Rift thermal inheritance in the SW Alps (France): insights from RSCM thermometry and 1D thermal numerical modelling

Abstract. Conceptual models of orogenic accretionary prisms assume that peak temperatures (Tmax?) increase towards the internal domains as crustal rocks are accreted from lower to upper plate. However, recognition pre-orogenic heating events in mountain belts questions magnitude thermal overprint during nappe stacking. Using Raman spectroscopy on carbonaceous material (RSCM) calculate Tmax?, we have investigated record Lower Jurassic Eocene strata exposed along six stratigraphic sections at front Digne Nappe (SW Alps), Devoluy Massif Castellane Arc. Our results highlight two groups depth-dependent temperatures: (1) a regionally extensive and constant Tmax? up 300–330 ?C measured succession (2) variable (<150 ?C) recorded either Upper Mesozoic or syn-orogenic sequence. Modelling shows highest palaeotemperatures were achieved Early Cretaceous (? 130 Ma), associated with Valaisan–Vocontian rifting, while lowest reflect post-rift relaxation Alpine foreland basin. This study provides striking new example where mid-crustal sediments downgoing plate inherited. An estimated gradient 80–90 km?1 requires thickness 8–10 km Cretaceous, hence placing constraints for tectonic reconstruction rift geophysical interpretation current SW Alps. These call careful palaeothermal data when they used identify past collisional events. Where details basin evolution lacking, high-temperature records may be misinterpreted syn-orogenic, which can turn lead an overestimation both thickening horizontal displacement belts.