Winona's Subterranean Slug Fest EarthCache
Winona's Subterranean Slug Fest
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The coords take you to the parking area near the scenic overlooks at Garvin Heights Park. Follow the path to the overlooks and kiosks. Please observe the retaining wall stones. These are excellent examples of 430 million year old marine worm trails.
Approximately 600-500 million years ago, a shallow inland sea covered this region. There was no land vegetation at this time. Erosion of the land masses and sedimentation were gradual processes during this quiet time of warming seas.
The seas were rich with algal colonies and microscopic life forms. Around 430 million years ago, as the seas warmed and oxygen levels increased, new marine life forms evolved with the ability to secrete hard body parts in the form of internal skeletons and shells, endo- and exoskeletons, to protect their soft bodies in response to the the changing environment. These shells were protective mechanisms developed in response to an increased exposure to:
1.A higher density of UV radiation;
2.Greater physical stresses from waves and currents;
3.Higher predator stress.
During the same time period, the sedimentation of magnesium rich limestone and sand granules from the erosion created the upper Oneota Dolomite layer of stone in the bluffs you see today. This layer is approximately 165 feet thick.
Marine invertebrates, including worms, found this subterranean substrate to be ideal for burrowing, thus creating a porous appearance in this stone. Slow sedimentation in the calm waters filled and fossilized these burrows, creating the relief pattern you see today in the quarried rocks of the retaining walls. Crystalline dolomite inclusions and calcite deposits are also present in some of the rocks showing fossilized coral.
This Oneota Dolomite stone is indigenous to this area and is loosely named “Winona Travertine.” It is highly sought as a weather resistant decorative architectural component for commercial buildings and fireplace surrounds. It is only quarried at Biesanz Quarry, however, examples may be viewed on Highway 14 at the Stockton Hill roadside cuts.
To receive credit for this earthcache, you will need to complete the following tasks:
1.Please measure the width and depth of 10 of the fossilized trails in the retaining wall rocks IN MILLIMETRES at overlook one or two, average those numbers and e-mail them to me when you log this earthcache.
2.Please post a photo of an example of one of the worm trails or fossils seen here today.
3.Please post a photo of yourself and your Gps with a background view of this lovely Bluff Country.
Enjoy!
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