Contributions to the stratigraphic architecture of the Chubut Group in the North Flank, Basin Center and offshore of the Golfo San Jorge basin, Argentina.The current stratigraphic scheme of the Chubut Group in the Golfo San Jorge basin (GSJB) proposes the existence of a basal large perennial lake (Pozo D-129 Formation) that was feeded by peripheral fluvial systems (Matasiete Formation). The lithostratigraphic criteria to differentiate these units in outcrops and cutting samples are clear, because the Pozo D-129 Formation contains black shales and coastal deposits with oolitic limestones, while the Matasiete Formation is recognized by their typical reddish siltstones deposited in subaerial fluvial floodplains. On the other hand, the top of the Pozo D-129 Formation is one of the better seismic reflectors in the basin, defined by a high acoustic impedance level. A detailed revision of the cutting record of some wells in the Northern Flank and Basin Center of the GSJB allows to calibrate seismic sections with wells. In fact, the presence of the Matasiete Formation (235 of thickness) was documented in the Northern Flank of the basin (El Trébol oilfield), a unit considered until now exclusive of the San Bernardo Fold Belt and peripheral sectors of the basin. Besides, in the basin center (eg. YPF.SC.PDA.x-1), the presence of the Pozo D-129 Formation was documented above the seismic marker with more than 900 m of thickness; representing a very significant difference between lithostratigrpaphic and seismostratigraphic boundaries. This information points out to the presence of lacustrine and coastal deposits within the basal seismic interval assigned up to now as Mina El Carmen Fomation, above the marker used as seismic top of the Pozo D-129 Formation. The results of the work have different contributions, both prospective and methodological. On the one hand, the possibility of finding reservoirs associated with fluvio-deltaic paleoenvironments of the Matasiete-Pozo D-129 system within the seismic interval interpreted so far as Mina El Carmen Formation in the Northern Flank and Basin Center, thus expanding the exploratory opportunities in the onshore and offshore. On the other hand, the increase in the column of lacustrine rocks with the capacity of source rock above the regional marker, would also have an impact on the petroleoum systems (maturation, overburden, etc.). Methodologically, these results conditioned the use of the seismic marker as a lithostratigraphic boundary in the Basin Center and to revalue the use of direct information (cutting).