Marine Science Faculty Publications

Siderite ‘clumped’ Isotope Thermometry: A New Paleoclimate Proxy for Humid Continental Environments

Document Type


Publication Date


Digital Object Identifier (DOI)


Clumped isotope measurements can be used to exploit the paleoclimatic potential of pedogenic siderite (FeCO3); however, the applicability of this method is held back by the lack of clumped isotope calibrations of mineralogies other than calcite and aragonite. Here we present an inorganic calibration of siderites grown in the laboratory between 21 and 51 °C. Linear regression of Δ47 values and temperature (106/T2, K) yields the following relationship (r2 = 0.997):Δ47-RF=(0.0356±0.0018)×106T2+(0.172±0.019)">Δ47-RF=(0.0356±0.0018)×106T2+(0.172±0.019)

We demonstrate that this calibration is indistinguishable from calcite at current levels of analytical precision. Our observations suggest that there is likely no large systematic bias in the clumped isotope acid fractionation factors between the two different carbonate minerals. We also present clumped isotope measurements of a natural siderite collected from Holocene sediments of the Mississippi River Delta. We find that siderites record warm season marsh water temperatures instead of mean annual temperatures as it has long been presumed. This finding has important implications for the accuracy of siderite stable isotope and clumped isotope based climate reconstructions.

Was this content written or created while at USF?


Citation / Publisher Attribution

Geochimica et Cosmochimica Acta, v. 126, p. 411-421