper ones. The possible presence of a thermocline creates an inactive bottom layer that does not move, causing all the discharge to be carried by the upper strata. This study compares the results of hydrodydynamic simulations performed for the whole reservoir to the ones carried out for the upper strata only. The validity of a non-stratified flow approximation is then discussed.

3

Unsteady free convection over a vertical plate subject to a step change of the surface temperature or heat flux in a stratified porous medium

Magyari E., Keller B., Pop I.

International Journal of Applied Mechanics and Engineering

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2007

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Vol. 12, no 2

465-476

EN

The problem of unsteady free convection heat transfer from a one-dimensional (parallel) flow along an infinite verticaI fiat plate embedded in a thermaIly stratified fluid-saturated porous medium is considered. FIows are induced by a step change in surface temperature or heat flux. By a formaI reduction of the corresponding boundary vaIue problems to well known Fourier heat conduction problems, analytical solutions of the Darcy and energy equations are obtained.

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Mixed convection heat and mass transfer in a doubly stratified non-Darcy porous medium

Murthy P. V. S. N., Mukherjee S., Krishna P. V. S. S. S. R., Srinivasacharya D.

International Journal of Applied Mechanics and Engineering

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2007

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Vol. 12, no 1

109-123

EN

The mixed convection heat and mass transfer from a vertical surface embedded in a doubly stratified nonDarcy porous medium have been analyzed. The wall temperature and concentration are constant and the medium is linearly stratified with respect to both temperature and concentration. The external flow is assumed to be uniform. A series approximation is made for both temperature and concentration in terms of the stratification parameter and the solution is presented in both the aiding and opposing flow cases. The flow, temperature and concentration fields are effected by complex interactions among the diffusion ratio Le and buoyancy ratio N and stratification ratio Sr in addition to the flow driving mixed convection parameter Ra/Pe The effect of double stratification of the medium on non-dimensional heat and mass transfer coefficients is discussed.