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The Hawthorn Group is a stratigraphic unit that includes several geologic formations of Late Oligocene to Pliocene age in North Florida, United States. It is known for its phosphate rock resources, and for its rich assemblages of Neogene vertebrate fossils. It was originally called the Waldo Formation by L.C. Johnson of the United States Geological Survey in 1887, and later became the Hawthorne Group named for Hawthorne, Florida, where its phosphate-rich rock was quarried and processed for use as fertilizer.[1]

Hawthorn Group
Stratigraphic range: Miocene
Sub-units(See text)
OverliesOcala Limestone
Thickness> 330 feet
RegionNorth Florida
Country United States
Type section
Named forHawthorne, Florida
Named byL.C. Johnson, 1887
Location of the Hawthorn Group within Florida (in red).



Period: Neogene
Epoch: Miocene
Faunal stage: Chattian through early Blancan ~28.4 to ~2.588 mya, a period of 25.512 million years


The Hawthorn Group extends from Suwannee County in the north and southward to Hernando County. It encompasses in part the counties of Gilchrist, Levy, Dixie, Citrus, Sumter, Alachua and Marion County. The Hawthorn is also present below undifferentiated sediments (TQu) as well as the Tamiami Formation from Polk County south through Highlands, Glades, Hendry, Dade, Collier, and Monroe County at depths ranging from mean sea level near Polk to below 600 meters in Monroe Co.[2] The Hawthorn overlies Ocala Limestone[3]







  1. ^ Geology of Florida: Miocene to Holocene. University of Florida Geology
  2. ^ USGS Florida Geology
  3. ^ Glen L. Faulkner, Geological Survey (U.S.), United States. Army. Corps of Engineers, Geohydrology of the Cross-Florida Barge Canal area, Tallahassee, 1973.