SEARCH Articles Figures Tables Gypsum in the Villalba de la Sierra Formation. A Field view of the Villalba de la Sierra Formation near the village of Fuentes. The left side and center of the picture show the Bascuhana Member, composed mainly of massive alabastrine gypsums, and the right side exhibits green marly mudstones of the upper part of the Villalba de la Sierra Formation. The highlighted rectangle represents the area where the next picture was taken [Publishers Imprint]