The clumped isotope geothermometer in soil and paleosol carbonate

Abstract

We studied both modern soils and buried paleosols in order to understand the relationship of temperature estimated from clumped isotopes in carbonates (T°C_(clumped)) to actual surface and burial temperatures. Carbonates from modern soils in a broad range of climates were sampled from Arizona, Nevada, Tibet, and India. T°C_(clumped) obtained from these soils shows that soil carbonate only forms in the very warmest months of the year, largely in the afternoon, and probably in response to intense soil dewatering. The highest T°C_(clumped) obtained from modern soil carbonate are <40°C On average, T°C_(clumped) significantly exceeds mean annual temperature by 10-15°C due to (1) summertime bias in soil carbonate formation, and (2) sensible heating of soil. Secondary controls on T°C_(clumped) are site aspect, but especially soil depth and shading.

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