The Sierras Marginales thrust sheet has been subdivided into three groups of minor thrust sheets, according to the features of the pre-lutetian stratigraphic succession, combined also with the features of the lutetian sediments and to its presence or absence. These are, from N to S, the Ager-Montroig, the Sant Salvador-Roca Roja and the Sant Llorenq de Montgai tectonic units. Lutetian sediments deposited in two separated areas, located respectively in the Sant Llorenq de Montgai and Sant Salvador-Roca Roja tectonic units, in shallow carbonate platform and nearshore to fluvial environments. The relationsheeps between thrusts and three conglomerate units that outcrop in the tectonic units above mentioned, suggest that thrusts moved in an overstep thrusting sequence