Rocks of the Legoupil Formation in the Cape Legoupil area were folded about a N70E oriented axis. Later these rocks were affected only by brittle deformation which occurred in four stages: (1) jointing — set I, (2) dyking, (3) faulting and, (4) jointing — set II. Both, folding and subsequent brittle deformation, are hardly compatible with the Mesozoic-Cenozoic eastward subduction of the ancient Pacific ocean crust.
Three tectonic units occur in folded stratified volcanic sequence on Barton Peninsula. Fossil flora (Del Valle et al. 1984) occurs in the basal part of the upper unit which age is not younger than Paleocene. The rocks of the middle and lower units are older, possibly Mesozoie.