PARENT SESSION
Poster Session # 17: Aquatic Systems.
Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Organic-sediment stratigraphy of elongated tree-islands, Everglades National Park.
Stone, Peter*,1, Ross, Michael 2, Ruiz, Pablo2, Reed, David2, Chmura, Gail3, 1 South Carolina Dept. Health and Environmental Control, Columbia, SC2 Florida International University, Miami, FL3 McGill University, Montreal, Quebec, Canada
ABSTRACT- Larger tree-islands in freshwater peat marsh of the southern Everglades are distinctly elongated parallel to sluggish overland flow, occupy slight ridges of organic sediment (peat at the top), and are usually focused at their upstream end on a sediment-buried bedrock mound. Six tree-islands were cored to limestone bedrock to examine stratigraphy of accreted organic sediments and reveal the depositional history. Archeologically modified organic soil and debris comprised the sediments present on the bedrock mound. Stratigraphies beneath the long downflow "tails" were much more complex than the deeper peats typically found in elongated tree-islands of the northeastern Everglades. Southern Everglades profiles commonly included inter-layering of peat (fibrous organics), muck (fine grained organic-and-mineral mud), and in places apparent ash from organic-soil fires, sometimes all lying above basal marsh marl (calcareous silt precipitated by algae in seasonally flooded marshes). Establishment of organic-sediment ridges thus appears to post-date and succeed the development of the Everglades marsh itself in these specific geographic positions. The abundance of fine-textured siliceous mineral matter of the muck was not anticipated, given the lack of an obvious source, the very low current velocities, and the rarity of similar constituents in the surrounding marsh peats. The muck and muck-peat mixtures found at mid-levels in these profiles suggest that physical transport of solid material has been important in the formation of ridges, and thus probably in the wider Everglades system. An alternative mechanism, i.e., in which ridge development depends exclusively on enhanced plant production and peat sedimentation resulting from nutrient delivery (perhaps dissolved) from the upstream "head" into a low-nutrient-status marsh, thus seems insufficient to explain the low, forested ridges of southern Everglades tree-islands. Mineral, chemical, and pollen content of the muck constrain its likely origin.
Key words: forest-island, peatland