A view of the conglomerate rock bluff
overlooking Wildcat Creek at Clegg Garden. Looking south, a view
upstream of the creek. The rock at this point on the trail forms a
minor cave that affords some shelter from the elements.
This particular kind of conglomerate
rock can be seen in various parts of Tippecanoe County, most famously
at Prophet's Rock near Battleground, or at Valley Street in
Lafayette. The following description of this kind of rock is here
excerpted from the 1888 report of the Indiana State Geologist, in the
chapter “Geology of Tippecanoe County”, pages 87-90. It may be
that modern geological science has a different theory of the nature
and origin of this conglomerate rock, I don't know, but if there is I
hope to add it to a future blog post here:
THE DRIFT.
An exhaustive study of the Drift
must be extended over a wide area. Facts must be closely collected
and carefully grouped. Every locality in this widely distributed
formation must be patiently examined and thoughtfully studied.
Geologists can not jump at conclusions, but years of continued
patient study may unfold the mystery. The assertion may be ventured
that no county in the Union affords a more varied exhibit of this
puzzling deposit than Tippecanoe.
Mention has been made of the
ancient valley which crosses the northern part of the county from
east to west, and also the great basin in the central part of the
county. The area of this basin is not less than 250 square miles.
This ancient basin is now filled with gravel, containing a small
proportion of clay, sand and bowlders. The ancient valley is filled
with blue clay and sand.
In Sleepy Hollow, two miles
north-west of Lafayette, on the opposite side of the Wabash
River....(has a place that) is known as the “sand pit”. West of
this about 200 yards is the “stone quarry.” Here an exposure
along the north bluff of the hollow reveals a stratum of sand so
firmly cemennted as to form a hard, durable stone. When it was first
discovered a quarry was opened out here with the expectation of
finding an inexhaustible supply of good building stone. This stratum
of cemented sand is about six feet in thickness, on an average. It
is composed of moderately fine, sharps grains of sand, firmly
cemented together. It hardens, somewhat, on exposure, and, so far as
tested, it proves to be a very good material for foundations for
light buildings. It would be utterly worthless, however, for heavy
structures. While the stratum is six feet in thickness, but a small
portion of it can be procured in suitable sizes for economic use. It
occurs between beds of cemented gravel.
Tenth Street Hollow, at La
Fayette, shows grand exposures of this cemented gravel, sand and
bowlders. Here, as well as at the points already mentioned, these
material are so firmly cemented together as to form immense masses of
solid conglomerate. Tenth Street Hollow is a miniature canon, eroded
by the waters of the Recent Period. The bluffs of this hollow are
high and precipitous. The walls of conglomerate stand up on either
side in picturesque grandeur. Along their perpendicular sides may be
distinctly seen the lines of stratification. Here, at Durgee's Run,
on Perin Avenue, in Sleepy Hollow, on Burnett's Creek, at Battle
Ground, and every point where a view may be obtained of a north or
south wall these lines of stratification may be distinctly seen, and
with a uniform dip to the west of usually about 15 to 20 degrees.
The immense gravel depostis of the Wea Plains, and the corresponding
terrace on the opposite side of the river, embracing more than 100
square miles of territory, at every point observed show clearly that
the whole mass is distinctly stratified; that it is in layers as
evenly and uniformly placed as are the solid rock deposits beneath
it. Wherever the gravel is solidly cemented together these lines of
stratification may be followed the full length of the exposure.
Excavations made in the gravel beds to procure material for road
building always reveal the same facts. And further, it is always
plainly disclosed that there is a slight dip toward the west. This
dip to the west is observed equally on both sides of the river. On
Indian Creek, Laramie Creek, Wild Cat Creek and Wea Creek—wherever
this cemented gravel, sand or bowlders are exposed, the same uniform
westerly dip is observed. The conclusion arrived at here is that
these gravel and sand deposits, forming terraces adjacent to the
river, sometimes called “alluvial terraces” are not river
terraces at all, but that they were formed by the same agencies that
made all the wide plains of Indiana long ages before the Wabash River
traced it serpentine course across the surface. The Tippecanoe
Basin was filled with clay, sand, gravel and bowlders at a period far
remote from that in which the Wabash began wearing a channel through
the hills and rocks of Warren and Fountain Counties, to find its way
to the sea.
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