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1. Investigations of the Sedimentology and Stratigraphy of the
Sediments at the Cleo-Meyer Farm in Little Falls, MN
Lori McDonald
EAS 423 Fall
Dr. Kate Pound
3. Abstract
Surficial sediment in central Minnesota is dominated by glacial and glacio-fluvial deposits. These
sediments are associated with landscape features that record the advance and retreat of ice
lobes into Minnesota during the Pleistocene. Sedimentology is the study of the composition of
sediments such as sand, silt and clay and the processes that lead to their deposition.
Stratigraphy is the study of the arrangement of sedimentary layers in a given area. The
investigation of the sedimentology and stratigraphy of a glaciated area such as the Cleo-Meyer
farm near Little Falls Minnesota reveals the local glacial history. The outcrop area of the Cleo-
Meyer locality investigated is located in the Little Falls East quadrangle of the E ½ of the NE ¼ of
the NE ¼ of T40N R32W S27, with a base elevation of 1,250 feet above sea level. The largest
wall of the main gravel pit was the primary focus of this investigation. At this location, every
unique sedimentary layer was measured and recorded. Samples of each sedimentary layer were
gathered in the field and analyzed in the lab to determine the color, size distribution of the
grains, and relative percentages of sand silt and clay. The 1-2 millimeter grain size portions were
sorted into different lithologic categories. Once they were sorted, the grains were counted and
the relative percentage of each lithology represented was recorded. When combined, these
data allow for the stratigraphic correlation of the units present at each different location to its
corresponding till. The sediments present at the main section of the Cleo-Meyer location were
determined to be outwash and till deposits associated with either the St. Croix or the Wadena
moraines, with incorporated Superior lobe till and outwash material. These sediments were
deposited in sequence in a variety of different glacial processes associated with the ablation of
the ice lobes that once covered this area of Minnesota.
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4. Introduction
The surficial geologic morphology of central Minnesota is dominated by glacial deposits
and glacially related processes; which has resulted in a glacially influenced and sculpted
landscape. (Hobbs, 2009) A provenance study is defined as the science that deals with the
description, classification, and origin of sedimentary rock. It is the study of modern sediments
such as sand, mud (silt) and clay, and the processes that result in their deposition. (Knaeble,
1996) Sedimentologists apply their understanding of modern processes to interpret geologic
history through observations of sedimentary rocks and sedimentary structures. In the area of
the Cleo-Meyer locality at the Little Falls East quadrangle of the E ½ of the NE ¼ of the NE ¼ of
T40N R32W S27, a provenance study was conducted on the glacial sediments that were found to
be present. The investigation of the sedimentology and stratigraphy of a glaciated area such as
the Cleo-Meyer farm near Little Falls Minnesota reveals the local glacial history of the area. It
also broadens our understanding of the different processes formerly present there that shaped
the land as we know it today.
Location
The Cleo-Meyer pit is located in the Little Falls East quadrangle of the E ½ of the NE ¼ of the NE
¼ of T40N R32W S27, with a base elevation of 1,250 feet above sea level.
4
5. Figure 1: Glacial sediments exposed at the Cleo-Meyer farm. Measured section of the study
area is 54 feet high from top of tape measure to the bottom (vertical line located in center of
photo). Left photo is original outcrop. Right photo has overlying color interpretation of the
stratigraphy of the different units observed there.
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6. Previous Investigation
Deposition of glacial material from the retreat of these massive ice sheets in differing
environmental conditions resulted in unique sedimentary deposits. These deposits are classified
according to the environment in which they were deposited. Some of the different
classifications of glacial sediments considered in this investigation include:
• Glacial till
• Glacial fluvial outwash
• End moraines
All glacial deposits, including end moraines, have two distinct sedimentary types; glacial till, and
fluvial outwash.
Figure 2: Different glacial zones in which sediments are deposited.
Glacial Till: Till is material that is directly deposited by a glacial ice. Till includes a mixture of
undifferentiated material ranging from clay size to boulders. This is the usual composition of a
moraine. (Knaeble, 1996)
Glacial fluvial outwash: Fluvial and outwash sediments are deposited by water. These deposits
are usually stratified or sorted by the action of running water from the melting of a glacier. In
contrast to till, outwash displays layering that is a result from sorting and deposition by running
water. Crossbedding is a common sedimentary feature found in outwash. Till and outwash are
6
7. generally found in close association to one another because outwash is formed by meltwater
streams as they wash out the ice margins. (Kaneble, 1998)
End Moraine: End moraines form along the outer edge of an ice sheet and mark the extent of
the ice advance. These features usually appear as massive linear mounds of till. In this area of
Central Minnesota, one of the best examples of an end moraine deposit is found at the Powder
Ridge ski area in Kimball. This is part of the St. Croix moraine located in central Minnesota.
Minnesota Historical Geology: The general surficial geologic history of Minnesota is
dominated by glacial events that occurred in the Pleistocene epoch, more specifically the
Wisconsin Age. During this time the Laurentide ice sheet covered much of northern America,
and Minnesota was located at the edge of the sheet. (Ojakangas, 1982)
Figure 3: Furthest extent of the Laurentide Ice Sheet advance
Glacial Advances: Throughout the Quaternary there were six major glacial ice advances, each
bringing with it a unique or “typical group” of sediments derived from the rocks and landforms
the ice sheets moved over as they advanced and retreated over different source areas.
Wisconsin age glaciation in Minnesota was dominated by four lobes that extended from the
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8. Laurentide Ice Sheet of Canada. Over the course of about 65,000 years, these lobes advanced
and retreated several times. During a glacial advance, a glacier will incorporate bedrock and
existing sediments from the local environment into the ice. Glacial ablation, or melting, deposits
the incorporated sedimentary material in various ways according to the location of the sediment
on the retreating glacier. Through investigation of the differences in the lithologies of the
glacial sediments throughout the state, the ice lobes that deposited the landform can be
identified.
Figure 4: One of the last glacial advances in Minnesota during the Wisconsin age. This image
shows the ice coverage of the Des Moines lobe and its sub-lobes.
The Rainy and Superior lobes reached their maximum extent approximately 20,500
years ago. (Norton, 1983) During the last advance of these lobes a coarse-textured till of basalts,
gabbro, granite, iron formation, red sandstone, slate, and greenstone was deposited. This
advance resulted in the St. Croix moraine which extended from Walker to St. Paul. (Norton,
1983) The surficial geologic units associated with the area of the Cleo-Meyer Farm include the
St. Croix moraine association, deposits associated with the Wadena lobe, and outwash
associated with St. Croix moraine. (Hobbs, 1983) The St. Croix moraine association is a till that is
mostly end moraine material. It is composed mostly of sand and gravel, with a sandy and stony
texture. The St. Croix Moraine also has units of parallel ridges that appear to be large scale
thrust features. (Knaeble, 1998) Near the moraine it locally includes calcareous drift
incorporated from the underlying Wadena lobe. The Superior lobe is also well known for its ice-
marginal thrust blocks in the St. Croix moraine in the Stearns County area. (Knaeble, 1997)
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9. Hypothesis
Because of the surficial units associated with the area investigated, it is hypothesized
that the sediments seen at the Cleo-Meyer farm will be consistent with the St. Croix Moraine
association, with Superior lobe thrusted material incorporated in it. Also, because of its relative
proximity to the Mississippi River, it is hypothesized that along with the St. Croix Moraine
association, there will be significant stream deposits found there that are either directly
associated with the Mississippi River, or one of its paleo-tributaries.
Materials and Methods
Materials used in this investigation include:
• Tape measure
• Sample collection bags
• Munsell Color chart
• Sodium pyrophosphate
• Glass beakers
• Scale
• Hydrometer
• Graduated cylinders
• Blender
• Hot plate
• 0.63mm, 1mm, and 2mm mesh sieves
• Ceramic dishes
• Petrographic microscope
9
10. The study section was measured with a tape measure by placing it at the top middle of the
outcrop and pulling it down to the base. The entire section measures fifty-three feet high, with
approximately a sixty-degree angle from bottom to top. Eleven unique sediment deposits were
observed at this location of the Cleo-Meyer gravel pit, each loosely consolidated to
unconsolidated. Each unique sedimentary layer was described and its characteristics recorded.
Samples were taken from each layer and brought back to the sediment lab for analysis. Dry
color was determined for each sample using the munsell color chart. Approximately 50 grams of
each sample was weighed out and placed into a clean glass beaker. A solution of 150ml sodium
pyrophosphate was added to each sample to disaggregate clay material present. After soaking
for 24 hours, the sediment and solution was stirred to remove air bubbles and allowed to settle.
Following this process, a hydrometer reading was taken for each sample using a graduated
cylinder containing 1,000ml of sodium pyrophosphate. After the sediment had settled, the
solution was transferred to a blender and was agitated approximately one minute to further
disaggregate any clay present. Each sample was then transferred into a large graduated
cylinder, and filled to 1,000ml with water. To determine satisfactory sediment to water ratio
had been achieved for the removal of clay particles, additional hydrometer readings were taken
at one hour intervals. At this stage the wet color is also recorded. The sediment was then
strained through a 0.063mm sieve and dried on a hot plate for approximately three hours. Once
dry, the 0.063mm, 1mm, and 2mm mesh sieves were used to separate grain sizes. Following
agitation, the contents of each sieve was transferred into separate envelopes which were
labeled, weighed, and recorded. Weight percentage was calculated and the 1-2mm size grains
are set aside for grain counting.
The 1-2mm fraction for each distinct layer was placed into a black tray. Individual sediment
grains were separated into a ceramic dish with 12 different partitions. The grains were
differentiated into color categories and sorted according to lithology using a petrographic
microscope. Grain assemblages for each layer were glued onto a numbered slide. They were
then analyzed, counted, and recorded. A grain count worksheet was used with this method to
determine percentages of each typical grain type represented in the 1-2mm analysis.
10
11. Figure 6: Grain count worksheet used for classifying 1-2mm grains into Precambrian, Paleozoic,
and Cretaceous groups based upon individual grain lithology. This is used to determine
sediment provenance.
Figure 7: The Munsell soil color chart for color differentiation of soil and sediments.
11
12. Table 1: Descriptions and field notes of all the sedimentary units observed at the large pit at the
Cleo-Meyer Farm.
Sample Thickness Field Description Dry Color Wet Color
CM 1-10b 52 – 53 ft Top layer. Sample taken to the north (off to
the side) of the middle of the section. Dark
reddish-brown silty particles mixed with
coarse sand
7.5 YR5/6 7.5YR 6/8
CM 1-10a 52 – 53 ft Top layer. Sample taken from the middle of
the section near the tape measure. Light tan,
very fine sand to silty particles mixed with
larger pebbles that have low sphericity, but
are rounded.
10YR 6/4 10YR 7/8
CM1-9 48 – 52 ft Called “the holey layer” near the top of the
outcrop. Medium grey. Made of very fine clay/
silty particles intermixed with fine slightly
angular sand. Compacted, hard, very porous.
Abundant holes in this layer made by birds or
small animals.
10YR 6/3 2.5YR 5/4
CM 1-8 47 – 48 ft Darker brownish-red unconsolidated medium
grained sand. Composed of more angular
fragments.
7.5YR 4/4 7.5YR 6/8
CM 1-7 36 – 47 ft Light reddish-tan, medium to fine sand. Loose
unconsolidated, horizontally bedded.
10YR 6/4 2.5Y 8/4
CM 1-6 35 – 36 ft Well compacted, red colored very fine sand.
Medium to thin bedding with coarse laminae
seen in the sandstone in the field.
10YR 5/6 7.5YR 5/6
CM 1-5 32 – 35 ft Very tightly compacted, not lithified,
composed of very fine clay and silt particles.
Cohesive clay-like texture, would stick
together when squeezed. Alternating light and
dark tan horizontal bands seen in outcrop.
Called “the green layer” in the field because of
small green plants/ moss growing out of it.
2.5Y 7/4 NA
CM 1-4 30 – 32 ft Very poorly sorted, thin conglomerate layer
composed of very large pebble to cobble sized
clasts in a medium to fine sandy matrix. Larger
clasts are composed of rocks such as
amygdaloidal basalt and rhyolite. Overall dark
reddish-brown color.
7.5YR 5/4 NA
CM 1-3 4.4 – 30 ft Large massive very loosely to unconsolidated
sand with large scale crossbedding features
seen in the field. Medium to fine sand, well
sorted. Dark reddish tan color. “ The big
layer”
5YR 6/3 NA
CM 1-2 2 - 4.4 ft Fine-very fine sand, well compacted, slightly
cohesive but easily broken up. Well defined
thinly laminated crossbedding in outcrop.
Sequence becomes more progressively coarse
upwards.
10YR 5/4 10YR 6/8
CM 1-1 0 - 2 ft Bottom layer of the section. Coarse-very
coarse sand with pebble sized grains
incorporated that were rounded with low
sphericity. Some crossbedding seen in
outcrop.
10YR 6/4 10YR 8/4
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13. Results
The 1-2mm grain size is considered to be very coarse sand. It provides critical information
on sediment provenance, and is very useful in distinguishing among till units and for
determination of ice-flow direction. The method used in this study for classifying individual
sand grains grouped them as precambrian, paleozoic, or cretaceous.
Grain Analysis
Precambrian: Grains are grouped into light, red, and dark color categories. The light category
consists of granite, gneiss, quartz, and quartzite.
The red category includes iron, rhyolite, agate, arkose sandstone, and quartz arenite.
The dark category of the Precambrian encompasses dark mafic rocks and other dark igneous or
metamorphic rocks.
13
14. Paleozoic: The Paleozoic grouping includes carbonate, chert, sandstone, and shale. The only
grains seen in this study for this category were cherts and Paleozoic sandstone
Cretaceous: Grains grouped as Cretaceous include grey shale, speckled shale, limestone,
inoceramous shells, pyrite, and lignite. No cretaceous sediments were observed in this study.
Sedimentology Interpretation
Triangular Diagram Analysis: A triangular or ternary diagram is a graphical tool used to classify
different properties in geologic classification. In doing a triangular diagram analysis of each of
the layers investigated in the 1-2mm grain analysis, there are three different plots
differentiating Precambrian, Cretaceous, and Paleozoic rock types, comparing the sediments
investigated with known tills in the Central Minnesota region.
Figure 8: Different triangular diagrams used in soil and sediment analysis
Triangular diagram A differentiated total percentages of Precambrian versus Paleozoic and
Cretaceous grains. CM 1-1, CM 1-8, and CM 1-9 all were plotted on the diagram in the Shooks
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15. till range. CM 4-1 was plotted as First Red till. CM 1-10a and CM 1-10b were plotted in the
Wadena Till range.
Triangular diagram B and triangular diagram C compared different groupings within the
Precambrian category based upon relative percentages of granitic, quartz, and dark, red, or
sandstone grains present. In Triangular diagram B, the grain percentages plotted CM 1-1, CM 1-
9, and CM 1-10b in the range of the First Red till. CM 4-1 is plotted as Eagle Bend till, and CM 1-
10a is plotted in the range of Pierz till.
Triangular diagram C plotted CM 1-1 as St. Francis till and CM 4-1 as First Red till. CM 1-8
and CM 1-9 were plotted as being in the range of Wadena and Pierz till. CM 1-10a was plotted
as Eagle Bend till and CM 1-10b was plotted in the range of Sauk Center till.
Stratigraphic Interpretation
CM 1-1: In investigating the physical structures of the layers in outcrop, the bottom layer of the
section is 2 ft thick. The larger are pebble sized, or about the size of a golf ball and are present
in a matrix of smaller sand sized material. This material was unsorted and a good example of
what we would expect from glacial till. The 1-2mm grain analysis showed that there were 99%
Precambrian grains, and 1% Paleozoic.
CM 1-2: The second layer from the bottom was also approximately 2 feet thick and is composed
of very fine sand with cross bedding laminations that can be seen in the middle of the section.
This stratum also seems to have a coarsening upwards sequence, with larger clasts towards the
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16. top of the sequence. There also appears to be some imbrications of the larger clasts seen in this
section. This section also had a 1-2mm grain analysis of 99% Precambrian grains, and1 %
Paleozoic. This section is interpreted as being related to a glacial outwash event.
CM 1-3: The third layer was the largest and most massive in the entire cross section. This
section is 25.5 feet thick, and is composed of very fine to medium sand particles. Because the
sand in this section was smaller than the 1-2mm fraction, a 1-2mm analysis was not conducted.
However, because of the large scale crossbedding and small scale laminations seen in the
sample, this layer was interpreted as being deposited by glacial meltwater as glacial outwash in
a large or more prolonged melting event, with water velocities at slower speeds to be able to
deposit smaller sized particles.
CM 1-4: The fourth layer is located directly on top of the massive cross bedded layer. It is a very
thin lens of pebble conglomerate. This very poorly sorted layer consisted of clasts that ranged
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17. from pebble (golf ball) size to very fine sand. The 1-2mm grain analysis of this layer showed
100% Precambrian grains, with a majority of them being associated with the superior till.
CM 1-5: The 5th
layer in the section was nicknamed “the green layer” because it appeared to be
green when standing at a distance describing the section. However, when it was examined
more closely it was found to be composed of very fine clay particles that held enough moisture
for small green plants to be growing out of it. The clay in this layer is very thinly laminated and
is 3 ft in total thickness. The sediment in this layer was also too small to conduct a 1-2mm
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18. analysis.
CM 1-6: The sixth layer in the section was approximately 1 ft in thickness. Its composition is red
colored, very fine sand that is very thinly bedded in horizontal layers. The sediment in this
section also was too small to conduct a 1-2mm analysis, but because of the thin layering and red
color it is interpreted as being a glacial outwash from the rainy or superior lobes.
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19. CM 1-7: The seventh layer in the section is 9.5 feet thick and was composed of light reddish tan
medium to fine sand. This layer also displayed horizontal bedding features that can be
associated with glacial outwash deposits. A 1-2mm analysis could not be conducted due to
small grain size.
CM 1-8: The eighth layer in the section was composed of dark reddish brown medium to course
sand. It averages approximately a foot in thickness; however, there are abundant channel scour
and fill patterns seen in the section. Analysis of the 1-2mm grain portion revealed 100%
Precambrian sediment with most of the lithologies represented by typical rocks from the
superior lobe.
19
20. CM 1-9: The ninth layer was approximately 3.5 feet thick and composed of mostly clay and silt
particles intermixed with fine to medium sized sand. This layer was nicknamed named “the
holey layer” because of the presence of bird and insect holes in it. The 1-2mm analysis revealed
that there were 98% Precambrian grains, with 2 % Paleozoic.
CM 1-10a/ CM 1-10b: The top layer in the section was divided into two different sections, one
to the right of the tape measure and one to the left. Section 10a was the section to the right of
the tape measure. It is composed of very poorly sorted till material with the largest clasts being
pebble (golf ball) sized. The 1-2mm analysis of this material showed that there were 99%
Precambrian sediments, with 1% Paleozoic. The top layer to the left of the tape measure was
labeled as section 10b. It is composed of dark reddish brown unsorted till material ranging from
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21. very fine silty particles to large pebble to cobble clasts. The 1-2mm grain analysis of this section
also revealed 99% Precambrian sediments, with 1% Paleozoic.
CM 1-10a
CM 1-10b
Conclusions
The sediments present at the main section of the Cleo-Meyer location are outwash and till
deposits associated with the St. Croix and Wadena moraines. Each of the sedimentary layers
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22. that were able to be investigated were found to contain Precambrian material that originated
from the rainy and superior lobes. All of the 1-2mm grain analysis contained 99-100%
Precambrian sediments, with 1% or less Paleozoic sediments, and 0% percent cretaceous
sediment.
Comparing the results from triangular diagrams A, B, and C to the expected assemblages
associated with the St. Croix moraine found in the Geologic Atlas of Stearns County, the results
are inconclusive. None of the tills plotted on diagrams A, B, or C were plotted as the same till on
any of the consecutive diagrams. These results could have been skewed in many different ways.
One possible reason for the inconclusiveness of these diagrams is that these sediments were
deposited in conditions that were highly influenced by fluvial processes. Grains present in test
tills for the analysis done by the Stearns County geologic atlas could have been taken from sites
that were not as affected by these processes. Grains removed or dissolved in the presence of
moving water would skew the results of these diagrams, making their validity questionable.
Also, because the St. Croix moraine sediments in Stearns county commonly have been
associated with thrusted Superior Till sediments, that could have been another factor in the
weak triangular diagram results.
The percentages of 1-2mm grain lithologies present was consistent with a majority of
Wadena Lobe sediments, with some incorporated Superior lobe till and outwash. Typical St.
Croix end moraine sediment was largely unrepresented in this measured section. These
sediments were deposited in sequence in a variety of different fluvial glacial processes
associated with the ablation of the ice lobes that once covered this area of Minnesota.
Future Research
Future research would include developing a more comprehensive classification scheme for
1-2mm grains. Many problems were encountered when trying to classify grains that did not fit
22
23. into the current grain classification chart. Examples of problem grains were rose quartz, clear
quartz sandstone, tan to pink sandstone, and pink feldspar grains.
There is no clear current category that these grains can be classified into. Filtering these
results into categories that had the “best fit” could ultimately alter the results and
interpretations of the source of the sediment represented in the 1-2mm grain fraction.
References
23
24. Danelski, T.C., Moe, S.A., Weeks, M.R., and Anderson, G.G., 1993, Ice-thrust Wadena drift in the southern
St. Croix Moraine, Stearns Co., Minnesota; Geological Society of America, North-Central Section, 27th
annual meeting: Abstracts with Programs - Geological Society of America, v. 25, p. 15-16.
Hobbs, H.C., 2005, The search for early Wisconsinan glaciation in Minnesota; Geological Society of
America, North-Central Section, 39th annual meeting: Abstracts with Programs - Geological Society of
America, v. 37, p. 89-90.
Hobbs, H.C., and Craddock, J.C.(., 1983, Structure and geomorphology of the St. Croix Moraine, Swanville
area, Minnesota; North-central Section, the Geological Society of America, 17th annual meeting: Abstracts
with Programs - Geological Society of America, v. 15, p. 251.
Johnson, M.D., and Savina, M., 1987, The late Wisconsin southern margin of the Superior Lobe was 10 to
15 kilometers south of the St. Croix Moraine; Geological Society of America, North-Central Section, 21st
annual meeting: Abstracts with Programs - Geological Society of America, v. 19, p. 206.
Knaeble, A.R., 1998, Superior-Lobe glacial thrusting of sediment and bedrock along the St. Croix Moraine,
Stearns County, Minnesota; Contributions to Quaternary studies in Minnesota: Minnesota Geological
Survey, St. Paul, MN, United States (USA), Report 49, 15-26 p.
Knaeble, A.R., 1997, Glaciotectonic thrusting along the St. Croix Moraine, Stearns County, west-central
Minnesota; 1997 abstracts with programs, The Geological Society of America, 31st annual North-Central
Section: Abstracts with Programs - Geological Society of America, v. 29, p. 27.
Knaeble, A.R., 1996, Glaciotectonic thrusting along the St. Croix Moraine, Stearns County, Minnesota; Text
supplement to the geologic atlas of Stearns County, Minnesota: County Atlas Series - Minnesota
Geological Survey, v. C-10, p. 40-47.
Knaeble, A.R., and Meyer, G.N., 2006, Glacial landforms in central Minnesota; a perspective on the genesis
and age of drumlins, moraines, and glacio-tectonic thrust ridges; Geological Society of America, North-
Central Section, 40th annual meeting: Abstracts with Programs - Geological Society of America, v. 38, p.
70.
Metz, M.A., Meyer, D.P., Rogers, M.R., Thorne, R.E., and Anderson, G.G., 1994, The influence of basement
block tectonics on ice thrust Wadena Drift in the southern St. Croix Moraine, Stearns Co., Minnesota;
Geological Society of America, North-Central Section, 27th annual meeting: Abstracts with Programs -
Geological Society of America, v. 26, p. 54-55.
Norton, A.R., and Craddock, J.C.(., 1983, Supraglacial and proglacial sedimentation associated with the
Itasca and St. Croix moraine interlobate area, north-central Minnesota; North-central Section, the
Geological Society of America, 17th annual meeting: Abstracts with Programs - Geological Society of
America, v. 15, p. 251.
Ojakangas, R.W., and Matsch, C.L., 1982, Minnesota's geology: United States (USA), Univ. Minn. Press,
Minneapolis, MN, United States (USA), .
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