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Carolina bays are elliptical to circular depressions concentrated along the East Coast of the United States within coastal New York, New Jersey, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, and north Florida.Kaczorowski, R. T. (1977) The Carolina Bays: a Comparison with Modern Oriented Lakes Technical Report no. 13-CRD, Coastal research Division, Department of Geology, University of South Carolina, Columbia. In Maryland, they are called Maryland basins. Within the Delmarva Peninsula, they and other coastal ponds are also called Delmarva bays.Coleman, D. (2001) Delmarva Bays: Natural Enigmas. Maryland Department of Natural Resources , Annapolis. Maryland.
The earliest scientific description of Carolina bays is by L. C. Glenn (1895), who used the term "bay" (which he described as "lake-like expanses") to refer to these features near the town of Darlington, South Carolina. Glenn put quotation marks around the word "bay" but did not use the phrase "Carolina bay". A subsequent publication by F.A.Melton and William Schriever (1933) used the phrase "The Carolina Bays" (with quotation marks around the word "Bays"). Later, G. R. MacCarthy (1937) published a paper titled "The Carolina Bays", using this phrase throughout the publication (without quotation marks, and with a capital "B" for the word "Bays").
At the northern end of the distribution of Carolina bays, within the Delmarva Peninsula and New Jersey, the average orientation of the long axes abruptly shifts by about 112 degrees to N48°E. Farther north, the orientation of the long axes becomes, at best, distinctly bimodal, exhibiting two greatly divergent directions, and, at worst, completely random, lacking any preferred direction. Plate 3 of Rasmussen and Slaughter,Rasmussen, W. C., and T. H. Slaughter (1955) "The ground water resources, in The water resources of Somerset, Wicomico, and Worcester Counties". Bulletin no. 16, Maryland Geological Survey, Baltimore, Maryland. which is reproduced as Figure 51 of Kacrovowski, illustrates the disorganized nature of the orientations of the long axes of Carolina bays in 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.
Stratigraphy relations of some Carolina bays with fields of eolian dunes in river valleys suggest that Carolina bays formed episodically during different times at different places. For example:
Lake Mattamuskeet (Hyde County, North Carolina): Cores from within this Carolina bay revealed a 0.3–1.2 m thick unit of sand and silty sand (lacustrine deposits and paleosols) that rests on an unconformity above an undisturbed unit of gray clay and sandy clay (with marine shells and burrows) of Pleistocene age. Cores from the adjacent sand rims revealed a 2.6–2.9 m thick unit of silt, sand silt, and silty sand (interpreted as paleosols, shoreline, loess, and eolian deposits) that rests on an unconformity above an undisturbed unit of gray clay and sandy clay (with marine shells and burrows) of Pleistocene age (the same unit that was encountered in cores from within the Carolina bay). Charcoal and wood from a western sand rim (closer to the bay) yielded radiocarbon ages of ~5,760 and 1,270 years before present (BP). Organic sediment and charcoal from an eastern sand rim (farther from the bay) yielded radiocarbon ages ranging from ~7,750 to 2,780 years BP.
Wilson's Bay (Johnston County, North Carolina): Cores and augers from within this Carolina bay revealed a 1.5–3.2 m thick unit of sand, sandy silt, and silty sand (lacustrine deposits) that rests on an unconformity above an undisturbed unit of saprolite (weathered felsic gneiss). These lacustrine deposits yielded a radiocarbon age of ~21,920 years BP. Cores and augers from the adjacent sand rims revealed a 1.5–4.0 m thick unit of muddy sand, sand, and gravel that rests on an unconformity above an undisturbed unit of saprolite/weathered felsic gneiss (the same unit that was encountered in cores from within the Carolina bay). Organic material within the bay yielded an age of ~21,920 radiocarbon years BP.
Herndon Bay (Robeson County, North Carolina): Cores drilled into four different sand ridges associated with this Carolina bay revealed that the sand ridges are composed of 2.5–4.5 m thick accumulations of fine to coarse sand that rest on an unconformity above an undisturbed unit of black mud of Cretaceous age (Black Creek Formation). Sediment samples from sand rims associated with this Carolina bay have yielded three optically stimulated luminescence (OSL) ages of ~36,700 years ago; ~29,600 years ago; and ~27,200 years ago.
Big Bay (Sumter County, South Carolina): A core (drill hole D1/2) drilled within this Carolina bay went through the following units: (1) Drilling depth 0 to 4.5 m = eolian sand sheet that overlies the Carolina bay; (2) Drilling depth 4.5 to 9.0 m = silty sand and sandy mud with abundant organic material; and (3) Drilling depth 9.0 to 10.6 m = sandy clay of Pliocene age (Duplin Formation). Sediment samples from sand rims associated with this Carolina bay have yielded four optically stimulated luminescence (OSL) ages of ~35,700 years ago; ~25,200 years ago; ~11,200 years ago; and ~2,100 years ago.
Within cores of undisturbed sediments recovered from Big Bay, North Carolina, Brook and others 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 Stage to the Wisconsin Stage, back into marine isotope stage 5
Flamingo Bay (Aiken County, South Carolina): A core (C1) taken within this Carolina bay revealed a 0.94 m thick unit of quartz sand that rests on an unconformity (paleosol) above an undisturbed unit of sandy silt and clay of Eocene age. Charcoal samples within the 0.94 m thick unit of quartz sand yielded radiocarbon ages of ~4,500 to 2,500 years BP. A core (P25) taken from adjacent sand rim revealed a 1.85 m thick unit of Quaternary sand that rests on an unconformity (paleosol) above an undisturbed unit of sandy silt and clay of Eocene age (the same unit that was encountered in core C1 from within the Carolina bay). Moore et al. (2012) reported that sediment samples from sand ridges associated with this Carolina bay have yielded five OSL ages of ~15,000 years ago; ~13,100 years ago; ~11,500 years ago; ~9,200 years ago; and ~5,000 years ago. Brooks et al. (2010) reported that sediment samples from sand ridges associated with this Carolina Bay yielded OSL ages of ~108,700 years ago; and ~40,300 years ago.
Duke's Pond (Tattnall County, Georgia): A sediment sample from a sand rim at the margin of this Carolina has yielded an OSL age of ~23,600 years ago. Basal peat bog sediment within this Carolina bay yielded an age of ~8,600 radiocarbon years ago.
The dating of the sand rims of a number of Carolina bays by optically stimulated luminescence (OSL) techniques has yielded ages ranging from ~109,000 to ~2,000 years ago, but most ages from the sand rims range from ~40,000 to ~11,000 years ago.Savannah River Archaeological Research Program Staff (2010) Annual review of Cultural Resource Investigations by Savannah River Archaeological Research Program. South Carolina Institute of Archaeology and Anthropology, Columbia, South Carolina.
Radiocarbon dates have been obtained from organic matter collected from the undisturbed sediments filling Carolina bays by Bliley and Burney, Mixon and Pilkey,Mixon, R. B., and O. H. Pilkey, 1976, Reconnaissance geology of the submerged and emerged Coastal Plain province, Cape Lookout area, North Carolina. Professional Paper no. 859, U. S. Geological Survey, Reston, Virginia. Thom, and Kaczorowski. Some radiocarbon dates obtained from organic matter within undisturbed sediments are greater than 14,000 BP radiocarbon in age. The radiocarbon dates range from 27,700 ±2,600 to 440 ± 50 radiocarbon years BP. Some cores have contained organic matter that was too old for dating by radiocarbon methods, resulting in "greater than" dates. For example, samples from some Carolina bays have been dated at greater than 38,000 to 49,550 radiocarbon years BP. In cases where multiple radiocarbon dates have been determined from a single core, most radiocarbon dates are typically consistent in terms of their Stratigraphy position within a core, and accumulation rates calculated from them only are rarely anomalous. Given the nature of radiocarbon dating, 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. The intact internal stratigraphy of the Carolina bay sediments, as indicated by paleosols and pollen zones (e.g. Big Bay) refutes such arguments.
As discussed by Gaiser, radiocarbon dates reported from any Carolina bay are minimum dates for their formation. The radiocarbon dates only represent times during which organic matter accumulated and was preserved in Carolina bays. At other times, datable organic matter either might not have been preserved as sediment accumulated within them, or older organic matter might have been destroyed when the bays dried out. During times when the water table was below the bottom of a Carolina bay (e.g., possibly during glacial periods when sea level was 130 meters (400 ft) below present), organic matter could have been destroyed by oxidization and weathering. Also, during such times, eolian processes could have eroded any existing sediments at the bottom of Carolina bays. There are some who suggest that the oldest radiocarbon date from a Carolina bay only indicates the time when the water table rose high enough for a permanent lake or swamp to exist within it. This interpretation, however, may depend upon the nature of the overlying sediment. For example, eolian processes can bury and preserve organic matter, and thus the preservation of organic matter can occur independently of water table behavior.
The bays contain trees such as Nyssa sylvatica, bald cypress, pond cypress, sweet bay, loblolly bay, Persea, sweet gum, maple, magnolia, pond pine, and shrubs such as fetterbush, clethra, sumac, button bush, zenobia, and gallberry. Plants common in Carolina bays are Nymphaeaceae, sedges and various grasses. Several carnivorous plants inhabit Carolina bays, including bladderwort, butterwort, pitcher plant, and sundew.
Some bays have been greatly modified by human activities including farming, highway building, and construction of housing developments and . For example, Carvers Bay, a large bay in Georgetown County, South Carolina, was used as a practice range during World War II. It has been drained and is mostly used for forestry today. Others are used for vegetable or field agriculture with drainage. A study of bays located on the Delmarva peninsula estimated that 70% had been partially or fully converted to agriculture.
In South Carolina, Woods Bay, on the Sumter-Florence county line near Olanta, was designated a state park to preserve it as much as possible in its natural state. Also, 66 Bennett'
Ecological significance and biodiversity
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; Lake Waccamaw is an undrained example. Some bays are predominantly open water with large scattered pond cypress, while others are composed of thick, shrubby areas (), with vegetation growing on floating peat mats.
The bays are especially rich in biodiversity, including some rare species and/or endangered species. Species that thrive in the bays' include birds, such as , , , and other bird migration waterfowl, mammals such as deer, black bears, , , and opossums. Other residents include dragonflies, and green .
Bennett's Bay
Lisa Matthews Memorial Bay
Quaternary geologists and geomorphologists state that the features of the Carolina bays can be readily explained by known terrestrial processes and repeated modification by eolian and lacustrine processes. Also, Quaternary geologists and geomorphologists have found a correspondence in time between when 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 (Late Wisconsin) and 70,000 to 80,000 years BP (Early Wisconsin).
In addition, Quaternary geologists and geomorphologists have found that the orientations of the Carolina bays are consistent with the wind patterns that existed during the Wisconsin glaciation, as reconstructed from the orientations of parabolic dunes in river valleys. (2025). 9783030404987, Springer Publishing. ISBN 9783030404987 Within the Atlantic Coast Plain, the orientation of the long axes of Carolina bays and the inferred direction of movement of adjacent sand dunes, where present, are generally oblique to each other. In southern Georgia and northern Florida, the orientation is matched by an inferred west to east direction of movement of Pleistocene sand dunes.Markewich, H. W., and W. Markewich (1994) An overview of Pleistocene and Holocene inland dunes in Georgia and the Carolinas; morphology, distribution, age, and paleoclimate. Bulletin no. 206, United States Geological Survey, Reston, Virginia. Northward from northern Georgia to Virginia, the average inferred direction of movement of Pleistocene parabolic sand dunes systematically shifts along with the average orientation of the long axes of Carolina bays as to lie oblique to them. In the Delmarva Peninsula, the 112-degree shift in the average trend of the long axes also corresponds with a shift in the average inferred direction of movement of Pleistocene parabolic sand dunes such that their direction of movement is also oblique to the long axes, as is the case in the rest of the Atlantic Coastal Plain.
Some of the disfavored alternative hypotheses involve extraterrestrial events of some type. These hypotheses include meteorite impacts; shockwaves from a comet explosion; secondary impacts of glacial ice boulders ejected from a Younger Dryas impact in th Laurentide Ice Sheet; and speculative "cavitation" processes in a unproven, regional sandy, Mid-Pleistocene impact ejecta. These hypotheses are dismissed for a number of reasons including the wholesale lack of primary evidence for the extensive contemporary impact ejecta, impact processes, impactors, and suitable source impact crater for either sand or ice boulder ejecta.
Undrained depressions, circular to oval in shape and exhibiting a wide range of area and depth, are also a feature of the Gulf of Mexico coastal plain in Texas and southwest Louisiana. These depressions vary in size from in diameter. Within Harris County, Texas, raised rims, which are about high, partially enclose these depressions.Aronow, S., nda, A Digression on the origin of some anomalous undrained depressions mostly on the Pleistocene and Pliocene surfaces in the Gulf of Mexico PDF version, 48 KB Armand Bayou Watershed Working Group, The Texas Coastal Watershed Program, Houston Texas.Aronow, S., ndb, Geomorphology and surface geology of Harris County and Adjacent parts of Brazoria, Fort Bend, Liberty, Montgomery, and Waller Counties, Texas PDF version, 68 KB Armand Bayou Watershed Working Group, The Texas Coastal Watershed Program, Houston Texas.
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