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The geology of South Georgia and the South Sandwich Islands is part of the largely submerged Scotia Ridge. The island of South Georgia is unusual among oceanic islands for having pre-Cretaceous sedimentary rocks underlying much of the island and a significant portion of felsic igneous rocks. Two-thirds of the island consists of intensely folded flysch, capped with Aptian age fossils, tuff and greywacke in the Cumberland Bay Series. The series includes slate, phyllite, conglomerate, siltstone and sandstone. In the west are basalt flows, pillowed spilite, prehnite and trachyandesite, as well as shale with radiolarite fossils.

Uranium-lead dating of zircon and muscovite grains from the southern Andes and South Georgia (gathered from the peraluminous Darwin granite suite and undersea Tobifera Formation rhyolite) indicates that the rocks formed during the middle Jurassic. The grains were likely remnant from 1.5 billion years ago.

The fragmentation of the Gondwana supercontinent is preserved in an ophiolite in the Rocas Verdes marginal basin—part of the Larsen Harbour complex on South Georgia. As the continent fragmented, oceanic crust formed in the Weddell Sea in the Middle Jurassic. The ridge's Beagle granite suite has complicated uranium-lead data. Feldspar phenocrysts formed in cracks within the Beagle granite pluton, likely related to the tectonism affecting the high-grade metamorphic rocks of the Cordillera Darwin in Tierra del Fuego.

See also

• Scotia Plate – Minor oceanic tectonic plate between the Antarctic and South American platesPages displaying short descriptions of redirect targets
• South Sandwich Plate – Small tectonic plate south of the South American platePages displaying short descriptions of redirect targets

References

1. Frakes, Lawrence A. (1966). "GEOLOGIC SETTING OF SOUTH GEORGIA ISLAND | GSA Bulletin". Geological Society of America Bulletin. 77 (12): 1463. doi:10.1130/0016-7606(1966)77[1463:GSOSGI]2.0.CO;2. Retrieved 6 November 2018.
2. Mukasa, Samuel B.; Dalziel, Ian W.D. (1996). "Southernmost Andes and South Georgia Island, North Scotia Ridge: Zircon U-Pb and muscovite 40Ar39Ar age constraints on tectonic evolution of Southwestern Gondwanaland". Journal of South American Earth Sciences. 9 (5–6): 349–365. doi:10.1016/S0895-9811(96)00019-3.

v t e  South Georgia and the South Sandwich Islands
Capital: King Edward Point
General	Coat of arms Commissioner Flag Foreign relations History Languages List of South Georgians Operation "Paraquet" Public holidays Toothfish Day South Georgia Museum .gs Sovereignty Invasion of South Georgia
Settlements / Whaling stations	Bird Island Grytviken Godthul Husvik King Edward Point Leith Harbour Ocean Harbour Prince Olav Harbour Stromness Corbeta Uruguay base
South Georgia islands	Annenkov Island Bird Island Black Rock Black Rocks Clerke Rocks Cooper Island Grass Island Grassholm Kupriyanov Islands Pickersgill Islands Prion Island Saddle Island Shag Rocks South Georgia Island Welcome Islands Willis Islands
South Sandwich Islands	Bristol Montagu Saunders Candlemas Islands Candlemas Vindication Traversay Islands Leskov Visokoi Zavodovski Southern Thule Bellingshausen Cook Thule
Seamounts	Protector Shoal Kemp Caldera
Landmarks	Admiralty Peak Allardyce Range Barff Peninsula Fortuna Glacier Gold Harbour Larsen Harbour Mount Baume Mount Belinda Mount Cunningham Mount Paget Mount Roots Orca Peak Peggotty Bluff Salisbury Plain Salvesen Range Southern Thule Thatcher Peninsula Bay of Isles Stromness Bay Cumberland Bay Possession Bay Busen Point

• Geology of South Georgia and the South Sandwich Islands