Geo-petrographic data on the metamorphic rocks with Cambrian, Silurian and Devonian fossils in the Agordo area (Southalpine metamorphic basement of the Eastern Alps, Italy).

Recently, in the Agordo area, some unquestionable fossils have been described: 1) Latest Cambrian acritarchs, within trivial black, fine grained phyllites (Col di Foglia); 2) Aeronian graptolites, within boudins along a recrystallized shear zone cutting low-grade metapelites (Ponte Alto); 3) Middle Devonian Rugosa corals, within metalimestone boudins along the mentioned shear zone. These fossil findings are unique in this basement, therefore, the rocks containing them deserve a careful petrographic investigation. This paper presents the basic petrographic features of the rock samples containing the fossils. All the rocks underwent a greenschist facies metamorphism (chlorite zone) under a thermal gradient of ca. 38°C/Km. The most interesting rocks are those bearing well preserved graptolites which mainly consist of quartz, fluorapatite (up to 70%.), carbonaceous matter and sulphides. T in the boudins turns out to be slightly lower than in the surrounding matrix.