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85 CERRO DEL HUMO NOTES ON PRECEDING PROFILES At this point there is an embay- ment in the west side of the lava- capped meseta of the Cerro del Humo. The sides of the embayment are formed by the barrancas, often obscured by slides, and the central part contains numerous more or less isolated hills and small mesetas, all of Tertiary tuff. The general dip is eastward at a low angle, but the beds are much disturbed, partly by original tectonic movements, partly by slumping, observable, seldom equalling 5�. Directly W., between the embayment and the road to Laguna de los Palacios, and continuing northward is a zone in which the beds are more sharply tilted, with an eastward dip of 50�-30�, and where the K-E transition is exposed. This, too, is affected by slumping + is also somewhat faulted, but is rather surely a fold of tectonic origin. CHUBUTIANO-PEHUENCHE: It is probable that all the beds shown in profile AA below the variegated silicified tuff (doubtless+ Argiles fissilaires) are Pehuenche. The apposition of a greenish sandstone and a dark, overlying clay suggest the SPECIMENS 87 CERRO DEL HUMO Profiles AA, AB, AC. (See also p. 41, other specimens). 276. 2 small lower jaws. Hard upper tuff. (Profile, p. 81). G.G.S. 12/9/30. 1 package. 29552 277. Skull + jaws. Profile p. 81. J.H. 12/9/30. 1 package. 29551 278. 2 large incisors and one jaw frag. Surface near #280. G.G.S. + J.H. 12/9/30. 1 pack. 279. Many isolated teeth, etc. "Upper quarries", profile p. 85. ? The level of the "lower quarries" is well defined, as marked. That of the "upper quarries" is doubtful due to the nature of the exposures. I believe they lie in the upper part of the hard tuffs of this profile, about 20'-25' above the "lower quarries." They are certainly not over 30' above the latter, + they are certainly not below them. G.G.S. 12/8/30. 1 pack. 29424-30 29486