19 June 2013

Dwyka Tillite in South Africa

Posted by Callan Bentley

My wonderfully named e-buddy Martin Bentley recently took a field trip to a quarry in South Africa (between Grahamstown and Fort Beaufort) where the Dwyka Formation is exposed:

This poorly sorted sedimentary rock (a ‘diamictite’) is usually interpreted as glacial deposits (lithified till, or ’tillite’).

Alfred Wegener cited these rocks and accompanying glacial striations (and similar ones in South Africa, India, Australia, and Antarctica) as evidence for the existence of Gondwana, the southern supercontinent of the late Paleozoic.

And Martin collected me some samples!

NOVA students will soon be examining these samples both in-hand and via the digital medium of the macro-GigaPan, to learn about glaciation, tillite, and the initial evidence put forward in support of continental drift.