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Change on the coastline of the Southern Alicante region
Tent-Manclús, J. E.
The Bajo Segura Region is a plain dominated by the Segura River with the mouth towards the Mediterranean Sea on Guardamar. The Hondón and Salinas de Santa Pola lagoons inside the plain, are the remains of a major marine bay known in the Roman times as the sinus ilicitanus. Offshore the Region geophysical data has permitted to model the coastline change and study the underwater marine terraces. 183 maps have been made from the 15000 BP until Today (100 year apart the older ones and 25 years for the recent ones). The coastline has migrated between 20 and 50 km onshore and then offshore about tens of meters to 35 km shaping today coastline. The sea level at 15000 BP was located 70 m below today sea-level (btsl). During the Younger Dryas (13500 to 11700 BP) varies around 60-66 m btsl then increase until 21 m btsl and stopped during the 8.2 ka event (8500 BP to 8200 BP). Again, the level increases first fast and then slowly but moving fast horizontally (near 35 km for 1000 years) developing the sinus ilicitanus when the marine transgression enters the plain about 4200 BC. The Segura River developed a delta in the today area of Orihuela, 35 km to the East of its today river mouth in Guardamar. The river until around the year 1400 AD developed a fingering (bird-foot) quite variable delta in the center of the sinus, most of the major irrigation canals (acequias) could correspond to the ancient delta-channels. Around the XV century major events changed the sinus basin producing the river mouth move to the present location. The sinus open communication with the Mediterranean Sea was closed around the XVIII century by sand bars, first the southern of Guardamar and then the northern on Santa Pola.
The change of the coastline in the southern part of the province of Alicante for the last 15,000 years have been modeled and described in the work of Tent-Manclus (2013). It is obtained by integrating data from different sources and especially high-resolution seismic profiles of the nearby marine continental shelf. Ten periods have been distinguished in the evolution of the Bajo Segura coastline : 1) 15000 BP- 14600 BP: rapid rise; 2) 14600 BP to 13500 BP: the Older Dryas, slow rise; 3) 13500 BP to 12700 BP: stability and descent; 4) 12700 BP to 11700 BP: the Younger Dryas, descent of the sea level; 5) 11700 BP to 11300 BP: very fast rise; 6) 11300 BP a 8500 BP: rapid rise; 7) 8500 BP = 6500 AC to 8200 BP = 6200 AC: 8.2 ka event stabilization; 8) 6,200 BC to 4,000 BC: rise, Tabarca Island is form; 9) 4000 BC to 3000 BC: the slow rise due to subsidence sinus ilicitanus forms and 10) 3000 BC to the present day 2000 AD: the sinus ilicitanus desiccates.
Maps at different times are show selected from the 164 maps that have been made. This is a first version of how the coastline evolves in the region. This work It can be a starting point to improve knowledge of the historical landscape evolution..
The sinus ilicitanus dries until today, the rest of which are the lagoons of the Fondo and Santa Polo Salinas.
Cite as: Tent-Manclús, J. E. (2013): Cambios de la línea de costa en el Bajo Segura (S de Alicante) en los últimos 15.000 años. Estudios geográficos, 74 (275): 684-702. Doi: 10.3989/estgeogr.201324