VFEC3: The Port Kennedy Quarry EarthCache
VFEC3: The Port Kennedy Quarry
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Difficulty:
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Terrain:
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Size: 
(other)
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To log this cache, you will need a binoculars, paper, pen and a camera. The walk to ground zero consists of short walk from the parking lot to the cache coordinates. This is an active road you will be walking on so be very careful!
The above coordinates will take you to a great place to view the Quarry. Please notice the “Danger” signs posted and DO NOT cross into the fenced area. A total of 112 acres within the park where asbestos and other hazardous substances have been discovered are currently closed to public access. This area is referred to as the “the Valley Forge Asbestos Release Site.” While the primary contaminant at the Site is asbestos, contaminants other than asbestos also have been detected at elevated concentrations, including arsenic, lead, mercury and others that pose a risk to human health.
The first thing you will notice is that there are two rather distinct types of rocks visible. The base (lower) is a light colored rock called Ledger dolostone. It is believed to represent a sediment which was deposited as a chemical precipitate at the bottom of an ancient sea. It is thought to have been formed during the Cambrian period, more than 500 million years ago.
In places this is stained red from the rock above it. The red rocks above are composed of sand-sized fragments which have been cemented together (sandstones) as well very fine clay particles (shales). These are a fragmental sedimentary rocks that represent a different type of sedimentary deposit than the dolostone. These red rocks lie at the southeastern edge of a broad belt of similar rocks which extend all the way from the Hudson River in NJ, all the way south into Maryland. Plant fossils and amphibian footprints have been found in these as well as other features that indicate that the red sediment was deposited from land and not sea. The red rocks belong to the Stockton Formations and were formed in the Triassic period, about 190 million years ago.
So the dolostone was formed >500 million years ago and the red stones are about 190 million years old. As there is nothing deposited between this time, either no rocks were deposited or those that were deposited eroded away a long time ago. A surface such as this which represents either erosion or nondeposition is known as an unconformity.
Both the rocks represented here are sedimentary rocks as evidence by the layers or beds. When these beds form, they form horizontal or nearly horizontal. If you look at the dolostone, you will notice that the bedding is nearly vertical. In contrast, the red sediments appear nearly horizontal (although is is actually sloping into the cliff away from the viewer.
When the dolostone layers were first deposited, they were undoubtedly laying in a nearly horizontal position. At a later date, the bedding assumed the nearly vertical position we see now. This probably happened during the Appalachian revolution when a great deal of mountain building took place in eastern North America.
The bedding in the rock below the unconformity lies at an angle to bedding in the rock above the unconformity, this feature is known as an angular unconformity. This angular unconformity is one of the best exposed unconformities in the eastern portion of the United States.
To log this earthcache:
Using your binoculars, view the Angular Unconformity and sketch what you see. Make sure to label both stone types. Please post this picture to your log.
Sources:
Guidebook To The Geology Of The Philadelphia Area.
http://www.dcnr.state.pa.us/
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Valley Forge Caching Info:
It is required that cachers stay on marked trails at all times.
Only Earthcaches and virtual stages of caches may be placed on Valley Forge land.
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Treasures
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