PHYSIOGRAPHIC AND GEOLOGIC DEVELOPMENT 243 



Fig. 161 — Types of deformation north 

 of Lambrama near Sotospampa. A 

 dark basaltic rock has invaded both 

 granite-gneiss and slate. Sills and dikes 

 occur in great numbers. The topographic 

 depression in the profile is the Lambrama 

 Valley. See the Lambrama Quadrangle. 



material. Nevertheless, it remains the dominating rock type over 

 the whole stretch of country from Huascatay to Huancarama. In 

 the northwestern part of the Abancay sheet its effect on the land- 

 scape may be observed in the 

 knife-like ridge extending from 

 west to east just above Hu- 

 ambo. Above Chuquibambilla 

 it again outcrops, resting upon 

 a thick resistant quartzite of 

 unknown age, Fig. 162. It is 

 strongly developed about 

 Huadquirca and Antabamba 

 and, still associated with a 

 quartzite floor, it finally disap- 

 pears under the lavas of the 



great volcanic field on the western border of the Andes. Figs. 141 

 and 142 show its relation to the invading granite batholiths and 

 Fig. 162 shows further structural features as developed about 

 Antabamba where the great volcanic field of the Maritime Cordil- 

 lera begins. 



Both the enormous thickness of the Carboniferous limestone 

 series and the absence of clastic members over great areas in the 



upper portion of the series 

 prove the widespread extent of 

 the Carboniferous seas and their 

 former occurrence in large in- 

 terlimestone tracts from which 

 they have since been eroded. 

 At Puquiura they extend far 

 over the schist, in fact almost 

 completely conceal it; at Pasaje 

 they formerly covered the mica- 

 schists extensively, their ero- 

 sion in both cases being conditioned by the pronounced uplift and 

 marginal deformation which accompanied the development of the 

 Vilcapampa batholith. 



G H 



Fig. 162 — Sketch sections at Anta- 

 bamba to show (a) deformed limestones 

 on the upper edge of the geologic map, 

 Fig. 163 A; and (b) the structural rela- 

 tions of limestone and quartzite. See 

 also Fig. 163. 



