Abstract Introduction Marl Prairie Habitat & Community Everglades Hydrologic History Methods > Results Discussion Conclusions Acknowledgements References Figures & Tables PDF

Radiocarbon dates from the upper 8 cm of core 03-9-16-6 yield >110 pMC (percent modern carbon). This indicates that the analyzed material is less than 50 years old and has more ¹⁴C than the 1950 AD reference standard; thermonuclear testing during the 1950s generated ¹⁴C, and organisms that lived after that time incorporated the "extra" ¹⁴C in their biomass, yielding results with >100 pMC. Casuarina pollen first occurs at 7.5 cm in cores 03-9-16-3 and 03-9-16-6; this is consistent with radiocarbon dates from 03-9-16-6 that indicate deposition of the upper 8 cm during the 20^th century. Radiocarbon dating of the sample at 10.5 cm in core 03-9-16-6 indicates a calibrated age of 300 yrBP; the one sigma ranges for this calibrated date are 310-290 yrBP, indicating deposition well before hydrologic changes of the 20^th century. However, the two sigma ranges for the calibrated date are much broader (430-0 yrBP), making accurate calculation of pre-drainage sediment accumulation rates tenuous.

Pollen is abundantly preserved in sediments throughout both cores, typically comprising >10,000 grains g^-1. Two assemblage zones were identified in both core 03-9-16-3 and 03-9-16- 6, based on visual inspection of pollen diagrams and downcore changes in modern analogs (Figs. 5, 6). Raw counts of pollen from each sample are provided in Table 3 and Table 4. Pollen Assemblage Zone I is dominated strongly by Pinus pollen (>65%). Quercus pollen comprises <1% of assemblages, and the bulk of the remaining assemblage consists of marsh taxa including Cladium and Sagittaria (Figs. 5, 6).

In Pollen Assemblage Zone II, Pinus pollen is less abundant than in zone I (<60%); Quercus and Myrica pollen are more abundant, and pollen of the Poaceae, Cyperaceae, Asteraceae, and Amaranthaceae are more than twice as abundant as in zone I (Figs. 5, 6). Casuarina pollen is present throughout most of Zone II, and Quercus pollen reaches peak abundance in the uppermost samples.

Figures 5 and 6. Percent abundance of pollen of major plant taxa in sediment cores 03-9-16-3 (Fig. 5) and 03-9-16-6 (Fig. 6). Closest modern analogs were identified through comparison with modern samples using the modern analog technique and squared chord distance (SCD) as the dissimilarity measure. Samples with SCD<0.15 are considered to be close analogs. Double asterisks mark the first occurrence of Casuarina at 7.5 cm. Radiocarbon dates are reported either as calibrated years before present (cal yrBP) or pMC (percent modern carbon). Samples with >100 pMC are less than 50 years old and have more 14C than the 1950 AD reference standard; thermonuclear testing during the 1950s generated 14C, and organisms that lived after that time incorporated the "extra" 14C in their biomass, yielding results with >100 pMC. [larger image]