Banded Iron Formation - I found this sample near Jasper knob, Marquette, Upper
Penninsula of Michigan. The red layers are iron rich cherts and
the grey layers are pure iron. No one theory has gained favor
with geologists as to the origins of these lower Proterozoic rocks.
Most theroies center around the hypothesis that the atmosphere
at that time was depleted in oxygen increasing the amount of iron
leached during weathering.
