Birth of Bahamas

So where do we begin? (geologically, of course).


[...to kill time while waiting for Katie to get her lab stuff done]

Okay, and so the North American (continental) and Atlantic (oceanic) decided to move westwards 200Ma (in layman's terms that is million years ago), thanks to the mantle currents during the opening up of Mid Atlantic Ocean Ridge, hence creating shallow water area at their junction.

This allows CARBONATE sediments to form.

The crust was thin enough to 'sink', hence allowing accumulation of carbonate sediments down to 5,800m deep, as proven by boreholes being drilled.

Boreholes! (I digress...)
So as of 1996 (?), there's more only 12 boreholes that is more than 3000m deep. And:

• None of them has surpassed crustal rocks
• The bottom of the deepest wells still shows shallow-provenance rocks
• None are older than Cretaceous (135Ma) except Great Isaac's well (NW of Great Bahama Bank) which is sourced from North American continent.
• All are of marine origin except the red beds, fossil soils and aeolian limestone (sand dune rock) found in shallow wells and in the ridges

So what do all these tell us? That the Bahamas have experienced the same geographical conditions and underwent the same shallow marine environment from the time of formation until recent Ice Age, i.e. for the whole of the Bahamian history.

SoF = Straits of Florida; OBC = Old Bahama Channel; CAP = Crooked–Acklins Platform; TOTO = Tongue of the Ocean [Source: Visible Earth NASA]

So why is Bahamas remarkably unique? It's their great thickness and the absence of other rocks! Thinking about how the rocks from 5000m deep (in the past) are the same as those found (and are still forming) on the surface today!

[Fiona and Katie will surely be able to write a book about it but from my mere undergraduate knowledge there's only so much I can tell, plus it's nearly 12 midnight in the department and it's getting really creepy]

The explanation for this is the interaction of two parameters;

1. RAPID production of carbonate sediments
2. SLOW subsidence of crust where Bahamas stands, allowing shallow marine sedimentation to persist without drying out to die, or drown

So, this is the gist of it :)

- D

[ref: Sealey, N. (1995)Bahamian Landscapes: An introduction to the Geography of the Bahamas]