A terrane in paleogeography is an accretion that has collided with a continental nucleus, or "craton" but can be recognized by the foreign origin of its rock strata. The boundaries of a terrane are usually represented by crustal faults. In the lithospheric scheme of plate tectonics, a terrane is not a microplate, but a piece of crust "riding" atop another plate. It can accrete to another piece of crust when the plate of which it is a part collides with the plate associated with the other crust. Palaeogeography is the study of the ancient geography of the Earths surface. ... See also: Accretion (finance) Accretion is increase in size by gradual addition of smaller parts. ... Color-coded regions of the world based on the seven commonly-recognised continents Dymaxion map by Buckminster Fuller shows land masses with minimal distortion as nearly one continuous continent A continent is one of several large areas of land on Earth, which are identified by convention rather than any strict... World geologic provinces. ... Fault in metamorphosed strata near Adelaide, Australia Geologic faults or simply faults are planar rock fractures which show evidence of relative movement. ... The tectonic plates of the Lithosphere on Earth. ... Bridge across the Álfagjá rift valley in southwest Iceland, the boundary of the Eurasian and North American continental tectonic plates. ...

The concept of terranes developed from studies in the 1970s of the complicated Western or Canadian Cordilleran ("backbone") orogenic margin of North America, a virtual geological lasagna that had remained an inexplicable apparent "irreducible complexity", 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 are dubbed accreted terranes by geologists. Orogeny is the process of mountain building, and as such is both a tectonic structural event, a geographical event and a chronological event, in that orogenic events happen within a time frame, affect certain regions of rocks and crust, and cause distinctive structural phenomena and related tectonic activity. ... Lasagna in the crinkly American style. ... Irreducible complexity (IC) is the argument that certain biological systems are too complex to have evolved from simpler, or less complete predecessors, and are at the same time too complex to have arisen naturally through chance mutations. ...

"It was soon determined that these exotic crustal slices had in fact originated as "suspect terranes" in regions at some considerable remove, frequently by thousands of kilometers, from the orogenic belt where they had eventually ended up. It followed that the present orogenic belt was itself an accretionary collage, composed of numerous terranes derived from around the circum-Pacific region and now ‘welded’ together along major faults. These concepts were soon applied to other, older orogenic belts, e.g. the Appalachian belt of North America.... Support for the new hypothesis came not only from structural and lithological studies, but also from studies of faunal biodiversity and palaeomagnetism." (Carney et al.)

For an example of a terrane, see Avalonia. Paleomagnetism refers to the orientation of the Earths magnetic field as it is preserved in various magnetic iron bearing minerals throughout time. ... Avalonia was a paleomicrocontinent also known as a Terrane. ...

See also Geology of Victoria The Australian state of Victoria rests at the southern end of the Great Dividing Range, which stretches along the east coast and terminates near Ballarat. ...

External links

• Paleos.com: Terranes
• Terrane: a definition
• New techniques for modelling terranes in three dimensions
• West Antarctica terrane analysis
• Examples of accreted terrane in Idaho

References

• J.N. Carney et al., Precambrian Rocks of England and Wales, GCReg. volume 20