Dating the Tejo river lower terraces in the Ródão area (Portugal) to assess the role of tectonics and uplift

摘要: Abstract The Tejo river is one of the major drainages in Iberian Peninsula; it a long-lived system (ca. 3.4 Ma) and provides an archive long-term landscape development environmental change controlled by tectonics, climate eustasy. most upstream Portuguese reach river, ∼ 200 km from Atlantic coast, shows evidence for five fluvial terraces (T1 to T5) with elevations reaching more than 120 m above modern bed. A chronological framework these established here integrating geomorphological, stratigraphical archaeological information ages luminescence dating. Optically stimulated dating K-feldspar, (involving correction anomalous fading signal), indicates that younger have probable age range of: T5 — 31 40 ka; T4 100 ∼ 280 ka. We deduce related changes are likely been as follows: ∼ 10 m aggradation ∼ 280 100 ka (0.06 m/ka); 14 m incision 40 ka (0.23 m/ka); 8 m 40 31 ka (0.89 m/ka); 16 m during last (0.52 m/ka). These values indicate duration rate both downcutting episodes were variable. There widespread neotectonic activity this intraplate region. Neither eustatic nor climatic Quaternary provide clear trends might explain observed pattern valley incision, thus we conclude tectonic driving mechanism. In study area, sediments deposited before beginning allows calculation time-averaged ∼ 0.07 0.10 m/ka over ∼ 2.6 Ma. This was probably determined increase relative uplift rate, resulting intensification compressive stress. During late Cenozoic stage, Rodao depression underwent less adjacent areas along which has incised narrow into basement rock, almost no terrace development. Terrace formation also promoted soft bedrock (Tertiary arkoses) impoundment alluvium behind resistant barriers crossed river. Geomorphological offset supported