Arcadia Formation

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Arcadia Formation
Stratigraphic range: Miocene
Type Geological formation
Unit of Hawthorn Group
Sub-units Tampa Member
Overlies Ocala Limestone and Avon Park Formation
Thickness 600 feet
Primary limestones, dolostone, sand, clay
Region Central Florida
Country  United States
Extent Pasco-Sarasota counties
Type section
Named for Arcadia, Florida
Named by T. M. Scott, 1988
Location of the Hawthorn Group within Florida (in red).

The Arcadia Formation and its sub-unit, the Tampa Member, are Late Oligocene geologic formations in North Florida, United States. It is part of the Hawthorn Group.


Period: Paleogene to Neogene
Epoch: Early Late Oligocene through Pliocene
Faunal stage: Chattian through early Blancan ~28.4 to ~2.588 mya, calculates to a period of 25.512 million years


The Arcadia Formation and Tampa Member is located southwestern flank of the Ocala Platform from Pasco County and southward in to Hillsborough and Sarasota County, Florida. The Tampa Member and the lower part of the Arcadia Formation form the upper part of the Floridan Aquifer system in parts of southern Florida.[1]


The Arcadia Formation is composed of limestones and dolostones which are yellowish gray to light olive gray to light brown in color. The texture is micro to finely crystalline with varying sandy, clayey limestones and dolostones containing phosphate. The clays are yellowish gray to light olive gray in color. They are moderately hard as well as sandy, silty, phosphatic and dolomitic. Silicified carbonates and opalized claystone have also been found.[2]

Tampa Member[edit]

The Tampa Member consists predominantly of limestone with subordinate dolostone, sand and clay very similar to that of the subsurface limestone part of the Arcadia Formation. There is considerably less phosphate. The color is white to yellowish gray. It is fossil bearing and variably sandy and clayey mudstone, wackestone, and packstone with little to no phosphate grains. Sand and clay beds are like those in the undifferentiated sediments of the Arcadia Formation.


The Arcadia Formation proper contains molds and casts in dolostone containing mollusks. The Tampa Member contains mollusks and corals in molds and casts with silicified pseudomorphs and shell material.


  1. ^ Miller, J. A., 1986, Hydrogeologic framework of the Floridan aquifer system in Florida and parts of Georgia, Alabama and South Carolina: United States Geological Survey Professional Paper 1403-B, 91 p. plus maps.
  2. ^ Scott, T. M., The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological Survey Bulletin 59, 148 p.