Sampling and Analyzing Method: Acarininid shells were cast in epoxy, ground to midsection and imaged by SEM to identify suitable, well-preserved domains for analysis. In situ d18O data were acquired in the WiscSIMS Laboratory at the Department of Geoscience, UW-Madison, using a CAMECA IMS-1280 large radius multicollector SIMS. (Kita et al., 2009; Valley and Kita, 2009). Depending on the size of the target, samples were analyzed with a 10 µm or 3 µm primary beam. Four consecutive measurements of UWC-3 calcite standard (d18O = 12.40 per mille Vienna standard mean ocean water; VSMOW; Kozdon et al., 2009) were performed before and after every set of typically 10 sample analyses.