The North Charleston Mastodon

Construction workers digging a foundation for a building in North Charleston, South Carolina 5 years ago uncovered the remains of a mastodon.  Bones including a partial tusk, femur, vertebrae, jaw, ribs, and feet were excavated.  One scientist also examined the surrounding sediment for pollen and plant remains. Apparently, the site was riverbank, and the mastodon likely was covered in flood-borne sediment.  I hope a paper is published detailing the information yielded by this site.  So far, all the information I can find comes from 2 abstracts that described poster presentations of the find at scientific meetings.  The authors didn’t even put the posters on the internet.

One presentation compared the pollen found here to that from other Pleistocene-aged sites located near the present day coast–St. Catherine’s Island, Reid’s and Bell’s Bluff, and a site along the Georgia-Florida border.  All of these sites were farther inland during Ice Ages.  Like these other sites, the North Charleston locality had a strange admixture of species presently found at higher latitudes with those still found in the region.  Water milfoil, an aquatic plant, occurred here.  This is not surprising because mastodons were semi-aquatic.  Hickory pollen was “unusually” abundant, indicating a moist temperate climate, but the pollen of red pine, a northern species, was found in association with sub-tropical Spanish moss.  Other Pleistocene sites in the region yield hemlock, basswood, and walnut–species no longer found this far south.  However, I’m skeptical about the identification of supposed red pine pollen.  This species currently occurs in New England, a region that was under glacial ice for much of the Ice Age when its range was forced south.  I doubt it occurred as far south as South Carolina though because there are no relic populations in the southeast.  Red pine pollen is distinguished from pollen of southern pines on the basis of size.  Pollen grains under 43 micrometers in size are classified as northern species of pine, while those over 43 micrometers are thought to be from southern pines.  Shortleaf pine is a common southern species of pine whose pollen grains overlap in size with red pine pollen grains.  Moreover, under the atmospheric conditions of low CO2 as occurred during Ice Ages, shortleaf pine pollen grains may have been slightly smaller than those of the present day.  In my opinion they look identical as the below photos show.  I believe pollen classified as red pine in the below reference and several other studies is from shortleaf pine which is still widespread in the region.

Shortleaf pine pollen grains average a “maximum” 50-75 micrometers in size.

Photos of northern species of pine pollen grains including red pine (Pinus resinosa), jack pine, and white pine.  Red pine and white pine pollen grains easily overlap in size with shortleaf pine.  Therefore, I’m not convinced of palynologists’ claim that red pine occurred in the southeast during Ice Ages.

Reference:

Rich, Fred

“The North Charleston Mastodon Site–New Insights Drawn from Paleoecological Synthesis”

The Geological Society of America: Southeastern Section–64th annual meeting

 

The Mysterious Nodoroc Site in Winder, Georgia

The geological origin of a mud volcano located in Winder, Georgia is a mystery waiting to be solved.  As far as I know, geologists haven’t ever studied this unexplained watery bog that last erupted circa 1800.  It’s probably similar to mud volcanoes found in Africa and southeast Asia.  About 10 years ago, a mud volcano in Cameroon exploded and killed a whole village by carbon dioxide asphyxiation. The carbon dioxide displaced the oxygen in the atmosphere.  An atmosphere of just 10% carbon dioxide causes people to become comatose; an atmosphere of 30 % CO2 causes people to drop dead immediately.

Winder, Georgia is in Barrow County which is between Athens and Atlanta.  My grandparents used to live there.

Nodoroc is a Creek Indian word meaning gateway to hell.  It’s an odd natural boggy pond that used to release a constant bluish smoke while bubbling.  The Creek Indians built an altar of heavy stones on the edge of the volcano where they executed criminals and then threw the corpses in the bog.  It was their way of sending deserving souls to hell.  They believed the volcano was protected by the wog–a devil dog with red eyes and the head of a bear.  Despite the cultural importance of the site, the Creek Indians sold the pond and the land around it to the English for 14 pounds of beads.  Some early colonist made off with the altar and now it’s lost to archaeologists.

I couldn’t find a photo of Nodoroc on google images that I could confirm was the actual site, but the below link is an aerial photograph.  The brown muddy expanse is labeled and obvious to see.  The link below that is of video of a mud volcano in Yellowstone National Park.  Unlike Nodoroc, it is still active and it probably has a different kind of origin.  The Yellowstone mud volcano is caused by heating and cooling subterranean rock on a fault line, while the Nodoroc mud volcano resulted from decaying organic matter.

http://www.wikimapia.org/#lat=33.973821&lon=-83.6727574&z=19&l=0&m=b

http://www.youtube.com/watch?v=iJ8qfpMkDs0

The first European explorers to visit Nodoroc say that it burned and dissolved everything they threw in it.  Even rainwater evaporated when striking the bog.  They reported that the area attracted lots of animals, but I think the abundance of wildlife resulted from Indians avoiding the place which they only used for executions.

Circa 1800 John Gosset built a cabin nearby and cleared a field around Nodoroc.  One day, Gosset and his wife witnessed the last eruption of the mud volcano.  His wife noticed an unusual amount of fog over the bog that morning.  She called her husband who was busy ploughing to come see it.  A loud explosion was followed by a shower of hot mud particles.  After the eruption the volcano settled several feet and cooled.  Decaying matter likely caused a fermentation reaction, releasing carbon dioxide and methane that had been trapped under the mud.

In the days of free range livestock Nodoroc was known as a cattle mire because cows constantly were  getting stuck in the quicksand-like mud.  Farmers eventually erected a fence to prevent any more losses.  Nodoroc was formerly about 5 acres in extent but circa 1900 John Harris drained part of it and grew several successful crops of corn.  While ploughing, he often came across bones and horns.  They were mostly the bones of recent cattle, but I suspect they may have been mixed in with Pleistocene fossils–a point I will discuss later.

Gary Bolton, a layman, visited the site in 1987 out of curiousity.  He noted that tulip tree saplings had colonized part of the pond, but many fell over, as if the shaky marsh ground couldn’t support deep roots.  Most of Nodoroc was covered with “thousands” of crayfish chimneys.  He mentioned sticking a shovel in the pond and finding that the level of muck was deeper than the shovel itself.

Acidic peat bogs are rare in the piedmont region of southeastern North America.  Peat bogs often contain and preserve pollen, plant macrofossils, animal fossils, and human artifacts.  So far, Nodoroc has only attacted 2 paleobotanists.  Dr. Stephen Jackson and Dr. Donald Whitehead investigated the site in 1981 and published their findings 10 years later.  They took 2 deep piston cores of sediment that they analyzed.  They did find 2 statigraphically datable segments in the core: 1 dated from 26,000 BP-22,00 BP, and the other from 3600 BP to the present.  This study was done before radiocarbon dates were recalibrated.  These dates roughly translate to between 30,000 calender years BP-26,000 calender years BP, and from 4,000 calender years to the present.  The lack of continuous stratigraphy is explained by long periods of time when water level was low and deposition didn’t occur.  The oldest segment dates to the weak interstadial immediately prior to the cold phase that led to the Last Glacial Maximum.

The site itself was probably an open marshy environment during the interstadial.  Plant macrofossils and pollen indicate an abundance of sphagnum peat moss, arrowhead (Sagitteria sp.), sedges, and carnivorous pitcher plants growing directly on the site.  Shrubs such as alder, myrtle, and mountain laurel and/or blueberry (Ericereae genus) grew on the marsh edge.  Pines and oaks dominated the forest surrounding the site.  With the exception of white pine (Pinus strobus) scientists can’t distinguish between species of pine by looking at pollen grains. After looking at the pine pollen and pine needle fossils under a microscope Drs. Jackson and Whitehead were only able to eliminate 3 species–longleaf, slash, and table mountain, none of which would have been expected to be here anyway.  However, the size of the pollen grains suggests both northern and southern species of pines were present.  Northern species of pine tend to have smaller pollen grains, while southern species of pine tend to have larger grains.  Both large and small grains were present.  My educated guess is that jack pine (Pinus banksiana) and shortleaf pine (Pinus echinata) were the dominant pinus species, while white pine was also present.  Macrofossils of jack pine, a species that now no longer occurs farther south than Michigan, have been found in Missouri and north Georgia sites dating to the mid-Wisconsinian interstadial.  Apparently, it was a more widespread species then than it is today.  Shortleaf pine, a southern species, occurs as far north as southern Ohio, and its short needles can endure snowy and icy conditions without much damage.  There’s no way of determining which species of oaks predominated here–all oak pollen looks too similar.

Other important trees growing in this interstadial forest were Critchfield’s spruce (my species assumption), fir, and hickory.  Chestnut, beech, sugar maple, and birch were present but at low levels.  (After the Ice Age chestnut became much more abundant in the region until its unfortunate extirpation 100 years ago.)  Hazelnut was a common bush growing in the understory.  During the Wisconsinian Ice Age hazelnut ranged throughout the south but is practically absent here today.  Noticeably absent or rare then were sweetgum, tupelo, and red maple all of which are common today in this area.

Fir trees thrive in regions with snowy winters.  As I mentioned in last week’s blog entry, the piedmont region of southeastern North America during the Ice Age was an abrupt transition zone between subtropical Gulf Coast Corridor grasslands and boreal forests of the Southern Appalachians.  Humid tropical fronts often hit cold air causing lots of snowfall.  Critchfield’s spruce, firs, and short-needled pines were and are well adapted to the snowy conditions that may have once blanketed the south.  It would have been interesting to see this environment where warm climate fauna frequently wandered to mix with creatures from the cold north.

I’m surprised no Pleistocene fossils habe been discovered or noticed from Nodoroc.  If cows often perished in the mire, I’m sure some of the Pleistocene megafauna did as well.  Perhaps the Indian legend of the wog is based on skeletel material of extinct beasts they discovered.  If I owned the pond I’d have it dragged for fossils and artifacts.

Artist’s rendition of the wog, a creature of Creek Indian legend that supposedly guarded Nodoroc.  Was the legend based on Pleistocene-aged fossils Indians found in the bog?  Cows used to get stuck in the mire and perish.  Pleistocene megafauna must have also.  This site should be prospected for Pleistocene vertebrate fossils which are probably mixed with modern livestock bones.

References:

Bartow County Historical Society

The History of Nodoroc and Tales of the Wog

Jackson, Stephen; and Donald Whitehead

“Pollen and Macrofossils from Wisconsinian Interstadial Sediments in Northeastern Georgia”

Quaternary Research 39 1993

Wilson, Gustavius

The early history of Jackson County, Georgia

W.E. White 1914

Pleistocene Soil Cycles

In his book The Natural Environments of Georgia Dr. Charles Wharton suggests Ice Age coniferous forests consisting of boreal species built many of the soils in the mountains and piedmont of Georgia.  This is fodder for contemplation of Georgia’s ecology.  Pleistocene soil composition must have gone through cycles that paralleled the climate cycles of stadial to interstadial and glacial to interglacial.  Soils became thin during stadials but were enrichened during interstadials and interglacials.  I am aware of no studies investigating the origins of topsoils in Georgia, and this kind of study is not even possible now because almost all of Georgia’s original topsoil has eroded or blown away, thanks to poor agricultural practices.  Nevertheless, speculation on the ecology of the Pleistocene soil cycle is another fruitful topic for this blog.

Fossil evidence from Bob Black Pond in Bartow County shows that a forest composed of jack pine, red pine, white pine, white spruce, Critchfield’s spruce, and paper birch grew in north Georgia during the Last Glacial Maximum ~21,000 BP.  This probably represents a common dominant forest in north Georgia during climate phases of the Ice Age known as stadials–times of arid cold when the Laurentide Glacier expanded to the north and locked up much of the planet’s atmospheric moisture.  To contemplate a full cycle of Pleistocene soil development, let’s go back farther in time to about 30,000 BP.

30,000 years ago, an interstadial that had lasted for about 4,000 years was coming to an end.  Interstadials were warmer, wetter climate phases within Ice Ages.  Studies of the pollen record show oak pollen always increased during interstadials, while pollen from coniferous trees decreased.  The leaves and debris from oaks and other hardwoods build up a healthy, thick topsoil, usually taking about 100-200 years to do so.  After 4,000 years most of the topsoil in the region must have been particularly rich.

Ice Age climate fluctuated rapidly.  Imagine now, that an ice dam on the St. Lawrence River melted enough during the warming trend of the previous 4,000 years to collapse, sending a torrent of freshwater and ice bergs into the North Atlantic.  This flood of cold freshwater shut down the thermohaline current that had kept the climate warm for millennia.  Climate changed immediately to colder, more arid, and windier conditions.  CO2 levels plummeted as well.  After a few decades many of the oaks and other broadleaf trees that had spread to upland habitats began to die from drought and wind and lower CO2 levels.  Grasses and coniferous trees compete better than hardwoods under these conditions.  Plants need CO2 for respiration.  During stadials CO2 levels fell so low that even some coniferous trees became starved for CO2.  Fossil juniper from the La Brea tarpits, for example, show evidence of CO2 starvation.  Under these conditions broadleaf trees only persist near rivers and streams.  Grasslands and brush thrive in the shade free environment, but the burgeoning bison, horse, and mammoth populations overgrazed the vegetation, leaving bare soil which blows away in the wind and much of the topsoil is thinned or lost.

Jack pine forest in Michigan. The landscape much resembles that of an open pine savannah in the coastal plain of Georgia.  Like an open pine savannah, jack pine forests are fire dependent.  Jack pine grew in the mountains and the piedmont of Georgia during stadials, the coldest stages of the Ice Age, but is completely absent from the state today.  The hilly terrain likely made for a more varied environment though in Georgia than this photo indicates.

Today, Eastern jack pine (Pinus banksiana) grows no farther south than northern Michigan and is a common tree on sandy outwashes in Ontario, Canada.  It’s a pioneer species, able to grow on thin sandy soils.  During the driest coldest phase of stadials, jack pine colonized dry upland sites in Georgia where many oaks could no longer dominate.  Jack pine forests are rich environments.  They grow thinly allowing light to hit the forest floor.  This promotes the growth of grasses and berry bushes.  Kirtland’s warblers, upland sandpipers, bluebirds, cowbirds, deer, bear, snowshoe hare, and rare prairie plants such as Allegheny plum, rough fescue, and Hill’s thistle all thrive in jack pine forests.  In Pleistocene Georgia many of these same species with the addition of extinct grass-eating mammals  were probably also abundant.  The rare Kirtland’s warbler (now summering in only a few counties in Michigan) winters in the Bahamas which were expanded in size due to lowered sea levels during the Ice Age.  (https://markgelbart.wordpress.com/2011/11/11/banana-hole-fossil-sites/) I suspect this bird was more widepread then and may have occurred in Georgia because it is dependent on jack pine forests.  Perhaps not coincidentally, fossils of upland sandpipers have been excavated from Bartow County where the jack pine fossils were found.

Fires were rare during stadials because lightning storms were rare.  Jack pines require fire for regeneration.  Other species of pine less dependent on fire such as red pine (Pinus resinosa) and white pine (Pinus stroba) encroached into jack pine forests in the absence of fire.  Post oaks which are among the most fire resistant and drought resistant oaks also move into these pioneer forests.  Gradually, the needles and debris from Ice Age coniferous forests added humus and thickened he topsoil.  When the next interstadial began (~15,000 BP) the climate warmed, precipitation increased, CO2 levels increased, and oaks and other broadleafed trees expanded from their refuges along waterways and once again colonized their old territory.  Jack pine is the most shade intolerant boreal species and was the first to be completely replaced, retreating to the north where it was able to take advantage of newly deglaciated sandy soils.  Next, red pine retreated, mostly toward New England, though relic populations remain in West Virginia.  Of the boreal species of pine, white pine was the least shade intolerant, so it still persists in north Georgia, though it’s much less common than it was during the Ice Age.

Young mixed boreal and hardwood forest.  At the beginning of interstadials when climate became wetter and warmer, oaks and other hardwoods rapidly displaced boreal conifers in the Georgia mountains and piedmont, shading the pines out.  These climate phases probably fostered the greatest variety of wildlife because northern species of plants and animals would still be present but southern species would begin colonizing the new habitat.

The greatest diversity of wildlife likely occurred during transitions from stadial to interstadial and vice-versa.  Environments in transition harbored a greater variety of habitats that animals and plants of northern and southern affinities would have found favorable.  A study of forest succession in the Georgia piedmont found that bird species abundance peaked at the stage when oaks began replacing pines.

There’s no evidence that northern species of pines ever extended their range into south Georgia.  Central Georgia was probably a transition zone where northern species of pines mixed with southern species of pine in environments that have no modern analog.  Shortleaf pine, the southern pine best adapted to cooler weather, was probably the most common pine species, though some northern pines ranged into the piedmont.  But much of south Georgia became brush, grassy deserts during stadials and much of the topsoil there blew away.  Eolian sand dunes rolled across the landscape, and the wind scooped out depressions and created Carolina Bays–a subject for a future blog entry.