Terrane

Terrane
In geology, a terrane (in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or "sutured" to crust lying on another plate. The crustal block or fragment preserves its distinctive geologic history, which is different from the surrounding areas—hence the term "exotic" terrane. The suture zone between a terrane and the crust it attaches to is usually identifiable as a fault. A sedimentary deposit that buries the contact of the terrane with adjacent rock is called an overlap formation. An igneous intrusion that has intruded and obscured the contact of a terrane with adjacent rock is called a stitching pluton.
The older usage of terrane described a series of related rock formations or an area with a preponderance of a particular rock or rock group.
Overview
A tectonostratigraphic terrane is not necessarily an independent microplate in origin since it may not contain the full thickness of the lithosphere. It is a piece of crust that has been transported laterally, usually as part of a larger plate, and is relatively buoyant due to thickness or low density. When the plate of which it was a part subducted under another plate, the terrane failed to subduct, detached from its transporting plate, and accreted onto the overriding plate. Therefore, the terrane transferred from one plate to the other. Typically, accreting terranes are portions of continental crust which have rifted off another continental mass and been transported surrounded by oceanic crust, or they are old island arcs formed at some distant subduction zones.
A tectonostratigraphic terrane is a fault-bounded package of rocks of at least regional extent characterized by a geologic history that differs from that of neighboring terranes. The essential characteristic of these terranes is that the present spatial relations are incompatible with the inferred geologic histories. Where terranes that lie next to each other possess strata of the same age, it must be demonstrable that the geologic evolutions are different and incompatible. There must be an absence of intermediate lithofacies that could link the strata.
The concept of tectonostratigraphic terrane developed from studies in the 1970s of the complicated Pacific Cordilleran orogenic margin of North America, a complex and diverse geological potpourri that was difficult to explain until the new science of plate tectonics illuminated the ability of crustal fragments to "drift" thousands of miles from their origin and fetch up, crumpled, against an exotic shore. Such terranes were dubbed "accreted terranes" by geologists.
When terranes are composed of repeated accretionary events, and hence are composed of subunits with distinct history and structure, they may be called superterranes.
Tectonostratigraphic terranes
Africa
Alkapeca
Birminian Terrane
Kahiltna Terrane
Likasi Terrane
Mozambique Belt
Asia
Aldan Terrane
Birekte Terrane
Bargusin Terrane
Daldyn Terrane
Magan Terrane
Markha Terrane
Midyan Terrane
Shan–Thai Terrane
Tungus Terrane
Tynda Terrane
Uchur Terrane
Taiwan
Coastal Range Terrane
Longitudinal Valley Terrane
Eastern Central Range Terrane
Western Central Range Terrane
Hsuehshan Range Terrane
Western Foothills Terrane
Coastal Plain Terrane
Tibet
Lhasa Terrane
Qiangtang Terrane
Xigaze Terrane
Bainang Terrane
Zedong Terrane
Dazhuqu Terrane
Australasia
Brook Street Terrane
Buller Terrane
Caples Terrane
East Tasmanian Terrane
Glenburgh Terrane
Dun Mountain-Maitai Terrane
Molong—Monaro Terrane
Murihiku Terrane
Narryer Gneiss Terrane
Takaka Terrane
Torlesse Composite Terrane
Waipapa Composite Terrane
West Tasmanian Terrane
Europe
Alkapeca
Armorican terrane
Avalonia
Avalon Composite Terrane
Balearic Terrane
Briançonnais Terrane
Central Highlands Terrane
Central Southern Uplands Terrane
Charnwood Terrane
Hebridean Terrane
Leinster—Lakesman Terrane
Midland Valley Terrane
North Armorican Composite Terrane
Northern Highlands Terrane
Rosslare—Monian Terranes
Southern North Sea Terrane
Tregor—La Hague Terrane
Wrekin Terrane
Fennoscandia
Bamble Terrane
Idefjorden Terrane
Kongsberg Terrane
Telemarkia Terrane
Western Gneiss Region
North America
Avalonia Terrane
Bancroft Terrane
Buffalo Head Terrane
Cache Creek Terrane
Carolina Terrane
Cassiar Terrane
Crescent Terrane
Elzevir Terrane
Frontenac Terrane
Franciscan Complex
Ganderia Terrane
Hottah Terrane
Insular Superterrane
Intermontane Plate and Intermontane Belt
Meguma Terrane
Occidentalia Terrane
Pacific Rim Terrane
Pearya Terrane
Quesnellia
Salinian Block
Slide Mountain Terrane
Smartville Block
Sonomia Terrane
Steel Mountain Terrane
Stikinia
Wrangellia Terrane
Yakutat Block
Yukon—Tanana Terrane
South America
Arequipa-Antofalla
Chaitenia
Chilenia
Chiloé Block
Cuchilla Dionisio Terrane
Cuyania
Fitz Roy Terrane
Madre de Dios Terrane
Mejillonía
Nico Pérez Terrane
Pampia
Paranapanema block
Piedra Alta Terrane
Tandilia Terrane
References
Citations
General bibliography
McPhee, John (1981). Basin and Range. New York: Farrar, Straus and Giroux.
McPhee, John (1983). In Suspect Terrain. New York: Farrar, Straus and Giroux.
McPhee, John (1993). Assembling California. New York: Farrar, Straus and Giroux.
External links
West Antarctica terrane analysis
Examples of accreted terrane in Idaho
Alaskan Terranes