268 BULLETIN OF THE 



The Sohoruco, or Elevated Reef Level. — The general extent and topo- 

 graphic character of the soboriico is explained on a previous page. It 

 forms the lowest bench immediately adjacent to the entire north coast 

 and along the Santiago front, and is topographically and geologically an 

 elevated coral reef. Synchronous with this level are the elevated playa 

 deposits in the harbors, and the elevated cienaga or mud deposit on the 

 south side of the island at Batabano. 



The Beach and Cliff Terraces. — Ou the east end of the island, the north 

 coast is marked by three distinct and abrupt cliffs and terraces cut out 

 of the steep slope of the old six-hundred-foot plain, or the Cuchilla level, 

 which forms the highland. Between Cape Maysi and Baracoa the coast 

 is practically inaccessible. The three terraces seen in this region ai'e so 

 clear and distinct that they are readily visible at one view, and their 

 continuity is clearly traceable for miles. They can be best understood 

 from the accompanying figure (Plate I. Fig. 6), and a description of the 

 coast adjacent to the mouth of the Yumuri of the east. Here the river 

 empties directly into the sea through a precipitous canon affording a 

 fine cross-section of the benches, so that their architecture and origin 

 can be seen. The coastal scarp consists of three narrow sub-level 

 benches, each surmounted by a vertical cliff. Bench No. 1 is the first 

 sub-level strip above the sea. This in general represents the level of 

 the elevated reef, which nearly everywhere forms the low-lying coastal 

 plain and breaks off at the sea in a surf wall some ten feet in length. 

 Its interior margin against the base of the first great clift" is forty feet 

 high, and it nowhere exceeds one hundred yards in width. Imme- 

 diately off the mouth of the Yumuri River, however, a gravel delta fan 

 spreads out in brackish water, a hundred yards or so on each side. 

 The present -submerged fringe reef does not grow immediately where 

 this delta fan is being deposited across the river mouth, but appears on 

 each side. If the present bottom, constituted as above, should be ele- 

 vated forty feet, it would produce a beach exactly similar to the elevated 

 one now seen ; that is, it would be composed of alluvial gi-avel imme- 

 diately where the rivar once emptied, and of coral limestone a hundred 

 yards or more on each side of it. 



This lowest terrace (Xo. 1), which is usually formed of elevated reef 

 rock, is composed of alluvial gravel immediately off the cut of the river, 

 and of elevated reef rock a quarter of a mile away seaward. This lowest 

 bench consists of several small levels, the uppermost of which is the 

 specially well defined alluvial gravel plain. 



This old beach abuts against a cliff (No. 2) about one hundred and 



