ANADYR BASIN
ANADYR BASIN
P 64
The basin is connected to the same superimposed
depression,
which one bridges complex zone of an articulation of flank decay of
Anadyr
- Koryak of system Cenozoic with junction by patterns of Chukotsky
Mesozoic
and western protrusion Chukotsky - Stjuardsk block. Besides, here are
stretched
chalk Willingly Chukotsky and Paleogene Anadyr - Bristol'sky
vulcanology
belt.
Two zones are allocated in the common basin
plan. In north
and northeast, the complex of sedimentary implementation is introduced
only young (N-Q) coarse deposits thickness up to 2 - 2,5 kms, which
bedding
is direct on Eocene- effusives bridging. In turn more ancient,
miscellaneous
formation genesis and structure occurs in the folded basement. These
areas
differ by poorly contrasting tectonics, flat dip of strata,
co-sedimentation
type of local upheavals. At southern edge of this zone under
Paleocene-Eocene
effusive the marine terrigenous and continental carbonic formations
upper
chalk, forming a buried floor complex of implementation are laid out.
The leases of basin, approximate to its
southern and southwest
frame, differ greatly. Up to 3 - 5 kms thick depositions of
Neogene-Quaternary
and presence under them essentially of argillaceous and
silty-argillaceous
upper Eocene - Oligocene formations (up to three kms). Early Paleogene
volcanics here are abbreviated in thickness and are replaced by
terrigenous
formations.
Below at a cut-away of a buried floor of
implementation
there are terrigenous strata and - Cenozoic tufa siltstone depositions.
In these areas, young diastrophic movements with horizontal compounding
were brightly exhibited. That caused formation overlap faults and
thrusting,
along which the narrow highly peaked anticlines frequently complicated
by the phenomena of current argillaceous mass, and disconnected
detachment
fault are laid out.
In limits most known Cenozoic part of a
cut-away of basin
from below following suites and strata upslope stand apart:
Ust' - Chirynajsk (P3/2 >) -
sandy-argillaceous;
Majnitsk (P3) with three under suites (bottom,
argillaceous,
middle, siltstone, and upper, sandy - siltstone); Sobol'kovsk (N1/1) -
predominantly tufa - sandstone;
Gagarinsk (N1/1), Avtatkul'sk (N1/1-2), Eliseevsk
(N2/1),
Ozerninsk (N2/1-3), Echinsk (N3/1-N2) and Aleksandrovsk (N2-Q), differ
among themselves on nature of an interlayering dominating type of
terrigenous
formations, and enriched hydrocarbon and carbonaceous formations [45,
47].
Anadyr basin is well understood in the regard
of pattern
of catagenesis in this region [47, 65, 158]. Tectonic discontinuity of
basin, thermal properties of formations, availability in a cut-away of
truncations, fluid washes and unconformities, progressing of explosive
disturbances, transformation a calorific area and forms by high heat
generation.
All these factors attach a catagenic complex areal nature (fig. 29).
Thus,
frequently prove, that the same litho-stratigraphic divisions in
different
areas are resized rather variously, quite often even on the neighbor
leases,
where they are approximately on equal depths. All this results that the
separate suites and strata are characterized by a wide range of
catagenic
transformations [47].
Standard chemical - bitumen examination the
performance
of clay materials of Anadyr basin results in fig. 30. It is necessary
at
once to point out, that the contents in CK bituminous reductants and
their
structure on the given generalized schedules mirror not only feature of
original composition ??, but also the non-uniform conditions
catagenesis,
in which various lithologic-stratigraphic division. Lower tufaceous
formation,
opened up by a well in the central part of the basin, 1.2 % contain a
(beta/XB)
in amount 1.1 -1.2%, but are characterized by minute concentrations XB
and low significance of bitumen coefficient (p), As formations of this
complex bedding in optimum from outlook oil generation to zone
catagenesis
(MK3), the low contents in them dissoluble is possible to believe, that
reductants is connected to features of structure CK and with
influencing
of tufogennogo such as mineral environment.
64
65
text fig 29
Figure 29.
Pattern catagenesis of a field Anadyr of basin on
a base
surface Neogene of depositions
1 - Boundary of basin and its frame;
2 - Well and significance of magnitudes (OCB=OSV)
in
terms of R\3 base on Neogene surface;
3 - Line of equal significance (OCB=OSV)
(izoresplendy);
4 - Areas with significance (OCB=OSV) =
7.0-8.00;
6 - Tectonic disturbances influencing isometric
figure
of (a - thrust, overlap faults, b - sea disposals)
Upper deposition of a buried floor of
implementation of
basin are enriched CK in some smaller extent (see fig. 30). The extent
of their catagenesis transformation varies in a range of gradation
MK\2-MK\4
(concluding V. N. Boroiaeva, A.A. Koshunova, A.I. Utkinoj). However,
for
a facies type CK is essentially humic arkose, the contents XB and
magnitude
beta\XB here nevertheless is higher, than in underlying a complex.
Paleogene depositions abundant only in a
southern part
basin are inflected in a wide range of catagenesis (PK/2-MK/2) [27, 47,
153), but in the basic part deposition in conditions of zone of mezo-
catagenesis.
Eocene-Oligocene deposition in structure of Ust'- Chirynajsk and
Majnitsk
suites are characterized contouring inclusive CK. Within the limits of
this complex of concentration C/nk in siltstone formations grow from
0.54
% in mean - upper under suites of Majnitsk of suite up to 0,79 % in
under
majestic and 0.77 % in Ust-Chirynajsk. In the plan of the contents Cnk
(NOV) are augmented from less 0.5 up to more than 0.7 % in a southwest
direction (fig. 31). On the data of element analysis of the allocated
concentrate
CK (IS NEW) and pyrolysed (?/? at = 1.0; hydrogen and oxygen subscripts
150 mg ??/g? and 130 mg ??2/??/nk accordingly).
The resulting data are referred to CK,
converted not more
strongly than gradation PK/3.
65
68
Fig. 31. The allocation schem? of CK with
(B %)
in Neogene and Paleogene siltstone depositions of Anadyr Basin.
1 - Boundary of basin its frame: 2 - point
assay; 3 -
line of the equal contents C/HK %
68
CK are referred to blended sapropel -humic to
a type,
or III to a type on classification of the French Petroleum Institute
[170].
In balance of dissoluble reductants CK the
equal proportion
neutral (XB) and acidic (DSBB) bitumen or dominance maiden of them
(Ust'
- Chirynajsk stratum) takes place approximately; the IK-spectra XB
confirm
commingle sapropel -humic a nature SK - rich-dark occluding in field
850
- 700 cm\-1 in a combination to a bar mean intensities at 1600 cm\-1
and
with strong occluding in field 1720 - 1700 cm\-1. The extent
re-establish
XB (back is proportional contents GZ), and contents in XB YB C15 + here
optimum in all cut-away. Extent and polymodality of the schedules of
allocation
standard chemical carbon bitumen index of clay materials Paleogene of
age
testify to active processes reallocating in them mobile of reductants.
69
The total contents YB With, in formations
Majnitsk suite
vary 3 from less 0.01 to 0.09 of %, compounding in recalculation on
C/nk
0.5 up to 9.2 %. The proportion of concentrations of factions C15?/C15+
changes within the limits of 0.2 - 0.54, thus inside of factions Page 70
?12, more lighter dominate ?6 - ?10 (tab. 2) -
ratio
?6-?10/?11-C15- is inflected within the limits of 0.7 - 56.3, averaging
7.6.
The formations Neogene of a complex, in the
majority beds
in zone of proto-catagenesis, have rather non-uniform allocation CK.
According
to magnification saturated. Upslope on a cut-away ascending dispersions
of the contents Snk from 0.18-2.53 % in Gagarin and Sobol'kovsk suites
to 1.69 - 7.87 % in Aleksandrovsk is fixed. Enriched Snk of silty-clay
materials Neogene grows from central to western and southern inshore to
zones (see fig. 31).
Owing to higher contents CK Neogene of deposition
in
the greater extent are enriched and bitumen with reductants, however
extent
bitumen CK in recalculation on Snk here is lower. Among bitumen
dominates
DSBB. In comparison with Eocene-Oligocene by a complex XB more oxidize
also, contain less YB (see fig. 30). The IK-spectra point, that in
pattern
XB the basic role is played by chained aliphatic pieces. The stated
materials
in a combination to the data of element structure HOB (H/C at- 0.8 -
0.9)
allows to speak about predominantly continental genesis CK Neogene of a
complex.
The contents YB C1+ in formations Neogene is
inflected
from 0.003 up to 0.13 % and compounds in recalculation on Cnk 1 1 4.6
%.
Among YB C1+ considerably dominate C15+, (the ratio of factions C15
/C15+,
as a rule, does not exceed 0.27), inside of lighter YB C1+ the
dominance
more lighter YB C6-C10 (ratio C6-C10/C11-C15 on the average equally
13.5)
is hardly expressed.
Contrast enough distinctions of
physical-genetic types
CK Neogene and Paleogene complexes of depositions are exhibited at
comparison
of the data on allocation normal alkanes and regular isopentane C15 +.
On catagenesis a level (PK3) of significance of coefficient of oddness
normal alkanes CPI in formations Neogene compound 3.3 - 6.7, whereas
for
Paleogene of depositions of significance CPI do not exceed 2.9. The
ratio
Pr/n-C17 is inflected from 4.1 up to 13.8 in formations of Neogene age
and from 1.6 up to 3.7 in Paleogene formations; the magnitudes of
coefficient
Pr/f compound 4.2 - 8.3 and 1.3 - 4.1 accordingly.
For formations of both complexes converted
within the
limits of gradation MK1, - MK3 learning individual structure
low-boiling
YB With, (tab. 3) was implemented.
As it is visible, the distinctions of types CK
are exhibited
in means of indexes of a faction YB C7 clearly.
3 Summary contents in ?? C15+ here in all
cut-away.
p.70
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