Post-obduction carbonate system development in New Caledonia (Népoui, Lower Miocene)

Deepwater Fold‐and‐Thrust Belt Along New Caledonia's Western Margin: Relation to Post‐obduction Vertical Motions

“…The 10° seaward dip of PONC‐1 along the western margin of New Caledonia is concordant with the general 10° dip toward the southwest of nearby postobduction sediments that crop out on the coast near Népoui (Coudray, ; Maurizot et al, ) (Figure ), and of dipping planation surfaces on allochthonous ophiolitic massifs (Chardon & Chevillotte, ; Chevillotte et al, ). Onshore, these dips are interpreted to be the result of postobduction epeirogenic uplift motions (Chardon & Chevillotte, ; Chevillotte et al, ).…”

“…We cannot rule out that the trigger was combined with other factors such as high sedimentation rates and/or seismicity related to postobduction isostatic rebound (e.g., postglacial seismicity in Fennoscandia, (Fjeldskaar et al, )), but the high values of oversteepening strongly suggest that it was the triggering mechanism. Known contemporaneous sedimentary records of the Miocene mixed carbonate siliciclastics series of Népoui (Maurizot et al, ) do not reveal particularly high sedimentation rates but indicate sediments were deposited in a shelf environment close to the coast. Moreover, they are Miocene in age and obduction is thought to have finished during latest Eocene (Cluzel, ).…”

“…In terms of relative age, the postobduction units (PONC‐1, PONC‐2, and PONC‐3) that fill the flexural basin above the RN reflector are interpreted to be Oligocene to present day (Collot et al, ). Onshore, the only coeval postobduction marine rocks crop out in the Népoui area and consist of early Miocene shallow‐water to outer shelf carbonate systems mixed with coarse detrital products that are primarily derived from erosion of the ophiolite (Coudray, ; Maurizot et al, ) and Quaternary reefs (Cabioch et al, ). Gravity core MD06‐3019 was recovered during voyage Zonéco‐12 (Foucher & Scientific Party, ) at 3520 m water depth in the center of the NCT (see location on Figure b), probably in the distal part of a submarine canyon or the deep‐sea fan (Foan, ).…”

“…The onshore domain is characterized by the presence of (i) the 10 km wide and 50 km long Kopeto‐Boulinda obducted ophiolite massif, which overlies obducted basalts of the Poya Terrane (Eissen et al, ), Gondwana‐related sedimentary basement, synobduction turbidites and Cretaceous rifted blocks and (ii) latest Eocene and Miocene sedimentary outcrops that are only found in the Népoui area between the shore and obducted massifs and respectively record the final stages of Eocene obduction and Miocene postobduction extensional tectonics (Coudray, ; Maurizot et al, ; Paris et al, ). Elements constituting the synobduction to postobduction marine sediments are essentially erosional products of the ophiolites mixed with bioclastic‐biogenic limestones.…”

Nickel-Bearing Laterite Deposits in Accretionary Context and the Case of New Caledonia: From the Large-Scale Structure of Earth to Our Everyday Appliances

“…The terrane was exposed to emergence, dismantling, weathering, and erosion during the Neogene post-obduction period. Early Miocene conglomerate of the Népoui area reworks abundant weathered products of the peridotite, including supergene nickel ore (Coudray, 1971;Maurizot et al, 2016). The oldest weathering profiles have been dated indirectly by paleomagnetism methods at 25 Ma (Sevin et al, 2012).…”