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Investigation of some physical and chemical properties of the stony marine clays in the lower Fraser Valley area of British Columbia Ahmad, Nazeer

Abstract

Some of the physical and chemical properties of the stony marine clays recently described by Armstrong and Brown in the Lower Fraser Valley area of British Columbia were investigated. Mechanical analysis of samples taken from four depths from the Murrayville, Jackman and Lehman sites showed that the amount of clay material less than 2 microns in diameter increased from a range of 4 to 18 per cent in the surface foot to 20 to 40 per cent at a depth of 18 feet. The silt and fine sand material varied conversely, the surface foot containing from 77 to 96 per cent while the material from; 18 feet contained from 61 to 68 per cent. The textural classification of the samples ranged from sandy loam to silt loam in the surface, and from loam to clay loam at depth. The material collected from the fourth site, Haney, had a somewhat higher content of clay material, 42 to 46 per cent, and a smaller percentage of coarse skeleton, fine sand and silt. Samples from the surface were not available, but the textural classification at depth was clay to silty clay. The mechanical analysis and other physical and chemical information support the suggestion that the material at the Haney site differs significantly from that at the others. The apparent and real densities of the material at all four sites increased with depth, the range in apparent density being from about 1.1 to 1.4 at the surface to 1.4 to 1.8 at 18 feet. In the case of the real density the range was from about 2.69 on the surface to 2.74 to 2.82 at depth. There was a corresponding reduction in total porosity from about 60 per cent of the soil volume at the surface to 35 per cent at depth. The moisture tension determinations showed that to a large extent this reduction was at the expense of large or macro pores. Hydraulic conductivity determinations with soil cores showed that close to the surface the material is reasonably permeable to water, but that it decreases to a very low value at depth. The cation exchange capacity of the material was found to vary considerably ranging from 7 to 23 milli-equivalents per 100 gm. In general the deeper samples gave somewhat lower and more constant values than the surface, ranging from 10.2 to 16.5 milli-equivalents per 100 gm. Reaction and exchangeable cation determinations showed that at the one-foot depth the material is acid, pH 5.0 to 5.8, and from 40 to 73 per cent base saturated. However, the reaction and degree of base saturation was found to increase with depth until in the deeper samples the reaction ranged from pH 7.4 to 9.4> and the clay material was completely base saturated. Highly significant quantities of exchangeable sodium and free lime were found in all the deep samples. Material with effective diameter less than 2 microns was separated from all samples, and from the 18-foot samples less than .5 micron material as well. The free-oxide content of the less than 2 micron material was found to range from about 8.7 per cent at the surface to 3.9 per cent at depth. Sodium carbonate fusion analysis showed the fine material to contain from 50 to 60 per cent silica, and have a high silica-sesquioxide ratio ranging from 3.02 to 6.41. The fine material was found to contain significantly more total magnesium and potassium at depth. These results, together with the high exchange capacity and dehydration values obtained suggest that the fraction smaller than .5 microns contains a significant amount of clay material of the montmorillonite, illite, or hydrous mica types, and that the proportion of this material is somewhat higher at the surface.

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