• General statement of Central Armorican trough during Llandovery through Lochkovian: "depositional patterns typical of a platform environment...Silurian is mainly an alternating succession of unfossiliferous sandstones and locally fossiliferous black shales...The arenaceous deposits are probably related to the eustatic regression and corresponding high sedimentation rate during the Pridolian and Lochkovian...Outside the A. Massif the Pridoli-Lochkovian succesion in Artois (boreholes) is characterized by shallow marine shales and limestones overlain by areanceous deposits that correspond to the Early Devonian transgression."

•For this Community: "The preservation of the phyllocarids...and crinoids (with stems and arms still articulated to the calyx) are suggestive of rapid burial. Rolfe and Beckett (1984) assgined the Laval Basin, Silurian phyllocarid localities to the 'restricted marine A' environment, which they interprted as lagoonal or estuarine with ephemeral brackish or hypersaline waters. The fauna is cosmopolitan and low diversity, but the presence of true, marine faunal elements...precludes such an environment...[lithology and preservation] suggest a quiet environment...well below wave base...the abundance of Myodocopida ('Bolbozoe') implies an offshore, epicontinental shel setting-probably BA 4 or 5..In the eastern Armorican Massif these nodular shales represent the deepest facies."

• General statement: "In Brittany there are two kinds of black shale and limestone deposits during the Llandovery to lowermost Devonian interval: (1) black shales (commonly described as sapropelites) are widespread in space and time and (2) black, micritic limestones or argillaceous limestones are restricted to two localities in the eastern part of the Armorican Massif. The black shales are very rich in organic matter and locally contain detrital mica, pyrite, and nodules..."

•For this community: "The fauna occurs exclusively in nodules interbedded in black shales...sediment finely laminated and shows no evidence of bioturbation..."