Occurrences of outcropping marl in the Hand Hills area were first reported by Allan and Sanderson (1945). A photograph in the report shows marl plainly visible at surface along the flanks of the Hills with little or no covering vegetation. At the present the Hills are at a maximum elevation of over 3500 feet within the study area, more than 500 feet above the level of the surrounding plains. Bedrock is at or close to surface along the entire flanks of the Hills and the top is covered by a thin veneer of ground moraine. The bedrock along the lower slopes of the Hills belongs to the Tertiary and Cretaceous Paskapoo Formation. It mainly includes grey and buff siltstone and mudstone. Thin coal beds and laminae are also prevalent within the formation.
The top of the Hand Hills is capped by moderately to poorly cemented gravel beds belonging to the Tertiary Hand Hills Formation. In places, sand is more common than gravel and considerable reworking has taken place. Marl and light colored clays stratigraphically below the gravels are included within the formation. It is supposed that the Hills are present at least partially because of the gravel capping which protected the area from glacial erosion. The thickness of the gravel exceeds 15 feet as indicated by sections in local gravel pits. The marl is over 25 feet thick in places (test holes 64-6 and 64-8, Vanden Berg and Lennox).
The purpose of this study is to report on marl beds close to surface which are easily exploitable by conventional means of excavation at convenient localities. Drilling was therefore confined to depths of less than 30 feet. Twenty-one holes were drilled and samples obtained at regular intervals wherever carbonate percentage values appeared to be high. The higher grade samples were analyzed for calcium carbonate equivalents at the soils laboratory of the Department of Agriculture, Edmonton. An enclosed figure illustrates that those test holes which yielded marl samples that were analyzed and also indicates the area underlain by more than 5 feet of marl at a depth of less than 10 feet. Individual test hole sections and analytical results are given in figures 5 to 25.
Holes 3, 15, 19, 20 and 21 penetrated the most economically significant beds of marl. Grades achieve a maximum of 67 percent CaCO3 and more commonly the values are between 30 and 40 percent. Holes 7, 9, 10, 11, 14 and 16 are worthy of note but samples were not subjected to detailed analyses.
The dry marl is typically soft and flaky ranging in color from light grey to dull orange or light yellow. Thin lenses and laminae of white carbonate salts are common. Moisture contents at the time of sampling were normally less than 15 percent. Sand and granule size ranges typically comprise less than 10 percent by weight of the material. Silt size fractions of those samples analyzed range from 54 to 64 percent and clay from 23 to 36 percent. Particles retained above the No.230 mesh sieve include quartz, quartzite, chert, siltstone, ironstone, gypsum and fragments of weakly cemented marl. Shells and other organic remains are absent with the exception of occasional stubby, tubular structures composed of soft tufa. Small amounts of feldspar, obsidian and other miscellaneous rock and mineral fragments are also present. The nature of the material under high magnification is shown in place II, figure 4.
X-ray diffraction analyses confirm the presence of calcite, dolomite, quartz and feldspar. Dolomite appears to be present in relatively high quantities but analytical results are not available to indicate the exact contents. Clay minerals in the form of montmorillonite, kaolinite, illite and chlorite are verified by X-ray diffraction patterns.
The concentration of carbonates is interpreted to be the result of precipitation of calcite and dolomite from discharging groundwaters. As noted above, residual indications of organic influences appear to be rare and this, together with the fact that higher grade sections appear nearer the flanks of the Hills, would tend to demonstrate a groundwater redistribution of carbonates towards these areas.
Development of the marl is feasible at several places within the study area. Carbonate grades are not as high as could be desired and gravel beds commonly overlie the marl, especially along the edges of the Hills. Commercial exploitation of the gravel and marl simultaneously could be a possible approach to development. Although no estimates of reserves are available, it would appear that tonnages of marl in place are more than sufficient to meet the needs for local agricultural liming purposes.
Holter, M.E. (1974): Marl resources of the Hand Hills area; Alberta Research Council, ARC/AGS Open File Report 1974-36, 42 p.