Article: Time in stratigraphy

Recent publication of several formalized systems of stratigraphic classification and nomenclature provides an opportunity for the re-assessment of certain stratigraphic concepts.The scope and categories of stratigraphic studies are examined and related to the nature of the chronological record available in extant rocks. Lithostratigraphic data are identified as the matrix of a body of biostratigraphic evidence which serves as the basis for construction of a model time-scale using biochronological divisions. The notion of a separate 'time-stratigraphy' with 'time-stratigraphic' units is considered to be invalid.The nature of stratigraphic boundaries in relation to diastrophic processes, the general nature of stratigraphic divisions, and the special status of the biochronologic zone are discussed, together with problems of correlation.