Luca Martire

The study of ancient marble plays an important role in the interpretation of historical and archaeological sites and gives interesting information about building materials used in ancient times and their trade routes. The present work focuses on Chianocco marble that represents one of the most important ancient white marbles for cultural heritage exploited in the Piedmont region (Northwest Italy) and employed for the Palazzo Madama façade. A multi-analytical study based on petrographic (optical and scanning electron microscopy), electron microprobe, cathodoluminescence and stable isotope analyses was carried out on these marbles in order to perform an archaeometric study. Chianocco marble was used in Turin during the baroque era by the Savoy architect Filippo Juvarra (1678–1736) in historical buildings, such as the façade of the Palazzo Madama, the plinth of the façade of the town Cathedral and the columns (now plastered) of the portico of Piazza San Carlo. This stone is a dolomitic rock belonging to the Mesozoic cover of the Dora Maira Massif (Pennidic Unit). It shows a vuggy fabric characterized by a vacuolar texture due to tectonic brecciation and subsequent selective dissolution during subaerial exposure. This kind of research is useful to highlight the importance of the use of local stones as building materials and to investigate stone materials for the restoration and maintenance of historical buildings.

A new structural setting for the central part of the External Ligurian Briançonnais (CELB) is proposed. CELB is divided into km-scale tectonic units that still preserve pre-Alpine geological features at several stratigraphic levels. Macro-, meso- and microscale primary features, such as paleoescarpments, unconformities and depositional or diagenetic fabrics are thus well preserved and can be still mapped and studied in detail at many stratigraphic levels.Significant transposition of bedding is recorded only in Upper Cretaceous and Eocene marly limestones and shales and in major km-long shear zones, where intense development of closely spaced tectonic foliations occurred.Several features indicate that the CELB tectonic evolution took place at shallow crustal levels: 1) strong localization of deformation along the weakest stratigraphic levels; 2) absence of diffuse recrystallization of rocks; 3) minor occurrence or absence of transposition of bedding; 4) kinematic evolution of fold axial plane foliations into frictional slip cleavages.A gradual decrease in the intensity of deformation from the Internal Ligurian Briançonnais to CELB and Dauphinois Domain is observed, although the boundaries of these three domains correspond, in the study area, to several Km-long, transpressive shear zones whose kinematic role in the evolution of the southern termination of the Western Alps should be carefully considered.

R. M. Russo, V. I. Mocanu, M. F. J. Flower, Meng Xianghua, Ge Ming, Kuang Hongwei, Cai Guoyin, Cai Guoyin, Dr. Daniel Cassard, Caj Kortman, Dr C. J. R. Braithwaite, Luca Martire. Episodes 2003;26:26-35. https://doi.org/10.18814/epiiugs/2003/v26i1/005