Geology Reference
In-Depth Information
The sub-latitudinal faults are, north to south: Derbent-Krasnovodsk (I
I),
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North Apsheron (II
II), Apsheron-Balkhan (III
III), Sangachal-Ogurchin
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(IV
IV), Milsk-Chikishlyar (V
V), Pre-Caucasus Minor (VI
VI), Elburs
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(VII
VII); and the diagonal faults are: Adjikabul-Mardakyany (XVI
XVI)
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and the Abich Swell fault (XVII
XVII).
The indicated lineaments bind and define the following major tectonic
elements in the SKB structure. On the west flank, onshore (west to east): the
Lower Kura Depression, Alyat Ridge, Kobystan with the Djeirankechmes
Depression, the Apsheron Peninsula folding; offshore: South Apsheron
trough (South Apsheron shelf ), the Baku Archipelago folded zone. On the
north flank, folding of the Caucasus Major meganticlinorium southeast-
ern plunge: onshore, North Apsheron Depression, North Apsheron zone
of uplifts, Artem-Kelkor Trough; offshore: the western and central parts
of the Apsheron-Balkhan sill. On the eastern flank, the Balkhan area of
uplifts (eastern onshore part of the Apsheron-Balkhan sill), the Kyzyl-
Kum trough, the Gorgandag-Chikishlyar zone of uplifts - onshore and
offshore - the Turkmen structural terrace. On the southern flank of the
basin, the Lenkoran-Gorgan trough offshore and the onshore portion of
the Pre-Elbrus trough. And in the central part of the basin, the folding of
the deep-water South Caspian Depression with the Abich Swell and the
Sary-Chikishlyar zone of folds (see Figure 1.1).
The general SKB geology displays a number of characteristic features.
The structural architecture of the Mesozoic structural-formational stage
does not match that of the Cenozoic one. A typical feature of the basin
is geologically frequent change in the direction and sign of the regional
tectonic motions. The basin has a step-block structure. Different strati-
graphic complexes, intervals and lithofacies contact each other across the
regional faults. The section is quite variable in terms of lithofacies and res-
ervoir properties; some Cenozoic intervals were formed in the environ-
ment of avalanche deposition. The PT-KT (Productive Sequence-Red-Bed
Sequence) section is rhythmical, with clay varieties periodically replaced
in the section by sands. The PT-KT stratigraphic components region-
ally pinch-out both up- and down-dip of the general folding (Figure 1.2)
thereby forming lenses. There are clear indications of the paleotectonic
and neotectonic stress. Widespread is a powerful fault, diapir, fracture and
nappe overthrust tectonics with common mélange-like “twisted” lamina-
tion of the crushed clays, carinate and “overturned” folded forms.
In some regions, density inversion of the depositional section is observed
with thick unconsolidated (sometimes even quasi-liquefied) high-porosity
water-saturated plastic (mostly montmorillonite) clays. Some seismic
velocity inversions are encountered with chaotic seismic events on the
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