Laungshe Fm

Chindwin Basin, this name is adopted by Cotter in 1915 to shales exposed at a section in south of the sheet 84 k/4 in an area where Laungshe is the principal village. In Minbu-Salin Basin, Laungshe area. [Original Publication: Barber, A. J., Khin Zaw & Crow, M. J. (eds) 2017. Myanmar: Geology, Resources and Tectonics. Geological Society, London, Memoirs, 48, 219–260]

Synonym: Laungshe Shales

[Figure: Map showing location of sub-basins of the Central Myanmar Basin (after Myint Thein and M. Maung 2017)]

Sandy claystone. Consists of mainly soft blue-grey shale, interbedded with yellow-brown, fine-grained sandstone and carbonaceous pack–wackestone lenses. The predominant beds are dark grey, well bedded, and often concretionary shales. Thin layers of sandstone occur throughout the series, but in the upper horizons those amounts to several hundred feet in thick. Tracing them laterally it was found that they were inconstant and passed into shales. In Minbu-Salin Basin and Pyay Embayment, it is sandy claystone. The Fm consists mainly of shales, interbedded with a few sandstone and fossiliferous limestone beds (packstone and wackstone). The shales are dark-grey, laminated to nodular, carbonaceous and interbedded with argillaceous sandstone beds.

[Figure: Stratigraphic succession of the Chindwin Basin (after Than Htut, 2017)]

Thin layers of selenites are abundant throughout the Laungshes, and traces of fragmentary and unidentifiable fossil plants are found in Chindwin Basin. Contains the fossils Nummulites atacicus, Assilina glanulosa (fore-reef facies), Rotalia spp., Alveolina spp., Alveolina oblonga and A. elliptica (lagoonal facies) in Minbu-Salin Basin and Pyay Embayment.

Deposited in a pro-delta environment in Chindwin Basin, deposited in shelf to deep-marine environments in Minbu-Salin Basin and Pyay Embayment.