Homotaxial stratigraphy

Abstract

It has been argued recently by Woodford that fossils allow stratal units deposited during a specific interval of time to be distinguished from those that simply occur in unique order (homotaxis). This distinction is here criticised because the only practical test procedure using- fossils is observation of their stratigraphic order, which does not allow the specific interval of time mentioned in definitions of time-stratigraphic units to be identified. Stratal units defined by invariant sequences of fossils should be called homotaxial stratigraphic units, and “time-stratigraphic” should be restricted to units defined by radiometric techniques. In this way, names of stratal categories can be related to practical methods of testing the truth of included members.