128 



bulletin: museum of comparative zoology. 



tion of man's occupation of the area for a few centuries perhaps in 

 the past. 



Pissis (1875, p. 78-81) has described the distribution of the most 

 recent marine elevated deposits of Chile. Beginning on the north 

 in the plain which extends from the Bay of Antofogasta to that of 



>s-<=s.L. 



fO^SL. 



100 ioo loo "00 Sue too 700 soo »C9 loco hqo noo 



Fig. 35. — Rise to the north of the Recent uplifted marine deposits of Chile, 

 according to the data of Pissis (1875, p. 78-81). The dotted line show.s 

 apparent warped surface from Oaldera .southward. The line a-b gives 

 the mean tilt-rate from Mejilloncs southward. The line c-d is drawn at 

 the same tilt-rate to touch the elevated rock bench at Corral. 



Mejillones this plain, having there an altitude of forty meters, is 

 represented by correlated deposits at constantly lower levels oh the 

 south as far as the 38th parallel. In the vicinity of Caldcra the 

 deposits rise from twenty-five to thirty meters above sea-level. 

 About Valparaiso and San Antonio the level is maintained between 

 fifteen and twenty meters. The city of Concepcion is built on the 

 sands at the mouth of the Rio Bio Bio and finally at Levau the de- 

 posits rise scarcely two to three meters abo\e the sands of the beach. 

 Taking these data as given b\^ Pissis and plotting the upper limit 

 between Mejillones and Levau, the tilt-rate is shown by the graphical 

 construction in Fig. 35. According to these observations made by 

 Pissis as early as 1875 the coast from a point north of Valdivia shows 

 a rise at the rate of about 0.13 ft. per mile for about 1,100 English 

 statute miles. 



Valdi\ia and Corral lying to the south of this group of raised 

 deposits as noted above shows evidence of depression preceding the 

 last slight rise of the coast. Accepting Pissis's altitudes for the height 

 of the uplifted plain and assuming the above rate of tilting, the 

 abandoned sea-ca\'es south of Corral fall on a tilted plane about three 

 meters above that of the formation of sands and shells, and may 

 tentatively be regarded as at the sea-le\'el under which the sands were 

 laid down. 



