Quantifying crustal thickening and surface uplift in the northernmost Central Andes

Since its onset in the Late Cretaceous, episodic mountain building in the Central Andes has shaped the landscape, climate, and biota of western South America through a series of synchronous regional pulses of intensified deformation and surface uplift acting at the scale of the entire orogen. However, despite this common Late Mesozoic through Cenozoic tectonic history, the ~4000 km long Central Andes exhibit remarkable latitudinal differences in both height and width, pointing to the potential importance of local heterogeneities in controlling the magnitude of topographic growth associated with each of the regional mountain building episodes. A thorough understanding of the driving mechanisms behind these latitudinal differences requires first determining the times, rates, magnitudes and spatiotemporal patterns of crustal thickening and surface uplift along the orogen. While this has been done extensively in recent years for the southern and central portions of the Central Andes, such processes are still insufficiently constrained in its northernmost part.

In this work, we use new and published whole-rock geochemistry data from the Late Cretaceous to Late Miocene arc-related magmatism recorded in northernmost Peru to quantitatively estimate crustal thickening and surface uplift using empirically calibrated “chemical mohometers” based on the ratios of key trace elements. We compare our results with the tectonostratigraphic evolution and tectonic subsidence history of the adjacent foreland and hinterland basins. Finally, we present new apatite U-Th-Sm/He and apatite fission-track thermochronological data from a transect across the northernmost Central Andes. These data, integrated with structural observations and the reconstructed crustal thickening and surface uplift history, unravel the relative contribution of magmatism and shortening to the observed crustal thickening.