Sinkholes in the karst area of south-central Indiana contain, from oldest to youngest, (1) sandy calcareous mud; (2) red clay and red silt, both facies commonly known as terra rossa; (3) chert gravel; (4) loess; and (5) yellowish-brown silt derived from loess.

The nature and distribution of litho-stratigraphic units suggest the filling of bedrock basins. The terra rossa in the sinkholes is primarily a transported sedimentary deposit. The source of much of the terra rossa sediment is probably the adjacent uplands.

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