The geology of the Western Alps through the field notebooks of Secondo Franchi (1859-1932)

Secondo Franchi (1859-1932) was one of the most important geologists of the Regio Ufficio Geologico of Italy. In collaboration with his colleagues of the Turin office, starting from 1888 Franchi surveyed in detail the Western Alps to contribute to the new Geological Map of Italy at the 1:100,000 scale. Franchi's studies contributed to the definition of a still largely accepted chronostratigraphic framework for the Alpine successions, and to the recognition of previously overlooked folding and faulting phases in the Western Alps. Eleven of Franchi's field notebooks are kept in the Library of Istituto Superiore per la Protezione e la Ricerca Ambientale in Rome. These notebooks are richly illustrated with geological sections and landscape sketches and represent an invaluable firsthand resource for the analysis of Franchi's mapping methods and interpretive procedures. This paper analyses Franchi's contribution to the geological knowledge of some specific localities of the Western Alps, integrating excerpts from his original field notebooks and published works.