Deepwater fold-and-thrust belt along New Caledonia's western margin: relation to post-obduction vertical motions
|Author(s)||Collot Julien1, Patriat Martin1, 2, Etienne S.1, 3, Rouillard P.1, 3, 4, Soetaert F.1, 2, Juan C.1, Marcaillou B.5, Palazzin G.6, Clerc C.7, Maurizot P.1, Pattier F1, 3, Tournadour E.1, 3, Sevin B.1, Privat A.1|
|Affiliation(s)||1 : DIMENC, Serv Geol Nouvelle Caledonie, Noumea, New Caledonia.
2 : IFREMER, Noumea, New Caledonia.
3 : ZoNeCo Res Program, ADECAL Technopole, Noumea, New Caledonia.
4 : Novas Oil & Gas Consulting Ltd, Slough, Berks, England.
5 : CNRS, Geoazur, IRD, UNSA,OCA,UMR 7329, Noumea, New Caledonia.
6 : Univ Orleans, ISTO, Orleans, France.
7 : Univ Nouvelle Caledonie, LIVE, Noumea, New Caledonia.
|Source||Tectonics (0278-7407) (Amer Geophysical Union), 2017-10 , Vol. 36 , N. 10 , P. 2108-2122|
|WOS© Times Cited||4|
|Keyword(s)||deepwater fold-and-thrust belt, obduction, isostasy|
Classically, deepwater fold-and-thrust belts are classified in two main types, depending if they result from near- or far-field stresses and the understanding of their driving and triggering mechanism is poorly known. We present a geophysical dataset off the western margin of New Caledonia (SW Pacific) that reveals deformed structures of a deepwater fold-and-thrust belt that we interpret as a near-field gravity-driven system, which is not located at a rifted passive margin. The main factor triggering deformation is inferred to be oversteepening of the margin slope by post-obduction isostatic rebound. Onshore erosion of abnormally-dense obducted material, combined with sediment loading in the adjacent basin, has induced vertical motions that have caused oversteepening of the margin. Detailed morpho-bathymetric, seismic stratigraphic and structural analysis reveals that the fold-and-thrust belt extends 200 km along the margin, and 50 km into the New Caledonia Trough. Deformation is rooted at depths greater than 5 km beneath the seafloor, affects an area of 3500 km2, and involves a sediment volume of approximately 13 000 km3. This deformed belt is organized into an imbricate fan system of faults, and one out-of-sequence thrust fault affects the seabed. The thrust faults are deeply rooted in the basin along a low-angle floor thrust and connected to New Caledonia Island along a major detachment. This study not only provides a better knowledge of the New Caledonia margin, but also provides new insight into the mechanisms that trigger deepwater fold-and-thrust belts.