Fluvial terraces of the northwest Iberian lower Miño River.
Viveen, W. ; Schoorl, J.M. ; Veldkamp, A. ; Balen, R.T. van; Vidal-Romani, J.R. - \ 2013
Journal of Maps 9 (2013)4. - ISSN 1744-5647 - p. 513 - 522.
sea-level change - tectonic activity - portugal - uplift - climate - reconstruction - pleistocene - evolution - incision - deposits
A new fluvial terrace map with a tectonic framework for the northwest Iberian lower Miño River is presented. It is the first integrated map to cover the entire lower, 67-km reach of the Miño River, and to cover both the Spanish and Portuguese side of the river. The map is presented at a scale of 1:200,000, although its features were mapped at a scale of 1:5000. Various map layers can be viewed, such as a digital elevation model (DEM), fluvial sediment thickness layers, a palaeoflow direction layer, a lineament and fault layer, and two terrace and tectonic basin layers, showing up to 10 fluvial terraces and a floodplain level. Interpretation of the map shows that next to regional tectonic uplift and glacioeustacy, local basin subsidence and small-scale block movement are very important for the fluvial network, localised fluvial terrace formation, and preservation.
A 0.65 Ma chronology and incision rate assessment of the NW Iberian Miño River terraces based on 10Be and luminescence dating
Viveen, W. ; Braucher, R. ; Bourlès, D. ; Schoorl, J.M. ; Veldkamp, A. ; Balen, R.T. van; Wallinga, J. ; Fernandez-Mosquera, D. ; Vidal-Romani, J.R. ; Sanjurjo-Sanchez, J. - \ 2012
Global and Planetary Change 94-95 (2012)aug-sept. - ISSN 0921-8181 - p. 82 - 100.
optically stimulated luminescence - low-accumulation shelf - fluvial terraces - late pleistocene - southern england - sea-level - cosmogenic radionuclides - northwestern spain - last deglaciation - tectonic activity
In this work a series of 5 luminescence and 10Be dated fluvial terraces of the Miño River (NW Iberian Atlantic Margin) is presented. The outcomes allowed answering the longstanding question whether the Miño valley infill has a fluvial or marine origin. The perfect exponential decrease in 10Be concentrations with depth and a progressive increase in age with terrace altitude indicate that the Miño terraces are fluvial terraces rather than terraces incised in older marine basin infill. Accurate dating of the terraces was difficult due to saturation of the luminescence signal and high inheritance of 10Be concentrations. Nevertheless, minimum ages of up to 650 ka could be determined and are very likely close to the real ages of the terraces. The age estimations and field evidence suggest that terrace formation and terrace incision occurred during eccentricity-forced cycles of glacio-eustatic sea level changes and tectonic uplift. The occurrence of a steep and narrow continental shelf probably favoured rapid and profound incision by the Miño River during periods of low sea levels. It is furthermore hypothesised that the transition periods between glacials and interglacials were especially important for terrace deposition and incision. Denudation rates of the terraces were calculated from the 10Be data and do not exceed 1.30 m Ma- 1. These extremely low rates are probably the result of a combination of factors that favoured terrace preservation. Large, flat terrace surfaces with high permeability and continuous vegetation cover during the Quaternary stabilised the terrace surfaces. Maximum incision rates, calculated from terrace age and altitude, are 0.07–0.09 m ka- 1. These values can be used as proxies for tectonic uplift rates. They are in agreement with published uplift rates along the northern Spanish coast and the westernmost termination of the Cordillera Cantabrica. This similarity most likely identifies a common tectonic regime leading to similar tectonic uplift rates. The results demonstrate that tectonic uplift occurs in a region that was until very recently considered as tectonically stable.