EOCENE PLANKTONIC FORAMINIFERAL BIOSTRATIGRAPHY IN THE NOUMEA BASIN OF NEW CALEDONIA

Olistosromal blocks of pelagic limestone occur throughout the flysch sequence of the Noumea Basin in southern New Caledonia. These blocks contain planktonic foraminifera and have collectively been referred to as “Globigerina Limestones” by earlier workers. No definitive biostratigraphic correlations have been made but the “Globigerina Limestones” have generally been regarded as middle to late Eocene in age. A complete stratigraphic succession is not present in the Noumea Basin but in the northern part of New Caledonia, near Koumac, the “Globigerina limestones” overlie black pelagic chert of Paleocene age and underlie Eocene(?) age flysch. The Uitoe Limestone is a reef unit near Bouloupari and appears to stratigraphically overlie the “Globigerina Limestones’.

Planktonic foraminifera from the “Globigerina Limestones” were studied in 112 thin sections collected from the Noumea Basin. A diverse fauna was identified including Morozovella aragonensis, Morozovelloides crassatus, Morozovelloides lehneri, Guembelitrioides nuttalli, Acarinina bullbrooki, Globigerinatheka mexicana, and Globigerinatheka kugleri among others. This assemblage is consistent with a middle Eocene (Lutetian) age. Further, the joint occurrence of Acarinina bullbrooki, Morozovella aragonensis, and Globigerinatheka kugleri in numerous samples suggests a correlation with planktonic foraminiferal biozone E9 (Lutetian) for most of the blocks of the “Globigerina Limestones” in the Noumea Basin. Several of the studied samples may be as young as early Bartonian but biostratigraphic precision is limited.

The planktonic species present in the Uitoe Limestone are Dentoglobigerina yeguaensis, Zeauvigerina zealandica, Pseudohastigerina micra, Guembellitroides nuttali and Clavigerinella eocanica. These are long ranging species suggesting an age no older than biozone E7 and no younger than biozone E10.

The results indicate that the pelagic limestones in the Noumea Basin are similar in age to the foraminiferal oozes of DSDP site 206 in the New Caledonia Basin. Further work on the planktonic foraminifera of the “Globigerina Limestones” near Koumac and in the Noumea Basin will improve biostratigraphic precision and clarify this relationship.