Blake Plateau

The Blake Plateau is a large, relatively shallow (eight hundred to twelve hundred meters) carbonate bank that lies two hundred miles off Charleston on the continental shelf. It runs from near Cape Hatteras in North Carolina, past South Carolina and eastern Florida, to just north of the Bahamas. At the eastern, seaward edge of the plateau, the Blake Bahamas Scarp descends eighteen thousand feet toward the abyssal plain below. This scarp forms the highest geologic structure east of the Rocky Mountains.

The structure of the Blake Plateau clearly illustrates the process of the North American/African separation beginning in the Late Triassic period (208 million years before present) as well as the development of continental shelves generally. It also provides additional evidence through recent sediment and fossil analyses of the events occurring at the Cretaceous/Tertiary boundary that led to the great mass extinctions of many animal and plant species of that time.

The Blake Plateau began to form as the North American plate disengaged from the African plate in the Late Triassic period, forming the Atlantic Ocean. Beginning with rifting that shattered the subsurface, lava flows and down-faulted valleys formed at the edges of the continents and offshore. Later sediments formed a progressively thicker wedge seaward. As rifting continued during the Jurassic period, the carbonate deposits formed in what was then a warm, shallow sea: the early Atlantic Ocean. The weight of the deposits of sediments and of the carbonates bent the crust downward, which allowed more deposition, allowing the carbonates to reach a thickness of more than thirty thousand feet (ten kilometers).

The plateau is of economic interest because of the 1970 and 1996 discoveries of immense deposits of hydrocarbons in the form of methane and methane hydrate that may be developed commercially in the future. Many geologists now believe that this immense carbonate bank may contain huge quantities of usable methane gas.

Murphy, Carolyn H. Carolina Rocks! The Geology of South Carolina. Orangeburg, S.C.: Sandlapper, 1995.