ABSTRACT The "Andalusian Black Lands" (Chromatic Vertisols) are soils of great ecological and productive importance, emphasizes their fertility, however, their formation is still a reason for discussion. The main objective of this work was to analyze the most recent geomorphological and environmental evolution and the physical-chemical behavior of some parameters along its profile (Chromatic Vertisols). This study was conducted in Los Lirios wetland of the Guadalquivir basin (Seville, Spain). In addition, samples were obtained in an exploration of the bottom of this wetland for a study on pollen. Samples were obtained to a depth of 260 cm every 6 cm in the 120 cm upper soil layer. Physicochemical characteristics of samples were determined in the laboratory. A total number of 20 samples were evaluated, 11 of which correspond to the 65 cm of compact horizons submitted to tirsification. Radiocarbon dating (C14) was performed by Beta Analytic (Miami, Florida, USA). The results indicate the formation of a cumulative glacis and a subsequent environmental change towards more hydromorphic conditions might account for the surface and physical-chemical processes that characterize this alterological process, which generates soils of high ecological significance and agricultural productivity.