Here, we run a set of numerical experiments exploring how the style and magnitude of isostasy in warmer more ductile regions versus colder more rigid regions affect the architecture and evolution of fold-thrust belts, and employ a case study of the Subandean zone. We found that when ductile flow is involved in accommodating isostatic adjustment, subsidence is rather local, larger, and results in narrower, less elevated fold-thrust belts with a complex internal architecture consisting of prominent steeply dipping faults. When isostatic subsidence is controlled by lithospheric flexure, the tilting of the basement on 10’s of km scale facilitates the outward propagation of fold-thrust belts. The internal architecture is simpler and involves prominent basement-parallel décollements. The outcome is wider fold and thrust belts with higher topographies.
