aM tia

70

Further collections from this deposit, made in 1948, were tested by
R. J. C. Fabry of the Geological Survey, who also found the salt to consist
mainly of potassium nitrate, with lesser amounts of calcium sulphate. Mr.
Fabry noted that the source rock, coated with the salt, contains considerable
free ammonia.

The origin of the nitrate in these salts is an enigma. The beds on
which the nitre is forming, although too fine grained to allow accurate
mineralogical and textural determination, do not appear to be superficially
different from other impure limestones and sericite phyllites both higher
and lower in the section, and fresh specimens of the nitre-bearing rocks
cannot be distinguished (except by taste) from many similar beds that do
not form nitre. The most obvious origin, namely, by the reaction of the
partly decomposed feldspars in the rocks with nitric acid produced by the
decomposition of recent animal deposits, is difficult to accept in view of
the location of the salt on an exposed cliff face, the position and topography
of the cliff itself, the restriction of the salt to a single thin series of beds,
the uniqueness of the deposit in the entire area studied, its persistence
through varying climatic conditions, and the apparent lack of any animal
deposits. Marmot burrows and one large eagle nest were found on the slope
above the cliff, but there is no evidence of nitre forming from the rocks near
these, and the present animal population would appear totally inadequate to
accumulate deposits that could supply sufficient nitric acid to produce the
efflorescence. Nor do the salt-encrusted beds appear to mark the outcrop of
a local water-table, and there is no obvious relation between the distribution
of the salt and the numerous shears and fractures that must serve as
channels for the movement of ground water.

The restriction of the efflorescence to a single thin series of beds, the
release of the salt by weathering over an extended period, and its tendency
to be removed, rather than formed, near fractures controlling water move-
ment, may suggest that the nitrate is an original constituent of the beds.
The beds do not appear to be part of a normal evaporite sequence, for no
halite or gypsum, which would invariably be present in much larger amounts
than nitre, have been identified in the underlying beds, and the selective
leaching of these salts and not of nitre does not seem possible. However,
certain beds in several parts of the Ingenika group release calcium sulphate
(gypsum or anhydrite) upon weathering (See below); and general condi-
tions of aridity at the time of deposition may be indicated by the abundance
of clean quartz-pebble conglomerate, the purity and perfection of rounding
and sorting of some quartzites, the probable mud-cracks in impure lime-
stone on Forres Mountain, and the paucity of fossils. A further possibility
is that the overlying graphitic schists and phyllites, which were probably
originally carbonaceous shales, and which may have accumulated under
putrescent conditions, contained animal nitrate. But there is no indication
of the manner in which the highly soluble nitre could be preserved from
early Paleozoic time to the present.

In a canyon of a creek flowing into Mesilinka River from the north
about 7 miles east of Blackpine Lake, a white crystalline salt has formed
to a depth of about 2 inches on vertical surfaces of sericitic phyllites and
schists, and has accumulated on a few protected ledges to a depth of nearly