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The Falkland Islands are located on a projection of the Patagonian continental shelf. In ancient geological time this shelf was part of Gondwana, which around 400 million years ago broke from what is now Africa and drifted westwards relative to Africa. Studies of the seabed surrounding the islands indicated the possibility of oil. Intensive exploration began in 1996,〔RICHARDS, P C, and HILLIER, B V. 2000. Post-drilling analysis of the North Falkland Basin: Part 1: Tectono-stratigraphic framework. Journal of Petroleum Geology, Vol. 23, 253-272.〕 although there had been some earlier seismic surveys in the region. Descriptions of the geology of the Falkland Islands are provided in several publications.〔ALDISS, D T, and EDWARDS, E J. 1998. Geology of the Falkland Islands. Geological map. 1:250 000. (Falkland Islands Government.)〕〔STONE, P, ALDISS, D T, and EDWARDS, E. 2005. Rocks and fossils of the Falkland Islands. (Nottingham, UK: British Geological Survey.)〕〔STONE, P, and ALDISS, D T. 2000. The Falkland Islands. Reading the rocks - a geological travelogue. (Keyworth, Nottingham, NG12 5GG: British Geological Survey for Falkland Islands Government.) STONE, P, and ALDISS, D T. 2001. The Falkland Islands. Stone runs - rock in the landscape. (Keyworth, Nottingham, NG12 5GG: British Geological Survey for Falkland Islands Government.) 〕 ==Geological history == The geological history of the Falkland Islands began more than 1000 million years ago, before they existed as separate islands. The breakup of Gondwana led to the formation of a large number of minor crustal fragments, including the Falkland Islands. At first, the fragment containing the islands separated from the southeastern part of Africa on a section that would become Antarctica and later rotated by almost 180°. The interior of Gondwana was based on crystalline rocks more than a billion years old; in the Falklands today these are found in the Cape Meredith complex. Sand and mud filled and eventually covered the developing continental rifts. Later these sediments covering the rifts hardened into rock. These rock sequences from Gondwana's break-up can be identified in places as far apart as South Africa, western Antarctica and Brazil. In the Falkland Islands, these sequences are known as the West Falkland Group. Two hundred million years ago, tectonic forces tore Gondwana apart. Sheets of liquid basalt intruded into the cracks that formed between the sedimentary layers. The resulting solidified sheets can now be seen in the form of dikes that cut the oldest sedimentary layers, those that lie principally in the southern part of East Falkland and in South Africa. Tectonic forces continued to form the region: a mountainous chain formed, part of which now forms Wickham Heights on East Falkland Island and extends westwards through West Falkland into the Jason Islands. A basin developed and was filled with land-based, or ''terrigenous'', sediments. These layers of sand and mud filled the basin as it sank; as they hardened, they produced the rocks of the sedimentary Lafonia Group of the Falklands. These rocks are similar to those in southern Africa's Karoo basin. About 290 million years ago, in the Carboniferous period, an ice age engulfed the area as glaciers advanced from the polar region, eroding and transporting rocks. These rocks were deposited as extensive moraines and glacial till. When the glacial sediments were turned into stone they formed the rocks that now make up the Fitzroy Tillite Formation in the Falklands. Identical rocks are found in southern Africa. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Geology of the Falkland Islands」の詳細全文を読む スポンサード リンク
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