The clay mineralogy of a set of Tertiary marine sediments from the Internal Subbetic of the Betic External Zone was examined. Two types of sedimentary environment were distinguished: a platform environment consisting of limestones, marls, organogenic limestones, conglomerates and silexites distributed heterogeneously in time and space; and deep environments, where the sedimentation consisted of marls, marly limestones, marly clays and silexites, with no sedimentary gap. A third group of sediments studied belongs to the Águila Complex, with mineralogical and stratigraphic characteristics very similar to the platform sediments. This third type of sediment is found in the sediments of the Campo de Gibraltar Complex as large, disperse blocks resulting from tectonic activity. A very similar mineral association was observed in all three domains, consisting of smectite, illite, mixed-layer I-S, kaolinite and lesser amounts of palygorskite and chlorite. Materials mainly derive from the erosion of Mesozoic sediments, and sedimentation was controlled by the compressive tectonics of the region.