Pandanallur Fm
Type Locality and Naming
SUBSURFACE: The type section is located at exploratory well Pandanallur-A (depth interval: 690-250 m), in the Nagapattinam subbasin. The hypostratotype is in the well Bhuvanagiri-A (depth interval: 1355-700 m). It was named after the Pandanallur town by ONGC team steered by Venkatarengan et al., (1993) and issued as Document-VII by KDMIPE, ONGC, Dehradun (1993).
[Figure 1: Type-section Map of Subsurface Formations]
Lithology and Thickness
Clayey sandstone. This formation mainly consists of clayey sandstone interbedded with bands of claystone. Sandstone is light gray to dirty white, grains are fine to coarse, subangular to subrounded, moderate to poor sorting, feebly calcareous. Sand grains are transparent to translucent, silty with clayey matrix with traces of pyrite and carbonaceous matter. Claystone is dark gray to greenish gray, sticky, silty, feebly calcareous sandstone occurs at places. Pyrite, limestone, chert and chalk occur in traces. Its thickness varies from 440-1000+ m. Part of Nagora Gr.
[Figure 2: Generalized Stratigraphy and Petroleum System of Cauvery Basin (from dghindia.gov.in)]
[Figure 3: Generalized Stratigraphy of Cauvery Basin (Provided by A. Nallapa Reddy & R. Nagendra)]
Relationships and Distribution
Lower contact
Conformable with the Karaikal Fm.
Upper contact
Conformable with the Tiruppundi Fm / Niravi Fm / Madanam Fm and Cuddalore Fm.
Regional extent
This formation is confined to Bhuvanagiri area in the Ariyalur-Pondicherry subbasin.
GeoJSON
Fossils
Foraminifera-Globigerina angiporoides, Nummulites sp., Lepidocyclina sp.
Age
Depositional setting
Middle neritic.
Additional Information
This unit is distinguished from analogous Tiruppundi Fm, which is abundantly calcareous.