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This photo shows the
general
size of the esker. It is about one km wide, seven to ten km
long
and about 30 m above the water level. The mine owner said that
drill
tests indicate that it goes much deeper. Notice the higher
elevation
ground around the esker (some kames and terraces) as well as the lake
(the
small white spot 2/3 of the way to the right and halfway up). the
piles in the center have been created by the mining company. Notice the pile on the left is much lighter in color than the one just to the right of it. The more reddish color of the right pile would indicate that much of the material came from the deposits of the St. Louis Sublobe while the lighter pile to the left came from deposits of the Wadena Lobe. |
| This is a photo
(right) where
excavation is actively occurring. Notice the different size of
material
as well as the cross bedding identified by the arrow. The beds
have
been contorted by a shifting of the sediments resulting in a wave like
pattern. Click
here for more information on cross bedding. In the photos below notice both the evidence of cross bedding as well as the scooped out areas that have been filled in again. These photos are closer views of the same area. The bottom arrow (photo below left) shows a layer of coarser gravel that indicates deposition during higher water velocity along with much finer sand that would be deposited during times of much lower water velocity. These are the kinds of deposition expected in a glacier environment with periods of melting and then times of little water flow during cold periods. These periods may even occur daily. The other arrows of the photos below show areas where deposition has occurred followed by erosion and deposition again. Dr. Kroeger called these "cut and fill" structures where the river eroded some sediments and then later filled in again. |
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The photo at the
left shows
much of this cross bedding. You are looking at what would be a
cross
section diagram of the esker with each layer being deposited as
the
water flowed from behind you toward the direction you are
looking.
These are small particles that would be able to be carried by a river
during
normal flow much like the Mississippi today. These fine sediments
could not be deposited during flood stage conditions of a river.
The photos below show more of the cross bedding The blue line added to the photo helps to identify a layer of sand that is much redder. It is quite possible that it represents a water table level where oxidation of iron that is carried in the water would have occurred giving it the red color. |
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The photos to the left and below again indicate the many examples of cross bedding including very fine sands (left and below left) and areas that contain much coarser material (below right). As you look at these photos be reminded that the larger the material, the larger the water velocity needed to transport the material before it can be deposited. |
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| In the photo at the
right it
is easy to see the different colors from cross bedding. The
darker
material is probably from the St. Louis Sublobe glacier and the lighter
material was probably brought here by the Wadena Lobe. This
forms a layer pattern similar to this one in Renville County.
A rock count that was done gave the following results: 64 carbonates (limestone or dolomite), 6 metamorphic (quartzite and shale) and 28 volcanic (mostly basalt and granite) |
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The photo at the left is of a rock called phyllite, a metamorphic rock that has submicroscopic grain size (bigger than slate) and has cleavage. It was very brittle and weathered. Phyllite is similar to shale but has a glossy sheen. The small piece (lower arrow) was easily broken from the larger piece (the location of the upper arrow). |
