ORVEC: Little Slough River EarthCache
ORVEC: Little Slough River
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Little Slough River
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NOTE! This cache is best accessed by BOAT. It can be accessed on foot if the lower pool water elevation allows crossing the upper dam spillway, usually August - October! See below.
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Falls of the Ohio History
Dating back to the Middle Devonian Period, about 387 million years ago, the fossils found here are the remains of over 600 species of marine animals.
If you could go back in time to the Middle Devonian Period, you would find yourself treading water in a warm, tropical sea. Peering under the crystal blue waters, you would see odd fish swimming around and a variety of colorful corals ringed with stinging tentacles. Some colonies would be just below the wave level. The occasional trilobite would scurry in the coralline debris between the larger colonies.
Although the creatures are different, the scene would be similar to swimming in the Bahamas or Australia's Great Barrier Reef today.
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The Ohio River
The Ohio River is young from a geologic standpoint. The river formed on a piecemeal basis beginning between 2.5 and 3 million years ago. The earliest Ice Ages occurred at this time and dammed portions of north flowing rivers. The Teays River was the largest of these rivers, and the modern Ohio River flows within segments of the ancient Teays. The ancient rivers were rearranged or consumed by glaciers and lakes.
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Little Slough Riverlet
There were three ancient riverlets carved into the Jefferson limestone of the Devonian fossil beds by the meltwaters of the receding glaciers after the most recent ice age.
This erosional effect occurred some 10,000 years ago when the ice age ended and the meltwaters created the Ohio River valley.
Little Slough is the farthest upstream riverlet and is also one of the deepest. Little Slough cuts all the way down through the five distinct layers of fossils at the falls:
- The uppermost layer - or the youngest rock - is the Paraspirifer Acuminatus Zone, which contains fossils of brachiopods (including paraspirifers, a two-shelled animal similar to a clam); bryozoans (commonly called lace coral); trilobites; and some solitary, branching, and colonial corals.
- The second layer is the Fenestrate Bryozoan-Brachiopod Zone. Named for the predominant fossils found there, this layer contains many of the same corals and brachiopods as the Paraspirifer Acuminatus Zone. Here one also can find crinoid stems in abundance. Crinoids are animals that looked like plants, sporting "roots" and "flowers." When the crinoid died, the body segments separated and fossilized, leaving small, doughnut-shaped segments. Prehistoric man used these very popular fossils, which are often called "Indian beads," to make necklaces.
- The third layer is a six-inch-thick layer called the Brevispirifer Gregarius Zone, and contains fossils of brachiopods and gastropods (sea snails). The smallest horn corals, or cup corals, begin to appear here. One of the Falls' most unusual corals, called a stromatoporoid, first appears in this layer. Scientists haven't yet reached a verdict on exactly whether the stromotoporoid is a reef-building colonial coral or a sponge, but the creature played an important role in the makeup of the fossil bed.
- The fourth zone, the Amphipora Ramosa Zone, commonly called the Cave Zone, attracts attention for reasons other than the matlike stromotoporoids or the branching corals. Pocket caves have developed here due to the powerful erosive powers of the Ohio River rushing across the rock. This zone occurs along the vertical cliffs of the river channel, where the cutting force of the river reaches its peak.
- Finally, the oldest and most remarkable layer is the largest to be exposed. It bears the name Coral Zone because of its abundance of fossil corals - so many, in fact, that visitors find it difficult to walk on this layer without stepping on fossils exposed in the bedrock.
It is here that Little Slough empties into the main channel of the Ohio River.
From 1925 to 1927, a dam for generating hydroelectric power was added, and the system of canals was expanded. The Little Slough gorge stood in the way of this modernization and the riverlet was blocked by the dam wall which exists there today.
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The area is generally available August - October due to dry weather and low water.
IF YOU HIKE - BEFORE YOU GO:
Call this number: (502) 775-5056 and listen to the one-minute recording.
The recording will give you important information on the river level above and below McAlpine dam. You will also hear how much water is running through the upper and lower spillwayss of the dam (one-mile apart).
If there is ANY water running through the upper dam spillway, THIS HIKE IS NOT POSSIBLE - YOU CANNOT CROSS. (But you can paddle)
When the upper gauge is at pool, the level will be 12.6 feet. The lower level (below the dam) MUST be 12.0 feet or LESS also.
If the lower gauge is above 20 feet, the reef will be partially submerged.
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To Log This Earthcache
Take a picture of your GPSr at the listed coordinate with the steps of the Little Slough Wall in the background (see my pic).
And to demonstrate the educational value of this earthcache experience, please answer the following questions:
1. How long ago was Little Slough riverlet carved into the fossil beds and by what?
2. Which fossil layer is the first and topmost of this site?
3. The water flow here is regulated, by what?
4. How many steps are there in the Little Slough crossing at these coords?
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Please email your answers first, then LOG THE FIND. Do not wait on a reply from me. FINDs which do not meet logging requirements will be deleted.
Additional Hints
(Decrypt)
Gur nafjref gb #1 naq #2 ner va gur grkg, #3, #4 naq gur cvp ner ng gur fvgr.
Treasures
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