Data from a transect of four cores collected in the Makepeace Cedar Swamp, near Carver, Massachusetts, record past changes in deposition, vegetation, and water level. Time series of palynological data provide a 14,000-yr record of regional and local vegetation development, a means for biostratigraphic correlation and dating, and information about changes in water level. Differences in records among cores in the basin show that water level decreased at least 1.5 m between 10,800 and 9700 cal yr B.P., after which sediment accumulation was slow and intermittent across the basin for about 1700 yr. Between 8000 and 5600 cal yr B.P., water level rose 2.0 m, after which slow peat accumulation indicates a low stand about the time of the hemlock decline at 5300 ± 200 cal yr B.P. Dry conditions may have continued after this time, but by 3200 cal yr B.P., the onset of peat accumulation in shallow cores indicates that water level had risen to close to its highest postglacial level, where it is today. Peat has accumulated across the whole basin since 3200 cal yr B.P. Data from Makepeace and the Pequot Cedar Swamp, near Ledyard, Connecticut, indicate an early Holocene dry interval in southern New England that began 11,500 yr ago near the end of the Younger Dryas interval. The dry conditions prevailed between 10,800 and 8000 cal yr B.P. and coincide with the arrival and later rise to dominance of white pine trees (Pinus strobus) both regionally and near the basins. Our results indicate a climatic cause for the “pine period” in New England.
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Figure 1. (a) Maps showing location of Makepeace Cedar Swamp, Carver, MA, and Pequot Cedar Swamp, Ledyard, CT. (b) Makepeace Cedar Swamp basin showing perpendicular transects A and B that delineate one of the sub-basins. (c and d) Transects A and B depth/bathymetry profiles based on probes every 10 m and the location of four sediment cores along transect A. |
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Figure 2. Sediment stratigraphies, percentage of organic matter, and intervals with identified macrofossils for cores A–D, with percentage of humification, carbonate, and iron content for core A. Intervals of sediment (292–300, 188–200, and 73–100 in core D; 168–200 and 52–100 in core A; 393–400, 182–200 and 60–100 in core C; and 156–175 and 49–100 in core B) are not represented with stratigraphic depths because of compaction during the coring process. |
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Figure 3. Regional pollen stratigraphy, age-models and sediment accumulation rates for core A. The 14C and biostratigraphically revised dates are shown next to the lithologic change from peat to mud. Numbers on the pollen stratigraphy show the locations of the seven pollen events listed in Table 2 and described in the text. |
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Figure 4. Pollen stratigraphy for Makepeace Cedar Swamp cores A (upper), B (middle), and D (lower). CP for core B indicates interval of sediments compacted during core extrusion. Asterisks indicate pollen types used in the regional pollen sum that also includes ash (Fraxinus), basswood (Tilia), elm (Ulmus), hackberry (Celtis), hazel (Corylus), holly (Ilex), ironwood/hornbeam (Ostrya/Carpinus), larch (Larix), mulberry (Morus), poplar (Populus), walnut (Juglans), and wormwood (Artemesia). |
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Figure 5. Paleohydrologic summary diagrams for Makepeace (core A, upper) and Pequot Cedar Swamps (core B, lower) comparing lithology, sediment analyses, and a shared sequence of local and fossil palynological and paleoenvironmental indicators to show similar trends toward dry conditions during the maximum of white pine (P. strobus) pollen ca. 10,200 cal yr B.P. (9000 yr B.P.). Total (solid line) and regional (dotted line) pollen accumulation rates are shown for core A. The same taxa are shown for both sites, but stippling indicates that a taxon was not used for the paleohydrologic interpretation for that site. |
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Figure 6. (a) Correlations based on analog matches among fossil pollen data (dotted lines) and dated sediments (solid line). Italicized ages are 14C dates. (b) Estimated water level for Makepeace Cedar Swamp at 13,700, 13,000 to 11,400, 9720 to 7960, 5600, and 3200 cal yr B.P. Boxes indicate that 14C dated intervals were used to estimate the water level for each time period, and lines indicate analog and/or stratigraphic correlation was used. |
