When the cores are returned to the lab, they are split in two halves. One-half of the core is sampled and the other half is archived for future use. The core that was sampled from Lake
Chichancanab had a total length of 4.9 m with a basal radiocarbon age of 9000 years BP. The sedimentation rate averaged about 0.5 mm per year. The core was sampled continuously at 1-cm intervals over its length. A 1-cm sample in the Lake Chichancanab
core represents about 20 years of deposition. The sedimentation rate determines the temporal resolution of study and as a result, scientists are able to reconstruct climatic changes that lasted for multiple decades or longer. The sediments
of Chichancanab consisted of alternating layers of organic matter, calcite, and gypsum.
The total core length from Punta Laguna was 6.3 m with a basal age of 3300 years. The sedimentation rate averaged 2 mm/year, which is about four times
greater than the sedimentation rate in the core from Chichancanab. A 1-cm sample for the Punta Laguna core represents only 5 years of deposition, permitting the resolution of much shorter climatic events. Sediments in the Punta Laguna core are
composed almost entirely of calcium carbonate(CaCO3).
David A. Hodell
Department of Geology, University of Florida
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