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Ratnagiri Formation
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Ratnagiri Fm base reconstruction

Ratnagiri Fm

Period: 
Neogene

Age Interval: 
Early-Middle Miocene


Province: 
W.India Mumbai Offshore

Type Locality and Naming

Well R – 2 – 1, (depth interval 453 - 796m). [Original Publication: Basu, D.N., Banerjee, A and Tamhane, D.M. 1982. Facies distribution and petroleum geology of Bombay Offshore Basin, India. Journal Petroleum Geology, Volume 5, pp. 57-75.]

[Figure: Lithostratigraphy in Mumbai Offshore blocks (from NDRDGH.gov.in; after Jitendra Misra, 2009)]


Lithology and Thickness

Limestone. Monotonous limestone sequence with thin shale layers. In the type section, the limestone is predominantly biomicritic with moldic and vugular porosity. The shale is pyritiferous. In the type area, it is only 343 m thick. The thickness gradually increases towards the north Ratnagiri and DCS areas up to 1500 m.

[Figure 1: Formations and their reference sections in Mumbai Offshore Basin (after Pandey and Dave, 1998)]


Lithology Pattern: 
Limestone


Relationships and Distribution

Lower contact

Unconformable onto the Alibag Fm or the Panvel Fm.

Upper contact

The upper contact of the Ratnagiri Fm with the Chinchini Fm is sharp and unconformable.

Regional extent


GeoJSON

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Fossils

In type well, top of the Ratnagiri Fm coincides with the highest occurrence of Miogypsina antillea / Cycloclypeus indopacificus.


Age 

Early to Middle Miocene age.

Age Span: 

    Beginning stage: 
Aquitanian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
23.04

    Ending stage: 
Serravallian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
11.63

Depositional setting

The formation was deposited under shallow shelf lagoon to shallow open shelf environment. In the Ratnagiri area, the formation was deposited over a carbonate platform, flushed by minor tidal channels and frequently exposed to swampy and subaerial conditions.


Depositional pattern:  


Additional Information


Compiler:  

D.S.N Raju