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50 NOTES ON COLI-HUAPI PROFILES. Pehuenche: The Salamanqueano is not exposed in any continuous section with the barranca + the Chubutiano occurs no nearer than the cliff east of the Laguna. The lowest beds exposed near the barranca belong to the Pehuenche. The lower part, poorly exposed, is chiefly of cross-bedded variegated sands + gravels where visible, as in the shore-cliff near Camp #1. At the foot of the cliff, the upper part of the Pehuenche, it consists chiefly of sombre variegated shales, soft plastic clay when wet. Some bone fragments occur in this, but not identifiable even as to class. The contact with the argiles fissilaires seems everywhere to be plane and parallel, although not very well exposed except to the east. It involves a brusque change in lithology, but often when it can be followed closely there is a transitional zone of alternating Arg. fis. + Pehuenche-type beds. The possibility of an unconformity is not excluded, however. Argiles Fissilaires: This problematic formation here is formed by beds from 100'-150' in thickness intercalated between the Pehuenche and the Notostylopense. The contact with the Pehuenche is fairly sharp and can be defined within a few feet if not exactly. Wherever the two are seen in true continuity, without intervening talus or soil, the bedding planes of the arg. fis. + the notost. appear to be absolutely parallel. The transition also is often gradual to such a point that the top of the arg. fis. is difficult to fix exactly. Thus hard silicified beds or lenses