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The Phanerozoic history of continental cratons is marked by repeated global episodes of 3 types: (1) oscillatory--generally elevated or oscillating with respect to sea level; marginal and submarginal areas subject to highly differentiated uplift and subsidence; periodicity of oscillations and uplifts 105-106 years; wave lengths of intracratonic tectonic elements 101-102 km; duration of episodes 107-108 years; (2) emergent--progressively elevated in time; without significant topographic relief; tectonically undifferentiated below wave lengths of 103; duration 106-107 years; and (3) submergent--progressively depressed below sea level to form widespread epicontinental seas; sub pisodes (106-107 years) of differential subsidence to form basins and arches (^dgr = 102-103 km); duration 107-108 years.
Time relations of cratonic episodes are (1) oscillatory--much of Cenozoic, including present and period from Pennsylvanian to Early Jurassic (time spans of Appalachian-Hercynian, Laramide and Alpine orogenies); (2) emergent--latest Precambrian, early Middle Ordovician, Early Devonian, etc. (lacunal intervals between accumulations of cratonic sedimentary sequences); and (3) submergent--time spans of Caledonian, Antler-Acadian, and Nevadian orogenies.
In plate-tectonic terms, the present is characterized by high spreading rates and by convergent boundaries of oceanic and continental plates relatively remote from cratonic margins. These probably were the prevailing conditions during times of oscillatory cratonic behavior. Emergent cratons, by historical analysis, appear to be related to quiescent episodes at continental margins, possibly reflecting spreading-rate minima. Submergent cratons would seem to coincide with times of active plate convergence involving oceanic margins of cratons expressed by obduction and subduction at such margins.
Differences in cratonal tectonic habit may represent responses to either or both time-variable factors in continent-margin tectonics: variation in lateral stress transmitted to cratons from their margins, and variation in thickness, and thus in flexural rigidity of the continental lithosphere.
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