Posts Tagged ‘Edisto Beach’

Parallel Unconformities in Florida and South Carolina Fossil Sites

August 9, 2010

Unconformities often puzzle geologists.  An unconformity is a geological term in the study of stratigraphy for a region where sediment from one age overlays sediment from an older age, but fill from the age in between is missing.  For example at the Peace River fossil site located in southwest Florida, late Pleistocene-age fossils are found in sediment over fossiliferous Miocene-age sediment, but rocks and fossils from the Pliocene and early Pleistocene are completely absent.  Geologists are some times at a loss to explain exactly why unconformities occur in certain areas, and of course, creationists jump all over the lack of a definitive answer as proof against an old age earth.  However, they are wrong.  Though scientists don’t know for sure why an unconformity occurs, there are plausible reasons.

Most likely, the Pliocene and early Pleistocene were particularly arid.  The rivers in the region dried up and floods were rare.  Floods wash sediment over bones, thus creating fossils, so without fluvial sedimentation, fossil evidence never was preserved from this intervening age.  This dry climate phase may explain why Georgia’s piedmont is almost barren of Pliocene and Pleistocene fossils, though I’m convinced a concerted search of Georgia’s river basins would discover some of the latter age here.

The fossiliferous strata off the coast of Edisto Beach, South Carolina parallels that of the Peace River fossil site and may be due to the same climate phase.  This site too yields both late Pleistocene fossils mixed with Miocene shark’s teeth, so this unlocated Pleistocene strata must overlay Miocene strata, and the ocean currents are eroding both.  At the Ashley River site, also in South Carolina, the Pleistocene fossils overlay even older Oligocene strata.

In the Peace River the fossils are located in an area of only about 84 square feet in sediment about 6-12 feet underwater.  Scuba divers uncovered the fossils.  Miocene fossils are not only found underneath the Pleistocene ones, but they’re intermixed with them and river currents even work them to modern surfaces.  As river currents wash away ancient sediment, they expose these fossils.  Nevertheless, scientists can use knowledge of chemistry to discern the difference in age between Miocene and Pleistocene fossils.

Scientists analyze the ratio of rare earth elements within the fossils.  Rare earth elements are a family that aren’t particularly rare but consist of few a layman would know.  They include 14 in the lanthanide series and 14 in the actinide series.  All actinides, such as uranium, are radioactive.  Lanthanum, cerium, and erbium are some examples of lanthanides.  Rare earth elements exist in small quantities in ground water, and they occur in consistent ratios with each other.  However, these ratios change over time.  When animals drink water they ingest these elements and absorb them into their bones in the same consistent ratios.  Naturally, Pleistocene fossils have ratios of rare earth elements that occured in Pleistocene ground water, while Miocene fossils have ratios of rare earth elements from Miocene-age water.

The list of Pleistocene fossils found at the Peace River is impressive and includes large, warm climate species.

gar

box turtle,

giant tortoise

river cooter

red bellied turtle

rattlesnake

undetermined duck or goose

cormorant

turkey

pampathere (giant armadillo)

glyptodont

eremotherium (giant ground sloth)

Harlan’s ground sloth

raccoon

Florida spectacled bear

dire wolf

jaguar

bobcat

giant beaver

capybara

tapir

horse

flat-headed peccary

collared peccary

stout-legged llama

long-necked llama

bison (antiquas)

white tail deer

mammoth

mastodon

manatee

Miocene fossils from this site are largely marine–shark’s teeth, ray plate teeth, fish bones, dugong bones, and whale bones.  Notably though, 20 specimens from 5 species of three-toed gazelle horses have been recovered here.  Here’s the list:

Cormohipparion plicatile

Cormohipparion ingenuum

Pseudohipparion skinneri

Calippus elachistus

Nannihippus marganui

Three-toed gazelle horses were a common herbivore of the Miocene.  They had a slender build resembling modern day deer.  During the later Pliocene deer likely began to replace them in the ecological niche they occupied, while surviving horses evolved into the one-toed horses of today.

References:

Hulbert, Richard; Gary Morgan, and Ardreas Kerner

“Collared Peccary (Mammalia, Artiodactyla, Tayassuidae, Pecari) from the late Pleistocene of Florida.”

Museum of Northern Arizona bulletin 65

Whitten, Kenneth; and Kenneth Gailey

General Chemistry with Quantitative Analysis

Saunders College Publishing 1984

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Bob Perkins has shipped me an atlatl.  Future blog entries will include an erratic series entitled “Adventures with an Atlatl.”  I’m also planning on entries about Georgia’s Pleistocene Horses, Pleistocene deer, a study of passenger pigeons, and another erratic series detailing my time travel fantasy of living in Georgia’s Pleistocene before people colonized the region.  This includes what technology I would bring back with me, what kind of house I would build, and what foods would I procure.

The Edisto Beach Fossil Site

May 25, 2010

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