Climatic cycles inferred from the aminostratigraphy and aminochronology of Quaternary dunes and palaeosols from the eastern islands of the Canary Archipelago

Aminochronological and aminostratigraphical methods have been used to study the Quaternary a e o l i a n deposits f r om the islands located east of the Canary Archipelago (Fuerteventura and Lanzarote islands and La Graciosa , Montana Clara and Alegranza islets). T h e extent of racemisation/ epimerisation of four amino acids ( isoleucine , aspartic acid , phenylalanine and glutamic acid) was measured in land snail shells of the genus Theba. The age calculation algorithms of these amino acids h a v e b e e n determined to permit t he numerical dating of these deposits. Eight A m i n o z o n e s , e a ch defining dune/palaeosol-formation episodes, have been distinguished and dated at 4 8 . 6 ± 6 . 4, 42.5 ± 6 . 0 , 37.8 ± 4 . 6 , 29.4 ± 4 . 8 , 22.4 ± 4 . 5 , 14.9 ± 3.6, 11.0 ± 4 . 0 and 5.4 ± 1.1 ka B P , t h e first f i ve of t h em defining c y c l e s of 5 - 7 ka. The alternation of palaeosols and a e o l i a n deposits, w h i c h are related to abrupt transitions from humid to arid conditions, are t he reflection of globally induced changes in North Africa palaeoenvironmental conditions linked to the effect of African palaeomonsoons on the trade w i n d s and the Saharan Air Layer. Probably these a eolian cycles , with a recurrence neriod of 5 - 7 ka. are t he expression of multiples of the ~ 2 . 4 ka solar-cycle