92 



J. W. SPENCER — GEOGRAPHICAL EVOLUTION OF CUBA. 



A B 



Figure 12. — Map of Yuvinri Valley. 



= position of section shown in figure 13. 



of the valley rises in the form of an amphitheater made by rain-washes. 

 Closing this valley and separatino- it from the deep Matanzas fiord there 

 is a range of hills about a mile across their base. This eastern end of 

 Yumuri valley is divided into tAVO lobes by an insular hill, shown on the 



map. The elevation 

 of this barrier ridge 

 is from 250 to 400 

 feet, and its longi- 

 tudinal section is 

 shown in broken 

 shading in figure 13, 

 while the form of 

 the valley is seen 

 bounded by solid 

 shading. The re- 

 markable feature of 

 the outlet is its 

 smallness, for it is a 

 canyon with verti- 

 cal walls, the ex- 

 treme height of which is 250 feet, and l)readth 300 feet, but the ridge 

 slopes upward gently on both sides, producing a shallow depression in 

 the barrier closing the valley (see figure 13). There is a second shallow 

 depression, indicated by 6, figure 13, the two depressions (a and b) cor- 

 responding to the two lobes of the valley. 



The contrast between the modern canyon, forming the only outlet of 

 the valley, and the magnitude and the age of the valley are most striking, 

 and at first would appear difficult 

 of explanation by any cause that 

 could be demonstrated, but in ex- 

 amining the canyon it was found 

 that the older Tertiary and late Pli- 

 ocene (Matanzas) formations were 

 involved in the most recent dis- 

 turbances, and that there had been a fault near the inner side of the 

 barrier separating the valley from the outer bay (see figure 4, i)age 76). 

 This fault furnishes an adequate explanation for the basin, and its verti- 

 cal elevation was from 250 to 400 feet, or the amount of elevation of the 

 hollows (a and 6, figure 13), which were the continuations of the two 

 lobes of Yumuri valley, as shoAvn in figure 12. 



The character of the valley being now known, the remaining question 

 was the date of the faulting. That it was long after the Pliocene times 



Figure 13. — Longitudinal Section of Ridge 

 closing Yumuri Valley. 



C=canj'pn; A and ^—former extensions 

 of valley. 



