A lot of unconformities and stratigraphic gaps have been discovered in the Paleozoic and Mesozoic stratigraphy of Bac Bo region (North Viet Nam), but their role in the regional geology was not accessed yet in detail. This paper is the first attempt to describe the most significant unconformities and stratigraphic gaps and discussing their role in regional geology. The most important is the angular unconformity of Norian-Rhaetian formations upon various formations of different formations; it marked the change tectonic regime of the region resulting from the indosian orogeny in Viet Nam and in Southeast Asia in common. The gap of Lower Devonian red beds formations (Si Ka Formation, Song...
