Mineralogy of Bearpaw sediments in the South Saskatchewan River Valley
Date
1962-05
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ORCID
Type
Degree Level
Masters
Abstract
The Cretaceous Bearpaw formation in the South Saskatchewan
River valley is a 900-foot sequence of mudstones interlayered with several
thin sandstone units. The diversified mineralogy of these sediments reflects
a complex depositional history, in which sedimentary, volcanic,
and metamorphic source rocks all supplied detritus. A sedimentary source
is suggested by the abundance of detrital chert and by the occurrence of
rounded grains of tourmaline and zircon in the sandstones. Volcanic
rocks supplied montmorillonite, sanidine, and hexagonal biotite flakes.
Further evidence of a volcanic source is found in the recurrence of thin
bentonite seams in the succession of sediments. A metamorphic source is
indicated by a distinctive suite of metamorphic minerals in the heavy
mineral residues.
The postulated source areas of the sediments are all to the
west of the Bearpaw depositional basin. The sedimentary source rocks
are believed to have occupied the site of the Purcell and Selkirk Mountains
in British Columbia. Active volcanoes in western Montana probably
supplied the volcanic detritus. The metamorphic source area was most
likely the Shuswap terrane in British Columbia. Transportation of detritus
from the source areas to the site of deposition was mainly by water, but,
almost certainly, some of the volcanic material was wind-borne.
The results of the mineralogical studies have proved to be of
little use in stratigraphic zoning of the Bearpaw formation.
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Degree
Master of Science (M.Sc.)
Department
Geological Sciences
Program
Geological Sciences