PARENT SESSION
Oral Session #10: Paleoecology. Presiding: S. Hotchkiss.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Hall of Ideas J.
Can regional landscape evolution be determined by the study of one lake?
Winkler, Marjorie1, Sanford, Patricia1, 1
ABSTRACT- For study of Cape Cod National Seashore environmental changes, sediment cores from 10 kettle ponds within a 12 km2 area were radiocarbon-dated and analyzed for pollen, diatoms, charcoal, sediment composition and chemical changes. All ponds were small, deep basins less than a meter asl set in cryptodepressions in glacial outwash. Some formed a chain of ponds connecting to the sea; others were closed basin. The cores contained between 7 and 2 meters of sediment with basal dates from deglaciation (about 13,000 yr B.P.) or from the middle Holocene (since 5000 yr B.P.). Cores with younger dates had sands and gravels interrupting lake sediment deposition. One closed-basin pond dated from 13,000 yr B.P. but then contained sands and gravels until 5000 yr B. P. Another pond was a bog for 3000 years after deglaciation. Pollen analysis from all older ponds indicated sequential dominance by spruce, jack pine, white pine, pitch pine and oak, and alternation of mesophytic trees and pine barrens until present. Diatom analysis separated the ponds into two groups: connected to or separated from the sea. Specific event/s that brought gravels to some ponds but not others nearby is not known although severe storms or drought effects on ponds without clay-rich perched aquifers are possibilities. High Pb, Se, Hg, As, Zn, and Cu concentrations in recent sediments document that all Cape ponds are impacted locally by land-use changes and by atmospherically-disseminated pollutants. Pollen from one pond sufficiently determines regional upland vegetation, but pond geomorphic evolution is unique.
KEY WORDS: kettle pond development, Cape Cod National Seashore, recent water quality changes, paleovegetation and paleolimnology