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Downwearing rates (erosion in the vertical plane) were measured with a micro-erosion meter (MEM) in eastern Canada, on an argillacious, sub-horizontal shore platform at Mont Louis in eastern Québec, and on two sloping, basaltic and sandstone platforms at, respectively, Scots Bay and Burntcoat Head in the Bay of Fundy, Nova Scotia. The original data covered a period from 2002 to 2009. This dataset was extended by measurements repeated at surviving MEM stations in 2017, producing records ranging over 9–14 years, depending on when each station was installed. Because of rapid surface downwearing, many of the original MEM stations were inoperable in 2017, especially at Burntcoat Head. Nevertheless, data were obtained from 19 stations at Burntcoat (35% of the 2009 original), 25 at Mont Louis (83% of the original), and 38 at Scots Bay (75% of the original). For the stations at Mont Louis and Scots Bay that were still functioning in 2017, there were no significant differences in rates of downwearing over the shorter (from station installation up to 2009) and extended periods (from installation to 2017). Mean rates of downwearing calculated from all the stations in each area declined through time, however, due to the loss of the more rapidly eroding stations. A simple procedure, which was proposed to compensate for this decrease, produced mean downwearing rates that were broadly similar to those reported over the original measurement period. There were significant relationships between downwearing rates and elevation (R 2  = 0.32) and downwearing rates and rock hardness (R 2  = 0.41) in the extended record at Scots Bay, and a small but significant relationship between downwearing rates and rock hardness at Mont Louis (R 2  = 0.17). Differences in downwearing rates across the platforms suggest that salt weathering and wetting and drying are dominant weathering mechanisms at Scots Bay and Mont Louis. Chemical weathering of the sandstone cementing agent and the premature removal of weathered grains by wave-generated bottom currents may, however, be more important at Burntcoat Head. [ABSTRACT FROM AUTHOR]

Abstract: A mathematical wave and weathering model was used to study the effect of Holocene changes in relative sea level (RSL) on rock coast development. Model runs were made for fast- and slow-eroding coasts in macro- and mesotidal environments using Holocene RSL records from Sweden, northeastern USA, southwestern Britain, central Japan, western Africa, and southern Australia. A further series of otherwise identical runs were made with constant sea level. Changes in RSL determined the amount of time that marine processes have operated within the modern intertidal zone, and rates of wave attenuation and erosion continue to be influenced by subtidal morphology that developed in most areas when RSL was rising to its present level. The model suggested that although tidal range is also important, Holocene RSL changes promoted subhorizontal platform development in Australasia and over much of the Southern Hemisphere, and sloping platforms over much of the Northern Hemisphere. Shore platforms may have been partly inherited from earlier periods in the Holocene, when RSL was similar to today''s. Nevertheless, most platforms continue to be eroded at all tidal levels. Where geological and wave conditions are less favourable, erosion in the lower intertidal zone has essentially terminated in areas where RSL rose to its present position, whereas erosion only occurs today in the lower intertidal zone in places where RSL rose to above its present level in the middle Holocene. [Copyright &y& Elsevier]

Waves were measured over tidal cycles on a sloping, basaltic shore platform at Scots Bay in the macrotidal Bay of Fundy (large tidal range 13. 5 m), and on a horizontal, argillite platform at Mont Louis in Gaspé, Québec (large tidal range 3 m). Video cameras were used to record the height and period of the waves against a series of graduated metal poles anchored along surveyed, shore-normal profiles. Field measurement and theoretical considerations suggest that wave height increases with elevation at Scots Bay, reflecting the occurrence of a gently sloping tidal flat below the midtidal level and higher gradients on the upper than on the lower parts of the platform. Calculated pressures generated within the rock along joints and other discontinuities suggest that wave conditions are suitable for mechanical-wave erosion at Scots Bay. Waves generally break on the low tide cliffat the seaward edge of the platform at Mont Louis, preventing any wave action on the shallow, flooded platform surface behind. During high spring tides, greater water depths allow fairly large waves to cross the platform, but a beach generally protects the cliff foot and, apart from a few upstanding ridges, there is no rock exposed to wave action at the water surface at this elevation. Downwearing by weathering dominates on the horizontal Mont Louis platform, but waves would still attack the cliff during high tides if there were no protective beach, which suggests that the platform may have been cut by waves near the high tidal level and subsequently lowered by weathering to its present elevation. [ABSTRACT FROM AUTHOR]

The morphometry of shore platforms is determined by their morphogenic environments. Gaspá, Quábec is a mesotidal storm wave environment. Shore platforms are cut into steeply dipping flysch, consisting of shale, graywackes, and argillites. The platforms are quasihorizontal, with a low-tide cliff or low-tide ramp at their seaward termini, and a high-tide ramp at the cliff base. Platform gradient is determined by tidal range, mean platform elevation by midtide level, and the cliff platform junction by level of the high tides; lithological and structural factors play a secondary role, Platform width is a function of wave intensity and rock hardness. Most elements of platform morphometry are determined by the elevational distribution of wave action, particularly during storms. [ABSTRACT FROM AUTHOR]

Variations in the width of shore platforms were investigated within southern Wales, Gaspe in eastern Canada, and southern Japan. The strong, positive linear relationship between platform gradient and tidal range implies that platform width may be largely independent of tidalrange, although regional negative correlations between platform gradient and width suggest that platforms become narrower with increasingtidal range. Platform width increases with wave intensity, and the widest platforms are oriented toward the dominant waves. The width of the platforms also decreases with increasing rock dip. A structural classification, based upon combinations of rock dip and strike, relative to the orientation of the cliff face, helped to explain variationsin platform width in Canada and Japan. Changes in structural class induced by variations in coastal orientation may partially account fordifferences in the width of platforms on headlands and in embayments. Platform width is also influenced by the presence and type of cliff-foot deposits. [ABSTRACT FROM AUTHOR]

Ice-directional indicators were compiled from detailed field mapping at the Izok Lake volcanogenic massive sulphide deposit, in the Point Lake region of western Nunavut and eastern Northwest Territories. Cross-cutting erosional relationships and depositional landforms indicate that the Izok Lake area was affected by four ice-flow phases. It is this new glacial history interpretation that is used to explain the gahnite indicator mineral dispersal train down-ice of the Izok Lake deposit as being the net effect of all ice-flow phases. Its fan-shaped morphology is a function of the duration and intensity of two dominant glacial trajectories. Field-based mapping of all glacial-flow indicators are essential, and must be properly interpreted, to detect palimpsest dispersal trains. The resultant dispersal fan serves as a model for future exploration in the glaciated terrain of the north-central part of the Slave Province. [ABSTRACT FROM AUTHOR]