A similar succession of strata was observed at Aplao, still farther up the Majes Valley, [174] . A greatly deformed and metamorphosed older series is unconformably overlaid by a great thickness of younger strata. The younger strata may be again divided into two series, a lower series consisting chiefly of red sandstones and an upper consisting of gray to yellow, and only locally red sands of finer texture and more uniform composition. The two are separated by an erosion surface and only the upper series is tilted regionally seaward with faint local deformation; the lower series is both folded and faulted with overthrusts aggregating several thousand feet of vertical and a half mile of horizontal displacement.
Fig. 174—The structural relations of the strata on the border of the Majes Valley at Aplao, looking west. Field sketch from opposite side of valley. Height of section about 3,000 feet; length about ten miles.
The above sections all lie on the eastern side of the Majes Valley. From the upper edge of the valley extensive views were gained of the strata on the opposite side, and two sections, though they were not examined at close range, are at least worth comparing with those already given. From the narrows below Cantas the structure appears as in Figs. 175-176, and shows a deforming movement succeeded by erosion in a lower series. The upper series of sedimentary rock has suffered but slight deformation. A still more highly deformed basal series occurs on the right of the section, presumably the older quartzites. At Huancarqui, opposite Aplao, an extensive view was gained of the western side of the valley, but the lower Tertiary seems not to be represented here, as the upper undeformed series rests unconformably upon a tilted series of quartzites and slates. Farther up the Cantas valley (an hour’s ride above Aplao) the Tertiary rests upon volcanic flows or older quartzites or the granite-gneiss exposed here and there along the valley floor.