Alluvial and Colluvial Geology of Pleistocene Georgia

Rivers and streams built all of Georgia’s coastal plain or about 1/3rd of the state.  All of Georgia’s coastal plain was under ocean water during most of the Eocene (55 million BP-33 million BP), and then periodically it was at least partially inundated with seawater transgressions until as recently as 5 million years ago.  Rivers deposited sediment from eroded rock originating in the piedmont and mountains, and gradually this fill became high and dry land.  This explains why so much sand occurs on the coastal plain.

During the Pleistocene Georgia’s rivers went through several cyclical phases that correlated with climate fluctuations.  

 

Diagram of changing river patterns over the last 28,000 years.  Earlier interstadials probably had some braiding rivers and some meandering rivers.

From ~28,000 BP-~15,000 BP cold arid climate caused reduced stream flow.  Lowered water tables made many small streams vanish.  Major rivers consisted of a braided pattern, and they were clogged with many sandbars and islands.  Other rivers became like a chain of isolated springs where the water table met the surface of the land.

From ~15,000 BP-~12,ooo BP sudden warming climatic trends caused massive storms and a dramatic increase in precipitation.  These super storms were of 2 types: violent tropical storms and storms caused when strong cold fronts originating from retreating glaciers clashed with warm fronts.  The frequent storms created super meanders in rivers and caused the river bends to shift wildly, resulting in lots of scroll bars.  Distinct wet and dry seasons also contributed to scroll bar formation.

From ~12,000 BP-~~5,000 BP increasing precipitation in the atmosphere caused by glacial meltwater pulses caused rivers to meander more than they do today.

From ~5,000 BP- the present modern river meandering patterns prevailed.

Colluvial environments resemble alluvial landscapes but have a different origin. Colluvial environments are shaped by rainwater eroding soil from slopes rather than from river sedimentation.  However, in some cases, rivers eroded slopes that later led to colluvial soil fill.  As I noted in the above description, during certain climatic phases of heavy precipitation and increased storm activity, rivers meandered more than they do today.  These supermeandering rivers and streams eroded slopes.  Later, when rivers returned to their present beds, rain washed soil from the slope to the flat below. 

Diagram of colluvial environments.

Colluvial flats can also exist where rainwater washes soil from rocky hills–the area adjacent to Stone Moutain in Dekalb County is an example of this.

The most common type of colluvial flat occurs along small streams and springs that at one time had a much larger flow.  Deep gulleys and steep terrain characterize colluvial lands.  Little Kettle Creek, which I visited last year, may be an example of a stream that once had a higher stream flow.  The gulley where this small shallow creek runs is at least 12 feet high in the place I visited, and on topographical maps, the gulley looks much higher than that in other places.  When it accumulated mammoth, mastodon, bison, and deer fossils, it must have been a much deeper stream with a higher flow.

View of Little Kettle Creek from the top of a bridge.  The gulley here is much deeper than the water flow.  I hypothesize Little Kettle Creek used to have a much greater flow of water.  The megafauna fossils found here must have been deposited from either alluvial or colluvial processes.

Dr. Charles Wharton listed several examples of colluvial lands–Anneewakee Creek in Douglas County, Bay Springs Creek in Carroll County, Chattahoochee State Park in Fulton County, and the southeast and northeast faces of Stone Mountain in Dekalb County.  Common trees growing on colluvial flats include beech, tulip, magnolia, white oak, mulberry, loblolly and shortleaf pine.  At Stone Mountain, mountain laurel grows in the understory.  Paw paw (See my blog entry–“Favored Fruit of the mastodons” https://markgelbart.wordpress.com/2010/10/01/the-paw-paw-a-favored-fruit-of-the-mastodon/ BTW, the offer still stands–a free copy of my book in exchange for paw paw seeds or fruit)  is common (or was when Dr. Wharton checked it out 30 years ago) in the understory at Chattahoochee State Park.  Paw paw does grow best on rich soils that are found on colluvial flats.

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.

The Vero Beach Mammoth Engraving

About 5 years ago James Kennedy, an amateur fossil collector, found a nondescript scrap of bone near Vero Beach, Florida.  It seemed so ordinary he went home and promptly stuck it in a box under his sink.  But a few months later he took it out of the box, cleaned it,  and discovered it was not nondescript at all–there was an engraving of a mammoth on it.  Paleolithic art on portable objects such as bone, antler, and rock are common in Europe but before this discovery unknown in North America.

Up close view of the mammoth engraving.  The domed forehead indicates it depicts a mammoth, not a mastodon.  The fossil is mineralized and has no DNA left for species identification. The whole scrap of bone is just 16 inches long.  The engraving itself is about 4 inches wide. 

This fossil is an incredible and rare find from a site that has produced a bounty of other wonderful fossils and artifacts, including human remains probably dating to about 14,000 calender years BP.  Of course the first thought to cross the minds of scientists when they initially saw the specimen was the possibility that it might be fake.  But there are several ingenius scientific techniques that can detect whether the artifact is a fraud or not.  By analyzing the ratio of rare earth elements found in the specimen (a method I’ve discussed on a couple of previous blog entries including https://markgelbart.wordpress.com/2011/08/28/the-fossil-rich-region-of-tunica-hills-louisiana/) they determined the fossil dates to the Pleistocene and did come from the Vero Beach site.  After examination of the specimen under a microscope, scientists concluded the engraving showed the same amount of weathering as the rest of the bone.  A fresh engraving would look much clearer than the rest of the bone.  Scientists made a fresh incision on this bone, then used a scanning electron microscope to compare the fresh cuts with the older engraved cuts.  The fresh cuts had a “debris field” (microscopic dust) whereas the engraved one didn’t, suggesting an older debris field eroded away.  Also, it looks as if the mineralization of the bone occurred across the engraving.  Scientists conducted 2 additional tests to determine if the engraving was authentic.  Energy dispersion x-ray spectroscopy can detect whether the specimen was cut, then applied with a substance that made it look mineralized.  No substance they could detect was used.  Finally, they made a cast and mold of the fossil and subjected it to reflection transformation imagery (http://vcg.isti.cnr.it/Publications/2006/DCCS06/).  This helped them determine the engraving wasn’t made recently.

James Kennedy with what looks like a bunch of fossils.

I’m convinced it’s authentic.  From examining Mr. Kennedy’s dwelling (his home?) in the above photograph, he appears to be a working class kind of guy and unlikely to be harboring a method that can fool modern forensic scientific techniques.

According to a Mammoth Trumpet article, the Vero Beach mammoth engraving is being auctioned.  If a museum doesn’t place the highest bid, this specimen could be lost to science.

The whole scrap of bone with the engraving on it.  Geometric designs extended past the broken end. The size of the bone narrows it down to either mammoth, mastodon, or giant sloth.  Not enough is left for scientists to determine which it was.  But without a doubt the engraving depicts a mammoth.  Mammoths had  domed forehead, mastodons didn’t.  If I had to make a bet, I’d gamble the bone is from a mammoth because it’s likely the paleo-indian who engraved it was drawing the animal it was from.

Vero Man was NOT a 12 Foot Tall Giant

While researching the topic of this blog entry, I came across a creationist blogger who claimed the scientists who originally examined the fossils from the Vero Beach excavation found bones of 12 foot tall men.  Supposedly, this supported the existence of giants as recorded in biblical accounts.  I knew this was bullshit, but the creationist had a source–a newspaper article written in 1930.  I assumed the newspaper reporter was probably a sensationalist idiot, incapable of distinguishing his ass from a hole in the ground. I was certain the reporter had never even read the original scientific paper and had gotten his facts confused.  I’ve read hundreds of scientific papers on paleontological discoveries, and scientists always give exact measurements of every single body part when they find something new and different.  So I searched and found the article written by E.H. Sellards in 1916, and much to my delight, it was available for free online.

It’s an excellent paper, quite advanced for its time–realize that in 1915 when workers were digging  the drainage canal that led to the abundant  fossil discoveries here, north Florida was a wilderness with a few subsistence farmers, cotton plantations, and lumber operations.  The canal construction bisected an extinct river bed that formerly flowed into the Indian River lagoon.  The extinct river was about 100 yards across but was shallow.  I suspect it was a kind of brackish stream.  Workers kept finding cartloads of Pleistocene-age fossils, attracting the attention of E. H. Sellards, a geologist, and O. Hays, a vertebrate zoologist.  Dr. Sellards told the workers to look for human remains, though he didn’t expect them to find any because at the time conventional wisdom assumed that Pleistocene mammal extinctions in North America occurred before man’s arrival on the continent.  Much to his surprise, workers and fossil collectors did find human remains in 3 different places along the canal, and human artifacts in 2 additional spots–all associated in the same strata with bones of Pleistocene-age mammals.  This was the first evidence ever that humans co-existed with extinct Pleistocene mammals in North America.  In total they found the remains of at least 5 individual people.

The human specimens from the first locality included leg, heel, feet, and finger bones.  They were found associated with fossils of mammoths, mastodons, horses, deer, and Jefferson’s ground sloth.  The mammal fossils had the same degree of mineralization as the human fossils.

The human specimens from the second locality consisted of ankle, pubic, and finger bones and were found with 7 flint tools.  I’m no expert on lithics, but from the pictures in Dr. Sellards’ paper, they look like scrapers used to scrape fur from hides.  These specimens and artifacts were found associated with fossils of mammoth, horse, tapir, possum, rabbit, cotton rat, armadillo, shrew, alligator, snakes, and acorns.  Lots of good plant fossils were initially discovered, but after exposure to air overnight, all but the acorns, turned to dust.  Dr. Sellards could have used the benefit of modern techniques to prevent this.

The human specimens from the third locality included arm, shoulder, jaw, foot, tooth, toe, and skull bones along with broken pottery, bone implements, and flint arrowheads.

Dr. Sellards also found mammoth and bird bones with human-made engravings.  These were found associated with fossils of horse, saber-tooth, deer, tapir, horse, rabbit, round-tailed muskrat, raccoon, alligator, snake, fish, amphibian, bird, acorns, and wood.

Dr. Sellards wrote “Undisturbed strata over human bones precluded the possiblity of human grave burial intruding into the sediment.”  He even found a heavy rock over some of the human bones.  Moreover, if these were more recent purposeful graves, more of the skeletons would have been found rather than just disarticulated pieces.  Despite Dr. Sellards’ sound reasoning, Ales Hrudlicka, the leading American anthropologist then, insisted these bones were from later Indian burials intruding into the older fossil deposit.  This controversy occurred before the invention of carbon dating which would have settled the issue.  Dr. Hrudlicka refused to believe Indians co-existed with now extinct Pleistocene mammals, even after discovery of Clovis arrowheads in mammoth bones in 1932.  Comically, he once gave a lecture denying this possibility, immediately following presentation of the famous Clovis evidence at a symposium. Some people are just so close-minded, they can’t accept evidence, even after it slaps them upside the head.  Which brings me back to the creationist.

In Dr. Sellards paper he only gives measurements for 1 of the human specimens.  He measured “the lower margin of the lesser tuberosity to the upper margin of the inner condylur on the femur.”  It was 29 cm.  On an average modern human that part of the leg is 32 cm.  So if anything, that particular Indian was smaller than average–not a 12 foot giant as the full-of-shit journalist reported in his article in 1930.  The creationist blogger should have taken the effort to do some critical thinking and deeper research before he regurgitated phony bullshit.

For a century now this drainage canal in Vero Beach has been a productive site for amateur fossil collectors.  In addition to species mentioned above, they’ve found fossils of dire wolves, jaguars, bobcats, llamas, bison, pampatheres (a 300 pound armadillo), and Eremotherium–a really giant ground sloth.  But this will soon be coming to an end.  The city of Vero Beach is planning to cover the canal in concrete and turn it into a sewage outlet, though they are giving scientists extra time to do some last minute collecting before they close this door to the past.

Incidentally, all the human remains from the Vero Beach fossil site were lost.  After their discovery the specimens were shuttled back and forth between the Smithsonian Insitution and Florida State, but by 1947 interested parties lost all track of them.  What a shame.

References:

Lepper, Bradley

“Mammoth Engraved on Bone from Florida”

Mammoth Trumpet (27) 1 January 2012

Sellards, E.H.

“Human Remains and Associated Fauna from the Pleistocene of Florida”

Florida State Geological Survey 1916

It’s Ice Cream for Deer but Poison for Humans

One of the dumbest examples of wilderness survival folklore ever espoused is the notion that to determine whether a potentially edible plant is poisonous or not, a person should observe an animal consuming the plant.  The logical fallacy is the assumption that if the animal could eat the plant and not die, than it would be safe for humans to eat.  This is a stupid assumption for 2 reasons:  First, the animal could crawl off in the bushes and die later out of sight.  Second, and more importantly, all animals have completely different physiologies than humans.  There are many plants highly poisonous to humans but perfectly edible to many species of mammals, birds, and especially insects, such as caterpillars which consume poisonous plants that make them inedible to birds when the caterpillars become butterflies.  Below are 2 species of common plants found in Georgia that are favorite foods of deer but are poisonous to humans.

Strawberry bush–Euonymous americanus.  Naturalist refer to the plant as “ice cream” for deer.  But it is poisonous to humans.  It’s in the bittersweet family.

Buffalo nut–Pyrularia pubera.  Also a favored deer edible that is poisonous to humans.  It’s in the sandalwood family.

Deer eat strawberry bush twigs, and birds eat the fruits, but both parts are deadly to humans, causing vomiting, diarrhea, irregular hearbeats, convulsions, coma, and death.   Scientists don’t know what type of poison it is.  Strawberry bush is also poisonous to livestock.  It was advantageous for deer to evolve the ability to digest a plant that was likely poisonous to competing herbivores of the Pleistocene, such as bison and horses.  I wonder if other browsing Pleistocene herbivores (mastodons, tapirs, Jefferson’s ground sloths) could also eat strawberry bush without ill effect.  Browsers tend to be more resistant to plant poisons because they eat small amounts of a great variety of foods and don’t concentrate the poison in their systems.  Grazers eat large quantities of fewer species of plants, making it more difficult to evolve the ability to eat toxic vegetation.  Deer probably evolved the capacity to survive eating toxic plants because they only nibbled on the plant, and individuals that could survive eating small quantities passed this characteristic on to the next generation, unlike bison which ate such large quantities that no individuals survived consuming the toxins.   Gradually, each generation of deer had a growing inherited capacity to digest this toxic plant with no ill effects.

Buffalo nut is toxic to humans, rabbits, and pigs, but not deer, cattle, horses, sheep, and mice.  Its poison is an amino acid similar to that found in cobra poison.  The protein stimulates growth hormone in deer and may facilitate antler growth. In addition to harboring plant toxins, buffalo nut is a parasite, living on nutrients from other tree’s roots.  The roots of a buffalo nut “kiss” the roots of other species forming a hausteum, an attachment that helps them leech nutrients absorbed by the other tree. Many species of trees serve as host species for buffalo nut, including oak, chestnut, and hemlock.

Both strawberry bush and buffalo nut grow as understory trees in disturbed moist woodlands–a habitat that expanded during interstadials and interglacials but decreased during stadials.  Grazers always became more abundant during stadials when arid cool climates fostered the growth of grasslands but decreased the abundance of toxic woodland plants.  Browsers increased when forests expanded.  Strawberry bush and buffalo nut are known as “gap phase” species, thriving in areas of the forest disturbed by fire, storm, or human activity.

Like most plants, strawberry bush and buffalo nut are invisible in the Pleistocene fossil record, but they must have been present then or they wouldn’t be here today.

Speaking of (or rather writing of) ice cream for deer, I tried growing fava beans in my garden 2 years ago.  Fava beans are a cold hardy legume.  I read they could survive temperatures as low as 15 degrees F.  Because winters in Augusta, Georgia seldom get that cold, I predicted they would do well.  I had a great stand of fava beans in my backyard by early December.  One afternoon while taking a walk in broad daylight, I saw a deer.  It stopped about 20 yards from where I stood.  It seemed unafraid and even stomped its hooves as if attempting to intimidate me.  I resumed walking up the street until I heard hooves hitting pavement behind me.  I realized it was heading straight for my fava bean patch.  I raced back to scare it away but 2 big dogs came out of nowhere and chased the fleeing deer from my garden for me.  My fava beans were safe but nor for long–a few days later the temperature dropped below 15 degrees, an unfortunate stroke of luck because temps here get that cold maybe once every 10 years.  The favas did sprout back from the roots but production was meager compared to what would have been from the lush first growth.

Freshwater mussels of Georgia

I used to think clams were boring, but that was before I learned about their reproductive life cycle.  I formerly thought of bivalves as inactive organisms that live on aquatic bottoms like a dead stick in the mud.  It’s true most species of freshwater mussels are sedentary life forms, filter-feeding on the microscopic algae and bacteria that are carried their way by currents.  The males and females are even incapable of approaching each other to mate.  Instead, the male ejects sperm into the water and the female takes it in while filter feeding, thus fertilizing her eggs.  Amazingly, the female tricks more advanced creatures into helping spread her larva.  Some species of mussels have a fleshy protuberance that resembles a worm or small minnow.  When a fish strikes at the bait, the female mussel squirts her larva onto the fish’s gills.  Eventually, the larva develop into little mussels and drop to the bottom of a river or lake and burrow into the mud where they’ll probably live for the rest of their lives.  Other species of mussels release bags that resemble myriads of tiny aquatic insects.  A fish striking the bag releases hundreds of larva which attach themselves to the fish’s gills.  Biology majors seeking a subject for a master’s thesis take note–little is known about which mussel species parasitize which fish species, so the field of study is wide open.

Life cycle of a freshwater mussel.

Elliptio complanata–Eastern elliptio.  This widespread freshwater mussel occurs in almost every river system in Georgia.  It’s quite edible.  I’ve never eaten one, but I picked up a dead one not long ago and the inside looked and smelled just like an oyster.  It left a carrion-like odor on my hand, however, indicating it had gone rotten.

The Altamaha Spinymussel–Elliptio spinosa.  This endangered species only inhabits the Altamaha River.

Top: Anodonta grandis–Giant Floater…Bottom: Villosa dumbelis–Eastern Creekshell

Rayed Pink Fatmucket–Lampsilis splendida

Anodonta imbecilis–Paper pondshell

A great variety of mussel species live in Georgia’s waters–the exact number is probably unknown.  There’s an estimated >126 species from at least 16 genera, though many are in danger or have succombed to extinction.  Mussels live a long time–up to 100 years.  Nevertheless, many species are endangered.  Dams, sedimentation, pollution, and the introduction of invasive Asiatic clams and zebra mussels have all reduced the amount of available habitat.  Before Europeans colonized North America mussels were an abundant food source for the Indians.  Georgia’ s rivers used to be crystal clear for most of the year, except during summer when Indians burned the woods, and they became black with ash (a practice they engaged in every year).  Today, Georgia’s rivers are clogged with agriculturally eroded mud.  This is not good for filter-feeders.

Surprisingly, I found no information about Pleistocene-aged freshwater mussels in Georgia on the web.  Mussel shells are as durable as bone and should be present in alluvial fossil sites.  I suspect they’ve been ignored or unnoted because scientists don’t know whether specimens associated with alluvial fossil bones are from the present or the Pleistocene.  Leisey Shell Pit in Florida is a famous fossil site noted for bivalve shells, but these are sea shells, dating to when the site was under ocean water.  Nevertheless, freshwater mussels were certainly abundant in Pleistocene freshwater environments throughout the south.  Most were probably the same species that today are heading for extinction.

My Dream Nature Property (Part 1)

I’m starting a new irregular series on this blog–my dream nature property.  My fantasy of living in Georgia 36,000 BP is not really possible.  Instead, I’ll be wishing and dreaming about properties in rural Georgia that I hope to one day purchase.  I’ll stick a trailer or cabin on the land and live out my days there.  So this fantasy has a possibility of coming true.

The first property I’d like to salivate over as a naturalist is this little gem on a Broad River Bluff.

http://www.landflip.com/land.asp?listing_id=7417

It’s 154 acres of mostly wooded land in the middle of nowhere.  I drove through this area of Wilkes County last spring and summer.  I only stepped out of my car for brief periods of time but saw deer and turkey instantly.  This property is only a few miles upstream from the spectacular Anthony Shoals.   I can imagine a nice canoe or kayak trip back and forth to the shoals. Most of this part of Wilkes County is abandoned farmland that has grown up into second growth forest or overgrown fields.  It’s very quiet and there is little traffic, unlike some of our crowded National Parks and National Forests.

View of the Broad River from this beautiful property.

The property itself is said to consist of a mixture of hardwoods and pines.  A satellite view shows the wooded property is surrounded by hayfields and cow pastures.  This isn’t necessarily a bad thing–open spaces attract grassland and forest edge species.  Hayfields and cow pastures are a lot better than suburbs anyway.  Because of the river, I’d be sure to see a great variety of aquatic animals and birds.  The bluff forest may hold some rare types of plants as well.  It appears the owners use the land for hunting and fishing.  I’d most likely use it for birdwatching, nature walking, and fishing, though, who knows, I might take up hunting as well.

A duck pond on the property.

A nice picnic area for  private beer parties and outdoor grilling or just quiet solitude.  Note the large leaning trees.

The property is selling for $369,668.  I’m going to have to get real lucky on the stock market to be able to afford something like this.  There’s no house on the property, so if I decide to live here, I’d have to pay for that as well.  When considering buying rural land, it’s best to realize how much property taxes will be.  A buyer should understand that not only do they need to come up with the money or credit to purchase the land, but they need to have a lot of money socked away to pay property taxes every year.

I think government should give tax breaks to people who allow their properties to remain natural, especially if they harbor rare environments.  Much of Georgia’s remaining rural land is destined to be ruined by monocultured tree farms and row crops, so the owners can afford to pay property taxes.  They may be more inclined to let it remain wild, if they don’t have to pay property taxes on it.

New Study of Burmese Pythons in South Florida is Ripe for Debunking

The National Academy of Science often publishes some really bad studies.  One example was a paper that proclaimed Ice Age mammal extinction, the Younger Dryas cold phase, and Carolina Bays were all caused by a comet colliding with the Laurentide Glacier 12,900 years ago.  This illogical paper has since been thoroughly debunked.  Another study ripe for debunking is one that made headline news last week. http://www.pnas.org/content/early/2012/01/23/1115226109.full.pdf+html

Scientists claim the populations of medium-sized mammals in Everglades National Park has been reduced by up to 100% since the accidental introduction of Burmese pythons.  I suspect this is alarmist bullshit.  Reptiles have very slow metabolisms and do not eat as much as carnivorous mammals.  Moreover, if an introduced predator reduced its food supply, it in turn would suffer a population decline, because they would have nothing left to eat.  The number of Burmese pythons captured has steadily increased (with the exception of the 2010 when there was a snake-killing hard freeze), suggesting the species is increasing in number.  This increase in python population couldn’t happen, if they were wiping out their prey base.

The method they used to count deer, raccoon, possums, rabbits, bobcats, and foxes is highly questionable and somewhat bizarre.  Scientists drove at night 331 times over an 8 year period in cars with 1-4 people in them, and counted live and road-killed animals within Everglades National Park.  Supposedly, they did the same thing during the 1990’s before Burmese pythons colonized the park, though as far as I know this data wasn’t published then, and they could be pulling numbers out of their ass.

The results confirm (in my opinion) that this study is full of shit.  From 2003-2011 these scientists only counted 9 raccoons and 5 possums.  9 raccoons and 5 possums in 8 years?  No way. No way!  That is 1 raccoon and less than 1 possum per year.  (Why didn’t they count armadilloes?– Another common small mammal in south Florida.)  These results are just not credible.  To get a good estimate of small mammal populations, the scientists should have used live traps which I guarantee would catch raccoons and possums with a high frequency.  I’m certain these animals are still abundant in the park.  In fact a recent series on the Discovery channel featuring a nature park adjacent to the Everglades that is run by the Seminole Indians showed the Indians frequently capturing problem or injured raccoons and bobcats.

The scientists admit they have no direct evidence that snakes are behind the so-called decline in the population of medium-sized mammals in the park, but point to anecdotal evidence.  If all they have is anecdotal evidence, they’ve got nothing.

The introduction of Burmese pythons has been a wonderful addition to an ecosystem that was in desperate need of more large predators.  I have no doubt that the population of medium-sized mammals has been reduced, but there is no way they’ve decreased as much as this ridiculous study claims.  The introduction of Burmese pythons has been highly beneficial for box turtles and birds whose eggs were vulnerable to the overpopulation of raccoons and possums.

By the way, the Everglades is overrated.  The most beautiful and productive ecosystem in Florida was destroyed by Walt Disney.  The creator of Bambi killed more wildlife than a millenia of hunters.  William Bartram and other explorers all agreed that the region now ruined by Disney World and Orlando was the most beautiful wild place they’d ever seen, and this was in the 18th century when just about every place on the continent was wild.

Sagponds Contain a Partial Pollen Record of Ice Age Vegetation in Northwest Georgia

In the southern Appalachian mountains when groundwater dissolves underlying limestone the ground slumps to a granite bottom, creating an interesting environment known as a sagpond.  These differ from sagponds located in California which are formed from strike-slip faults.  Georgia sagponds form from the same geological principle that creates limesink lakes in Florida.  Dr. Charles Wharton counted as many as 96 sagponds per square mile in Bartow County.  They range in size from a few feet across to several acres.  Some go seasonally dry; others retain water year round.  Scientists recognize 4 types of sagponds.  Dry sagponds drain within an hour after rain stops.  Young sagponds, where the ground hasn’t finished slumping, hold water during winter and spring.  Mature sagponds are partially filled with colluvial silt and retain water year round.  Extinct sagponds have been completely filled with silt but still might be moist enough to support a marsh.

Topographical map of Green Pond.  Sagponds often form on mountains and provide wetland habitats in otherwise dry upland environments.

These low wet areas dotting the otherwise dry upland ridge and valley region host disjunct populations of at least 49 species of plants that are normally found on the coastal plain, including the evergreen laurel oak, gallberry (a type of holly), fetterbush, rock rose,  joint grass, panic grass, beaked rush, and many others.  Common aquatic plants found in sagponds are tupelo, buttonbush, red maple, and sedges.  Buttonbush and tupelo tend to grow in the middle of a sagpond; grass and sedge grow on the edges; than there is a heath zone ringed by a lowland woods consisting of loblolly pine, laurel oak, and red maple.

Page from the book Natural Environments of Georgia with a photo of a dry sagpond in Bartow County.

Photo by Alan Cressler of a sagpond on Keel Mountain in Madison County, Alabama.  I couldn’t find any photos on the web of sagponds in Georgia, though there are supposed to be a lot of them.

Dr. Wharton reports that Bloody Pond in Chickamauga Battlefield Park has a large stand of willow oaks.  (While researching this topic, I discovered that there are at least 2 other Civil War era battlefields with areas known as “Bloody Pond.”)

Scientists looking for ancient pollen and Pleistocene-aged plant macrofossils have excavated and cored several sagponds–Bob Black Pond, Quicksand Pond, Green Pond, Pigeon Mountain Marsh, and Lookout Mountain Marsh.  The pollen record from all these sites combined cover a timespan of between ~34,000 Bp-~10,000 BP in calender years.  Some of the studies date to before scientists realized carbon-dating gave dates too young when compared to tree rings.  The data I give in this discussion mention dates I’ve adjusted.  They’re just rough estimates based on the inaccurate dates from the early studies.

Pollen from Green Pond, believed to date to the Farmdalian Interstadial, suggests an environment in northwest Georgia consisting of dry oak and hickory woodlands with prairie openings.  Dr. W. A. Watts (of Penn State but now retired) conducted this study in 1973 and gave carbon dates of 29,630 BP- 25,000 BP which should be adjusted to about 34 ka BP-30 ka BP.  Pine pollen was scarce.  ~28,000 years ago pine and spruce pollen began to increase, indicating an abrupt change to a cooler drier climate.  Surprisingly, pond cypress was locally present.  This shows that individual plant species ranges didn’t always change in predictable patterns.  Pond cypress is absent in this region today, despite a warmer climate.  Shortly after this date, the pond filled with sediment and the pollen record ends for this site.  Conveniently, this is when the pollen record from sediment cored from Bob Black Pond, which Dr. Watts also studied in the early 1970’s, begins. 

Dr. Stephen Jackson of Wyoming University also studied Bob Black Pond over 20 years later.  He found boreal forest species dating to about 22,000 BP.  In addition to pollen he found plant macrofossils of white pine, red pine, jack pine, white spruce, Critchfield’s spruce, and paper birch.  Critchfield’s spruce is an extinct species thought to be adapted to temperate climates, and white pine still grows on the mountains of north Georgia, but the other 4 species no longer range much further south than Canada.

Jack pine present day range map.  This species lived as far south as northwest Georgia during the LGM.  Today, it lives no further south than northern Michigan.  Red pine is restricted to New England.  White spruce lives across Canada as does paper birch.

There’s no doubt the climate in north Georgia during the Last Glacial Maximum was cooler than that of today, but it wasn’t necessarily as cool as present day southern Canada, despite the presence of Canadian species of trees.  Scientists may have originally misinterpeted this data when they assumed the climate here was comparable to today’s southern Canada.  Pine and grass grow better in atmospheres with lower CO2 than broad-leafed trees.  So moderately lower temperatures combined with lower CO2 levels allowed northern species of conifers to compete better with oaks, maples, and other broad-leafed trees for space in the southern Appalachians.  It’s a good thing for the boreal species too because their present day range was completely under miles of ice then.

Fossil pollen from Pigeon Marsh in Walker County dates to approximately the LGM.  Jack and red pine pollen ranges from 25%-45%, oak pollen ranges from 30%-40%, and spruce pollen ranges from 1%-2%.  Hickory and chestnut were present but not abundant.   After the LGM, as the climate remained cool but became more moist, beech became the dominant tree here until the modern floral composition took over.

During the Pleistocene sagponds would’ve been prime foraging grounds for herds of hungry mastodons.  Sagponds supported the kinds of aquatic plants (especially buttonbush and pond cypress) that we know mastodons ate from analysis of their coprolites.  And indeed, fossil evidence of mastodons has been found in the ridge and valley region of Georgia and Tennessee.

References:

Watts, W. A.

“The Vegetation Record of a Mid-Wisconsinian Interstadial in Northwest Georgia”

Quaternary Research 3 (2) 1973

Wharton, Charles

The Natural Environments of Georgia

Georgia Department of Natural Resources 1980