干旱区生态环境知识资源中心

Slope evolution in arid regions may result in the development of talus flatiron sequences at the foot of structural reliefs. A good example exists to the South of Zaragoza (Ebro Basin), where five stages of slope evolution have been identified in the talus flatiron sequences (S-1 to S-5, youngest to oldest). The deposits of these slopes 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-1) is post-19th century. The pottery remains of the previous one (S-2) indicate an age post-Middle-late Bronze (3.500-3.100 BP) and C-14 datings obtained for this accumulation are 2.529 +/- 52 BP and 2.930 +/- 60 BP. The talus flatirons S-3 have provided an age of 27.862 +/- 444 BP by C-14 and for S-4 the age is 35.570 +/- 490 BP. The oldest accumulation has not been dated. The extrapolation of the logaritmic equation fit from the talus flatiron profiles allows to calculate the scarp retreats. The data supplied indicate rates of scarp retreat of 0.9-1 m/1.000 years over the past 35.000 years.