The Prairie Bluff Chalk is a geologic formation in Alabama and Mississippi.

[2][3] The chalk was formed by marine sediments deposited along the eastern edge of the Mississippi embayment during the Maastrichtian stage of the Late Cretaceous.

It is a unit of the Selma Group and marks the end of the Cretaceous in Alabama.

It is hypothesized that this event, along with faulting and liquification of the Prairie Bluff Chalk, is related to the meteorite impact at the Chicxulub crater site, directly south, across the Gulf of Mexico, from the formation.

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