History of the Island of Cuba. 199 



ous, while the remaining thin partitions are indurated into 

 sharp edges of coarsely crystalline marble — a surface indura- 

 tion which I have also often noticed in the chalky Cretaceous 

 limestones of Texas. 



On the resisting summit points the rock is hardened and 

 worn into Karrenfelder, while the steeper bluffs are thickly 

 coated with tufaceous deposits. Great caverns abound in 

 these rocks in many parts of the island. So completely has 

 the work of solution and interstitial change gone on that the 

 original nature of the rock is nowhere well preserved. It 

 nowhere exhibits the enormous proportions or abundance of 

 coral remains so apparent in the reef rock, but on the other 

 hand there is an abundance of casts and moulds of molluscan 

 shells, and I seriously doubt if it was originally a reef rock, as 

 has been alleged. 



I do not think the occasional traces of coral proves reef 

 rock origin, for all corals are not reef building and the mol- 

 luscan remains are far more abundant than those of corals. 

 Neither can they be called chalks, although very foraminifer- 

 ous in places, for they are too coarsely crystalline, and lack 

 that fineness and uniformity of texture seen in the chalky 

 limestones which I have had considerable experience in study- 

 ing. In places at their basal contact they are certainly detrital, 

 showing at the reservoir south of Havana, where they are in 

 contact with the older series of clays and serpentines, a dis- 

 tinct conglomeritic structure, largely composed of shell frag- 

 ments and beach wash. Near Villa Clara they contain very 

 small fragments of igneous material derived from the older 

 rocks which they buried. The limestones also contain alterna- 

 tions of other material which is clear^ not of reef rock origin, 

 such as the great beds of fine, siliceous and argillaceous mate- 

 rial as noted at Matanzas and seen from thence east to Baracoa, 

 forming thick strata of yellow material, containing, at least at 

 Baracoa, Miocene mollnsca. These slightly arenaceous yellow 

 beds outcrop at Nuevitas, Gibara and many other places along 

 the coast, and are included between thicker strata of limestone, 

 and I think they are underlain by several hundred feet of the 

 latter material, and belong above the limestone capping Junki 

 and the Yumuri bluffs. These yellow beds underlie the Sebo- 

 ruco reef at Baracoa, and are capped by a thick stratum of old 

 limestone back of the city ; the harbor is largely formed by 

 their undermining; they are also well developed beneath the 

 old reef points of Mata Bay. 



A peculiar rock material in the old limestone series at Bara- 

 coa and not seen elsewhere is a hill of almost vertically strati- 

 fied siliceous material, which at first sight resembles gray 

 chalk, but has the light specific gravity of some of the diato- 



