Abstract

Computer modeling of the distribution of fossils within depositional sequences provides a means for generating hypotheses and increasing understanding of the fossil record. The simulation presented here joins the basin-scale stratigraphic modeling program STRATA, a random-branching model of species origination and extinction, and a model relating the probability of species occurrence to sedimentary facies. Model results indicate that facies sensitivity of species has the strongest control on range offset, i.e., the time between last appearance in a stratigraphic column and the time of extinction within a basin or the time between first appearance in a column and time of origination in a basin. Model results also predict the distribution of zones of increased range offset within depositional sequences. In the results presented here, increased range offset occurs within the transgressive systems tract of the deep basin, in far updip settings, and near the shelf break of the late highstand to early lowstand. The model also demonstrates how incompleteness of the fossil record is partitioned among sampling bias, facies bias, and unconformity bias. In this simulation, sampling bias and facies bias are roughly equal in magnitude and constant across the basin, but unconformity bias increasingly dominates over these two in updip positions.

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