RT Journal Article T1 Observaciones sobre las fracturas de las diaclasas plumosas A1 Pocoví Juan, Andrés A1 Arlegui, L. E. A1 Simón Gómez, José Luis AB Many joint surfaces show en échelon arrays of microfractures (F-joints) along one or both fringes of hackle marks. Our field observations indícate that, where both sets are present, they are stepped in oposite senses. So the F-joints can not be used as shear criteria for discontinuities. Good examples of hackle marks with F-joints have been reproduced in the laboratory by submitting silicone putty to tensile tests when these include sorne rotational component. Rotation induces shear in different senses if observed from an external point of view; so it can explain the development of two sets of Riedel fractures showing opposite stepping. In geological conditions, this rotation occurs around the tips of fractures undergoing vertical displacement. Thus, from this model, hackle marks and F-joints could be used for detecting the sense of small dip-slip movements on joints PB Sociedad Geológica de España YR 1991 FD 1991 LK http://hdl.handle.net/10272/18008 UL http://hdl.handle.net/10272/18008 LA spa DS Repositorio Institucional de la Universidad de Huelva RD 31 may 2026