Alveolina from Western Kutch-Systematics, Distribution and Stratigraphic Significance

Alveolina of Kutch Middle Eocene limestones and marls is identified as A. elliptica var. nuttalli. The variety is shown to have a characteristic shape (expressed as a ratio of polar and equatorial diameters), and more or less fixed number of flosculinised whorls; the variation in the development of non-flosculinised whor1s on the flosculinised ones is attributed to an ontogenetic development correlated with size increase. The variety shows a clear case of lateral facies variation, occurring in two 'apparent' horizons in deeper parts of the basin with vertical absence in between, but continuing throughout the rock unit in marginal shallower parts. The facies-governed nature of this larger benthic foraminiferal species and its presence in the Kutch Paleogene sequence without the earlier glomalveoline forms are considered important aspects in stratigraphic studies.