16 November 2011
Vesicle-rich layering in Catoctin Formation
Posted by Callan Bentley
I saw this boulder lining a garden this past weekend down in Nellysford, Virginia, in the scenic valley of the Rockfish River draining the eastern slope of the Blue Ridge.
It’s a piece of the Neoproterozoic-aged Catoctin Formation, a series of lava flows and associated rocks that erupted on the breakup of the early supercontinent Rodinia and the subsequent opening of the Iapetus Ocean basin. The white “polka dots” are amygdules – volcanic degassing structures called vesicles that have been filled in with white-colored mineral deposits.
What struck me about this boulder was the distinctive amygdule-rich horizons, separated by amygdule-poor horizons. I guess these might reflect flow patterns in the ancient lava?
[…] Rodinia was breaking up to open the Iapetus Ocean basin. As the basaltic lava degassed, bubbles formed. Some of these bubbles popped, and released their payload of gases to the Neoproterozoic […]