A paleomagnetic investigation of rocks from the Ohio Range and the Dry Valleys, Transantarctic Mountains, Antarctica

Abstract

Two well-defined virtual geomagnetic poles (VGPs) for East Antarctica were obtained from the Middle Jurassic Ferrar Dolerite, sampled from a thick sill on Mt Schopf in the Ohio Range, and from a horizontal sheet intruding Paleozoic granitic rocks at Mt Cerberus in the Dry Valleys. The VGP from the sill at Mt Schopf lies at lat. 58°.0S, long. 129°.0W (dm=13°, dp=12°), and the VGP from Mt Cerberus lies at lat. 57°.8S, long. 135°.7W (dm=6°, dp=6°). Rocks from both localities have normal polarity magnetisations. These data, together with 15 other acceptable pole positions reported in the literature, define a Middle Jurassic paleomagnetic pole at 52°.7S, 139°.6W (α₉₅=4°.4), which is not significantly different from previously reported mean Middle Jurassic paleomagnetic poles from East Antarctica.

Paleomagnetic investigations in the Ohio Range of mafic inclusions in Ordovician granitic and sedimentary rocks of Devonian and Permian ages found that the rocks are magnetically unstable and are unreliable for determining a paleomagnetic pole.

Keywords:

• paleomagnetism
• Antarctica
• Ohio Range
• Dry Valleys
• Ferrar Dolerite
• Middle Jurassic