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Centre for Geobiology

Crossing Geological Boundaries

09.07.2008 Today we drilled across a major break in the geological sequence known as an unconformity. This radical change in rock types from predominantly sedimentary rocks above the unconformity to igneous rocks beneath signifies a major change in earth environments and a missing period of geological time during which major climatic and perhaps tectonic changes occurred.

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We hope to be able to better date the rocks on either side of this break and use a range of chemical techniques to understand why the rocks change so drastically here and if these changes were local or world wide.

photo: shows a flame structure in a sedimentary rock from the Barberton Mnt Land. These are formed when the dark probably denser upper layer was deposited on the paler lower layer that was still fluid, causing it to "squirt upwards" creating the flame structure (pencil for scale). Photo credit Nicola McLoughlin