Quaternary uplift rates along the Chilean Coast (19°S-31°S)

• Applicant: Professor Dr. Tibor J. Dunai
• Subject Area: Palaeontology
• Term: from 2012 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 220050336

The reconstruction of past tectonic movements is a prerequisite to understanding the underlying endogenic processes, and serves as an essential step to assess tectonic hazards in a region. The aim of the proposed research project is to unravel the Quaternary tectonic uplift history along the tectonically highly active Chilean coastal margin between 19º and 31ºS and to determine its spatiotemporal variations. This region features wellpreserved marine terraces up to several hundreds of meters in elevation that record coastal uplift throughout the Quaternary. Age-elevation relationships of the youngest terraces and the highest terraces indicate that uplift rate accelerated significantly during the Quaternary. In order to describe the spatial and temporal pattern of acceleration in uplift rate we propose to establish a regional chronology of marine terraces throughout the Quaternary. We propose to date well preserved features on the marine terraces, such as beach ridges and bedrock abrasion platforms by exposure dating utilizing cosmogenic nuclides (10Be, 26Al and 36Cl). Targets for dating are cobbles for single clast exposure ages (beach ridges), bedrock samples (abrasion platforms) and depth profiles (drilled in abrasion platforms; sampling of vertical terrace exposures and in pits). The proposed multiple-isotope approach and depth profile sampling will allow for the validation of the calculated ages and also the necessary correction of the exposure dates for any erosion, which may be significant for the oldest terraces. The motivation to derive this geochronological framework is (i) to test the general validity of the notion of accelerated Quaternary uplift for the region, (ii) provide a ‘base level’ for tectonic uplift-rates for this region (iii) establish the age of the onset of terrace formation along this coast and finally (iv) to infer potential alongstrike segmentation of the coast that will indicate the existence and persistence of megathrust segment boundaries.

• DFG Programme: Research Grants
• Participating Person: Dr. Pia Victor