Lost River - Karst Information Portal

Preglacial Regional Drainage and
Glacial Origin of Ohio River and
Regional Geology
The several glacial meltwater episodes
greatly impacted the formation of the Ohio
River and reestablished over drainage patterns.
As seen in Figure 32 from Powell’s (1965)
publication “Geology of the Falls of the Ohio
River,” in mid Tertiary times the Knobstone
Escarpment was not breached by the river.
The river headed within the Norman Upland/
Mitchell Plain area in what is now Kentucky,
with the Indiana side being drained by what
was called the Blue River, and Indian, Buck, and
Mosquito creeks. So downstream of the Knobs
the current valley is very much related to the
pre-glacial valley as seen in the big entrenched
meanders such as Horseshoe Bend. By the late
Tertiary, the Knobstone had been breached by
headward erosion by the ancestral Ohio. These
glaciations and subsequent huge meltwater
Geology Field Trip
discharges lead to the formation of the modern
Ohio River during the Pleistocene.
The Falls of the Ohio vicinity is the only
area on this field trip which has any known
glacial deposits (Figures 32 & 33). The Falls
vicinity is developed upon multiple terraces
underlain by sand and gravels of Wisconsinan
and possibly Illinoian age, with glacial lake
clays in an overall area of Quaternary alluvium.
The Illinoian glacial advance (about 100,000
years ago) was unable to entirely overcome
the abrupt Knobstone Escarpment on the
east, or the Crawford Upland on the west,
thus leaving the vast bulk of the karsted
Mitchell Plain unglaciated. The Wisconsinan
Glaciation, which ended about 15,000 years
ago, terminated in central Indiana.
The physiography of the valley area and
topographic cross-sections of the valley are
shown in Figure 33 and Section B-B’ is through
the Falls.
Figure 32. Maps showing the drainage routes in the vicinity of the Falls of the Ohio River during mid-Tertiary
time (A) late Tertiary or early Pleistocene time (B), and Pleistocene time (C) ( from Powell 1965).
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