ABSTRACT

A comparative study was made of two rhythmically stratified argillites in the Huronian Cobalt Series (Precambrian) of Canada. The rocks belong to the Gowganda Formation, which is believed to be of glacial origin.

The rocks were studied in thin section, and a continuous sequence of couplets from each outcrop was measured and subjected to power-spectrum analysis to detect any significant cyclic fluctuations in couplet thickness which might be present. Whereas no statistically significant periodicities were found, the sequences gave strikingly different power spectra; these are interpreted in the light of physical differences between the two argillites and their possible conditions of deposition. It is concluded that in both cases the sediments were derived primarily from seasonal influxes of glacial meltwater and floating ice and that the contrasts between the two argillites may be due to the presence or absence of turbidity current activity, to different annual rates of deposition, and to other factors.