Symptomatic lithospheric drips triggering fast topographic rise and crustal deformation in the Central Andes

The basin and plateau regions of the Central Andes have undergone phases of rapid subsidence and uplift during the last ~20 Myr in addition to internal tectonic deformation. Paleoelevation data and the presence of high seismic wave speed anomalies beneath the Puna Plateau suggest that these tectonic events may be related to lithospheric foundering. Here, we study the geodynamic processes in the region using three dimensional, scaled, analogue models and high-resolution optical image correlation techniques. The analogue experiments show how a gravitational instability of the mantle lithosphere developing into a lithospheric drip may form a circular sedimentary basin in the crust that undergoes subsidence and subsequently reverses to uplift, while simultaneously undergoing internal crustal shortening. The model results reveal that drips may be “symptomatic” where the crust is well coupled to the sinking mantle lithosphere and manifests tectonic deformation at the surface, or poorly coupled “asymptomatic” drips with weak crustal surface manifestations. Overall, the physical models suggest that the formation of the Arizaro Basin and nearby Central Andean basins are caused by symptomatic lithospheric dripping events and highlight the significant role of non-subduction geodynamic mechanisms in driving surface tectonics.