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Sitha Formation
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Sitha Fm base reconstruction

Sitha Fm

Period: 
Ordovician

Age Interval: 
Middle-Late Ordovician


Province: 
Myanmar Shan Region

Type Locality and Naming

Shan North Plateau, Shan mid-Plateau (Pyin Oo Lwin), was defined by Aye Ko Aung (2012) after the village of Sitha which is about 16 km south of Pyin Oo Lwin, Mandalay region, although the name was used informally by Professor U Thein earlier. [Original Publication: Barber, A. J., Khin Zaw & Crow, M. J. (eds) 2017. Myanmar: Geology, Resources and Tectonics. Geological Society, London, Memoirs, 48, 317-342]


Lithology and Thickness

Limestone. It is a sequence of medium- to thick bedded, grey to dark grey or blue limestone, with burrow structures, and is therefore commonly known as ‘The Burrow Limestone’. Some oolitic limestones occur in places. Yellow, buff and purplish-brown silt patches are also visible on weathered surfaces.

[Figure: Stratigraphical log of the Sitha Formation, 0.5 km south of Sitha village, Pyin Oo Lwin township, Mandalay Division (Aung&Cocks, 2017)]


Lithology Pattern: 
Limestone


Relationships and Distribution

Lower contact

Conformable with Lokepyin Fm in Shan North Plateau and Shan mid-Plateau (Pyin Oo Lwin).

Upper contact

Conformable with Panghsapye Fm in Shan North Plateau, Conformable with Kunlein Fm

In Shan mid-Plateau (Pyin Oo Lwin).

Regional extent

This Fm is developed in Shan North and Mid Plateaus. The Sitha Fm is the same as the Lower Naungkangyi Series of La Touche (1913). This unit is correlated with the Wunbye Fm of Shan State South (Myint Lwin Thein 1973), the Kaki Bukit Limestone Fm of Pulau Langkawi and mainland Malaysia (Lee 2009), and the Thung Song Limestone Fm of southern Thailand (Wongwanich et al. 2002; Ridd 2011).


GeoJSON

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Fossils

The discovery of new species of straight-coned nautiloids (Actinoceras, Ormoceras, Armenoceras), the receptaculitid Fisherites burmensis (Rietschel & Nitecki) and the bryozoan Diplotrypa westoni Ulrich.

[Figure: Middle Ordovician fossils of the Sitha Formation. (a, b) Fisherites burmensis Rietchel & Nitecki; (c) Wutinoceras sp.; (d, e) Actinoceras sp.; (f ) Ormoceras sp.; (g) Armenoceras sp. (Darriwilian); (h, i) Diplotrypa westoni Ulrich, (h) transverse section; and (i) longitudinal section (Darriwilian) (after Aung&Cocks, 2017)]


Age 

Middle-Late Ordovician. Fossil evidences suggest a Darriwilian–Sandbian age for the Sitha Fm.[Figure: Stratigraphical correlation of the Cambrian–Devonian rocks of Myanmar Shan region with those of northern Thailand and NW Malaysia. Asterisks indicate the levels at which fossils useful in correlation were found (after Aung&Cocks, 2017)]

Age Span: 

    Beginning stage: 
Darriwilian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
469.42

    Ending stage: 
Sandbian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
452.75

Depositional setting

The presence of burrow structures, ripple marks and receptaculitids indicate deposition in shallow supratidal, intertidal and partly subtidal environments.


Depositional pattern:  


Additional Information


Compiler:  

Aye Ko Aung and L. Robin M. Cocks (Aung & Cocks, Cambrian–Devonian stratigraphy of the Shan Plateau, Myanmar (Burma), Chapter 14 in Barber, A. J., Khin Zaw & Crow, M. J. (eds) 2017. Myanmar: Geology, Resources and Tectonics. Geological Society, London, Memoirs, 48, 317-342).