Tertiary Biostratigraphy of a Part of North-Western Kutch

The marine Tertiary strata around Lakhpat, north-western Kutch, range approximately from the Lutetian to the Burdigalian. Essential details are brought out in the lithic characters of these strata, mostly limestones, and the distribution of fossils in them. A number of breaks can be identified in the sequence, including the Eocene-Oligocene and the Oligocene-Miocene unconformities. Seven faunal zones have been recognised in this stratigraphic column, mainly with the help of the following larger Foraminifera: Alveolina elliptica (Sowerby), Asterocyclina alticostata (Nuttall), Dictyoconoides cooki (Carter), Discocyclina (Discocyclina) dispansa (Sowerby), D. (D.) sowerbyi Nuttall, Lepidocyclina (Eulepidina) sp., Miogypsina (Miogypsina) irregularis (Michelotti), Nummulites acutus (Sowerby), N. beaumonti d'Archiac and Haime, N. exponens (Sowerby), N. fichteli Michelotti, N. bagelensis Verbeek, N. perforatus (de Montfort), and "Operculina" sp. A striking vertico-lateral biofacies variation exists in the local zone 2, between strata rich in Nummulites exponens and those rich in species of Discocyclina (Discocyclina). Most of these larger Foraminifera are of considerable significance in the Indo-Pacific lower/middle Tertiary correlation. Certain aspects of this inter-regional stratigraphic correlation are discussed.