6 June 2016

Cleavage refraction in Konnarock Fm. rhythmites – a virtual sample

Posted by Callan Bentley

Here’s a visualization combination that leverages the advantages of the GIGAmacro system with the 3D ‘virtual sample’ perspective of the Sketchfab-hosted model: the same sample presented in both formats.

In this case, it’s a lovely example of cleavage refraction going from meta-clay-shale (now ‘slate’) through a graded bed of fine sand and silt.

Link GIGAmacro by Callan Bentley

Photoscan model by Marissa Dudek

The sample is of the Neoproterozoic Konnarock Formation‘s lower “rhythmite” unit (maybe varves??) near Mount Rogers, in Virginia’s Blue Ridge. The deformation overprints the primary sedimentary features, and is certainly related to Appalachian mountain building – probably the terminal Alleghanian phase.

Students: can you tell which of these renditions is right side up? Explain. How does the cleavage angle reinforce this deduction?