ROADSIDE GEOLOGY - SIMMS MOUNTAIN FAULT Multi-Cache
Know Future: Decided to reduce my inventory before placing any new caches. Had a long run, but time to move on. Thanks to all who have taken the time to hunt this one.
Know Future
ROADSIDE GEOLOGY - SIMMS MOUNTAIN FAULT
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A short geologic excursion near Farmington, Missouri
The Simms Mountain Fault is part of the New Madrid fault system, one of the largest and most active faults in the United States. We can’t see the fault itself – it is not visible in the field. We can, however, see ample, if subtle, evidence of its trace through St. Francois and Madison counties.
On this little excursion you'll see how geologists have deduced that there is at least 500 feet of vertical displacement on the Simms Mountain Fault as it passes through the St. Francis River valley. North of the fault (at Clue #1 and at the cache itself) the Davis and Derby-Doerun formations are visible. These are late Cambrian limestone beds that were deposited in a warm shallow ocean some 400 million years ago. South of the fault (at Clues #2 and #3) are exposures of Precambrian granites that are about 1,500 million (or 1.5 billion) years old.
So, what happened here? Sometime in the distant past, probably 200-300 million years ago, there was an upheaval on the Simms Mountain Fault. This upheaval pushed the deeply buried Precambrian rocks upwards 500 ft or more, to the same elevation as the Davis and Derby-Doerun limestones. What we see today is the result, after 300 million years of erosion.
This is a multi-part cache with three clues that will show you some geologic features of the Simms Mountain Fault, then lead you to the cache. The coordinates listed above will take you to...
Stop #1: Here you’ll find an exposure of tan, thin bedded, dolomitic limestone in the Davis Formation. There is a weathered green shale seam near the ground. This type of shale is diagnostic, so we know for sure that it is the Davis. Note that these rocks tends to crack and split when exposed to the weather. You are looking for an olive match case about three inches long. I've also attached a metal tag to the rocks. Both have the coordinates that will lead you to...
Stop #2: This road cut exposes a coarse red Precambrian granite. These are some of the oldest exposed rocks in the Midwestern USA. Here you can see the blast holes that were drilled to break this rock. The coordinates here are open for all to see. They will lead you to...
Stop #3: The most prominent outcrop of Precambrian granite in St. Francois County. It towers above the surrounding terrain. Look for a tag with coordinates that will lead you to...
The Cache: Here you'll be climbing a road cut of tan, thick-bedded Derby-Doerun dolostone. This is probably a small erosional remnant, as most of the surrounding outcrops are of the older Davis. The cache is a steel ammo box located within the right of way, so no need to cross the fence, which is private property. You may feel stumped, but don't give up, you'll find it.
Here are the original contents of the cache:
· Log book, pen & pencil
· 12 ft pocket tape measure
· A Bookcrossing.com audio book
· Mini FM stereo radio (batteries included)
· Yo-yo
· Jeweler’s screwdriver set
· Deck of playing cards
· Stock Market Investing Made EZ software (Ha!)
I hope you enjoy learning a bit about the earth beneath our feet. If not, I hope you find something in the cache that you like. Either way, have a great day and take care.
Additional Hints
(Decrypt)
Fgbc #1: Qba'g lbh whfg ybir trbpnpuvat?
Fgbc #2: Thgragnt (nabgure tbbq gnt).
Fgbc #3: Lbh zvtug or fvggvat ba vg.
Fgbc #4: V'ir fnvq gbb zhpu nyernql.