| Summary: | <p>This thesis attempts to reconstruct the environments in which the potashbearing,
Prairie Evaporite Formation (Middle Devonian) of the Elk Point Basin was
deposited, using preserved primary sedimentary features. Evidence from cores, thin
sections and mine obsetvations indicates that sedimentation was not continuously
subaqueous, but episodic, with periods of desiccation recorded throughout the
formation.</p>
<p>Deposition of the Prairie Evaporite Formation began with a major drop of the
sea-level, leaving most of the basin desiccated and the carbonate mounds of the
underlying Winnipegosis Formation exposed. Fed by seepage through barriers, the
region became a carbonate mudflat environment with patchy brine pools between the
carbonate mounds, and this was succeeded by a salt-pan environment. The Whitkow
Member, which was deposited under these conditions, filled approximately half of the
original relief of the intermound depressions. Subsequently, sea-level rose sufficiently
high to flood the area episodically, resulting in sedimentation of the Shell Lake
Member in intertidal to supratidal environments.</p>
<p>The filling of the basin and concomitant regression of the sea brought the area
under a more continental influence during the Leofnard Member deposition. Except for
the northernmost part, where salt-pan environments persisted, most of the study area
developed into a pericontinental salt lake environment. A considerable amount of
potash may have been deposited with halite syndepositionally, probably during the
peak of the evaporative conditions, and was prone to early diagenetic alteration under
periodic subaerial conditions.</p>
<p>The model presented provides a more dynamic and more realistic picture of the
changing depositional environments. This not only leads to a better understanding of
the deposit itself, but also may help to overcome some of difficulties in potash mining
that relate directly to the conditions during the time of deposition.</p>
<p>Note:</p><p>This thesis contains maps that have been sized to fit the viewing area. Use the zoom in tool to view the maps in detail or to enlarge the text.</p>
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