The Anticlinal Aguada Bandera (AAB) belongs to the southern plunge of the Sierra de San Bernardo fold belt in the western flank of the Golfo San Jorge Basin. We analyze the geochemistry of oils concerning their origin, migration and alteration. The structure is within a depocenter of the Pozo Anticlinal Aguada Bandera-1 Fm. (FPAAB1, Tithonian to lower Valanginian), the first one tested with Neocomian source rock. However, this work shows the association of the oils to the Pozo D-129 Fm. (FPD129, BarremianAptian). The structure (axis N30°W, 18-5 km long-width) is exhumed at the Río Chico Fm. (Paleocene) level, discouraging its exploration for four decades. The hydrocarbons are hosted in the Bajo Barreal and Castillo formations. The Anticlinal Aguada Bandera.x-1 well (YPF 1970, 484 m depth) drilled 1300 m of black mudstones rich in organic matter, receiving its name later. FPAAB1 is an effective oil source rock for the Río Mayo and Mata Magallanes oilfields and is currently in the gas window for Los Monos and AAB oilfields. The well also crossed 1250 m of FPD129 with only 15 m of black siltstone in its upper third, which would support the idea of generation from FPAAB1. Nonetheless, geochemical correlation associate oils at peak generation thermal maturity stage (0.7-1.0% VRE) with FPD129, with typical biodegradation and remigration traits. The burial history estimates that FPAAB1 transited the dry gas window at 115-60 Ma and FPD129 partially reached early oil maturity at 60 Ma. In this period, the San Bernardo Fold Belt had not yet formed, and the area showed smooth reliefs, with the Cretaceous sedimentation arranged in a gentle E-SE slope that controlled the migration for gas and oil of FPAAB1 and oil of FPD129. Thickness increasing of the FPD129 occur 20 km east in Los Perales and Ea. Cholita (south) oilfields, with higher maturity and TOC >1.5%. Therefore, we interpreted that the oil from FPD129 migrated west and northwest within the Chubut Group. The exhumation of the structures to the north of the Senguerr River began in the Middle Miocene, while to the south, the petroleum system remained partially buried, forming the AAB, Los Monos, Cerro Piedras, Estancia Cholita, and Cerro Guadal Norte fields. The dispersed hydrocarbons remigrated and accumulated in the structure of AAB. This partial exhumation process gives some characteristics: gas and shallow heavy oils, washed by meteoric waters, biodegradation, and pore underpressure in the topographic highlands