Paul Tinerella and Michael Newbrey
Geol 640: Regional Pollen Survey
19 February 2003
Georgia/ Florida Pollen Survey
Pollen records obtained from lake cores are important for understanding Quaternary vegetation patterns and thereby paleoclimates. To gain a better understanding of the importance of pollen cores, we examined the SiteSeer Pollen Database (http://www.ngdc.noaa.gov/paleo/softlib/siteseer.html) for vegetation changes in Georgia and Florida during the Late Pleistocene and Holocene.
Methods
We examined all site locations (Fig. 1) and pollen core records to determine comparability of cores. We eliminated four sites from the dataset (Fig. 1). Two sites were eliminated because of geographic location influenced vegetation patterns. We determined that Pigeon Marsh, Georgia (Watts 1975) is located at a higher elevation than other sites and its location explained the mosaic of biotypes observed in the pollens core. Camel Lake, Florida (Watts et al. 1992) is located near the coast and vegetation record is influenced differently than the other localities. Lake Louise, Florida and Lake Hall, Florida were not examined because they lacked a chronology (Watts 1971).
Results
We selected three lakes for examination and contrasted their pollen chronologies (Fig. 1). The Lake Tulane, Florida chronology extends back to 50,000 years BP and is the longest chronology in our dataset (Grimm et al. 1993)(Fig.2). The chronology of Sheelar Lake, Florida extends to 23,000 years BP (Watts and Stuiver 1980)(Fig.3), while Quicksand Pond, Georgia dates back to 20,000 years BP (Watts 1970)(Fig. 4). We infer the vegetation and climatic changes as follows:
Summary of Vegetational Changes:
20-50 ka: Oscillations between Quercus and Pinus: Pine forest to Oak savanna
16-20
ka: Quercus and Poaceae
stable with oscillations of Pinus
12-16 ka: Stable Pine forest with oscillations in Spruce component; Grasses high
9- 12 ka: Pine forest fluctuating; Oak savanna stable
3- 9 ka: Pine forest and Oak savanna present with fluctuations in grasses and weeds (Chenopodiaceae and Amaranthaceae, etc.)
3 ka- Present: Pine forest dominates; reduced Oak savanna/ deciduous/ grass and forb component present
Summary of Climate Changes:
20-50 ka: Oscillations between cooler/ wet and warmer/ dry
16-20 ka: Predominantly warmer/ dry with short fluctuations to cooler/ wet
12-16 ka: Cooler and wetter conditions with oscillations to warmer and drier conditions
9-12 ka: Warmer and drier conditions with short fluctuations of cooler and wetter events
3- 9 ka: Climate generally warmer and drier fluctuating to cooler/ wetter conditions
3 ka- Present: Generally cooler/ wetter with fluctuations of warmer/ drier events
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Figure 1. Pollen core data provided by the SiteSeer Pollen Database (http://www.ngdc.noaa.gov/paleo/softlib/siteseer.html).
Figure 2. Pollen core results from Lake Tulane, Florida (Grimm et al. 1993) showing numerous fluctuation in Pinus. Lines indicate changes in vegetation and perhaps climate.
Figure 4. Pollen core results form Quicksand Pond, Georgia (Watts 1970). Lines indicate changes in vegetation and perhaps climate.
Discussion
It is interesting to note that many of the
vegetational changes are correlated with Heinrich events. Heinrich events are evidenced by carbonate-rich
layers of ice-rafted debris (IRD) in deep ocean cores. The Heinrich events are correlated with IRD
and maximum iceberg calving. Heinrich
layers were deposited between 70 and 14 Ka years ago, and were accompanied by
decreases in sea surface temperatures and salinity and by massive discharges
of icebergs from the eastern margins of the Laurentide ice sheet. Grimm et al.
(1993) noted that peak abundance of Pinus estimated from a pollen core
in Lake Tulane, Florida coincides with Heinrich events H1 through H5 (Fig. 5).
The cooling of the surface water perhaps provided the cooler temperatures
and moisture needed to support abundant Pinus.
Figure 5. Peak abundance of Pinus as correlated with Heinrich events. Figure taken from Grimm et al. (1993:figure 4)
References
Grimm, E. C., G. L. Jacobson Jr., W. A. Watts., B. C. S. Hansen, and K. A. Maasch. 1993. A 50,000-year record of climate oscillations from Florida and its temporal correlation with the Heinrich Events. Science 261(5118): 198-200.
Watts, W.A. 1970. The full-glacial vegetation of northwestern Georgia. Ecology 51:17-33.
Watts, W.A. 1971. Postglacial and interglacial vegetation history of southern Georgia and central Florida. Ecology 52:676-690.
Watts, W.A. 1975. Vegetation record for the last 20,000 years from a small marsh on Lookout Mountain, northwestern Georgia. Geological Society of America Bulletin 86:287-291.
Watts, W.A., B.C.S. Hansen, and E.C. Grimm. 1992. Camel Lake: A 40,000-yr record of vegetational and forest history from northwest Florida. Ecology 73:1056-1066.
Watts, W.A., and M. Stuiver. 1980. Late Wisconsin climate of northern Florida and the origin of species-rich deciduous forest. Science 210:325-327.