The puzzling regmatic system of Eastern Dolomites, Italy

Following the mesoscale structural investigation of the Eastern Dolomites leading to the partial unravelling of the tectonic stratigraphy of the area, of which the results are presented in a companion paper, the study of the macroscale structures, and particularly their pattern, geometry and kinematic behaviour, was performed. A detailed structural map of the region was prepared (scale 1:50 000). The geometry of most fracture planes was traced according to standard techniques of photo-interpretation, while systematic field work was carried out to observe the real kinematics of the tectonic features, as well as to recognise the low- to middle-angle fault planes which are otherwise almost undetectable from aerial views. A second map, which shows the distribution of the outcropping lithologies, qualitatively grouped in four major rheological categories, was also prepared. According to the geometry and mostly the kinematic behaviour, three principal types of tectonic structures were distinguished: i) transcurrent faults, ii) normal and transtensional faults and iii) low- to middle-angle contractional faults. The first type is certainly the most represented one, forming dense sets of parallel planes which locally characterise entire sectors of the study area. In contrast, the normal and transtensional features are developed uniquely in the northeastern sector and are represented by both negative flower structures and graben. The low- to middle-angle contractional faults are represented by both north- and south-verging thrusts, among which the Ansiei Thrust System is certainly the most important structure being more than 30 km long. Finally, the general tectonic evolution of the puzzling regmatic system was tentatively reconstructed with the aid of geological sections.