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Siderite Nodules "Earth's hidden fossils" EarthCache

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behind the camera: Not fun anymore

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Hidden : 5/7/2009
Difficulty:
2 out of 5
Terrain:
2.5 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:


Photobucket

Anglin Falls is an place that I visit often with my boyfriend. Here you will hear songbirds, the scatter of leaves as squirrels run about the forest floor, and the occasional “swoosh” of an owl flying across the gorge. I hope those who come to visit the falls find it an enjoyable experience.

The forest was dedicated in 1996, as the John B. Stephenson Memorial Forest State Nature Preserve. Located in a 124-acre wooded gorge with a rich spring floral display, the preserve honors John B. Stephenson, the former president of Berea College who enjoyed the area's beauty and solitude and worked hard to preserve the forest surrounding Anglin Falls. Long open to the public, the preserve will remain a significant source for education, interpretation and inspiration for the people of Kentucky and the students and faculty of Berea College. Photobucket

My boyfriend brought me to this spot to show me the odd shaped rocks he found in the creek. The rocks first appeared as erractics, but where covered with an brownish rust like film of mud. Upon closer inspection, we discovered fossils where inside the rocks. The rocks are mixed in with the grey shale mud that looks like clay. The rocks contained crinoids and mussel shells.

A little research revealed that the rocks are called Siderite Nodules. Siderite is a common mineral associated with geodes, nodules, and ironstone banding. Siderite is very common in the coal fields, where it occurs as a reddish-brown mineral in shale layers, nodules, concretions, and fossil burrows. Commonly, a siderite nodule will have a nucleus of another mineral such as pyrite, sphalerite, or chert. Siderite also occurs in geodes with dolomite and calcite. Siderite becomes magnetic on heating, and alters readily to limonite and goethite. Photobucket

Siderite and associated iron minerals form curved bands common in sandstones in Anglin Falls. These bands are called Liesegang bands.

In the Anglin Falls Creek, siderite nodules that look similar to siderite nodules found in the coal fields of Kentucky. Do you know what is found in siderite nodules?

Siderite nodules from Anglin Falls Creek are locally famous for the fossils they sometimes contain. Fossils of crinoids and mussel shells are most common. Sometimes fossils of soft-bodied organisms, like the millipede, and fern leaves are found, however you will mostly find brachiopod and clam fossils in the siderite nodules.

Siderite nodules like those in which Anglin Falls Creek Fossils are found form when a iron, calcite and clay were all available during a bad day in the Pennsylvanian. A bunch of plants and animals died together and were buried by a fine silt. The positive nature of the dead material attracted the negatively charged clay particles; the iron and the calcite provided the cement. Waving a UV light over Anglin Falls concretions could reveal soft structure details due to extra calcite in these areas. Photobucket

Concretions are formed by the deposition of distinct minerals, different from the surrounding rock, very firmly cemented around a nucleus. They are generally lens shaped, although some have irregular, complex forms. The most common cementing materials are calcite, siderite, and silica. Parts of plants and animals may serve as nuclei, and well-preserved fossils may be found in concretions. In Kentucky, large concretions of siderite and calcite, which used to be called ironstones, are found in shales associated with coal beds. Nodules are another type of irregularly shaped minerals that occur in sedimentary rocks. The most common minerals that occur in nodules are siderite, gypsum, calcite, quartz, and barite/celestite. Siderite nodules, concretions, and liesegang (iron-stained) banding are a very common type of mineralization found in eastern and western Kentucky sandstones.

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Directions - Rockcastle County. From Exit 76 on I-75, go east 3.5 miles on KY 21 to the center of Berea. Turn right at the light (staying on KY 21), past the Boone Tavern, and travel another 5 miles. Turn right (south) on to US 421 and travel 2.6 miles. Turn right on Burnt Ridge Road and travel .2 miles, then left on Himanns Fork Road and travel 3.4 miles.

Look for a red brick house on the right (box 530); approximately one-tenth of a mile past the house make a sharp left turn down a steep hill on to Anglin Falls Road. Travel .9 miles on Anglin Falls Road to a sign that says "Anglin Falls" next to a mailbox marked "542 R2". Turn left and travel .2 miles to the parking area/trail head.

To get a smiley for your discovery, please answer the questions and post a picture of you and your group at the EarthCache site holding a Siderite Nodule (creek in background). Please include a smiling face!

What is the average size of the nodules?

Are the nodules smooth or rough when touched?

Source of educational information for this EarthCache comes from the Kentucky Geological Survey, University of Kentucky.

Additional Hints (Decrypt)

Gnxr n qrrc oerngu naq fzryy gur nve. Jnyx fvyragyl naq yvfgra. Yrg Angher thvqr lbh guebhtu ure sberfg.

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)