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Research Articles: Coastal Sedimentation |
1 Institute of Marine Sciences, University of North Carolina at Chapel Hill, 3431 Arendell Street, Morehead City, North Carolina 28557, U.S.A.; abrodrig{at}email.unc.edu
2 Devon Energy Corporation, 1200 Smith Street, Houston, Texas 77002, U.S.A.
Recent Gulf of Mexico shoreline studies interpret middle to late Holocene sea level as falling from a level above present elevation or stable at present elevation; however, the architecture of Morgan Peninsula, Alabama, does not support this. Morgan Peninsula is a beach-ridge strandplain composed of two obliquely aligned Holocene beach-ridge sets. Ground-penetrating radar profiles discriminate between parallel, even to wavy reflectors of the eolian dune environment and the underlying seaward-dipping, complex sigmoidal-oblique reflectors of the foreshore and upper-shoreface environment. The contact between foreshore and eolian facies in beach ridges can be used as a sea-level indicator. The average elevation of this contact in Morgan Peninsula rises throughout shoreline accretion, which occurred throughout the last 5.4 ka, suggesting that there was continual sea-level rise during this time.
Morgan Peninsula is a useful modern analog to ancient shoreface–shelf parasequences and demonstrates the significant internal complexities that can exist in these deposits. Erosional discontinuities imaged in the Holocene foreshore–upper shoreface environment are laterally continuous, extend to elevations above mean sea level, and correlate to beach ridges and the transition between beach-ridge sets. An increase in the wave regime or fluctuations in sediment supply appear to be likely mechanisms for forming erosional discontinuities below beach ridges. The erosional surface separating beach-ridge sets may have formed by increased storm activity and associated barrier breaching, or a reconfiguration of the Mobile Bay tidal-delta complex superimposed on a gradual rate of sea-level rise. This boundary is recognized by a change in beach-ridge orientation at the surface and an increase in the aggradational component of shoreline accretion.
This article has been cited by other articles:
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  K. SEIKE INFLUENCE OF BEACH MORPHODYNAMICS ON THE DISTRIBUTIONS OF THE OPHELIID POLYCHAETE EUZONUS SP. AND ITS FEEDING BURROWS ON A SANDY BEACH: PALEOECOLOGICAL AND PALEOENVIRONMENTAL IMPLICATIONS FOR THE TRACE FOSSIL MACARONICHNUS SEGREGATIS Palaios, December 1, 2009; 24(12): 799 - 808. [Abstract] [Full Text] [PDF]
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 A. R. Simms, N. Aryal, Y. Yokoyama, H. Matsuzaki, and R. Dewitt Insights on a Proposed Mid-Holocene Highstand Along the Northwestern Gulf of Mexico from the Evolution of Small Coastal Ponds Journal of Sedimentary Research, October 1, 2009; 79(10): 757 - 772. [Abstract] [Full Text] [PDF]
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 J. P. Donnelly and L. Giosan Tempestuous highs and lows in the Gulf of Mexico Geology, September 1, 2008; 36(9): 751 - 752. [Full Text] [PDF]
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D. L. Greene Jr., A. B. Rodriguez, and J. B. Anderson Seaward-Branching Coastal-Plain and Piedmont Incised-Valley Systems Through Multiple Sea-Level Cycles: Late Quaternary Examples from Mobile Bay and Mississippi Sound, U.S.A. Journal of Sedimentary Research, February 1, 2007; 77(2): 139 - 158. [Abstract] [Full Text] [PDF]
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