NOTES ON THE REGION ABOUT CAICARA, VENEZUELA 239 



ous veins and dikes cutting each other in all possible directions 

 traverses them. 



An extended survey of the shores of Isla de Caicara, opposite 

 the village of Caicara, showed that the bed rock of this island is a 

 medium-grained granite of comparatively firm texture, which is 

 drab colored in fresh breaks, but which weathers to a purplish 

 tint. This rock shows cleavage planes extending north and 

 south, and east and west. 



The cliffs exposed on the Caicara side of the stream by the 

 falling of the Orinoco during the dry season consist of medium to 

 fine-grained gneiss, whose laminations run either N.N.E.-S.S.W., 

 or E.N.E.-W.S.W. Quartz veins, varying in thickness from three 

 to five inches, cut the gneiss in a general N.W.-S.E. direction. 

 It was on the surface of one of these rocks, about 1 km. north of 

 Caicara, that the writer discovered what, considering the latitude, 

 would seem a very curious phenomenon. This consisted of three 

 grooves, about five inches long and one-eighth inch deep, which 

 run perfectly straight, one N. 8o° E., and the two other S. 8o° E. 

 They show a striking resemblance to glacial striae, but this does 

 not exclude the possibility that they may have been produced by 

 man, as in close proximity a series of the so-called " petroglyphics " 

 was found, the grooves of which, however, were considerably 

 deeper and wider. The surfaces of the rocks on which the grooves 

 were observed were considerably smoothed, as were the rocks of 

 the banks of the Orinoco, but this might be due to the effects of 

 the currents. 



The distribution of the granite and the gneiss in the hills 

 and ridges north of Cabruta and south and southeast of Caicara 

 also plainly reveals the prevalence of the gneiss over the granite, 

 for, with the exception of Cerro de Cabruta, north of the Orinoco, 

 and Cerro de los Spiritos, the lower portion of Cerro de Arinoza, 

 and possibly the whole of Pan de Azugar, all the cerros consist of 

 gneiss (see map, Fig. 1). 



The Cerro de Cabruta, rising abruptly at its southwestern 

 terminus from the waters of the Orinoco to a height of about 290 

 meters above sea-level, trends, for a distance of about 12 km., in 

 a N.E. direction, and gradually falls off toward the llano plateau. 



