Emerald fracture zone

Map of the Emerald fracture zone as red shading to south and relationship to its north to the approximate line of the Macquarie Ridge (yellow) which is the Australian and Pacific plate boundary. Clicking on map enables mouse over, which shows a purple dot as the location of the Macquarie triple junction.

The Emerald fracture zone (62°S 170°E) is an undersea fracture zone running the distance from the southwest corner of the Campbell Plateau to the northern tip of Iselin Bank. The name was proposed by Dr. Steven C. Cande of the Scripps Institution of Oceanography for the vessel Emerald, which traversed this region in 1821, and was approved by the Advisory Committee for Undersea Features in June 1997.[1] The Emerald Basin to its north west was named from the same source.[2] Some[2] have restricted the name to the southern east west orientated transform fault zone but the north south orientated faults that define the eastern boundary of the Emerald Basin are generally included in the literature.[3]

Geology

The latest reinterpretation of the ocean floor geology of the region based on magnetic data assigns the area of the fault zone to oceanic crust of Eocene to Miocene age and so would distinguish other north south fault zones in the Cretaceous oceanic crust to the south east of the Campbell Plateau.[4] The fracture zone is related to the Hjort Trench that represents the southern end of the Australian Plate and Pacific Plate convergence, contains the Macquarie Triple Junction at its south western margin and mainly acts as a leaky transform fault zone between the Antarctic Plate and Pacific Plate.[3] It has only moderate current seismic activity.[5] An example was the M_ww5.9 event of 9 June 2023.[6]

Tectonics

The clockwise rotation of the Pacific Plate and Antarctic Plate between 12 and 10 million years ago resulted in fragmentation of the long-offset Emerald transform fault and its replacement over less than 2 million years with closely spaced, highly variable transform offsets that were joined by short ridge segments.[7] There was asymmetrical spreading rates in the area of the leaky transform fault zone near the Macquarie Triple Junction.[7]

See also

• Macquarie fault zone
• Macquarie triple junction

References

1. "Emerald Fracture Zone". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. Retrieved 1 March 2012.
2. NOAA gazetteer:Emerald
3. Meckel (2003). Tectonics of the Hjort region of the Macquarie Ridge Complex, southernmost Australian-Pacific Plate Boundary, southwest Pacific Ocean (PhD) (Thesis). pp. 1–206. Bibcode:2003PhDT.......206M.
4. Shuck, B.; Van Avendonk, H.; Gulick, S. P. S.; Gurnis, M.; Sutherland, R.; Stock, J.; Patel, J.; Hightower, E.; Saustrup, S.; Hess, T. (2021). "Strike-slip enables subduction initiation beneath a failed rift: New seismic constraints from Puysegur Margin, New Zealand". Tectonics. 40 (e2020TC006436). Bibcode:2021Tecto..4006436S. doi:10.1029/2020TC006436. S2CID 235553788.
5. "USGS:Historic seismicity". Retrieved 4 June 2023.
6. "USGS M 5.9 – Macquarie Island region 2023-06-09 21:21:42 (UTC)". Retrieved 9 June 2023.
7. Gasperini, Luca; Ligi, Marco; Accettella, Daniela; Bosman, Alessandro; Cuffaro, Marco; Lodolo, Emanuele; Martorelli, Eleonora; Muccini, Filippo; Palmiotto, Camilla; Polonia, Alina (2022). "Late Miocene to recent tectonic evolution of the Macquarie Triple Junction" (PDF). Geology. 51 (2): 146–150. doi:10.1130/G50556.1. S2CID 254949707.

External links

• "Marine Gazetteer Placedetails: Emerald Fracture Zone".

 This article incorporates public domain material from "Emerald fracture zone". Geographic Names Information System. United States Geological Survey.