Pedosedimentary and palaeoenvironmental significance of a Holocene alluvial sequence in the southern Pampas, Argentina

A representative section of the Holocene alluvial record of the southern Pa mpas (Argentina) comprises a sequence of elastic sediments, a diatomite and two palaeosols. Detailed macro- and micromorphological descriptions provid e the basis for the reconstruction of its pedosedimentary history. Combinin g the pedosedimentary reconstruction with palaeoecological data allows a de tailed overview of alluvial landscape development and associated palaeoenvi ronmental change in the region during the Holocene. The early-Holocene shif t from a subhumid dry to humid climate was marked initially by a diminution in clastic sedimentation, the development of the Puesto Callejon Viejo Soi l and then re-establishment of fluvial aggradation with a dominance of bioc lastic sedimentation. Loess inputs increased during the mid-Holocene as the climate reverted to subhumid dry, and temporary subaerial exposure of the sediments led to the formation of the Puesto Berrondo Soil. More variable e nvironmental conditions followed with natural fluvial aggradation ceasing i n the late Holocene, though aeolian sedimentation has continued until the p resent day. The resultant surface accretionary soil has been modified by re cent alluvial inputs from Rood events linked to agricultural disturbance in adjacent catchments.