growth rings are described in gymnosperm woods of the victor szlápelis forest, salamanca formation, lower paleocene of the chubut province, argentina. this forest is composed by a large number of petrified trunks of parautocthonous provenance. the presence of trees with more than 1 m in diameter suggests an exuberant growth and good environmental conditions for tree development. associated sediments suggests that fossil trees were developed in a stable environment related with fluvial to deltaic characteristics. tree-ring methods are used to study the growth characteristics of these gymnosperms. wood anatomy and characters associated to the growth records indicate that climate was warm-temperate and humid, with a dry summer and a wet spring.