Strata and time

David G. Smith, R. J. Bailey, P. M. Burgess, A. J. Fraser

The superposition of stratified rocks is an unmistakable manifestation of the history of sedimentary processes through deep time. However, the relationship between the preserved strata of the rock record and the passage of geological time, indisputable in principle, is unknowable in detail; incompleteness is an essential property of the record. That gaps exist at all scales in sedimentary successions is easily demonstrated from consideration of sediment accumulation rates, and expectations of continuity and completeness at any scale are correspondingly inadvisable. Locating and quantifying the gaps in the record is, however, very much less straightforward. Predictive modelling of strata - essential for their practical exploitation - requires such geohistorical understanding, yet over-simplified assumptions about how time is represented in rock can still lead to inadequate or even...