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| Titel |
Plio-Pleistocene Stratigraphy of the Kura Basin, Azerbaijan: Implications for the Formation of the Greater Caucasus and Kura Fold-Thrust Belt |
| VerfasserIn |
Adam Forte, Eric Cowgill, Ibrahim Murtuzayev |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046028
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| Zusammenfassung |
| The west-northwest trending Greater Caucasus Mountains form the northern edge of the
Arabia-Eurasia collision within the Alpine-Himalayan belt. Recent thermochronologic work
suggests the Greater Caucasus initiated in the west and that rock uplift has propagated
eastward overtime. Since the Pliocene, the main locus of shortening has shifted south, from
the Greater Caucasus to the Kura fold-thrust belt in Georgia and Azerbaijan. Eastward
decreasing structural complexity and depth of exposure within the fold-thrust belt suggest
diachronous initiation and eastward propagation similar to the Greater Caucasus. The south-
and eastward propagation of this fold-thrust belt into the Kura foreland basin has
progressively deformed and exposed sediments shed during earlier stages of Greater
Caucasus uplift.
The lithology, petrography, and geochemistry of age-correlative Kura Basin sediments
exposed within the central (~46.8Ë E) and eastern (~47.8Ë E) portions of the Kura
fold-thrust belt vary significantly both along- and across-strike. Four measured
sections, three within the central portion and one in the eastern section, expose
compositionally immature sediments of heterogeneous siliciclastic lithologies. The
three central sections measured across the fold-thrust belt (perpendicular to the
strike of the fold-thrust belt and Greater Caucasus) interrogate mainly Pliestocene
age sediments, with the northernmost, section extending into the Pliocene aged
Productive Series. Lithologies suggests that for much of the Pliestocene an extensive
braid plain extended ~30 km southwestward from the modern Greater Caucasus
rangefront. Just north of the modern Mingachevir reservoir, exposures of predominantly
fine grained sediments are consistent with a shallow lake with occasional aerial
exposure existing for much of the Pleistocene. South of the Mingachevir reservoir, the
sediments record a large east-west striking meandering fluvial system, similar to
the modern southeast-flowing Kura River, indicating the main axis of the Kura
Basin at this longitude has remained relatively stationary since the Pleistocene. The
easternmost section records a marked upwards coarsening, with fine grained muds at the
base transitioning to coarse conglomerates. This section was previously mapped as
mid-upper Apsheron (1.2 – 0.7 Ma), but geochemical correlation of an intercalated ash
horizon near the top of the section to an ash in the central sections known to be
~1.2 Ma instead suggests that the base of this section extends to between ~3-4
Ma.
Whole-rock sandstone geochemistry suggests along-strike spatial and temporal variations
in the source area for the Kura Basin sediments. In particular we identify three “units” based
on tightly grouped populations on Th-Sc-Zr/10 and La-Th-Sc discriminatory diagrams.
These populations contain rocks of similar age within measured sections in the
central region, but differing age when comparing the central and eastern regions.
Investigation of these populations petrographically and with additional geochemical
discrimination diagrams suggest they generally correlate to both an overall decrease in the
input of volcanic material over time, but also a change in source material from
intermediate to progressively more felsic volcanic. These results suggest that in
the central portion of the belt, during the late Pliocene and early Pleistocene, the
predominant source areas were intermediate volcanic or volcaniclastic rocks, potentially of
the Vandam arc, which were progressively exhumed and completely eroded in the
section of the Greater Caucasus north of the central region. These source rocks
are no longer exposed within this portion of the Greater Caucasus, instead only
occurring to the east. Contrastingly, Plio-Pleistocene age sediments within the eastern
region indicate that volcanics and volcaniclastics were never a significant source,
suggesting that the modern the Vandam arc rocks directly north of these sections
have been exposed only post ~1 Ma. Collectively these data are consistent with
thermochronologic evidence suggesting an eastward propagation of the Greater Caucasus. |
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