Constraints on the thermal evolution of the Magallanes Basin (MB) and the timing of the Patagonian fold-and-thrust belt formation in the Chilean study area reveal a complex pattern related to burial, thrust-driven exhumation and contact metamorphic events. The major phase of deformation is constrained between ca. 60 and 46 Ma. The [MnO|SiO2,Al2O3,FeO,MgO] ratio was defined to discriminate stratigraphic formations in the MB and to reconstruct the depositional environment. The Torres del Paine (TPI) intrusive complex had different consequences for inorganic and organic compounds of the metapelitic host rock. The maturity of carbonaceous matter is the most reliable and unequivocal indicator of peak temperature on time scales of several thousand years. Based on K/Ar age determinations on illite fine fractions a zone of incipient 40Ar* loss is constrained between 248 and 320 °C for the <0.2 µm fraction and between 260 and 345 °C for the <2 µm fraction.