Friday Field Foto #78: Sampling volcanic ashes
As most of my readers already know, I recently returned from another trip to southern Chile to look at the Cretaceous sedimentary rocks exposed in the Patagonian Andes (my 6th year in a row). This year was different in that the primary purpose of the trip was to convene an SEPM field conference with my colleagues and show others in our field these great rocks.
But, since it is such a long way to go, we added a couple days before and after the conference to do a bit of field work. A student at my alma mater completed her final (?) field season down there this year. She is a structural geologist working on the evolution of the basin in relation to the fold-thrust belt.
In the last couple of years an old road was improved significantly, which created numerous new roadcut outcrops. These new roadcuts reveal some incredible exposures of previously unexposed deep-marine sedimentary rocks. What the roadcuts also reveal are some volcanic ashes! In this week’s photo the prominent white stratum (also marked by hammer at right side) is one of these ashes.
This ash layer, along with several others, were sampled and their ages will be determined sometime this year as part of this student’s dissertation. This is very exciting because this basin needs some more age control badly.