Abstract

On Katafanga, Vanua Vatu, and Avea, three small islands in the Lau group of Eastern Fiji, occur highly calcareous Neogene sediments in which the most abundant organic remains are Globigerinidae (about 20 per cent by volume). Less abundant are calcareous red algae (0—2.0 per cent), calcareous blue-green algae (0—5.5 per cent), benthonic Foraminifera (0—4.0 per cent), coral fragments (0—22.0 per cent), echinoid spines (1.0—2.0 per cent), and brachiopods and mollusks (0—6.0 per cent).

An origin in water considerably shallower than that of most Globigerina deposits is indicated by both physical and biological evidence. Diagnostic features are: fragmental oölites; interbedding of thin oölitic layers containing few Globigerinidae with beds rich in Globigerinidae; abundant calcareous mud; and high calcium carbonate content and absence of volcanic material generally present in deep-sea oozes. Biological characters of significance are the presence of fragments of reef corals, blue-green algae, and Crustacea.

The above features and other evidence suggest a depth of more than 40 fathoms—the limit of flourishing reef-coral growth—but a depth not greatly in excess of this figure. Apparently the pelagic shells were brought by surface currents to an area where there was little clastic deposition and a paucity of benthonic forms. Some limestones contain a high percentage of lithified calcareous mud which appears to be similar to muds now accumulating on submarine banks and in certain coral lagoons. It is suggested that the presence of this material inhibited benthonic growth.

The Fiji sediments are compared with deep-sea ooze; the supposed deep-water Globigerina limestones of Barbados, the Solomon Islands, South America; deposits on submarine banks and in the lagoons of existing atolls; shallow-water Globigerina chalk of England; Globigerina “soapstone” of Vitilevu, Fiji; and foraminiferal dune limestone of the Arabian Sea.

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