Phanerozoic Tectonic Evolution of the Chukotka-Arctic Alaska Block: Problems of the Rotational Model Boris A. Natal’in Istanbul Technical University
Components of the Chukotka- Arctic Alaska block Arctic Alaska superterrane Arctic Alaska superterrane Seward Terrane Seward Terrane York Mountains terrane York Mountains terrane Bennett-Barrovia block Chukotka fold belt Nutesyn arc The Bennett-Barrovia block continues to Alaska as the Hammond subterrane, York Mountains terrane, and Nixon Fork terrane AlaskaChukotka
Proposed Boundaries of Arctic Alaska- Chukotka Plate (dotted line)
Late Jurassic, 150 Ma Lawver et al km Kotelnyi Severnaya Zemlya Kotelnyi
Bol. Lyakhovsky 122±7 K-Ar Younger than late Jurassic 291±62 Sm-Nd Ma K-Ar
Gravity gradients Pushkarev et al., 1999
Geophysical data Franke et al. (2004): - Blagoveschensk basin is absent - the shelf of the East Siberian Sea is epicontinental platform Puskarev et al. (1999): - Low standing basement - Densities are characteristic for consolidated crust Puskarev et al., 1999 SN
Bennett-Barrovia block: Basement Granites 750 Ma Metamorphism Ma Granites 699 Ma Granites 705 Ma Orthogneiss 681 and 676 Ma Orthogneiss 650 Ma
Correlation with Taimyr Bennett-Barrovia pre-collision volcanics – 633±25 Ma syncollisional granites – (650?) Ma metamorphism – 630 Ma assimilated crust – Ga (Nelson et al., 1989) and 0,8-1.0 (Karl et al., 1989) Devonian granites – Ga Bennett-Barrovia pre-collision volcanics – 633±25 Ma syncollisional granites – (650?) Ma metamorphism – 630 Ma assimilated crust – Ga (Nelson et al., 1989) and 0,8-1.0 (Karl et al., 1989) Devonian granites – Ga Taimyr pre-collision volcanics – Ma syncollisional granites – 630 Ma metamorphism – assimilated crust – Ga
Correlation of Paleozoic sections
Barrovia (Sherwood, 1992)
Taimyr and Severnaya Zemlya (Russia) Thick pile of the upper Proterozoic-Cambrian flysch Evaporites in the Ordovician and Upper Silurian and Devonian Early Paleozoic fossils are different
Franklinian structures sandstone, tuffaceous sandstone, shale, conglomerate, lavas and dikes of basalt, andesite, and diabase Ordovician to Silurian oceanic and magmatic arc rock assemblages Margin of N. America Deformed Ordovician and Silurian slates
Pre-late Devonian subduction related magmatic arc at the eastern edge of BB gravity magnetic Herman and Zerwick, 1998
The late Silurian-early Devonian collision of the Bennett-Barrovia block
Devonian-early Carboniferous subduction zone along the southern margin of the Bennett-Barrovia block Ma euhedral zircons of Ma 381 Ma 375 ± 11 Ma 376 ± 37 Ma ε Nd is +0.2 and Ma Visean
Back arc basin of the Devonian arc ε Nd -7 Tanatap basin - deep water shale and fine grained turbidite - high-K andesitic tuffs with ε Nd -7 Alyarmaut - Calc-silicates, quartzite, mafic tuffs Alyarmaut - Calc-silicates, quartzite, mafic tuffs Belkovskyi-Nerpalakh Trough - Upper Devonian to Lower Carboniferous limestone, shale, sandstone, conglomerate, mafic dikes and sills Belkovskyi-Nerpalakh Trough - Upper Devonian to Lower Carboniferous limestone, shale, sandstone, conglomerate, mafic dikes and sills Brooks Range - Devonian extensional basin (the Beaucoup F.) Brooks Range - Devonian extensional basin (the Beaucoup F.)
Position of continents is after Lawver et al. (2002); 390 Ma
Carboniferous-Permian Wrangel Island - shallow marine Carboniferous limestones grading up into Permian slates Wrangel Island - shallow marine Carboniferous limestones grading up into Permian slates (~2100 m) - basin slopes to the south Chukotka - Lower Carboniferous conglomerates grading up into arkose sandstones, shale, and limestones (4500 m) - Permian rocks are unknown - Source area is expected in the south - Source area have to be rich in granites
Modified after Grantz et al. (1991) 4.5 km molasse orogeny Many km lithic turbidite mafic magmatism rifting km shale, chert, sandstone stable shelf
Carboniferous collision? Position of continents is after Lawver et al. (2002); 330 Ma
Opening of the South Anyui ocean Position of continents is after Lawver et al. (2002)