Biomarkers heat up during earthquakes: New evidence of seismic slip in the rock record
Heather M. Savage et al., Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA; firstname.lastname@example.org. Published online ahead of print on 6 Jan. 2014, http://dx.doi.org/10.1130/G34901.1.
While earthquakes must occur along faults, it is very difficult to determine what structural features in fault zones are directly related to earthquake slip. Identification of past earthquakes on exhumed faults would allow relation of structural features to earthquake processes. Frictional melt, called pseudotachylyte, has been the only way to detect past earthquakes on faults that have been exhumed to the surface. In this study, Heather Savage and colleagues show that organic compounds present in sedimentary rocks are altered along faults that were unambiguously heated during earthquakes, as evidenced by the presence of pseudotachylyte melt in the faults. They also observe a gradational heating signature away from the fault that is not observable with pseudotachylyte but is expected from thermal diffusion. These results show for the first time that the difference in organic thermal maturity between on and off-fault rocks is a robust earthquake indicator.
How accurate are rivers as gauges of chemical denudation of the Earth surface?
Julien Bouchez, GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Telegrafenberg, 14473 Potsdam, Germany, email@example.com; and Jrme Gaillardet Institut de Physique du Globe de Paris, Universit Paris
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Geological Society of America