Time, Order, and Stratigraphy: Exploring the Effects of Missing Time in the Identification of Ordered Patterns in the Stratigraphic Record

Monday, 15 December 2014
David Lee Oliver, California State University Fresno, Earth and Environmental Sciences, Fresno, CA, United States and Mara e Brady, California State University Fresno, Earth & Environmental Science Dept, Fresno, CA, United States
Detection of cyclical drivers of stratigraphic patterns aids in the reconstruction of paleoenvironments and the identification of potential hydrocarbon reservoirs. Statistical analysis of lithofacies stacking patterns is a common approach, and often focuses on the question of whether the observed patterns can be distinguished from those generated by random processes, which offers the potential of extrapolation into a predictive framework. The observed sedimentary record can be fragmented by a variety of issues, such as covered sections in outcrop, broken sections on cores, dolomitization, or recording errors from geophysical equipment. This missing data represents unobserved time in the record, and understanding how this missing time affects our observations can enhance our ability to reconstruct a basin’s history. Synthetic stratigraphic sections of known history are generated by Dougal, a previously developed 1-D carbonate forward numeric model, and used to explore the effects of cover, or fragmentation of the record, in the analysis of observed stratigraphic sections. Each synthetic stratigraphic section is covered in increments of 5% of the total thickness, and examined under a variety of styles ranging from a singular thick to numerous thin intervals. Covered intervals are distributed as clustered or evenly spaced across the whole stratigraphic section. Results indicate a general decrease in the degree of observed order in the stratigraphic columns as the proportion of cover increases. Within each increment, the style with a singular thick covered interval demonstrated the lowest degree of order, and the stratigraphic sections with two evenly spaced and equally thick covered intervals demonstrated the highest order. These results show how the proportional quantity and distribution of missing data can affect the identification of ordered patterns in the rock record. This work can provide guidelines for the analysis of covered intervals in stratigraphic sections.