The Geology of the prairie evaporite formation of the Yorkton area of Saskatchewan
Date
1967
Authors
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ORCID
Type
Degree Level
Masters
Abstract
Beds of grey insolubles alternate with units of clear to
grey halite in the lower two-thirds (about 330 feet) of the
Prairie Evaporite Formation of the Yorkton area.
The upper one-third of the formation consists mainly of
clear to grey, anhedral halite containing one or two potash
zones. In the potash zones, euhedral halite predominates over
anhedral halite.
Three types of sylvite, two types of halite, and two types
of carnallite occur in the potash zones. These mineral types
have characteristic associations.
Clear to milky-white sylvite, with red rims of included
hematite, is the dominant. sylvite of both. potash zones. It is
partly replaced by fine-grained, anhedral, pink sylvite, and
is always associated with clear halite but never with carnallite.
Large-grained, clear to pinkish sylvite, without hematite
rims, occurs in seams in the lower potash zone. This sylvite is
associated with mllky-white halite and both halite and sylvite
are replaced in part by blood-red, anhedral carnallite.
Blood-red carnallite is associated with clear and milky-white
halite in the upper potansh zone of Alwinsal Brewer 9-22
well. No sylvite is present and the origin of the carnallite
is unknown.
The clear halite and milky-white halite of the potash zones,
and the clear to grey halite of the rest of the formation, have
bromine contents lower than, as well as within, the range for
primary halite crystallized from present-day sea water. Values
lower than the primary range suggest that solution and redeposition
of halite has occuried.
Red-rimmed sylvite and large-grained, clear to pinkish sylvite
have similar bromine and rubidium values. Rubidium values,
below 0.0017 wt. per cent suggest these sylvites formed from
pre-existing sylvite; values greater than 0.0020 wt. per cent
suggest they formed from pre-existing carnallite.
In township 23, range l W. 2 Mer., and in townships 28 and
29, ranges 6 W. 2 and 7 W. 2 Mer., solution of the Prairie Evaporite Formation and collapse of formations below the First
White Speckled Shale has occurred. These solution areas underlie
"lows" on the Paleozoic erosion surface. Locally, the
Paleozoic erosion surface has as much as 550 feet of topographic
relief. Blairmore and Lower Colorado sediments are
300-400 feet thicker on the sites of erosional "lows". The
erosional "lows", with their thick Cretaceous sequences, are
more extensive areally than the solution channels. In seismic
investigations, these thick sequences of low velocity sediments
cause apparent structural lows, also more extensive
areally than actual lows caused by Prairie Evaporite solution.
These apparent structural lows, however, may be misinterpreted
as signifying areas of Prairie Evaporite solution
and areas containing normal potash zones may be overlooked.
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Degree
Master of Arts (M.A.)
Department
Geological Sciences
Program
Geological Sciences