|
The Canterbury Region of New Zealand corresponds to the portion of the South Island to the east of the Southern Alps, from the Waiau River in the north, to the Waitaki River in the south. To the west of the Southern Alps lies the Alpine Fault, a major fault boundary, that passes through the South Island from Fiordland in the south, to the Marlborough Region in the north, where it divides into multiple faults. The Pacific Plate lies to the east of the Alpine Fault and the Australian Plate lies to the west. The Pacific Plate is sliding SSW at about 35mm/yr, relative to the Australian Plate, and rising up 10mm/yr, generating the Southern Alps. The Alpine Fault did not develop until early Miocene times (23 Ma). Ten million years ago the Southern Alps were low hills, and they only became mountainous as recently as 5 million years ago. To the east of the Southern Alps are the Canterbury Plains, formed by the sediment eroded from the Southern Alps. On the coast, just southeast of Christchurch, is Banks Peninsula, composed of two large mainly basaltic Miocene volcanoes. ==Basement Rocks== All basement rocks beneath the Canterbury Region belong to the Torlesse Composite (Rakaia and Pahau) Terrane. They are largely composed of greywacke (hardened sandstone and mudstone), that accumulated in a deep marine environment, and were accreted to the Gondwana continent, before the Tasman sea opened up in late Cretaceous times (80 Ma). They outcrop in the Southern Alps and the foothills. The Rakaia Terrane rocks, of Permian to late Triassic age (300-200 Ma), occur south of Rangiora. The Pahau Terrane rocks, of late Jurassic to early Cretaceous age (160-100 Ma), occur to the north, and are probably derived from the Rakaia Terrane. At the boundary between these two terranes, is the Esk Head Belt, an 11 km wide melange of broken and deformed rocks. The basement rocks just to the east of the Alpine Fault and to the south of Timaru have been metamorphosed into Schist. 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 Canterbury, New Zealand」の詳細全文を読む スポンサード リンク
|