Hist. geology field report
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Transcript of Hist. geology field report
Jesse Jones
11/17/15
Field Report
Site 1 Route 15:
First step out of the van was a very vertical rock cut facing the west. We parked right beside a
unit of sedimentary rock that looked very brittle to the eye. There were many layers upon layers
when examining the structure of the formation. To the south of where we park were a red
sedimentary rock called “rock beds”. There were two different formation at this site which made
it an intriguing area of study. Over the course of the 20-30 minutes many people were finding all
sorts of fossil fragments some that were still in tacked and others that broke away from the rock
unit quite nicely. The two formation of study at this first stop were the Lock Haven formation
which contained ruminates of shallow marine fossils that were about 30-90 meter thick
according to Bradford writer of Roadside Geology of Pennsylvanian. Mainly a Devonian Lock
Haven formation with a contact of overlying Catskill formation (Bradford 127). Taking note to
the south, mostly Catskill formation, dominantly reddish, sometimes red brick or maroon, to
greenish gray, cross bedded sandstones and the thin shale’s (Bradford 127) these formations,
both the Lock Haven and Catskill red beds formed during the Devonian period ranging from 400
million years old to 370 million years old. From North to South, the Lock Haven formation was
to the north ranging in height of 20-50 meters at the rock cut location we were observing.
Moving to the south this shale and mud/silt stone structure continued to be more of a sandstone
based rock structure throughout having no real vast fossil formation and was quite abrupt when
walking up to it from the Lock Haven Formation. With the Arcadian Mountains to the east the
deposition of this location was quite low. From what we saw starting from the south of the rock
cut was higher ground predominantly dry environments. Heading north the environment was
seen as a lower or shallow marine environment with the assortment of marine type fossils and
vegetation throughout the rock cut.
Figure 1: Coalified Wood or
Plant Frag.
Figure 2: A small Cemerotochia
Figure 3: Rhipidomella
Site 2 Mutton Creek Road Cut; Route 328:
The second rock exposure wasn’t as good as the first due to the time of year. Being that this rock
cut was located in a forest there was lots of leaves on the ground covering up majority of the
rock exposure. Taking note this site was across from a creek running east to west. From what the
Roadside Geology of Pennsylvania there used to be an old railroad put in place along this route
and over time Mutton Creek’s original direction of flow was along this rock cut but now has
moved either naturally to the south 50 yards or was diverted by man. With that said, this
formation is a part of the Lock Haven formation. Being north, this part of the Lock Haven
formation doesn’t have the depth compared to the road cut a couple miles south of this cut. The
sub unit is called the Westfalls Group while the main formation is the Lock Haven. Being that
the first site was a shallow portion of the lock haven formation as the formation moved to the
north the waters were interpreted has deeper waters do to the different types of fossil groupings
like Pelecypods, Brachiopods, and Horn Coral. Another give away for this being a location of
probable deep marine environments is the type of sediments the rocks are made of as well.
Figure 4: Coalified plant material
Figure 5: Coalified plant material
(Lower Center), Portion of Horizontal burrow (Upper center)
Figure 6: Small
Aviculopectem (Lower Right), Two Rhipidomella (Lower Left and Center), Small
Whidbormella (Upper Right)
Bibliography
Berg, T. (1981). Guidebook for the 46th Annual Field Conference of Pennsylvania Geologists:
Geology of Tioga and Bedford Counties, Pennsylvania. Harrisburg, PA: Distributed by Field
Conference of Pennsylvania Geologists c/o Dept. of Environmental Resources, Bureau of
Topographic and Geologic Survey.
VanDiver, B. (1990). Roadside geology of Pennsylvania. Missoula, Mont.: Mountain Press Pub.