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Chinchini Formation
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Chinchini Fm base reconstruction

Chinchini Fm

Period: 
Neogene

Age Interval: 
Pliocene to Recent


Province: 
W.India Mumbai Offshore

Type Locality and Naming

Well SS-1, (depth interval Seabed – 1700 m). [Original Publication: Rao, R.P. and Talukdar, S.N., 1980. Petroleum geology of Bombay high field, India. Journal name , volume pp: 487-506.]

Synonyms: A predominantly clastic sequence, disconformably overlying the Bandra Fm was informally referred as Chinchini Formation by Rao and Talukdar (1980). Basu et al., (1982), referred this unit as the Tarapur Formation. Since the name Tarapur preoccupies in the stratigraphy of Cambay Basin, the name Chinchini Formation has been adopted by Zutshi et al. (1993) (Source: Pandey and Dave, 1998)

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


Lithology and Thickness

Claystone. The formation consists of greenish-grey to bluish grey sticky clays and claystone with frequent intercalations of shell debris. In the basal part, shales with limestone intercalations occur. In Ratanagiri area in the south and more western part of shelf margin depression (SM-1 structure), a massive bioclastic limestone unit occurs within the Chinchini Formation. The thickness of the formation is 1688 m in type section. It shows gradual increase in thickness from east to west within the basin. Clay/Claystone that provides a seal for the reservoirs of the Offshore region.

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


Lithology Pattern: 
Claystone


Relationships and Distribution

Lower contact

The formation disconformably overlies Bandra Fm, Ratnagiri Fm and Tapti Fm in different parts of the Bombay offshore Basin.

Upper contact

The sediment water interface / sea bed.

Regional extent

Entire Mumbai offshore region


GeoJSON

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Fossils

A very rich assemblage of foraminifera including Globigerinoides fistulosus, Globigerina nepenthes, Neogloboquadrina acostaensis, N. hummerosa, Dentoglobigerina actispira and Sphaeroidinella dehiscens have been recorded.


Age 

Pliocene to Recent. It may extend down to Late Miocene; a hiatus of 6 Myr equivalent to Late Miocene was inferred in some wells.

Age Span: 

    Beginning stage: 
Zanclean

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
5.34

    Ending stage: 
Holocene

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
0.00

Depositional setting

A shallow-marine environment varying from inner neritic to outer neritic has been inferred for the formation.


Depositional pattern:  


Additional Information


Compiler:  

D.S.N Raju