The early stages of the dislocation structure forming in intense slip bands are analysed, using 3D4 modelling. The surface displacements generated by plastic slip are computed using an analytical post-processing method. A detailed scheme for persistent slip marking formation and morphology is proposed, in relation with the persistent slip band dislocation arrangements present inside of the grain. The simulations show the crucial role of these arrangements for the extrusion-intrusion growth and localisation of plastic slip at the band edges. The results provide insights for a new micro-crack initiation scheme, combining different initiation mechanisms described in the literature.