TITLE:
Late Cenozoic Tectonic Uplift Producing Mountain Building in Comparison with Mantle Structure in the Alpine-Himalayan Belt
AUTHORS:
Vladimir G. Trifonov, Sergey Yu. Sokolov
KEYWORDS:
Late Cenozoic Uplift, Mountain Building, Seismic Tomography Profiles, Lithosphere, Asthenosphere
JOURNAL NAME:
International Journal of Geosciences,
Vol.5 No.5,
April
29,
2014
ABSTRACT: Tectonic
uplift producing recent mountain systems has spanned in the Alpine-Himalayan
Belt the time interval from Oligocene to Recent (the last 30 - 35 Ma), being
divided into two stages. During the first stage, local uplands, usually not
higher than middle-elevated mountains, rose and their total area increased.
During the second stage (the last 5 - 2 Ma) this process was accompanied by a
total uplift of the greater part of the belt. As a result, the rate of vertical
movements increased, the recent mountain systems were formed, and the coarse
molasses accumulated in the adjacent basins. Uplift of the land surface
resulting in formation of mountain topography is an isostatic reaction to
decompaction of the upper spheres of the Solid Earth. Three factors of the
decompaction are discussed in the paper. These are: I, collisional compression,
resulting in deformational thickening of the Earth’s crust (folding, thrusting,
etc.); II, partial replacing of the lithosphere mantle by the lower-dense
asthenosphere material and, as a result, decompaction of the uppermost mantle;
and III, retrograde metamorphism of high-metamorphosed rocks within the lower
crust and near the crust-mantle boundary and, as a result, decompaction of
these rocks. These processes were initiated or facilitated by the lateral asthenosphere flows. According to the seismic
tomography data, the flows spread from the stationary developed zone of the
rise of deep mantle material that is expressed in the recent structure as the
Ethiopian-Afar super-plume. Reworking the 400 - 700-km deep transition layer of
the mantle, the sub-lithosphere flows could be enriched in sources of aqueous
fluids. The flows and their fluids initiated factors II and III of the tectonic
uplift and caused softening and detachment of the lithosphere, facilitating
deformational thickening of the Earth’s crust, i.e., the factor I. The latter produced uplands during the entire
Oligocene-Quaternary development of the orogenic belt, while the factors II and
III manifested themselves only during the second stage of mountain building.
The detailed studies in the Central Tien Shan and the Greater Caucasus showed
that the acceleration of uplift at the second stage was caused mainly by the
factor II in the Central Tien Shan and the factor III in the Greater Caucasus.