HR: 1340h
AN: PP43A-0998    [Abstracts]
TI: Speleothem Paleoclimate Records from the Floridian Panhandle
AU: * Froelich, P N
EM: froelich@magnet.fsu.edu
AF: Department of Oceanography, NHMFL-Geochemistry, Florida State University, 1800 E. Paul Dirac Dr., Tallahassee, FL 32310,
AU: Kowalczk, A J
EM: akowalczk@magnet.fsu.edu
AF: Department of Oceanography, NHMFL-Geochemistry, Florida State University, 1800 E. Paul Dirac Dr., Tallahassee, FL 32310,
AU: McCardle, D
EM: Donald.Mccardle@HCAhealthcare. com
AF: CT Imaging Department, Capital Regional Medical Center, 2626 Medical Blvd., Tallahassee, FL 32308,
AU: Tibbetts, N
EM: tibbetts@magnet.fsu.edu
AF: Department of Geological Sciences, NHMFL-Geochemistry, Florida State University, 1800 E. Paul Dirac Dr., Tallahassee, FL 32310,
AB: Geochemical time-series constructed from speleothem records provide a high resolution view into paleoclimate conditions temporally unmatched by deep ocean sediment and ice core records. The potential of speleothem records is vast with immense spatial and temporal resolution. One surprise to the speleothem paleoclimate community is the absence of high resolution speleothem isotope and trace element records from Florida, an area of extensive karstic geology, a plethora of caves, and monsoon-like climate. Two stalagmites collected from Brooks Quarry Cave, recently opened in Marianna, FL will provide one of the first Holocene speleothem climate records from the Southeast. Speleothem BC-1 is a 71 cm calcite stalagmite collected in situ. Speleothem BC-2 is a 6.1 cm stalagmite collected inside the quarried entrance to the cave. Both dripstones are banded and laminated at what appear to be 11-year cycles (dating in progress). If these are annual "sparves" (speleothem varves), the growth rates are approximately 100 μm per year. BC-1 would extend through much of the Holocene. RGB scans along the polished length of the growth axis reveal color cyclicity related to bundles of these bands. Isotope records from BC-2 reveal a multi-year record showing a variation of -2.7 ‰ to -6 ‰ in δ¹⁸O and -3.7 ‰ to -9.1‰ in δ¹³C, with no correlation between the two. High resolution multi-element laser ablation scans across 8 "sparves" (2.3 mm length) reveals co-variation in U and Ba with other elements showing weaker banding correlations with "clays" (Si, Fe, Mn, Ce, Rb). Photomicrographs of the laser tracks show correlation of visible "sparves" to chemical variations. Medical CT imaging techniques were applied to sample BC-1using a GE Lightspeed Plus CT scanner at maximum power (140 kV, 565 mA) and medium resolution (0.6 mm per scan slice) to view density differences and pore spaces inside the calcite matrix. CT technology reveals a porous nature of the calcite matrix in the lower 35 centimeters with abundant fluid and air inclusions, while the upper 36 centimeters consist of a denser, non porous calcite matrix with a ring of dissolution features on the outer rind. A biomedical video of the longitudinal stacked scans will be presented during the talk to describe internal features that are otherwise invisible. This tool may routinely guide speleothem selection for paleoclimate studies, and imaging of internal dripstone structures prior to open-rock surgery.
DE: 4914 Continental climate records
DE: 4924 Geochemical tracers
DE: 4958 Speleothems
DE: 4994 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting