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Chronology and paleoenvironmental interpretation of talus flatiron sequences in a sub-humid mountainous area: Tremp Depression, Spanish Pyrenees


Correspondence to: Carles Roqué, Àrea de Geodinàmica Externa i Geomorfologia, Universitat de Girona, Campus Montilivi, E-17071, Girona, Spain. E-mail:


Talus flatirons are debris-covered relict slopes, disconnected from the source area, which are relatively common in arid and semi-arid areas. Talus flatiron sequences record the alternation of accumulation and incision phases. These chronosequences may be used for infer temporal changes in the morphogenetic processes acting on the slopes as well as information on the local paleoclimatic history. Talus flatiron sequences developed in the Tremp Depression, eastern Spanish Pyrenees, are analysed from the geomorphological, chronological and paleoenvironmental perspective. The two groups of relict slopes differentiated by means of detailed geomorphological mapping have been dated by optically stimulated luminescence (OSL) and radiocarbon dating at 25–20 kyr (S3) and 5·4–1·7 cal kyr (S2). The talus flatiron group S3 is correlated with a fluvial terrace of the Noguera Pallaresa River (c. 23 kyr bp). The comparison of the ages obtained in the Tremp Depression with chronologies published for talus flatiron sequences in semi-arid areas and other paleoclimatic proxies suggests that the aggradation phases in the slopes occurred during periods with higher humidity and vegetation cover. The chronological differences observed between semi-arid Spain and the Tremp Depression may be partly related to the more humid climate of the latter mountain area. Copyright © 2013 John Wiley & Sons, Ltd.