### 3.2 Contamination
The results for all samples measured as part of this study are included in Table 1 and plotted in Figure 3(a) and (b). Figure 3(a) is a plot of $\Delta_{48}$ *versus* $\Delta_{47}$ whilst Figure 3(b) is a plot of
$\Delta_{49}$ *versus* $\Delta_{47}$.
$\Delta$ values for the room temperature (20$^\circ$C) equilibrated gas, *BDHequilRT*, measured over the duration of this study are tightly clustered with $\Delta_{47}$ = 0.021 $\pm$ 0.010‰, $\Delta_{48}$ = 0.06 $\pm$ 0.05‰ and $\Delta_{49}$ = -14.16 $\pm$ 10.0‰. Similarly, the carbonate standard *UEACMST* determined using the three different porapak trap designs are tightly clustered with $\Delta_{47}$ = -0.412 $\pm$ 0.008‰, $\Delta_{48}$ = 0.05 $\pm$ 0.05‰, and $\Delta_{49}$ = -11.0 $\pm$ 9‰. There is no evidence for a dependence of the *UEACMST* data on trap configuration, Figure 3(a) and (b). Neither is there any correlation  of the clumped isotope values for either the *BDHequilRT* or *UEACMST* standards.
In contrast results obtained for the *UEAOES*, *UEATHC* and *UEABEL* standards show both variable behaviour dependent on the trap design used and a marked correlation between the clumped isotope values for a particular sample.
 When using the initial 21cm porapak trap (trap 1) at temperatures between -20 and -30$^\circ$C the $\Delta$ values we report for *UEAOES* are $\Delta_{47}$ = -0.205 $\pm$ 0.009‰, $\Delta_{48}$ = 0.01 $\pm$ 0.03‰ and $\Delta_{49}$ = 38 $\pm$ 44‰ (n = 6). On switching to the shorter 7cm porapak trap (trap 2) the results became highly variable with $\Delta_{47}$ varying between -0.198 and +0.389‰ (n = 7). Moreover the $\Delta_{47}$ values are strongly correlated with both $\Delta_{48}$ and $\Delta_{49}$, Figure 3(a) and (b). $\Delta_{48}$ ranges between +0.07 and +2.73‰ and $\Delta_{49}$ between -27 and +389‰. The most extreme $\Delta$ values correspond to sample measurements in which a noticeable non-condensable gas load was reported after the intial isolation of the CO~2~ from the reaction vessel implying a small atmospheric leak during the reaction step. On returning to a longer 24cm porapak trap operated at -20$^\circ$C (trap 3) the results stabilised at $\Delta_{47}$ = 
References
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Eiler, J. M., & Schauble, E. (2004). ^18^O^13^C^16^O in Earth's atmosphere. Geochimica et Cosmochimica Acta, 68(23), 4767–4777.
Petersen, S. V., Winkelstern, I. Z., Lohmann, K. C., & Meyer, K. W. (2016). The effects of Porapak™ trap temperature on $\delta^{18}$O, $\delta^{13}$C, and $\Delta_{47}$ values in preparing samples for clumped
isotope analysis. Rapid Communications in Mass Spectrometry, 30(1),
199–208. http://doi.org/10.1002/rcm.7438