Evolution and sedimentation in a forebulge environment: example of the late Eocene Uitoé Limestone, New Caledonia, Southwest Pacific

Abstract

New litho- and biostratigraphic data for the Uitoé Limestone on the southwest coast of New Caledonia constrain its age to the E13–E15 zone (late middle–late Eocene or late Bortonian–Runangan in the New Zealand nomenclature). From the base up, the limestone sequence records a shallowing trend with evidence of emergence followed abruptly by deep basinal turbidite, indicating rapid submersion. Comparison with the adjacent area to the northwest shows that the Uitoé Limestone is part of a diachronous carbonate ramp extending in age from middle to late Eocene. Moreover, a forebulge environment is confirmed for this unit which, at a larger scale, was deposited on the distal part of a foreland basin system that had been propagating southeastwards through New Caledonia since the Paleocene. The Uitoé Limestone and its thin turbidite cover represent the youngest sedimentary deposits in a forebulge environment prior to the collisional stage and obduction of the allochthonous units over New Caledonia.