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| Titel |
Structural studies near Pevek, Russia: implications for formation of the East Siberian Shelf and Makarov Basin of the Arctic Ocean |
| VerfasserIn |
E. L. Miller, V. E. Verzhbitsky |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1868-4556
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| Digitales Dokument |
URL |
| Erschienen |
In: Geology, geophysics and tectonics of Northeastern Russia: a tribute to Leonid Parfenov ; Nr. 4 (2009-09-17), S.223-241 |
| Datensatznummer |
250001449
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| Publikation (Nr.) |
 copernicus.org/smsps-4-223-2009.pdf |
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| Zusammenfassung |
The Pevek region of Arctic Russia provides excellent beach cliff exposure of
sedimentary and igneous rocks that yield detailed information on the nature,
progression and timing of structural events in this region. Regional folding
and thrust faulting, with the development of a south-dipping axial plane
cleavage/foliation developed during N-S to NE-SW directed shortening and
formation of the Chukotka-Anyui fold belt. This deformation involves strata
as young as Valanginian (136–140 Ma, Gradstein et al., 2004). Fold-related
structures are cut by intermediate to silicic batholiths, plutons and dikes
of Cretaceous age. Reported K-Ar whole rock and mineral ages on the
granitoids range from 144 to 85 Ma, but to the south, more reliable U-Pb
zircon ages on compositionally similar plutons yield a much narrower age
range of ~120–105 Ma (Miller et al., this volume) and a pluton in
Pevek yields a U-Pb age on zircon of 108.1±1.1 Ma with evidence for
inheritance of slightly older 115 Ma zircons. Magmas were intruded during an
episode of E-W to ENE-WSW directed regional extension based on the consistent
N-S to NNW-SSE orientation of over 800 mapped dikes and quartz veins.
Analysis of small-offset faults and slickensides yield results compatible
with those inferred from the dikes. Younger tectonic activity across this
region is minor and the locus of magmatic activity moved southward towards
the Pacific margin as represented by the <90 Ma Okhotsk-Chukotsk
volcanic belt (OCVB). A lengthy period of uplift and erosion occurred after
emplacement of Cretaceous plutons and produced the peneplain beneath the
younger OCVB.
Based on our studies, we speculate that ~120–105 Ma magmatism, which
heralds a change in tectonic regime from compression to extension, could
represent one of the consequences of the inception of rifting in the
Amerasian Basin of the Arctic, forming the Makarov Basin north of the
Siberian shelf at this longitude. A synthesis of available seismic
reflection, gravity and magnetic data for the offshore Siberian Shelf reveals
a widespread, seismically mappable basement-sedimentary cover contact that
deepens northward towards the edge of the shelf with few other significant
basins. Various ages have been assigned to the oldest strata above the
unconformity, ranging from Cretaceous (Albian – 112–100 Ma) to Tertiary
(Paleocene–Eocene – ~60–50 Ma). The period of uplift and erosion
documented along the Arctic coast of Russia at this longitude could represent
the landward equivalent of the (yet undrilled) offshore basement-sedimentary
cover contact, thus overlying sedimentary sequences could be as old as early
Late Cretaceous. Although quite speculative, these conclusions suggest that
land-based geologic, structural, petrologic and geochronologic studies could
provide useful constraints to help resolve the plate tectonic history of the
Arctic Ocean. |
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