MACROFORAMINIFERAL BIOSTRATIGRAPHY AND PALEOBIOGEOGRAPHY OF THE UITOÉ LIMESTONE (EOCENE; BARTONIAN) OF NEW CALEDONIA, SOUTH PACIFIC

The Eocene age Uitoé Limestone of western New Caledonia represents a shallow water carbonate platform deposited in a tectonically active setting. The Uitoé was sampled in a 26.5 m thick section along the north shore of Baie de Saint-Vincent near the town of Boulouparis. The Uitoé Limestone overlies the Triassic flysch in angular unconformity and is overlain by an olistostromal chert breccia of possible Late Eocene age.

Large benthic foraminifera are the most abundant component of the Uitoé Limestone with red algae and bryozoans colonies also being major constituents. Minor groups include pelecypods, scleractinian corals, sponges, green algae and planktonic foraminifera. The larger foraminifera assemblage includes Assilina, Pellatispira, Discocyclina, and Operculina among others. The joint occurrence of Assilina and Pellatispira in the Uitoé Limestone indicate correlation with late middle Eocene Shallow Benthic Zone SBZ 17 (early Bartonian; 40-38.5 Ma). Additionally, the presence of Assilina and Pellatispira suggests an association with the Assilina-Pellatispira-Biplanispira (APB) fauna. The APB fauna is a low latitude Eocene fauna of the Tethyan realm and is typically found on the Sundaland craton and on the Pacific Plate. The absence of Biplanispira from this assemblage in New Caledonia may be a paleobiogeographic effect with Biplanispira typically associated only with the Sundaland craton. The presence of Operculina in the Uitoé Limestone may indicate a link with the Lacazinella fauna of the Australian craton.

The presence of the Tethyan APB fauna in the Uitoé Limestone of New Caledonia delimits the eastward extension of the Australian larger foraminiferal province. Further, the biostratigraphic age (SBZ 17) indicated by the larger foraminifera in the Uitoé Limestone shows that tectonic activity in New Caledonia was extant until at least the late middle Eocene (Bartonian). Two additional localities of the Uitoé facies containing large foraminifera (Cimetière Neo-Zélandais and Col Aymes) were identified in recent geologic mapping in New Caledonia. Detailed study of these two localities will refine the biostratigraphic age of the Uitoé and extend an understanding of the distribution of the APB fauna.