Bunyan’s Bowling Ball – The Grandview
Boulder
This boulder was plucked from the bedrock
of the Penokee Range by the southward moving glacier of the last
Ice Age. It was derived from the upturned edge of the Bad River
Dolomite Formation, and was transported about three miles before
being dropped.
This formation of cherty carbonate was
once a limey mud in the bottom of an ancient Pre-Cambrian sea,
during Huronian time, more than a billion years ago. Upon with
drawel of the sea, the mud solidified into dolomite rock. This rock
was then metamorphosed into marble during a period of extensive
mountain building that involved the entire Lake Superior region.
These mountains in their prime must have rivaled today’s Rockies in
scenic grandeur. The Penokee Range today is a worn destroyed by
weathering and erosion. The Bad River dolomite incorporated within
this root segment is the only extensively exposed marble formation
outcropping within the state of Wisconsin.
One of the more interesting aspects of
this boulder is the fact that it preserves evidence of its original
sedimentary character in the form of fossils. There are very
distinct colonies of algae that grew on the bottom of the shallow
Pre-Cambrian sea in this boulder. The surface of the colonies had
convex upper surface facing the sunlight. This fact allows
determination of the original “up” direction on the sea floor. It
is easy to see that this boulder is tilted, and therefore the
original direction of “up” on the sea floor, is now inclined toward
the west.
PLEASE DO NOT DEFACE THIS BOULDER OR
LITTER THE ADJACENT GROUNDS. SPECIMEN COLLECTING IS ABSOLUTELY
PROHIBITED.
TO LOG THIS CACHE:
1) What are the “wavy bumps” seen on the surface of the
boulder?
2) Measure and average the size of the “wavy bumps”.
To log this cache -mail me the
answers
HERE.