CLAY MINERALOGY OF PARENT MATERIALS DERIVED FROM UPPERMOST CRETACEOUSAND TERTIARY SEDIMENTARY-ROCKS IN SOUTHERN SASKATCHEWAN

Soils developed from parent materials derived from uppermost Cretaceou s and Tertiary sedimentary rocks have been delineated from those which do not contain any of these younger sediments. The present study was initiated to determine the validity of this delineation. Parent materi als from six locations in southwestern Saskatchewan were collected to determine their general chemical and physical properties. Clay fractio ns from each of these six parent materials were then subjected to deta iled chemical and mineralogical analyses. The two parent materials con taining the greatest amount of post-Bearpaw bedrock sediments (Jones C reek, Scotsguard) were characterized by substantially more organic car bon and less CaCO3. The presence of coal and the absence of carbonates in local bedrocks were considered to be the source of these deviation s. In general, fine clays were comprised of 64-69% smectite, 14-21% il lite and 10-13% kaolinite and coarse clay contained 32-39% smectite, 2 5-34% illite and 11-14% kaolinite. An exception was found in two fine clays which had less smectite but 3-6% vermiculite. Total iron content of the fine clays ranged from 7.16 to 8.11% expressed as Fe2O3. Howev er, only a small fraction of this iron was extractable using the CDB t echnique. There were no substantial differences in surface areas or CE Cs of the clay fractions. Despite minor differences in the chemistry a nd mineralogy of these six parent materials, a separation of the soil associations does not appear to be warranted.