ABOUT THIS EARTHCACHE
This EarthCache will bring you to an exposed view of shale and sandstone that formed during the Pennsylvanian Period between 323 to 299 million years ago. The exposed rock you are looking for is across the river from the parking area. This is across the outflow area of the dam and can be dangerous. There is a walkway with railing and picnic tables at GZ. If the outflow appears too aggressive to be near, if it is closed or if you feel you can't safely get to the posted coordinates, then you can make your observations from the parking lot.
LOGGING REQUIREMENTS
In order to log this EarthCache, send me your answers to the following questions either through email or messaging from my profile page.
1: Can you see a clear division between the Birmingham Shale layers and the Morgantown Sandstone layers?
2: Estimate the height of the Birmingham Shale layer.
3: Estimate the height of the Morgantown Sandstone layer.
4: Describe any differences between the layers as far as color, consistency, texture or anything else you notice.
5: Post a pic of you or a personal item with the outflow in the background.
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HISTORY
The Pennsylvanian Period, also known as the Upper Carboniferous, is a geologic time span within the Carboniferous Period that lasted from roughly 323.2 to 298.9 million years ago. It's characterized by the uplift of continents, a transition to a more extensive terrestrial environment, and the formation of coal swamps. The name "Pennsylvanian" comes from the state of Pennsylvania, where the rocks of this period are well exposed, particularly the coal beds.
WHAT ARE YOU LOOKING AT?
The lower level you are looking at is Birmingham Shale. These rocks indicate that the climate warmed up so that tropical coastal swamps could develop across western Pennsylvania. The very nearshore marine fossils that are sometimes found in the Birmingham Shale indicate that full-fledged marine waters lay not too far to the west. The fact that full marine conditions were not experienced in the Pittsburgh area suggests that the submergence of the continental areas during this time interval was not extensive. The upper level is the Morgantown Sandstone. This sandstone is the result of a cooling episode, where sea levels dropped and large river systems criss-crossed the region.
MORGANTOWN SANDSTONE
The Morgantown Sandstone is a sedimentary rock formation, specifically a sandstone, found in southwestern Pennsylvania and parts of West Virginia. It's part of the Pennsylvanian period and is characterized by its massive to cross-bedded structure, often varying in thickness from 10 to 65 feet. The sandstone is thought to have formed during a period of sea level drop and large river systems criss-crossing the region.
BIRMINGHAM SHALE
The Birmingham Shale is a dark, thinly laminated shale rock unit within the Casselman Formation. It's situated below the Morgantown Sandstone and above the Ames Limestone in the Pittsburgh area. The Birmingham Shale is described as unranked marine or brackish-water shale cropping out in Birmingham, Allegheny County, PA, between the Elk Lick coal and the Skelley limestone.
references
https://sites.pitt.edu/
https://pittsburghgeologicalsociety.org/
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