The Chubut Group, also known as "Chubutian", is a stratigraphic unit that appears not only in the Golfo San Jorge Basin (CGSJ) but also in the Cañadón Asfalto Basin (CCA). The Chubutian presents two regionally differentiable sections: 1) an essentially epiclastic lower section, with significant variations in thickness, more restricted areal distribution, Barremian age to Aptian, and 2) an essentially pyroclastic upper section, with more constant thicknesses, greater areal distribution and Albian to Campanian age. From an economic point of view, the Upper Chubutian is the most prolific productive horizon of O&G in the CGSJ, while the Lower Chubutian, although historically contributing less in production, in recent years has significantly increased it, especially for gas. The objective of this work is, starting from surface information, to describe the architectural elements of the Lower Chubutian and propose a tectosedimentary model that can be extrapolated to subsurface. The reference point are the stratigraphic columns outcropping in the CCA (Fms. Cerro Fortín / Los Adobes), which are the most complete and representative of the tectosedimentary activity in the North flank of the CGSJ and that also allow to analyze the relationship with the pre-Chubutian substrate. In these columns, three coarsening upward sequences are recognized, although the general arrangement of the complete cycle presents a gradual decrease in energy. During the deposition of the whole cycle the sedimentation rate vs space generation was balanced, predominating coarse continental deposits, from alluvial fans to braid-plains evolving laterally and vertically to more sinuous fluvial systems. The proposed model responds to asymmetric depocenters, with strong taphrogenic control, showing opposite polarities and aligned following a defined trend. The paleocurrents in the two initial basal sequences are erratic and greatly influenced by local paleo-relief in confined depocenters while in the latter have a S/ SW general tendency, a consistent trend with the regional paleo-slope followed by an integrated fluvial system. This last sequence is broader distributed but still confined to a submeridian tectonic paleo-valley that discharged in the CGSJ at the time of the Matasiete / Pozo D-129 Fms. In this scenario only in the main axis of the CGSJ, the magnitude of the extension allowed the generation of a permanent huge lake, relatively deep, that permitted the development of euxinic organic facies in its center: Fm. Pozo D-129. Finally, we compare this model with some selected reference wells in the North flank in order to verify the proposed analogy.