The Marismas Formation is the upper part of the sedimentary infill of the SW sector of the Guadalquivir basin. Previous chronological data of the Lebrija core sediments, indicated that the age at the top of this formation was 9.6 kyr BP and the bottom, 60 m, is near or beyond the range of radiocarbon, but post Matuyama - Brunhes reversal. In this work we present 17 new ages coming from the analysis of racemization of amino acid on valves of ostracods, in order to complete the chronology and the age-depth model of the Marismas Formation. The results indicates that the section located below the meter 56, throws ages ranging between 164685±14110 and 202830±30255, which correlates with the marine isotope stage MIS6-7 Middle Pleistocene, significantly lower in age than described in other parts of the lower Guadalquivir basin.