Carolina Bay
Encyclopedia
Carolina bays are elliptical depressions concentrated along the Atlantic seaboard within coastal Delaware
, Maryland
, New Jersey
, North Carolina
, South Carolina
, Virginia
, Georgia
, and northcentral Florida
(Prouty 1952, Kaczorowski 1977). In Maryland, they are called Maryland Basins (Rasmussen and Slaughter 1955).
Other landform depressions, not widely accepted as Carolina bays, are found within the northern Gulf of Mexico
coastal plain in southeast Mississippi
and Alabama
, where they are known as either Grady ponds or Citronelle ponds (Otvos 1976, Folkerts 1997). Carolina bays vary in size from one to several thousand acres. About 500,000 of them are present in the classic area of the Atlantic Coastal Plain, often in groups, with each bay invariably aligned in a northwest-southeast direction. The bays have many different vegetative structures, based on the depression depth, size, hydrology
, and subsurface. Many are marshy; a few of the larger ones are (or were before drainage) lakes; 36 square km (14 square mile) Lake Waccamaw
is an undrained one. Some bays are predominantly open water with large scattered pond cypress
, while others are composed of thick, shrubby areas (pocosin
s), with vegetation growing on floating peat mats. Generally the southeastern end has a higher rim composed of white sand. They are named for the bay trees frequently found in them, not because of the frequent ponding of water (Sharitz 2003).
Undrained, often circular to oval, depressions exhibiting a wide range of area and depth are also a very common feature of the Gulf of Mexico coastal plain within Texas and southwest Louisiana. These depressions vary in size from 0.4 to 3.6 km (0.25 to 2 miles) in diameter. Within Harris County, Texas, raised rims, which are about 0.65 m (2 ft) high, partially enclosed these depressions. In the scientific literature, they are known by a variety of names, including “pocks”, “pock marks”, “bagols”, “lacs ronds”, and “natural ponds” (Aronow nda, ndb).
, including some rare
and/or endangered species
. Species that thrive in the bays' habitat
s include birds, such as wood stork
s, heron
s, egret
s, and other migratory
waterfowl
, mammals such as deer
, black bears
, raccoons, skunk
s, and opossums.
Other residents include dragonflies, green anoles and green tree frog
s.
The bays contain trees such as black gum, bald cypress, pond cypress, sweet bay, loblolly bay
, red bay
, sweet gum, maple
, magnolia
, pond pine
, and shrubs such as fetterbush
, clethra, sumac
, button bush
, zenobia, and gallberry
. Plants common in Carolina bays are water lilies
, sedges and various grasses. Several carnivorous plants inhabit Carolina bays, including bladderwort
, butterwort, pitcher plant
, and sundew
.
Some of the bays have been greatly modified within human history, under pressure from farming, highway building, housing developments and golf course
s. Carvers Bay, a large one in Georgetown County was used as a bomb
ing practice range during World War II
. It has been drained and is mostly used for tree farming
today. Others are used for vegetable
or field crops
with drainage
.
In South Carolina, Woods Bay, on the Sumter-Clarendon County line near Turbeville
has been designated a state park to preserve it as much as possible in its natural state. Also in Clarendon County (near Manning
), another bay, Bennett's Bay, is a Heritage Preserve.
Another bay in Bamberg County, South Carolina
is owned by the South Carolina Native Plant Society, which has been developing a 52 acres (210,436.7 m²) preserve called the Lisa Matthews Memorial Bay, which is trying to preserve and increase the federally endangered wildflower Oxypolis canbyi (Canby's Dropwort) in the bay. The uplands area surrounding the bay is being restored from a loblolly pine
plantation to the original longleaf pine
. Included in the longleaf restoration is the restoration of wiregrass (Aristida beyrichiana) as a key understory plant. Its flammability aids in periodic burning, which is necessary for Canby's Dropwort and many of the other species unique to the environment.
, but in the area of southeastern Indiana
and southwestern Ohio
.
At the northern end of the distribution of Carolina bays within the Delmarva Peninsula
, the average orientation of the long axes abruptly shifts by about 112 degrees to N48°E. Further north, the orientation of the long axes becomes, at best, distinctly bimodal, and exhibits two greatly divergent directions and, at worst, completely random and lacking any preferred direction (Kacrovowski, 1977). Plate 3 of Rasmussen and Slaughter (1955), which is reproduced as Figure 51 of Kacrovowski (1977), illustrates the disorganized nature of the orientations of the long axes of Carolina bays within the northernmost part of their distribution within Somerset
, Wicomico
, and Worcester
counties, Maryland.
At the southern end of their distribution, the Carolina bays in southern Georgia and northern Florida are approximately circular in shape. In this area, they have a weak northerly orientation (Kacrovowski, 1977). The Carolina bays in southern Mississippi and Alabama are elliptical to roughly circular in shape. The measurement of the long axes of 200 elliptical Grady / Citronelle ponds found a very distinct orientation tightly clustered about N25°W in southwestern Baldwin County, Alabama
(Otvos 1976).
Within the Atlantic Coast Plain, the measured orientation of the long axes of Carolina bays and the Pleistocene direction of movement of adjacent sand dunes, where present, are generally perpendicular to each other. In southern Georgia and northern Florida, the northerly orientation is matched by a westerly orientation of the direction of Pleistocene movement of sand dunes (Markewich and Markewich 1994). Northward from northern Georgia to Virginia, the average orientation of direction of Pleistocene movement of parabolic sand dunes systematically shifts along with the average orientation of the long axes of Carolina bays as to always lie approximately perpendicular to them. In The Delmarva Peninsula, the 112 degrees shift in the average trend of the long axes is also accompanied by a corresponding shift in the average direction of Pleistocene movement of parabolic sand dunes such that their direction of movement is also perpendicular to the long axes, as is the case in the rest of the Atlantic Coastal Plain (Carver and Brooks 1989).
radiocarbon in age. The finite radiocarbon dates range in age from 440 ± 50 to 27,700 ±2,600 BP radiocarbon in age (Whitehead 1981, Gaiser et al. 2001). Some samples are so old, they contained insufficient radiocarbon for dating, which results in "greater than" dates. For example, samples from sediments filling Carolina bays have been dated at greater than 38,000 to 49,550 BP radiocarbon years (Frey 1955, Brooks et al. 2001).
In cases where multiple radiocarbon dates have been determined from a single core, radiocarbon dates are consistent in terms of their stratigraphic position within a core and accumulation rates calculated from them with only the occasional exception. Given the nature of radiocarbon dating, such discordant dates occasionally occur even in undisturbed deposits, when multiple samples were dated. The occasional discordant dates by themselves are meaningless as an indicator of disturbance, contrary to the arguments of Firestone (2006). The intact internal stratigraphy of the bay sediments, their paleosols, and their pollen zones, i.e. as observed by Brook et al. (2001) in case of Big Bay, refutes such arguments.
As discussed by Gaiser et al. (2001), radiocarbon dates reported from any Carolina bay are all minimum dates for their formation. Because only organic matter can be dated by radiocarbon dating, the reported radiocarbon dates only represents times during which organic matter of some type accumulated in Carolina bays and was later preserved. At other times, datable organic matter would either not have been preserved as sediment accumulated within them, or older organic matter destroyed when they dried out completely. During glacial periods when sea level was 130 meters (400 ft) below present, the water table would have been below the bottom of the vast majority of the bays. At such times, any organic matter would have been destroyed by oxidization and weathering of the lake bottom. Also, at that time eolian processes would have eroded any existing sediments filling the bottom of many bays removing any older lake sediments and the pollen, and datable organic matter. As a result, it is highly unlikely that organic matter dating to the exact age of any Carolina Bay would have been preserved except in the deepest of them. Thus, the oldest radiocarbon date from a Carolina Bay only indicates when the water table rose high enough for a permanent lake or swamp to exist within it (Gaiser et al. 2001).
About Carolina bays in general, Ivester et al. (2004a) concluded:
and
Based on OSL dating, Brooks et al. (1996, 2001), Grant et al. (1998), and Ivester et al. (2002, 2003, 2004b) argue that lacustrine and eolian processes have periodically modified the shape and size of the Carolina bays during the last 100,000 to 120,000 years. For example, Ivester et al. (2003), using OSL dating, dated the nested, concentric sand rims, which are found in Big Bay, a Carolina bay in South Carolina. From the outside to the inside the age of the rim becomes progressively younger, i.e. 35,660±2600; 25,210±1900; 11,160±900; and 2,150±300 years BP. These dates demonstrate that Big Bay has shrunk over the last 36,000 years by 1.6 miles (2.6 km). Ivester et al. (2004a) also found these rims to be composed, not of impact ejecta, but rather "are composed of both shoreface and eolian deposits". Concerning the Carolina bays, they concluded:
On the basis of 45 OSL dates from and sedimentological analyses of rims of Carolina bays in Georgia and South Carolina, Ivester et al. (2007) concluded that a single Carolina bay was actively modified between 12,000 to 50,000 BP; 60,000 to 80,000 BP; and 120,000 to 140,000 BP. His conclusions is collaborated by the OSL dating done by Brooks et al. (1996, 2001), Grant et al. (1998), and Ivester et al. (2002, 2003, 2004b) on other Carolina Bays and the fact not all Carolina Bays are as perfectly aligned as they are claimed to be. In any one location, the orientation of their long axes varies by 10 to 15 degrees as discussed in Johnson (1942), Kacrovowski (1977), and Carver and Brooks (1989). Plate 3 of Kacrovowski (1977) also shows the long axes of Carolina bays becomes, at best, distinctly bimodal and exhibits two greatly divergent directions and, at worst, completely random and lacking any preferred direction within the northernmost part of their distribution, i.e. Somerset, Wicomico and Worcester counties, Maryland.
Within cores of undisturbed sediments recovered from Big Bay, North Carolina, Brook et al. (2001) documented well-defined pollen zones consisting of distinct pollen assemblages. They found a stratigraphically consistent series of pollen zones, which increased in age consistently with depth from Holocene interglacial epoch to the Wisconsinan glacial epoch, back into oxygen isotope stage 5, 75,000 to 134,000 years BP. These pollen zones collaborate the dating of Big Bay by OSL and radiocarbon dating.
have been proposed to account for the bays, including action of sea
currents
when the area was under the ocean
or the upwelling of ground water at a later time. One major theory within the earth sciences academic community is that a combination of processes created the shapes and orientations of these ancient landforms, including climate change, the formation of siliclastic karst by solution of subsurface material during glacial sealevel lowstands and later modification of these depressions by periodic eolian and lacustrine processes.
Various proposals that they were either directly or indirectly created by a meteorite shower or exploding comet are disputed by many scientists for an apparent lack of extraterrestrial material, absence of shocked quartz and "bedrock" deformation associated with larger bays, and extremely low ratio of depth to diameter of the larger bays. More information on these theories can be found at: Carolina Bays.
Quaternary geologists and geomorphologists argue that the peculiar features of Carolina bays can be readily explained by known terrestrial processes and repeated modification by eolian and lacustrine processes of them over the past 70,000 to 100,000 years. http://eeg.geoscienceworld.org/cgi/content/abstract/5/3/261. Also, quaternary geologists and geomorphologists believe to have found a correspondence in time between when the active modification of the rims of Carolina bays most commonly occurred and when adjacent sand dunes were active during the Wisconsin glaciation between 15,000 and 40,000 years and 70,000 to 80,000 years BP http://gsa.confex.com/gsa/2004AM/finalprogram/abstract_78899.htm. In addition, quaternary geologists and geomorphologists have repeatedly found that the orientations of the Carolina bays are consistent with the wind patterns which existed during the Wisconsin glaciation as reconstructed from Pleistocene parabolic dunes, a time when the shape of the Carolina bays was being modified http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6R-48C7H09-11W&_user=3787556&_coverDate=11%2F30%2F1989&_rdoc=2&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%235821%231989%23999259996%23567345%23FLP%23display%23Volume)&_cdi=5821&_sort=d&_docanchor=&view=c&_ct=15&_acct=C000061383&_version=1&_urlVersion=0&_userid=3787556&md5=74136fc47efd27f5ca168517637c0d4c.
New hypotheses arose again in the 1980s and 1990s, spurred on by various attention to impacts such as the Tunguska event
, Cretaceous–Tertiary extinction event and a theorized link to the unsolved scientific mystery of the Younger Dryas event. Impact geologists determined the depressions are too shallow to be impact features. Reports of magnetic anomalies turned out not to show consistency across the sites. There were no meteorite fragments or impact crater geologic structures. None of the necessary evidence for an impact was found. The conclusion was to reject the impact theory at the Carolina bays.
Delaware
Delaware is a U.S. state located on the Atlantic Coast in the Mid-Atlantic region of the United States. It is bordered to the south and west by Maryland, and to the north by Pennsylvania...
, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
, North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
, South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
, Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
, Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
, and northcentral Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
(Prouty 1952, Kaczorowski 1977). In Maryland, they are called Maryland Basins (Rasmussen and Slaughter 1955).
Other landform depressions, not widely accepted as Carolina bays, are found within the northern Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
coastal plain in southeast Mississippi
Mississippi
Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...
and Alabama
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
, where they are known as either Grady ponds or Citronelle ponds (Otvos 1976, Folkerts 1997). Carolina bays vary in size from one to several thousand acres. About 500,000 of them are present in the classic area of the Atlantic Coastal Plain, often in groups, with each bay invariably aligned in a northwest-southeast direction. The bays have many different vegetative structures, based on the depression depth, size, hydrology
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
, and subsurface. Many are marshy; a few of the larger ones are (or were before drainage) lakes; 36 square km (14 square mile) Lake Waccamaw
Lake Waccamaw
Lake Waccamaw is a unique fresh water lake located in Columbus County in North Carolina. The lake is oval in shape and measures roughly 5.2 by with an average depth of . It covers 36,170,802 square meters, an average width of 2.32 meters and a shoreline of about 22,852 meters...
is an undrained one. Some bays are predominantly open water with large scattered pond cypress
Taxodium ascendens
Taxodium ascendens, also known as Pond Cypress, is a deciduous conifer of the genus Taxodium, native to North America. Many botanists treat it as a variety of Bald Cypress, Taxodium distichum Taxodium ascendens, also known as Pond Cypress, is a deciduous conifer of the genus Taxodium, native to...
, while others are composed of thick, shrubby areas (pocosin
Pocosin
Pocosin is a term for a type of palustrine wetland with deep, acidic, sandy, peat soils. Groundwater saturates the soil except during brief seasonal dry spells and during prolonged droughts...
s), with vegetation growing on floating peat mats. Generally the southeastern end has a higher rim composed of white sand. They are named for the bay trees frequently found in them, not because of the frequent ponding of water (Sharitz 2003).
Undrained, often circular to oval, depressions exhibiting a wide range of area and depth are also a very common feature of the Gulf of Mexico coastal plain within Texas and southwest Louisiana. These depressions vary in size from 0.4 to 3.6 km (0.25 to 2 miles) in diameter. Within Harris County, Texas, raised rims, which are about 0.65 m (2 ft) high, partially enclosed these depressions. In the scientific literature, they are known by a variety of names, including “pocks”, “pock marks”, “bagols”, “lacs ronds”, and “natural ponds” (Aronow nda, ndb).
Ecological Significance and Biodiversity
The bays are especially rich in biodiversityBiodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
, including some rare
Rare species
A rare species is a group of organisms that are very uncommon or scarce. This designation may be applied to either a plant or animal taxon, and may be distinct from the term "endangered" or "threatened species" but not "extinct"....
and/or endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
. Species that thrive in the bays' habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s include birds, such as wood stork
Wood Stork
The Wood Stork is a large American wading bird in the stork family Ciconiidae. It was formerly called the "Wood Ibis", though it is not really an ibis.-Appearance:...
s, heron
Heron
The herons are long-legged freshwater and coastal birds in the family Ardeidae. There are 64 recognised species in this family. Some are called "egrets" or "bitterns" instead of "heron"....
s, egret
Egret
An egret is any of several herons, most of which are white or buff, and several of which develop fine plumes during the breeding season. Many egrets are members of the genera Egretta or Ardea which contain other species named as herons rather than egrets...
s, and other migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
, mammals such as deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
, black bears
American black bear
The American black bear is a medium-sized bear native to North America. It is the continent's smallest and most common bear species. Black bears are omnivores, with their diets varying greatly depending on season and location. They typically live in largely forested areas, but do leave forests in...
, raccoons, skunk
Skunk
Skunks are mammals best known for their ability to secrete a liquid with a strong, foul odor. General appearance varies from species to species, from black-and-white to brown or cream colored. Skunks belong to the family Mephitidae and to the order Carnivora...
s, and opossums.
Other residents include dragonflies, green anoles and green tree frog
Tree frog
Hylidae is a wide-ranging family of frogs commonly referred to as "tree frogs and their allies". However, the hylids include a diversity of frog species, many of which do not live in trees, but are terrestrial or semi-aquatic.-Characteristics:...
s.
The bays contain trees such as black gum, bald cypress, pond cypress, sweet bay, loblolly bay
Gordonia
Gordonia is a genus of flowering plants in the family Theaceae, related to Franklinia, Camellia and Stewartia. Of the roughly 40 species, all but two are native to southeast Asia in southern China, Taiwan and Indochina. The remaining species, G...
, red bay
Persea
Persea is a genus of about 150 species of evergreen trees belonging to the laurel family, Lauraceae. The best-known member of the genus is the avocado, P. americana, widely cultivated in subtropical regions for its large, edible fruit.-Overview:...
, sweet gum, maple
Maple
Acer is a genus of trees or shrubs commonly known as maple.Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in...
, magnolia
Magnolia
Magnolia is a large genus of about 210 flowering plant species in the subfamily Magnolioideae of the family Magnoliaceae. It is named after French botanist Pierre Magnol....
, pond pine
Pond Pine
Pinus serotina is a tree found along the Atlantic coastal plain of the eastern United States, from southern New Jersey south to Florida and west to southern Alabama...
, and shrubs such as fetterbush
Pieris (plant)
Pieris is a genus of seven species of shrubs in the family Ericaceae, native to mountain regions of eastern and southern Asia, eastern North America and Cuba. Known commonly as andromedas or fetterbushes, they are broad-leaved evergreen shrubs growing to 1–6 m tall and wide...
, clethra, sumac
Sumac
Sumac is any one of approximately 250 species of flowering plants in the genus Rhus and related genera, in the family Anacardiaceae. Sumacs grow in subtropical and temperate regions throughout the world, especially in Africa and North America....
, button bush
Cephalanthus occidentalis
Cephalanthus occidentalis is a species of flowering plant in the coffee family, Rubiaceae, that is native to eastern and southern North America. Common names include Buttonbush, Common Buttonbush, Button-willow and Honey-bells....
, zenobia, and gallberry
Gallberry
Gallberry refers to two similar shrubs in the Holly family:* Ilex coriacea* Ilex glabraGallberry refers to two similar shrubs in the Holly family:* Ilex coriacea* Ilex glabra...
. Plants common in Carolina bays are water lilies
Nymphaeaceae
Nymphaeaceae is a family of flowering plants. Members of this family are commonly called water lilies and live in freshwater areas in temperate and tropical climates around the world. The family contains eight genera. There are about 70 species of water lilies around the world. The genus...
, sedges and various grasses. Several carnivorous plants inhabit Carolina bays, including bladderwort
Bladderwort
Utricularia, commonly and collectively called the bladderworts, is a genus of carnivorous plants consisting of approximately 233 species . They occur in fresh water and wet soil as terrestrial or aquatic species across every continent except Antarctica...
, butterwort, pitcher plant
Pitcher plant
Pitcher plants are carnivorous plants whose prey-trapping mechanism features a deep cavity filled with liquid known as a pitfall trap. It has been widely assumed that the various sorts of pitfall trap evolved from rolled leaves, with selection pressure favouring more deeply cupped leaves over...
, and sundew
Sundew
Drosera, commonly known as the sundews, comprise one of the largest genera of carnivorous plants, with at least 194 species. These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginous glands covering their leaf surface. The insects are used to supplement...
.
Some of the bays have been greatly modified within human history, under pressure from farming, highway building, housing developments and golf course
Golf course
A golf course comprises a series of holes, each consisting of a teeing ground, fairway, rough and other hazards, and a green with a flagstick and cup, all designed for the game of golf. A standard round of golf consists of playing 18 holes, thus most golf courses have this number of holes...
s. Carvers Bay, a large one in Georgetown County was used as a bomb
Bomb
A bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy...
ing practice range during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. It has been drained and is mostly used for tree farming
Forestry
Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...
today. Others are used for vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
or field crops
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
with drainage
Drainage
Drainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...
.
In South Carolina, Woods Bay, on the Sumter-Clarendon County line near Turbeville
Turbeville, South Carolina
Turbeville is a town in Clarendon County, South Carolina, United States. The population was 766 at the 2010 census.-Geography:Turbeville is located at...
has been designated a state park to preserve it as much as possible in its natural state. Also in Clarendon County (near Manning
Manning, South Carolina
Manning is a city in South Carolina and the county seat of Clarendon County in the Southeastern United States, located in the center of the county, just to the east of Interstate 95 and at the intersection of U.S. 301 and U.S. 521. The population was estimated to be 3,943 as of 2008, down 2% from...
), another bay, Bennett's Bay, is a Heritage Preserve.
Another bay in Bamberg County, South Carolina
Bamberg County, South Carolina
-Demographics:As of the census of 2000, there were 16,658 people, 6,123 households, and 4,255 families residing in the county. The population density was 42 people per square mile . There were 7,130 housing units at an average density of 18 per square mile...
is owned by the South Carolina Native Plant Society, which has been developing a 52 acres (210,436.7 m²) preserve called the Lisa Matthews Memorial Bay, which is trying to preserve and increase the federally endangered wildflower Oxypolis canbyi (Canby's Dropwort) in the bay. The uplands area surrounding the bay is being restored from a loblolly pine
Loblolly Pine
Pinus taeda is one of several pines native to the Southeastern United States, from central Texas east to Florida, and north to Delaware. It is particularly dominant in the eastern half of North Carolina, where there are huge expanses consisting solely of Loblolly Pine trees...
plantation to the original longleaf pine
Longleaf Pine
Pinus palustris, commonly known as the Longleaf Pine, is a pine native to the southeastern United States, found along the coastal plain from eastern Texas to southeast Virginia extending into northern and central Florida....
. Included in the longleaf restoration is the restoration of wiregrass (Aristida beyrichiana) as a key understory plant. Its flammability aids in periodic burning, which is necessary for Canby's Dropwort and many of the other species unique to the environment.
Orientation
As measured by Johnson (1942) and Kacrovowski (1977), the orientation of the long axes of Carolina bays systematically rotate northward along the Atlantic Coastal Plain from northern Georgia to northern Virginia; the average trend of the long axes of Carolina Bays varies from N16°W in eastcentral Georgia to N22°W in southern South Carolina, N39°W in northern South Carolina, N49°W in North Carolina, and N64°W in Virginia. Within this part of the Atlantic Coastal Plain, the orientation of the long axes of Carolina bays varies by 10 to 15 degrees (Johnson 1942, Kacrovowski, 1977, Carver and Brooks 1989). If the long axes of these Carolina bays, as measured by Johnson (1942), are projected westward, they converge, neither in the Great Lakes nor CanadaCanada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, but in the area of southeastern Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
and southwestern Ohio
Ohio
Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
.
At the northern end of the distribution of Carolina bays within the Delmarva Peninsula
Delmarva Peninsula
The Delmarva Peninsula is a large peninsula on the East Coast of the United States, occupied by most of Delaware and portions of Maryland and Virginia...
, the average orientation of the long axes abruptly shifts by about 112 degrees to N48°E. Further north, the orientation of the long axes becomes, at best, distinctly bimodal, and exhibits two greatly divergent directions and, at worst, completely random and lacking any preferred direction (Kacrovowski, 1977). Plate 3 of Rasmussen and Slaughter (1955), which is reproduced as Figure 51 of Kacrovowski (1977), illustrates the disorganized nature of the orientations of the long axes of Carolina bays within the northernmost part of their distribution within Somerset
Somerset County, Maryland
-2010:Whereas according to the 2010 U.S. Census Bureau:*53.5% White*42.3% Black*0.3% Native American*0.7% Asian*0.0% Native Hawaiian or Pacific Islander*1.7% Two or more races*1.5% Other races*3.3% Hispanic or Latino -2000:...
, Wicomico
Wicomico County, Maryland
As of the census of 2010, there were 98,733 people, 37,220 households, and 24,172 families residing in the county. The population density was 261.7 people per square mile . There were 41,192 housing units at an average density of 109.2 per square mile...
, and Worcester
Worcester County, Maryland
-2010:Whereas according to the 2010 U.S. Census Bureau:*82.0% White*13.6% Black*0.3% Native American*1.1% Asian*0.0% Native Hawaiian or Pacific Islander*1.7% Two or more races*1.3% Other races*3.2% Hispanic or Latino -2000:...
counties, Maryland.
At the southern end of their distribution, the Carolina bays in southern Georgia and northern Florida are approximately circular in shape. In this area, they have a weak northerly orientation (Kacrovowski, 1977). The Carolina bays in southern Mississippi and Alabama are elliptical to roughly circular in shape. The measurement of the long axes of 200 elliptical Grady / Citronelle ponds found a very distinct orientation tightly clustered about N25°W in southwestern Baldwin County, Alabama
Baldwin County, Alabama
-2010:Whereas according to the 2010 U.S. Census Bureau:*85.7% White*9.4% Black*0.7% Native American*0.7% Asian*0.0% Native Hawaiian or Pacific Islander*1.5% Two or more races*4.4% Hispanic or Latino -2000:...
(Otvos 1976).
Within the Atlantic Coast Plain, the measured orientation of the long axes of Carolina bays and the Pleistocene direction of movement of adjacent sand dunes, where present, are generally perpendicular to each other. In southern Georgia and northern Florida, the northerly orientation is matched by a westerly orientation of the direction of Pleistocene movement of sand dunes (Markewich and Markewich 1994). Northward from northern Georgia to Virginia, the average orientation of direction of Pleistocene movement of parabolic sand dunes systematically shifts along with the average orientation of the long axes of Carolina bays as to always lie approximately perpendicular to them. In The Delmarva Peninsula, the 112 degrees shift in the average trend of the long axes is also accompanied by a corresponding shift in the average direction of Pleistocene movement of parabolic sand dunes such that their direction of movement is also perpendicular to the long axes, as is the case in the rest of the Atlantic Coastal Plain (Carver and Brooks 1989).
Age
The age of the Carolina bays is constrained by a variety of dating techniques, as predating the end of the Pleistocene by ten of thousands to over a hundred thousand years. The techniques, which demonstrate a preterminal Pleistocene age for the Carolina bays, are radiocarbon dating, optically stimulated luminescence (OSL) dating, and palynology.Radiocarbon dates
As illustrated in Figure 3 of Heinrich (2005), numerous radiocarbon dates have been collected from the sediments, which fill the basins of Carolina bays. The majority of these samples, from which these dates were obtained, were collected from cores of undisturbed sediments that filled Carolina bays in North and South Carolina. These cores were collected to reconstruct region paleoenvironmental records using pollen, diatoms, and other fossils found in the distinctly and conformably layered sediments that fill the Carolina bays (Brooks et al. 2001, Frey, 1953, Frey 1955, Gaiser et al. 2001, Watts 1980, Whitehead 1981). Additional radocarbon dates have been obtained from organic matter collected from the undisturbed sediments filling Carolina bays by Blilet and Burney (1957). Kaczorowski (1977), Mixon and Pilkey (1976), and Thom (1970). Many radiocarbon dates, which were obtained from organic matter preserved within undisturbed sediments are greater than 14,000 BP
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
radiocarbon in age. The finite radiocarbon dates range in age from 440 ± 50 to 27,700 ±2,600 BP radiocarbon in age (Whitehead 1981, Gaiser et al. 2001). Some samples are so old, they contained insufficient radiocarbon for dating, which results in "greater than" dates. For example, samples from sediments filling Carolina bays have been dated at greater than 38,000 to 49,550 BP radiocarbon years (Frey 1955, Brooks et al. 2001).
In cases where multiple radiocarbon dates have been determined from a single core, radiocarbon dates are consistent in terms of their stratigraphic position within a core and accumulation rates calculated from them with only the occasional exception. Given the nature of radiocarbon dating, such discordant dates occasionally occur even in undisturbed deposits, when multiple samples were dated. The occasional discordant dates by themselves are meaningless as an indicator of disturbance, contrary to the arguments of Firestone (2006). The intact internal stratigraphy of the bay sediments, their paleosols, and their pollen zones, i.e. as observed by Brook et al. (2001) in case of Big Bay, refutes such arguments.
As discussed by Gaiser et al. (2001), radiocarbon dates reported from any Carolina bay are all minimum dates for their formation. Because only organic matter can be dated by radiocarbon dating, the reported radiocarbon dates only represents times during which organic matter of some type accumulated in Carolina bays and was later preserved. At other times, datable organic matter would either not have been preserved as sediment accumulated within them, or older organic matter destroyed when they dried out completely. During glacial periods when sea level was 130 meters (400 ft) below present, the water table would have been below the bottom of the vast majority of the bays. At such times, any organic matter would have been destroyed by oxidization and weathering of the lake bottom. Also, at that time eolian processes would have eroded any existing sediments filling the bottom of many bays removing any older lake sediments and the pollen, and datable organic matter. As a result, it is highly unlikely that organic matter dating to the exact age of any Carolina Bay would have been preserved except in the deepest of them. Thus, the oldest radiocarbon date from a Carolina Bay only indicates when the water table rose high enough for a permanent lake or swamp to exist within it (Gaiser et al. 2001).
OSL dating
Over the last several years, Ivester et al. (2002, 2003, 2004a, 2004b, 2007) have dated the sand rims of numerous Carolina bays using optically stimulated luminescence (OSL) They found sand rims of many Carolina bays to be as old as 80,000 to 100,000 BP. For example, Ivester et al. (2002) wrote about Flamingo Bay, a Carolina bay:About Carolina bays in general, Ivester et al. (2004a) concluded:
and
Based on OSL dating, Brooks et al. (1996, 2001), Grant et al. (1998), and Ivester et al. (2002, 2003, 2004b) argue that lacustrine and eolian processes have periodically modified the shape and size of the Carolina bays during the last 100,000 to 120,000 years. For example, Ivester et al. (2003), using OSL dating, dated the nested, concentric sand rims, which are found in Big Bay, a Carolina bay in South Carolina. From the outside to the inside the age of the rim becomes progressively younger, i.e. 35,660±2600; 25,210±1900; 11,160±900; and 2,150±300 years BP. These dates demonstrate that Big Bay has shrunk over the last 36,000 years by 1.6 miles (2.6 km). Ivester et al. (2004a) also found these rims to be composed, not of impact ejecta, but rather "are composed of both shoreface and eolian deposits". Concerning the Carolina bays, they concluded:
On the basis of 45 OSL dates from and sedimentological analyses of rims of Carolina bays in Georgia and South Carolina, Ivester et al. (2007) concluded that a single Carolina bay was actively modified between 12,000 to 50,000 BP; 60,000 to 80,000 BP; and 120,000 to 140,000 BP. His conclusions is collaborated by the OSL dating done by Brooks et al. (1996, 2001), Grant et al. (1998), and Ivester et al. (2002, 2003, 2004b) on other Carolina Bays and the fact not all Carolina Bays are as perfectly aligned as they are claimed to be. In any one location, the orientation of their long axes varies by 10 to 15 degrees as discussed in Johnson (1942), Kacrovowski (1977), and Carver and Brooks (1989). Plate 3 of Kacrovowski (1977) also shows the long axes of Carolina bays becomes, at best, distinctly bimodal and exhibits two greatly divergent directions and, at worst, completely random and lacking any preferred direction within the northernmost part of their distribution, i.e. Somerset, Wicomico and Worcester counties, Maryland.
Stratigraphy of Big Bay
The physical relationship of Pleistocene sand dunes to Big Bay, North Carolina, and adjacent Carolina bays further demonstrates that they are tens of thousands of years old (Brooks et al. 2001). In this case, during the Pleistocene, sand dunes have migrated from the valley wall of the Wateree River into, and partially filled, Big Bay and an adjacent Carolina bay. According to basic principles of cross-cutting relationships and superposition, both Carolina bays were first created and the sand dunes later migrated into them. Thus, the sand dunes must be younger than Carolina bays. Since the sand dunes have been dated by OSL dating at 29,600 ± 2,400 to 33,200 ± 2,800 BP, both Carolina bays must be older than these dates.Palynology
The sequences of pollen zones recovered from cores taken from various Carolina bays by Frey (1953, 1955), Watt (1980), and Whitehead (1964, 1981) document the presence of full glacial pollen zones within the sediments filling Carolina bays. The thick sediments, which were recovered in these cores and contain pollen characteristic of full glacial conditions could have accumulated within these Carolina bays only if they had existed prior to end of the last glacial epoch. The radiocarbon dates reported by Frey (1953, 1955), Watts (1980), and Whitehead (1964, 1981) from these Carolina bay cores fully collaborate both the glacial age of the pollen and the undisturbed nature of the sediments filling these Carolina bays as indicated by the reported layering of the sediments filling them and increasing age with depth of the pollen they contain.Within cores of undisturbed sediments recovered from Big Bay, North Carolina, Brook et al. (2001) documented well-defined pollen zones consisting of distinct pollen assemblages. They found a stratigraphically consistent series of pollen zones, which increased in age consistently with depth from Holocene interglacial epoch to the Wisconsinan glacial epoch, back into oxygen isotope stage 5, 75,000 to 134,000 years BP. These pollen zones collaborate the dating of Big Bay by OSL and radiocarbon dating.
Theories of Origin
Theories of the origin of the Carolina bays fall into two major categories: that these features were created by forces within the Earth, or that they were gouged by an astronomical event or set of events.Geomorphology
Various geomorphological theoriesTheory
The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...
have been proposed to account for the bays, including action of sea
Sea
A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...
currents
Ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...
when the area was under the ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
or the upwelling of ground water at a later time. One major theory within the earth sciences academic community is that a combination of processes created the shapes and orientations of these ancient landforms, including climate change, the formation of siliclastic karst by solution of subsurface material during glacial sealevel lowstands and later modification of these depressions by periodic eolian and lacustrine processes.
Various proposals that they were either directly or indirectly created by a meteorite shower or exploding comet are disputed by many scientists for an apparent lack of extraterrestrial material, absence of shocked quartz and "bedrock" deformation associated with larger bays, and extremely low ratio of depth to diameter of the larger bays. More information on these theories can be found at: Carolina Bays.
Quaternary geologists and geomorphologists argue that the peculiar features of Carolina bays can be readily explained by known terrestrial processes and repeated modification by eolian and lacustrine processes of them over the past 70,000 to 100,000 years. http://eeg.geoscienceworld.org/cgi/content/abstract/5/3/261. Also, quaternary geologists and geomorphologists believe to have found a correspondence in time between when the active modification of the rims of Carolina bays most commonly occurred and when adjacent sand dunes were active during the Wisconsin glaciation between 15,000 and 40,000 years and 70,000 to 80,000 years BP http://gsa.confex.com/gsa/2004AM/finalprogram/abstract_78899.htm. In addition, quaternary geologists and geomorphologists have repeatedly found that the orientations of the Carolina bays are consistent with the wind patterns which existed during the Wisconsin glaciation as reconstructed from Pleistocene parabolic dunes, a time when the shape of the Carolina bays was being modified http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6R-48C7H09-11W&_user=3787556&_coverDate=11%2F30%2F1989&_rdoc=2&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%235821%231989%23999259996%23567345%23FLP%23display%23Volume)&_cdi=5821&_sort=d&_docanchor=&view=c&_ct=15&_acct=C000061383&_version=1&_urlVersion=0&_userid=3787556&md5=74136fc47efd27f5ca168517637c0d4c.
Impact event
The cometary impact theory of the origin of the bays was popular among earth scientists of the 1930s and 40s. It said that they were the result of a low density comet exploding above or impacting with the Laurentide ice sheet about 12,900 years ago.New hypotheses arose again in the 1980s and 1990s, spurred on by various attention to impacts such as the Tunguska event
Tunguska event
The Tunguska event, or Tunguska blast or Tunguska explosion, was an enormously powerful explosion that occurred near the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia, at about 7:14 a.m...
, Cretaceous–Tertiary extinction event and a theorized link to the unsolved scientific mystery of the Younger Dryas event. Impact geologists determined the depressions are too shallow to be impact features. Reports of magnetic anomalies turned out not to show consistency across the sites. There were no meteorite fragments or impact crater geologic structures. None of the necessary evidence for an impact was found. The conclusion was to reject the impact theory at the Carolina bays.
External links
- Anonymous, 2007, Geology and Ecology of Carolina Bays. Southeastern Section–56th Annual Meeting (29–30 March 2007) Savannah, Georgia.
- Bob, nd, More Carolina Bay Information., Comets, Culture, and Currency? Web Site, Athens, Georgia.
- David, M., and J.L. Gilbride, 2011, LiDAR-Derived Digital Elevation Maps Of The Delmarva Peninsula And Southern New Jersey Used To Identify Carolina Bay Landforms; Their Planform Shape And Orientation Changes Systematically With Latitude. Geological Society of America Abstracts with Programs. v. 43, no. 5, p. 629.
- Eyton, R.J., and J.I. Parkhurst, 1975, Analysis of Extraterrestrial Origin of Carolina Bays. Paper no. 9, Geography Graduate Student Association, University of Illinois, Urbana, Illinois.
- Goodwin, B.K., and G.H. Johnson, 1970, Carolina Bays in the Upland Gravels of Midlothian, Virginia. Part 2, Eleventh Annual Field Conference of the Atlantic Coastal Plain Geological Association Guidebook. Williamsburg, Virginia, The College of William and Mary. 30 pp.
- Howard, G.A., 1997, The Carolina Bays. North Carolina.
- Ivester, A.H., 2002, Carolina Bays and inland dunes of the Southern Atlantic Coastal Plain yield new evidence for regional paleoclimate.. Geological Society of America Abstracts with Programs. v. 34, no. 6, pp. 273-274.
- Ivester, A.H., M.J. Brooks, and B.E. Taylor, 2007, Sedimentology and Ages of Carolina Bay Sand Rims. Geological Society of America Abstracts with Programs. v. 39, no. 2, p. 5.
- Ivester, A.H., D.I. Godfrey-Smith, M.J. Brooks, and B.E. Taylor, 2003, Concentric sand rims document the evolution of a Carolina Bay in the middle coastal plain of South Carolina. Geological Society of America Abstracts with Programs. v. 35, no. 6, p. 169.
- May, J.H., and A.G. Warne, 1999, Hydrogeologic and geochemical factors required for the development of Carolina Bays along the Atlantic and Gulf of Mexico, coastal plain, USA Environmental & Engineering Geoscience. v. 5, no. 3, pp. 261-270.
- Moore, C.M., and M.J. Brooks, 2011, Evidence for Widespread Eolian Activity in the Coastal Plain Uplands of North and South Carolina Revealed by High-Resolution LiDAR Data. PDF version Geological Society of America Abstracts with Programs. v. 43, No. 2, p. 76.
- Moore, C.M. M. J. Brooks, A.H. Ivester and T.A. Ferguson, 2011, Geoarchaeological Investigations of Carolina Bays in South Carolina: Methodological Approaches for Interpreting Site Formation Processes, Archaeostratigraphy and Geochronology. PDF version Geological Society of America Abstracts with Programs. v. 42, no. 1, p. 70.
- Pinter, N., and S.E. Ishman, 2008, Impacts, mega-tsunami, and other extraordinary claims PDF version, 304 KB. GSA Today. vol. 18, no. 1, pp. 37–38.
- Diane Tennant Series About Carolina Bays
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- Tennant, Diane, 2008a, The Carolina bays: Explaining a cosmic mystery, Part 1 The Virginian-Pilot, (September 7, 2008)
- Tennant, Diane, 2008b, Are Carolina bays related to the extinction of the mammoth?, Part 2 The Virginian-Pilot, (September 8, 2008)
- Tennant, Diane, 2008c, The Carolina bays: New evidence points to a killer comet, Part 3 The Virginian-Pilot, (September 8, 2008)