New Caledonia Obducted Peridotite Nappe: Offshore Extent and Implications for Obduction and Postobduction Processes

• Published in: Tectonics (Washington, D.C.) D.C.), 2018-04, Vol.37 (4), p.1077-1096
• Main Authors: Patriat, Martin, Collot, Julien, Etienne, Samuel, Poli, Sara, Clerc, Camille, Mortimer, Nick, Pattier, France, Juan, Caroline, Roest, Walter R.
• Format: Article
• Language: English
• Subjects: Continental margins; Eocene; Fault lines; Geological time; Magma; Nappes; New Caledonia; Obduction; Offshore; ophiolite; Ophiolites; Peridotite; Seismic data; Seismological data; SW Pacific; Tectonics; Uplift; Zealandia
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1002/2017TC004722

One of the largest ophiolitic peridotite masses in the world covers a quarter of the island of Grande Terre, New Caledonia. The Peridotite Nappe was obducted during the Eocene, is weakly deformed, and corresponds to the highest of a structurally simple pile of thrust nappes. We present new marine seismic data that allow us to track the offshore continuation of the Peridotite Nappe along strike for a distance of more than 500 km south of New Caledonia and to image its preobduction, synobduction, and postobduction sedimentary records. Offshore, the Peridotite Nappe underlies a ~150 km wide and 2 km deep basin. Flat‐topped horsts of peridotite are clearly bounded by major normal faults; in contrast, faults are obscure onland. To the east, the Peridotite Nappe roots along the eastern margin of the Félicité Ridge (new name), a ~300 × 25 km dome‐shaped ridge, which we interpret as being the southern extension of the high‐pressure/low‐temperature metamorphic core complex observed in New Caledonia. Two alternative tectonic models address the relative timing and relationships between Peridotite Nappe emplacement, uplift of a metamorphic core complex, and extensional tectonics. These models provide new ideas for the understanding the formation of the eastern margin of the Zealandia continent. Our results contribute to an understanding of how oceanic mantle is emplaced onto continental margins. Key Points The New Caledonia Peridotite Nappe is confidently identified in offshore seismic lines over a 50,000 km2 area Offshore, the Peridotite Nappe is clearly cut by postobduction, deeply rooted normal faults Speculatively, the continuation of the HP/LT Mt. Panie metamorphic complex lies east of the Peridotite Nappe, along the dome‐shaped Félicité Ridge