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Gianna Alvino - The Keyser Limestone
Nick Condrey - The Sideling Hill Outcrop
Jason Grubb - The Oriskany Sandstone
Michael Hutton - Strike and Dip
Marietta Verdoni - The Sideling Hill Interpretive Center

The Keyser Limestone

Gianna Alvino
Fall 1999
The Keyser Limestone formation is found in the Appalachian Mountains and although the exact date of formation is still questionable, it is believed to have formed during the Silurian period (405-425 million years ago). The formation consists of shaly fine-grained limestone, which is about 270 to 290 feet thick and contains many animals. Essentially, the entire formation is biogenic hence everything is technically a fossil that is found there. The formation lies next to the Sandy Mile Beach. The sand is younger than the limestone, but is one the side, only due to the fact that when the Appalachian Mountains were formed, folding occurred, displacing the sandstone.

The fossils that were found there were ostracodes, brachiopods, crinoids, and bi-valve crustaceans. While looking through the limestone formation, one was able to find many examples of each of the different types of fossils, and later on able to identify many of them.

The ostracodes were the most common. They are bi-valve filter feeding crustaceans which were basically similar to tiny shrimp. They lived in the water and breathe through gills; they have a hard outer shell, and jointed appendages. The ostracode tended to be more abundant due to its smallness: the average one was about 3 to 4 millimeters in length.

The next group of fossils found was the brachiopods. These were basically two shelled animals, which contained upper and lower valves. Although brachiopods and bivalve mollusks, like clams both have two shells or "valves", their geometry is fundamentally different. When clam shells close, they meet at the animals bilateral symmetry. The valves of brachiopods, in contrast, come together in a plane perpendicular to that of bilateral symmetry. These were filter feeders just as the ostracodes, although they were not as common. The shells on them were made of calcium carbonate, which is the main component of limestone; therefore, they made up part of the formation itself. With the brachiopods, more than one species was identified, which were: Chonetes jerseyenis, and Meristina praenuntia. These two species could be distinguished with a hand lens.

The next fossils that were obtained were the crinoids, or more commonly known as sea lilies. The name is misleading though in that these were not plants, but animals that belong to the Echinodermata, and were relatives of the starfish. They were immobile creatures, which had stalks that rooted them to the ground. These stalks were made up of stacks of round disks, which are the remnant fossil that will be found in the formation. These disks, named columnals each had a hole down the center where the tissue was contained. The hole would either be circular, or a have a pentagon shape to it. The reason that it would have a pentagonal shape would be due to its five-fold symmetry. On top of the stalk was a mouth with tentacles with which it would be able to catch its food with and eat.

The last fossil type that was found would be the bivalve mollusks. The size of these can range anywhere from the size of a pin head to giant which is in excess of two meters. During the Silurian time, though, the size was typically smaller, ranging from about 2 to 10 centimeters. Normally. As inferred from the name, the bi-valves consisted of two halves, which were similar to one another. The genus that is found most commonly here is Mytilarca. There are many different ones, which may be found throughout the formation, due to how common they were at the time of preservation of the fossils. u.{މE d .-de#dsV:/* ddD.N d2nBcY&&"KWWJcy?rUX @-5YbcmrwxUV)*"#$ M R W X EMU ! !!!! !!!!8  UU fU PX U  U   #/-/7?HH(FG(HH(d'`=/R@H-:LaserWriter 8 New YorkTTTE( index.html Linda Ernst Linda Ernst