This article by Timothy Gallagher and Nathan Sheldon presents a new approach for reconstructing terrestrial temperatures using fossil soils. The approach is based on the principle that, as temperature increases, certain elements are more easily weathered and subsequently lost from a soil. Gallagher and Sheldon compiled modern forest soil data to derive a specific relationship between bulk soil chemistry and mean annual temperature. The relationship was then applied to previously published chemistry data from fossil soils in Oregon that span the past forty million years. In addition to validating the relationship with modern soils in the same region, Gallagher and Sheldon were able to produce a terrestrial temperature record that was in general agreement with the regional fossil plant record. A temperature drop of almost 3 degrees C was recorded for the Eocene‐Oligocene greenhouse‐icehouse transition, and the maximum temperature of the Neogene was recorded during the Mid‐Miocene Climatic Optimum, a global warm climate event. The new terrestrial temperature record was also compared to general warming and cooling trends originally identified from marine sediments. This comparison demonstrated that over the past forty million years, marine and terrestrial temperature trends in Oregon were both similar and synchronous, suggesting strong climate coupling between the marine and terrestrial realms.
Holocene scarp on the Sawtooth fault, central Idaho, USA, documented through LiDAR topographic analysis
Glenn D. Thackray et al., Department of Geosciences, Idaho State University, Pocatello, Idaho 83209, USA. Published online ahead of print on 16 April; http://dx.doi.org/10.1130/G34095.1.
The Sawtooth Fault near Stanley, Idaho, has been identified as
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Geological Society of America