Figure
3: Top: Δ47-temperature relationship for all 108
freshwater carbonates included in this study. Black line represents a
linear, ordinary least squares regression through the data and the gray
shaded area represents the 95% confidence interval. We find a strong
relationship between Δ47 and temperature(p
<0.0001; r2 = 0.8959). Red diamonds
represent low temperature and/or high pH lacustrine microbialites from
Anderson et al. (2021) that have been excluded from the regression.Bottom: Comparison of our composite freshwater regression to
previously published clumped isotope calibrations. ANCOVA results show
that the slope derived for our calibration is statistically different
from the acid corrected calibration of Petersen et al. (2019) and
Anderson et al. (2021), with pslope values of 0.0036 and
0.0334, respectively (Table 3). Our calibration yields higher
temperature estimates than Anderson et al. (2021) in the range of
natural carbonate growth, but similar temperatures to Petersen et al.
(2019) (Supplementary Table 3).