One of the parks main features is McCormick's Creek Canyon Falls.
Some 250 million years ago Indiana was covered by a broad,
shallow sea. Limy mud and sand were deposited layer by layer on the
sea bottom. As these soft sediments became deeply buried, they were
compressed and cemented into layers of solid limestone. Geologists
have divided these rocks into three formations, which lay on top of
one another like a stack of pancakes. All three bedrock formations
date from the Mississippian Period of geologic time, and together
they represent about a million years of geologic history.
The lowest, and therefore the oldest, of these formations is the
Salem Limestone, which can be seen in the old quarry near the mouth
of the canyon and in the lower canyon walls. The limestone is in
the thick beds, is uniformly sandy in texture, and weathers into
huge rounded blocks. Some surfaces show a pitted effect known as
honeycomb weathering. Only a few large fossils are present, but
with a magnifying glass you may be able to see that most of the
sand grains are small fossils or rounded fossil fragments. Many are
the shells of Endothyra baileyi, a single-celled animal that lived
in abundance in the ancient sea and was no bigger than a
pinhead.
The middle formation is the St. Louis Limestone. This layer is
about 60 feet thick and makes up most of the canyon walls. It is
more fine-grained and more closely cemented than the Salem
Limestone. Some of the beds are shaly and some contain nodules of
chert, a hard flinty material. Among the fossils that are abundant
in some beds are colonial corals, such as Lithostrotionella.
Observe but please don't collect specimens in the park.
The St. Louis Limestone ends at a height about equal to the top
of the falls. Upper parts of the canyon walls are made up of the
third formation, the Ste. Genevieve Limestone. Rocks of this
formation are even more fine grained, more smooth textured, and
more compact than those below. The Ste. Genevieve Limestone is the
youngest bedrock of the park.
Long after the rocks were formed, they were lifted above sea
level, and streams began their work of erosion. Valleys similar to
those of today were formed. Then, about a million years ago, a
series of glaciations began that powerfully shaped the topography
of this part of Indiana.
The glacier that covered the park area is known as the Illinoian
glacier. It left deposits of sand and clay that contain cobbles of
granite and other stones from as far north as Ontario. These
deposits show that the limit of this glacier's advance was just
southeast of the park. The ice blocked many of the pre-glacial
valleys, and drainage from these valleys, along with meltwater from
the glacier, had to flow southwestward along the glacier margin for
many miles before it could find an outlet to the Ohio River.
When the ice melted, glacial deposits still blocked some of the
pre-glacial valleys. Some of the streams that drained these valleys
did not find their former courses but eroded new ones. The area
southeast of the park formerly drained westward, but glacial
deposits diverted the drainage to the northwest across what is now
the park, and in this way the course of McCormick's Creek was
determined.
As the creek eroded downward, the rock-walled canyon was formed.
Most of this erosion probably took place about 50,000 years ago,
when ice of the last glaciation (which did not reach the park area)
was advancing from the north. At that time the climate was wetter
and colder, and erosion was more rapid than it is today. The falls,
which are evidence of the canyon-forming process, still are eroding
their way upstream, but now at a very slow rate.
In the upland area of the park are numerous bowl-shaped
depressions called sinkholes. Some are small, some are large, and
some are in groups or in rows. A few contain springs and small
streams that sink into the ground. All these features were formed
by the underground movement of water, which slowly dissolves the
limestone bedrock and forms an underground network of passageways
to carry the water. Sinkholes, which are formed as the limestone is
slowly removed from beneath the soil, carry the runoff from rain
and snow underground.
As the underground streams seek lower and lower levels, some of
the passageways are left high and dry. Wolf Cave is an example of a
large dry passageway that has been opened to view by erosion.
Erosion also leaves small remnants of the passage as natural
bridges. Litten Natural Bridges are an example. Features formed by
subterranean drainage are known as karst features and are
widespread in part of southern Indiana where limestone is
found.
Want to know even more about the geology, history, plants or
animals of McCormick's Creek State Park? Check out the Nature
Center for exhibits, brochures, interpretive services and more.
To get credit for this earth cache:
1. Take a picture of a team member with gps in hand and the
falls. It can be taken at the overlook deck or down at the creek
slab reference point.
2. Elevation readings at the end of the steps at the creek slab
reference point, the overlook deck, and parking area. A total of 3
readings.
3. Name the type of falls these are.
Post your picture with your log and email me your answer and
readings via my profile page.
Waypoints for the parking, creek slab reference, and overlook
deck are provided. Get your pictures and readings at these
waypoints.
Please follow the parks rules.
