Pedogenic products sealing normal faults (Barcelona Plain, NE Spain)

Minor normal faults affecting Miocene conglomerates of the Barcelona Plain are constituted by a poorly developed fault core without a damage zone. Fault rocks are made of a red muddy material that has been obliterated by later diagenetic processes. The most important products are spherulites and palisades formed by orange bladed calcite crystals. These calcite crystals are interpreted as resulting from pedogenic processes, being similar to Microcodium. The precipitation of the calcite crystals was induced by evaporation together with biota activity. The presence of these pedogenic products has an important effect in fault evolution because: 1) they date fault evolution during the Miocene extension; 2) they indicate shallow burial depth and meteoric diagenetic environment during fault evolution; and, 3) they give the cohesiveness to the fault rock causing the sealing of the fault and its behaviour as a barrier to fluids.