From Lower Albian to Santonian times the counterclockwise rotation of the Iberian Plate resulted in a number of periods of rifting and relative falls in sea level. During the Middle Albian, these events brought about an important influx of siliciclastic sediments within a deltaic-estuarine system that deposited the Escucha Formation. Significant coal deposits have been recorded in freshwater swamp plain (upper delta plain) and brackish water swamp (lower delta plain) environments. The distribution and thickness of the workable coal of the study area are controlled by the stratigraphy, paleogeography, sedimentology, and tectonic structure. These coals, which have been classified as mainly subbituminous, are characterized by their high sulfur content (6 to 7.3 percent dry basis average of worked coal). The study of the sulfur content of the coal seams of the Castellote and Calanda Sub-basins reveals three types of sulfur distribution: vertical variation within individual coal seams, stratigraphic variation, and lateral variation within the basin. These three types of sulfur distribution have two principal controlling factors; the sedimentologic setting and external factors, the latter probably due to the leaching of the sulfur of pre-Cretaceous evaporites.