Kalapani Fm
Type Locality and Naming
Names after the ‘Kalapani’ (black water) of the Andaman Islands. Type section is Well AN-42-1 (depth interval: 520m to 3972m).
[Original Publication: Pandey, J., Agarwal, R.P., Dave., A., Maithani, A., Trivedi, K.B., Srivatsava, A.K., and Singh, D.N. (1993) Lithostratigraphy of Petroliferous Basins, Document XI, Andaman Basin, KDMIPE, ONGC Publication, pp. 1-103.].
Hypostratotype: AN-1-1 (depth interval: 2600-3740m)
Lithology and Thickness
Flysch (Claystone and Sandstone). In the holostratotype (Well AN-42-1), the formation typically depicts flysch facies and consists of claystone, shale and sandstone. In the hypostratotype offshore well, the formation consists of light to dark grey, moderately hard, highly calcareous shale and light grey to white, sub angular to angular, slightly calcareous, fine to medium grained, poorly sorted sandstone.
In the type section, is has a thickness of 1140m. In the hypostratotype of AN-42-1, it has a thickness of 3452m. In well AN-1-1 (depth interval: 2600-3740m), it has a thickness of 1140m.
Relationships and Distribution
Lower contact
Unconformably overlies the basement of igneous rocks in AN-42-1.
Upper contact
In the reference AN-42-1 section; there is a pronounced unconformity on the top, where it is overlain by Neogene strata
Regional extent
[Figure 1: Detailed geological map of Andaman area (modified after Bandopadhyay 2012) showing locations mentioned in numbers in B. Ghosh et al., 2017, Geo.Soc.London.Memoirs, 47, 95-110)]
GeoJSON
Fossils
In the Oil India Wells AOE-1, AOE-2, the formation has yielded a rich suite of planktonic foraminifera of Late Cretaceous to Oligocene age. The diagnostic species include, Morozovella velascoensis, P. pseudomenardii, M. subbotinae, G. (Acarinina) soldadoensis angulosa, G. (A) pentacamerata, Asterocyclina sp., Globigerina ampliapertura, G. selli, G. gortanii, Lepidocyclina sp, Asterigerina sp., G. opima opima, Catapsydrax dissimilis, G.tripartita, G. prasaepis, G. sastrii, G. opima nana, G. angulisuturalis.
Age
Depositional setting
The presence of abundant reworked planktonic and smaller foraminifera suggest probable transportation of outer shelf sediments to bathyal environment by turbidity traction.
Additional Information