The d'Entrecasteaux (French pronunciation:[dɑ̃tʁəkasto]) Ridge (DER) is a double oceanic ridge in the south-west Pacific Ocean, north of New Caledonia and west of Vanuatu Islands. It forms the northern extension of the New Caledonia–Loyalty Islandsarc, and is now actively subducting in the Vanuatu subduction zone under the Vanuatu/New Hebrides arc.[1] The subduction of the DER is responsible for the anomalous morphology of the central part of New Hebrides arc whose movement more closely matches the north-east direction of the subducting Australian Plate (the rest of the New Hebrides arc rotate west in front of the southward expanding North Fiji Basin).[2]
DER
The d'Entrecasteaux Ridge connects the New Caledonia Ridge to the Vanuatu Trench
Approximate surface projection on Pacific Ocean of D'Entrecasteaux Ridge (DER) shaded in brown. Both the North d'Entrecasteaux Ridge and the South d'Entrecasteaux Chain are shown.
The name honours French naval officer Antoine Bruni d'Entrecasteaux, explorer of the south-west Pacific in the late 18th century.
The DER extends north from the New Caledonia ridge to the New Hebrides/Vanuatu Trench and thus separates the North Loyalty Basin (4,500–5,000 m (14,800–16,400 ft) bsl) to the south from the West Santos Basin (5,400 m (17,700 ft) bsl) to the north. The DER has a western and an eastern part with distinct morphologies: the arcuate western part is an elongated graben flanked by two near-parallel horsts; the eastern part widens to the east where it has been described to split into a southern and northern ridge.[3] These are separated by the Central d'Entrecasteaux Basin [4] This has a smooth surface covered by sediments, which is deepening eastward to 4,000 m (13,000 ft) west of Santo Island.[1]
The southern ridge is composed of 40 to 36 Ma-old extinct stratovolcanoes.[5][6] Some have called it therefore the South d'Entrecasteaux Chain.[7] It was considered to be a prolongation of the Loyalty Ridge by many, but this is questioned by reason of a 200 km (120 mi) gap between the westernmost South d'Entrecasteaux Chain seamount and the northernmost seamount in the Loyalty Ridge and the divergence in magnetic anomaly azimuths.[8] It is a seamount chain on-top of a broad east–west-trending ridge. The seamounts, including the Sabine Bank which reaches 7 m (23 ft) bsl, are the volcanic remnants of an old island arc. A 4,000 m (13,000 ft)-deep scarp separates the southern ridge from the North Loyalty Basin to the south.[1] The Bougainville Guyot, south of Santos, forms the eastern continuation of the seamount chain and is a Middle Mioceneandesitic volcano, aged 40 ± 2 Ma,[9] covered by Oligocene to Miocene lagoonal limestone.[10]
The northern ridge, also known as the North d'Entrecasteaux Ridge,[7] is a more continuous ridge, mostly more similar in composition to the Mariana fore-arc, forms part of an abandoned, north-facing oceanic trench which has been subducting under the New Hebridesisland arc during the last 2–3 Ma.[6] The northern DER reaches 2,350–2,100 m (7,710–6,890 ft) bsl.[1] Its eastern part has had its basalts reinterpreted by modern compositional reanalysis as Eocene basalts that are primitive arc tholeiites between 21 and 38 Ma in age.[11] Accordingly the eastern part of the DER is an abandoned plate boundary which was part of a south-dipping subduction zone before the Miocene.
A single dredged sample closest to the New Caledonia Nappe, as yet obtained, where the western part starts a curve that transitions to the eastern part, is of E-MORB back-arc basin-type composition and has an age of 49 ± 10 Ma.[11] This western part of the DER, has an average depth of 3,500 m (11,500 ft), and is bounded to the north by a scarp. The western platform has experienced an Eocene compressional phase followed by Middle Miocene to Quaternary uplift and tilt,[1] and indeed the next dredged sample to the north east has a poorly constrained age that is greater than 21 Ma and of primitive arc tholeiite composition consistent with subduction related formation.[11]
^Pelletier, Calmant & Pillet 1998, The central North Fiji basin and New Hebrides arc, and the D'Entrecasteaux ridge and West Torres plateau, pp. 272–273
^Collot & Fisher 1992, The d'Entrecasteaux Zone and Surrounding Ocean Basins, pp. 22, 23
Collot, J. Y.; Daniel, J.; Burne, R. V. (1985). "Recent tectonics associated with the subduction/collision of the D'Entrecasteaux zone in the central New Hebrides" (PDF). Tectonophysics. 112 (1): 325–356. Bibcode:1985Tectp.112..325C. doi:10.1016/0040-1951(85)90185-4. Retrieved 7 January 2017.
Collot, J. Y.; Fisher, M. A. (1992). "The d'Entrecasteaux Zone-New Hebrides island arc collision zone: an overview" (PDF). Proceedings of the Ocean Drilling Program, Initial Reports. 134: 19–31. Retrieved 7 January 2017.
Meffre, S.; Crawford, A. J. (2001). "Collision tectonics in the New Hebrides arc (Vanuatu)". Island Arc. 10 (1): 33–50. doi:10.1046/j.1440-1738.2001.00292.x. Retrieved 7 January 2017.
Pelletier, B.; Calmant, S.; Pillet, R. (1998). "Current tectonics of the Tonga–New Hebrides region". Earth and Planetary Science Letters. 164 (1): 263–276. Bibcode:1998E&PSL.164..263P. doi:10.1016/S0012-821X(98)00212-X. Retrieved 7 January 2017.
Greene, HG; Collot, JY; Pelletier, B; Lallemand, S (1992). "4. Observation of forearc seafloor deformation along the North d'Entrecasteaux Ridge - New Hebrides island arc collision zone from Nautile submersible" (PDF). Proceedings of the Ocean Drilling Program, Initial Reports. 134.
Mortimer, N; Gans, PB; Palin, JM; Herzer, RH; Pelletier, B; Monzier, M (2014). "Eocene and Oligocene basins and ridges of the Coral Sea‐New Caledonia region: Tectonic link between Melanesia, Fiji, and Zealandia". Tectonics. 33 (7): 1386–407. doi:10.1002/2014TC003598.
entrecasteaux, ridge, entrecasteaux, french, pronunciation, tʁəkasto, ridge, double, oceanic, ridge, south, west, pacific, ocean, north, caledonia, west, vanuatu, islands, forms, northern, extension, caledonia, loyalty, islands, actively, subducting, vanuatu, . The d Entrecasteaux French pronunciation dɑ tʁekasto Ridge DER is a double oceanic ridge in the south west Pacific Ocean north of New Caledonia and west of Vanuatu Islands It forms the northern extension of the New Caledonia Loyalty Islands arc and is now actively subducting in the Vanuatu subduction zone under the Vanuatu New Hebrides arc 1 The subduction of the DER is responsible for the anomalous morphology of the central part of New Hebrides arc whose movement more closely matches the north east direction of the subducting Australian Plate the rest of the New Hebrides arc rotate west in front of the southward expanding North Fiji Basin 2 DER The d Entrecasteaux Ridge connects the New Caledonia Ridge to the Vanuatu Trench Approximate surface projection on Pacific Ocean of D Entrecasteaux Ridge DER shaded in brown Both the North d Entrecasteaux Ridge and the South d Entrecasteaux Chain are shown The name honours French naval officer Antoine Bruni d Entrecasteaux explorer of the south west Pacific in the late 18th century Contents 1 Geological setting 2 References 2 1 Notes 2 2 SourcesGeological setting editThe DER extends north from the New Caledonia ridge to the New Hebrides Vanuatu Trench and thus separates the North Loyalty Basin 4 500 5 000 m 14 800 16 400 ft bsl to the south from the West Santos Basin 5 400 m 17 700 ft bsl to the north The DER has a western and an eastern part with distinct morphologies the arcuate western part is an elongated graben flanked by two near parallel horsts the eastern part widens to the east where it has been described to split into a southern and northern ridge 3 These are separated by the Central d Entrecasteaux Basin 4 This has a smooth surface covered by sediments which is deepening eastward to 4 000 m 13 000 ft west of Santo Island 1 The southern ridge is composed of 40 to 36 Ma old extinct stratovolcanoes 5 6 Some have called it therefore the South d Entrecasteaux Chain 7 It was considered to be a prolongation of the Loyalty Ridge by many but this is questioned by reason of a 200 km 120 mi gap between the westernmost South d Entrecasteaux Chain seamount and the northernmost seamount in the Loyalty Ridge and the divergence in magnetic anomaly azimuths 8 It is a seamount chain on top of a broad east west trending ridge The seamounts including the Sabine Bank which reaches 7 m 23 ft bsl are the volcanic remnants of an old island arc A 4 000 m 13 000 ft deep scarp separates the southern ridge from the North Loyalty Basin to the south 1 The Bougainville Guyot south of Santos forms the eastern continuation of the seamount chain and is a Middle Miocene andesitic volcano aged 40 2 Ma 9 covered by Oligocene to Miocene lagoonal limestone 10 The northern ridge also known as the North d Entrecasteaux Ridge 7 is a more continuous ridge mostly more similar in composition to the Mariana fore arc forms part of an abandoned north facing oceanic trench which has been subducting under the New Hebrides island arc during the last 2 3 Ma 6 The northern DER reaches 2 350 2 100 m 7 710 6 890 ft bsl 1 Its eastern part has had its basalts reinterpreted by modern compositional reanalysis as Eocene basalts that are primitive arc tholeiites between 21 and 38 Ma in age 11 Accordingly the eastern part of the DER is an abandoned plate boundary which was part of a south dipping subduction zone before the Miocene A single dredged sample closest to the New Caledonia Nappe as yet obtained where the western part starts a curve that transitions to the eastern part is of E MORB back arc basin type composition and has an age of 49 10 Ma 11 This western part of the DER has an average depth of 3 500 m 11 500 ft and is bounded to the north by a scarp The western platform has experienced an Eocene compressional phase followed by Middle Miocene to Quaternary uplift and tilt 1 and indeed the next dredged sample to the north east has a poorly constrained age that is greater than 21 Ma and of primitive arc tholeiite composition consistent with subduction related formation 11 References editNotes edit a b c d e Collot Daniel amp Burne 1985 The d Entrecasteaux Zone pp 5 7 Pelletier Calmant amp Pillet 1998 The central North Fiji basin and New Hebrides arc and the D Entrecasteaux ridge and West Torres plateau pp 272 273 Collot amp Fisher 1992 The d Entrecasteaux Zone and Surrounding Ocean Basins pp 22 23 Greene et al 1992 Figure 1 p44 Mortimer et al 2014 Figure 9 a b Meffre amp Crawford 2001 Tectonic setting pp 34 35 a b Greene et al 1992 Introduction p43 Mortimer et al 2014 Sections 2 3 D Entrecasteaux Ridge 8 2 Eocene Subduction Related Arcs Mortimer et al 2014 Abstract Collot amp Fisher 1992 Abstract a b c Mortimer et al 2014 Figure 2 7 3 North D Entrecasteaux Ridge Sources edit Collot J Y Daniel J Burne R V 1985 Recent tectonics associated with the subduction collision of the D Entrecasteaux zone in the central New Hebrides PDF Tectonophysics 112 1 325 356 Bibcode 1985Tectp 112 325C doi 10 1016 0040 1951 85 90185 4 Retrieved 7 January 2017 Collot J Y Fisher M A 1992 The d Entrecasteaux Zone New Hebrides island arc collision zone an overview PDF Proceedings of the Ocean Drilling Program Initial Reports 134 19 31 Retrieved 7 January 2017 Meffre S Crawford A J 2001 Collision tectonics in the New Hebrides arc Vanuatu Island Arc 10 1 33 50 doi 10 1046 j 1440 1738 2001 00292 x Retrieved 7 January 2017 Pelletier B Calmant S Pillet R 1998 Current tectonics of the Tonga New Hebrides region Earth and Planetary Science Letters 164 1 263 276 Bibcode 1998E amp PSL 164 263P doi 10 1016 S0012 821X 98 00212 X Retrieved 7 January 2017 Greene HG Collot JY Pelletier B Lallemand S 1992 4 Observation of forearc seafloor deformation along the North d Entrecasteaux Ridge New Hebrides island arc collision zone from Nautile submersible PDF Proceedings of the Ocean Drilling Program Initial Reports 134 Mortimer N Gans PB Palin JM Herzer RH Pelletier B Monzier M 2014 Eocene and Oligocene basins and ridges of the Coral Sea New Caledonia region Tectonic link between Melanesia Fiji and Zealandia Tectonics 33 7 1386 407 doi 10 1002 2014TC003598 16 S 165 E 16 S 165 E 16 165 Retrieved from https en wikipedia org w index php title D 27Entrecasteaux Ridge amp oldid 1184758378, wikipedia, wiki, book, books, library,
