This data release contains all new glassy-only single-test stable isotope data from International Ocean Discovery Program (formerly Ocean Drilling Program) Sites 846 and 929, in addition to image plates containing photographs of every Cibicidoides test analyzed. This dataset and associated plates are part of a larger manuscript, which will be submitted for consideration to the journal Nature in May, 2026. Data were collected only from individual glassy Cibicidoides tests, meaning they are very well-preserved and are likely not impacted by post-depositional isotope exchange (i.e., diagenesis). Data were collected from Ocean Drilling Program (currently International Ocean Discovery Program) Sites 846 and 929 to compare to their published, pooled-test stable isotope records. Because the published pooled-test records likely required 3-10 tests per analysis, and because it is highly unlikely that many samples from these and other deep-sea sites regularly contain 3-10 glassy tests (Poirier and others, 2021), any offsets between the new glassy only records and the published records from each site demonstrate that the latter are biased by diagenesis. As these two records have been included in every iteration of global benthic d18O stack to date, these results demonstrate that these stacks are also biased by diagenesis. The manuscript associated with this dataset discusses these topics in more detail, while also modeling the proportion of records within the stacks are biased comparably to Sites 846 and 929. This dataset serves as a public means to release all of the new data, while also providing an accessible location for the images of every test that was analyzed. Citation: Poirier, R.K., Gaetano, M.Q., Acevedo, K., Schaller, M.F., Raymo, M.E., & R. Kozdon (2021). Quantifying diagenesis, contributing factors, and resulting isotopic bias in benthic foraminifera using the foraminiferal preservation index: Implications for geochemical proxy records. Paleoceanography & Paleoclimatology, 36(5), p.e2020PA004110.
