99-9 Drivers of Low and Variable Bioturbation through the Cambrian–Ordovician Transition in the Arrow Canyon Range, NV, and the Ibex area, UT

Session: Evolution of Life in the Cambrian Seas: Biotic, Biogeochemical, and Sedimentological Contexts, Part I

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Abstract:

Bioturbation, or the mixing of sediment by burrowing animals, is widespread, intense and encompasses a range of behaviors across the modern seafloor. However, in the early Paleozoic, bioturbation intensity lagged behind other ecological innovations, despite the emergence in the early Cambrian of metabolic capabilities that permitted vertical burrowing and extensive infaunalization. However, the drivers of this lag in the rise of intensive sediment mixing remain debated. The Cambrian–Ordovician transition serves as a case study for how the dynamic environmental and ecological conditions of the early Paleozoic impacted seafloor animal communities, including bioturbators. High-resolution sampling and statistical analyses of sedimentology and bioturbation across this interval in Laurentian strata of the Arrow Canyon Range, NV, and the Ibex area, UT, reveal that bioturbation did not increase unidirectionally and instead varied substantially through time and between regions. Our data corroborate previous findings that bioturbation remained relatively low during this interval. In the Arrow Canyon Range, we find that bioturbation is elevated in particular facies and depositional settings (i.e., fine-grained carbonates and strata recording muddy peritidal paleoenvironments). In contrast, we observe no statistically significant correlations between bioturbation and the same factors in the Ibex area, which emphasizes the importance of local conditions in shaping bioturbation. We attribute this inter-regional disparity in bioturbation to the greater environmental variability of the Ibex region, and potentially to associated environmental shifts in the coupled impact of hydrodynamic energy and seawater oxygenation in shaping seafloor habitability and bioturbator activity levels. 

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

doi: 10.1130/abs/2025AM-8895

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