On the origin of fore-arc basins: new evidence of formation by rifting from the Jurassic of Alexander Island, Antarctica

D I M Macdonald, P T Leat, P A Doubleday, S R A Kelly

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Abstract

The Middle Jurassic-Lower Cretaceous Fossil Bluff Group of Alexander Island, Antarctica represents the fill of a fore-are ba sin unconformably overlying an accretionary complex. Like most fore-are basins, this example had been considered to have a passive origin, as a topographic hollow between the are and the trench-slope break. Recent discoveries of igneous rock coeval with sedimentation have altered this view. Oxfordian-Kimmeridgian basaltic and rhyolitic sills and lava flows are found in a restricted area at the north of the basin, within a single formation. Chemically, most basalts are high-Nb types, which cannot have originated in a supra-subduction zone setting. Since the age of emplacement of these rocks coincides with a gap in the record of plutonism in the Antarctic Peninsula volcanic are, it is concluded that a late Jurassic pause in subduction led to active rifting to form the fore-are basin.

Original languageEnglish
Pages (from-to)186-193
Number of pages8
JournalTerra Nova
Volume11
Publication statusPublished - 1999

Keywords

  • GONDWANA BREAK-UP
  • ALKALINE MAGMAS
  • MAFIC DYKES
  • PENINSULA
  • EVOLUTION
  • BASALTS
  • BATHOLITH
  • MARGIN

Cite this

Macdonald, D. I. M., Leat, P. T., Doubleday, P. A., & Kelly, S. R. A. (1999). On the origin of fore-arc basins: new evidence of formation by rifting from the Jurassic of Alexander Island, Antarctica. Terra Nova, 11, 186-193.