Time in the Rock: A field guide to interpreting past events and processes from a fragmentary siliciclastic archive

Abstract Converging research in modern environments, stratigraphy, numerical modeling, and physical experiments introduce new ideas and reinforce prior thinking on the complex and partial nature of the stratigraphic record. Through different vantages they each ask the question, ‘what does the rock record actually record?’ These studies show the stratigraphic record to be highly incomplete across multiple time scales. They focus new attention on the inverse relationship that was long ago demonstrated by Sadler (1981) between calculated sedimentation rates and the time span of the sections over which the measurements are made. Similarly, these studies note only parts of past processes and events make the final stratigraphic cut. Deep questions about the stratigraphic record remain. Which processes and events preserve? How are these processes and events recorded? What processes govern preferences for preservation of one deposit over another? What is the overall completeness of the stratigraphic recorded? In short, exactly how representative is the stratigraphic record of the geologic past? Despite all these caveats, stratigraphy still appears to preserve a robust record of past time and process. This paper explores current thinking on the sampling processes that build sedimentary deposits, controls on how much and what part of these deposits are preserved, and the interplay between autogenic and allogenic processes over the range of geological time scales. The paper offers a series of guidelines for field geologists attempting to interpret siliciclastic deposits in light of the evolving complex view and limited completeness for the stratigraphic record.