Geomorphology and Geoarchaeology of Southern Mississippi (2004)

8/9/2019 Geomorphology and Geoarchaeology of Southern Mississippi (2004)

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A Review of theGeomorphology and Geoarchaeology

of Southern Mississippi

By Paul V. HeinrichLouisiana Geological Survey

Baton Rouge LouisianaUnedited Draft Manuscript (2004)

IntroductionIt has been long known that archaeological sites aren't randomly distributed over the

natural landscape. Rather, studies of the distribution of archaeological sites show that they

are either preferentially associated with specific landforms or concentrated adjacent to the

where the needed natural resources are located. In addition, the location of archaeological

sites determines the specific processes, both natural and cultural, involved in modifying the

cultural deposits that comprise them. As a result, the knowledge of the geomorphology of

an area can be used to predict, in very general terms, the abundance, types, and condition of

archaeological sites to be found in an area.

MethodologyFor this paper, a review was conducted of the literature published on the geology and

geomorphology of southern Mississippi, George, Hancock, Harrison, Jackson, Pearl River,

and Stone counties. In addition, to papers available in the peer-reviewed literature,

including journal articles and publications Mississippi Office of Geology, unpublished

theses, dissertations, and contract reports from various sources were acquired and

consulted. The Mississippi Mineral Resources Institute at the University of Mississippi in

University, Mississippi proved to be a significant source of unpublished contract reports

related to the geology of southern Mississippi.

One serious problem encountered in preparing this report was the lack of useful

mapping for the distribution of upland surfaces and terraces for southern Mississippi. The

only useful geologic mapping existed only for George County, Mississippi, as part of

Williams (1966) and for Hancock County in Pellegrin (1978). The official state geological

map of Mississippi, Bicker (1969), lacked the detail needed for compiling a geomorphic

map of southern Mississippi. The mapping of Brown et al. (1944), because of the lack of


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detailed topographic bases at the time it was created, proved to be badly flawed in its

depiction of the upland surfaces and terraces and unsuitable for compiling a useful

geomorphic map. The sketch maps illustrated in Otvos (1971, 1995, 1997) and other

publications of his proved too generalized for compilation.

Because of these problems, the general geomorphic map, Figure 1, showing the

distribution of terraces, surfaces, and other landforms within southern Mississippi was

created by compiling information from Williams (1966) for George County and Pellegrin

(1978) in Hancock County and mapping from digital data sources. Both 10 and 30 m

digital elevation models (DEMs) served as the primary base for mapping and compilation

of pre-existing maps. Both 10 and 30 m DEM data came from the Mississippi Automated

Resource Information Center (MARIS) and the National Cartography and Geospatial

Center (NCGC). In addition to the DEM data, the geologic mapping used 7.5-minutetopographic and digital orthophoto quadrangles and 15-minute topographic maps to drawn

boundaries and make interpretations. Digital files of individual 7.5-minute topographic and

digital orthophoto quadrangles were acquired from Mississippi Automated Resource

Information Center. The USDA Geospatial Gateway served as the source of NCGC 7.5-

minute topographic and digital orthophoto quadrangle county mosaics. The geomorphology

shown in Figure 1 largely came from the analysis and interpretation of this data.

Regional SettingSouthern Mississippi lies within the coastal plain that forms the northern margin of the

Gulf of Mexico. Within southern Mississippi, the coastal plain consists of 7 to 9 km (4.3 to

5.5 mi) of sediments that accumulated within the Gulf of Mexico over the last 165 million

years as the Gulf of Mexico has been infilled in by a variety of sediments. Over time, as the

result of both the accumulation of coastal plain sediments and a progressive drop in sea

level over the last 14 million years, the northern shore of the Gulf of Mexico has shifted

southward. As a result, geologically young sediments and landforms characterize southern

Mississippi. The surface geomorphology of southern Mississippi can be subdivided on the basis of landforms and the sediments underlying them into the Neogene Uplands, the

Pleistocene Coastal Plain, and the Holocene Coastal Plain.


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Neogene UplandsThe Neogene Uplands comprise the bulk of the landscape within the six counties that

comprise southern Mississippi (Figure 1). Most of the Neogene Uplands consists of rolling

hills that are dissected by deeply incised stream valleys and underlain by Neogene age

coastal plain strata. The Neogene Uplands include large area of flat-lying areas, upland

flats, within its otherwise rolling and hilly topography. The maximum elevation of the

Neogene Uplands increases westward from over 98 m (320 ft) in Gregory County to 113 m

(370 ft) in Stone County and 116 m (380 ft) in Pearl River County.

Ridge and Ravine TopographyRidge and ridge topography characterises the surface of most of the Neogene Uplands

of southern Mississippi. Ridge and ravine topography consists of a monotonous network of

steep-sided, ravine-like branching valleys and rounded intervening ridges and hills. Itconsists of narrow, rounded ridges less than 0.2 to 0.4 km (0.12 to .25 mi) wide and deep,

steep-sided ravines lacking significant floodplain development. The relief between the

crests of ridges and bottoms of adjacent ravines can be as much as 15 to 40 m (50 to 130

ft). The meximum elevation of these ridges gradually decrease gulfward.

Within the ridge and ravine topography, erosion has incompletely removed the pre-

existing constructional topography associated with the Citronelle Formation. Within ridge

and ravine topography, erosional processes associated with a humid climate has largely

produced an erosionally graded landscape, the ridge and ravine landscape of Hack (1960).

In ridge and ravine landscape, the courses of the local drainage networks follow zones of

structural or lithologic weakness within the underlying Neogene strata. In addition, the

relative resistance of strata to erosion and distance from the major trunk drainages

determined the relative relief of ridge crests and hill summits (Hack 1960).

Upland Flats The only remnants of the coastal plain that once formed the surface of the Citronelle

Formation consists of concordant summits along the major drainage divides and isolated

flat surfaces, which are called the "upland flats. These upland flats consist of relatively flatrolling surfaces, typically about 0.8 to 5 km (0.5 to 3 mi) wide forming the summits of

drainage divides. Upland flats are quite common within Georges County east of the

Pascagoula River valley. West of the Pascagoula River valley, they are very rare to

nonexistent with only few scattered examples largely found in central Stone County.


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Thousands of closed depressions characterize the otherwise flat and featureless surface

of the upland flats within southern Mississippi (Figures 2 and 3). These depressions range

in diameter from 45 to 780 m (150 to 2,600 ft) and range in depth from 0.9 to 12 m (3 to 40

ft). These depressions are generally wet, often containing miniature swamps, and rarely wet

enough to contain ponds. The interior of these depressions often contains swamp or forest


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topographic are often quite irregular in shape. These depressions are found on upland flats

within the Alabama and Mississippi coastal plains and along the Atlantic coastal plain,

where they are called "Carolina Bays" (Figure 4).

Brown et al. (1965) reported the presence of ridges of sand surrounding these

depressions. Later inspections of these landforms found that these ridges are absent from

these landforms. Otvos (1973) noted that the white rims seen on aerial photographs

consisted of a zone of leached, dry sand surrounding these depressions that sharply

contrasts with their highly vegetated and unplowed interiors on aerial photography.Brown et al. (1944), in part Harvey et al. (1965), and Otvos (1973, 1997) argued that

eolian processes created these enclosed depressions. Brown et al. (1944) regarded these

depressions as possibly being of recent origin having resulted from the removal of

vegetation by fire and subsequently excavated by wind. Otvos (1973, 1997) argued that the

eolian origin of these depressions is the most plausible explanation based on a generally

consistent orientation of their long axes and the lack of sufficient soluble minerals and

sediments in the underlying Neogene strata for the development of karst.

In contrast, Harvey et al. (1965) in part, Isphording and Flowers (1988), May and

Warne (1999), and Williams (1966) argued that these depression, along with similar

enclosed depressions found within the Atlantic Coastal Plain called "Carolina Bays," are

depressions related to removal of either iron, clays, aluminum, colloids, or other minerals

by dissolution from Neogene sediments. Isphording and Flowers (1988) demonstrated that


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the incongruent dissolution of kaolinite and gibbsite results in a 34-percent reduction in

volume that is capable of producing karst-like depressions. Their research refuted the

contention of Otvos (1973, 1997) that there is a lack of sufficient soluble minerals within

the Neogene sediments underlying the upland flats. Isphording and Flowers (1988) also

argued that this process is currently producing karst-like depression within the coastal

plain. May and Warne (1999) later argued that the Carolina Bays of the Atlantic coastal

plain and the enclosed depressions of the upland flats as having both been created by silica

karst processes during the Pleistocene. Finally, as Otvos (1981) argued that fractures have

controlled the orientation of drainage patterns within the study area, it can be argued that

the same regional fractures would have controlled ground water flow and the orientation of

the enclosed depressions. They demonstrated that the relatively flat upland flats are prime

locations for the development of silica-karst. At this time, Isphording and Flowers (1988)and May and Warne (1999) have offered the best explanation for the origin of the oval and

circular depressions within the upland flats.

Otvos (1973, 1997) suggested that enclosed depressions found within the upland flats

originated prior to the uplift and dissection of the original depositional, coastal plain

surfaces underlain by the Citronelle Formation. He argued that these depressions formed as

blowouts on Late Pliocene age floodplains that comprised part of the original Citronelle

coastal plain. However, Otvos (1973, 1997) failed to provide any credible arguments as to

how these depressions would have survived in recognizable and relatively pristine form

when other constructional landforms, natural levees, abandoned channels and courses,

beach ridges, sand dunes, and so forth, have been completely obliterated by surficial

processes. The fact, that all other recognizable constructional landforms have long been

obliterated indicates that these depressions are the result of relatively recent, if not ongoing,

modification of the upland flats, which is consistent with these depressions being silica-

karst.

Brown et al. (1944) reported the presence of other alleged eolian landforms and a

blanket of eolian sand covering the uplands within southern Mississippi. Specifically, they

reported to have found small sand dunes and elliptical depressions about 2,4 km (1.5 mi)

southwest of Agricola, Mississippi, in the SW quarter section of Sec.12, T.3S., R.6W.

However, later attempts to examine these dunes and depressions failed to find any evidence


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of their existence (Otvos 1973, 1997). Similarly, Otvos (1973) failed find any evidence of

any the layer of wind-blown sand noted by Brown et al. (1944). The layer eolian sand

noted by Brown et al. (1944) quite likely was a well-developed biomantle. In sandy coastal

plain sediments, biomantles can consist of a surficial sandy layer that has the appearance of

a distinct sedimentary layer of eolian origin that is separate from the underlying parent

material (Johnson 1990).

Subsurface UnitsTwo major stratigraphic units, the Pensacola Formation and the Citronelle Formation,

underlie the Neogene Uplands of southern Mississippi. The Citronelle formation, youngest

and uppermost of these units, underlies upland flats and the crests and summits of the ridge

and ravine topography. It overlies and separated from the Pensacola Formation by an

erosional unconformity, which exhibits a considerably amount of relief (Oivanki and Otvos

1994; Otvos 1973, 1994, 1997).

Pensacola Formation. The sediments comprising the Pensacola Formation, as defined

by Otvos (1994, 1997), are the oldest strata exposed within Southern Mississippi. It

consists of strata formerly subdivided into the Hattisburg Formation, Pascagoula Clay

(Formation), and Grahams Ferry Formation. As shown in Bicker (1969), the Pensacola

Formation directly underlies the surface of the lower and middle slopes of major stream

and river divides. It also, underlies the thin fluvial deposits that form the IntermediateTerraces. Within the Intermediate Terraces, erosion has removed these fluvial deposits and

the Pensacola Formation directly underlies its surface. Where it underlies the surface of

southern Mississippi, the landscape is typically gently rolling and characterized by clayey

soils and fine, dendritic, lace-like drainage patterns. The Pensacola Formation underlies

many swampy and poorly drained areas, which don't lie within the modern alluvial valleys

(Brown et al. 1944; Williams 1966).

The Pensacola Formation consists of 900 to 1500 m (3000 to 5000 ft) of dominantly

light and dark greenish gray and light to medium gray sandy mud, mud, and clay beds with

infrequent beds of fine- to medium-grained sand and gravelly sand interspersed throughout

them. Within terrestrial and deltaic facies, formerly mapped as the Hattisburg Formation,

beds of lignite and carbonaceous clay or mud commonly occur. The Pensacola Formation

consists of a complexly interfingering mixture of paralic - coastal plain, i.e. fluvial,


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backswamp, estuarine, and deltaic, and nearshore marine deposits (Oivanki and Otvos

1994; Otvos 1973, 1994, 1997).

The Pensacola Formation is sparingly fossiliferous. Locally, the fossils found

individual beds consist of the molds of bivalves, the shells of Mulinia lateralis and Rangia

cuneata , and brackish water foraminifera such as Ammonia beccarii and Elphidium spp .

The upper part of the Pensacola Formation, which lacks Rangia (Miorangia ) johnsoni and

was formerly designated as the "Graham Ferry Formation," is considered to be Lower

Pliocene in age. The underlying sediments containing Rangia (Miorangia ) johnsoni and

formerly designated as the "Pascagoula Clay," is regarded to be Upper Miocene in age

(Otvos 1973, 1994, 1997).

Citronelle Formation. Within southern Mississippi, the Citronelle Formation is the

youngest pre-Quaternary stratigraphic unit exposed within southern Mississippi. Itunderlies the upland flats and the upper slopes of the major drainage divides and interfluves

within southern Mississippi as shown in Bicker (1969).

The Citronelle formation consists predominantly of unconsolidated, poorly- to

moderately-sorted, silty sand, sand, and gravelly sand containing occasional thin beds of

fine-grained sediments. Typically, the colors of the coarse-grained sediments vary from

dark yellowish brown (10YR6/6), moderate red (5R4/6), moderate reddish orange

(10R6/6), to moderate reddish brown (10R4/6). Where affected by modern surface

weathering and pedogenesis, these reddish colors are altered to dark and light yellowish-

orange (10YR6/6 and 10YR7/6), moderate yellow (5Y7/6), and white. These colors reflect

the presence of films composed of mainly of hematite, gibbsite, and kaolinite that coat and

fill the spaces between sand grains. The thin kaolinitic clayey beds found within the

Citronelle Formation exhibit purple, pink, and light gray colors that are often characteristic

of the Citronelle Formation (Otvos 1973, 1995, 1997)

The Citronelle Formation rarely contains situ fossils. Typically, they consist of isolated

trunks of silicified wood and long external molds of root. At the Dees Pit within Vanleave,

Jackson County, Mississippi, a very rare, if not unique, peat lens and, possibly logjam,

yield identifiable pollen (Otvos 1973, 1995, 1997). The most abundant fossils found in the

Citronelle Formation consist of Paleozoic fossils, including brachiopods, bryozoans, corals

crinoids, trilobites, and gastropods, found within individual chert pebbles that occur


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abundantly within the Citronelle Formation. The original source of these fossils was

Paleozoic limestone within the region of the Nashville dome (Dockery 1995, 1996).

The minerals that create the reddish and reddish orange colors of the Citronelle

Formation demonstrate the highly weathered nature of these sediments. The hematite,

gibbsite, and kaolinite are indicative of intense lateritic weathering under tropical climates.

Another indication of deep weathering of these sediments, contemporaneous with their

deposition, is the presence of thick paleosols, fossil oxisols, within the Citronelle

Formation. These paleosols consist of several meter-thick beds of massive sandy sediments

containing rhizomorphic root molds and veined, marbled, and mottled by pedogenesis

(Otvos 1995, 1997).

Pleistocene Coastal PlainOnly the narrow edge of the Mississippi coastal plain consists of coast-parallel terraces

exhibiting any degree of preservation of their original depositional surfaces. Depending on

the degree of preservation of the depositional surfaces comprising them and the presence or

absence of constructional topography, these surfaces can be grouped into one of two groups

of terraces. The lowermost set of surfaces, having relatively undissected surfaces and

exhibiting constructional landforms are grouped into the Prairie Terraces. The second set of

terraces consists of deeply dissected surfaces lacking constructional landforms. They are

grouped into the Intermediate Terraces because of their intermediate position between the Neogene Uplands and the Prairie Terraces. Both sets of terraces are considered to be

constructional surfaces and to be underlain by Pleistocene sediments.

Intermediate TerracesLying intermediate in elevation between the dissected uplands and rare upland flats of

the Neogene Uplands and the coast-wise Prairie Terraces, are a series of discontinuous

coast-wise terrace surfaces (Figure 1). Similar terraces also are found intermediate in

elevation between the Neogene Uplands and Prairie Terraces within and floodplains of thePearl and Pascagoula rivers and their tributaries (Figure 1). Because of their fragmentary

nature and lack of detail research about them, it difficult, at this time, to either subdivide or

correlate them with any confidence. Therefore, they grouped into the Intermediate

Terraces. The Intermediate Terrace is equivalent to the "Low Terraces" of Brown et al.

(1944) and Williams (1966).


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West of the Pascagoula River within Jackson County, the Intermediate Terraces form a

narrow "V"-shaped terrace flanking, lying above the upper surface of the Prairie Terraces

and Neogene Uplands along the east side of the Pascagoula River valley and the west side

of the Escatwapa River valley (Figure 5). Within Jackson County about 2.9 km (1.8 mi)

south of Big Point, Mississippi, the apex of the "V" and southern end of this terrace lies on

the boundary between Sec. 3, T. 6S., R. 5W. and Sec. 34, T.5S., R. 5W. At Big Point, a 6 to

7.6 m (20 to 25 ft) high scarp occurs within this terrace indicating that it consists of

multiple surfaces of different ages.

Between the Pascagoula and Biloxi rivers within Jackson and Harrison counties, theIntermediate Terraces consists of pieces of a deeply dissected, coast-parallel terrace lying

between the Prairie Terraces and the Neogene Uplands (Figure 1). The southern edge of the

Intermediate Terraces consists largely of a well-defined scarp, called "Big Scarp" by Otvos

(1973, 1995, 1997), rises 4.6 to 6 m (15 to 20 ft) above the surface of the adjacent Prairie

Terraces. Otvos (1973, 1995, 1997) hypothesized that Big Scarp is a tectonic feature,


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possibly a fault-line scarp (Figure 6). However, subsurface structural data substantiating

this hypothesis has yet to be presented. Adjacent to Big Scarp, this stretch of the

Intermediate Terraces lies at elevations above 12 to 14 m (40 to 45 ft). Further north its

surface rise over 15 m (50 ft) in elevation. The only constructional topography evident

within this part of the Intermediate Terraces consists of large arcurate ridges of unknown

origin (Figure 5.).

Between the Biloxi River and Bay St. Louis with Harrison County, the Intermediate

Terraces consist of a series of relative narrow, less than 0.6 to 1.2 km (1 to 2 mi) wide,

terrace fragments lying between the Prairie Terraces and the Neogene Uplands (Figure 1).

The southern edges of these terraces consist of a well-defined, 4.6 to 6 m (15 to 20 ft) high

gulfward-facing scarp. Typically, these terraces range in elevation over 12 to 14 (40 to 45

ft) to 15 to 17 m (50 to 55 ft). New Hope, Mississippi lies on the westernmost of these

terraces. Between a tributary of Turkey Creek in Sec.13, T. 7S., R.12W. and Bay St. Louis,terraces of the Intermediate Terraces are largely absent, except for some very narrow and

almost unmappable surfaces, along the contact between the Prairie Terraces and Neogene

Uplands.

West to northwest of Bay St. Louis within Hancock and Pearl River counties, terrace

fragments belonging to the Intermediate Terraces occur between the Neogene Uplands and


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the upper surface of the Prairie Terraces (Figure 1). The terraces consist of deeply

dissected, gently sloping surfaces preserved within the interfluves separating

Hobololochitto Creek, East Hobololochitto Creek, Long Branch, their tributaries, and

tributaries of Jourdan River within central Hancock and southern Pearl River Counties.

They range in elevation from 15 to 26 m (50 to 85 ft) in east-central Hancock County to

about 36 to 43 m (120 to 140 ft) in west-southern Pearl River County. Well-defined scarps

separate these terrace surfaces from the adjacent Prairie Terraces and Neogene Upland.

The characteristics of the sediments underlying the Intermediate Terraces within

southern Mississippi are poorly known. Unlike either the strata underlying the Neogene

uplands and the Prairie Terraces, little specific research has been conducted about the

deposits underlying the Intermediate Terraces. Brown et al. (1944), Otvos (1973, 1997),

and Williams (1966) provided the only specific descriptions of the sediments underlying

the Intermediate Terraces. Otvos (1973, 1997) and Oiranki and Otvos (1994) informally

referred to the sediments underlying the "Low Terraces" as "Early Pleistocene Alluvium,"

Pre-Sangamon alluvial unit," and "earlier Pleistocene units."

Relatively coarse-grained fluvial sediments underlie the Intermediate Terraces found

along the Pascagoula River and its tributaries. These sediments consist mostly of "gray" to

either "tan" or "yellow" sand that locally contains granules and pebbles of quartz and

"brown" chert. The sand ranges in thickness from a maximum of 6 m (20 ft) to moretypically 2 m (6 ft) or less in thickness. Within many of the terraces along the Pascagoula

River and its tributaries, erosion has cut through these sediments underlying the

Intermediate Terraces and exposed underlying clayey Neogene sediments (Brown et

al.1944; Williams 1966).

The sediments underlying Big Ridge consist of well- to medium-sorted, medium-

grained, sometimes muddy sand. These sediments are of fluvial origin with brackish-water

and marine sediments being absent. They are very similar in appearance, lithology, and

color, to the sediments underlying the Prairie Terrace. Near outcrops of the Citronelle

Formation, they are indistinguishable in color from the Citronelle Formation (Otvos 1973,

1985).

The Lamey Pit, located within the NW 1/4. Sec. 34, T.6S., R.9W., in Jackson County,

Mississippi, exposes 6 to 7 m (20 to 23 ft) of poorly sorted, occasionally gravelly, silty to


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muddy fine sand that locally underlies Big Ridge. These sands exhibit parallel and cross-

laminations and are locally extensively burrowed. The sediments exposed in this burrow pit

also contain a few laminated clay beds and peaty clay lenses. These beds and lenses contain

finely disseminated organic matter and partly carbonized logjams composed of yellow pine

branches and cones. (Otvos 1973, 1985, 1997).

Pollen and other plant material recovered from the Lamey Pit are indicative of an

interglacial climate. The pollen spectra are indicative of an interglacial epoch containing

predominately pine and oak with significant amounts of tupelo and sweet gum. Within the

wood recovered, yellow pine predominates along with lesser amounts of oak, Carya , Ilex,

Liquidambar , Castanea , and Myrica . The pines cones belonging to spruce, slash, and,

possibly, pond were recovered from these sediments (Otvos 1997).

The age and origin of these surfaces remain uncertain. Their position between the Neogene Uplands, which are underlain by late Pliocene sediments of the Citronelle

Formation and the Late Pleistocene Prairie Terraces, indicates that these surfaces and the

sediments underlying them either are early Pleistocene, middle Pleistocene, or combination

of these in age. At this time, as summarized by Otvos (1973, 1995, 1997), it appears that

these terraces are remnants of former coastal plain underlain by fluvial sediments.

The exact ages of the surfaces of the Intermediate Terraces and the deposits

comprising them remains uncertain. So far, neither paleontological nor other data useful in

determining the specific ages of either the surfaces or sediments comprising the

Intermediate Terraces has been recovered from the Mississippi coastal plain. At of this

time, it is uncertain whether either these surfaces or associated sediments date from the

same period of time. The best that can be inferred is that they post-date the Late Pliocene

Citronelle Formation and postdate the Late Pleistocene Prairie Terraces.

Prairie TerracesWithin southern Mississippi, the Prairie Terraces is the lowest coast-parallel terrace,

which comprises the terrestrial coastal plain lying adjacent to the Mississippi shoreline of

the Gulf of Mexico (Figure 1). It either forms the Gulf of Mexico shoreline or the

southernmost high ground lying adjacent to low-lying Holocene marshes and beaches. The

Prairie Terraces, unlike the older Intermediate Terraces, often exhibits relict constructional

topography, i.e. abandoned beach ridges and river channels and meander loops. The Prairie

Terraces are considerably less dissected than adjacent fragments of the Intermediate


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Terraces. The coast-parallel portion of the Prairie Terraces typically ranges in elevation

from 1.5 (5 ft) to over 7.6 m (25 ft). Within this range of elevations, multiple surfaces can

be recognized within the Prairie Terraces. The width of the Prairie Terraces varies greatly

along the extent of the Mississippi coastal plain.

West of the Pascagoula River within Jackson County, the Prairie Terraces consists of

two distinct surfaces that occupy a strip of the Mississippi coastal plain that is about 13 km

(8 mi) wide at its narrowest point between the valleys of the Pascagoula and Escatawpa

rivers (Figure 1). Surrounding this remnant of the upper surface is a recognizable lower

surface that extends from Holocene coastal marsh and the edge of the upper surface

northward to the edge of the Intermediate Terraces. It ranges in elevation from about sea

level to just over 1.5 m (5 ft) above sea level at its southern edge to about 4.6 to 5.8 m (15

to 19 ft) above sea level at its northern edge within Sec. 13 and 18, T. 6S., R. 5W. about 10km (6.2 mi) inland along the eastern edge of the Pascagoula River valley. An outlier of

highest surface of the Prairie Terraces consists of an isolated rectangular outlier that is

about 5.6 to 7.2 km (3.5 to 4.5 mi) wide in an east-west direction and about 8 km (5 mi)

wide in a north-south direction and lies adjacent to the modern shoreline. Pascagoula and

Moss Point, Mississippi lie upon the upper surface. The upper surface has an elevation of 3

to 5 m (10 to 17 ft).

Further north, along the upper surface of the Prairie Terraces forms an extensive "V"-

shaped terrace (Figure 1). One leg of the "V" consist of a prominent terrace lying along the

east side of the Pascagoula River valley, on which the towns of Wade and Three Rivers,

Mississippi, and Black Creek Swamp and lie. This leg of the upper surface extends

northward across the Jackson - George County lie where it is cut out by the valley wall of

Pascagoula River valley against the Intermediate Terraces just north of Garrnet Branch and

just south of Basin, Mississippi. The apex and southernmost end of the "V" is located about

3.2 km (2 mi) east of Helena, Mississippi within Sec. 25 and 26, T. 7S., R. 5W. Within

these sections, a well-defined 3 to 4.5 m (10 to15 ft) high scarp separates the lower and

upper surfaces. The other leg of this "V"-shaped terrace of the upper surface extends along

west side of the Escatawpa River northeastward into George County (Figure 1). As along

the Pascagoula River, extensive swamps, i.e. Island and Redoak swamps lie on the upper

surface at the base of the scrap separating it from the Intermediate Terraces. Isolated


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fragments of the upper surface occur further upstream along the valley walls of the

Pascagoula and Escatawpa rivers and their tributaries.

Within eastern Jackson County, the lower surface of the Prairie Terraces exhibits well-

preserved relict constructional landforms. The most prominent of these landforms are

abandoned meander belts of the Pascagoula River that has been cut in two segments by the

Escatawpa River and its valley (Gazzier 1977; Saucier 1977). Lying north of the Escatawpa

River, a well-defined northwest-southeast trending segment of a relict Pascagoula River

meander belt is illustrated by 7.5-minute topographic maps and aerial photography. This

meander belt extends from Sec. 14 and 23, T. 6S., R. 6W., at Col Town, Mississippi; past

Helena, Mississippi; to Sec.3 and 9, T. 7S., R. 5W. (Figure 7). Southeast of the Escatawpa

River, Bayou Cumbest and Middle Bayou occupy the relict courses of abandoned

Pascagoula River meander belts (figure 8). Between the relict river course occupied by


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Bayou Cumbest and the upper Prairie surface, Gazzier (1977) has mapped two sets of low,

linear ridges on the lower surface interpreted to be relict beach ridges.Between the Pascagoula River and a north-south line formed by US Highway 57 and

Old Fort Bayou within Jackson County, a single slightly narrower strip of the Prairie

Terraces forms the southern edge of the Mississippi coastal plain (Figure 1). This strip of

the Prairie Terraces extends about 11 km (7 mi) inland from the shore of the Gulf of

Mexico and consists also of upper and lower surfaces. Within this strip, the lower surface

consists of a fragment of the Gulfport strandplain about 3.7 km (6 mi) long and 0.6 to 0.9

km (1 to 1.5 mi) wide that lies south of Graveline and Simmons bayous. It lies at an

elevation typically ranging from 3.6 to 5.2 m (12 to 17 ft) to over 6 m (20 ft). As discussed

by (Oivanki and Otvos 1994), this segment of the Gulfport strandplain exhibits well-

developed beach ridge and swale topography (Figure 9). North of Graveline and Simmons

bayous, the remainder of this strip of the Prairie Terraces consists of an upper surface that


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extends northward to the highly dissected southern edge of the Intermediate. The upper

surface rises northward from the lower surface and the Gulf of Mexico shoreline fromabout 5.2 to 6.4 m (17 to 21 ft) in elevation to over 6 to 7.6 m (20 to 25 ft) in elevation at

the edge of the Intermediate Terraces. This segment of the upper surface exhibits

prominent linear and arcurate ridges that are over 7.6 to 9.1 m (25 to 30 ft) in elevation

(Figure 10). The origin of these ridges remains undetermined, including why two of these

ridges are aligned with the prominent scarp that forms the southern edge of Big Ridge.

Between a north-south line formed by US Highway 57 and Old Fort Bayou and Bay

St. Louis within Jackson and Harrison counties, the Prairie Terraces consists of narrow

strips of Prairie Terraces. One of these consists of a strip about 0.3 to 2.9 km (0.5 to 1.8 mi)

wide between the southern edge of the Intermediate Terraces, locally called "Big Ridge,"

and Back Bay of Biloxi. The easternmost edge of this strip appears to be a continuation of

the upper surface at an elevation just above 6 to 7.6 m (20 to 25 ft). Just east of Bayou

Porteaux within Sec. 13 and 14, T. 7S., R.9W., a short northwest-southeast scarp separates


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this upper surface from the lower surface, which comprises the rest of this strip at

elevations ranging from under 3 m (10 ft) to over 6 m (20 ft). Lying between the Back Bay

of Biloxi and the Gulf of Mexico, Biloxi, Mississippi, and Keesler Airforce Base lies on

another east-west strip of the Prairie Terraces consisting of a segment of the Gulfport

strandplain. This strip exhibits well-defined beach ridge and swale topography

characteristic of strandplains. It ranges in elevation from just under 3 m (10 ft) to ridges

with crests over 9 m (30 ft). A long strip of the Prairie Terraces lies between the north bank

of Tchoutacabouffa River and the southern edge of dissected remnants of the Intermediate

Terraces and the Neogene Uplands.

A narrow stretch of the Prairie Terraces lies between the west end of Back Bay of

Biloxi and Bay St. Louis (figure 1). Except for a small fragment in the Johnson Bayou area

and strip adjacent to and including the Gulfport strandplain, this stretch of the PrairieTerraces appears to consists largely of its upper surface lying at elevations over 7.6 to 9 m

(25 to 30 ft). A scarp separating the upper and lower surfaces can be seen in Sec.17 and 18,

T. 7S., R. 12 W.

West of Bay St. Louis and within Hancock and Pearl River counties, the landward

edge of the Prairie Terraces curves towards the northwest, locally expanding its width

greatly, and eventually merges with the valley wall of the Pearl River valley (Figure 1).

This part of the Prairie Terraces has been subdivided into three major regions by Pellegrin

(1978), the "Prairie Surface," "Texas Flats," and "Devil's Swamp." The "Prairie Surface"

and "Texas Flats" are regarded to be part of the upper surface and "Devil's Swamp" is

regarded to be part of the lower surface recognized elsewhere within the Mississippi coastal

plain.

Within Hancock County, the "Prairie Surface" and "Texas Flats" of Pellegrin (1978)

comprise an upper surface that forms part of the Prairie Terraces. This surface consists of a

moderately flat terrain, which is dissected at its southern edge. It ranges in elevation from

about 6 m (20 ft) at its southern edge to elevations over 15 m (50 ft) within northern

Hancock County. The southern edge of the upper surface, in places, exhibits a distinct with

a relief of about 3 m (10 ft). This scrap is best developed within Sec. 1, T. 8S., R.16W.


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(Figure 11). Within the area he mapped as the "Texas Flats," Pellegrin (1978) has

illustrated rectilinear drainage patterns, he interpreted to be poorly preserved, relict beach

ridges a Pleistocene strandplain system. The origin of these features remains uncertain. An

excellent example of some of these possible relict beach ridges can be seen in Sec.17, 19,

and 20, T. 7S., R.15W.

The lower surface of the Prairie Terraces west of St. Louis Bay consists of a large area

mapped by Pellegrin (1978) as "Devil's Swamp." It is a flat poorly drained lowland that is

exhibits relict constructional landforms such as abandoned relict river channels and courses

and low arcurate to linear ridges. One of these relict river channels can be seen due west of

the Stennis Space Center (Figure 11). As also seen in Figure 11, a linear scarp offsets the


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point bar surfaces of some of these channels, which is possibly a fault-line scarp. Other

relict landforms present within the Devils Swamp area are four low, sandy ridges, the

Westonia, Logtown, Port Facility, and Bay St. Louis ridges, mapped and described by

Pellegrin (1978). The Port Facility and Bay St. Louis ridges are parts of the Gulfport

strandplain.

The sediments underlying the surfaces of the Prairie Terraces have been subdivided in

a number of ways. The first of the two current classification systems, which is used by

ongoing mapping within adjacent Louisiana, designates these sediments as the Hammond

Alloformation within Louisiana. The final methodology for classifying these sediments,

which is used by recent research within Mississippi, subdivided the deposits underlying the

Prairie Terraces on the basis of lithology while using their fossil content as a relatively

quick way of identifying these specific subdivisions. As practiced by Otvos (1975, 1987,1988b, 1991a, 1991b, 1992, 1995, 1997; Otvos and Howat 1992), the sediments underlying

the Prairie Terraces on the basis of composition were subdivided into the Biloxi, Gulfport,

and Prairie formations (Figure 1).

The Biloxi Formation. The Biloxi Formation of Otvos (1975) consists of fossiliferous,

light-gray, bluish gray, muddy fine sand, clayey fine sand, and sandy mud with lessor

amounts of mud and clay. The dominant colors found in these sediments are from medium

bluish gray, light gray, medium greenish gray, and dark greenish gray. The sediments of

the Bilox Formation overlie Neogene strata or sediments of the Prairie Formation. Inland,

the Biloxi Formation interfingers with the Prairie Formation of Otvos (1975, 1991a) and, in

places, has been deeply eroded by fluvial scours and channels infilled with the Prairie

Formation (Figure 12). The sediments of either the Gulfport or Prairie formation overlie it.

The Biloxi Formation grades into and interfingers with the sediments comprising the

Gulfport Formation. The Biloxi Formation typically ranges in thickness from 4.5 to 10.5 m

(15 to 35 ft). Locally, it has a maximum thickness of 36 m (119 ft) (Otvos 1973, 1995,

1997; Otvos and Howat 1992).


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The Biloxi Formation is fossiliferous. In cores and other samples recovered from

some, but not all, borings, the Biloxi formation contains a rich fossil fauna. The fauna

consists of a large diversity of gastropod, pelecypod, and foraminifera species, as well as a

number of species of coelenterates, bryozoans, annelids, and ostracods. The different

assemblages of fossils are indicative of depositional environments for parts of the Biloxi

Formation ranging from marine continental shelf and nearshore to brackish water estuarine

environments. The fossil faunas and amino acid ratios derived from individual fossils are

indicative of a Sangamonian age for the Biloxi formation (Otvos 1995, 1997; Otvos and

Howat 1992).

Gulfport Formation. The Gulfport Formation consists of sand that underlies the

discontinuous and partially buried strandplain ridges exhibited by the Prairie Terraces

(Figure 13). It consists of medium- to fine-grained, moderately to very well sorted sand andlessor amounts of more poorly sorted silty sand. The moderately to very well sorted sand

exhibits horizontal to low-angle cross-laminations in outcrop. The oxidized sands of the

Gulfport Formation are light orange-yellow in color as the result pedogenic and diagenetic

limonite. Beds of dark-brown to black, humate-impregnated sands outcrop in exposures

along East Belle Fountaine Beach, Harrison County. Beneath the strandplain ridges, the


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Gulfport Formation is up to 21 m (69 ft) thick. It grades laterally into the Biloxi Formation

(Figure 13). It is largely devoid of fossils, except for Ophiomorpha trace fossils and the

molds of molluscan bivalves. The Gulfport Formation consists of beach, dune, and

shoreface sand, which comprise the Gulfport strandplain (Otvos 1973, 1995, 1997; Oivanki

and Otvos 1994).

Prairie Formation. The Prairie Formation consists of clayey, muddy, and silty fine

sands. Where exposed in borrow pits and banks of canals, these sands commonly festoon

cross-bedding and types of cross stratification and channels locally filled with gravelly

sands. At depth, its sediments are yellowish gray, greenish gray, and gray in color. Near the

surface, these sediments are very pale orange, pale yellowish brown, and medium

yellowish orange in color because of surface weathering. Where these sediments have been


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derived from the erosion of the Citronelle Formation, their color resembles the colors of the

Citronelle Formation. Typically, the Prairie Formation is 6 to 18 m (20 to 40 ft) thick with

maximum thickness of 21 to 24 m (70 to 80 ft). Gulfward, it interfingers with and locally

fills channels cut into the Biloxi Formation (Figures 12 and 13). Plant fossils have been

recovered from rare peaty lenses and one cheek tooth of a Pleistocene horse, Equus cf.

occidentalis or Equus cf. complicates , have been found in the Prairie Formation. Pine and,

to a lesser extent, oak pollen has been recovered from the peaty lenses (Otvos (1973, 1995,

1997; Otvos and Howat 1992).

Otvos (1997) argued that the of the Prairie Terraces were created and the sediments

comprising them accumulated during a high stand of sea level during the last Interglacial

epoch, the Sangamonian Stage about 75,000 to 125,000 years ago. The assignment is based

upon calcareous microfossils found recovered from Biloxi Formation found in MississippiSound Core S-2 of Drillhole no.2. Also, Amino acid D/L ratios from Chione spp. and

Anadra spp. shells from the Biloxi Formation and correlative units within Mississippi,

northewest Florida, and Texas correspond to calculated ratios for the Sangamonian Stage

(Otvos and Howard 1996). The presence of upper and lower surfaces, specifically within

Jackson County, demonstrates that the Prairie Terraces is a composite surface composed of

sediments deposited during at least two sea level cycles contrary to the interpretation of it

having been created during a single sea level cycle as argued by Otvos (1995, 1997).

Regardless, the surfaces of the Prairie Terraces and sediments comprising them predate the

human occupation of southern Mississippi

Deweyville TerracesWithin southern Mississippi, Deweyville Terraces are present within both the Pearl

and Pascagoula Rivers. Within the Pascagoula River valley, the surfaces of the Deweyville

Terraces lie largely buried by younger Holocene Fluvial deposits. Typically, only by

oversize meander bights cut into the eastern valley wall of the Pascagoula River valley

indicate the presence of the Deweyville Terraces. For example, such large meander bights

can seen on 7.5-minute topographic mapping north, west, and south of Coll Town,

Mississippi, within Sec. 14, 26, and 43, T. 6S., R. 6W. Further north, partially buried parts

of the Deweyville Terraces, i.e. Straw Island and Honey Island, can be discerned within the

Pascagoula River floodplain on 7.5- an 15-minute mapping within and north of Sec. 9, 10,


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15, and 16, T. 5S., R. 6W. Also, Black Creek, Files Pond, and John Goff Slough appear to

occupy shallowly buried Deweyville Terrace channels with Sec. 28, 31, 32, and 41, T. 4S.,

T.6W. Because Holocene fluvial deposits have buried the Deweyville Terraces in these

areas, they are largely mapped as Holocene floodplain. However, within these areas, the

Deweyville Terraces potentially occurs close enough to the surface where surface

excavations might disturb the surfaces that comprise it and any cultural deposits lying on

top of them.

As mapped by Pearson et al. (1986) various surfaces of the Deweyville Terraces occur

along either side of the Pearl River valley (Figures14 and 15). Only the largest remnants of

such surfaces could be shown in Figure 1. The largest of exposed Deweyville Terraces

consist of a north-south strip lying along the eastern edge of the Pearl River valley between

McGehee Creek in Sec. 7 and 9, T.5S., R.18W. and the Pearl River at Walkiah Bluff inSec. 19, 28, and 19, T.5S., R.18W. Within this strip, the Deweyville Terraces consists of

multiple surfaces ranging in elevation from 14 to 17 m (45 to 55 ft). As in the Pascagoula

River valley, oversize meander bights cut into its valley walls demonstrate the presence of

buried Deweyville Terraces within the Pearl River valley.

Within the northwestern Gulf of Mexico coastal plain, unconformity-bounded fluvial

deposits of the Deweyville Formation, Deweyville Alloformation within Louisiana,

underlie the Deweyville Terraces. The sediments of the Deweyville Formation typically

consist of coarse-grained channel and point bar deposits, mostly gray sand and gravelly

sand, covered by relatively thin, sometimes absent, fine-grained, gray sandy to silty clay,

overbank sediments. These sediments are intermediate in stratigraphic position, age, and

often elevation between the much more clayey sediments underlying the Prairie Terrace

and Holocene floodplain. Erosional contacts separate the sediments of the Deweyville from

the older sediments of the Prairie Formation and younger sediments that underlie the

Holocene floodplain (Bernard 1950; Gagliano and Thom 1967; Pearson et al. 1986). The

Deweyville Terrace is often the favored locations for sand and gravel mining because the

coarse-grained, gravelly nature of its sediments and the relatively thin, often absent, clayey

layer of overbank sediments, which cover it.


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The terraces of the Deweyville formation within southern Mississippi exhibit the

distinctive appearance, i.e. ridge and swale topography and abandoned channels and

courses, found associated with it elsewhere within the northwestern Gulf of Mexico coastal

plain. The considerably larger radii of the ridge and swale topography and meander loops

of the abandoned channels, which greatly exceed those of adjacent segments of modern

channels and courses, give the terraces of the Deweyville Formation their distinctive

appearance. In addition, the width of the abandoned channels and courses noticeably

exceed the widths of the abandoned and active channels and courses found within the

Holocene floodplains of the modern rivers, with which these terraces are associated

(Bernard 1950; Gagliano and Thom 1967; Pearson et al. 1986). Currently, the Deweyville

Formation and its associated terraces are regarded as having been deposited during at three

distinct periods, about 30,000 to 35,000, 40,000 to 41,000 and 52,000 years ago. Thesedates came from the optically stimulated luminescence dating of deposits of the Deweyville

Formation exposed within the valley of the lower Nueces River within Texas as reported

by Durbin et al. (1997).

The Deweyville Terraces and the sediments underlying apparently represent the

accumulation of predominately coarse-grained sediments and the aggradation of

floodplains of coastal rivers during periodic sea level highstands during the last glacial

stage, the Wisconsinan Stage. As a result, the Deweyville Terraces and sediments

comprising them predate the human occupation of southern Mississippi. In addition, the

deltas associated with these terraces lie submerged offshore beneath the surface of the

modern Gulf of Mexico (Durbin et al. 1997; Pearson et al. 1986).

Holocene Coastal PlainThe third major geomorphic subdivision of southern Mississippi is the Holocene

Coastal Plain. This subdivision consists of active geomorphic surfaces associated that are

the sites of ongoing accumulation of sediments and modification by fluvial and coastal

processes. Within southern Mississippi, the major subdivisions of the Holocene Coastal

Plain are the Pascagoula alluvial valley, Pearl River alluvial valley, and the Holocene

marshes and beaches.


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Pascagoula Alluvial ValleyWithin southern Mississippi, the Pascagoula alluvial valley consists of three major

segments. First, from Mississippi Sound to about 11 km (7 mi) north of it, the tidal delta of

the Pascagoula River occupies a 5 to 6.4 km (3 to 4 mi) wide segment of this valley. Thetidal delta is characterized by anastomosing river and tidal channel s and large lakes and

saline marsh within the southern 4 km (2.5 mi) edge of its delta and brackish marsh within

the remainder of it. Second, the Pascagoula River alluvial valley from the Pascagoula delta

to about 11 km (7 mi) north of it to the north end of Big Swamp consists of floodplain

composed of freshwater swamp, large lakes, and anastomosing channels. North of Big

Swamp, a single meandering channel with natural levees surrounded by backswamp

occupies the Pascagoula alluvial valley.

Little if anything has been published about the sediments that underlie the deltaic and

floodplain of the Pascagoula valley. A substantial amount of subsurface data exists in the

form of logs foundation borings, geophysical and descriptive logs of water wells, and other

subsurface data. However, none of this data has been compiled as part of a comprehensive

study of these sediments. Therefore, the character of these sediments remains largely

unknown.

Models of incised valleys filled by rising sea level predict that significant aggradation

of the floodplain occurred as a result of late Pleistocene and early and middle Holocene sealevel rise. Thus, there is significant potential for the presence of relatively thick Holocene

deposits underlying the floodplain of the lower and central segments of the Pascagoula

valley within southern Mississippi. Very likely significant aggradation of valley floor has

occurred during Holocene and Late Pleistocene sea level rise within of the stretch of the

Pascagoula valley characterized by anastomosing channels and its delta. Nothing is known

about the internal structure and age of the alluvial fans that lies along the valley wall of the

Pascagoula valley.

Pearl River Alluvial ValleyThe Pearl River Valley progressively narrows northward. At its mouth, the Pearl River

valley ranges in width from 10 to 11 km (6 to 7 mi) in width. Further north it rapidly

narrows in width to about 6.4 to 8 km (4 to 5 mi) and width and eventually about 5 km (3

mi) in width within the northern Pearl River County. Southward of its junction with Bouge


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Chitto and down to its floodplain, the floodplain of the Pearl River is characterized by a

swampy floodplain occupied by multiple anastomosing channels. North of its junction with

Bouge Chitto, the Pearl River exhibits a well-defined meandering channel with minor

crevasse distributary extending into the floodplain.

A potentially important feature of the Pearl River valley is a series of well-developed

alluvial fans that occur along its eastern valley wall within Northwest Pearl River County

(Figure 1). A series of large alluvial fans lie along the valley wall between irregular sec 37

and 38, T. 1S., R.17W. and Sec. 11 and 12, T. 3S., R. 18W. Some of these alluvial fans are

as wide as 0.6 to 1.2 km (1 to 2 mi). A series of three smaller alluvial fans occur along the

valley wall of the Pearl River between Sec 15, T. 3S., R.18W. and Sec. 10 and 15, T. 4S.,

R. 18W.

As in case of the Pascagoula River valley, little if anything has been published aboutthe sediments that underlie the deltaic and floodplain of the Pearl River valley. Although a

substantial amount of subsurface data exists in the form of logs foundation borings,

geophysical and descriptive logs of water wells, and other subsurface data, none of this data

has been compiled as part of a comprehensive study of these sediments. Therefore, the

character of these sediments remains largely unknown.

Judging by models of incised valleys filled by rising sea level, it is expected that

significant aggradation of the floodplain occurred during late Pleistocene and early and

middle Holocene sea level rise. As a result, there is significant potential for the presence of

relatively thick Holocene deposits underlying the lower and central segments of the Pearl

River floodplain characterized by anastomosing channels and its deltas. Nothing is known

about the internal structure and age of the alluvial fans that lies along the valley wall of the

Pearl River valley. Judging from the geologic history of alluvial fans in other fluvial

valleys, they have a high potential for containing thick late Pleistocene and Holocene

sediments.

Holocene Marshes and Beaches Within southern Mississippi, the Holocene coastal plain consists largely very thin band

of modern beach deposits that are typically less than 100 m (330 ft) wide and

discontinuous and wider stretches of coastal marsh. One major stretch of coastal marsh lies

east of the mouth of the Pascagoula River delta within Hancock County east of Pascagoula,


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Mississippi, and northwest Orange, Mississippi, and Pecan, Mississippi. This strip consists

of permanently flooded saline coastal marsh that is about 3 to 4 km (2 to 2.5 mi) wide and

lies either at or slightly below sea level. This marsh has an irregular gulfward edge with a

noticeable peninsula along the shoreline along the axis of Crooked Bayou and ends in a

headland that forms South Rigolet Island (Gazzier 1977). The marsh comprising this

peninsula clearly overlies an alluvial ridge of a relict Pleistocene meander belt associated

with Bayou Cumbest.

The second major stretch of Holocene coastal plain comprises parts of Belle Fountaine

Point along the south shore of Harrison County. The coastal plain, about one km (0.6 mi)

wide at its maximum, consists of shoreline beach ridges and saline marsh lying between

them and a segment of the relict Gulfport strandplain. A thin strip of brackish and saline

marshes also fills and incised valley, occupied by Graveline and Simmons bayous, lying between the Gulfport strandplain segment and undifferentiated Prairie Terrace. This strip of

marsh extends westward to Marsh Point where it comprises the western end of Belle

Fountaine (Oivanki and Otvos 1994).

Between Belle Fountaine, past Bay St. Louis, and Clermont Harbor, Mississippi, in

Hancock County, the shore of the Gulf of Mexico lacks any significant Holocene coastal

plain development, except for very narrow beach deposits. Instead, the Holocene coastal

plain consists of largely brackish marshes found within the partially flooded incised valleys

of minor coastal streams, i.e. Biloxi, Tchoutacabouffa , and Wolf rivers, and along the

edges of incised valleys completely inundated to form bays, i.e. Bay St. Louis and Back

Bay of Biloxi.

The third and final major stretch of Holocene coastal plain, called the "South Hancock

Relict Island and Marsh Complex," by Otvos (1995, 1997), comprises the western coast of

Hancock County (Figures 1 and 16) . This "complex" lies southwest of Clermont Harbor,

Mississippi, and south of Ansley, Mississippi, and extends to the southwest where it

merges with the Pearl River delta. It varies in width from 3 to 5 km (2 to 3 mi). This stretch

of Holocene coastal plain consists of three linear beach ridge trends, i.e. Magnolia Ridge,

Campbell Island, and Point Clear Island surrounded by saline and brackish marsh.

Magnolia Ridge is a 2 to 4 m (7 to 14 ft) high beach ridge that originally formed as


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mainline beach ridge. Shell middens on these ridges dated the occupation of these ridges

and utilization of these marshes from 2,900 to 2,190 years ago (Otvos 1995, 1997).

Little information has been either collected or compiled concerning the sediments that

underlie the Holocene coastal plain. At this time published data exists only for the

Holocene coastal plain associated with the Belle Fountaine area and the South Hancock

Relict Island and Marsh Complex.

Within the Belle Fountaine area, the deposits underlying the Holocene coastal plain are

relatively thin marsh and beach deposits. These sediments vary in composition from

organic-rich, very poorly sorted, fine-grained sand and muddy, medium-grained tidal

channel sand and dark greenish-gray, very soft marsh mud. Depending on the relief of the

pre-existing topography, including depth of incised valleys, flooded by Late Holocene sea

level rise, these sediments can be over 6.7 m (22 ft) thick. The Holocene coastal plainforming the tip of Belle Fountaine point consist of barrier sands. These sediments represent

late Holocene accumulation of sediments in response to sea level rise (Oivanki and Otvos

1994).


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A thicker wedge of sediments underlie comprise the South Hancock Relict Island and

Marsh Complex. These sediments consist of a wedge of sediments as much as 13 m (43 ft)

thick that thin landward and pinch-out and end against the older Pleistocene sediments

beneath Magnolia Ridge. They consist of thin marsh deposits underlying "muddy

nearshore" sediments that, in term overlie "open marine" sediments. The open marine

sediments lie upon the surface that was the former coastal plain during late Pleistocene to

middle Holocene epochs (Otvos 1995, 1997).

The history of the South Hancock Relict Island and Marsh Complex started with

global sea level rise during the Holocene, which submerged this former coastal plain now

buried by its sediments. During the middle Holocene, Magnolia Ridge formed as a beach

marking the greatest landward advance of the Gulf of Mexico shoreline. After sea level had

stabilized, the accumulation of, at first, open marine and, later, muddy nearshore sediments built the South Hancock Relict Island and Marsh Complex. However, over the last several

hundred to thousand years, the South Hancock Relict Island and Marsh Complex has been

subject to erosion that has greatly reduced its the area it covers (Otvos 1995, 1997).

GeoarchaeologyAs illustrated by the preceding discussion, the geomorphic regions present within

southern Mississippi differ greatly in their geology, geologic history, geomorphology,

landforms, and geomorphic processes. As a result, there exist great differences in wherearchaeological sites might be found in these regions and the processes affecting their

preservation.

Neogene UplandsThere has been few if any comprehensive studies of the distribution of archaeological

sites within southern Mississippi that can be used as a guide for evaluating the possibly

distribution of archaeological sites within the Neogene Uplands. Detailed analysis of

archaeological surveys that covered a significant area of similar uplands within the FortPolk Military Reservation South-central Louisiana provided a general guide as to the

possible distribution of sites. Within the Neogene Uplands of South-central Louisiana,

Anderson and Smith (2003) noted that distance to mapped water was the important

predictor of site location. For example, studies of site location versus distance from water


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features, i.e. the 1988 and 1995 Fort Polk predictive models, found that the vast majority of

sites, 90 to 93 percent, lay within 200 m (60 ft) of either a stream or, where present, edge of

a floodplain. In addition, Anderson and Smith (2003) observed that within this interval,

archaeological sites were virtually absent within the interval from the edge of either the

floodplain or stream to about 50 m (154 ft) from it. Willingham and Phillips (1987) found a

similar distribution of sites within the forested Neogene Uplands of the Kisatchie National

Forest near Alexandria, Louisiana. Anderson and Smith (2003) also found that sites lacking

diagnostic artifacts tended to occur farther away from mapped water features than sites

containing diagnostic artifacts.

Another important limiting variable noted by Anderson and Smith (2003) and

Willingham and Phillips (1987) was the elevation of the land above either the stream or,

where present, edge of floodplain. They found that the vast majority of sites, i.e. about 90 percent, occurred within a strip of land lying between 3 to 12 m (10 to 40 ft) about the level

of the nearest water or floodplain margin. Very few prehistoric archaeological sites were

located above 18 m (60 ft) in elevation above the level of the nearest water or floodplain

margin (Anderson and Smith 2003).

Contrary to conventional archaeological wisdom, Anderson and Smith (2003) found a

lack of any pronounced correlation between landforms and the location of archaeological

sites within the Fort Polk Neogene Uplands. Although, archaeologists have presumed that

prehistoric Native Americans would preferred either the noseslopes or crests of ridges, they

noted no detectable preference for sites to be located at these locations. Similarly, because

of their distance from water, the level parts of the Fort Polk landscape, in fact, contained

fewer archaeological sites relative to their area found within the surveyed parts of Fort

Polk. The only topographical preference that Anderson and Smith (2003) noted for the

location of prehistoric archaeological sites were high areas, i.e. ridge crests and terrace

edges adjacent to streams or floodplains.

The relative stability of the surface of the Neogene Uplands over the period of

prehistoric human occupation implies that a relatively complete archaeological record

should be preserved within it. However, within the ridge and ravine topography, slope

processes would have acted to dislocate and disperse cultural deposits with time to the

point that there would have been increasing destruction and downslope displacement of


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archaeological deposits with age Thoms (1993), Thoms and Clive (1993), Fields and

Heinrich (1987). Within the upland flats, the relative flatness of the landscape would have

inhibited the activity of slope processes and promoted the preservation of older

archaeological deposits.

Circular undrained depressions. Potential, but undemonstrated, locations for the

clustering of archaeological sites within the Neogene Uplands are the rims and adjacent

area around the edges of the circular and elliptical depressions, "Grady Ponds," found

within the upland flats. Detailed study of similar silica-karst depressions, called "Carolina

Bays," located within the Atlantic Coastal Plain of South Carolina by Brook et al. (1996)

found evidence of intense prehistoric human activity having been associated with them

between 4,000 and 10,000 BP. Similarly, wetlands, which occur within the depressions of

the upland flats, might have also at times been attractive locations for human occupation.Therefore, the rims and adjacent area around these features are potential locations for the

concentration of archaeological sites.

Pedoturbation. In addition, soils on stable geomorphic surfaces are very dynamic

systems, which result in the vertical and lateral translocation of particles, including

artifacts. These soils are very dynamic systems because, unless restricted by extreme

environmental conditions, the biota inhabiting these soils, i.e. earthworms, ants, and

fossorial vertebrates, constantly mix and redistribute particles that comprise these soils. The

uprooting of soil within tree throws cause additional disturbance and mixing of soils. The

effect of biotic processes is not only to disturb already buried archaeological deposits, but

also relatively quickly bury any surface accumulation of cultural materials (Balek 2002;

Johnson 1990; Johnson et al. 1987; Peacock and Fant 2002),

A study by Peacock and Fant (2002) of the sandy soil profile and artifacts contained

within it at Site 22MR539 within Holly Springs National Forest, north-central, Mississippi,

found that the general tendency of pedoturbation within sandy upland soils is to

progressively bury artifacts with time. Within the Holly Springs National Forest, Peacock

and Fant (2002) found that shovel tests encountered artifacts dating to about 2,000 BP at a

depth of about 60 cm (24 in) and shovel testing in the same area failed to find any artifacts.

From an analysis of the distribution with depth and their orientation within the soil profile,

they concluded that pedoturbation has progressively buried the artifacts, which had initially


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accumulated on the ground surface, within the soil profile without any additional

accumulation of sandy sediments within site 22MR539.

The possible burial of artifacts within sandy soils has been noted at archaeological

deposits found within loose, sandy soils within upland landscapes similar to the Neogene

Uplands of southern Mississippi (Peacock and Fant 2002). For example, within the sand

hills of South Carolina, Michie (1998) found that only pedoturbation could explain the

presence of Archaic through early Mississippian artifacts found buried as deep as 50 cm

(20 in) at sites 38CT17 and 38CT34 within fluvial deposits comprising Pleistocene terrace

remnants. Michie (1990) suggested that pedoturbation could cause artifacts to be buried

deeper with time within the soil profile as to create a pseudo-stratigraphy within cultural

deposits at some archaeological sites.

The pedoturbation of archaeological deposits within sandy soils has severalimplications (Peacock and Fant 2002). First, pedoturbation has had the effect of preserving

archaeological deposits by quickly burying cultural materials that accumulate on stable,

non-accreting surfaces. Because of pedoturbation, the cultural materials comprising many

archaeological sites were buried deep to have survived historic erosion and disturbance that

likely affected the surface of most of the Neogene Uplands and younger Pleistocene

terraces. Second, pedoturbation likely buried artifacts below a depth of 50 cm (20 in) as

noted by Carr et al. (1998) for sites in Greene and George counties, Mississippi. The depths

of shovel testing will have to take into consideration how deep artifacts might have been

buried by pedoturbation. Third, it is possible that pedoturbation will create sites exhibiting

cultural stratigraphy although no accumulation of sediments has occurred. Finally, it is

possible that although artifacts have been translocated vertically by pedoturbation, it might

have left some of the lateral distribution of artifacts intact.

Finally, very little is known about the stratigarphy and sediements underlying the small

streams and drainages found within the Neogene Uplands. Unfortunately, because of

differences, i.e. the presence of loess and base level graded to the Mississippi River instead

of the Gulf of Mexico, the research of Grissinger and Murphey (1983) and Grissinger et al.

(1982) can't be used to understand the geoarchaeology of these streams. However, their

research certainly indicates that these streams must likely has had a complex history


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because of Holocene climatic changes resulting in the accumulation of multiple

stratigraphic units capable of containing buried archaeological deposits.

Pleistocene Coastal Plain

Comprehensive studies comparable to the Fort Polk Predictive Models, Willinghamand Phillips (1987), and Anderson and Smith (2003) for Neogene Uplands are lacking for

the fluvial and coast-wise terraces of the Pleistocene coastal plain. From these studies, a

person can speculate that distance to permanent, especially navigable, water might be a

significant factor. Within the poorly drained, even swampy, surface of the Prairie Terraces,

well drained and topographically high landforms within the coastal plain, e.g. relict beach

ridges, other ridges, scarps, and pimple mounds, where they lie adjacent to permanent

sources of water, would have been preferred for the location for prehistoric settlement

ranging from temporary camps to more permanent settlements.

The edge of Pleistocene fluvial and coastwise terraces that form the valley walls of

incised valleys occupied by Holocene floodplains and estuaries provide highly favoured

locations for the location of prehistoric occupations and the accumulation of archaeological

deposits. For example, two major archaeological sites within Hancock County, Mississippi,

Cedar Land Plantation Site (22HA506) and Jackson Landing Site (22HA500) lie on the

relict Gulfport Barrier where it is cut by the shoreline of the Pearl River Estuary and the

sites directly overlook the estuary. Along the Pearl River, archaeological sites often occur on the edge of either Prairie or older Deweyville terraces where they directly overlook the

Holocene floodplain and lay adjacent to a tributary stream entering alluvial valley from the

terrace surface. Fewer sites are located on the edge of older Deweyville terraces where they

overlook swamps occupying relict channels of the younger Deweyville terraces and also

lay adjacent a tributary stream entering alluvial valley from the terrace surface (Gagliano et

al. 1982; Pearson et al. 1986).

As noted for the similar size stream valleys in Louisiana by Gagliano (1963), extensive

archaeological sites should be found along the edges of the Pleistocene terraces where they

form the valley walls of the tributaries of the Pascagoula and Pearl rivers. The most

promising locations should be found along these terrace edges at the junction of the valley

they form with smaller tributary streams.


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Similarly, the surface of the upper level of the Intermediate Terraces, where it

overlooks Black Creek, Island, and Redoak swamps in northern Jackson County might

potentially have been favourable for prehistoric habitation. In both locations, scarps

provided high, well drained, and level land that overlooks and lies adjacent to permanent

water and highly productive swampland. This combination of environmental factors might

have encouraged prehistoric Native Americans to settle the edge of the upper adjacent to

the scarp and result in the accumulation of prehistoric cultural deposits.

The surfaces of the Intermediate, Prairie, and Deweyville terraces all predate the

human occupation of the Mississippi Coastal Plain. As a result, unless buried by

pedoturbation within the soil profile or within colluvial deposits, the cultural deposits on

these surfaces should occur as surface accumulations. Given the ubiquitous activity of

pedoturbation within the profile of sandy soils, it is quite likely that as in case of the Neogene Uplands, prehistoric cultural materials formerly deposited on the surface of these

terraces typically have been buried within sandy soil profiles over time. It is possible, that

older archaeological components are now buried as much as 50 to 60 cm (20 to 24 in) deep

within these soil profiles by pedoturbation.

Finally, very little is known about the stratigarphy and sediements underlying the small

streams and drainages found within the Pleistocene Terraces. Unfortunately, too little is

known about the stratigraphy and depositional history of these deposits for any accurate

predictions about the occurrence of buried sites within the sediments underlying their

floodplains. However, the aggradation of their floodplains because of postglacial sea level

rise certainly resulted in the accumulation of multiple stratigraphic units capable of

containing buried archaeological deposits.

Pascagoula and Pearl River Alluvial ValleysAs with any alluvial valley, the abundant biotic resources of backswamps oxbow

lakes, and active channels must have provided prehistoric Native Americans with an

abundance of biotic resources, which they undoubtedly supported a rich and varied

population through time. Unfortunately, little, if anything has been compiled specifically

about the relationship between the occurrence of archaeological sites and landforms for

either alluvial valley. Within the alluvial valley of the Pearl River, Pearson et al. (1986)

noted that all of the sites that they examined lay on natural levees. A similar relationship


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should exist within the Pascagoula River alluvial valley. Studies in other river valleys

indicate that the natural levees adjacent to oxbow lakes occupying the abandoned channels

of active meander belts are the most likely location for the occurrence of large

archaeological sites. The alluvial aprons that flank the edges of either alluvial valley have a

potential to contain buried, well-preserved, stratified sites that date back to the beginning of

human occupation of the Gulf Coastal Plain of Mississippi. Similarly, archaeological sites

likely are closely associated with the banks of lakes and tidal channels within modern

estuary of the Pearl River (Gagliano 1963).

The floodplains of the tributaries to both the Pascagoula and Pearl rivers also have a

great potential for the occurrence of archaeological sites. Gagliano (1963) reported the

presence of extensive archaeological site adjacent to the banks of similar river systems

within Louisiana. These sites that ranged in length from over 100 m to over 0.3 km inlength and extended 30 to 90 m (100 to 300 ft) wide. Also, the alluvial aprons bordering the

valley walls of these tributaries have a potential to contain buried, well-preserved, stratified

sites.

At this time, little if anything, is known about the stratigraphy of the Holocene

sediments underlying the floodplains of the Pascagoula and Pearl rivers and their tributary

drainages. as a result, it is impossible to evaluate the potential for buried archaeological

deposits underlying the their floodplains at this time. However, given the history of

Holocene floodplain aggradation in response to post-glacial sea level rise, there is a

significant potential for the presence of buried archaeological deposits.

The alluvial fans within the Pearl River valley are potential locations for the

occurrence of cultural resources. In other river valleys, as documented by Bettis (2003) and

Hoyer (1980), alluvial fans provide some of the most well-preserved and continuous

records of human habitation within North America. Not only do they provide ideal

locations for human habitation, but also they are locations for the periodic accumulation of

sediments that bury and preserve archaeological deposits created by such habitation. The

periodic accumulation of sediments that characterize alluvial fans provide conditions

favorable for the accumulation of stratified multicomponent cultural deposits with its

components separated into individual occupations.


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Holocene Coastal Plain

Within the Holocene Costal Plain, the main high ground consists of beach ridges.

Gagliano et al (1982) noted that beach ridges and cheniers were favored landforms for

human settlement. They noted that specific locations on these ridges seemed to be favoredsites for human settlement. Specifically, the segments of beach ridges that lay near

permanently open water were often occupied in prehistoric times. These segments included

the ends of ridges where they terminated against the shorelines of bays or lakes and where

these ridges are cut by either bayous, tidal channels, or passes. Also, archaeological sites

are found where the ridges lay adjacent to either bayous or lakes. Finally, prehistoric Native

Americans favored unusually wide segments of beach ridges, specifically where two or

more ridges join together, for the occupation of these ridges. Often, archaeological sites

found on a beach ridge occur on the landward side of the beach ridge Gagliano et al (1982).

The loose sand of these beach ridges should be very susceptible to disturbance by a number

of processes, including pedoturbation. Thus, cultural materials, which originally

accumulated on the surface of these ridges might have been buried with time by not only

eolian processes, but also pedoturbation.

An important aspect of the Holocene coastal plain is the sediments underlying it

consist of late Holocene marsh, beach, brackish water, and nearshore marine sediments that

accumulated on top of older Pleistocene sediments. The surface of these older Pleistocenesediments was once the exposed surface of the Mississippi coastal plain, which was

available for occupation during the terminal Pleistocene and into the early and middle

Holocene. Thus, it is possible that Archaic and Paleo-Indian archaeological site lie buried

beneath the Holocene deposits underlying the Holocene coastal plain.

ConclusionsThe surface of Southern Mississippi, George, Hancock, Harrison, Jackson, Pearl River,

and Stone counties, can be divided into three major geomorphic regions, the NeogeneUplands, the Pleistocene Coastal Plain, and the Holocene Coastal Plain. Within the

Neogene Uplands and Pleistocene, cultural resources will occur primarily as surface sites

lying relatively near permanent water, possibly including ponds and swamps found within

enclosed depressions. Pedogenic processes can be expected to have buried artifacts


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associated within sites found on within the Neogene Uplands and Pleistocene Terraces as

deep, and possibly deeper, as 60 cm (2 ft). It is possible that the pedoturbation, in some

cases, can result in the creation of pseudostratigraphy between components of differing

ages.

The Pleistocene Terraces contain several potential locations for the occurrence of

prehistoric archaeological sites. Sites might be expected to found on the edge of Pleistocene

Terraces where they form the valley walls of floodplains, estuaries, or overlook large

swamps. Ridges and other topographically high relict landforms within the poorly drained

terrace surfaces would provide favorable sites, where they lie adjacent to permanent water

for the occurrence of archaeological sites. Finally, the edges of relict channels, where

occupied by lakes or swamp also provide locations where cultural resources might be

found.Within the Holocene Coastal Plain, specific locations for the occurrence of cultural

resources also occur. Within Holocene floodplains, the natural levees of the channels of

active and abandoned river and streams provide promising locations for the occurrence of

cultural resource. The natural levees of abandoned channel segments containing oxbow

lakes should provide the most likely locations for finding prehistoric archaeological sites.

The banks of lakes are also likely locations for the occurrence of archaeological sites.

Within coastal strandplain systems, beach and chenier ridges are the most promising

landform for the location of prehistoric archaeological deposits.

References Cited

Anderson , David G., and Steven D. Smith 2003 Archaeology, History, and Predictive Modeling Research at Fort Polk,

1972-2002. University of Alabama Press, Tuscaloosa.

Balek, Cynthia L.

2002 Buried artifacts in stable upland sites and the role of bioturbation: a review.Geoarchaeology. 17(1):41-51.

Bernard, Hugh Allen1950 Quaternary Geology of Southeast Texas. Unpublished Ph.D. dissertation,

Department of Geology, Louisiana State University, Baton Rouge.


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Bicker, Alan R.1969 Geologic Map of Mississippi. Geologic map, 1:500,000. Office of Geology,

Department of Environmental Quality, Jackson.

Bettis, E Arthur, III

2003 Patterns in Holocene colluvium and alluvial fans across the prairie-foresttransition in the Midcontinent USA. Geoarchaeology. vol.18, no. 7, pp. 779-797.

Brooks, Mark J., Barbara E. Taylor, and John A. Grant1996 Carolina Bay geoarchaeology and Holocene landscape evolution on the upper

coastal plain of South Carolina. Geoarchaeology. 11(6):481-504.

Brown, G. F., V. M. Foster, R. W. Adams, E. W. Reed, and H. D. Padgett, Jr.1944 Geology and Ground-Water Resources of the Coastal Area in Mississippi.

Bulletin no. 60, Mississippi State Geological Survey, Jackson.

Carr, P. J., C. Jenkins, K. L. Bruce, and B.J. Gray1998 Cultural Resource Survey of Proposed Relocation of Mississippi Highway

63 from U.S. Highway 98 to Leakesville (MDOT Project No. 98-0002-01-016-10/101150), George and Greene Counties, Mississippi. Report Prepared for theMississippi Department of Transportation, Jackson.

Dockery, David T., III1995 Rocks and Fossils Collected from Mississippi Gravel. Mississippi Geology.

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