DOI: 10.5061/dryad.4b8gthtgn
title: Spatial heterogeneity in benthic foraminiferal assemblages track regional impacts of paleoenvironmental change across Cretaceous OAE2

description: The impact of global climate events on local ecosystems can vary
 spatially. Understanding this heterogeneity can illuminate which
 environments will be most impacted and the proximal drivers of ecosystem
 responses. Cenomanian-Turonian marine deposits of the Western Interior
 Seaway (WIS) record paleoceanographic changes associated with
 transgression and the onset of Oceanic Anoxic Event 2 (OAE2). They provide
 an ideal setting to study basinwide paleoecological responses during a
 global perturbation. Here, we integrate benthic foraminiferal assemblages
 from before, during, and after OAE2 via multivariate ordination analysis
 to examine spatial patterns in faunal responses across the western United
 States on a common scale and to interrogate a previously defined faunal
 marker used for basin-wide correlation, the Benthonic Zone (BZ). We
 identify oxygenation and organic matter quality as primary and secondary
 controls of variation across the 10 stratigraphic records and use this
 variation to infer paleoenvironmental changes. Stratigraphic trends
 reveal, in contrast to previous studies, deoxygenation at the onset of
 OAE2. They also reveal temporal patterns in oxygenation and productivity
 consistent with the gradual northward migration of a southern water mass
 into the WIS. This spatial heterogeneity hinders the use of the BZ in
 biostratigraphy because assemblages change in response to diachronous
 environmental change, and thus timing of the BZ with respect to OAE2 is
 not consistent across the basin. Our study demonstrates that regional
 processes can overshadow ecosystem responses to global events and
 underscores the importance of considering how changes in the position of
 water masses impact the expression of global biogeochemical perturbations.
description: Main data file: Proportional abundances for this study were
 obtained from Elderbak et al 2014, Lowery et al. 2014, and Bryant et al.
 2021. Additional data from Eicher and Worstell (1970) was manually
 digitized, and some data were converted from original categorical
 abundances (Abundant, Common, Rare) to estimated proportional abundances
 based upon the category the taxa were assigned to by the original authors
 and the number of taxa in each category in each sample. See Bryant and
 Belanger (associated publication) for details of this data conversion. All
 data sets were taxonomically standardized and proportional abundances were
 normalized to 100% before multivariate analysis. Each species was also
 assigned a morphotype (see Bryant and Belanger for details of the
 assignments) in order to perform the morphotype-level multivariate
 analysis. Supplementary materials included: three
 supplementary figures and six supplementary tables. 
description: The file is .csv and can be opened and edited with Microsoft
 Excel and can be processed in R studio. Supplementary
 figures 1–3 are included in one .pdf file. Supplementary tables 1, 3, 4,
 and 6 are included in one .pdf file, while supplementary tables 2 and 5
 are in individual tabs of one .xlsx file.