176-14 Exploring the effects of taphonomic destruction and time-averaging on size-frequency distributions and paleoenergetic metrics

Session: Laws of the Grave: Advances in Taphonomy Across the Paleontologic Record

Presenting Author:

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Abstract:

A growing body of palaeoecological studies suggests long-term gradual or stepwise increases in the mean per-capita energy content and energetic requirements of marine animal taxa and ecosystems through the Phanerozoic. These paleoenergetic conclusions rest largely on trends in the taxonomic composition, trophic structure, and size-frequency distributions of fossil assemblages. Paleoenergetic metrics derived from fossil or death assemblages differ fundamentally from energetic metrics derived from living assemblages in three key respects: (1) death assemblages are time-averaged, (2) death assemblages represent only a small, nonrandom subset of the living assemblages from which they derive, and (3) individuals in death assemblages have by definition completed their lifespans, so that production/biomass ratios are always 1 (Powell et al., 2001). Even when limiting comparisons to the subset of taxa with relatively high preservation potential several studies have documented elevated rates of shell destruction among small size classes, producing death assemblage size-frequency distributions that are much less right-skewed and have much larger median sizes than living assemblages. Thus it remains unclear how well we should expect death assemblages to record energetic gradients across living assemblages. I will use transition matrix models to explore the predicted effects of taphonomic filtering and time-averaging on paleoenergetic metrics such as mean per-capita paleoproduction and paleoproduction transfer efficiency, and to determine the conditions under which energetic gradients in living assemblage are and are not preserved in death assemblages.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11282

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