Three Kings Ridge
Three Kings Ridge | |
---|---|
Ma | |
Zealandia | |
Type | Igneous |
Lithology | |
Primary | Basalt, mantle peridotite, trachybasalt through to rarer andesite |
Location | |
Coordinates | 31°03′S 172°51′E / 31.05°S 172.85°E |
Region | South Pacific |
Country | New Zealand |
Type section | |
Named for | Three Kings Islands |
The Three Kings Ridge, sometimes known as Three Kings Rise and more rarely at its southern end as the Three Kings Bank is a
Geology
The ridge along with its northern continuation, the Loyalty Ridge that extends north of New Caledonia, is now a relatively well studied, greater than 3,000 km (1,900 mi) long feature of Zealandia tectonics.[2] It is a relatively rigid portion of continental crust compared to the oceanic crust in surrounding basins about 25 km (16 mi) in thickness.[3] While regarded as inactive there have been moderate sized earthquakes at the northern end of the ridge.[4] It can be regarded as a stranded western remnant arc segment split off by intra-arc and cross-arc rifting during back-arc basin opening from the still active eastern arc segments close to the Pacific trench and slab.[2] The 400 km (250 mi) long[5] Cook Fracture Zone that is aligned with the two ridges separates it from the Loyalty Ridge and is associated with about 250 km (160 mi) lateral displacement at the southern end of the central Minerva-Cook spreading zone of the South Fiji Basin.[2] In the middle of the area between the two ridges is the youngest dated volcanics, being the DR22A seamount at 19.7 ± 0.5 Ma.[2] The northern deep tip of the ridge has mudstone at 3,700 m (12,100 ft) water depth that is stratigraphically dated to 20.9 to 18.7 Ma.[2] To its east is the Norfolk basin separating it from the Norfolk Ridge in the Tasman Sea. To its west is the South Fiji Basin with its former spreading sea floor of the Cook Fracture Zone. To its south a trough extends from the Norfolk Basin separating it from the volcanic alignment of the Norfolk Ridge with the northern North Island.[2] It has been postulated that the Three Kings Ridge has been subsequently separated by the now inactive Vening Meinesz Fault Zone from the Miocene volcanic arcs of Northland in the North Island, and its extension under the Tasman Sea of the Northland Plateau.[6] However, there is a distinct age difference between the 25 million years ago dates of the southern part of the ridge eruptives and the nearest North Island volcanics.[5]
The
Tectonic implications
It has been postulated that the relatively rigid Three Kings Ridge had a role in the emplacement of the
Islands, reefs and seamounts
The ridge has to its south a group of 13 presently uninhabited islands where the
Bio-genetic separation
There is genetic drift evidence in insect and snail populations that these islands have been connected together but separate from the North Island from the point of view of individual species for up to 24 million years, but as recently as 2.24 million years with others.
See also
- Lord Howe Rise – Deep sea plateau from south west of New Caledonia to the Challenger Plateau, west of New Zealand
- Chatham Rise – An area of ocean floor to the east of New Zealand, forming part of the Zealandia continent
- Norfolk Ridge – Submarine ridge between New Caledonia and New Zealand
- South Tasman Rise – Area of seafloor about 1500 m deep south of Hobart, Tasmania in the Southern Ocean
References
- ^ Judd, Warren (1996). "The clifftop world of the Three Kings". New Zealand Geographic (29). Retrieved 28 February 2023.
- ^ S2CID 255041563.
- ^ S2CID 56089661.
- ^ USGS Regional Information:Seismotectonics of the Eastern Margin of the Australia Plate
- ^ S2CID 254306179.
- ^ .
- ^ S2CID 130355847.
- ^ "Estuary origins". National Institute of Water and Atmospheric Research. Retrieved 1 March 2023.
- S2CID 83698404.
- doi:10.1071/MR03001.