Isostatic compensation in the Western-Central Betic Cordillera (South Spain) caused by erosional unloading from the Messinian to the presentThe Emergence of an orogen

Abstract

In the Western-Central Betic Cordillera (WCBC), the Messinian Salinity Crisistriggered and important fluvial denudation, removing millions cubic meters of rocks from the Mediterranean slope of the emergent orogen. We offer an evaluation of the subsequent isostatic response calculating in a GIS environment the geophysical relief (gr) values (denudation plate and continuous models) and also surface uplift (Airy isostasy) for 48 drainage basins (spatial isostatic units). Higher gr (major denudation) values are obtained consistently at the Mediterranean side of the ancient water divide (328-465 m) and noticeable lower (<235 m) in the Atlantic slope. The obtained gr models show a similar asymmetric distribution. Comparison with published uplift models based on stratigraphic markers and landforms in the zone confirms that near the 45-50% of the total uplift of the WCBC was triggered during the MSC. Calculated surface uplift for the Mediterranean (291 ±20 m) and Atlantic (179 ±20 m) slopes indicate uplift rates during the MSC of 0.18 mm/yr in the Mediterranean (practically null in the Atlantic). Consequently, isostatic uplift caused by fluvial erosional unloading can be identified as one of the main proces controlling the landscape evolution in the zone during and after the MSC.