Study Dates Great Unconformity Erosion to 2.1-1.6 Billion Years Ago, Not Snowball Earth
Updated
Updated · ZME Science · Aug 19
Study Dates Great Unconformity Erosion to 2.1-1.6 Billion Years Ago, Not Snowball Earth
2 articles · Updated · ZME Science · Aug 19
Summary
A new PNAS study says the Great Unconformity was mainly carved by tectonic upheaval during supercontinent cycles, with North China erosion peaking 2.1 billion to 1.6 billion years ago rather than during Snowball Earth 700 million years ago.
Five North China field sites and zircon dating methods traced when basement rocks cooled and rose, linking the strongest crustal exhumation to the assembly of the ancient supercontinent Columbia.
That timing undercuts the idea of a single global glacial scouring event: preserved Snowball Earth-age rocks in the eastern Grand Canyon and limited erosion on Namibia's Congo margin point to uneven regional histories.
The findings also weaken a long-running link between Snowball Earth erosion and the Cambrian explosion around 530 million years ago, suggesting several regional 'great unconformities' formed at different times for different reasons.