LEADER 07292ctm 2200625 i 4500001 ocm06403541 003 OCoLC 005 20230822035313.0 008 800610s1979 xx abf bm 000 0 eng d 035 (Sirsi) o06403541 035 (OCoLC)6403541 040 ERE |beng |erda |cERE |dOCL |dOCLCQ |dOLA |dERE |dOCLCQ |dOCLCF |dOCLCQ |dOCLCA |dOCLCQ |dOCL |dOCLCO |dOCLCQ |dERE |dUtOrBLW 043 n-us-nc 049 EREE 050 4 QE699 |b.B4x 100 1 Benton, Stephen B. |q(Stephen Boyd), |eauthor. |=^A1461119 245 10 Holocene evolution of a nanotidal brackish marsh : |bprotected bay system Roanoke Island, North Carolina / |cby Stephen Boyd Benton. 264 0 |c1979. 300 xii, 176 leaves, 17 leaves of plates : |billustrations, maps ; |c28 cm 336 text |btxt |2rdacontent 337 unmediated |bn |2rdamedia 338 volume |bnc |2rdacarrier 502 |bM.S. |cEast Carolina University |d1979 500 Presented to the Graduate Faculty of the Department of Geology 500 Advisor: Stanley R. Riggs 520 3 The Broad Creek study area on the southeastern end of Roanoke Island is located within the large estuarine system dominating the northern half of coastal North Carolina. Estuaries in northeastern North Carolina are characterized by low salinities (0 to 25 ppt) and low astronomical tides ([less-than] 15cm). However, because of their large size and shallowness, they are strongly influenced by wind tides. The study area consists of three environments; a shallow elongated embayment (Broad Creek) protected from most wave energy, a tidal creek system, and an irregularly flooded brackish marsh dominated by Juneus roemerianus. Within the study area, sediment distribution patterns are similar to the sediment distribution patterns which occur within the larger scale estuarine system of northeastern North Carolina. Sedimentation processes operating within the study area include the following: 1) wave erosion during low wind tides and biocorrosion of the marsh shoreline recycling fine sediment and organic material; 2) permanent deposition of suspended sediments within the central, deeper portions of the bay during normal energy conditions; 3) deposition of suspended sediments on the marsh surface during high wind tides; 4) nondeposition, winnowing, and reworking of lag sands into thin shelf bars on outcrops of a muddy sand unit lateral to the central bay mud depositional environment within Broad Creek; 5) channel bottom scour within meanders of the tidal creek system; 6) deposition of highly organic rich mud on shoals lateral to the tidal creek channel; and 7) erosion and southerly transport of fine to medium grained sands along the high energy Roanoke Sound shoreline and deposition on a bay mouth bar forming across the southern end of Broad Creek Stratigraphic relationships and dates indicate that the present Broad Creek system is a product of a series of evolutionary changes which occurred over the past 6,000 years. The study area represents a relict drainage system formed during the late Wisconsin lowstand of sea level which has been progressively drowned by rising sea level through time within an increasing influence of marine conditions. The drowning influence was confined to the floodplains from 6,000 B.P. until approximately 2,500 B.P. Between 2,500 B.P. and 1,500 B.P. fresh marshes expanded rapidly across the low interstream divides within the study area as the floodplains were overtopped by the transgression. Between 1,500 B.P. and 1,000 B.P., the fresh marshes were replaced by brackish marshes which moved into the study area from the southeast. Brackish marshes continue to dominate the study area today and respond to rising sea level by growing vertically and migrating landward over the inorganic uplands. The Broad Creek embayment has expanded to its present size through erosion of its marsh shorelines. The eroded shorelines are undercut peat scarps with relief of 0.75 to 1.0 meter. This steplike shoreline geometry and the sedimentation processes operating within the study area represent a major departure from tidal flat shoreline geometries and sedimentation processes reported in similar scale systems characterized by astronomical tidal ranges [greater-than]1/2 meter. Since this natural astronomical tidal range break falls within the microtidal classification generally in use, a new tidal range subdivision to be called "nanotidal" is proposed for estuarine systems with a tidal range of [less-than]1/2 meter. Erosional peat scarp shorelines like those found within Broad Creek are typical throughout the northeastern North Carolina estuarine system. Considering the magnitude of erosion of marsh shorelines, it is feasible that this mechanism provides a significant means of introducing organic detritus into the estuarine system where regular tidal flushing is not significant. Preliminary calculations show similar amounts of organic detritus entering the northeastern North Carolina estuaries through erosion to amounts reported entering Georgia estuaries through tidal flushing. 504 Includes bibliographical references (leaves 151-159). 650 0 Geology, Stratigraphic |yHolocene. |=^A224336 650 0 Geology |zNorth Carolina. |=^A19177 650 0 Marshes |zNorth Carolina |zRoanoke Island. |=^A9300 650 7 Geology. |2fast |0(OCoLC)fst00940627 650 7 Geology, Stratigraphic. |2fast |0(OCoLC)fst00940727 650 7 Holocene Geologic Period. |2fast |0(OCoLC)fst01353233 650 7 Marshes. |2fast |0(OCoLC)fst01010775 651 7 North Carolina. |2fast |0(OCoLC)fst01204304 |?UNAUTHORIZED 651 7 North Carolina |zRoanoke Island. |2fast |0(OCoLC)fst01241356 |?UNAUTHORIZED 648 7 From 10 thousand years ago |2fast 655 7 Academic theses. |2fast |0(OCoLC)fst01726453 655 7 Academic theses. |2lcgft 655 7 Thèses et écrits académiques. |2rvmgf |0(CaQQLa)RVMGF-000001173 700 1 Riggs, Stanley R., |edegree supervisor. |=^A80459 710 2 East Carolina University. |bDepartment of Geology. |?UNAUTHORIZED 856 41 |zAccess via ScholarShip |uhttp://hdl.handle.net/10342/11549 949 Click on web address |wasis |hjoyner101 949 Click on web address |wasis |hhsl111 994 C0 |bERE 998 174578 998 174578 590 Joyner-"Presented to the graduate faculty of the Department of Geology ... in partial fulfillment of the requirements for the degree Master of Science in Geology." 590 Joyner-"Presented to the graduate faculty of the Department of Geology ... in partial fulfillment of the requirements for the degree Master of Science in Geology." 590 Joyner-"Presented to the graduate faculty of the Department of Geology ... in partial fulfillment of the requirements for the degree Master of Science in Geology." 596 1 4