8 Climatic Hypotheses of Alluvial-fan Evolution in Death Valley Are Not Testable

For the last two decades, climatically based interpretations have been the major focus in evolutionary studies of dryland alluvial fans. Climatic hypotheses to explain the development of alluvial fans in southern Death Valley, however, do not fare well when they are assessed with criteria used by philosophers of science. First and foremost, dating techniques do not have the chronometric precision or accuracy to correlate Pleistocene fan aggradation (or hiatuses in deposition) to Pleistocene climatic changes. Second, there is only one clear correlation of fan aggradation and a climatic interval: in the hyperarid Holocene in Death Valley. A single temporal correlation, no matter how many data points go into it, does not comprise abundant support for a climatic hypothesis. Third, climatic hypotheses are difficult to separate from nonclimatic explanations of Death Valley fan evolution. Fourth, it, is very difficult to successfully predict or model Death Valley fan behavior from climatic hypotheses. Lastly, it is not possible to falsify the competing hypothesis that aggradation on Death Valley alluvial fans is entirely from high-magnitude meteorological storms that are not necessarily tied to any climatic regime. This analysis indicates that climatic hypotheses are not testable for Pleistocene-age fans in Death Valley, and perhaps for alluvial fans in other drylands.