Bulls Scarp

Bulls Scarp is an uneven rocky cliff located approximately 66 miles to the east of the South Carolina coast.  This sloping underwater feature is on the edge of the continental shelf, and it covers about 20 square miles.  Today, Bulls Scarp varies in depth from 42 yards to 220 yards beneath the surface of the sea, depending upon the height of its rocky outcroppings.  But during the last Ice Age between ~24,000 BP-~16,000 BP, it was above sea level because the Laurentide Glacier had advanced over all of eastern Canada, locking up a great quantity of earth’s atmospheric moisture.

Sonar image of Bulls Scarp, about 66 miles east of the South Carolina coast.  This image was taken by researchers from the College of Charleston.  20,000 years ago, this was a rocky location right at sea level and it probably hosted breeding colonies of walruses, seals, and sea birds.  Note how it stuck out into the ocean like a kind of natural pier.

Bulls Scarp fascinates me because it represented an environment that no longer exists anywhere in southeastern North America.  The closest above sea level cliffs today are in Maine.  Scientists from the College of Charleston believe Bulls Scarp would have provided favorable habitat for marine mammals such as seals and walruses.  Fossils of both have been found near Charleston.  (See: https://markgelbart.wordpress.com/2011/01/28/seals-and-walruses-off-southeastern-north-americas-pleistocene-coast/).  Puffins and other sea birds nested here as well, and oyster reefs attached to rocks would have been abundant.  Researchers think these resources may have attracted paleo-indians.  Bulls Scarp also offered rock shelters, stone for tool-making, and freshwater springs.  Herds of mammoths, bison, horses, and llamas likely wandered all the way to the coast, and Indians following this game may have discovered these seaside cliffs.  Most of the continental shelf that was above sea level during the last Ice Age has been eroded by currents and wave action, destroying potential archaeological sites, but Bulls Scarp may have lag deposits containing fossils and human artifacts because the rocky outcroppings served as an impediment that trapped sediment. Scientists have identified it as a likely site where Clovis artifacts may be found.

Walruses on a rocky shore off the coast of Alaska.  Strange as it may seem, an area off the coast of what today is South Carolina likely had a scene just like this 20,000 years ago.

A great variety of environments existed on the exposed continental shelf between Bulls Scarp and what today is the modern shoreline.  The climate was on average cooler and drier, though not especially cold during winter, thanks to the nearby Gulf Stream.  Lightning-induced wildfires were infrequent while draughts were common.  These climatic conditions favored prairies and scrub oak thickets.  Pine savannahs and river bottomland forests were less common than they are today.  “Sand dune fields” and Carolina bays formed on the northeast side of the braided rivers flowing on the shelf.  Rivers didn’t meander during this time period, but instead were shallow and clogged with sandbars.  Grassy marshes occurred near springs, and cypress swamps were relict habitats on low poorly drained sites.

When the Ice Age ended,  the Laurentide Glacier melted rapidly, and sea levels rose at an astonishing rate—40 yards per year.  Ocean front condos would have been a really bad investment then.  Cypress tree stumps found 19 yards below modern sea level date to 11,500 BP.  The Atlantic Ocean inundated cypress swamps and all the other types of environments mentioned above within a few thousand years.  Modern sea level was reached about 6,000 years ago. 

We can study the ocean floor off the South Atlantic Bight and imagine what it used to be like, but for me it’s not nearly as satisfying as it would be to have actually seen it.  The paleo-indians didn’t enjoy our modern technological wonders, but they did get to see interesting pristine landscapes.

Reference:

Lepper, Brad

“Paleolandscapes of the South Atlantic Bight”

Mammoth Trumpet 29 (3) July 2014

 

 

Tags: Bulls Scarp, Exposed continental shelf during the Ice Age, Seals and Walruses, underwater cliffs off the South Carolina coast