GEOLOGY OF FLORIDA

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Lecture : Physiography and Geomorphology of Florida

Walter Schmidt
Chapter 1
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I. Introduction
     A. Landforms are not static in geology
          1. Doctrine of Uniformitarianism
          2. Interpretation
               a. Past configurations
               b. Future configurations
     B. Classification of landforms
          1. Local geologic structures and rock types
          2. Type and rate of erosion
     C. Physiography and geomorphology
          1. Physiography-a description of the features of the Earth
          2. Geomorphology-study of the evolution of landforms
               a. Classification
               b. Description
               c. Nature
               d. Origin
               e. Development
          3. Descriptive (geography) versus interpretive (geology)

II. Florida's Dominant Geomorphic Processes
     A. Marine forces are most important
          1. Erosion and deposition by currents
               a. Flat seafloors
               b. Marine scarps
          2. Ridges and highlands
               a. Erosional features
               b. Depositional features (wind and water)
     B. Marine Influences Forming Terraces and Scarps
          1. Florida Platform
               a. Half above sealevel and half below
               b. Alternately flooded and exposed
          2. Relief
               a. Results in large sealevel effects (low slope)
               b. Low maximum elevation (104 meters in Walton County)
               c. Sediments resulting from marine, eolian, and fluvial processes
          3. Landforms
               a. Negative features
                   (1) estuaries
                   (2) lagoons
               b. Positive features
                   (1) barrier islands
                   (2) coastal ridges
                   (3) coast parallel valleys
                   (4) spits and bars
               c. Marine terraces
                    (1) represent periods of deposition and erosion
                    (2) related to sealevel changes
                    (3) Healy identified eight terrraces
                    (4) methods used for identification
                         (a) topographic maps (1° slopes)
                         (b) physiographic and geomorphic maps
                         (c) stratigraphy, lithology, and granulometric studies
                         (d) fossils (plant and animal)-palynology
     C. Coastal Regions and Associated Landforms
          1. Coastal Zone
               a. Transition from land to water
               b. Complex and dynamic
          2. Main processes
               a. Sealevel changes
               b. Land level changes
               c. Both change
          3. Florida's Coastal Features 
               a. East coast and middle west coast are depositional
                (1) barrier islands
                (2) barrier beaches
                (3) spits
                (4) overwash fans
               b. Southwest Florida Coast
                (1) salt marshes
                (2) mud flats
                (3) marsh grasses
                (4) mangroves
           c. Florida Keys
                (1) Modern coral reef
                (2) Ancient coral reef
           d. Big Bend
                (1) salt swamp and marsh
                (2) drowned karst topography
                (3) near-shore oyster reefs
           e. Eastern Panhandle
                (1) barrier islands
                (2) Apalachicola delta
           f. Western Panhandle
                (1) drowned estuaries
                (2) barrier beaches
    D. Drainage systems

          1. Sheet drainage in the Everglades
          2. Trellis drainage of coast parallel streams
          3. Dendritic drainage in the Northern Highlands
          4. Rectangular drainage in the Suwannee River Basin
          5. Internal drainage in karst areas
     E. Karst Geomorphology: The Pattern of Sinkholes 
          1. Summarized by FGS publications of White (1970) and Lane (1986)
          2. Features
               a. Small sinkholes on planar karst platforms in the Coastal Lowlands
               b.  Rolling hills and star shaped sinks on ridge; the Brooksville Ridge and the Lake Wales Ridge
               c. Isolate collapse sinkholes in buried-karst or newly developing karst
          3. Frequency and type are related to geologic setting
               a. Few sinkholes where competent overburden is greater than about 60 feet (figure 1.9)
                (1) deep
                (2) steep
                (3) cover collapse type
               b. Large, complex sinkhole in escarpment zones (Cody Scarp)
                (1) cover is thinner and irregular
                (2) funnel-shaped over small conduits
                (3) variable types
               c. Lowlands
                (1) many small sinkholes
                (2) sinking streams
                (3) other karst features
                (4) dissolution sinks
                d. Types
                    (1)  solution-no cover
                    (2)  collapse-thin cover; fills as fast as it forms
                    (3)  cover collapse-variable cover; form with rise or fall of water table
    F. Ridges and Highlands
         1. Eroded by stream and marine processes
         2. Sediments represent Neogene fluvial, deltaic, and shallow water marine environments
         3. Sediment sources are southeastern coastal plain and Appalachians forming the siliciclastic coastal plain prograding wedge
         4. Prograding sediments filled in the Georgia Channels at the end of the Oliogocene allowing clastics on to the peninsula
         5. Sealevel variations and near-shore processes modified these deposits leaving the elongated system of upland ridges that we see today.
    G. Wetlands
          1. Defined by:
             a. Hydrology
             b. Vegetation
             c. Soils
          2. Each responds to a different time frame
          3. Types
            a. Coastal marshes
            b. Estuaries
            c. River and stream flood plains
            d. Low-relief plains
            e. Areas with near-surface water tables and high potentiometric surfaces
            f. Areas fed by artesian springs
III. Interesting features
  A. Stream capture: Chattahoochee, Flint, and Apalachicola Rivers
          1. Stream capture by headward erosion
          2. Chipola River occupies the ancestral Chattahoochee River channel
 B. Tectonic deformation inferred from terrace mapping or surface lineaments
 C. Platform Rebound from Carbonate Loss
 D. Disappearing Lakes and Rivers
 E. Topographic Inversion-Brooksville Ridge
 F. Meander Pattern of the Suwannee River–partially entrenched
 G. The Offset Course of the North-flowing St. Johns River
 

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