FLORIDA –BAHAMAS MESOZOIC PASSIVE MARGINS: FINDING AN AREA OF SEA LEVEL ABSOLUTE FLUCTUATIONS

The complete meltdown of the Greenland and Antarctic ice sheets would raise sea level 65 meters, whereas a partial meltdown only a few tens of meters. Eustatic sea level rates of changes in Greenland since 2003 show a net ice mass reduction of 96 gigatons per year.

For comparison rate of change analysis absolute measurements in historical eustatic sea level fluctuatious are critical in determing sea level rise factors of causation. Overall worldwide sea level geologic measurements (Vail Curves) are expresed in relative sea level changes. thus, finding an area of absolute measurements for sea level change is the challenge.

Since carbonate reefs reach the top of the subsea or photic zone, carbonate reef growth is an ideal indicator of sea level change. Carbonate deposits at the Caribbean – South America plate boundary are a prime example that plate motion can greatly supersede sea level fluctuations. The best areas to use carbonate reef data is along the Florida-Bahamas-Caribbean passive margins of the Atlantic basin, where Neogene tectonics and carbonate deposition were stable. The carbon dioxide levels were much greater above the K/T boundary, creating an environment devoid of significant carbonate buildups. The earliest significant quantitative sea-level rate of change data is derived from wells drilled into stable carbonate platforms of the late Neogene 2-7 Ma, when carbon dioxide levels decreased in the atmosphere. Cores show rates of paleo sea level rise averaging 10 to 20cm/100yr versus currently between 17-32cm/100yr. The rate increase has nearly doubled within the past 14 years. This increased rate if change in sea-level has been recently highlighted at the 2007 Intergovernmental Panel on Climate change in Paris, France.

Through all the erratic temperature swings over the past 4,000 years geochemical data from Holocene reef cores from Florida show a sea level rise of 12cm/100yr., typical of stable geological and climatological periods.

The Questions remains: Is the current rate change of sea level significant or, just another unanswered anomaly from the cycle curve?