Tectonic structure and evolution of the Alpha

Tectonic structure and evolution of the Alpha-Mendeleev Fracture Zone Chernykh A.1,2, Glebovsky V.1., Korneva M.1, Astafurova E. 1, Redko A.G. 1 I.S. Gramberg VNIIOkeangeologia (VNIIO), St.-Petersburg, Russia 2 Saint Petersburg State University, Russia

e-mail: [email protected] 35th IGC Cape Town, Republic of South Africa 2016

Study Area Depth, m

Main structures:

Ellesmere I.

Eurasian Basin (EB)

North Pole

EB

Amerasia Basin LR

MB

CAM

AR

PB

MeB

MR

MR CaB ESM

Alpha Ridge (AR) Mendeleev Ridge (MR) Chukchi Borderland (CB) Canadian Basin (CaB) Makarov Basin (MB) Mendeleev Basin (MeB) Podvodnikov Basin (PB)

CB

Banks I.

East-Siberian continental margin (ESM) Canadian Arctic continental margin (CAM) Fig. Bathymetry of the Amerasia Basin (IBCAO v.3.0 (Jakobsson et al., 2012)

Alpha-Mendeleev Ridges Transition LR

Sotrudnichestva (Cooperation) Gap [Treshnikov et al., 1967]

AR

N

MR

Fig. Bathymetry of the AlphaMendeleev transitional zone (IBCAO v.3.0 (Jakobsson et al., 2012)  «The angular relationship between the Mendeleyev Ridge and the Alpha Cordillera appears to result from a southerly displacement of the cordillera crest along numerous an echelon transform faults» (Hall, 1970)

Research results overview  EGU Conference 2014  Chernykh A.A., Astafurova E.G., Korneva M.S., Egorova A.V., Redko A.G., Glebovsky V.Yu. Tectonic pattern of the Mendeleev Ridge and adjacent basins: results of joint analysis of potential fields and recent Russian seismic data // Geophysical Research Abstracts, Vol. 16, EGU2014-14872, 2014  Publication  Chernykh A. A., Astafurova E. G., Glebovsky V. Yu., Korneva M. S., Egorova A.V., Redko A. G. New data on the tectonics of the Mendeleev Ridge and adjacent geological structures // Doklady Earth Sciences, 2016, 470, 2, pp.  ICAM-7 Conference 2015  Chernykh A. A., Glebovsky V. Yu., Egorova A. V., Redko A. G., Sukhanov R. A. Tectonic structure and evolution of the Alpha-Mendeleev Fracture Zone // Abstracts of the International Conference on Arctic Margins VII, 2–5 June 2015, Trondheim, Norway.  IGC-2016

Bathymetry & Potential Fields

N

+ -

Bathymetry model IBCAO v.3.0 [Jakobsson et al., 2012]

• • •

Magnetic anomaly map [Glebovsky et al., 2012]

Free air anomaly map [Glebovsky et al., 2012]

Specific magnetic anomaly field -> HALIP –High Arctic Large Igneous Province Chaotic, irregular character of AMF [ex., Grantz et al., 2011] Actually - boundaries of geostructures, their internal peculiarities, tectonic elements - could be distinguished

Potential Fields Interpretation • Correlation between magnetic, gravity anomalies and relief of basement is existed • Horst/graben structures are clearly seen on seismic sections across and along the Mendeleev and Alpha Ridges Dg Calculated

Dg Observed

(DT)a Observed Alpha Ridge

upper crust

low crust

mantle

Fig. Gravitational model along MR. Upper part is based on MCS data from «Arktika-2012»

Mendeleev Ridge tectonic structure • Horst-graben structure • MR • South part – N-S orientation • North part – NW-SE orientation, rhomboid form

Thickness, km

Boundaries of geostructures

• AR • NE-SW orientation Faults

Strike-slip & oblique-slip faults

Grabens, half-grabens

Fig. The structural and tectonic scheme of MR and adjacent geostructures

Slip Faults & AMFZ • Strike-slip & oblique-slip faults: • found by offsets of anomalies and by rhomboid grabens joining in pull-apart basins; • are sinistral faults; • supported by multichannel seismic data (next slides); • point to existed transtensional conditions; • form broad Alpha-Mendeleev Fracture Zone (AMFZ).

Fig. Alpha-Mendeleev Fracture Zone (AMFZ) location between MR and AR

Thickness, km

Multichannel Seismic Data S

N

0

V.E. 1:3

S

0

5 km

Line 1201

Flower structure

25 km

N

Multichannel Seismic Data

• Results of Interpretation of reflection seismic data crossing Alpha-Mendeleev Fracture Zone (AMFZ) had supported it existence

Tectonic Structure of Study Region

Bathymetry, meters

• The draft tectonic scheme of Arctic Ocean is shown with other shear zones proposed

Fig. The draft tectonic scheme of whole study region over the map of bathymetry IBCAO 3.0 [Jakobsson et al., 2012]

ARCTIDA? •

Moving back the blocks of Mendeleev Ridge and Chukchi Borderland along AMFZ finally led to idea of initial unity of all blocks with present thick crust (>22 km) in Amerasia Basin (AR, MR, LR, CB, etc.)

•

They are seemed to be blocks of continental Arctida [Zonenshain, Natapov, 1987]

Makarov Basin

AR

Podvodnikov Basin

Mendeleev Basin

MR

Canadian Basin

CB

ES (De Long High)

Fig. Reconstruction of strike-slip motion of the Mendeleev Ridge and Chukchi Borderland along AMFZ back in time shown over map of consolidated crust thickness

North Chukchi Basin

Crust thickness, km less

10.4

12.0

13.7

15.4

17.1

18.8 20.5

22.2

23.9

25.5

27.2

28.9 30.6

32.3

34.0

35.7

more

Evolution ~155 Ma • Existence of ARCTIDA (Zonenshain, Natapov, 1987) • Beginning of Canada Basin (CB) opening

Arctic Canada

AR

MR

CB

CB – Chukchi Borderland; AR –Alpha Ridge; MR – Mendeleev Ridge

The Legend spreading continental rifting

Alas ka

shear zones HALIP carapace

Evolution ~130 Ma • HALIP emplacement (138-125 Ma by Dossing et al., 2012) • Phase 2 of Canada Basin opening (Grantz et al., 2011) • Beginning of disintegration of AR+MR+CB blocks

AR

MR

t-Sib

Arctic Canada

Eas erian

CB

-Chu kchi

CaB

f sh e l

CB – Chukchi Borderland; Cab - Canada Basin; AR –Alpha Ridge; MR – Mendeleev Ridge


shear zones Alaska

HALIP carapace

Evolution

lf she a r - Ka nts

AR

PB

Arctic Canada

e Bar

~110 Ma • Rifting/spreading in Mendeleev and Podvodnikov Basins • AMFZ functioning (125 -100 Ma, this study) • Rifting in Makarov Basin

MeB

East-Siberian-Chukchi shelf

MR

CaB

CB

Alaska

AMFZ – AlphaMendeleev Fracture Zone; CB – Chukchi Borderland; CaB - Canada Basin; AR –Alpha Ridge; MeB – Mendeleev Basin MR – Mendeleev Ridge PB – Podvodnikov Basin



Evolution ~90 Ma • End of rifting/spreading in Podvodnikov & Makarov Basins ara ts-K n e Bar

lf she MB

PB


Arctic Canada

AR

MeB MR

CaB

CB

CB – Chukchi Borderland CaB - Canada Basin AR –Alpha Ridge MB – Makarov Basin MeB – Mendeleev Basin MR – Mendeleev Ridge PB – Podvodnikov Basin



Alaska

Evolution Greenland

en Ba r

~70 Ma • Onset of rifting in the Barents-Kara shelf (Drachev et al., 2011)

lf she a r a ts-K LR MB AR


Arctic Canada

PB

MeB MR

CaB

CB

Alaska

CB – Chukchi Borderland CaB - Canada Basin AR –Alpha Ridge LR – Lomonosov Ridge MB – Makarov Basin MeB – Mendeleev Basin MR – Mendeleev Ridge PB – Podvodnikov Basin



Evolution Greenland

Present time • Spreading in Eurasian Basin

EB LR MB AR


Arctic Canada

PB

MeB MR

CaB

CB

Alaska

CB – Chukchi Borderland CaB - Canada Basin AR –Alpha Ridge LR – Lomonosov Ridge MB – Makarov Basin MeB – Mendeleev Basin MR – Mendeleev Ridge PB – Podvodnikov Basin



General Conclusions  AMFZ – is broad shear zone between Alpha and Mendeleev Ridges comprising system of sinistral strike-slip and oblique-slip faults formed in transtensional conditions  AMFZ – is key geological structure to reveal tectonic evolution of the Amerasia Basin  AMFZ was functioning while formation of the Mendeleev Basin due to extension which came from the opening Canada Basin (during Phase 2), in time period of ~125-100 Ma

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