Coralline algae from the Aramda Reef Member of the Chaya Formation, Mithapur, Gujarat

The Quaternary sediments of the Aramda Reef Member of the Chaya Formation exposed in the Mojap coast near Mithapur, Gujarat are characterized by well-developed coralline algal build-ups. These algal build-ups are exceptionally rich in coralline algae and corals. In the present paper, thirteen species belonging to eight genera of coralline algae are described. Out of these, seven species (Titanoderma nataliae, Lithophyllum nitorum, Lithophyllum quadratum, Spongites sp. Brandano et al., 2005, Sporolithon lvovicum, Mesophyllum fructiferum and Lithothamnion praefruticulosum) are the new records for India. Four species (Titanoderma pustulatum, Sporolithon intermedium, Mesophyllum commune and Phymatolithon sp.) are first time recorded from the study area. Among the major framework builders of coralline algae of the Aramda Reef Member are Lithophyllum, Titanoderma, Sporolithon, Mesophyllum and Lithothamnion. Two associations of the coralline algal assemblages can be distinguished: one indicating shallow water, high-energy conditions is developed in the upper part, while the other suggesting deposition in low-energy conditions is characteristic of the lower part of the succession. These algal associations, together with their growth-forms (encrusting, warty to fruticose, layered) come from stratigraphically separate beds. They indicate that the temperature, depth and hydrodynamic energy conditions also fluctuated during deposition of the Aramda Reef Member. It is concluded that the lower Hapalidiaceae-Sporolithaceae association dominated during warmer interval, whereas the upper lithophylloids association flourished in relatively low-temperature conditions. The associated corals indicate that minimum winter sea surface temperature remained above 18°-20° C.