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Universiteit van Amsterdam (2015)

Landscape reconstruction linking tectonics and climate using sedimentological data in SE-Spain

Mastwijk V.B.

Titre : Landscape reconstruction linking tectonics and climate using sedimentological data in SE-Spain

Auteur : Mastwijk V.B.

Université de soutenance : Universiteit van Amsterdam - Institute for Biodiversity and Ecosystem Dynamics (IBED)

Grade : Master programme : Geo-ecological Dynamics 2015

Résumé
The Betic Cordillera is a mountain chain dividing the African and the Iberian plate making it a tectonically highly active region and an interesting study area. Especially the area west of the Lorca Basin in south eastern Spain is not completely explored in a sedimentological sense in combination with landscape evolution. Geologically speaking the area can be divided in carbonates from the Iberian shelf, clastic rocks from the Internal Zone and the infill of the basin in between. Besides geology and tectonics also the climate has changed considerably with several arid periods and temperature shifts. Furthermore, the research area has been affected substantially by tectonic activity where tectonic uplift lead to river blockage and the creation of lakes. This research aims to reconstruct the landscape by analysing the sedimentology of the area. The role of climate and tectonics was researched by looking at sediment depositions, especially near the three major rivers ; the Luchena River, The Rio Turillo and the Rio Velez. Also the different river terraces present within the study area where compared with terrace datings of other researches just upstream and downstream. The grains found within the fluvial deposits were determined for the different rivers found within the area. The grains were compared to the lithological units present in the area to determine the provenance. By using ArcGIS several maps and graphs were constructed, including a sediment map, a geomorphological map, a geological map and length profiles of the rivers. An assessment was made to check the correlation between slope angle, grain size and sorting. The Geomorphological area was split into seven areas based on similar units that could be grouped together. The sediment map was based on this map with geomorphological units being transferred into sediment classes with different grain sizes and sorting. The sediments in several parts of the research area showed a sudden shift of lacustrine deposition to fluvial deposition. This is caused by the presence of several paleo-lakes due to blockage caused by the location of bedrock ridges. After the obstacles enclosing the lakes were breached or overflown, fluvial activity resulted in fluvial deposition and erosion. The importance of tectonic activity is seen in the avoidance of the Rio Velez of flowing through the Internal Zone and its preference to flow in the fault separating the Internal Zone from the rest of the area. Furthermore, the longitudinal river profile of the Luchena River displays to concave parts where the lower part is connected to the current base level. The upper concavity is likely related from before the area around the Puentes Reservoir was uplifted. Dating of the sediments was only partially possible with an estimation for several layers. Therefore, the role of climate was difficult to assess. However, a colder, wetter climate was deducted for a period between 13,8 and 9,5 ka BP. Also, the rivers will likely be influenced by tectonics and climate in the future as they have been in the past. In future research, the use of dating is evident for understanding the processes that played a part in the past and acquiring the correct time frame of events. More observations of the sediments near the rivers are needed to fill in the gaps left in this study. Furthermore, the climate record needs more research to achieve more consensuses of climatological data for at least the last 18000 years.

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Page publiée le 6 novembre 2016, mise à jour le 17 octobre 2018