Klintar: Ancient Marine Reefs of the Wabash Valley (GM-17)
Scattered throughout the Wabash sluice-way between Peru and Huntington are numerous dome- and mound-shaped hills, which are remnants of ancient coral reefs. These reefs may be partly of completely isolated as rocky hills, or they may form bluffs along streams. These features are called klintar (the singular is klint) after similar fossil reefs on Gotland Island in the Baltic Sea.

The Wabash Valley klintar were formed in Silurian seas that covered the area more than 400 million years ago. Later deposition buried them to unknown depths. After regional uplift, weathering and erosion removed overlying strata, and parts of these ancient reefs were gradually exposed. Rock materials left behind by Ice Age glaciers reburied many of these reefs, and some of them were again partly exposed by postglacial erosion. Hanging Rock near Largo is a klint. Several limestone quarries in or near the Wabash Valley produce reef rock for aggregate.

Our Hoosier State Beneath Us: Geomorphology