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P 170 NOTES PROFILE DB A. The contact of the Patagonian and Terrestrial tuffs is approximately plane but discordant. The basal Patagoniano is a tuff similar to some of those below but pith marine fossils. The contact is almost always visible topographically. In some, not all places the upper foot or so of the tuff is much indurated & contains irregular cavities and also bore holes ? almost exactly similar to what is occurring today near Comodoro where the modern sea is eroding the sane tuffs in the strand zone. The base of the Patagoniano is somewhat higher, in absolute elevation, than at Cabeza Blanca. B The uppermost part of the terrestrial tuffs average about 20' in some places seems slightly different from the lower beds, yellowier, somewhat less massive, & with larger concretion. In other places it cannot be so distinguished. The contact is generally obscured. No identifiable fossils were found, although an exhaustive search was made. On the basis of this section alone, there would be no reason to separate this from the lower beds. It is not, however proven that it is not separate & equivalent to the fossiliferous Pyro- P171 therium beds of Cabeza Blanca. If this is not the case, such an equivalent is lacking. Below this are about 175' of concordant tuffs, for the most part very massive. There is some evidence of bedding & the three- fold division adopted in the section is generally visible, but the beds grade almost perfectly one into the other and seem to have been deposited continuously. Throughout this series fossils occur although in general extremely rare and very poor in preservation. Two zones, one about 20' to 30' and the other about 105'- 115' above the base, were found to be very locally somewhat richer in fossils both of the Notostylpos fauna by field determination. The basal contact is generally well defined by a marked lithologic change reflected in the topography but it appears to be perfectly concordant. This series in generally appears to be exactly similar to the tuffs underlying the Pyrotherium beds at Cabeza Blanca (distant less then 5