340-335 Million Years Ago
This sediment was isolated from the erosion happening on the mainland
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While the sediments in the Catskill Delta were hardening, other sediments were collecting offshore of Euramerica. These sediments were rich in calcium from the shells of prehistoric aquatic life.1 Because this sediment was isolated from the erosion happening on the mainland, it contains little siliciclastic sediment. Siliciclastic sediment is sediment that contains Silica, the stuff that makes the shiny flakes of mica you see on forest floors in New England. Because it lacks this easily crystallized silica, Bedford Indiana Limestone, properly called Salem Limestone, is quite uniform in color and texture. The uniform texture is a result of a sorting of the grains in the stone by ocean currents. In fact, these grains are not just fragments of sediment but some are microfossils, small or fragmented fossilized organisms. These fossils are mostly brachiopods and fenestrate bryozoans.2 The Salem limestone generally contains fossils between 0.5 and 2 millimeters in diameter. When the grains were being sorted by currents it is commonly thought that larger fossils were washed elsewhere leaving only the smaller sediments.
https://upload.wikimedia.org/wikipedia/commons/4/46/Limestone_block_at_the_Indiana_Memorial_Union.jpg
These calcium rich sediments underwent the same process as those in the Catskill Delta in order to form stone. As they collected on the sea floor, layer upon layer of sediment created pressure, squeezing the grains closer together. The pressure along with geothermic heat also caused minerals to precipitate out of the water still stuck in the small pores between the grains. These minerals hardened over millions of years, bonding the grains together to form limestone.3
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Sources for this page:
1. Powell, W. G. (2004). Indiana limestone. Retrieved May 16, 2016, from
http://academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCbuilding/
2. Goldstein, A. (1999). Microfossils of the middle Mississippian Salem limestone:
Midwest U.S.A. Retrieved May 16, 2016, from Falls of the Ohio State Park
website: http://www.fallsoftheohio.org/SalemMicrofossils.html
3. Geology for Dummies
1. Powell, W. G. (2004). Indiana limestone. Retrieved May 16, 2016, from
http://academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCbuilding/
2. Goldstein, A. (1999). Microfossils of the middle Mississippian Salem limestone:
Midwest U.S.A. Retrieved May 16, 2016, from Falls of the Ohio State Park
website: http://www.fallsoftheohio.org/SalemMicrofossils.html
3. Geology for Dummies