Geological controls on the formation and preservation of Holocene organic coastal facies are analogous to those found in marginal-marine sedimentary deposits of economic importance. Coastal barriers along the paraglacial coast of New England are associated with a variety of estuarine and backbarrier environments that include tidal flats, salt marshes, lakes, ponds, and bogs. To date, the role of organic facies as high-resolution lithologic and chronostratigraphic markers within barrier lithosomes has not been addressed. The Kennebec barrier chain located along the south-central coast of Maine provides a good opportunity to study the patterns of coastal-fluvial upland interaction and preservation potential of organic-rich sediments in clastic coastal sequences.
A detailed stratigraphic analysis of 14 barrier systems, based on 150 cores and 40 km of high-resolution ground-penetrating radar profiles, was used to identify several distinct organic facies. This database has been used for mapping, stratigraphic correlation, and interpretation of environmental changes associated with each facies (water table fluctuations, saltwater intrusion, closure of tidal inlets, etc.). The next phase of the research is to obtain conventional 14C and AMS dates on in-situ organic materials which will be used to establish a regional chronology of coastal development. Basal dates will provide information on the timing of backbarrier deposition, whereas dating the top portions of organic horizons that lack evidence of erosion will give a near-maximum age of their burial by barrier sediments. Preliminary results indicate that some maritime bogs began forming prior to 4,600 years ago and since that time have been episodically buried by washover and aeolian sands.
AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid