Weimer, Lisa M.
Bernhardt, Christopher E.; Weimer, Lisa (deceased); Gamez, Desire; Cooper, Sherri R.; Jensen, Jennifer
Weimer, Lisa M.; Riegel, W. L.
Reimer, P. J.; Bard, E.; Beck, J. W.; Burr, G. S.; Hughen, K. A.; Kromer, B.; McCormac, G.; van der Plicht, J.; Spurk, M.
Webb, III, T.; Prentice, I. C.
The cores were selected for analysis based on the x-rays. Those cores selected for further analysis were selected on the basis of laminations or other features which indicated the lack of disturbance. The core was placed in an extruding device vertically. The core was then extruded up into a template and sliced. This slice (hockey puck) was placed on a preweighed titanium plate and the wet weight determined. The ring was then removed and the slice was trimmed to remove the outer portion of the core. This was done to prevent any contamination that may have occurred at the side of the core barrel during the coring operation. This sample was then bagged and weighed. This weight was found to be important in the determination of water content and thus the dry weigh as water was lost during the period of initial sampling and the laboratory analysis. These sample were then stored in a refrigerator and then transhipped to the home based laboratory. For those core selected for trace metal analysis, the slices were sampled from the center of the "hockey puck" with titanium tools and place in an acid washed plastic bottle and frozen.
Approximately 50 short cores were planned to be collected for analysis of flora, faunal, and charcoal abundances. The cores were dated using 210Pb and 14C. Additionally, pollen, plant macrofossils, and invertebrate faunas were analyzed from surface samples. These samples were collected from sites throughout the region to maximize representation of modern plant communities. The resulting data provided the basis for comparison with down-core assemblages to determine how much change in vegetational distribution has occurred.
Pollen and spore identification (minimally 300 grains per sample) was based on reference collections of the U.S. Geological Survey (Reston, Virginia). Pollen sums were based on abundance of all identifiable taxa. The interpretations of past plant communities are based on the quantitative method of modern analogues (Overpeck et al. 1985). The squared chord distance (SCD) between down-core pollen assemblages and a suite of 197 surface samples collected throughout southern Florida in the early 1960s and 1995 to define the similarity between each fossil and modern pollen assemblage. Internal comparison among surface samples from 10 vegetation types indicates that samples with SCD values approx. 0.15 may be considered close analogues (Willard et al. 2001). If analogues were present for a fossil assemblage, the source vegetation for the fossil assemblage was identified as one of the 12 types represented in the modern database. Cores were divided into pollen zones based on a combination of visual inspection, objective zonation using CONISS (Grimm 1992), and modern analogues.
U.S. Department of the Interior, U.S. Geological Survey
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