From high plateaux to marginal basins: the active role of the mantle

Abstract

Current geodynamic models pose many serious problems for the description of continental tectonic processes, Serious difficulties arise also in the description of some of the ocean basins. Deformation of the Earth's crust appears to be concentrated along several mobile megashear belts. It is proposed that these could be the surficial expression of ‘mantle chimneys’ which extend to great depths. Within these structures, post orogenic high plateaux form, and as time passes these develop a central depression enclosed within arcs or indeed full‐scale rings of mountains. The enlargement and deepening over time of the back‐arc depression occurs in concert with the radial migration of a ‘topographic wave’. In this respect, the following structures represent different phases in an evolutionary sequence: (a) the Tibetan Plateau, (b) the North American Cordillera, and (c) the Tyrrhenian Basin and Calabrian Arc. The development of this succession reflects a particularly high degree of activity in the mantle, in which diapiric rising of asthenospheric matter elevates the land and causes tensional rifting. The resulting centrifugal movement of the mantle melt results in crustal foundering and engulfment of the area behind the arc, which thus becomes susceptible to the subsequent processes of com‐pressional deformation.

Tectonic evolution of a sequence of related late Permian transtensive coal-bearing sub-basins, Mongolia: A global wrench tectonics portrait

“…Hence, "endogenic factors may be considered as the active prime-movers of global tectonics [and other surface products]. This hypothesis reflects a point of view in which the Earth is considered from its inner workings' outwards" (Wezel, 1992a(Wezel, , 1992b.…”

Global change in Earth history: a personal point of view

“…Morphogenetic uplift of the belt of compression begins the Pangaean regime, which is distinguished by a high degree of continentality, low sea levels, expanded land areas, amplified relief, high rates of erosion, and gradual climatic cooling and desertification, leading to ice ages. The period is one of global epeirogeny caused by mantle upflow (see Wezel, 1992, this issue). The topographic uplift of plateaux and mountain ranges is preceded first by regional metamorphism at high temperature and secondly by the emplacement of granitoids (Gansser, 1982).…”

“…I believe that the prinapal cause is a sudden, generalized transformation of the main areas occupied by mountain ranges and plateaux into topographic lows. Collapse of the orogens may lead to the separation of continents and the lateral migration of radial thrusts through the outer arcs (Dewey, 1988;Wezel, 1992).…”