ABSTRACT

Stratigraphic changes in the clustering of first or last taxon occurrences are a joint expression of evolutionary, ecological, taphonomic, and sedimentological processes. Sedimentation rates control the degree of sedimentary dilution and condensation and thus alter the time contained in a given thickness of sediment. However, it remains poorly explored quantitatively how distinct the stratigraphic patterns in the first and last occurrences can be under different deposition models with a constant thickness of accumulated sediment. Here, I present an algorithm that translates ecological or evolutionary signals between time and stratigraphic height. It is implemented for R Software as the package DAIME and complemented by tools to quantify the uncertainties associated with the construction of deposition models. By modeling the stratigraphic expression of the K/Pg extinction and an earlier extinction pulse potentially linked to Deccan volcanism on Seymour Island under varying sedimentation rates, I show that (1) clustering of last occurrences ∼ 250 kyr prior to the K/Pg boundary can be equally explained by a stronger earlier extinction pulse or prolonged intervals with reduced sediment accumulation rate, but (2) when the temporal variability in sedimentation rate is known, the most plausible extinction dynamics can still be identified. The approach is applicable for any type of information transported as a part of the sedimentary record (e.g., fossils or trace elements) or data derived from it (e.g., isotope ratios and rates of morphological evolution).

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