A mineralogical study and multivariant geochemical analysis have been carried out to determine the sedimentation processes and the influence of surrounding rocks on sediments. Analyses were made on the clay fraction of sediments and on bulk samples of rocks from nearby reliefs in the Sorbas Basin (SE Spain). Source rocks were identified by statistical analysis of trace elements and by comparison of the crystallographic parameters of phyllosilicates in sediments and supposed sources. Palaeoenvironmental conditions are recorded by specific elements in the clay minerals. The study of the B and Mg content and of the different types of smectites and palygorskite found in distinct areas has permitted a description of these conditions for this Basin. In this way, different types of deposition environment, showing varying degrees of confinement and influence from marine or continental water, have been distinguished.