The timing of Quaternary phases of fan development and soil formation in the semi-arid SE Spain (Eastern Betic Cordillera)

Resumen

This work uses the set of available regional geochronological data (OSL, TL, 14C, Th/U) on alluvial sediments, cal- cretes and soils for the semiarid SE Spain to build a theoretical timescale for the most important phases of sedimentation and soil formation occurred in the zone from the Middle Pleistocene to the Holocene. Most of the data come from the set of paleo- seismological and paleoclimatic research carried out in the regions of Murcia and Almeria over the past 15 years. The gathe- red geochronological data set has 122 dates, 36 for calcic soils and calcretes and 86 for sediments and covers the last 400 ka. The analysis is based on the construction of age-frequency distribution functions discriminating periods of 5 ka, which offer sufficient resolution to distinguish among different Oxygen Isotopic Stages (OIS) occurred during the period of analysis. The analysis excludes age-data for the last 5 ka, since the large number of records published for this time-period will produce an anomalous peak. A detailed study of the Holocene data is presented in another contribution. Calcretes appears as elements developed during the last stages of warm isotopic stages (OIS 9 to 1), whilst sedimentation dominated during the transition between warm-cold isotopic stages, especially during terminations II to I, coinciding with deglaciation periods.