Assessing the sedimentation deficit problem in Louisiana's coastal salt marshes
The imbalance between relative sea-level rise and vertical marsh accretion is frequently cited as a major factor in the problem of wetland loss in coastal Louisiana. Relative sea-level rise rates are high, compared to the rest of the Gulf coast, owing to subsidence of Holocene Mississippi deltaic plain sediments, and although marsh accretion rates are also high, in comparison with other coastal areas of the US, they are usually insufficient to maintain the relative elevation of the marsh surface. This situation is commonly referred to as a sedimentation deficit. One of the problems with evaluating the magnitude of the sedimentation deficit problem in Louisiana, and its spatial variation, is that measurements of subsidence and marsh accretion or sedimentation are rarely made on similar time scales. Subsidence affecting the marsh surface is composed of a number of factors, including compaction of recently deposited sediments, regional downwarping, and diagenesis of underlying Pleistocene and earlier sediments. The total effect of these factors, in combination with eustatic sea-level rise, is frequently obtained from tide gauge measurements over the last 50 years or so. Subsidence is also measured by dating sedimentary horizons of known depth that characterize surface environments. Carbon-14 is a common tool for this type of study and subsidence is then averaged over periods of up to several thousand years. In comparison, marsh accretion or sediment deposition can be measured over periods from several hundred years, using Lead-210 dating, to several days, using marsh surface sediment traps. The many techniques available for measuring the sedimentary status of the marsh surface can provide a variety of information concerning the processes responsible for sediment deposition and vertical accretion.
- OSTI ID:
- 5949417
- Report Number(s):
- CONF-9010204--
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Vol. 74:9; ISSN AABUD; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
ALPHA DECAY RADIOISOTOPES
AQUATIC ECOSYSTEMS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14
CARBON ISOTOPES
CENOZOIC ERA
DEPOSITION
DIAGENESIS
ECOSYSTEMS
EVEN-EVEN NUCLEI
FEDERAL REGION IV
FEDERAL REGION VI
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC TRAPS
GROUND SUBSIDENCE
GULF COAST
HEAVY NUCLEI
ISOTOPES
LEAD 210
LEAD ISOTOPES
LEVELS
LIGHT NUCLEI
LOUISIANA
MARSHES
MISSISSIPPI
NORTH AMERICA
NUCLEI
QUATERNARY PERIOD
RADIOISOTOPES
SAND
SEA LEVEL
SEDIMENTATION
SEDIMENTS
USA
WETLANDS
YEARS LIVING RADIOISOTOPES