(JACKSONIAN or PRIABONIAN)
Most of the bedrock underlying the Dougherty Plain is a formation called the Ocala Limestone. The sinkholes, round ponds and swamps, and limestone cliffs along the major streams and rivers in the region result from solution of this limestone in the warm, wet climate of southwest Georgia. Outcrops of the rock are common in streambanks, as at the Flint River near Albany in the photo above left. Man-made exposures occur in the several quarries from which the rock is mined. However, over much of the region where this is the surface "rock", it has been deeply or completely weathered to a deep red soil known as 'terra rosa', as in the photo above right, taken in Sumter County. This soil makes for very rich farmland.
Unlike other limestones in southwest Georgia, the Ocala is usually a fine-grained sediment, ranging from fairly soft mud-sized lime to fine sand-sized lime grains. It is very rich in fossils at most places, including a high diversity of marine organisms. The photo at left shows the fine texture of the limestone, as well as the smooth scallop Amusium ocalanum that is so common in the Ocala.
Study of the sediment in the Ocala, and of the fossils it contains, indicates that it was deposited on a fairly typical carbonate "rimmed shelf" not unlike the modern continental shelf of south Florida, off the Keys. Much of the "Environment" section of this webpage is devoted to the fossils' part in interpreting the sediments of this shelf.
Common fossils in the Ocala include the following:
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