Minbu Township () is a

township A township is a form of human settlement or administrative subdivision. Its exact definition varies among countries. Although the term is occasionally associated with an urban area, this tends to be an exception to the rule. In Australia, Canad ...

Minbu District Minbu District is a district in western Magway Region in central Myanmar.Magway Region Magway Region (, ; formerly Magway Division) is an administrative divisions of Myanmar, administrative division in central Myanmar. It is the second largest of Myanmar's seven divisions, with an area of . Pa-de Dam (ပဒဲဆည်) is one of ...

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

. The principal town is Minbu. The township is home to the Shwe Settaw Pagoda, which holds an annual

pagoda festival Pagoda festivals (; ''paya pwe'') are regular festivals found throughout Myanmar that commemorate major religious events in pagoda's history, including the founding of a pagoda and the crowning of the pagoda's hti (umbrella). Pagoda festivals are ...

from the fifth waning day of

Tabodwe Tabodwe () is the eleventh month of the traditional Burmese calendar. Festivals and observances *Full moon of Tabodwe **Htamanè, Harvest Festival () **Mon National Day Rakhine people, Rakhine tug of war festival, Yatha Hswe Pwe. *Pagoda festiva ...

to the Burmese New Year, attracting 100,000 pilgrims nationwide.

Geology

Rocks belonging to the Pegu Group, dated to

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

and

Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...

times, are well-exposed in the western part of Minbu Township, where they form the western margin of the Minbu Basin and the Prome Embayment. This margin extends from the western part of

Pakokku District Pakokku District (, ; also Pagukku District) is a district of the Magway Division in central Myanmar (Burma). It is situated in northern part of Magwe Region. The administrative centre is the city of Pakokku. Pakokku is a largest city of M ...

south through Minbu Township and then into

Mindon Township Mindon Township () is a township of Thayet District in the Magway Region Magway Region (, ; formerly Magway Division) is an administrative divisions of Myanmar, administrative division in central Myanmar. It is the second largest of Myanmar's se ...

to the south. The two main

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

s in the Pegu Group in this area are the Pyawbwe Formation and the Okhmintaung Formation. The Pyawbwe Formation, which is dated to Neogene times, makes up the upper layer. Below that is the Okhmintaung Formation, which is dated to Paleogene times. An

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

(specifically a

disconformity An unconformity is a buried erosion surface, erosional or non-depositional surface separating two Rock (geology), rock masses or Stratum, strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer ...

) separates these two layers; it consists of erosional surface contact between them. Both formations are well-exposed in a stream north of the village of Pyawbwe and along the Mann Chaung stream between the villages of Uyin and Kodaung. The Okhmintaung Formation generally consists of massive- to thick-bedded

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

, with lesser amounts of

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

, thin conglomeratic sandstone, and thin-bedded

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

. Fossils of

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

s and shell fragments are found in the sandstone bed. In the upper part of the Okhmintaung Formation, there are features like

evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as oce ...

s and

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...

. The Pyawbwe Formation primarily consists of

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

, which is poorly bedded and relatively soft and ranges from grey to bluish-grey in colour. Thick-bedded sandy shale is intercalated in this formation and ranges from grey to yellowish 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. 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. Sea levels then rose and submerged the area again in the Neogene. 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. In particular, the algae family '' Braarudosphaeraceae'' is an especially prominent indicator of near-shore conditions. Sandstone deposits in the Okhmintaung Formation likely represent tidal channel deposits, while intercalated mudstone and sandstone deposits inn the Pyawbwe Formations likely represent a sub-tidal environment.

References

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