Late Miocene - Quaternary forearc uplift in southern Peru: new insights from 10Be dates and rocky coastal sequences. (August 2021)

• Record Type: Journal Article
• Authors: Regard, Vincent; Martinod, Joseph; Saillard, Marianne; Carretier, Sébastien; Leanni, Laetitia; Hérail, Gérard; Audin, Laurence; Pedoja, Kevin
• Is Part Of: Journal of South American earth sciences. Volume 109(2021)
• Publication Date: 2021-08
• Subjects: Neogene -- Quaternary -- Andes -- Coastal sequence -- Marine terrace -- Rasa -- Cosmogenic dating -- Episodic coastal uplift; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2021.103261
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: We explore the coastal morphology along an uplifting 500 km-long coastal segment of the Central Andes, between the cities of Chala (Peru) and Arica (Chile). We use accurate DEM and field surveys to extract sequences of uplifted shorelines along the study area. In addition, we consider continental pediment surfaces that limit both the geographical and vertical extent of the marine landforms. We establish a chronology based on published dates for marine landforms and pediment surfaces. We expand this corpus with new 10 Be data on uplifted shore platforms. The last 12 Ma are marked by three periods of coastal stability or subsidence dated ~12-11 Ma, ~8-7 Ma and ~5–2.5 Ma ago. The uplift that accumulated between these stability periods has been ~1000 m since 11 Ma; its rate can reach 0.25 mm/a (m/ka). For the last period of uplift only, during the last 800 ka, the forearc uplift has been accurately recorded by the carving of numerous coastal sequences. Within these sequences, we correlated the marine terraces with the sea level highstands (interglacial stages and sub-stages) up to MIS 19 (790 ka), i.e., with a resolution of ~100 ka. The uplift rate for this last period of uplift increases westward from 0.18 mm/a at the Peru-Chile border to ~0.25 mm/a in the center of the study area. It further increases northwestward, up to 0.45 mm/a, due to the influence of the Nazca Ridge. In this study, we document an unusual forearc cyclic uplift with ~4 Ma-long cycles. This periodicity corresponds to the predictions made by Menant et al. (2020) based on numerical models, and could be related to episodic tectonic underplating (subducting slab stripping) beneath the coastal forearc area. Highlights: Recent uplift has been recorded for a million years by uplifted shores. Older shores and pediment draw a 12 Ma-long history of uplift and subsidence cycles. The total uplift since 12 Ma is ~1000 m. The cycle duration is ~4 Ma, which is similar to the results of Menant et al. (2020) Away from the Nazca ridge, uplift rates are up to 0.25 mm/a.