2007 GSA Denver Annual Meeting (28–31 October 2007)

Paper No. 6
Presentation Time: 1:30 PM-5:30 PM


BAHR, Leah M., Geological Sciences and Engineering, University of Missouri-Rolla, 125 McNutt Hall, 1870 Miner Circle, Rolla, MO 65409, HOGAN, John, Geological Sciences and Engineering, University of Missouri-Rolla, 127 McNutt Hall, Rolla, MO 65401 and ATEKWANA, Eliot, Boone Pickens School of Geology, Oklahoma State University, 105 Noble Research Center, Stillwater, OK 74078, lmbm88@umr.edu

A stalactite collected from a concrete structure near Gweru Zimbabwe, South Africa was investigated to better understand growth mechanisms for stalactites. The sample is composed of relatively concentric rings, alternating between light brown and dark brown in color. These differences have been attributed to reflect growth during the “wet” and “dry” seasons in Gweru. The petrographic microscope was used to characterize the nature of the rings and to count the rings in an attempt to determine the stalactite's age. Physical characteristics of individual layers, such as crystal form, indicate these layers preserve a more complex growth history than simply recording seasonal changes. It is suggested that each ring is related to separate significant rainfall events during the wet season with no deposition during the dry season. Stalactite rings thus provide a good record of past rainfall activity and will require other methods to establish the calendar age of rings.