The writer describes a detrital series known under the name "Grès de Taveyanne". This formation includes greywackes which are the product of the erosion of andesitic volcanoes. Its age is estimated to be near the Eocene-Oligocene limit. This series has undergone load metamorphism of low grade caracter due to tectonic overlaying of nappes. Several facies, caracterized by distinct mineral assemblages are described : 1. "Faciès vert" : albite, ± prehnite, chlorite, sericite, sphene. 2. "Spotted" laumontite facies: albite, laumontite, chlorite, sphene. 3. "Spotted" pumpellyite-prehnite facies: albite, pumpellyite, prehnite, chlorite, sphene. The "Faciès vert" was formed first : it is found only in zones that underwent mechanical deformation by the overlying of "préalpines" nappes. Laumontite facies development took place after the green facies was formed but before the appearance of the pumpellyite-prehnite facies. This last facies is the result of the transformation of laumontitic greywackes and is present only where formation is affected by overloading due to helvetic nappes. The "Faciès vert" is thought to have developed under a temperature lower than 200°C and under an overloading pressure going upper to 1600 bars supplemented by tectonic pressure (stress). Laumontite facies develops at higher temperature (200°C and more), but under the same overloading pressure. At last, the physical environment caracteristical of pumpellyite-prehnite facies seems that of laumontite facies but with an additionnal tectonic pressure.