Earthquakes epicenters in Arctic
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Category: geographygeography

Geological and tectonic evolution of the Arctic Ocean

1.

Geological and tectonic evolution of the
Arctic Ocean
Lectures 2 - 3
Course: Particularities and Features
of Cold Region Geology
by
Alexey A. Krylov,
Institute of Earth Sciences, St. Petersburg State University

2.

Northwind Ridge
TOPOGRAPHY OF THE ARCTIC OCEAN
Podvodnikov
Basin

3. Earthquakes epicenters in Arctic

4.

International Chronosrtatigraphic Chart

5.

What existed prior the Arctic Ocean?
Breakup of Rodinia — the
Grenvillian supercontinent
that formed ~1 Ga.
Arctida structures
within Rodinia:
Svalbard, the Kara block,
the Greenland–
Ellesmere, Alaska–
Chukchi and New
Siberian blocks.
Continental masses
Continental blocks of Arctida
Oceanic basins
Arctida located between the
Canadian margin of Laurentia,
the southwestern margin of
Siberia and the northeastern
margin of Baltica.

6.

What existed prior the Arctic Ocean?
The breakup of the
Rodinia was accompanied
by the destruction of the
margins of plates into
independent terranes,
microcontinents, small and
average plates:
- New Siberian block
- the Kara plate
- Svalbard plates
Active continental margin
located close to the Timan–
Ural margin of Baltica
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

7.

What existed prior the Arctic Ocean?
Svalbard plate collision formation of the Timan–
Pechora orogen, which
sutured the plate with the
timanian margin of Baltica.
The SW margin of Siberia
was in a setting of active
continental margin of
pacific type.
The birth of the Iapetus
Ocean on the margins of
Laurentia and Baltica.
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

8.

What existed prior the Arctic Ocean?
Iapetus was
characterized by an active
spreading regime between
Laurentia and Baltica.
Continental crust
breakup along the eastern
(modern coordinates)
margin of Baltica with the
formation of the oceanic
floor of the Ural
paleoocean
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

9.

What existed prior the Arctic Ocean?
The end of the
Ordovician was marked
by the beginning of the
closure of the Iapetus
oceanic space.
Active subduction
processes manifested
everywhere on its
continental margins
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

10.

What existed prior the Arctic Ocean?
The Silurian–Devonian
boundary: closure of the
Iapetus Ocean.
The collisional event
between Laurentia and
Baltica and their unification
into Laurussia.
The Kara microcontinent
already was located directly
near the Taimyr margin of
Siberia.
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

11.

What existed prior the Arctic Ocean?
The blocks of Arctida
composed a continental
bridge between Siberia
and Laurussia, joining
the structures of the
supercontinent.
Rheic Ocean - the
oceanic space between
Laurentia and the
African margin of
Gondwana, was in active
closure
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

12.

What existed prior the Arctic Ocean?
The global tectonic
regime did not undergo any
significant alterations in the
Early Carboniferous.
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

13.

What existed prior the Arctic Ocean?
The Rheic ocean disappeared….
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

14.

What existed prior the Arctic Ocean?
The appearance of Pangea…
Arctida….
Continental masses
Inferred position of spreading zones
Continental blocks of Arctida
Oceanic basins
Active continental margins

15.

GEOLOGICAL DATA COLLECTED UP TO DATE
PS87/106
Eocene
Campanian
?
Maastrichtian
PS87/106
Maastrichtian
Only 3 short cores (Fl 533, CESAR-6, FL 437) on
the Alpha Ridge, and one ACEX-borehole on the
Lomonosov Ridge recovered the Mezozoic (Late
Cretaceous) sediments. To characterize the
Mesozoic sedimentation in the Amerasian Basin,
we have only this geological material.

16.

GEOLOGICAL DATA COLLECTED UP TO DATE
ACEX – Arctic Coring EXpedition – 2004 – IODP302
IODP 302 Site
Nansen
Basin
Amundsen
Basin

17.

18.

GEOLOGICAL DATA COLLECTED UP TO DATE
Position of the ACEX-boreholes on the Lomonosov Ridge
drilled along the seismic profile AWI-91090.

19.

GEOLOGICAL DATA COLLECTED UP TO DATE
1
2A
3A
4A
4B
4C
ALL

20.

GEOLOGICAL DATA COLLECTED UP TO DATE
TRACKS OF THE VESSELS

21.

ORIGIN OF THE AMERASIAN BASIN
Rotational model of
the Amerasian Basin
Formation
Late Jurassic – Early
Cretaceous (~150-140 Ma):
breaking off the Chukotka –
Arctic Alaska microplate
from the Canadian Arctic
Archipelago.
1 – position of idealized
boundaries of modern
lithospheric plates;
2 – boundary of the
Chukchi – Arctic Alaska
microplate;
3 – idealized trajectory of
the Chukchi – Arctic Alaska
microplate during the
opening of the Canada
Basin

22.

ORIGIN OF THE AMERASIAN BASIN
Model of upper mantle return flow: the reason for the extension of the
Makarov-Podvodnikov Basin and separation of the Alpha Mendeleev Ridge
from the “paleo-Barents-Kara Sea” margin.
90 Ma
Lobkovsky et al., 2014
P-wave tomogram

23.

ORIGIN OF THE AMERASIAN BASIN
AlphaMendeleev
Ridge
AlphaMendeleev
Ridge
Canada
Basin
Canada
Basin
MakarovPodvodnikov
Basin
no MakarovPodvodnikov
Basin
The process of detachment and subsequent movement of
the Alpha-Mendeleev Ridge away from the Barents Sea
margin, accompanied by rift extension of the Makarov and
Podvodnikov basins, occurred in the interval of 110-60 Ma.
after Kazmin et al., 2015, Doklady Earth Sciences

24.

ORIGIN OF THE AMERASIAN BASIN
AlphaMendeleev
Ridge
Canada
Basin
MakarovPodvodnikov
Basin
“Lomonosov
Ridge”
The initial area of the Canada Basin 110 Ma ago was equal to its
present area. Later, subsequent formation of structures of the
Amerasian Basin, including the Alpha-Mendeleev Ridge and
Makarov and Podvodnikov basins, was caused by continuous
movement of the subduction zone, located on the Alaska-Chukchi
margin, toward the Pacific.

25.

AMERASIAN BASIN: MESOZOIC SEDIMENTS
Fl-437, CESAR-6
Clark, 1988
Yellowish laminated siliceous ooze rich in diatoms,
ebrideans, silicoflagellates, and archeomonads.
OC < 1%.
Age: Campanian for Fl-437 (Dell’Agnese&Clark, 1994);
Campanian-Maastrichtian for CESAR-6, depending on whether
diatoms, silicoflagellates or palinomorphs are taken as the prime
biostratographic indicator.
Warm Arctic Ocean with strong seasonality and high paleoproductivity.

26.

AMERASIAN BASIN: MESOZOIC SEDIMENTS
Fl-533
Peridinoid and
gonyaulocoid
cysts –
dinoflagellate
Age: early Maastrichtian (Fifth&Clark, 1998)
Immature, mixed terrigenous-marine type of organic matter.
Origin: anoxic condition in an isolated local basin? A depositional
environment under an oceanic water mass exibiting an oxygen
minimum?

27.

AMERASIAN BASIN: MESOZOIC TEMPERATURES
Jenkyns et al., 2004

28.

ARCTIC OCEAN: FORMATION OF THE EURASIAN BASIN
55 Ma
Lobkovsky et al., 2014
Detachment of “the second zone of Cenozoic tectonic blocks” (a linear
Lomonosov Basins Ridge) from the Barents Sea margin and formation
of the Eurasian Basin.

29.

PALEOGENE – GREENHOUSE
Stein R., GRL, 2006
Sluijs et al., Nature Geo, 2009
Thermal events during Paleogene coincided with intervals where Corg depleted
in 13C isotope. Reason: gas hydrate destabilization? (CH4 depleted in 13C)

30.

PALEOCENE–EOCENE THERMAL MAXIMUM (PETM)
Late Paleocene – Early Eocene
PETM
Sluijs et al., 2006
TEX86 temperatures in the Central Arctic during (and
around) PETM.

31.

AZOLLA FRESHWATER EVENT – MIDDLE EOCENE
0
1
2
3
4
5
6, TOC%

32.

AZOLLA FRESHWATER EVENT – MIDDLE EOCENE
Age of Azolla event
in ACEX core was
determined by
calibration with welldated ODP hole 913B
= 48.3 Myr.

33.

PALEOGENE: ISOLATION OF THE ARCTIC OCEAN
50 Ma
Closing of the Turgai Strait. The Arctic Ocean become isolated.
40 Ma
Barron et al., 2015

34.

BIOSILICA DEPOSITS – MIDDLE EOCENE
Biosilica sediments in the Lithological Units 2 and 1/6 of the ACEX.

35.

BIOSILICA DEPOSITS – MIDDLE EOCENE

36.

BIOSILICA DEPOSITS – MIDDLE EOCENE
1/4
2
Paleogene
1/6
1/4
Marine anoxic
environments is
needed
1/6
Biosilica
1/3
Neogene
1/3
Sandy silty clay
Pyrite in heavy fraction (size 0.05-0.1 mm) from ACEX sediments
2

37.

BIOSILICA DEPOSITS – MIDDLE EOCENE
Environmental model of the central Arctic at the Lomonosov
Ridge during the early middle Eocene, after the Azolla phase.

38.

Neogene
Paleogene
Silty Clay
Age model
“A” includes
26 Ma hiatus
at ~200 m
below ocean
floor.
Biosilicious
ooze
Silty clay
PROBLEM OF THE MID-CENOZOIC HIATUS
Mesozoic

39.

SUBSIDENCE OF THE LOMONOSOV RIDGE
Moore et al., 2006.
The regular subsidence of the Lomonosov Ridge by cooling and
weighting of the lithosphere with time: a consequence from plate
tectonics.
Right side: lithological units from U4 (oldest) to U1.2 (youngest)

40.

PROBLEM OF THE MID-CENOZOIC HIATUS
Evidence against a long hiatus: the absence of faults and tectonic
deformations in the sediments above the intended hiatus on the Lomonosov
Ridge.

41.

ПРОБЛЕМА
PROBLEMСРЕДНЕ-КАЙНОЗОЙСКОГО
OF THE MID-CENOZOIC HIATUS
ПЕРЕРЫВА
The values of
osmium isotopes in
the sediments
accumulated "before
hiatus" is different
from those in the
World Oceans, which
confirms the isolation
of the Arctic.
The values of
osmium isotopes also
indicate the absence
of a long hiatus (less
than 400 thousand
years, not 26 million!).
Poirier, Hillaire-Marcel, GRL, 2011

42.

ПРОБЛЕМА
PROBLEMСРЕДНЕ-КАЙНОЗОЙСКОГО
OF THE MID-CENOZOIC HIATUS
ПЕРЕРЫВА
If " age model B" is true, then the sedimentary section contains
Oligocene deposits.

43.

ПРОБЛЕМА
PROBLEMСРЕДНЕ-КАЙНОЗОЙСКОГО
OF THE MID-CENOZOIC HIATUS
ПЕРЕРЫВА
Isolation: 49÷36.6 Ма
Hegewald, Jokat, 2013
Fram Strait open ~17.5 Ma [Jakobsson et al., 2007]
Isolation of the Arctic Ocean till this time [O’Regan et al., 2008]
New idea: isolation from ~49 Ma (Turgai Strait closing) till 36.2 Ma [Chernykh,
Krylov, 2015].
Oligocene regression (ruppelian/chattian) can be observed in the sediments of
the Central Arctic Ocean

44.

ПРОБЛЕМА
PROBLEMСРЕДНЕ-КАЙНОЗОЙСКОГО
OF THE MID-CENOZOIC HIATUS
ПЕРЕРЫВА
MODEL
Dropping of the sea level due to spreading in the Eurasian
Basin during isolation of the Arctic Ocean
Sea level
Time
LR
Falling sea levels could lead to erosion of sediments on the
Lomonosov Ridge. Most likely this erosion does not exceed 400
Kyr.

45.

ONSET OF SEASONAL AND PERRENIAL ICE
The assumption about the time of sea-ice occurrence in the
Central Arctic prior ACEX drilling.
Jenkuns et al., 2004, Nature

46.

ONSET OF SEASONAL AND PERRENIAL ICE
Stickley et al., 2009, Nature
St. John, 2008,
Paleoceanography
Onset of the ice in Central Arctic: appearance of the coarse material (IRD)
and ice-dependent diatoms.

47.

ONSET OF SEASONAL AND PERRENIAL ICE
0
50
100
Хорошо
окатанные
Плохо
окатанные
250
Полуокатанные
200
Неокатанные
cmbsf
150
First300
seasonal ice appeared in the Central Arctic in the Middle
350
Eocene
400
1/1
1/2
1/3
1/4
1/5
1/6
2
3
4
450
0
0.2
0.4
0.6
Wadell coefficients
0.8
1
First appearance of the stones at the 247 mbsf, in LU 2 (biosilica deposits) =
46 Ma (or at 43 Ma using stratigraphy “without hiatus”)
Amount of fraction 150-250 μm increased at 46.3 Ma. [St. John, 2008].
Sea-ice-related diatoms Synedropsis spp. found ~47 Ma [Stickley et al.,
2009].

48.

ONSET OF SEASONAL AND PERRENIAL ICE
EOCENE
Major
warming
event
Major
cooling
events
Major
increases in
sea-ice
cover
Alkenone-based sea surface temperatues (SSToC), abundance of icerafted debris (IRD). SST data do not support perennial sea ice cover
during the studied time interval.
- occurrence of large-sized single dropstones

49.

ONSET OF SEASONAL AND PERRENIAL ICE
Sources of the terrigenous material and ice drift systems
Px – Clinopyroxene;
Hbl – Hornblende;
Sid – Siderite;
P – Pyrite;
D – Dolomite;
Chl – Chloritoid;
I – illite;
S – smectite;
K – kaolinite;
C - chlorite
Numbers:
time during
which the
ice
reaches
the Fram
Strait

50.

Paleogene
13Ma
Neogene
ONSET OF SEASONAL AND PERRENIAL ICE
Distribution of the heavy minerals along the ACEX borehole. Сhange of the
mineral associations occurred at ~ 13Ma.

51.

ONSET OF SEASONAL AND PERRENIAL ICE
mbsf
0
100
200
Cpx/
Hbl
Flint, Qu sandstone,
Limestone, Shale
Sandstone - 2
Basalt - 2
Qu sandstone - 3
Sandstone - 9
Shale - 7
Qu gravelstone - 3
Dolerite - 1
Quartz sandstone - 1
Quartzite - 2
Qu sandstone - 3
Quartzite
Qu sandstone
Quartzite
Qu sandstone
300
1/2
1/3
Within LUs 1/3 – 1/1 also
appear argillites (shales),
schists, flints, limestone (1
sample) and basalts (2
samples).
1/4
1/6
2
Large-sized stones in LUs
2, 1/6, 1/5 и 1/4 represented by
quartz sandstones, quartz
siltstones and quartzites.
Сhange of rocks assemblages found at the level of
159 m, which practically coincides with the change of
associations of heavy minerals in LU 1/3.

52.

ONSET OF SEASONAL AND PERRENIAL ICE
The first pack ice in the central Arctic have
appeared in the Middle Miocene (about 13 Ma).
From that moment, the “paleo-trans-polar" ice
drift system began to act.

53.

QUATERNARY SEDIMENTATION IN THE ARCTIC
Three scenarios of sedimentation
1) Glaciation.
The ocean is covered with pack ice. Lack of benthic and
planktonic organisms. Sedimentation rates are minimal.
2) Deglaciation.
Degradation of glaciers. The appearance of a large number of
icebergs. The transfer of coarse material. Pack ice and icebergs
are melting rapidly. The appearance of benthic and planktonic
organisms. High rates of sedimentation.
3) Interglacial.
Modern Arctic Ocean. The predominance of clay and silt
material. The abundance of benthic and planktonic organisms.
The intermediate sedimentation rates.

54.

QUATERNARY SEDIMENTATION IN THE ARCTIC
Glaciation
Pack ice
Low sedimentation rates or hiatus

55.

QUATERNARY SEDIMENTATION IN THE ARCTIC
Pelagic
sedimentation
Deglaciation
Seasonal
ice
icebergs
Pack ice
IRD
IRD
IRD
Start of bioproductivity
High sedimentation rates
IRD – ice-rafted debris

56.

QUATERNARY SEDIMENTATION IN THE ARCTIC
Interglacial
Pelagic
sedimentation
Seasonal ice
Pack ice
IRD
IRD
High bioproductivity
High or intermediate
sedimentation rates

57.

Contribution of glaciomarine material to pelagic sediments

58.

Contribution of glaciomarine material to pelagic sediments

59.

Contribution of glaciomarine material to pelagic sediments

60.

Contribution of glaciomarine material to pelagic sediments

61.

Contribution of glaciomarine material to pelagic sediments

62.

Contribution of glaciomarine material to pelagic sediments
Ice-Rafted Debris.
A sample of ice-rafted debris (IRD), or sediment.
The individual grains of microscopic-size debris are counted to
obtain the percentage of grains in a gram of sediment.
The percentage varies when ice-rafting increases or decreases,
or if the number of organisms increase or decrease.
Rounded quartz grains from
ice-rafted debris
An angular quartz grain from
ice-rafted sediment

63.

Contribution of glaciomarine material to pelagic sediments
Quantitative studies of glaciomarine-influenced sediments
from the Nordic seas have shown that their IRD content can
be correlated to the onshore glacial history of the
Fennoscandian and the Svalbard/Barents Sea ice sheets.
Large amounts of IRD
in the sediments coincide
with the extension of the
ice sheets over the
continental shelves.

64.

Marine Isotopic Stages
Marine Isotope Stages (MIS), sometimes referred to
as Oxygen Isotope Stages (OIS), are related to
chronological alternating of cold and warm periods on
our planet, going back to at ~ 2.6 Ma.
MIS uses the balance of oxygen
isotopes in stacked fossil plankton
(foraminifera) deposits on the bottom
of the oceans to build an
environmental history of our planet.
The changing oxygen isotope
ratios hold information about the
presence of ice sheets, and thus
planetary climate changes, on our
earth's surface.

65.

the 16О atom
16О = 99,757%
+ +
+ +
+ +
+ +
neutrons = 8
protons = 8
____________
nucleons = 16
____________
electrons = 8
+ - protons
the 17О atom
17О = 0,038%
+ +
+ +
+ +
+ +
neutrons = 9
protons = 8
____________
nucleons = 17
____________
electrons = 8
- neutrons
the 18О atom
18О = 0.205%
+ +
+ +
+ +
+ +
neutrons = 10
protons = 8
____________
nucleons = 18
____________
electrons = 8
- electrons

66.

Marine Isotopic Stages
As a result of experiments that compared the real
temperature of foraminifera growth with the calculated
"isotopic temperatures", the following equation was
derived (Erez & Luz, 1983).
ToC = 17.0 – 4.52 (δ18Oc – δ18Ow) + 0.03 (δ18Oc –
– δ18Ow)2,
where
δ18Ос – О-isotope from carbonate-CO2 and
δ18Оw – О-isotope from СО2, which is in
equilibrium with water at 25оС.
δ18О = 18O/16O

67.

Marine Isotopic Stages

68.

Inclination
Foraminifers
Grain-size
Inclination
Фораминиферы
Гранулометрия
(Jakobsson et al., 2001)
Хребет Ломоносова
Foramenifers
Inclination
Grain-size
QUATERNARY SEDIMENTATION IN THE ARCTIC

69.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
Hydrocarbons were discoveried in Arctic:
- along the Arctic Alaskan
margins (Mackenzie Delta–
Prudhoe Bay),
- the Canadian Arctic
Islands (Sverdrup–
Ellesmere Basin), and
- on the Eurasian shelves
(southern Barents Sea,
western Siberia).
These discoveries demonstrate that favourable
conditions for hydrocarbon generation and entrapment
are widespread in the Arctic Ocean region
The primary source of these oil and gas accumulations is
thought to be source-rock units of Pz and Mz age.

70.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
In contrast, Tertiary oils in the Beaufort Mackenzie
basin off northwestern Canada appear to be derived
from organic-rich, middle-upper Eocene deposits
(Richards Sequence).

71.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
A new assessment of the hydrocarbon resources
along the Arctic Alaskan margin suggests that Eocene
and Miocene sequences have given rise to previously
unrecognized petroleum systems.
A potential source-rock unit might be the organic-rich,
lower Eocene section of the Canning Formation
(Mikkelsen Tongue) which has organic carbon contents
typically 1-2 wt% and max values up to 12.3 wt%.

72.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
Recent recovery of organicrich, lower-middle Eocene
sediments from the Lomonosov
Ridge by the IODP302
Expedition, coupled with
evidence from organic-rich
Eocene deposits on the New
Siberian Islands (Kos’ko and
Trufanov, 2002), has given rise
to speculations that widespread,
organic-rich, potential source
rocks might be present across
the entire Arctic Basin and its
margins (Durham, 2007).
Yellow asterisks = Azolla locations
These strata are characterised by the widespread occurrence
of large quantities of the freshwater fern Azolla deposited during
the onset of the middle Eocene (about 50 Ma).

73.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
Simulated variation in TOC content (wt%) and HI (mg HC/g TOC)
between 56.2 and 44.4 Ma along the Lomonosov Ridge transect

74.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
Modelled source-rock potential in the
Lomonosov Ridge borehole (IODP-302)
Source-rock potential classes based on HI and
TOC values (Peters, 1986)

75.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
Simulated source-rock potential in sediments deposited
between 56.2 and 44.4 Ma along the Lomonosov Ridge and
corresponding overburden thickness (in metres).
Potential is better in the Amundsen Basin direction.

76.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
1D thermal and burial history modeling for IODP-302 borehole (Mann et al., 2009).
Model shows that an additional 1000 m overburden and a constant heat flow of 100 mW
m2 are required to initiate HC generation.

77.

OIL&GAS POTENTIAL OF THE CENTRAL ARCTIC
Accumulated thickness of rocks having very good and good HC
source potential on the Lomonosov Ridge (max. 110 m) and in
the Amundsen Basin (up to 250 m) plotted against their
respective seismic profiles (Mann et al. 2009).

78.

CONCLUSION
1) Canadian Basin began to form in the Late Jurassic –
Early Cretaceous (~150-140 Ma) due to breaking off the
Chukotka–Arctic Alaska microplate from the Canadian
Arctic Archipelago.
2) The process of detachment and subsequent movement of
the Alpha-Mendeleev Ridge away from the Barents Sea
margin, accompanied by rift extension of the Makarov and
Podvodnikov basins, occurred in the interval of 110-60 Ma.
3) Mesozoic sediments in the Amerasian Basin represented
mainly by siliceous («diatom-bearing”) sediments.
4) Detachment of the Lomonosov Ridge from the Barents
Sea margin and formation of the Eurasian Basin began
~58 Ma (Late Paleocene).

79.

CONCLUSION
5) Two age models (“A” and “B”) may be used for the
characterization of ACEX sediment. Age model “A” includes
a 26 My-long hiatus (covering the Oligocene, Eocene and
Late Early Miocene). Model “B” includes a hiatus of less than
400 Ky. Model “B” seems more reliable from the standpoint
of plate tectonics. In favor of a short hiatus indicates the
absence of significant erosion of sediment, confirmed by a
detailed analysis of the dropstones and heavy minerals
distribution.
6) During the late Paleocene-early Eocene terrigenous shelf
sediments accumulated on the Lomonosov Ridge (and in the
Eurasian Basin): LU3 in the ACEX-well. Accumulation of biosiliceous sediments began in the Middle Eocene: LU2-1/6 in
the ACEX-well. For a long time the Arctic Ocean was an
isolated basin.

80.

CONCLUSION
7) In the Late Eocene (36.6 Ma) Fram Strait opened and
the isolation of the Arctic Ocean terminated. Pelagic
terrigenous sediments of lithological units 1/6 - 1/1
began to accumulate.
8) The first seasonal ices appeared in the central Arctic
in the Middle Eocene and the further evolution of the
Arctic basin was accompanied by a gradual cooling of
the climate.
9) The first pack ice in the central Arctic have appeared
in the Middle Miocene (about 13 Ma). From that
moment, trans-polar drift ice system began working.

81.

CONCLUSION
10) Sources of sedimentary material that is carried by
ice (icebergs) was fairly stable in geological history. For
the Eurasian basin this is a mainly "Siberian sources",
and for Amerasian basin - "Canadian.“ This indicates the
general (large-scale) stability of the basic systems of
modern ice drift (trans-Polar and the Beaufort gyre) in
the geological past.

82.

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