Evidence of Holocene climatic changes from Aeolian deposits in Baja California Sur, Mexico

Well-defined Late Pleistocene and Holocene dune fields are present on the s urface of the Purisima-Iray Magdalena sedimentary basin and on top of barri er islands of the Magdalena Lagoonal Complex in Baja California Sur, Mexico . Thermoluminescence, amino acid epimerization, and radiocarbon techniques were used for dating dune sands and shell samples respectively. During Late Pleistocene to early Holocene (14 to 8 ka BP) mega-barchans and linear dun es were formed. During early Holocene through middle Holocene (warm-dry cli mate) dune fields were still active, At about 5 to 6 ka BP the stabilizatio n of sea level developed the present lagoonal system in the area. Sandy bar rier islands capped by foredunes were developed. At this time coastal dunes were eroded, and in part inundated, forming large flooding flats and sabkh a deposits in the old inter-dune areas. During late Holocene, after the lag oonal system was fully developed, dunes were emplaced along the lagoonal co asts. The presence of some younger dates in older deposits seems to represe nt dune reactivation. (C) 1999 INQUA/Elsevier Science Ltd. All rights reser ved.