The Edisto Beach Fossil Site

Approximately 47,ooo years ago, the Laurentide glacier began expanding over what’s now Canada.  Much of the water that existed in the atmosphere became trapped in this growing sheet of ice.  As a result of decreasing precipitation, the Atlantic Ocean receded many miles to the east of what today is the coast of South Carolina and other ocean-bordering states.  Somewhere to the east of what would become Edisto Beach 40,000 years later, grass, shrubs, and finally trees colonized the new top soil that had formed from sea bird guano, plant detritus, pulverized shells, sand, and river deposited mud.  This soil built up on top of a fossiliferous geological formation dating to the early Miocene when the area was deep under the ocean.  The later Pliocene and early Pleistocene strata, for some reason, washed away, creating what geologists refer to as an unconformity where the late Pleistocene strata overlay the Miocene–strata from the ages in between is missing here.  For some unknown reason conditions were favorable for fossilization here, and many Pleistocene age vertrebrate fossils became preserved over thousands of years.

Now, the glacier has melted and the Atlantic Ocean has once again advanced.  Strong currents blast through both the Pleistocene strata, and the Miocene formation, eroding slabs of fossils into the sea where the waves carry them to the shore.  Edisto Island is a productive fossil site, albeit the fossils are from three different ages and are totally mixed, so that Miocene and Holocene marine fossils are found right next to Pleistocene land vertebrate specimens.  Shark’s teeth, including those of the giant great white shark, Carcharodon megalodon, are often discovered here, but perhaps the list of Pleistocene mammals recovered from this beach and close offshore is even more impressive.  Here’s the list:

Opposum–Didelphis virginiana

Beautiful Armadillo–Dasypus bellus

Giant Armadillo–Holmesina septentrionalis

Glyptodont–Glyptotherium floridanum

Jefferson’s ground sloth–Megalonyx jeffersonii

Harlan’s ground sloth–Mylodon harlani

Dire wolf–Canis dirus

Gray fox–Urocyon cinereoargenteus

Florida spectacled bear–Tremarctos floridanus

Raccoon–Procyon lotor

Saber-tooth–Smilodon fatalis

Lion/Giant panther?–Panthera leo atrox

Cougar–Puma concolor

Bobcat–Lynx rufus

Walrus–Odobenus (cf) rosmarus

Gray seal–Halichoerus grypus

Monk seal–Monachus tropicales

Giant beaver–Casteroides ohioensis

Beaver–Castor canadensis

Porcupine–Erethizon dorsatum

Extinct capybara–Neochoerus pinkneyi

rabbit–Syvilagus sp.?

False killer whale–Psuedo crassidens

Bottlenose dolphin–Tursiops (cf) truncatus

Sperm whale–Physeter sp.?

an undetermined species of baleen whale

Tapir–Tapirus (cf) veroensis

Long-nosed peccary–Mylohyus nasutus

Stout-legged llama–Paleollama mirifica

White tailed deer–Odocoileus virginianus

Elk–Cervus elephas…southernmost record

Bison–Bison (cf) antiquus

Manatee–Trichechus sp.?

Mastodon–Mammut Americanum

Mammoth–Mammuthus columbi

Edisto State Park

I chose to prospect for fossils here because it’s a publicly accessible area, requiring no special permission, and an evening in nearby Charleston would satisfy my wife who is not at all interested in fossils.

Tons and tons of sea shells cover Edisto Beach, and they’re concentrated in many areas such as depicted in the following two photos.

I collected about ten pounds of sea shells, but none that I could definitively call a fossil, though a few of them can be categorized as maybe fossils.  Here are the ones I brought home with me.

The following photos are of what’s probably part of a lag deposit–stone and possibly small bones cemented together with sea shells–a cockle and two oysters.  Perhaps it was part of the Pleistocene-aged deposit that contains all the specimens of mammals washing ashore.

The cockle shell below, next to two oyster shells, suggests relatively great age.  It has a blueish-gray color different from most of the other sea shells and has invertebrate bore holes, indicating it had been buried under sediment for some unknown period of time.

The whelk shell below also suggests considerable age–it’s pock-marked with dozens of bore holes. 

Both species–the cockle and the whelk–are still extant, so there’s no affordable way of telling how old they are.  They might be thousands of years old, but it’s difficult to say for sure because recent sea shells are mixed together with ancient ones at this site.  But they do give an aged appearance.

When I first picked this up, I thought it looked like a dugong or manatee bone that ocean waves had eroded into an oddly-shaped pebble as often happens.  The more I look at it, however, the more it looks like just a pebble.

Even though this isn’t a fossil, it’s the best specimen I found on the beach that day.  It’s a sea pen (Atrina rigida), named after its shape, similar to an old fashioned ink pen.  They’re fragile and usually are found broken, but this one is complete on both sides.  Barnacles grew on one side of this specimen.  According to Euell Gibbons, sea pens make good eating.  They have a muscle that tastes just like a scallop, only better.

Botany Bay

Not far from Edisto State Park is the Botany Bay Wildlife Management Area–a misnomer because it’s actually a hunter’s management area.  Food for game animals is grown here to improve hunting for humans.

Note the corn and wheat fields grown for deer, turkey, and dove.

Humans are allowed to hunt and remove live animals, but aren’t allowed to remove the bones of long dead ones.  I reject this on the grounds of inconsistancy.

Botany Bay is a beautiful area–a maritime forest of live oak, palm, and southern pine interspersed with salt marshes and fronted by the beach.  By far the most common birds I saw were laughing gulls, brown pelicans, and mourning doves.  The live oak acorns support a high population of gray squirrels that were hard to avoid even when going 15 mph on the long dirt road through the WMA.  Here are some photos of pelicans, live oaks, and salt marsh.

Charleston, South Carolina

I found an intersting restaurant in the old town of Charleston called the Hominy Grill.

They serve traditional low country dishes such as shrimp and grits, chicken perloo, country captain, and fried catfish with peanut geechee sauce served over fried grits.

This is fried catfish, fried grits, and peanut geechee sauce.

They also have daily specials that vary.  When I was there the specials included pit roasted lamb po’ boys and grouper cooked in a tomato crab sauce.  For dessert we had a rich home made chocolate ice cream.  It was all delicious.

Later we took a stroll around Charleston Harbor.

This is a picture of salvaged brick from Fort Sumter.  Notice the powder burns and bullet holes from that old Civil War battle.

References:

Gibbons, Euell

Stalking the Blue Eyed Scallop

David McKay Company 1964

Sanders, Albert

Additions to the Pleistocene Mammal Faunas of South Carolina

American Philosophical Society 2002

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Tags: Atrina rigida, Botany Bay, Charleston South Carolina, Edisto Beach, Hominy Grill, lag deposits, Pleistocene Mammals, Sea Pens