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Incorporating Information on Varying Sedimentation Rates Into Paleontological Analyses

The transformations between time and stratigraphic height underlying the DAIME model. The age model or sediment accumulation history (thick black line) connects stratigraphic heights with their time of deposition. A specimen deposited in the sediment at time 11.5 (filled circle) will thus be located at a stratigraphic height of 43 (filled triangle). When the location of a specimen is constrained by a stratigraphic bin, its time of deposition is constrained by the corresponding time bin obtained by transforming the endpoints of the stratigraphic bin (empty triangles) into time (empty circles). Accordingly any shell input in the sediment during a time bin (light gray area) is proportional to the shell content in the corresponding stratigraphic bin (dark gray area). This can be used to transform shell accumulation rates in time (dashed line) into shell abundance per stratigraphic height (dash-dotted line) and vice versa.

Is clustering of extinctions really an increase in extinction rate or is it merely generated by reduced sedimentation rates that reduce the spacing between individual extinctions with long breaks between each other? Niklas Hohmann, Paleobiology Master student, has examined this question in his Bachelor thesis, which is now published in PALAIOS (Hohmann 2021). The methods he developed are implemented for the R software and were previously applied in peer-reviewed publications (Jarochowska et al. 2020).
The novelty of this approach is that it allows for a quantification of the effects of sedimentary processes on paleontological interpretation. Using this principle, Niklas showed that a peak in extinction rate on Seymour Island, Antarctica, approx. 250 thousand years before the Cretaceous/Paleogene impact can be equally attributed to an increased extinction rate or an extended time interval with low sedimentation rate.

Hohmann, N. (2021). Incorporating Information on Varying Sedimentation Rates Into Paleontological Analyses. PALAIOS, 36(2), 53–67, https://doi.org/10.2110/palo.2020.038

Jarochowska, E., Nohl, T., Grohganz, M., Hohmann, N., Vandenbroucke, T. R. A., & Munnecke, A. (2020). Reconstructing depositional rates and their effect on paleoenvironmental proxies: The case of the Lau Carbon Isotope Excursion in Gotland, Sweden. Paleoceanography and Paleoclimatology, 35, e2020PA003979. https://doi.org/10.1029/2020PA003979