7.2 PHYSICAL CHARACTERISTICS 



7.2.1 Geolog y 



Mainland Dare County is located on the 

 Pamlico Terrace and bordered by water on three 

 sides with a land connection to the south. The penin- 

 sula is based on recent Quarternary deposits con- 

 sisting of surficial organic materials of varying 

 thickness overlying undifferentiated and complexly 

 interbedded layers of sand, silt, clay, and mollusk 

 shells (Heath 1975). 



The following discussion of recent geo- 

 logical processes follows Peacock and Lynch (1982). 

 The Pamlico Terrace is the lowest and youngest of 

 the several generalized surfaces of the Coastal Plain 

 recognized as having been formed during periods of 

 higher sea level. About 75,000 years B.R, the edge 

 of the sea lay inland to a point now marked by the 

 sandy ridge of the Suffolk Scarp (Daniel 1981) lo- 

 cated 72 km to the west of the Dare mainland's cur- 

 rent shoreline. At the peak of the Wisconsin 

 glaciation, the sea was far below its modern level. As 

 elsewhere in the cedar's range, the complex cycle of 

 marine transgressions and regressions produced 

 differing effects upon the topography of the al- 

 ternately exposed and submerged surfaces. Rising 

 seas slowed stream erosion by raising stream base 

 levels, and planed off the previous surface features 

 or obscured them with silts and muds. Falling sea 

 level, in contrast, exposed areas of the continental 

 shelf and rejuvenated streams, increasing downcut- 

 ting and topographic relief. 



7.2.2 Development of Peat Deposits 



During the recent period of rising sea level, 

 conditions favorable to peat formation have 

 prevailed in Dare County and throughout the North 

 Carolina Coastal Plain. During the past 1 0,000 years, 

 peat has been forming under swamp forests, 

 pocosins, and marshes, in blocked drainages, 

 Carolina bays, and river floodplains (Otte 1981). Ex- 

 tensive sampling of peat depths, in conjunction with 

 surveys of energy-grade peat deposits, indicate the 

 presence of a subpeat system of southeast to 

 northwest oriented stream channels (Ingram and 

 Otte 1981, 1982) which have not yet been explored 

 in detail. 



7.2.3 Soils 



Soils of mainland Dare County were mapped 

 for the first time by Barnes (1981, and unpubl.; 

 USACE 1982) (Figure 39). Organic soils 

 predominate; the deepest histosols border the Al- 



ligator River and also occupy prepeat drainage chan- 

 nels in the interior of the county. Shallow histosols 

 generally adjoin deeper peats in the soilscape; 

 mineral series occur in areas which were interstream 

 divides, slightly more elevated on the prepeat sur- 

 face. Prepeat topography is now thoroughly ob- 

 scured by organic deposits, as illustrated in Figure 

 22, where a cross section shows the relationships of 

 peat depth, underlying mineral sediments, and soil 

 series. 



In Dare County, Atlantic white cedar associa- 

 tions are most frequently established on deep or- 

 ganic soils of the Dare and Pungo Series or on the 

 shallower histosols of the Ponzer, Kilkenny and Mat- 

 tamuskeet series. Pure and mixed stands are occa- 

 sionally associated with the Roper and Pettigrew 

 series which are mineral soils with a histic epipedon 

 (organic surface layer). In a few instances (e.g., west 

 of the northern half of the bombing range), swamps 

 including white cedar are found extending from or- 

 ganic soils onto poorly drained mineral soils which 

 have a thick black or very dark gray highly organic 

 loam surface (Hyde and Cape Fear soil series). 



All of the soils of the region, classified as 

 "hydric soils" by the Soils Conservation Service 

 (USDA, SCS 1985a), are extremely wet year round, 

 though water seldom pools on the surface. They are 

 acidic (pH 3.0-4.0) (Barnes, unpubl.) and have large 

 quantities of Atlantic white cedar and bald cypress 

 roots, stumps, and logs throughout the profile. Sur- 

 face and subsurface accumulations of charcoal indi- 

 cate a history of severe fires in parts of the region 

 (Otte 1981). 



The transition zone between organic and 

 mineral material averages less than 0.5 m, with little 

 soil development in the underlying mineral layer (Dol- 

 man and Buol 1967). Daniels etal. (1984) believe that 

 the lack of a distinct soil beneath the histosols indi- 

 cates that the soils of the region have been con- 

 tinuously wet, with buildup of organic materials 

 during wetter periods and loss during drier climatic 

 times. 



Soils suitable for white cedar establishment 

 appear to be abundant in many areas of the Dare 

 peninsula, principally concentrated in the western 

 sector closest to the Alligator River 



7.2.4 Physiography and Hydrolog y 



The Dare mainland lies within the Atlantic 

 Coastal Plain Physiographic Province and is charac- 

 terized by relatively flat terrain with elevations rang- 

 ing from 3.7 to m above mean sea level, declining 



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