Extensional collapse of orogens
Tóm tắt
Lithospheric extension is sited, preferentially, along orogenic belts because they have a thicker continental crust, contain structural inhomogeneities, and suffer extensional orogenic collapse caused by body forces resulting from isostatically compensated elevation and sharp elevation gradients. Collapse occurs especially where rapid advective thinning of the shortened thermal boundary conduction layer occurs beneath an orogen and causes rapid uplift. Where boundary forces are compressional, extension is balanced by radial thrusting to form oroclinal loops around collapsed extensional basins. Where, as in the disruption of Pangea, boundary forces change rapidly from compressional to tensional, body force collapse is continued by general extension which may lead to continental splitting. Even where overall convergence is continuing, orogenic collapse may be enhanced by subduction rollback into small remnant oceans. The extensional collapse of orogens offers a partial explanation for why oceans cyclically close and reopen in roughly the same places, preservation of very high pressure metamorphic rocks, for the return of orogenic large crustal thicknesses to normal without very much erosional denudation with the widespread preservation of supracrustal sequences, high temperature metamorphic assemblages and the minimum‐melting granite suite.
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Tài liệu tham khảo
Bird P., Formation of the Rocky Mountains, western United States: A continuum computer model, Science, 240, 1501
Buck R., 1988, Flexural rotation of normal faults to produce abandoned horizontal detachments, E. Trans. AGU, 69, 465
Carey S. W., 1955, The orocline concept in geotectonics, Proc. Pap. R. Soc. Tasmania, 89, 255
Dewey J. F., 1980, Episodicity, sequency and style at convergent plate boundaries, The Continental Crust and its Mineral Deposits, edited by D.W. Strangway, Spec. Pap., Geol. Assoc. Can., 20, 553
Hills E. S., 1956, A contribution to the morphotectonics of Australia, J. Geol. Soc. Aust., 3, 1
Wezel F. C., 1982, The Tyrrhenian Sea: A rifted Krikogenic‐Swell basin, Mem. Geol. Soc. Italy, 24, 531
Williams D. M., 1988, Tectonic denudation of Dalradian rocks, Connemara, Ireland, Tectonics
Zwart H. J., 1967, The duality of orogenic belts, Geol. Mijnbouw, 46, 283