The Bahamas is composed of 100% shallow marine and terrestrial facies.
Growth occurs by lateral accretion and is dependent on sea level, platform and shelf margin configuration, and the orientation of sediment transport sources.
Carbonate islands originate by shoaling during stormy periods when sediments blanket ing the platform first accumulate as shoals, and progessively emerge into beach ridges and dunes. During low stands, dune deposits indurate and form nucleation points or anchors for subsequent deposition during high sea levels.
Growth is self regulated: lateral growth on the platform means less source area for sediment production. San Salvador appears to have nearly completed its lateral growth and subsequent growth will be vertically, if accommodated by subsidence or a higher sea level in order to oversteep the high ridges surrounding the island.
Four Phases of landform development:
Phase I: (350 – 180 ka)
Deposits corners
(as small ridges) of San Sal.
Other phases tied to/modified by these “anchors.”
Most significant
cavess are within these deposits.
Phase II: (132 – 120 ka)
Early Sangamonian
Interglacial (Sea Level Rising) Caternary Ridges – larger and higher farther inland.
Between the “anchors”
Long smaller ridge on
the north and west side. (Sandy point-Cockburntown-Sue point-Reckley point).
Stable shoeline on the more tranquil side of San Sal.
Phase III:
(80 ka)
Late Sangamonian (Sea Level only slightly below today) High promontories on the
eastern margin of San Salvador. Lie seaward of all other ridges and form the anchors for
subsequent caternary development. From 80 to 12 ka sea level retreats during the Wisconsin
glacial period.
Phase IV: (5 – 3 ka)
Lower and simpler ridges around nearly the
entire circumference of San Sal. Primarily on the eastern edge of San Sal and are
caternary on the Phase III and older anchors.
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