From Sink to Source: Looking at Alpine Geology Through the Garbage Can

Garbology, the science of finding stuff out about someone or something by digging through their trash, was invented in September 1970 by Alan Jules Weberman, a gadfly journalist who tried to unveil private secrets of Bob Dylan and his wife, the ex-bunny girl Sarah Lowndes, by searching the trash outside their Greenwich Village home in New York. Garbological applications to the Earth Sciences (“provenance analysis”) provide unique information on the hidden secrets of orogenic belts by scrutinizing the detritus they produce (“waste” in old geomorphological literature). This daring and exciting task requires painstaking dedication. First, we need to determine end-member signatures of “waste” shed by the diverse tectonic units incorporated in the mountain belt. This can be done only in modern settings and climatic conditions that grant minimum chemical weathering. Distortions of the original compositional signals by hydrodynamic processes need to be carefully checked and corrected for. Next, by combining the end-member signals as thus determined using forward modelling, we get a grasp of compositions expected to be found in the orogen’s garbage cans (“sedimentary basins”). The comparison between the expected and the observed may eventually lead us to decrypt the garbological record preserved in stratigraphic successions, and to unravel events the traces of which have long been erased by erosion from bedrock exposed in the thrust-belt. Simple statistical procedures allow us to interpret with a good amount of confidence information stored in recent deposits of the Pleistocene, but inferences become more and more uncertain when we try to extrapolate our knowledge of the present backwards in time to reconstruct sceneries of the remote past. By carefully checking diverse alternative hypotheses, however, garbologists may be of help to serious bedrock geologists to reconstruct with unsuspected precision the orogenic history of the Alps since the very beginning of convergence between Africa-Adria and Europe.