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| Titel |
Mesozoic evolution of the Amu Darya basin |
| VerfasserIn |
Marie-Francoise Brunet, Andrey Ershov, Maxim Korotaev, Dmitriy Mordvintsev, Eric Barrier, Irina Sidorova |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095431
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| Publikation (Nr.) |
 EGU/EGU2014-10882.pdf |
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| Zusammenfassung |
| This study, granted by the Darius Programme, aims at proposing a model of tectono-stratigraphic
evolution of the Amu Darya basin since the Late Palaeozoic and to understand the
relationship with the nearby basins. The Amu Darya basin, as its close eastern neighbour, the
Afghan-Tajik basin, lies on the Turan platform, after the closure of the Turkestan Ocean
during the Late Paleozoic. These two basins, spread on mainly lowlands of Turkmenistan,
southwest Uzbekistan, Tajikistan, and northern Afghanistan, are separated from one another
by the South-Western Gissar meganticline, where series of the northern Amu Darya margin
are outcropping.
The evolution is closely controlled by several periods of crustal thinning (post-collision
rifting and back-arc extension), with some marine incursions, coming in between accretions
of continental blocks and collisions that succeeded from the Late Triassic-Early Jurassic
(Eo-Cimmerian orogeny) to the Cenozoic times. These orogenies controlled the deposition of
thick clastics sequences, and the collision of the Indian Plate with Eurasia strongly deformed
the sedimentary cover of the Afghan-Tajik basin.
The more than 7 km thick Meso-Cenozoic sedimentary succession of the Amu Darya
basin, lies on a complex system of rifts and blocks. Their orientation and age (late Permian,
Triassic?) are not well known because of deep burial. The north-eastern margin, with the
Bukhara (upper margin) and Chardzhou steps, is NW oriented, parallel to the Paleozoic
Turkestan suture. The orientation bends to W-E, in the part of the Gissar situated to the North
of the Afghan-Tajik basin. This EW trending orientation prevails also in the south(-eastern)
margin of the basin (series of North Afghanistan highs) and in the Murgab depression, the
south-eastern deepest portion of the Amu Darya basin. It is in this area and in the eastern part
of the Amu Darya basin that the Jurassic as well as the lower Cretaceous sediments are the
thickest. The south-western part of the basin is occupied by the Pre-Kopet Dagh
Cenozoic foreland basin NW oriented, possibly underlain by an earlier extensional
trough.
The main elements of the sedimentary pile, which can be partly observed in the
South-Western Gissar are: Lower to Middle Jurassic continental to paralic clastic rocks;
upper Middle to Upper Jurassic marine carbonate then thick Tithonian evaporite rocks,
sealing the reservoirs in the Jurassic carbonates; continental Neocomian clastic rocks and red
beds, Aptian to Paleogene marine carbonate and clastic rocks.
To reconstruct the geodynamic evolution of the Amu Darya Basin, we analysed the
subsidence by backstripping of some wells/pseudo-wells and of three cross-sections with
some examples of thermal modelling on the periods of maturation of the potential source
rocks.
The crustal thinning events take place in the Permo-Triassic? (depending on the age of the
rifts underlying the basin), in Early-Middle Jurassic and during the Early Cretaceous,
resulting in increases of the tectonic subsidence rates. |
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