Supplementary Table 3. Exclusion of datasets from deep ocean circulation analysis
Site Reason for exclusion in analysis
549 This site contains a 1 meter gap in carbonate sedimentation at the core of the CIE, rendering identification of the core of the CIE difficult. Anomalously low 13C persists throughout the recovery period. We believe that the isotope record is extensively overprinted. Additional data is needed in the post- excursion period to reliably identify the inflection point where values return to pre-excursion patterns.
577 Site 577 contains a hiatus through the CIE. Without a tie point for the core of the CIE, and with no data point available to identify the end of the recovery period, a reliable chronology could not be constructed
865 Site 865 contains only 4 points in the time interval of interest, and only one value in the CIE interval. The value is unlikely to be representative of the 13C plateau and probably represents a value in the recovery. An unpublished high- resolution stable isotope record of bulk carbonates suggests that this site is missing the entire plateau interval.
690 Benthic foraminiferal 13C data for Site 690 published by Thomas and Shackleton (1996) were excluded from this analysis (total = 28 data points, out of 91 published data points). These data were systematically offset towards more positive values (~0.5‰ to 1‰) from the data published by Kennett and Stott 1990, Stott et al., 1990 and Thomas et al, 2002. We note that exclusion of these data does not affect our conclusions and we highlight two observations: (1) Since the offset is towards more positive values, the inclusion of these data would increase the interbasinal aging gradient between the Southern Ocean and other basins during the pre-excursion and post-excursion values, supporting our interpretation of overturning in the Southern Ocean during these time intervals. (2) The Thomas and Shackleton data contain only 1 value during the carbon isotope excursion interval, and this value does not significantly lower the Site 690 13C average, or the Southern Ocean basin average for that interval. The inclusion of these data would not change our main conclusions, yet because of the uncertainty in the cause of the offset of this dataset compared to three other sources, we have chosen not to include these data in our deep ocean circulation analysis.
1221 Site 1221 contains a carbonate dissolution horizon in which dolomite rhombs compose a significant portion of the fine fraction. Some benthic foraminifera contained dolomite rhombs on their tests, although these specimens were not selected for carbon isotope measurements. Foraminifera below the carbonate dissolution horizon have a sugary surface texture. 18O values from the core of the CIE display an inverse pattern than that observed in all other PETM sites - 18O values become more positive. It is unlikely that these values represent true oceanic conditions, since the PETM is a time of ubiquitous global warmth. We attribute these unusual features in the stable isotope record of this site to diagenesis.
1258 The sediments in this site were partially lithified, and it was very difficult to obtain foraminifera free of matrix. The 13C values from this site also appear to be systematically shifted towards more negative values than any other deep sea site not only within the CIE but also before and after it. The P/E boundary in this site overlays black shales that have very negative 13C values owing to their high organic carbon content. These observations have led us to believe that some geochemical overprinting has taken place in foraminifera from this site, perhaps due to fluid flow above the black shale horizon. The record at Site 1258 does appear to record the same basic features of the 13C seen in some of the most complete records of the PETM, but given the poor fossil preservation and the consistent offsets from all other data sets, we regard the absolute values as suspect.