Datación Radiogénica (U-234/U-238, y Th-230/U-234) de sistemas travertínicos del Alto Tajo (Guadalajara).

Resum

Data of Th-230/U-234 and U-234/U-238 ratios and geomorpho/ogica/ and sedimentologica/ features of several travertine deposits of High Tajo river valley let us point out the evidence of at least four travertine genesis stage(s) > 350 ky has been interpreted as botton-valley travertine deposits, located along Dulce river and Rugui//a river valley. The second stage (—226 ky) are a/so a botton-valley travertine located at +8 —10 m. over Ruguilla river. Along Cifuentes river botton-va/ley and water-fall travertines has been dated as —90 ky. Subrecent travertine deposits of detrital, dam, water-fall types has been attributed to holocene epoch. Radiogenic data of these subrecent travertines has not been in account because uranium lixiviation and «detrita/ thorium» incorporation of travertine deposits may give a relative Th-230 enrichment and coherently the calculation of too great an age