The Rawson and Valdés rifts, located under the shelf south of the Río Negro High, that separates them from the Colorado Basin, and north of the Golfo San Jorge Basin, record an extensional history before the breakup of the South Atlantic. The basins were first identified by gravity and seismics (refraction and reflection) in the late 1960’s. The wildcat YPF.Ch. PV.es-1 confirmed the existence of sedimentary basins off the coast, east of the Valdes peninsula. Regional seismic grids recorded in the 1970’s and 1990’s identified several NNW-SSE oriented grabens (Rawson Basin), with three segments bearing distinctive features. The Valdés Basin represents a set of more isolated and less continuous grabens, although with a similar orientation. Structural features of the Rawson Basin comprise a broad basin in the NNW, with a depth to basement exceeding 6 km, segmented by horst and graben structures, along an SSW dipping master detachment, known as the Ameghino subbasin. In the SSE, the so called southern subbasin is built up by narrower (20-30 km width) symmetrical basins, with a depth to basement of 2-3 km. Both subbasins are separated by a lineament with oblique tectonic features and the presence of intrusives and volcanoes. It is proposed to link up this lineament with the Colorado Fracture Zone, segmenting the SDRs developed underneath the shelf edge and the Jagüelito shear zone, defined onshore. The latter is associated to the Gondwana orogen and was reactivated during Middle Triassic times (243 Ma). Structural differences across the Rawson Basin could indicate that this long living feature controlled both the extensional deformation of the rift as well as later, affected the northwards propagation of the first segment preluding the breakup of the South Atlantic Volcanic Divergent Margin. In the Ameghino subbasin, the wildcat Tayra investigated the existence of a potential petroleum system on a structural high and turned out to be a dry hole. The late synrift infill drilled across, was built up of fluvial red beds without age-diagnostic elements. Onshore thermocronological AFT samples close to the Valdés Basin yielded cooling data between 200 and 160 Ma, which would indicate a lower and upper limit for tectonic stripping during crustal extension. After breakup, the area was exposed to exhumation. During the latest Cretaceous, the Valdés Basin started to subside, while the Rawson basin remained devoid of sedimentation until Late Early Miocene times, when the present shelf was flooded for the first time.