First record of OSL‐dated fluvial sands in a tropical Andean cave reveals rapid late Quaternary tectonic uplift

Abstract

We present the first results of OSL‐dated fluvial sands extracted from a riverside cave in the tropical Andes. The excellent agreement between the ages of the various samples allowed the calculation of a late Quaternary valley incision rate forced by ongoing uplift of an active Subandean fault‐propagation fold in NE Peru. A structural cross‐section was constructed to understand the relationship between the geometry of the fault‐propagation fold, historical damaging earthquakes and the cave system. The calculated uplift rate is 2.3 to 2.6 mm a⁻¹ over the past 70 ka and can be directly linked to active propagation of west‐verging basement thrusts. It is similar to uplift rates calculated from fluvial terraces in the Subandes of Colombia and Venezuela. The results will help to better assess the seismic hazard and confirm that OSL dating of fluvial sands in caves is a powerful tool to quantify uplift rates of active mountain fronts.