Barrier/lagoon and shoreface Holocene stratigraphy: Masonboro Island, N. C
- Univ. of North Carolina, Wilmington, NC (United States). Dept. of Earth Sciences
- East Carolina Univ., Greenville, N.C. (United States). Dept. of Geology
- Duke Univ., Durham, N.C. (United States). Dept. of Geology
Masonboro Island, located at the southwestern extremity of Onslow Bay, is a low relief 13 km long overwash dominated transgressive barrier. The stratigraphy and Holocene history of the barrier, estuary and shoreface was investigated utilizing 70 vibracores recovered from the estuary and the shoreface to water depths of 15 m. An additional 200 hand driven 3 m long cores were obtained from the intertidal beaches and fringing marshes. Thickness of the Holocene estuarine fill ranged from less than 5 m to more than 8 m in the backfilled valleys. The mud fill of the early Holocene possibly reflects a physiographically different ancestral barrier. Core data indicate intertidal environments have been characteristic of the estuary since its formation 4,100 years BP. The barrier platform is seldom thicker than 5 m except in the vicinity of former inlets. Data suggest inlets have been restricted to narrow zones due to the small tidal prism and the resistant units upon which the barrier rests. The presence of peat beneath major segments of the low tide beach indicates migrating inlets have not consistently played a major role. The shoreface is relatively steep. Seaward of 8 m water depth the thickness of the modern sediment cover is generally less than 50 cm and consists of a mobile sequence of graded sand and gravel units. The Holocene barrier lithosomes have not been preserved during shoreface migration. When present they consist of coarse channel fill or muddy gravels with organics similar to basal portions of oyster reefs. Palimpset material along with residual sediments developed on Oligocene Is. and calcarenite hardgrounds are often incorporated into the overlying sediment cover. Trenches and cores from overwash fans/terrace commonly show interbedded coarse gravel layers similar in composition to those found on the middle and lower shoreface. The data suggests that sediment exchange between the barrier and the shoreface is common.
- OSTI ID:
- 6079448
- Report Number(s):
- CONF-9304188-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:4; Conference: 42. annual Geological Society of America (GSA) Southeastern Section meeting, Tallahassee, FL (United States), 1-2 Apr 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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