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Francisco Lobo, CSIC-Instituto Andaluz de Ciencias de la Tierra (Spain)
Antonio Jabaloy, Universidad de Granada (Spain)
Patricia Bárcenas, IEO-Centro Oceanográfico de Málaga (Spain)
Antonio Azor, Universidad de Granada (Spain)
Luis Miguel Fernández-Salas, IEO-Centro Oceanográfico de Málaga (Spain)
Víctor Díaz del Río, IEO-Centro Oceanográfico de Málaga (Spain)
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The deltaic system of Adra River is found in the northern margin of the Alboran Sea, draining the Internal Zones of the Betic Mountais towards the Mediterranean Sea. The recent evolution of the system has been controlled by a number of human actions, which are modified in a significant way the natural behaviour of the deltaic system. The main goal of this communication is to discern the influence of anthropic activities versus natural change on the recent deltaic evolution, by integrating subaerial and submarine data.
According to supporting evidence, we distinguish the following evolutionary stages: 1) Initial interval of natural deltaic growth, from 4000 yr BC to 1872 AC, when a well-developed deltaic structure was formed, under the continued influence of abundant sediment supply. In the XIX century, sediment supply was favored by increased rain fall and by deforestation practices. As a consequence, a lobate depocenter with an undulated sea floor was generated in the western part of the prodeltaic environment.
2) Second interval when the fluvial channel was regulated, from 1872 to 1974 AC. During this interval, a new prodeltaic lobe was generated in the eastern part of the prodeltaic environment as a consequence of lateral deviation of the main fluvial channel. Two stages can be distinguished during this regulation interval: a) between 1872 and 1910 AC, when a highly steep, laterally continuous deposit was formed at the eastern termination of the prodelta; b) between 1910 and 1974 AC, when a second channel readjustment placed the river mouth in its present position; as a consequence, a new deposit developed just in front of the river mouth.
Coastline evolution data suggest that sediment supply was also high during this regulation interval. The submarine morphology, however, shows a considerable lower development of the prodeltaic deposits. The high steepness and moderate to low extension of the sediment body are indicative of erosion and/or significant lateral redistribution.
3) Last interval from 1974 AC to present-day, when sediment input was dramatically reduced, leading to widespread erosion of the most recent deltaic lobe.
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