Lost River - Karst Information Portal

2007 NSS Convention Guidebook
is incised deeply into the Crawford Upland,
attesting to its long history as an active stream
draining the Mitchell Plain area prior to the
Lost River becoming part of a subterranean
network. Without the westward retreat of
the upland and escarpment, the limestones
under the Mitchell Plain would not have
been exposed to the surficial karst processes,
and the Lost River basin would not exist as
it does today. Apparently, the Lost River had
a Tertiary or earlier predecessor which was
purely a normal antecedent stream eroding and
downcutting the upland. This is comparable to
the many antecedent streams in mountainous
areas which have carved deep canyons, yet
clearly cut across structure. The Lost River cuts
perpendicular to the north-striking (and westdipping)
rocks of the Crawford Upland.
Proceed west along the flank of the
escarpment. Along the road are good northerlylooking
(right) views of the Lost River basin
(Figure 49). Due north 5.5 miles is the upland
outliers on the north side of the basin.
Retreat of the Chester Escarpment and
Crawford Upland
Frequently in the above discussion,
mention has been made of the retreat of the
Chester Escarpment and Crawford Upland
being linked to terra rosa origination. During
the many studies emanating from the ill-fated
Soil Conservation Service Lost River basin
projects of the early to mid 1970s, the Crawford
Upland and Mitchell Plain soils were studied
extensively by retired IU soil geomorphologist
Dr Robert Ruhe and his students, notably John
Bassett, MS, Dr Robert Hall (retired from IU-
Indianapolis) and Dr Carolyn Olson. These
phenomena are occurring on the slope upon
which the road is built. Note how the toeslopes
resemble the scarp-front pediment erosionaldepositional
surfaces of the arid western United
States. Active escarpment retreat is occurring
here, and the arid pediment model is modified
(and obscured visually) due to the much wetter
climatic conditions of Indiana and the resulting
vegetative slopes. Various sized clasts of Chester
rocks ranging from cobbles to boulders can be
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found on top of, and mixed in with, limestone
erosion surfaces and soils, indicating down
slope transport.
These researchers conducted investigations
in this vicinity, which led to the conclusion
that the sloped surface of the escarpment is
shedding sediments onto the karsted Mitchell
Plain which is increased areally as the shedding
slope retreats to the west. Part of solving the
origin problem was first recognizing that the
volume of terra rosa soils far exceeds the volume
of residual material that could have been
deposited from the limestones eroded from the
Mitchell Plain. Another facet was addressing
the source of the iron which makes the terra
rosa, well, rosa, since the limestones have a low
natural iron content. Since the Mitchell Plain
was never glaciated, the soils had to have a local
origin (except for wind blown glacial silt known
as loess). At the bottom of the escarpment
slopes are piles of the (loess-covered) shedded
clastic and iron-rich material (residuum) which
is the parent material for terra rosa soils. Local
fluvial and paludal depositional patterns greatly
influence the depth and types and specific
nature of the soils. The thicker terra rosa soils of
the eastern and central Mitchell Plain are older
than those of the western Lost River basin and
have soil profiles which are dramatically more
developed. The sinkhole-plain soils have also
been greatly eroded by the Lost River and other
sinking stream/cave systems, which post-date
the retreat and Mitchell Plain development.
See the numerous articles by Ruhe, Bassett,
Olson, and Hall for more information.
Go west about 1.2 miles and stop at the
three-way triangular intersection with County
Road 100W. Bear left (south) up the hill a short
distance and prepare to turn right (west) at top
of hill onto Sandy Hook Road. This road is on
top of the Crawford Upland and the escarpment
in this area. A good vista overlooking the Lost
River basin is near a log cabin. The Mitchell
Plain is about 200 feet below the road at this
point. Note the cedar trees growing on the
toeslope (pediment) sandy soils. Continue
on this road in a winding westerly direction
for about 2 miles until the road bends right,