Tracing energy inputs into the seafloor using carbonate sediments

Carbonate rocks provide unique and valuable sedimentary archives for secular changes in Earth's physical, chemical, and biological processes. However, reading the stratigraphic record produces overlapping, nonunique interpretations that stem from the difficulty in directly comparing competing b...

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Bibliographic Details
Published in:	Proceedings of the National Academy of Sciences - PNAS 2023-02, Vol.120 (9), p.e2215833120-e2215833120
Main Authors:	Smith, B P, Edie, S M, Fischer, W W
Format:	Article
Language:	eng
Subjects:	Animal behavior Animals Biological activity Biological Evolution Bioturbation Carbonate rocks Carbonate sediments Carbonates Carbonates - analysis Chemical analysis Chemistry Geologic Sediments Marine environment Mass extinctions Mathematical models Ocean floor Oceans Oceans and Seas Paleozoic Permian Perturbation Physical Sciences Reduction Seawater Sediments Species extinction Stratigraphy Triassic Water - analysis
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Summary:	Carbonate rocks provide unique and valuable sedimentary archives for secular changes in Earth's physical, chemical, and biological processes. However, reading the stratigraphic record produces overlapping, nonunique interpretations that stem from the difficulty in directly comparing competing biological, physical, or chemical mechanisms within a common quantitative framework. We built a mathematical model that decomposes these processes and casts the marine carbonate record in terms of energy fluxes across the sediment-water interface. Results showed that physical, chemical, and biological energy terms across the seafloor are subequal and that the energetic dominance of different processes varies both as a function of environment (e.g., onshore vs. offshore) as well as with time-varying changes in seawater chemistry and with evolutionary changes in animal abundance and behavior. We applied our model to observations from the end-Permian mass extinction-a massive upheaval in ocean chemistry and biology-revealing an energetic equivalence between two hypothesized drivers of changing carbonate environments: a reduction in physical bioturbation increased carbonate saturation states in the oceans. Early Triassic occurrences of 'anachronistic' carbonates-facies largely absent from marine environments after the Early Paleozoic-were likely driven more by reduction in animal biomass than by repeated perturbations to seawater chemistry. This analysis highlighted the importance of animals and their evolutionary history in physically shaping patterns in the sedimentary record via their impact on the energetics of marine environments.
ISSN:	0027-8424 1091-6490