Geological Society, London, Special Publications
Geological Society, London, Special Publications; 1996;
v. 117;
p. 249-266;
DOI: 10.1144/GSL.SP.1996.117.01.15
© 1996 Geological Society of London
Nearshore and Coastal Environments |
The influence of inherited geological framework upon a hardbottom-dominated shoreface on a high-energy shelf: Onslow Bay, North Carolina, USA
W. J. Cleary1,
S. R. Riggs2,
D. C. Marcy1 &
S. W. Snyder3
1 Department of Earth Sciences, University of North Carolina at Wilmington, Wilmington, NC 28403, USA
2 Department of Geology, East Carolina University, Greenville, NC 27658, USA
3 Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA
The southeastern coast of North Carolina is a major tourist destination that has experienced rapid population growth resulting in increased revenues. Most development is sited on transgressive barriers and headland beaches located along chronic erosion zones. Beach replenishment is viewed as the only viable option for erosion mitigation. However, a detailed sand resource assessment is non-existent. Furthermore, few data exist on the inter-relationships between the underlying geological framework and the morphology, sediments and evolution of the coastal system.
The shoreface of the two constraining headlands of this sand-starved system in Onslow Bay was studied utilizing cores, remotely sensed data, and diver surveys. The (coquina-dominated) subaerial headland at Fort Fisher and the (limestone) submarine headland at New River clearly have influenced the coastwise evolution of the intra-headland perched beaches. These shorefaces, as well as those of adjacent barriers, are characterized by hardbottoms of varying relief, morphology, and lithology. Prominent submarine scarps and karstic topographic highs that extend above the ravinement surface have resulted in major changes in barrier orientation and development of distinct subcompartments with respect to coastal processes.
Holocene sea-level rise has produced a thin (<70 cm) variable sequence, deposited unconformably over bioeroded hardbottoms. Bioerosion represents a major source and supply of new sediment. The thin sediment veneer is a mosaic of remobilized graded palimpsest and residual shell-rich sand and gravels. Data reinforce the concept that a common equilibrium profile for all shorefaces is neither realistic nor adequate for an understanding of coastal processes in the study area.
