Investigations on marbles and stones used in Augustean monuments of western alpine provinces

Scientific and stylistic analysis of some public buildings erected during the Augustan age in the most important cities of the Italian side of Western Alps, Augusta Praetoria (Aosta) and Segusium (Susa, located in Turin district) shows the importance awarded to building processes by ruling classes. The honorific arches dedicated to emperor Augustus in both cities and the Porta Praetoria in Aosta, on one hand demonstrate the loyalty of the citizens to Roman state, one the other imitate recent architectonic features devised in the Urbs. The use of local materials in all these monuments, nevertheless, gives to them a peculiar character. The two arches devoted to the Princeps, older then the Aostan city gate (Aostan Arch: about 20-10 B.C.; Arch of Susa: 9/8 B.C.), were built entirely using stones that need final touches in plaster (puddingstone at Aosta, a kind of marble at Susa), whereas the Porta Praetoria (about 10-20 A.D.) presents mouldings in imported marble (Carrara) and some ribs in a grey local stone (Aymavilles marble, similar to the Bardiglio marble of Carrara district) imitating precious foreign marbles. This fact is a consequence of a larger use of expensive materials in Roman official architecture.