Anadyr basin
in the Bering Sea
THE PETROLEUM SYSTEM-CONCEPT AND
APPLICATIONS
Gregory F. Ulmishek, U.S. Geological
Survey, Box 25046,
DFC, MS 940, Denver, CO 80225
Leslie B. Magoon U.S. Geological Survey,
3475 Deer Creek
Road, Palo Alto, CA 94304
A The petroleum system is becoming
accepted as a unifying
concept in which various research focused at finding new hydrocarbon
reserves
can be conducted more efficiently. Proposed definitions of the
petroleum
system vary.
The system is understood as a group of
discovered and/or
undiscovered genetically related hydrocarbon accumulations that
emanated
from a contiguous body of source rocks and that occupy a specific rock
volume.
The petroleum system map, which shows
source rocks and
the genetically related accumulations and cross sections which show the
stratigraphic position of the accumulations, clearly demonstrate the
explorationist's
interpretation of the origin and migration route of hydrocarbons.
Three petroleum systems are compared to
graphically demonstrate
how the concept is used in exploration, research and resource
appraisal.
The systems, from most to least explored:
Northern China in the Jizhong subbasin
Northern Alaska in the Colville basin
Anadyr basin in the Bering Sea
Although the amount of information varies
for each basin,
the petroleum system can be meaningfully portrayed. The exploration
geologist
can use the petroleum system map and cross sections to develop plays,
find
undiscovered commercial quantities of hydrocarbons within the system.
The
system map and cross sections can be used as an analog for another area
that contains a seldom-explored system. The research geologist can
investigate
and model how a system works, either in total or part, which helps in
locating
new plays and in decreasing exploration risk. The appraisal
geologist
can evaluate the petroleum system map from a historical view to study
discovery
rate process or compare similar systems that have different levels of
exploration
to determine the ultimate yield of the little explored system.
Fig, 6. Isopach map of the rocks of the
Anadyr basin showing
the supposed offshore petroleum system and cross-section on through the
onshore part of the basin. (The map is after Deter et al., 1986; the
cross-section
is after Marlow et al, 1983, with changes according to Krylov et al,
1988).
The offshore part of the Anadyr basin in
the Bering Sea
is an undrilled frontier, which contains a speculative petroleum
system.
A grid of seismic lines covers the area (Marlow et al., 1983), and
interpretation
of the seismic data is based on drilling in the onshore part of the
Anadyr
basin and in the Navarin basin to the south (Fig. 5).
Drilling in the onshore part of the
Anadyr basin revealed
a sedimentary section consisting of Upper Cretaceous through Pliocene
rocks
overlying the Jurassic-Lower Cretaceous basement and separated into
sequences
by pre-Eocene, pre-Miocene, and pre-middle Miocene unconformities
(Voronkov,
1987).
Several, non-commercial oil and gas
fields and a number
of hydrocarbon shows, which demonstrate a petroleum system, were found
in the deep part of the basin on the south.
Although geochemical data are limited,
the presumed source
rock occurs in the Eocene-Oligocene and possibly, in the lower Miocene
sequences (Ivanov et al., 1988). In the same stratigraphic
intervals,
source rocks have been identified in the Navarin basin (Steffy et al.,
1985). Therefore, a potential source rock can be expected in the
upper Paleogene through lower Miocene rocks in the offshore part of the
Anadyr basin.
Rocks of this stratigraphic interval are
present in the
southern depression of the offshore Anadyr basin where they occur at
depths
of up to 4 km (Fig. 6) (interpretation of seismic data Marlow et
al., 1983; Krylov et al., 1988).
The rocks pinch out toward the southern
and northern slopes
of the depression and on the Tuman uplift on the western flank.
Onshore, the top of the oil window
occurs at depths varying
from approximately 1.8 to 2.6 km (Ivanov et al, 1988).
Hydrocarbon pools and shows onshore arc
dominantly concentrated
in siliciclastic reservoir rocks of early and middle Miocene age.
Middle Miocene shales to 330-m thick (Yeliseev Formation) form a
regional
seal. These rocks are present over all the depression, and overlap
inner
and marginal basin highs and extend into the offshore basin.
These data indicate that a petroleum
system is probably
present in the offshore Anadyr basin beyond the Tuman uplift (Fig,
6).
The exploration concept is to extend the onshore petroleum system
offshore
using structural data. The offshore system is separated from the
onshore system by a structural barrier, the Tuman uplift. The age
of the Tuman uplift is important to determining whether there are one
or
two petroleum systems. If the uplift is young, and formed after
the
source rock became mature, then one system occurs. Whereas, if the
uplift
was formed before the source rock became mature, then there are two
independent
petroleum systems.
An analogy with uplifts north of the
onshore Anadyr basin
suggests that the Tuman uplift is an old structure formed before
deposition
of the middle Miocene shale; therefore, the map of the Anadyr basin
indicates
two petroleum systems (Fig. 6).
The areal extent of the offshore system
(shown on map)
is based on probable presence of mature source rocks: approximately
along
isopach 2.5 km and includes adjacent structural slopes. The
probable
stratigraphic extent of the petroleum system is from Eocene through
middle
Miocene strata. It may also include the top of the Upper Cretaceous
section
underlying the source rocks, although onshore, this section is devoid
of
good reservoir rocks. Exploration based on this play concept may
further reduce the spatial extent of the offshore system when more data
on reservoir rocks, maturity of source rocks, and quality of the
regional
seal become available.
These examples demonstrate that the
proven extent of the
petroleum system is shown by a line that circumscribes a mature source
rock and genetically related oil fields and significant shows. This map
is easily made in c provinces where most of the fields have been found
and a substantial amount of geological and geochemical data are
available.
However, even in these provinces, lateral extensions of the petroleum
system
can be expected based on mapping of the geometry of the rock body that
contains the oil and gas fields within the system. This extension
of the petroleum system can be the basis on which a play is predicted.
In moderately explored areas, such as in
the North Slope
of Alaska, mapping of the rocks that constitute the petroleum system is
the best way to understand the extent of the system. Here,
discovered
fields are clustered in a relatively small area so more geologic
information
may be needed to understand the entire extent of the system.
In unexplored frontier areas, mainly
structural and limited
stratigraphic data, coupled with comparative analysis of similar
provinces,
can be used to map the speculative petroleum system and to evaluate its
probable stratigraphic extent.
The map of the system in this latter
case presents the
maximum possible extent of the system, and commonly, this extent
decreases
as more data on distribution of mature source rocks, reservoir rocks,
and
seals become available. At all stages of exploration, a
comparison
between the proven lateral and stratigraphic extent of the system and
its
maximum possible extent indicates potential areas for further
exploration
efforts. Using the petroleum system concept, plays can be
developed
to find commercial quantities of petroleum in unexplored extensions of
the system.
|
Tectonics
of the Anadyr Basin
A. K. Dertev, O.I. Cuprunenko (vnigri) {from Russian}
Page 85
Anadyrsk basin is well expressed in relief encompassing the
territory
of Nizhneanadyr depression, and water area of Anadyr limb and same
embayment.
From the south, it is bounded by Koryak bowed system, from west the
Rarytkinskim
anticlinorium, from north - Chukotsk bow system and Zolotogorskim
anticlinorium,
from east and south (on water area) - Nunivakskim and Gangutskim
upheavals
(fig. 1).
The majority of explorers, following geological features of
the basin,
esteems it as a Cenezoic pattern overlapped on difficultly constructed
Mesozoic bow formations, being the foundation to sedimentary and
igneous-sedimentary
Cenozoic depositions [1, 4).
Per the last years, on this considered region, a lot of works
were published
[3, 5 - 8], generalizing materials on geological features and
oil-and-gas-bearing
capacity. The large bulk of geophysical works and deep drilling were
executed
by specialists of the Geological Survey and private concerns of USA
within
the limits of Navarin and Anadyr basins in Bering Sea [9, 10], have
allowed
on more authentic ground to compare a geological feature of the marine
part of the Anadyr basin to a part located on land. The truth, in work
[9]. The American explorers at interpretation of geophysical materials
on water area for confrontation used obsolete (out of date) works of
KMPV
held on land in from the 1960 years. However for the water area
of
Bering Sea the results of geophysical works introduce significant
improvement.
Besides the deductions of M. Marleu etc. [9] are confirmed by the
newest
results of works in basin of Navarin [10].
In difference from the mentioned large generalizings [3, 5 -
8], authors
have delivered before themselves narrower problem - on the newest
materials
drilling and seismic of works to update features of a constitution and
geologic progres of Anadyr basin on land
Figure 6 From Olmishek
Isopach map ot Retiary rocks of the Anadyr
basin
Supposed ofshore petroleum system
Cross-sedtion through onshore part of basin
Map after Dertec el al., 1986
Cross-section is after Marlow el al., with
changes according
to Krylov et al., 1988
Fig. 1. Structural - tectonic schema of Anadyr basin
1 - Boundary of Anadyr basin;
2 - Boundary of patterns second belt (1 - Kanchalano - Onemensky
bending
flexure, 2 - upheaval of Dionisija,
3 - Nizhneanadyr bending flexure,
4 - Tymninsko - Tumanskoe upheaval,
5 - Anadyr bending flexure) is east; z - isoheight of a base surface
Cenozoic depositions, km (on land - on the data seismic and boring, on
water area - on the data marine seismic (9, 10); 4 - outlines of the
floor
space, figured in a fig. 2 and 3
The land on a ground of constructing has enough of detailed
maps of
isopachs of the basic strata of a sedimentary jacket and to compare
them
to major stages of evolution in the sub marine basin.
Top page 86
The foundation for rather friable Mesozoic Cenozoic of
depositions basin
are difficulty dislocated Mesozoic and, probably, Paleozoic formations
observed on patterns, framing it. A heterogeneous nature of the
foundation
constitution is supposed. In the south Anadyrsk basin both on land, and
within the limits of water area the foundation are the bow formations
of
Jurassic-chalk rocks of Koryak bowed system immersed under rather
friable
Cenozoic deposition. On water area, dredged trench samples on upheavals
framing the basin from the south, the formations Jurassic and chalk age
are recovered.
The most ancient formations referred to fundamental rocks,
serve tufaceous
sandstones with tufa hardpan and tufite, and also overlying stratas
andesite-basalts,
bottom chalk, open by wells on East - lake region. On materials of
seismic
survey of MOGT these depositions are allocated on East-lake and
West-Lake
Upheavals, but are not found in bending flexures (Majnitsk etc.).
Apparently,
these horizons occur more deeply -- maximum depth of described by MOGT
for the given area (5 - 6 kms). On a survey profile of MTZ held through
Majnitsk a bending flexure in its mean part, are guessed friable
Cenozoic
and early chalk of deposition thickness up to 10 kms. Maximum depth of
a roof of the foundation on water area of 9 kms [9].
Top page 86 column 2
In north of Anadyr basin, both on land and on water area, the
foundation
is the igneous deposition chalk. They performed cartology from
aeromagnetic
to filming. On water area on northern deposit basin edge, debris of
igneous
formations, chalk and Neogene age are recovered.
In east part of the basin on water-area is probable Paleocene
age of
fundamental rocks. These assumptions are grounded on variation of
nature
seismic of record on profiles intersecting upheaval of Nunivak, and
also
on results from dredged trench samples, held by the American geologists
[9, 10].
The stratigraphic schema Cenozoic repeatedly varied. In the
given article,
we adhere to alternative proposed by D. I. Agapitovym etc. in 1982
(table).
Thus, the total thickness of a sedimentary stratum changes
from 5 up
to 13 kms. However, actual thickness of a jacket in many respects
depends
on an extent of fluid wash of this or that suite. By results of seismic
of studies and geologic data all stratum of a sedimentary jacket is
subdivided
into three, geologic of a geophysical complex divided by surfaces of an
unconformity.
Page 86-87
The bottom complex engages terrigenous deposition upper chalk (upper
Cenozoic - Danish), open by wells in southern and central parts of
Anadyr
basin (West-lake, East-lake and the tenacious area, well on Kose Geka
on
her western (well no SKV 8 on the Profiled area) and on southeast (SKV
?-6 in an estuary near Nygchekveem) Abramlenii and banks on igneous
Nizhnemelovyh
depositions with an unconformable dip. With seismic survey of MOGT and
?OB, these depositions are allocated only on East - Lake Upheaval in
the
median part of the basin (reflection horizon V), to western and
southern
beds. The bottom complex is poorly understood. These depositions,
apparently,
are advanced in the central, southern and southwest parts of a hollow
and
are absent in north. Wells penetrate more than 1000 meters of these
deposits.
On a survey profile of MTZ through a mean part of Majnitsk bending
flexure,
the presence of upper chalk deposition by thickening more than 3 kms is
supposed.
The mean complex engages igneous formations Tanjurerskoy suite
and terrigenous
estuary - Chirynajsk and Majnitsk suites and abundant on all territory,
edging away to the set of rules of large upheavals. Thickness of a
complex
and its structure are changeable. The igneous depositions of
Tanjurerskoy
suite are advanced only in north of Anadyr basin and to the south, edge
away. Their maximum thickness is marked off in Kanchalano-Onemensk
bending
flexure and, on the data of MOV reflection seismic, compounds more than
three kms. Skv # 19 drilled in a mean part of a bending flexure exposed
2041meters of these deposits. The terrigenous formations estuary-
Chirynajsk
and Majnitsk suites are advanced in the central and southern parts of
Anadyr
basin and edge away to north and east. The thickness of more than 2 kms
are observed on Echinsk upheaval in CKB #18 (fig. 2); their
magnification
on a southern deposit edge of Anadyr basin (Majnitsk bending flexure,
Chirynajsk
upheaval) is supposed. Seismic survey of MOV and MOGT is good are
traced
these depositions, in their top of oil horizon is allocated bearing
reflective
horizon III.
End page 87 top page 88
By seismic studies on water, all stratum sediment deposits
area executing
Anadyr basin is confidently subdivided into two complexes easily
enough.
Bottom, introducing rather monotonic, Akustvcheski "a transparent"
stratum,
and upper, described by significant lamination [9]. Comparing seismic
with
a cut-away view from a deep well on Kose Geka, it's established that
the
bottom complex marine deposition is introduced to terrigenous and
igneous
depositions of Paleogene and late chalk age (quaternary). Selected by
seismic
survey on water area the horizon {BETA} (9, 10) is well compared to
reflection
horizons III and IV on land, for example with a base surface mineral of
depositions. Thus, selected is on land and mean complexes are
compared
to lower complex on water area. Its thickness the same as and on land,
extremely variable and alternating from the first hundreds meters on
upheavals
up to 5 kms in zones of maximum buckling, being augmented for, account
of more ancient depositions.
The upper complex occurrences with granite wash on deposits --
middle
and bottom. It engages Miocene, Pliocene and quaternary deposit
and
is abundant everywhere in the basin. For depositions Neogene are
characteristic
multiple enough fluid-filled, acoustically rigid, reflecting
boundaries.
On the data of seismic survey both on land, and water area the upper
complex
beds on two, three-bed complexes. Horizon (on marine area [9, 10]) is
compared
on land to a reflection horizon I, dated to a base surface of upper
Miocene
(Ozerninsk suite), and is a boundary surface of top and bottom (upper
and
lower) bed complexes.
On land, three bed complexes of upper Miocene-Pliocene Echinsk - is
allocated
Page 88 continued
By seismic marine studies, area all stratums of sediments
(deposits)
performing in the Anadyr basin, is subdivided confidently enough into
two
complexes. At the bottom, introducing rather monotonic, Akustvcheski "a
transparent" stratum, and upper, described by significant lamination
[9].
On a ground of confrontation of seismic with a cut-away open with a
deep
well on Kose of Geka, is installed that the bottom complex on water
area
is introduced terrigenous and igneous depositions of Paleogene and late
chalk. Selected by seismic survey on water area the horizon ? (9, 10)
is
well compared to reflection horizons III and IV on land, for example
with
a base surface mineral of depositions. Thus, is selected on land
and mean complexes are compared to one lower marine complex its
thickness
the same as and on land, extremely changeable and various from the
first
hundreds of meters on upheavals up to 5 kms in zones of maximum
buckling,
being augmented for, accounted by more ancient depositions.
As a whole, the upper sedimentary complex is more sustained on
thickness,
than the base does, and reaches 4 kms on water area and 5 kms on land.
Thickness of the beds in the complexes is changeable. Bottom of the bed
complex (Sobol'kovskaya, Gagarinskaya and Avtatkul'skaya suites),
absent
in north of Anadyrsk basin, and on a large part of other territory it
thickens
200 - 300 m. Is more sustained on thickness, which underlay deep, and
reaches
4 kms on water area and 5 kms on land. Thickness bed complexes
changeable.
Bottom bed complexes (Sobol'kovskaya, Gagarinskaya and Avtatkul'skaya
of
suite) is absent in north of Anadyrsk basin, and on a large part of
other
territory its thickness 200 - 300 m. It is augmented more than 2,5 kms
in the south Majnitsk of a bending flexure and up to 1 km in Central.
Mean
bed complex (Eliseevsk and Ozerninsk suite) is observed everywhere (300
- 500 m's) Thickness is moderated on a southeast deposit edge. Under
Anadyr
bending flexure also are augmented up to 750 - 832 meters in its middle
part (East & Ozerninsk upheaval) and in the south Majnitsk of a
bending
flexure (fig. 3). Upper bed complexes (Aaleksandrovsk stratum and
Echinsk
suite) are advanced everywhere (500 - 600 m's). The maximum thickness's
are observed in Kanchalaio-Onemensk bending flexure and in the south
Majnitsk
of a bending flexure. In east part of Majnitsk of a bending flexure and
further to the south these depositions, apparently, are absent.
The modern basin outlines are traced up to Pliocene -
quaternary transient
shelves.
On depositions that are more ancient, its sizes are considerably
abbreviated
down to separation to more small-sized independently developing basins.
The pattern is anisometric (single-ended) - southern deposit edge
steep,
northern flat. In the plan basin has an oval form, extended in width
direction,
western part which one is located on land, and east - on water area of
Anadyr embayment. Tymninsko - Tumanskoe the crosscut (transverse)
upheaval
partitions basin on Nizhneanadyrsk bending flexure located in its
western
part, and Anadyrsk is east.
Patterns more small-sized have north western and northeast
direction
of strata. The folds focused, as a rule, in northeast direction, for
east
- predominantly in a northwest direction are characteristic for western
part of the basin. First report structure surrounding also are located
on continuation of large patterns of a frame (configuration), embedded
floor Mesozoic Cenozoic rather friable formations.
89
Fig. 3. The schema of isopachs weighted volumetrically- and top of
Nemiotsenovyh (Ozerninsk both Eliseevsk suite and top of Nemiotsenovyh,
Pliocene-quaternary of depositions (Echinsk suite and Aleksakdrov
stratum
- b) fig. 2
Top page 89 text
The upheaval of Dionisiya is a continuation of Zolotogorsk
anticlinorium.
Chirynajsk and Ozerninsk upheaval are located on submerged Tamvatnejsk
anticlinorium. Podgornensky and Majnitsk bending flexures are on
submergence
accordingly Velikorechensk and Kerkerveemsk sinclinoria frame, observed
on Jurassic-chalk depositions of the basin. The patterns of northwest
orientation
are not patterns of surrounding deposits; apparently, it is a younger
formation.
The following patterns of the second order are allocated:
Kanchalaio
- Onemensk bending flexure, upheaval. Dionisiya, Nizhneanadyrsk a
bending
flexure, Tymninsko - Tumanskoe upheaval, is east Anadyrsk bending
flexure.
Kanchalaio - Onemensk bending flexure is located in a
northwest part
of basin and is carved out from it by upheaval of Dionisiya. As
independent
pattern it existed only in Pliocene - quaternary time, in other time
served
northern decline of Anadyr basin. The deep well, drilled in northern
part
of a bending flexure, has opened Pliocene - quaternary of deposition
(810
m), middle Eocene (455 m) and igneous Paleocene - Eocene formation
(2041
m). On the geophysical data it is possible to guess, that the thickness
of the Cenozoic shelf here do not exceed 3.5 - 4 kms, from them Neogene
no more than 2 kms.
The upheaval of Dionisiya has northeast direction of strata
and is on
western submergence of Zolotogorsk anticlinoria under a stratum of
Neogene
deposition. It separates Kanchalaio -Nemensk bending flexure from
Nizhneanadyr,
amplitude about 4 kms. At the arch the thickness Paleogene depositions
are considerably abbreviated and edge away lower and middle Eocene.
Upper
Eocene and Pliocene-quaternary formation are absent in east part and
reach
800 - 900 m in western, mostly embedded (see fig. 3).
End page 89
In Nizhneanadyr bending flexure, the dominant inherited
patterns are
dull.
Top page 90
Nizhneanadyr bending flexure is the largest pattern of Anadyr
basin
(on land), in its limits the upheavals of Chirynajsk, Ust'-Chirynajsk,
Ozerninsk, Povorotno - Aleksandrovsk, and multiple and bending flexures
are observed: Podgornensky, Velikorechensk, Central, Protochnaya,
Majvitsky,
Oleninshaya, and Limansk. Nizhneanadyrsk a bending flexure extends in a
northeast direction on a long fulcrum on 300 kms and on short - on 25 -
110 kms. On western and east deposit edge is located multiple
depositions
with depths submergence of up to 5-6 kms. Its mean part is raised,
section
of Nizhneanadyrsk bending flexure on two parts: western and east. The
depths
of immersion of Cenozoic depositions for positive patterns of a mean
part
of a bending flexure, on the data of boring and geophysical studies,
compound
1.3 - 2.5 kms. Fundamental rocks drilled by boring only on Lake
Upheaval
(East-Lake Pattern) on depths 1326 - 1670 m.
On southern and western to deposit edge the bending flexure is
carved
out from patterns of a frame by zones of explosive dislocating with
amplitudes
of separate disturbances from several tens up to hundreds meters. On a
southern deposit edge of a bending flexure Jurassic-chalk and Paleogene
formation frame are pulled, apparently, on friable Cenozoic
deposition.
Tymninsko - Tumanskoe upheaval has a sub-meridian direction of
strata
and partitions in the Anadyr basin on two parts. On a long fulcrum
length
it more than 150 kms, on short 20 - 60 kms, amplitude on a base surface
of Cenozoic depositions 2.5 - 4 kms, occurrence depth of these
formations
of 1-1.5 kms. Here are advanced Pliocene - Quaternary and mid to upper
Eocene formations. In the set of rules of upheaval are absent upper
Eocene
and terrigenous Eocene to Oligocene formation, to which a cut-away open
SKV convincingly testified by well K-8. The same well has opened
igneous
depositions Paleocene Eocene (Tanjurersk suite). In cut-away open with
wells a slope of upheaval - (P-12, P-23), thickness of these
depositions
having augmented
On a long fulcrum length is more than 150 kms, on short 20 - 60 kms,
amplitude on a base surface of Cenozoic depositions 2.5 - 4 kms,
occurrence
depth of these formations of 11.5 kms. Three basic developments here
Pliocene-quaternary
and middle & upper Eocene formations. The same well has opened
igneous
overturned Paleocene-Eocene (Tanjurersk suite).
The same wells have opened terrigenous depositions upper
chalk, missing
on the set of rules.
Here Cenozoic formation occurrence on early chalk fundamental
rocks
is at the surface. In water area trench dredge were brought up granite
early of age. Tumansk upheaval was generated in late chalk. In
Paleogene
and early Eocene time it monitored deposit accumulation in Anadyr
basin,
that is precisely visible on a pinching out of a mean complex of
depositions
and part upper in Nizhneanadyr bending flexure as approaching
Tymninsko-Tumansk
upheaval.
Nizhneanadyr bending flexure bedding in the east part of the
basin almost
wholly is within the limits of water area. It has the sizes 200 X 225
kms,
isometric the form and skewed constitution. Optimum embedded parts
situated
on southern deposit edge. Northern flat complicated by patterns width
of
a direction of strata, southern steep.
On the data of a gravity exploration [2] and marine seismic,
the bending
flexure is complicated by explosive disturbances by amplitudes up to
several
hundreds meters on a southern deposit edge and zone of explosive
disturbances
on the basis northern. Maximum thickness of Neogene formations up to 3
kms, Paleogene - up to 1 - 2 kms and Mesozoic-Paleozoic - up to 5
kms.
Thus, the former submissions about existence of large Anadyr
basin from
late chalk bottom are not confirmed. The modern outlines of the
basin
will master those for depositions of Pliocene -quaternary time. On more
ancient formations of Tymninsko - Tumanskoe the crosscut (transverse)
upheaval
basin partitions on two bending flexures (Nizhneanadyr and eastern
Nizhneanadyr),
developing independently in Paleogene and early Eocene time. In their
constitution
the complex combination fold - block of members of the various order is
observed, among which one on genesis stand apart inherited and is new
formed
positive and below zero structure.
Page 91
AGENDA of the LITERATURE
1. Azaputov D. I., Ivamov I. I. A history of tectonic
progressing of
Penzhinsk-Anadyr of area in late Mesozoic and Cenozoic. Geotectonics.
1969,
no. 1, p. 68- 82.
2. Willow of m. L., Ermakov. In. Tectonic impact area of a
northwest
part of shelf of Bering sea and adherent coastlines - Geotectonic,
1976,
no. 2, p. 101 - 110.
3. Geology of Bering Sea and its continental frame / under
edit. B.
X. Egiazarova. L.: mineral resources, 1985.
4. Dranovsky YA. no., Berson G. L. Tektonics the schema of a
northwest
part of Tihookeansk bow belt.- Geology and geophysics, 1969, no. 3,
with.
41-47.
5. Ivaiov V. V. Sedimentary basins northeast Asia. M.:
Science,
1985.
6. New data on outlooks oil of a presence of gas of Northeast
USSR.
/ D I. Agapntov, Ju. And. Kosygin, Ju. V. Motovilov etc. - Geology oil
and gas, 1983, M 7, with. 1 - 6.
7. Sketch of tectonics of Koryak upland /under edit. Ju. M.
Pushcharovskogo,
S. M. Til'mana. M.: a science, 1982.
8. Tjutrun I. I. Dunichev V. M. Tectonics and
oil-and-gas-bearing capacity
of a northwest part of Tihookeanskogo zone. M.: mineral resources,
1985.
9 Marlow M. Cooper A. Childs U. Tectonic evolution on gulf of
Anadyr
and Formation ?f Anadyr and Navarin Basins. Bull. AAPG. l983, vol. 67,
N 4, p. 646-665.
10. Steffy D., Turner P., Martin A., Flett T. Evolution
and Petroleum
Geology of the Navarin basin, Bering Sea, Alaska. Oil and Gas. J.,
1985,
vol. 83, N 31, p. 116 - 119, 122 - 124.
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The Cretaceous OCVB
stretches along the southeastern margin of Mesozoic
Verkhoyansk-Chukotka tectonic province and is sharply discordant to its
structural trends (fig. 1). Volcanic rocks are undeformed and overlie
Verkhoyansk-Chukotka Mesozoic structures with angular unconformity
(e.g., Zonenshain et al., 1990; Sengцr and Natal’in 1996).
Compositionally, volcanics vary from basalts to rhyolites; intermediate
and felsic rocks predominate (Kotlyar et al. 1981). In regional
geodynamic evolution, volcanism postdated accretion of the Okhotsk
block, Kolyma-Omolon Superterrane, and Chukotka terrane to the
Verkhoyansk passive margin of the Siberian craton (fig. 1). This
sequence of collisions terminated earlier island arc volcanism, caused
deformations and emplacement of granitoids, and led to formation of
composite Verkhoyansk-Chukotka orogen (Parfenov and Natal'in 1985,
1986; Parfenov 1991, Layer et al. 2001). Subaerial, chiefly explosive
volcanism of the OCVB occurred afterwards and was related to northward
subduction of the Kula oceanic plate under the newly assembled tectonic
collage (e.g., Parfenov and Natal'in 1986; Zonenshain 1990; Zonenshain
and Kuz'min, 1992). This Andean-style volcanism ended when the
Verkhoyansk–Chukotka collided with the Okhotomorsk block, and
subduction zone shifted eastward (e.g., Parfenov and Natal’in 1986). 