OREGON STATE UNIVERSITY

Stop 6: The Intracaldera Ignimbrite

Stop 6: The Intracaldera Ignimbrite

[21°42’56.30”S, 67°43’15.60”W]

The fifth goal of the season was quite simple in comparison to the previous days.  The idea was to become more familiar with the intra caldera facies of the Pastos Grandes Ignimbrite, looking for any variation in the unit with proximity to the scarp.  The results were quite boring, as the facies seems to be pretty unifom along the inner flanks of the caldera scarp. 

 

Pastos Grandes intracaldera facies

The well-indurated intracaldera Pastos Grandes Ignimbrite contains dense juveniles and fiamme (flattened glassy pumice).

 

western moat of Pastos Grandes

Looking West into Chile, across the western moat of the caldera which is completely filled with intracaldera Pastos Grandes ignimbrite.