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.