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Attached a Adobe PDF
format file of a field trip
that we ran last spring for the Institute on Lake Superior Geology meeting
that was held in Duluth. It has two stops that visit greenstone (stops
5-1 and 5-15). This may be helpful for you to find the places mentioned
below, and you may be interested in some of the other stops as well. I
would particularly recommend stops 5-8 and 5-9, which visit sedimentary rocks
that are the same age as the greenstone in the area.
There are some good road cuts
along highway 169 near Ely where you can see greenstone. One is 0.3
miles east of county road 88 (Spaulding Bay Road) NW 1/4 of SW1/4, sec. 25,
T.63N., R.12W. Here you can see pillow structures in the basalt (which
is slightly metamorphosed to produce the green color, hence greenstone).
This is a road cut with a nice clean flat surface on top which shows the
pillows very well. This is stop 5-15.
Another place is the big road
cut just out of Ely to the west on 169. This has pillow structures in it
as well, but they are harder to see because of the nature of the outcrop.
Another one that is very good
is in Gilbert, behind the junior(?) high school. There is a
big open grass soccer/football field behind the school, and at the north edge
of that field is a rather flat outcrop that is nice and clean, glacially
polished, that has very nice pillow structures in it. It also has
fractures filled with red jasper that were deposited during deposition of the
overlying Biwabik Iron Formation. The latter is a much younger bedrock
unit that was deposited on top of the older greenstone. This is stop
5-1.
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