Transcript Slide 1
Florida Groundwater and Hydrogeology The Florida Platform The edge is defined as where the water depth is at 300 feet. 100 miles west of Tampa 3-4 miles east of Miami The Florida Platform The Florida platform is a miles-thick carbonate bank Freeport Miami Nassau CaCO3 Ice age -300 ft CaCO3 +100 ft Warm period Origins of the Florida Platform Precambian 4.5 Bya to 500 Mya (Earth formation, cooling, oceans, atmosphere, life, oxygen) Paleozoic 500 Mya to 248 Mya Mesozoic 248 Mya to 65 Mya Cenozoic 65 Mya to present Approximately 250 million years ago Breakup of Pangaea Late Triassic, early Jurassic ~200Mya - 250 Mya Rifting phase: Creation of the Atlantic Ocean Approximately 150 million years ago Stable, shallow sea floor Subject to marine sedimentation Sedimentation: settling of particles from a fluid due to gravity For the next several million years the area was dominated by carbonate sedimentation Late Jurassic Carbonate Deposition/Sedimentation Marine Calcium and Magnesium Carbonate CaCO3 MgCO3 Between about 150 Mya and 25 Mya Florida platform was a flooded, submarine plateau dominated by carbonate deposition CaCO3 FL platform * The Eocene and Oligocene Limestone The Eocene and Oligocene limestone forms the principal fresh water-bearing unit of the Floridan Aquifer, one of the most productive aquifer systems in the world Eocene: 55 – 34 million years ago Oligocene: 34 – 24 million years ago Marine Carbonates carbonates Prior to 24 Mya Between 150 and 25 Mya, Florida was dominated by carbonate deposition Continental Influences Sedimentation on the Florida Peninsula Sediments Isolation of the Florida Peninsula sediments sediments Georgia Channel Suwannee Current (similar to Gulf Stream) Isolation of the peninsula from continental influences allowed carbonates to build on the platform for 125 million years Fundamental change came approximately 25 million years ago Events of the Late Oligocene Epoch, approximately 25 Mya Raising of the Florida Platform Lowering of Sea Levels, Interruption of Suwannee Current Suwannee Current +100 ft Rejuvenation of Appalachians, increased sediment load sediments Miocene Epoch: beginning approximately 24 Mya These Sediments were Silicon-based Sands, Silts, Clays, Rocks, and Rock Fragments KAlSi3O8 CaAl2Si2O8 NaAlSi3O8 MgSiO4 Feldspars Olivine Muscovite KAl3Si3O10 They are typically called “siliciclastics” Filling in the Georgia Channel Sediments Early Miocene (~ 24 Mya) Carried by rivers and longshore currents Sediments Rising sea levels allow sediments to become suspended in water and drift over the platform Siliciclastics Covered the Peninsula Silicon-based Deposition of Eocene/Oligocene Limestone (55 – 24 Mya) Raising of the Florida platform Lowering of sea levels, interruption of the Suwannee Current Infilling of the Georgia Channel with sediments derived from Appalachian/continental erosion 5. Sea level rise, lack of Suwannee current. 6. Suspended siliciclastic sediments settle over the peninsula 7. These sediments blanket the underlying limestone forming the upper confining layer for the Floridan Aquifer. 1. 2. 3. 4. Basic Florida Geology Sands sands, silts, clays, rock Limestone Confining unit Water-bearing unit Miocene deposits are siliciclastic: sands, silts, clays, rocks These deposits are known commonly as the Hawthorne Formation. They overlie the Eocene and Oligocene limestone deposits and form the upper confining unit for the Floridan Aquifer. Miocene sediments are non-carbonate marine sediments Megalodon #MG1 Locality: Hawthorne Formation, South Carolina Age:Miocene Virtually flawless museum grade specimen. Perfect serrations, black and gray mottling Price: $785.00 SOLD In Gainesville, Miocene clays tend to be fairly thick and, in many cases, close to the surface 13th st. Alfred A. Ring Park 1801 NW 23rd Boulevard—parking at Elks Lodge The thickness of and depth to Miocene sediments varies 0-500 ft thick in the North-central part of state Up to 40% phosphorus Also contains uranium Uranium decays to Radon OK Generalized Florida Geology Surface features were shaped primarily during the Pleistocene Surface Saliciclastics (sandy) Siliciclastic sediments from the continent settled over the limestone beginning 24 Mya. forming the upper confining unit for the Floridan Clays and Sands (Hawthorne) Limestone originating from the Eocene and Oligocene Epochs forms the water-bearing unit for the Floridan Aquifer. 55 – 24 million years ago Permeability: the ease with which water moves through material Surface Siliciclastics (sandy) (highly permeable) Clays and Sands (low permeability) 55 – 24 million years ago Unconfined aquifer is extensive throughout the state of Florida Low Permeability Confining Unit (poor water movement) The Floridan aquifer is a confined aquifer. The water-bearing unit is permeable limestone. Low permeability rock (confining) The Floridan Aquifer The water-bearing unit of the Floridan Aquifer is a confined, consolidated limestone formation. How does it contain and release water?