Hawthorn Group, Coosawhatchie Formation

The Coosawhatchie Formation is exposed or lies beneath a thin overburden on the eastern flank of the Ocala Platform from southern Columbia County to southern Marion County. Within the outcrop region, the Coosawhatchie Formation varies from a light gray to olive gray, poorly consolidated, variably clayey and phosphatic sand with few fossils, to an olive gray, poorly to moderately consolidated, slightly sandy, silty clay with few to no fossils. Occasionally the sands will contain a dolomitic component and, rarely, the dominant lithology will be dolostone or limestone. Silicified nodules are often present in the Coosawhatchie Formation sediments in the outcrop region. The sediment may contain 20 percent or more phosphate (Scott, 1988). Permeability of the Coosawhatchie sediments is generally low, forming part of the intermediate confining unit/aquifer system.
State Florida
Name Hawthorn Group, Coosawhatchie Formation
Geologic age Miocene
Lithologic constituents
Major
Unconsolidated > Fine-detrital > ClayWithin the outcrop region, the Coosawhatchie Formation varies from a light gray to olive gray, poorly consolidated, variably clayey and phosphatic sand with few fossils, to an olive gray, poorly to moderately consolidated, slightly sandy, silty clay with few to no fossils.
Unconsolidated > Coarse-detrital > SandWithin the outcrop region, the Coosawhatchie Formation varies from a light gray to olive gray, poorly consolidated, variably clayey and phosphatic sand with few fossils, to an olive gray, poorly to moderately consolidated, slightly sandy, silty clay with few to no fossils.
Minor
Unconsolidated > Fine-detrital > SiltWithin the outcrop region, the Coosawhatchie Formation varies from a light gray to olive gray, poorly consolidated, variably clayey and phosphatic sand with few fossils, to an olive gray, poorly to moderately consolidated, slightly sandy, silty clay with few to no fossils.
Incidental
Sedimentary > Carbonate > LimestoneOccasionally the sands will contain a dolomitic component and, rarely, the dominant lithology will be dolostone or limestone.
Sedimentary > Carbonate > DolostoneOccasionally the sands will contain a dolomitic component and, rarely, the dominant lithology will be dolostone or limestone.
Sedimentary > Clastic > Mudstone > Shale > Phosphatic-shaleVariably clayey and phosphatic sand with few fossils, to an olive gray, poorly to moderately consolidated, slightly sandy, silty clay with few to no fossils.
References

Scott, T.M., Campbell, K.M., Rupert, F.R., Arthur, J.D., Missimer, T.M., Lloyd, J.M., Yon, J.W., and Duncan, J.G., 2001, Geologic Map of the State of Florida, Florida Geological Survey & Florida Department of Environmental Protection, Map Series 146, scale 1:750,000.

Scott, Thomas M.P.G. #99, Text to Accompany the Geologic Map of Florida, Open-file Report 80, Florida Geological Survey, 2001.

Scott, T.M., 1988, The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological Survey Bulletin 59, 148 p.

NGMDB product
Counties Alachua - Baker - Bradford - Columbia - Lake - Levy - Marion - Orange - Seminole - Union