Mantle influence on Andean and pre-Andean topography

DÁVILA, F.M., MARTINA F., ÁVILA P., NÓBILE J., COLLO G., EZPELETA M., CANELO H., SÁNCHEZ NASSIF F.; LITHGOW-BERTELLONI C.

The making of Chilean-Argentinean Andes

Springer

Año: 2018; p. 363 - 386

Mantle convection can drive long-wavelength and low-amplitude topography, whichcan occur synchronously and superimpose to tectonics. The discrimination betweenthese two topographic components, however, is difficult to assert. This is because thereare still several uncertainties and debates in the geodynamic community, for examplethe scales and rates of dynamic topography. Geological, geomorphological,geophysical measurements and/or landscape analyses might assist to validate models.In this contribution we provide new geological evidences along the central andsouthern Andes, which demonstrate that dynamic topography has been an importantcomponent on the South American landscape formation as well as in the ancientwestern Gondwana. Our examples in the Argentine Pampas show that dynamictopography is required to explain the whole observed topography and that the amountof dynamic components is much lower than proposed in previous work (averagedynamic subsidence rates of ~0.04 mm/yr, which contrast with the ~0.1 mm/yrestimated in the US). We also propose two strategies to analyze ancient cases. The firstrequires of comparing a total elevation proxy, like the equilibrium lines (or ELA) inglaciated areas, with model topography derived from geochemical studies of mantlerocks. A second example was taken from the Triassic rifting evolution of westernArgentina (post-rift sag deposits). Sag deposit thicknesses exceed 2 km, which do notcorrelate with the hundred-meter thick thermal calculated by rift subsidence modelling