Coralline-algal framework in the quaternary of prainha (Santa Maria island, Azores)

Abstract

© Instituto Geológico y Minero de España.At the south coast of the island of Santa Maria (Azores, Portugal) a coralline-algal framework emerges near the base of a Quaternary succession. It is located about 2 m above the present mean sea level, extends for near 200 m along the littoral zone, and has a maximum thickness of 60 cm. The main framework builders are coralline red algae (Corallinaceae, Rhodophyta). Mollusc shells, vermetid tubes and bryozoans are the secondary framework builders. The coralline assemblage is composed of Spongites fruticulosus, with some Neogoniolithon brassica-florida, Lithophyllum incrustans and Titanoderma pustulatum. The morphological network and taxonomic composition show close analogies with the coralline algal assemblages of the Mediterranean and west Atlantic, formed at sea level in narrow tide amplitudes and moderate hydrodynamics