"No known ascent" is not the same as "no ascent" and I figured that the peaks in Biggar were probably already climbed:
Still, it was a good excuse. I hired a Chilean driver to check-out the access and I wrote Santiago for permission and ...
12 December 2000: First ascent of Sierra Nevada de Lagunas Bravas, 6155 meters. Ayers, Doherty, Morgan, and Brake.
We left the other peaks (and the Argentine summits of Sierra Nevada) for you-guys ... :-)