A library of early Cambrian chemostratigraphic correlations from a reproducible algorithm
The visual alignment of chemostratigraphic excursions enables correlation of sedimentary successions within the bounds of geochronology or biostratigraphy. This correlation facilitates the extrapolation of ages from radiometrically calibrated stratigraphic sections to others lacking temporal constraints. For Ediacaran and Cambrian applications, this practice commonly involves assigning ages to fossil first appearances, thereby resolving the tempo of early animal evolution. Chronologies, and the resulting evolutionary insights that they permit, frequently rely on the identification of a single, unique alignment between a time-calibrated and a time-uncertain section, yet visual correlation methods do not permit evaluating the uniqueness of such a chronology. Here we use a dynamic programming algorithm to determine a range of alignments between stratigraphic sections that are optimal under certain assumptions about total temporal overlap and sedimentation rates. We apply the algorithm to radiometrically calibrated Cambrian δ13Ccarb records to catalog a library of statistically significant and reproducible alignments. While a subset of the dynamic programming alignments support the statistical significance of published visual alignments, the remaining yield additional, significant correlation solutions that do not violate lithostratigraphic constraints. We conclude that the range of temporal inferences for fossil first appearances that arise from multiple chemostratigraphic alignments should be accounted for in assessing the timing of early Cambrian animal diversification.