Anisotropy of Magnetic Susceptibility of the Martin Formation, Saskatchewan, and its Sedimentological Implications

The magnetic fabric of the sedimentary rocks of the Precambrian Martin Formation has been investigated in an attempt to delineate paleocurrent directions. One hundred specimens were studied from twelve sampling sites. At most of the sites, a primary depositional fabric was found with a well-marked foliation lying close to the paleohorizontal. This was substantiated by a strongly positive fold-test. Six sites possessed tightly grouped maximum susceptibility axes; a further three sites showed more dispersion but still permitted useful estimation of mean directions of lineation. The directions of paleocurrent deduced are consistent with earlier geological interpretations and suggest that the Martin Formation was deposited in a basin of rugged, block-faulted terrain.

The Alteration of the Pore Spaces in Sandstones

The pore spaces in sandstones are the result of the original depositional fabric and the degree of post-depositional alteration that the rock has experienced. The largest pore volumes are present in coarse-grained, well-sorted materials with high sphericity. The chief mechanisms which alter the shape and size of the pores are precipitation of cementing agents and the dissolution of soluble components. Each process may operate alone or in combination with the other, or there may be several generations of cementation and solution.The scanning electron microscope has ‘been used in this study to reveal the morphology of the pore spaces in a variety of moderate porosity, orthoquartzites.