Andean‐age structure of Eastern Cordillera (Province of La Paz, Bolivia)

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Abstract
A Moho root beneath the Bolivian Andes, 40 km deep, is consistent with 230 km of overlap of Neogene age on a single, trenchward dipping transcrustal thrust fault with 10° of finite ramp cutoff (Main Andean Thrust (MAT)). Only 10% of the Andean crustal volume is ascribable to magmatic addition. The MAT is located within South American crust of full thickness. It intersects the basement top 450 km inland from the Neogene crustal margin. It is not a collision suture as shown by persistent pre‐Neogene facies continuity. Thrusting is not accompanied by terrane accretion. The present bilaterally symmetrical thrust belt responds to elastic line loading and to Coulomb rheology. In the hanging wall of the MAT, a deep high‐stress wedge base builds a steep critical slope. In the footwall, the foredeep response is fast subcritical growth by progradation and blind thrusting on a low‐stress decollement. Interaction is maintained by out‐of‐sequence renewal of movement on the MAT.