摘要:A detailed stratigraphy description and measurements of the sedimentary facies within the Halang Formation has been carried out to provide a thorough assessment of the architectural facies and depositional environment. The study area is located along the Tajum River in the District of Gumelar, Banyumas, Central Java-Indonesia where most of the Halang Formation is preserved in a good condition. Three cycles of facies association from basin plain, in channel to channel overbank deposits were able to be determined from the formation which indicate very active changes of sub-depositional environment that related to transgressive response influenced by the local tectonic during sedimentation takes place.