The Thanh Thuû – Pha H¸n Section has been described as the hypostratotype. The Hµ Giang Formation is composed of terrigenous - carbonate sediments, which are of littoral shallow marine and rather stable facies with abundant bottom fauna as Trilobites, Brachiopods etc. and green Algae (Microphytolites). Its lower boundary is not exposed and its basal part is metamorphosed.

In the upper part of the formation characteristic fossils have been found, including Paracoosia - Annamitia zone and Damesops - Damesella zone (Ngäc §­êng section), Damesops - Damesella zone (Pha Han section), Lingulella - Westonia - Palaeobolus and Solenoparia - Ptychoparia zones (Pha Long section) belonging to late Middle Cambrian. The Hµ Giang Formation underlies conformably the Chang Pung Formation containing the Cyclolorenzella - Blackwelderia - Drepanura basal zone (Chang Pung and Pha Long sections).

The Hµ Giang Formation has close relation with the S«ng M· Formation in Northwest ViÖt Nam and can be correlated with the Longha Formation in Southeast Yunnan of China.