Geology of the Falkland Islands

Phil Stone (UK) Plate tectonics have produced some surprising juxtapositions, as the earth’s continental fragments have drifted and jostled over the eons. Microplates seem to have enjoyed most freedom of movement and none more so than that supporting the Falkland Islands. Though this archipelago is situated in the south-west corner of the South Atlantic Ocean, about 650km east from Tierra del Fuego and the Strait of Magellan, its geology tells of an African heritage. Charles Darwin provided the first evidence for that – although he didn’t appreciate it at the time. Fig. 1. A reconstruction of the Gondwana supercontinent at about 300mya. (© BGS/NERC.) HMS Beagle visited the Falkland Islands twice, in 1833 and 1834, and during the first visit Darwin discovered fossil shells, mostly brachiopods. His first impression had been unfavourable, but, after that discovery, he noted in his diary: “The whole aspect of the Falkland Islands were however changed to my eyes … for I found a rock abounding with shells; and these of the most interesting age.” Darwin published his account of Falklands’ geology in 1846. The “interesting age” proved to be Devonian and, as more data were acquired, a close and surprising similarity was established with the fauna of equivalent age in South Africa. This similarity was soon extended to other aspects of the Falklands rock succession, while the geology of neighbouring Patagonia proved to be quite different. These relationships were not readily explicable without recourse to continental drift, so were largely ignored for many years, … Read More