Abstract The post-obduction formations of Grande Terre, New Caledonia, comprise igneous intrusions, regolith cover, and marine and terrestrial sedimentary rocks. Two restricted Late Oligocene granitoid bodies are intruded into the Peridotite Nappe and its substrate in the south of the island. Thick regolith cover developed over the Peridotite Nappe from the Late Oligocene or earlier. The Népoui Group comprises Late Oligocene–Early Miocene mixed marine carbonate and siliciclastic deposits. It mainly reworks the Peridotite Nappe and its regolith cover. Its development pattern is mainly controlled by tectonic uplift and subsidence. The Gwa N'Doro Formation on the eastern coast and the Fluvio-lacustrine Formation in the south are remnants of the Miocene–Present river network. Offshore, thick Oligocene to Neogene sedimentary successions are imaged by seismic surveys on the margins of Grande Terre, although these successions have not been drilled and remain undated. Several dredges have recovered shallow Miocene sedimentary rocks, indicating substantial Neogene subsidence. Quaternary formations are represented inland by aeolianite, vertisols and calcrete and offshore by the large barrier reef–lagoon complex, the onset of which is dated at c. 400 ka. This chapter discusses the different models proposed for the post-obduction evolution of Grand Terre.

Abstract In New Caledonia, the cover refers to the autochthonous Late Cretaceous to Paleogene sedimentary and volcanic formations unconformably overlying the basement rocks and underlying the allochthonous nappes. The first period of deposition, broadly from the Late Cretaceous to Paleocene ( c. 105–56 Ma) was controlled by extension and rifting. The second period, broadly the Eocene ( c. 56–34 Ma), was dominated by convergence and contraction. The Late Cretaceous part of the cover consists of synrift conglomerates and coal-bearing deposits with interlayered bimodal, subduction-related and intra-plate volcanic rocks. The post-rift deposits are deep water sedimentary rocks deposited under anoxic conditions with reduced terrigenous input. The Paleocene to Eocene formations, mainly carbonates, attest to profound palaeogeographical changes and a switch to a different geodynamic regime, linked to the onset of Eocene convergence. The Middle to Late Eocene formations are typically composed of turbidites and breccias. They were deposited in a typical flexural foreland basin context as an upwards-coarsening sequence topped by an olistostrome. They are associated with tectonic convergence and east-dipping subduction that led to the end-Eocene obduction of ophiolitic nappes. This two-fold evolution, extension then compression, can be integrated in the wider framework of the plate tectonic evolution of the SW Pacific.

Abstract New Caledonia is known as a global biodiversity hotspot. Like most Pacific islands, its modern biota is characterized by high levels of endemism and is notably lacking in some functional groups of biota. This is the result of its distinctive palaeobiogeographical history, which can be described in terms of three major episodes relating to Gondwana, Zealandia and New Caledonia. The geological record, the fossil record and the modern biota of the archipelago are all reviewed here. The geological record shows that the main island, Grande Terre, was submerged between 75 and 60 Ma. There is a 9 myr interval without any geological record between 34 and 25 Ma, immediately after the obduction of the Peridotite Nappe. Grande Terre may or may not have been submerged during this 9 myr interval. The ages given by molecular biology, independent of any geological calibration points, form a continuous spectrum from 60 Ma up to the present day. The derived lineage ages from molecular phylogenies all post-date 60 Ma, supporting the idea of the continuous availability of terrestrial environments since 60 Ma. Of the three common scenarios for the origin of the New Caledonia biota, long-distance dispersal is the most plausible, rather than vicariance or dispersal over short distances.

Abstract The record of two Neoproterozoic glaciations in South Australia has been known for about a century. The earlier glaciation, of Sturtian age, is represented by the Yudnamutana Subgroup and is characterized by widespread diamictites with both intrabasinal and extrabasinal clasts, some locally faceted and striated. Associated facies include shallow-water sandstone, bedded and laminated siltstone with lonestones and dropstones, and sedimentary ironstones (mainly ferruginous siltstone and diamictite). Proximal settings adjacent to the Curnamona Province display massive basement-derived conglomerate and gigantic basement megaclasts (up to hundreds of metres across). Sturtian glaciogenic sediments of the Yudnamutana Subgroup unconformably overlie a variety of older rock units, including crystalline basement near basin margins and uppermost Burra Group sediments in the depocentre, and were deposited both in shallow marine shelf environments and in tectonically active rift basins encircling the Curnamona Province, with corresponding increases in total thickness from 100–300 m to more than 5 km. Recent U–Pb zircon SHRIMP dating of a thin volcaniclastic layer indicates that the waning stages of the Sturtian glaciation occurred at c. 660 Ma. Unlike the deposits of the younger Elatina glaciation, the Yudnamutana Subgroup has so far not yielded reliable palaeomagnetic data.

Abstract Cryogenian correlation in Australia is based on an extensive data set from the Centralian Superbasin and Adelaide Rift Complex and integrates biostratigraphy and isotope chemostratigraphy to provide a three-dimensional interpretation based on outcrop and drill holes. Studies are ongoing, but newer data are consistent with the distributions discussed here. From the chemostratigraphic and biostratigraphic viewpoint, the first appearance of the acritarch Cerebrosphaera buickii , coupled with a large negative isotope excursion at c. 800 Ma, supported by the first appearance of the stromatolite Baicalia burra , seems to have potential for boundary placement. It is widely recognized across Australia and seems to have potential globally.

Abstract The Loyalty Ridge lies to the east and NE of the Norfolk Ridge. The three main Loyalty Islands (Maré, Lifou and Ouvéa) emerge from the ridge at the same latitude as Grande Terre. The islands are uniformly composed of carbonate deposits, except for Maré, where Middle Miocene intra-plate basalts and associated volcaniclastic rocks form restricted outcrops. Miocene rhodolith limestones constitute the bulk of the carbonate cover of the three islands. On Maré, these platform accumulations are locally topped by a dolomitic hardground, which, in turn, is covered by Pliocene–Pleistocene coral-bearing formations. These coral reef constructions are preserved as elevated rims over all three islands and define an atoll stage in their development. The Pleistocene–Holocene palaeoshoreline indicators include fringing bioconstructions and marine notches and record both eustatic sea-level changes and tectonic deformation. The ridge has been in the forebulge region in front of the active Vanuatu subduction zone since the Pliocene and each of the three islands has been uplifted and tilted to varying degrees. Offshore, the Loyalty Ridge continues northwards to the d'Entrecasteaux Zone and southwards to the Three Kings Ridge. Although typically volcanic, the nature of the deep Loyalty Ridge remains unknown.

Abstract The main metallic mineral resources of New Caledonia are hosted by the obducted Peridotite Nappe. Ni, Co, Cr and the Pt group elements (PGEs) are specific to this ultramafic terrane. Cr, as podiform chromitite in the uppermost mantle, is the only hypogene metal mined economically in the past. The largest chromitite deposits are located in the lherzolitic Tiébaghi Massif. Supergene Ni and Co deposits are concentrated by the tropical climate that has prevailed since the Miocene. New Caledonian lateritic Ni deposits account for 10% of the global Ni resources. Hydrous Mg silicate and oxide types coexist in a single deposit. A local genetic model based on geomorphological evolution is proposed. Sc is a prospective resource associated with these supergene deposits. The PGEs are a prospective resource associated with chromite, with potential in the hypogene, supergene and fluvio-littoral domains. Pt and Pd are the most significant elements. The transition zone between the upper mantle and crustal cumulates constitutes a regional Pt–Pd-enriched horizon. The concentrations are related to small disseminated chromite lenses in a pyroxene-rich lithology. The PGEs are concentrated in weathering profiles. The value of chromite-rich sands as placers or sand beach deposits might be enhanced by the occurrences of PGEs.

Abstract The mineral resources of the non-ultramafic rocks of New Caledonia and its Exclusive Economic Zone can be classified according to their host rocks. The metallic mineral resources are essentially associated with volcanic and magmatic activity. Non-economic volcanogenic massive sulfide deposits with Cu and Au are located in the Late Carboniferous Koh Ophiolite and in the Late Cretaceous Poya Terrane. Base metals, Au and Ag of the sedimentary–exhalative type are present in the metamorphic Diahot-Panié Metamorphic Complex, associated with syn-rift volcanism. An Au–Sb metallogenic province is associated with the post-obduction Late Oligocene granitoids and co-genetic hydrothermal silica–carbonate (listwanite) zones in the Peridotite Nappe; Au is disseminated in the granites and Sb occurs as lodes in the silica–carbonate. Among the non-metallic mineral resources, barite, gypsum, magnesite, phosphate, clays, dimension stones, limestone for use as cement and as a neutralizer, and aggregates are all present. Gemstones such as jade and chrysoprase are only used locally. Late Cretaceous coal, which was briefly exploited in the past, is now considered to be a source rock for an offshore potential oil and gas system. Petroleum prospectivity is currently focused on the Fairway Basin. Several low-enthalpy thermo-mineral springs with a weak geothermal energy potential are known on Grande Terre.

Abstract Convergence and subduction started in the Late Paleocene, to the east of New Caledonia in the South Loyalty Basin/Loyalty Basin, leading to the formation of the Subduction–Obduction Complex of Grande Terre. Convergence during the Eocene consumed the oceanic South Loyalty Basin and the northeasternmost margin of Zealandia (the Norfolk Ridge). The attempted subduction of the Norfolk Ridge eventually led to the end-Eocene obduction. Intra-oceanic subduction started in the South Loyalty Basin, as indicated by high-temperature amphibolite (56 Ma), boninite and adakite series dykes (55–50 Ma) and changes in the sedimentation regime (55 Ma). The South Loyalty Basin and its margin were dragged to a maximum depth of 70 km, forming the high-pressure–low-temperature Pouébo Terrane and the Diahot–Panié Metamorphic Complex, before being exhumed at 38–34 Ma. The obduction complex was formed by the stacking from NE to SW of several allochthonous units over autochthonous Zealandia, including the Montagnes Blanches Nappe (Norfolk Ridge crust), the Poya Terrane (the crust of the South Loyalty Basin) and the Peridotite Nappe (the mantle lithosphere of the Loyalty Basin). A model of continental subduction accepted by most researchers is proposed and discussed. Offshore continuations and comparable units in Papua New Guinea and New Zealand are presented.