Holocene evolution of a rock‐bounded barrier‐lagoon system,Cíes Islands,northwest Iberia |
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| Authors: | Susana Costas Castor Muñoz Sobrino Irene Alejo Marta Pérez‐Arlucea |
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| Institution: | 1. Marine Geology Department, National Laboratory for Energy and Geology‐LNEG, Alfragide, Portugal;2. Department Bioloxía Vexetal e Ciencias do Solo, Universidade de Vigo, Vigo, Spain;3. Department Xeociencias Marinas e Ordenación do Territorio, Universidade de Vigo, 36200 Vigo, Spain |
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| Abstract: | Coastal geomorphology results from the combined effects of contemporary dynamics, sea‐level rise and the inherited geological framework, yet the relative importance of these driving mechanisms may change throughout the evolutionary history of coastal deposits. In this contribution, we analyse the depositional history of the Cíes Islands barrier‐lagoon system, based on lithofacies, radiocarbon ages, and pollen analysis. Our results reveal a sedimentary sequence that provides evidence for striking changes in the dynamical functioning of this complex since the mid‐Holocene. The sedimentary sequence commenced about 7700 cal years bp by fresh‐water ponding of an upland depression located about 4 m below present mean sea‐level. Fresh‐water ponds were infilled by aeolian sediments following a gradual lowering of the water‐table 4000 cal years bp . Post‐3600 cal years bp sea‐level rise allowed water oscillations to reach the elevation of the bedrock causing the inundation of fresh‐water ponds and subsequent lagoonal and marine sedimentation. Subsequently, landward and upward migration of a sand‐barrier led to overwash and deposition of sand in the newly formed lagoon. The resultant sedimentary sequence suggests that climatic conditions played an important role controlling the sedimentation regime during the entire history of the basin; changing water‐table levels during early stages of evolution and increasing storminess during more recent times. In addition, background sea‐level rise related to the Holocene transgression was a key factor in controlling the evolution of the system, yet its influence depended to an extent on the relative elevation of the bedrock topography. Copyright © 2009 John Wiley & Sons, Ltd. |
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| Keywords: | sea‐level change climate bedrock topography sand‐barrier lagoon |
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