During this time period, in the Middle Devonian, a
mountain building phase was beginning. This is called the Acadian Oregony,
and occured when a landmass called Avalon collided
into, what is today, eastern North America. This collision was the first step in the
assembly of the supercontinent Laurussia. The collision of Avalon began to create a large
mountain range called
the Acadian Mountains along eastern North America.
Rivers running down the Acadian mountains
picked up sediments and
carried them into the Castskill basin, a basin just west of the Acadian mountains and running
parallel to it. This basin was flooded by the Kaskaskia Sea. The Kaskaskia epicontinental sea,
was just west of the Acadian mountains. It
covered New york west of the Hudson river, as well
as many other states down to, what is today, the gulf of mexico
The sediments from the Acadian mountains eventually made their way into
the Kaskaskia Sea. This occured throughout the Middle and
Late Devonian. The sediments flowing into the sea created sedimentary deposits
that formed the sedimentary
rock layers seen today in New York, and specifically those found
at 18-Mile Creek. The most fossiliferous shale and mudstone at 18-Mile Creek
tends to be the Wanakah shale of the Ludlowville formation and
the Windom Shale of the Moscow formation.
During the Middle to Late Devonian period, the global climate was much warmer
than it is today. Also, New York was almost on top of the equator.
As a result, the warm shallow Catskill basin, spoken of earlier, was the home
of a wide variety of creatures, such as coral reefs, and many other invertebrates,
such as brachiopods, pelecypods, crinoids, cephalopods, red algae,
and
gastropods. The corals and algaes contributed to the reef building
of the time period. Trilobites were common in the Devonian as well, but by
this point they were on the decline. By the end of the Devonian
period, most were extinct.
In addition, the Devonian period is known by some as the "Age of Fishes."
Armored fish, placoderms, and primitive sharks lived in the Devonian
period. In
fact, most modern fish can trace their ancestry back to that time
period. By the end of the period, fish had evolved jaws and became
the major predators of their time. The problem with these fish,
however, is the fact they were mainly cartilagenous, meaning to us
they do not fossilize much. However, the dermal armor, scales, and
teeth did, and these parts become the major links to fish of that
time period.
Note that the area of 18-Mile Creek is so large it is divided
into eight distinct sections, with each housing differences in rock
formations and, then, of course, fossil specimens. Found at the mouth
of Eighteen Mile Creek is the Lake Eerie Cliffs, which contains some of
the same exposures as Eighteen Mile Creek. For clarification, it is this
area and several
of the other sections which contain fossils of trilobites, gastropods,
corals, crinoids, brachiopods, pelecypods, and cephalopods. This is where
we have mainly collected.
For a much more detailed explanation of this area, check out this site:
New York Paleontology
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