Debate continues about exactly when the “Mother of Mass Extinctions,” the Permo-Triassic event, actually occurred on land. A team of scientists published a paper in the journal Science last November in which they reported on a large suite of radiometric dates from ocean sediments that bracket the extinction event. But, to date, there are no well constrained dates for when the event occurred on land. The problem lies in the fact that volcanic ash beds, in which datable minerals occur, are unknown from the sediments deposited on the Late Permian land surface. With only three days left to this year’s field season, and following several grueling long days of 10-12 hours under the Karoo sun, and a hard night’s sleep (see Dan below with Lulu), we’ve hit pay dirt (no pun intended).
Earlier today we found a new volcanic ash horizon in the vicinity of Graaf Reinet that is close to the reported Permian-Triassic boundary. The photograph below may not look like much other than some crumbly rock of various olive-gray shades, but a close examination of the image will reveal a white interval that may look like snow. As an aside, it is hHard to believe, but true, that the mountain passes here often receive centimeters of snowfall during winter, and there are signs warning travelers of road closings….in Africa. The snow white layer in the picture is volcanic ash, which we collected and will have analyzed by our colleague, Sandra Kamo, University of Toronto, for datable minerals. This is one of the Rosetta stones for which we’ve been looking. To date, the Karoo has been unrelenting in giving up its secrets, with teams of scientists searching for such a horizon. It now may be the time for breaking the locks on the rocks.
Tomorrow we’ll return to the site and complete our measurements and sample collection. Then, it’s time to begin to check off our list to finalize our field studies before heading to Cape Town this coming weekend for a few days to enjoy South African culture and learn more about its post-Apartheid history.