Excerpts from two books regarding fish and geology of the Poplar River
Excerpt from:
Chapter VIII – Fish and Game Along Highway No. 1 by Thaddeus Surber, Game
and Fish Department, in Schwartz, G.M. 1925. A Guidebook to Minnesota
Trunk Highway No. 1. University of Minnesota, Minnesota Geological Survey
Bulletin No. 20. 128 pp.
“The Poplar River, which enters Lake Superior at Lutsen, is fed by an enormous number
of lakes and has so much dead water that during summer months it affords no suitable
waters for trout, except for two miles above Lutsen, where it is spring fed. At certain
times good catches of trout, both brook and brown, are taken between Lutsen and the old
mill three miles above, but this stream cannot be relied on for trout fishing. The lakes
north of Lutsen furnish excellent angling for great northern pike and other fishes of that
character and will repay a visit for the observation of big game which will be referred to
later on. Some distance east of Lutsen and about four miles west of the Cascade, a small
stream crosses the road which might be ignored by the casual as too small for
consideration as a trout stream. This is known as Spruce Creek and is one of the best
small streams along the north shore for brook trout, but is a very difficult stream to fish
because it is small and passes through very heavy forest with dense undergrowth. The
Cascade is next reached, being the last stream of any size between Two Harbors and
Grand Marais. This is perhaps one of the most noted trout streams on the north shore and
affords very fine trout fishing to those who care to wade and fish the stream as it should
be fished...” (p. 99.)
Excerpt from:
Grout, F.F., R.P. Sharp, and G.M. Schwartz. 1959. The Geology of Cook
County Minnesota. University of Minnesota, Minnesota Geological Survey
Bulletin No. 39. 163 pp.
Chapter 3. Glacial Geology
The Glacial Tills
“Superior Lobe Till. The Superior Lobe moved west-southwestward in the Lake
Superior trough and shoved outward three to five and a half miles beyond the present
lake shore in Cook County. In the course of this study, the northern limit of its red clay
till has been traced from the western border of the county east-northeast to the vicinity of
Mineral Center (Plate 1). {Boundary is about three to four miles inland from Lake
Superior. The boundary shown in the Plate crosses the Poplar River about four miles
from the lake.} Red clay till is best seen in the broad open valleys... Red lake clay was
deposited in many parts of the area covered by the Superior Lobe, and every exposure of
red clay-rich material raises the problem of distinguishing between lake clay and till.
Tills of this hue are usually described as red, although most are actually pink. Near its
base and along its northern edge, this till sheet is also brownish pink and even brown in
some exposures owing to incorporation of brown lake clays or Rainy Lobe till. In its
most typical form, Superior till is compact and contains 60 to 80 per cent red clay. In
addition to a clay matrix, discrete fragments of lake clay are also incorporated...
At Big Bay and on the Poplar River, Superior Lobe till is calcareous. Its clay matrix
also displays a “nutty” structure, breaking out, when dry, in angular fragments one half to
one inch in size. The weathered profile is mostly 16 to 18 inches thick and consists of 6
to 12 inches of dark humic soil at the top, underlain by brownish leached and oxidized
material. This modest depth of alteration is attributed more to impermeability of the till
than to a short period of weathering. Where calcareous the till is leached to a depth of
two and a half feet on the crest of a well-drained ridge.
In most exposures the Superior Lobe till is 5 to 15 feet thick, but locally as much as 25
feet has been seen. The Poplar River flows in a deep rock gorge in Sec. 21, T. 60 N., R. 3
W., and red clay till is exposed on the east wall up to 250 feet above the floor of the
gorge (Figure 18). {Figure 18 is a cross-section diagram from west to east with the
Poplar River at the west edge at 1045’ and the east edge showing the upper edge of the
red clay till with bedrock at 1350’. It shows a gravel formation above the red clay
beginning at 1160’ up to 1234’ with a road cut shown at that elevation. The valley wall
from the river to 1160’ is shown as red clay till. Once the surface elevation goes past
1160’, bedrock is shown at 1045’ and on up to 1350’. So, the till is shown as being up to
about 100’ thick} This relation and remnants of high terrace gravel suggest the
possibility that a preglacial rock gorge was filled to a depth of 200 or more feet with red
clay till.”
Glacial Lake Deposits
“Parts of Cook County were occupied by lakes lying along the margins of the ice lobes,
from which they received meltwater and debris. Their existence is demonstrated
primarily by beds of red clay, locally calcareous, and beds of brown non-calcareous clay,
silty clay, and silt, in all instances older than or locally interbedded with the basal red
clay layers. Such lake beds are exposed principally in the..., in the lower valleys of the
Poplar, Onion, and Temperance rivers, and in the land bordering Lake Superior (Plate
1).”
“In the southwestern part of the county, lake beds are exposed in the valleys of the
Poplar, Onion, and Temperance rivers on the northern side of the Coastal Hills (Plate 1).
{The Plate shows the glacial lake bed on the Poplar as beginning at about elevation
1234’ and about at the upper falls. It stays fairly narrow for about a mile before
widening out to about three miles wide to the west of Caribou Lake.} For the most part
these accumulations are thin and consist entirely of red clay... The upper limit of lake
beds is 1309 feet on the Poplar River, 1250 feet on the Onion River, and 1240 feet on the
Temperance River. These elevations are above the known shorelines of Lake Duluth at
these places, so the beds are ascribed to marginal lakes formed when the valley mouths
were dammed by the Superior Lobe. Meltwater carried red debris north into those lakes
that formed after some recession of the ice had occurred, for the beds lie largely in areas
formerly covered by the Superior Lobe...
The land immediately bordering Lake Superior was submerged by Lake Duluth and its
successors, and within this area are scattered deposits of red lake clay, usually one to ten
feet thick.
The high content of red lake clay in the Superior Lobe till indicates that the ice moved
over areas mantled by lake beds,...” (pp. 63 – 66.)
Townships 59 and 60 North, Range 3 West
(Plate 13)
(p. 148)
“...The southern two thirds was covered by the Superior Lobe and has much red clay till.
On the Poplar River in the southern part of Sec. 21 is an exceptionally thick deposit of
red clay till in a preglacial rock gorge...”
(Note – Figure 18 and excerpts of Plates 1 and 13 are included in the attached PDF object
on the next page. Double click on the object to open the PDF file to see the additional
pages.)