Eugene's Monotis Traditional Cache
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Another geologically themed geocache in a remarkably diverse (geologically speaking) mountain range of northwestern Nevada. Although it appears remote on a map, the gravel roads to this site should be easily accessible by most passenger cars, and then there is a short climb up slope. It is just a short side trip off Interstate-80 (less than 20 minutes to get there). More complete access directions are below.
This geocache is situated on a hillside in an area where you can find fossils of an ancient clam called Monotis subcircularis that lived offshore in the sea here more than 200 million years ago. Some of the rocks covering the cache container will show you what Monotis subcircularis fossils look like, but please rehide the cache well with these rocks and move uphill to search for your own examples of the fossil; they are very easy to find on the ridge just above and west of the cache all the way to the top of the hill to the south, as well as elsewhere in the Eugene Mountain Range (see map).
Monotis is the genus name for a fossil bivalve (2-shell) “flat” clam of Mesozoic age – the same time span when dinosaurs lived on Earth. There is some controversy over exactly what environment the clams lived in, but it was probably in a shallow continental shelf environment or intertidal zone of the ocean, or brackish tidal lagoon much like the marine environments occupied by clams today. Each individual species of Monotis clam was widely distributed geographically, but had a short species longevity, which makes them very useful in paleontology for identifying certain geologic time periods. The fossils are found in marine mudstone, siltstone, medium-grained sandstone, and in limestone.
Here in the Eugene Mountains, the Monotis subcircularis fossil clam shells are found on bedding plane surfaces in a siltstone to fine sandstone that outcrops on the hillsides Look closely at the platy rock fragments that have eroded off the outcrops and you may find the imprints of the ancient organisms that tell us that the rocks here formed from shallow ocean sediments that covered this region in Triassic time, about 215-220 million years ago.
A detailed geologic map with text description of the geology and mineral deposits of the Eugene Mountains is published by the Nevada Bureau of Mines & Geology, and available free download on the Internet at the link below. Paper copies of the map can also be purchased at the NBMG office on the DRI campus at 2175 Raggio Parkway.
Geologic map of the Eugene Mountains, northwestern Nevada: Ronald Thole and Douglas Prihar, 1998.
The map shows the location and description of rock units and many fossil localities in the Eugene Mountains in addition to this one.
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Access: Take the Mill City Exit off Interstate 80 and go north, cross the Humboldt River, and continue until the road makes an abrupt 90-degree right turn at the gate of the GE Springer Tungsten Mine (about 7 miles from I-80). Do not enter the mine property; turn right, and drive 1.2 mile, at which point the road makes a 90 degree turn to the left (north). Go north for 1.7 mile to a fork in the road and take the left fork to the west. Note your odometer mileage here and drive about 2.7 miles (on Pole Canyon Road) and then follow your GPS directions from there.
Collecting small amounts ( up to 25 pounds) of rocks, minerals, and invertebrate fossils on public lands for personal and educational use is allowed, but commercial exploitation or sale of the fossils, rocks, or minerals collected on public lands is a violation of federal law.
Additional Hints
(Decrypt)
Ebpx-n-olr, onol.
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