I. Evolution of Florida’s Margins
    A. Early Platform Development
        1. Florida-Bahamas Platform
            a. Late Jurassic to Early Cretaceous was one of the most extensive carbonate systems in Earth’s history
            b. Stretching 7000 km from N to S along the eastern coast of North America, reaching Canada (fig 11.2)
            c. Represents a "gigaplatform" or Great Mesozoic Carbonate Bank
            d. Associated with early Mesozoic rifting and sea-floor spreading between North America and Africa and formation of the proto-Atlantic
            e. Also associated with late Triassic and early to middle Jurassic rifting and spreading that formed the Gulf of Mexico
            f. Factors that may have caused a shut-down of carbonate formation on theFlorida-Bahamas        Bank
                1. Eutrophication of seawater
                2. Plate migration to colder climates
                3. Burial by siliciclastics from Appalachians
                4. Multiple sea level variations
                5. Combinations of these factors
            g. Peninsular Arch may have divided Gulf and Atlantic depositional basins (made up of Paleozoic to late Jurassic age rocks)
            h. Modern carbonate deposition limited to SW Fla. and Bahamas results from
                1. Long residence time in tropical climates
                2. Separation from source of clastics
                3. Absence of environmental stresses (upwelling, schizohaline waters, etc.)
    2. Northern Boundary of the Florida Platform
        a. Georgia Channels (Suwannee Saddle in Fig. 11-3) –the carbonate-clastic interface is the northern boundary
        b. Related to depocenter that formed in the Jurassic
        c. Strong northeasterly flow in the Early Cretaceous through the Suwannee Strait
        d. From Late Cretaceous to Paleogene the Suwannee Strait produced a sharp facies boundary
        e. Straits filled during Oligocene low stand
        f. Siliciclastic and authigenic sediments were distributed E-W by transgressions and regressions
        g. N-S sediments basically by longshore drift of Piedmont derived materials
    3. Eastern Boundary of the Florida Platform and Separation from the Bahamas Bank
        a. Graben hypothesis—carbonates formed on structural highs and lows associated with horst and graben formation
        b. Leg 101 hypothesis—little or no structure required; just a massive carbonate bank with shallow water carbonates
        c. Mid Late Cretaceous orogenies fractured the basin with the detachment of Florida and the Bahamas and the formation of the Straits of Florida
        d. Developed into a windward, reef dominated, carbonate bank margin
        e. Features affecting development:
    1. SE Georgia Embayment and related coastal morphology
    2. Sanford High resulting in Miocene upwelling and phosphogenesis
    3. Karstification of Paleocene, Eocene, and Oligocene limestones; formed during late Oligocene and early Miocene low stands
    4. Western Boundary of the Florida Platform
        a. Defined by the West Florida Escarpment
           1. A high relief (up to 2 km), erosional slope
           2. A westward dipping flexure related to crustal thickness that focused sediment accumulation with the resultant carbonate ramp formation
            3. By-passed siliciclastic sediments occur in deep sea fans and are related to the MCU /MCSB
    5. Southern Boundary of the Florida Platform
        a. Defined by the Straits of Florida
            1. Original megabank extended across the current straits into northeastern Cuba
            2. Fracture zones and transform faults associated with sea floor spreading forming the Gulf of Mexico
            3. From late Cretaceous to mid-Eocene, collision of Cuba with Florida resulted in a foredeep now occupied by the southern Straits of Florida

II. Drowning of the West Florida Margin
    A. Lithologies indicate a rapid rise in sea level; west Florida Platform became a carbonate ramp
    B. Upwelling can displace shallow water carbonate conditions (may be replaced by shales (not in Florida) or phosphate (occurs on the WFS)
    C. Drowning seems to have resulted from a combination of shelf subsidence and sea level rise fast enough that the fringing reefs could not "keep up"; not a local event, but occurred at various sites around the world
    D. General westward retreat of the shoreline from late Oligocene to early Miocene
    E. Causes-rising (aggradation) vs. lowering (progradation)
        1. Greenhouse to icehouse transition causing eustatic sea level changes; lowering in late Oligocene and parts of the Miocene
        2. Closing of the Georgia Channels and resultant current modifications (Loop current formation)
        3. Mass Wasting—large scale slides (three or more) on the scarp during Miocene time
        4. Loop current intensification
            a. Closing of the Isthmus of Panama
            b. Redirecting Gulf and Caribbean currents
            c. Middle Miocene unconformities and changes in lithologies
            d. Mid-Miocene upwelling onto the Florida Platform
    F. West Florida Escarpment
        1. Extends from DeSoto Canyon to the south Florida Straits
        2. Undergoing erosion at variable rates
        3. Erosion processes may include some reactive fluids that are migrating to the scarp face and then reacting to chemically weaken the rocks
        4. Weakened rocks then fail by mass wasting

II. Quaternary and Modern Shelf-Slope Systems
    A. West Florida—low shelf and slope gradients characterize this area
        1. Depocenters often are associated with karst features that may have formed during low sea level stands (Tampa Bay and Charlotte Harbor)
            a. Lines of sinkholes
            b. Old spring discharge features
            c. Ancestral stream channels
        2. Reefs account for significant topographic features and are controlled by bottom topography
        3. Loop current may aid reef by raising temperature, but could cause problems with nutrient upwelling
        4. Sediment facies tend to follow bathymetry with siliciclastics introduced from the Mississippi Delta by loop currents
        5. Carbonate sediment facies vary in texture and composition with depth and distance from shore
            a. Molluscan sands
            b. Coraline-algal sands
            c. Ooids
            d. Coated grains
    B. South Florida
        1. Area of active sediment transport off the shelf
        2. Mixture of deep and shallow water sediments
        3. Mostly carbonates (86%) that is organically derived
        4. Many buried surfaces due to varying sea level stands
    C. East Florida
        1. Siliciclastics over old carbonate platform
        2. Composition varies with latitude from qtz to carbonate; carbonates from molluscan to coraline-algal
        3. Mostly silica to Lake Worth, then carbonate further south
        4. Miami to Lake Worth shelf is narrow (few kms) and has three or four linear rock ridges representing extensive relict reefs; these features were terminated in the Holocene
        5. Florida-Hatteras Slope is not significantly erosional south of Cape Hatteras with the exception of the Miami Terrace which extends north about 40 km from Miami
        6. Northern Straits of Florida are the site of "lithoherms" hydrodynanically streamlined coral reef tracts oriented in the strong, north flowing Florida Current; these features were actively accreting during the Pleistocene

III. Conclusion
    A. A lot remains to be learned about the Florida Shelf Area.