256-14 Linking Low-Oxygen Events across the Eastern North Pacific using Benthic Foraminiferal Faunal Responses

Session: Life and Environments Through Time and Space: Multi-Record Approaches to Stratigraphic Paleobiology, Part I

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Abstract:

Global climate events are uniquely expressed in different locations. Understanding the variation of paleoecological responses in space, and thus, the sensitivity of different ecosystems to climate perturbations, requires integration of multiple sedimentary timeseries. By co-analyzing taxonomically-standardized benthic foraminiferal faunal records from four sedimentary cores from oxygen minimum zone (OMZ) sites in the North Pacific, we were able to place faunal responses to the last deglaciation on a common multivariate scale. This revealed that abrupt low-oxygen events in the Gulf of Alaska (GoA) during glacial and deglacial times were as severe as the events in the more typically dysoxic Santa Barbara Basin and Baja California Sur. The timing of dysoxic events also appear synchronous across locations, but were shorter in duration in GoA. This led us to infer that the northward advection of low-oxygen waters from the Eastern Tropical North Pacific via the California Undercurrent could be driving these events, which only reached GoA when advection was the strongest.

Combining multiple records also requires that we know whether different sedimentary records, with their different sedimentation rates, sampling resolutions, and scales time averaging, are capable of detecting the same events. For the GoA record, sedimentation rates as high as 50 cm per thousand years facilitated the preservation of the abrupt low-oxygen events even though they were shorter in duration than at the more southern localities. Further, the end member faunal compositions at GoA are very distinct given that background conditions at the site are typically well-oxygenated in comparison to the suboxic baselines of the other sites, which make the dysoxic events more easily recognizable in GoA. We developed assemblage-mixing simulations that allow researchers to assess whether the faunal assemblage records they wish to compare have the potential to capture their target events given the potential differences in sedimentation rate, sampling strategy, and assemblage structure. We are currently expanding the application of these methods by databasing published benthic foraminiferal timeseries from around the globe to test for spatial and temporal variability in palaeoecological responses to glacial-interglacial transitions.

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

doi: 10.1130/abs/2025AM-7205

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