HISTORICAL GEOLOGY
LECTURE 1. STRATIGRAPHY
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Stratigraphy:
Many past geologic events have resulted in strata or layers of sediment
which have formed a stacked vertical sequence of sedimentary rocks. A good
example is sediment in the form of mud and sand from a river accumulating
on a sea-floor. The sediment forms a layer which eventually becomes
or lithified into a sedimentary rock.
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Historical Geology
The importance of stratigraphic sequences to historical geology is that they
provide a rock record of past events e.g. a pebbly beach may be recorded as a
CONGLOMERATE, a sandy river may be recorded as a layer of
SANDSTONE; a clayey tidal flat as a layer of SHALE.
Pebbly beach
conglomerate
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Sandy beach
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sandstone
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Muddy marsh
shale
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Stratigraphy is the study of these layered rocks, especially
their sequence, correlation from place to place, relative ages and
interpretation. Several important stratigraphic principles
emerged from the study of stratigraphy centuries ago by the
early founders of the science of geology:
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Harry Williams, Historical Geology
1. Principle of Superposition: In any sequence of undisturbed strata, the
oldest layer is at the bottom and higher layers are successively younger.
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Harry Williams, Historical Geology
2. Principle of Original Horizontality: Most sedimentary rocks formed
originally in close-to-horizontal layers (although many have since been moved
from their original position).
Undeformed strata
Deformed strata (tilted)
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"The present is the key to the past" i.e. geologic processes operating today also
operated in the past. e.g. river deposits forming today have a similar
composition and character as their ancient counterparts; glacial erosional and
depositional features are basically the same today as in the past...etc.
Modern
sand dune
Harry Williams, Historical Geology
Ancient
sand dune
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RESEARCH EARTH
SCIENCE: EXAMPLE
INFORMATION
BEREA SANDSTONE
History and description of the age of the of the
sandstone you select
Berea Sandstone
AGE: Late Devonian – 416.0 to 359.2million years ago (mya)
The Berea Sandstone formed from ancient streams in Canada that flowed to
and filled ancient and stagnant (non-flowing) seas that sat over the states of
West Virginia, Michigan, Ohio and Pennsylvania.
Through this process, the ancient streams traveling south from the Canadian
Shield dropped off sediments into the shallow seas located in what are now
parts of the above states. When the seas eventually regressed (went away)
due to climate and the building of the Acadia mountains to the east due to
plate tectonics, the shallow seas disappeared and what were left were the
rock layers such as the Berea Sandstone that had been deposited years earlier.
Description of the formation (location, size, type
of sandstone)
• The Berea Sandstone is located throughout 4 states KY,MI,OH,WV and covers near 50,000 square feet.
• Berea sandstone is a rock layer is a member of a number ofrock formations in the northeastern United
States. It exists in the following formations
• Berea Sandstone of Pocono Group (WV)
Berea Sandstone of Waverly Group (OH)
Berea Formation (MI)
Berea Member of Pocono Sandstone (KY)
Berea Member of Chattanooga Shale (KY)
• The Berea Sandstone is a fine-grained quartz based sandstone.
• It is primarily made of the following minerals:
• 88.9% Quartz
• 3.9% Cay
• 3.4% Feldspar
What have humans used the sandstone for as
a resource?
• Has been used for decades as an oil and gas producing formation
in the states of Kentucky, Ohio, and Michigan
• Berea Sandstone has been used as a building material; it has
angular, opposed to rounded grains which makes it a strong
abrasive. It has been used for buildings, sidewalks, foundations
and bridges.
• It has been famously used as a gridstone due to its consistent
sandstone texture.
Porosity and permeability of the sandstone
What is Porosity and Permeability?
• Porosity: consists of the tiny spaces in the rock that hold the oil
or gas.
• Permeability: is a characteristic that allows the oil and gas to
flow through the rock.
• Porosity: 2 studies conducted have shown that the Berea
Sandstone has an average porosity of 22-23% (Zhan, 2010)
• Permeability: Semi-permeable. At a 22-23% porosity, Berea is
somewhat permeable and is capable on holding gas and oil.
Types of fossils present
• The Berea Sandstone does not contain many fossils due to the
sandstone depositing during the late Devonian.
• The Berea was deposited in an ancient, shallow ocean that was
murky and did not have a flow (stagnant). Due to the environment
of these anciet oceans, it was not a substantial environment for
organism to thrive in.
References
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Berea Historical Society. Berea Historical Society, n.d. Web. 13 Sept. 2015.
<http://www.bereahistoricalsociety.org/site/Sandstone.aspx>.
Ohio History Central. Ohio History Connection, n.d. Web. 13 Sept. 2015.
<http://www.ohiohistorycentral.org/w/Bedrock_Geology_of_Ohio>.
Zhan, Xin, Lawrence M. Schwartz, M. Nafi Toksoz, Wave C. Smith, and F. Dale Morgan.
“Pore-Scale Modeling of Electrical and Fluid Transport in Berea Sandstone.” GEOPHYSICS 75,
no.5 (September 2010): F135–F142. © 2010 Society of Exploration Geophysicists
National Geologic Map Database. U.S. Department of the Interior | Geological Survey, 15
July 2015. Web. 13 Sept. 2015. <http://ngmdb.usgs.gov/Geolex/Units/Berea_413.html>.
Craig, Lawrence C. "Paleotectonic Investigations of the Mississippian System in the United
States." Geological Survey Professional Paper(n.d.): 45+. Web. 13 Sept. 2015.