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Kuchma Formation
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Kuchma Fm base reconstruction

Kuchma Fm

Period: 
Permian

Age Interval: 
Early Permian


Province: 
Bangladesh NW

Type Locality and Naming

The name Kuchma Formation was proposed by T Ahmed and MA Zaher for the subsurface section at Kuchma (24°42'N; 89°16'E) in the district of Bogra from subsea depth of 2,364 to 1,858 m.

Synonyms: Barakar stage and Barakar Series.


Lithology and Thickness

Glacial till followed by Coarse-grained sandstone. The formation is composed of sandstone and grit, with subordinate shale and is interbedded with coal seams. Five coal seams of 6, 22, 13, 4, and 6 m are present in the type section. The formation is 495 m thick. Tillites are at the base.


Lithology Pattern: 
Coarse-grained sandstone


Relationships and Distribution

Lower contact

The Kuchma Formation lies unconformably over the basement complex.

Upper contact

The Kuchma Formation lies conformably under the Paharpur Fm in the shelf facies of Bangladesh.

Regional extent

Precambrian platform region (NW Bangladesh). These Permian sediments (Kuchma-Paharpur) were deposited in the faulted basins of the Pre-Cambrian era and attained considerable thickness. The presence of this formation has not been reported from any other drill holes in the Bogra-Rajshahi area.


GeoJSON

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Fossils


Age 

"The rock unit is tentatively correlated with the Barakar Stage (Barakar Fm) of the Lower Gondwana Group in India, which is of Early Permian age. However, this correlation is done without any biostratigraphic information. It is problematic to make correlation solely based on lithology. The results of coal petrographic analyses, which could at least roughly date the various coal seams, are also not available. Considering these facts Klaus-Ulrich Reimann placed this unit in the next higher stratigraphic division, ie the Damuda Series (= Barren Measures Fm ?)." [Notes by JimOgg: Barakar through Barren Measures = late Artinskian through Middle Permian; but Barakar Fm itself is only upper half of Artinskian. Glacial till at base probably implies basal portion is Sakmarian glacial episode?" Conformable under Paharpur Fm, which is Wuchiapingian, implies extends to uppermost Capitanian. This suggests there may be numerous internal breaks, not continuous accumulation.]

Age Span: 

    Beginning stage: 
Sakmarian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
293.52

    Ending stage: 
Capitanian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
259.55

Depositional setting

" The tillites at the base of the Gondwana Group indicate that sedimentation followed a

major glaciation in the region; and the Gondwana coal measures also suggest that deposition occurred under cold to cool climatic conditions (Wardell, 1999). The tillites consist of boulder beds with clasts of unsorted sedimentary, igneous and metamorphic rocks interbedded with occasional units of mudstone, siltstone and coal, indicating interglacial sedimentation."


Depositional pattern:  


Additional Information


Compiler:  

Largely copy-pasted from Banglapedia (National Encyclopedia of Bangladesh as compiled by several geologists; http://en.banglapedia.org/index.php/Geological_Group-Formation; 2015)

PLUS, quotes from Md. Alam et al. (2003, "An overview of the sedimentary geology of the Bengal Basin in relation to the regional tectonic framework and basin-fill history", Sedimentary Geology, 155: 179-208.)