Two loess formations of upper quaternary age in the brazilian nordeste

Abstract

Two sedimentary formations of eolian origin, composed of silt and loamy silt occur in the interior of the Brazilian Nordeste, several hundred kilometers to the west of the coast (fig. 1). The area is semiarid, dominated by the trade winds and prone to severe droughts under the present climate. Climatic conditions not very different to the present ones are postulated for the times of origin of both units. The older one is the Cariutaba Formation, red in colour, massive, friable, porous and loose. Absolute ages from 21 ky BP to 8.5 ky BP were obtained by TL methods. The younger loess is gray in colour, powderish, loose and underwent subfussion processes (piping). Late Holocene ages of ca. 2.60 to 2.20 ky BP were found in this unit.