Ordovician ocean plate stratigraphy and thrust duplexes of the Ballantrae Complex, SW Scotland

Implications for the pelagic deposition rate and forearc accretion in the closing Iapetus Ocean

Wataru Fujisaki, Hisashi Asanuma, Kazue Suzuki, Yusuke Sawaki, Shuhei Sakata, Takafumi Hirata, Shigenori Maruyama, Brian F. Windley

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The Ballantrae Complex (at Bennane Lea in SW Scotland) contains important ocean plate stratigraphy (basalt, chert, mudstone, sandstone) in an accretionary prism that is associated with a classic Ordovician ophiolite. We used the ocean plate stratigraphy to sub-divide the prism into 11 tectonic units. To determine the depositional age of bedded cherts, zircons were separated from 9 tuff beds from 6 different units. All the tuffs have early to middle Ordovician ages, even though their present positions are mutually distant. These ages are consistent with microfossil records of radiolaria and graptolites. The stratigraphic-structural relationships demonstrate that the ocean plate stratigraphy has been repeated by bedding-parallel thrusts; this is typical of a modern accretionary duplex. We calculated the sedimentation rate of Early to Middle Ordovician bedded cherts at Bennane Lea on the basis of U-Pb zircon ages obtained from several tuff beds; the data indicate that the depositional rate (0.6-3. m/myr) was as slow as that of Mesozoic-Cenozoic equivalents defined by radiolaria. The age spectra of detrital zircons from Ballantrae sandstones show prominent single peaks at ca. 467 and 478. Ma, and a lack of Precambrian zircons. Integration of our new zircon ages with published isotopic data and palaeo-geographic maps indicates that the sandstones were deposited near an intra-oceanic arc and far from any continent containing Precambrian rocks. The pelagic-to-clastic sediments at Bennane Lea were deposited in the closing Iapetus Ocean from ca. 477. Ma to ca. 464. Ma, when they were accreted with the intra-oceanic arc of Ballantrae.

Original languageEnglish
JournalTectonophysics
DOIs
Publication statusAccepted/In press - Nov 20 2014
Externally publishedYes

Fingerprint

Iapetus
Scotland
Iapetus Ocean
duplex
stratigraphy
closing
thrust
Ordovician
oceans
sandstones
accretion
zircon
ocean
prisms
beds
radiolaria
arcs
sandstone
tuff
Precambrian

Keywords

  • Ballantrae Complex
  • Deep-sea sediments
  • LA-ICP-MS
  • Ocean plate stratigraphy
  • Zircon U-Pb age

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Geophysics

Cite this

Ordovician ocean plate stratigraphy and thrust duplexes of the Ballantrae Complex, SW Scotland : Implications for the pelagic deposition rate and forearc accretion in the closing Iapetus Ocean. / Fujisaki, Wataru; Asanuma, Hisashi; Suzuki, Kazue; Sawaki, Yusuke; Sakata, Shuhei; Hirata, Takafumi; Maruyama, Shigenori; Windley, Brian F.

In: Tectonophysics, 20.11.2014.

Research output: Contribution to journalArticle

Fujisaki, Wataru ; Asanuma, Hisashi ; Suzuki, Kazue ; Sawaki, Yusuke ; Sakata, Shuhei ; Hirata, Takafumi ; Maruyama, Shigenori ; Windley, Brian F. / Ordovician ocean plate stratigraphy and thrust duplexes of the Ballantrae Complex, SW Scotland : Implications for the pelagic deposition rate and forearc accretion in the closing Iapetus Ocean. In: Tectonophysics. 2014.
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AU - Suzuki, Kazue

AU - Sawaki, Yusuke

AU - Sakata, Shuhei

AU - Hirata, Takafumi

AU - Maruyama, Shigenori

AU - Windley, Brian F.

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KW - Zircon U-Pb age

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