Deep Structure and Past Kinematics of Accreted Terranes
1990; Wiley; Volume: 71; Issue: 40 Linguagem: Inglês
10.1029/90eo00312
ISSN2324-9250
Autores Tópico(s)Geology and Paleoclimatology Research
ResumoAn “accreted terrane” is simply a block of light crust that has been added to a continental margin during the collision of lithospheric plates. At subduction zones, terranes might be seamounts, continental slivers, ophiolites, deep‐sea fans, or old volcanic arcs that have been swept from the under riding plate, like packages falling into a basket at the end of a conveyor belt. Accretion also occurs by oblique slip along transform‐fault boundaries. Some terranes are exotic, whereas others might be native crust that has been dislodged by rifting or lateral faulting, then transported to a new location. Geologists have been writing about accreted terranes for many years, but only during the last decade has the concept been tested in detail by geophysical methods. For example, paleomagnetic studies in the Cordillera of western North America have revealed discordant paleolatitudes, implying that some terranes have moved thousands of kilometers relative to the craton. In some cases, paleomagnetic discordance is in tune with marked contrasts in fossil assemblages or stratigraphic mismatches that suggest large‐scale offsets across fault zones. In others, paleolatitude shifts derived from paleomagnetism have exceeded displacements inferred from geologic mapping, prompting close scrutiny of the geologic and paleomagnetic evidence.
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