The limestone that comprises the Banks has been accumulating since at least the Cretaceous period, and perhaps as early as the Jurassic; today the total thickness under the Great Bahama Bank is over 4.5 kilometres (2.8 miles).
The limestone that forms the Banks has been accumulating since at least the Cretaceous period, possibly as early as the Jurassic; today, the total thickness under the Great Bahama Bank exceeds 4.5 kilometers (2.8 miles).