Chapter 13
Paleocurrents from FMS and Scribe-oriented Core--A Comparison

Tobias H. D. Payenberg1
School of Natural Resource Sciences
Queensland University of Technology
Brisbane, Queensland, Australia

ABSTRACT

Paleocurrents were interpreted from cross-stratified beds identified on Formation MicroScanner (FMS)² images and from four depth-matched, scribe-oriented sandstone cores. The results were compared to document the extent of similarity; results varied greatly. In some cases, paleocurrent data differ widely between cores and FMS images, with absolute azimuth-vector means being opposed by as much as 180 degrees. In one of the four cores, the azimuth difference was almost 110 degrees, but the lower part of the sandstone shows consistent readings in both data sets. Azimuths and magnitudes of dip in the lowermost sandstone match well, with an absolute azimuth difference of only 6 degrees. In the three of four intervals where azimuth readings differ significantly, dips inferred from FMS images are on average 10 degrees less than dips of foreset beds measured in cores. In these intervals, circular standard deviations of FMS azimuths also are higher than those measured in oriented cores from the same depth intervals.