Found at Pileta de Prehistoria.
J.M. Moreno et al., The Middle-to-Upper Palaeolithic transition in Cova Gran (Catalunya, Spain) and the extinction of Neanderthals in the Iberian Peninsula. Science Direct, 2010. Pay per view.
A good article can be found at El País in both Spanish and English.
Most relevant seems to be that the transition between the occupations by the two species is separated by a thick sterile layer, meaning that there was no sudden replacement but maybe just the colonization of an empty land.
Cova Gran is located at the Catalan Pyrenees in the province of Lleida.