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| Titel |
Tectono-stratigraphic evolution of the northern margin of the Amu Darya basin in Uzbekistan (Bukhara-Khiva and South-West Gissar regions) |
| VerfasserIn |
Dmitriy Mordvintsev, Marie-Francoise Brunet, Eric Barrier, Jean-Luc Auxiètre, Christian Blanpied, Hermann Munsch, 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 |
250095993
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| Publikation (Nr.) |
 EGU/EGU2014-11473.pdf |
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| Zusammenfassung |
| The main purpose of this work is the reconstruction of the geological, tectonic and
stratigraphic evolution of the northern margin of the Amu Darya basin in Uzbekistan,
especially during the Mesozoic time. The area considered is running from the Bukhara-Khiva
region in the North-West (studied by subsurface data) to the mountains of South-Western
Gissar in the South-East. To reach this objective we aim at studying and comparing these
areas. The Bukhara-Khiva area consists of two NW-elongated steps – Bukhara and
Chardzhou, divided by a main fault-flexural zone, called Uchbash-Karshi flexure-fault
zone.
Eight geological-geophysical sections have been reconstructed in the Bukhara-Khiva area
by using seismic, well and map data. Six of them, roughly N-S trending, are almost
perpendicular to the trend of the steps, while the two others, running along the Bukhara and
Chardzhou steps are NW-oriented. All of these sections show the lateral distributions,
thickness variations and unconformities between the main stratigraphic horizons. These
horizons are the tops of: 1. the pre-Jurassic formations (Paleozoic - Permo-Triassic), 2. the
Lower-Middle Jurassic clastics, 3. the Middle-Upper Jurassic carbonates, 4. the
Upper Jurassic evaporites, 5. the Lower Cretaceous and 6. the Upper Cretaceous
beds.
The Bukhara step constitutes the northern part of the area. It is characterized by very thin
Jurassic deposits (sometimes missing as the evaporites) no more than 300 m thick. The
distribution of the different Jurassic formations is intermitted; the most extended one is the
carbonate layer. Most of the Jurassic sediments are concentrated in the Chardzhou step, the
southern part of the investigated area, where their thickness reaches more than 2 km. All
formations are well-developed and rather thick in comparison with the Bukhara step. The
Jurassic beds display different morphological-structural features. In the Bukhara step most of
the surfaces exhibit a very rough relief with abundant faults. However, the same
horizons in the Chardzhou step are flat, and the faults only exist in the western
area.
The Cretaceous beds disconformably cover the Jurassic series and have a similar
thickness (800-1500 m) on both steps.
Another part of the study is the tectonic subsidence analysis, performed through a dozen
of wells in the Bukhara-Khiva region, and three in South-Western Gissar. The preliminary
results show an active tectonic subsidence during the late Early Jurassic to Middle Jurassic,
and a minor event during the Early Cretaceous.
The third part of the study concerns the paleostress reconstruction and fault tectonic
analysis. Such an approach has been performed in the Gissar Mountains where the
Mesozoic-Cenozoic sequence is well exposed. The first results indicate that normal faulting
developed during the Mid-Late Jurassic associated with the NE-trending extension that
developed in the northern Amu Darya margin. |
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