Next above the Grinnell is a thick limestone formation which, because of
its weathered buff color, stands out in sharp contrast to the red beds
upon which it rests. It is the greatest cliff-maker in the park and in
several places its entire thickness of 4,000 feet may be exposed in a
single nearly vertical cliff. Since it is younger than the three
preceding formations, it is confined mainly to the higher elevations,
capping many of the loftiest peaks within the Lewis and Livingstone
Ranges. In the Many Glacier area such peaks are Mount Gould and the
Garden Wall, Mounts Siyeh, Grinnell, Allen, Wilbur, and Henkel. A number
of others, including Little Chief, Jackson, Gunsight, Fusillade,
Going-to-the-Sun, Piegan, Pollock, Cannon, and Heavens Peak, are visible
from Going-to-the-Sun Highway. The huge peaks--Kinnerly, Kintla, Carter,
and Rainbow--which stand guard at the heads of Kintla and Bowman Lakes
are composed of the Siyeh. The list also includes Cleveland, highest and
largest of all.
[Illustration: ALGAE COLONIES IN SIYEH LIMESTONE NEAR GRINNELL GLACIER.
(DYSON PHOTO)]
[Illustration: GENTLY TILTED STRATA OF THE SIYEH FORMATION IN GRINNELL
MOUNTAIN.
(DYSON PHOTO)]
Within the Siyeh there is a bed, averaging about 60 feet thick, composed
almost entirely of fossil algae which apparently formed an extensive
reef or biostrome on the floor of the shallow Belt Sea. The algae
colonies are in the form of rounded masses up to several feet in
diameter and bear a crude resemblance externally and internally to a
head of lettuce or cabbage. Geologists know these algae by the genus
name Collenia. Because of the rounded and smoothed surfaces on these
colonies, mountain climbers frequently find the reef difficult to cross.
It appears as a distinct light gray horizontal band on the east face of
Mount Wilbur about midway between the base of the cliff and the peak's
summit, where it can easily be seen from Many Glacier Hotel and
Swiftcurrent Camp. It is also discernible on the Pinnacle Wall above
Iceberg Lake and in Mount Grinnell. The Swiftcurrent Pass trail crosses
it just east of the pass, and it is also exposed along Going-to-the-Sun
Highway below the big switchback on the west side of Logan Pass where
attention is directed to it by a sign. Unweathered portions of the reef
rock are light blue. A similar but thinner reef outcrops at Logan Pass
near the start of the Hidden Lake trail. Although most of the fossil
algae occur in the Siyeh they are present in the younger formations and
also in the Altyn. Other than algae the only undoubted fossils of the
Belt series within Glacier National Park are burrows probably made by
worms. They are rare and are restricted mainly to the Siyeh formation.
[Illustration: FOSSIL ALGAE IN SIYEH FORMATION, HOLE-IN-THE-WALL BASIN.
(THE ROCK BOOK BY C. L. FENTON AND M. A. FENTON, DOUBLEDAY AND CO.)]
At the top of the Siyeh are several hundred feet of sandy and shaly
beds, mostly reddish in color, grouped by some geologists into a
distinct formation known as the Spokane. At Logan Pass it is about 700
feet thick and is well exposed in the lower parts of Clements and
Reynolds Mountains, and at the site of the former "Clements" Glacier.