Volumetric measurement of fossil charcoal: Principles, applications and potential

Abstract

Quantifying sedimentary charcoal content by estimation of volume from two-dimensional images is a relatively new and little-used method, but has the potential to improve the accuracy of fire histories. It requires a power transformation of area data, and multiplication by a coefficient to account for particle shape. The latter step has been routinely overlooked, or considered unnecessary, with volume estimates made simply by power transformation of the area data. Some researchers have used the method on the basis of the power transformation only, and others have rejected it as unnecessary on the same basis. However, the assumption that the shape coefficient can be ignored is likely to introduce very large errors, resulting in overestimation of charcoal volume. The magnitude of the error is indicated by a limited amount of empirical data obtained from volumetric measurement of individual charcoal particles, and accurate use of the method would require considerable further work to extend this data set. In a sedimentary sequence where particle morphology varies with depth, the errors identified could seriously distort the fire history produced. However, as such variation is easily identified, the method can still improve charcoal quantification where morphology is stationary.