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The Vanport Limestone Outcrop at Jack Critchfield Park
MILLER, Tyler. PEET, Ellis. SCHIAPPA, Tamra. Ph. D. Geography, Geology, and the Environment Department, Slippery Rock University, 1 Morrow Way, Slippery Rock, PA 16057.
Introduction
Pictures of the Outcrop, the fossils, a google earth map of the location or a geologic map of the VP
After examinationon of thin sections, hand
samples, and the outcrop, we have determined it
is nearly homogenous throughout with only
slight variations in allochem to mud ratio. Based
on the near 50/50 mud/allochem ratio we used
Dunhams classification to name the rock a
packstone. Many fossils exist throughout the
outcrop including, ostracods, brachiopods,
echinoderms, gastropodods, and foraminifera.
The finding of a foraminifera is significant
because it allows us to date the formation of the
rock to 323-252 million years ago.
Only a meter beyond the left field foul pole
at Jack Critchfield Park lies a late Paleozoic
limestone outcrop. Limestones consist of CaCO3,
which are formed by the sedimentation and
compaction of marine organisms that died in a
tropical, shallow ocean. Geologists use the
combination of allochems and the mud they are
entombed in to categorize limestones. This is
important because of the economic uses of
particular limestones as well as dating the rock to
recreate the past environment it formed in.
Photo of the Vanport Limestone outcrop located at Jack
Critchfield Park
Methodology
We started by measuring and analyzing the
outcrop, which has a height of two meters, so we
took hand samples from every quarter meter
using a hammer to break off a piece of rock. We
took these hand samples to the rock lab in ATS
where we cut the rock into a thin rectangle
(billet) and epoxied it to a slide. After a few
hours of drying, we use the PetroThin machine
then grind the billet to 30μm. Next, we analyzed
the percent of mud and each allochem and
proceeded to name the rock based on Dunham’s
carbonate classification scheme.
Results
Conclusion
Microscopic Organisms Responsible for the Formation of The Vanport Limestone
Phylum: Foraminifera
Order: Fusilinida
The fossils present in the outcrop tell us that the
rock was formed in a tropical shallow ocean during
the carboniferous and Permian periods. This
outcrop is part of the Vanport limestone group
which extends through much of western
Pennsylvania. The rock is a valuable resource, as it
is used for cosmetics, fertilizer, interior décor, and
most importantly as an aggregate in cement and
other building materials.
Phylum: Brachiopoda
NSH Quadrants
W
in
d
A large crinoid on the surface of the outcrop. A pen lies
underneath for scale.
References
To make a thin section (right), a billet is suctioned to a lever on
the PetroThin (left) and set to 30μm. The lever slowly swings
into the machine against a grinder to thin the billet.
Class: gastropoda
Paleozoic Algae
Order: Fusilinda
Harper, A. John. Suter, B. Simeon. Pennsylvania Geology, DCNR.
Mackenzie, W.S., Adams, A.E. A Colour Atlas of Rocks and Minerals in
Thin Section. Schiappa, Tamra.
MILLER, Tyler. PEET, Ellis. SCHIAPPA, Tamra. Ph. D. Geography, Geology, and the Environment Department, Slippery Rock University, 1 Morrow Way, Slippery Rock, PA 16057.
Introduction
Pictures of the Outcrop, the fossils, a google earth map of the location or a geologic map of the VP
After examinationon of thin sections, hand
samples, and the outcrop, we have determined it
is nearly homogenous throughout with only
slight variations in allochem to mud ratio. Based
on the near 50/50 mud/allochem ratio we used
Dunhams classification to name the rock a
packstone. Many fossils exist throughout the
outcrop including, ostracods, brachiopods,
echinoderms, gastropodods, and foraminifera.
The finding of a foraminifera is significant
because it allows us to date the formation of the
rock to 323-252 million years ago.
Only a meter beyond the left field foul pole
at Jack Critchfield Park lies a late Paleozoic
limestone outcrop. Limestones consist of CaCO3,
which are formed by the sedimentation and
compaction of marine organisms that died in a
tropical, shallow ocean. Geologists use the
combination of allochems and the mud they are
entombed in to categorize limestones. This is
important because of the economic uses of
particular limestones as well as dating the rock to
recreate the past environment it formed in.
Photo of the Vanport Limestone outcrop located at Jack
Critchfield Park
Methodology
We started by measuring and analyzing the
outcrop, which has a height of two meters, so we
took hand samples from every quarter meter
using a hammer to break off a piece of rock. We
took these hand samples to the rock lab in ATS
where we cut the rock into a thin rectangle
(billet) and epoxied it to a slide. After a few
hours of drying, we use the PetroThin machine
then grind the billet to 30μm. Next, we analyzed
the percent of mud and each allochem and
proceeded to name the rock based on Dunham’s
carbonate classification scheme.
Results
Conclusion
Microscopic Organisms Responsible for the Formation of The Vanport Limestone
Phylum: Foraminifera
Order: Fusilinida
The fossils present in the outcrop tell us that the
rock was formed in a tropical shallow ocean during
the carboniferous and Permian periods. This
outcrop is part of the Vanport limestone group
which extends through much of western
Pennsylvania. The rock is a valuable resource, as it
is used for cosmetics, fertilizer, interior décor, and
most importantly as an aggregate in cement and
other building materials.
Phylum: Brachiopoda
NSH Quadrants
W
in
d
A large crinoid on the surface of the outcrop. A pen lies
underneath for scale.
References
To make a thin section (right), a billet is suctioned to a lever on
the PetroThin (left) and set to 30μm. The lever slowly swings
into the machine against a grinder to thin the billet.
Class: gastropoda
Paleozoic Algae
Order: Fusilinda
Harper, A. John. Suter, B. Simeon. Pennsylvania Geology, DCNR.
Mackenzie, W.S., Adams, A.E. A Colour Atlas of Rocks and Minerals in
Thin Section. Schiappa, Tamra.