Geology Reference
In-Depth Information
The Indol-Kuban Foredeep has a drastically asymmetric profile. Its
external northern flank adjacent to the Scythian Platform is broad and
low-angle with a monoclonal Tertiary complex. Its internal geosynclinal
(southern) flank is narrow and steep, intensely folded and faulted.
The southern flank comprises two structural stages. The lower one
includes the Mesozoic and Lower Paleogene and is deformed into a system
of narrow, often overturned folds. The upper one begins with the Middle
Maikopian and is mostly monoclonal.
Within the flank are identified several fault-associated sub-latitudinally-
trending anticlinal zones. These zones are the Kaluga (Seversk), Azov,
Levkin, Crimea-Seversk, Varenikov, Anastasiyev and Kerch-Taman. Each
of them includes clearly individualized local structures.
The Kaluga zone anticlines are buried under the monoclonal Pliocene-
Quaternary deposits and are clearly identified large, with relatively low-angle
slopes structures in the Upper Eocene cut with lengthwise and cross faults
with the throw of up to 100 m. The structures in the Azov and Levkin zones
flatten in the Lower Maikopian; these are typical fault-associated asymmet-
ric, often eroded high amplitude strongly faulted (block-type) anticlines,
sometimes with overturned flanks. The highs in the Crimean-Seversk zone
are diapirs and crypto-diapirs; they display strong morphologic expres-
sion up to the Quaternary. The Varenikov zone folds are relatively weakly
deformed brachi-anticlines. The structures in the Anastasiyev zone are low-
angle in the east portion and in the west, and in the next, Kerch-Taman
zone; they are clearly diapiric, with mud volcanism and intense faulting.
The region, especially its western portion, is affected by neotectonics
(active growth of diapire structures, present-day seismic activity, mud vol-
canoes, etc.).
Commercial oil and gas occurrences are found in the stratigraphic
range of the Upper Cretaceous (in the Kerch-Taman zone) through the
Cimmerian Stage (Middle Pliocene). The hydrocarbons are mostly oil.
The number of productive intervals in the fields reaches and sometimes
exceeds ten. The major identified resources are concentrated within the
Kuma Horizon (Upper Eocene) and the Miocene interval. About 70% of
the discovered accumulations are concentrated within depths shallower
than 2,000 m. The Foredeep includes a number of oil and gas accumula-
tion zones (whose names are the same as the zone names) with individual
dominating trap and accumulation types.
The Kaluga zone includes sheet-type anticlinal accumulations. In the
Azov zone, the lower section contains sratigraphic-type, fault-trapped and
sheet-type accumulations and the upper section, facies-change trapped
