Facetas triangulares de ladera como indicadores paleoclimáticos en ambientes semiáridos (Depresión del Ebro)

Abstract

Talus flatirons are relic slope accumulations preserved at the foot of structural platforms and mesas. The generation of talus flatiron sequences involves alternating accumulation and incision periods indicating clear changes in the activity of the geomorphological processes. A good example exists to the South of Zaragoza within the Ebro Basin, where five stages of slope evolution have been identified in the talus flatiron sequences (S, to Sy youngest to oldest). The deposits of these slope accumulations contain pottery remains, charcoal and ashes which permit to carry out relative and absolute datings of the slope accumulations. Based on the pottery content, the most recent accumulation stage (S) is post-19th century. The pottery remains of the previous one (SJ indicates a post-Middle-Late Bronze and the 14C datings obtained for this accumulation are 2.529±52 BP and 2.930±60 BP. The talus flatirons S3 has provided an age of 27.862±444 years BP by UC and for the S4 the age is 35.570±490 BP. The oldest accumulation has not been dated. The datings allow to correlate the accumulation stages with cold climatic periods of the Upper Pleistocene and Holocene. These cold periods alternate with warm climatic periods during which the dominant water erosion isolates the talus flatiron