Sedimentary-edaphic Control Theory of Cyclic Sedimentation

Abstract

POLARITY coincidence correlation was recently applied to a lower Carboniferous sequence from the south of Scotland¹ in an attempt to establish the existence of “a fundamental cycle of about 145 ft. in the vertical change in sea level during the lower Carboniferous period in Great Britain”. Some of the geological assumptions made in order to carry out the mathematical analysis are of arguable validity, but of more immediate interest are the conclusions. The authors decided (page 137) that “isostatic readjustments … drive the cyclicity”. Many other writers^2–6 have appealed to “external” factors to account for cyclicity in Carboniferous sequences. On the other hand, “internal” mechanisms, such as normal sedimentary processes in a deltaic regime, have been invoked^7,8 to produce Yoredale-type cycles. It has also been shown quantitatively⁹ that the changes of environment evidenced in Coal Measures cyclic deposits are not regular, either vertically or laterally; and again a sedimentary control has been suggested.