An unconformity (specifically a disconformity) separates these two layers; it consists of erosional surface contact between them.

[1]: 262 The Pyawbwe Formation primarily consists of shale, which is poorly bedded and relatively soft and ranges from grey to bluish-grey in colour.

The lower part of the Pyawbwe Formation is mainly composed of relatively harder grey to brownish-grey shale, which is intercalated with thin-bedded, fine-grained, yellowish-grey sandstone.

[1]: 263 Based on the unconformity between the Okhmintaung and Pyawbwe Formations, and the absence of certain nannoplankton fossils in these rocks, it seems that the sea receded in the Minbu area at the end of the Paleogene, which is consistent with the general theory of a global drop in sea levels at that time.

[1]: 267 Based on fossils found in the Okhmintaung and Pyawbwe Formations, it seems that the Minbu area was a shallow marine shelf environment in Paleogene and Neogene times.